This document provides a review of size effect models and fracture mechanics as they relate to small scale structural modeling. It discusses the history of studying size effects dating back to Leonardo da Vinci and Galileo. More recent contributions include Griffith's work founding fracture mechanics in 1921 and Weibull completing the statistical size effect theory. The review explores deterministic size effect models based on fracture energy and nonlinear fracture mechanics that can better predict behavior of quasibrittle materials like concrete compared to linear elastic fracture mechanics. It presents Bazant's size effect law relating nominal stress to characteristic structure size and discusses its application and limitations for notched and unnotched specimens.
Plasticity, Theory of Plasticity ,Creep in concrete ,Creep, Stiffness ,Elasticity ,Plasticity ,Euler-Bernoulli beam equation, Buckling, Ductility VS Malleability, Ductile Materials, Brittle Materials ,Modulus of Elasticity, Plastic Strain, Tensile Strength, Yield Strength, Ultimate Strength, Solid mechanics or Mechanics of solids, Strength of Materials, Types of forces, Normal forces, Fatigue , Resilience, Unit of Resilience, Modulus of rigidity , Modulus of Resilience, Modulus of Toughness Poisson’s Ratio.
Understanding Permeability of Hydraulic Fracture Networks A Sandbox Analog Mo...Renee Heldman
1) The document discusses an analog sandbox model that was created to better understand how permeability is affected by hydraulic fracturing networks. Fine-grained silica powder was used to represent low-permeability shale and injected with a similar fluid to those used in fracking to create fracture networks.
2) Cross sections showed the development of fractures and permeability was quantified. Permeability increased from 2.7 x 10-9 cm2 originally to up to 0.032 cm2 after fracturing, demonstrating the significant impact fractures can have. Fracture development depended on confining pressure and fluid viscosity.
3) The document reviews scaling relationships for modeling fracturing and discusses using silica flour as an analogue for
Examples of Homogenization Techniques in the Material Modeling Under the Effe...Sardasht S. Weli
Explosions become a very attractive research area in the last decades.
This is due to the increase of accidental and intentional explosions.
Historical structure were not designed and built against the extreme loading events.
Homogenization Techniques were developed to assess the masonry response.
International Journal of Engineering Research and DevelopmentIJERD Editor
1) The study investigated the effect of aggregate size on the energy dissipation of plain concrete members subjected to static cyclic loading.
2) Testing found that smaller aggregate size (3/8") resulted in less energy dissipation compared to larger sizes (1/2", 3/4"), and gradually increasing loads led to less energy dissipation than constant loads.
3) Measurement of crack propagation using ultrasound found that larger aggregate sizes led to larger cracks under both constant and gradually increasing loads.
This document summarizes Griffith and Irwin fracture mechanics theories. [1] Griffith's theory explains brittle fracture and proposes that crack growth occurs when the potential energy released by fracturing exceeds the new surface energy. [2] Irwin modified Griffith's theory for ductile materials by including a term for the energy dissipated by plastic deformation near the crack tip. Irwin's theory partitions the energy into stored elastic energy driving fracture and dissipated energy resisting it. Crack growth occurs when the stored energy exceeds the dissipated energy.
A fracture mechanics based method for prediction ofSAJITH GEORGE
The document presents a fracture mechanics-based method for predicting cracking in circular and elliptical concrete rings undergoing restrained shrinkage. It describes an experimental program using different ring geometries and material tests to determine properties. A numerical model is developed using ANSYS to model the restrained shrinkage process and calculate stress intensity factors. The model uses a fictitious temperature field to simulate shrinkage and determines cracking age by comparing driving and resistance curves. It finds cracking occurs earlier in elliptical rings and the method accurately predicts experimental cracking ages.
FRACTURE MECHANICS OF NANO-SILICA PARTICLES IN REINFORCED EPOXIES Jordan Suls
This document summarizes a study that used finite element modeling to examine how different levels of particle dispersion (evenly dispersed, moderately clumped, and severely clumped) affect the fracture mechanics of nanosilica particle reinforced epoxies. Three models were created in Abaqus with the different dispersion levels and subjected to tensile loading. The results found that the evenly dispersed model had the highest fracture toughness, as indicated by its ability to withstand a greater force at similar displacements. This was because the clumped models developed large stress regions around the clumps that caused earlier debonding of the particle-matrix interfaces and faster crack propagation.
A Review of Masonry Buckling CharacteristicsIJERA Editor
Masonry load bearing wall subjected to vertical concentric and eccentric loading may collapse through instability. In this Paper the buckling behaviour of masonry load bearing wall of different slenderness ratio were investigated by many researcher has been reviewed via testing a series of scale masonry wall subjected to concentric and eccentric vertical loading. It is also observed that buckling behaviour is greatly influenced by the material properties of units, mortar and units-mortar interface. The influence of nonlinear behaviour of interface element, slenderness ratio and various end conditions have been investigated together with the effect of different end eccentricity of vertical load
Plasticity, Theory of Plasticity ,Creep in concrete ,Creep, Stiffness ,Elasticity ,Plasticity ,Euler-Bernoulli beam equation, Buckling, Ductility VS Malleability, Ductile Materials, Brittle Materials ,Modulus of Elasticity, Plastic Strain, Tensile Strength, Yield Strength, Ultimate Strength, Solid mechanics or Mechanics of solids, Strength of Materials, Types of forces, Normal forces, Fatigue , Resilience, Unit of Resilience, Modulus of rigidity , Modulus of Resilience, Modulus of Toughness Poisson’s Ratio.
Understanding Permeability of Hydraulic Fracture Networks A Sandbox Analog Mo...Renee Heldman
1) The document discusses an analog sandbox model that was created to better understand how permeability is affected by hydraulic fracturing networks. Fine-grained silica powder was used to represent low-permeability shale and injected with a similar fluid to those used in fracking to create fracture networks.
2) Cross sections showed the development of fractures and permeability was quantified. Permeability increased from 2.7 x 10-9 cm2 originally to up to 0.032 cm2 after fracturing, demonstrating the significant impact fractures can have. Fracture development depended on confining pressure and fluid viscosity.
3) The document reviews scaling relationships for modeling fracturing and discusses using silica flour as an analogue for
Examples of Homogenization Techniques in the Material Modeling Under the Effe...Sardasht S. Weli
Explosions become a very attractive research area in the last decades.
This is due to the increase of accidental and intentional explosions.
Historical structure were not designed and built against the extreme loading events.
Homogenization Techniques were developed to assess the masonry response.
International Journal of Engineering Research and DevelopmentIJERD Editor
1) The study investigated the effect of aggregate size on the energy dissipation of plain concrete members subjected to static cyclic loading.
2) Testing found that smaller aggregate size (3/8") resulted in less energy dissipation compared to larger sizes (1/2", 3/4"), and gradually increasing loads led to less energy dissipation than constant loads.
3) Measurement of crack propagation using ultrasound found that larger aggregate sizes led to larger cracks under both constant and gradually increasing loads.
This document summarizes Griffith and Irwin fracture mechanics theories. [1] Griffith's theory explains brittle fracture and proposes that crack growth occurs when the potential energy released by fracturing exceeds the new surface energy. [2] Irwin modified Griffith's theory for ductile materials by including a term for the energy dissipated by plastic deformation near the crack tip. Irwin's theory partitions the energy into stored elastic energy driving fracture and dissipated energy resisting it. Crack growth occurs when the stored energy exceeds the dissipated energy.
A fracture mechanics based method for prediction ofSAJITH GEORGE
The document presents a fracture mechanics-based method for predicting cracking in circular and elliptical concrete rings undergoing restrained shrinkage. It describes an experimental program using different ring geometries and material tests to determine properties. A numerical model is developed using ANSYS to model the restrained shrinkage process and calculate stress intensity factors. The model uses a fictitious temperature field to simulate shrinkage and determines cracking age by comparing driving and resistance curves. It finds cracking occurs earlier in elliptical rings and the method accurately predicts experimental cracking ages.
FRACTURE MECHANICS OF NANO-SILICA PARTICLES IN REINFORCED EPOXIES Jordan Suls
This document summarizes a study that used finite element modeling to examine how different levels of particle dispersion (evenly dispersed, moderately clumped, and severely clumped) affect the fracture mechanics of nanosilica particle reinforced epoxies. Three models were created in Abaqus with the different dispersion levels and subjected to tensile loading. The results found that the evenly dispersed model had the highest fracture toughness, as indicated by its ability to withstand a greater force at similar displacements. This was because the clumped models developed large stress regions around the clumps that caused earlier debonding of the particle-matrix interfaces and faster crack propagation.
A Review of Masonry Buckling CharacteristicsIJERA Editor
Masonry load bearing wall subjected to vertical concentric and eccentric loading may collapse through instability. In this Paper the buckling behaviour of masonry load bearing wall of different slenderness ratio were investigated by many researcher has been reviewed via testing a series of scale masonry wall subjected to concentric and eccentric vertical loading. It is also observed that buckling behaviour is greatly influenced by the material properties of units, mortar and units-mortar interface. The influence of nonlinear behaviour of interface element, slenderness ratio and various end conditions have been investigated together with the effect of different end eccentricity of vertical load
Numerical modeling of uneven thermoplastic polymers behaviour using experimen...Marcos Bianchi (Msc_Mba)
This document discusses numerical modeling of the behavior of uneven thermoplastic polymers using experimental stress-strain data and pressure dependent yield criteria to improve design practices. It presents the following:
1) Four polymers (PA-66, PA-6, PP, HDPE) were tested under tension and compression to determine their unevenness levels. PA-6 and PP showed significant unevenness, with compressive yield strengths 25-70% higher than tensile strengths.
2) Pressure dependent yield criteria that account for unevenness, such as conical and parabolic modified von Mises models, were reviewed. These criteria incorporate the effect of hydrostatic pressure on yield strength.
3) Experimental stress-strain data was
Peculiarities of irrecoverable straining in stress-drop testIJERA Editor
The paper concerns with analytical description of the phenomena observed in stress drop tests, namely, negative increment in plastic and creep deformation due to the sudden decrease in the acting stresses while the net stress remains positive. The model is developed in terms of the synthetic theory of irrecoverable deformation which has been generalized by introducing interplay between the deformation properties of material in the direction of acting load and opposite to it.
This document discusses the use of cohesive zone modeling to simulate fatigue crack growth and retardation. Cohesive zone models define cohesive stresses around a crack tip that are related to crack opening width. Crack propagation occurs when cohesive stresses reach a failure value. The models can account for material properties through a cohesive law. Finite element implementations use cohesive elements located at crack fronts. The models can simulate crack closure effects, wedge effects, and predict crack growth under various loading conditions like overloads through an unloading-reloading hysteresis. Cohesive theory provides a unified way to model long cracks under constant loading as well as short cracks and overloads.
Framework for assessment of shear strength parameters ofIAEME Publication
This document discusses a framework for assessing the shear strength parameters of residual tropical soils. It begins by providing background on shear strength and how it is typically measured through laboratory tests like direct shear tests and triaxial tests. However, these tests have limitations in simulating field conditions. The objective of the paper is then presented - to develop a phenomenological model to predict shear strength parameters from index properties that are easier to measure, like liquid limit and maximum dry density. This could provide a way to rapidly estimate shear strength when traditional testing methods are not available or feasible. The paper reviews previous studies on correlating index properties with shear strength and predicting unsaturated soil strength. It then discusses soil state and volumetric strain, and defines bulk modulus as
This document presents a study on using damage delocalization to model localization phenomena in the Bammann-Chiesa-Johnson (BCJ) constitutive model for metals. The study shows that modifying the BCJ model to include a nonlocal damage evolution equation, as proposed by Pijaudier-Cabot and Bazant, prevents unlimited localization of strain and damage. Specifically, it is shown that no discontinuities in the velocity gradient occur and dissipation energy is continuously distributed rather than localized into vanishing bands. Finally, finite element simulations of shear banding in a plate under tension illustrate the effects of imperfections and size on strain and damage localization within the nonlocal BCJ model framework.
This document summarizes a research paper that develops a modified grain contact theory to better model the pressure-dependent elastic properties of uncemented sediments. The Hertz-Mindlin theory typically overpredicts shear modulus values compared to laboratory measurements and does not capture the observed increasing ratio of bulk to shear modulus with decreasing effective pressure. The authors introduce two new pressure-dependent calibration parameters to account for grain relaxation effects and porosity changes not included in existing theories. Their modified model provides an improved fit to laboratory data and can predict elastic properties over a wider range of effective pressures.
Shear Strength Prediction of Reinforced Concrete Shear Wall Using ANN, GMDH-N...Pouyan Fakharian
To provide lateral resistance in structures as well as buildings, there are some types of structural systems such as shear walls. The utilization of lateral loads occurs on a plate on the wall's vertical dimension. Conventionally, these sorts of loads are transferred to the wall collectors. There is a significant resistance between concrete shear walls and lateral seismic loading. To guarantee the building's seismic security, the shear strength of the walls has to be prognosticated by using models. This paper aims to predict shear strength by using Artificial Neural Network (ANN), Neural Network-Based Group Method of Data Handling (GMDH-NN), and Gene Expression Programming (GEP). The concrete's compressive strength, the yield strength of transverse reinforcement, the yield strength of vertical reinforcement, the axial load, the aspect ratio of the dimensions, the wall length, the thickness of the reinforced concrete shear wall, the transverse reinforcement ratio, and the vertical reinforcement ratio are the input parameters for the neural network model. And the shear strength of the reinforced concrete shear wall is considered as the target parameter of the ANN model. The results validate the capability of the models predicted by ANN, GMDH-NN, and GEP, which are suitable for use as a tool for predicting the shear strength of concrete shear walls with high accuracy.
Improving the Properties of Self-compacted Concrete with Using Combined Silic...Pouyan Fakharian
The viscosity is the main property of self- compacted concrete (SCC) and using of pozzolan material such as metakaolin (MK) and Silica fume (SF) can help to achieve that goal. The effect of simultaneous substitution of MK and SF instead of cement on the rheological and mechanical properties of self-compacted concrete was experimentally investigated in this paper. Seventeen mix designs were cast with a substitution weight percentage (5, 10, 15, 20 %) in water to adhesive material ratio equal 0.32. All mixes were examined by compressive, tensile strengths and water absorption tests with an appropriate fluidity, without having signs of segregation or instability. The test results were indicated that the SCC mixes containing MK and SF had higher compressive and tensile strengths in comparison with no-pozzolan concrete. The comparison of linear multiple regression techniques (LMRT) and nonlinear multiple regression technique outputs with experimental results showed an appropriate similarity.
The present investigation deals with the static analysis of adhesively bonded inner tapered double lap joint in laminated FRP composites subjected to transverse loading using three-dimensional theory of elasticity based finite element method. Many researchers studied the influences of various parameters on the failure behaviour on the composites. In those studies, the typical bonding parameters are surface conditions, fillet, bond line thickness, and environmental conditions. In the present study the stresses and deformation characteristics of adhesively bonded inner tapered double lap joint made of generally and especially orthotropic laminates (FRP) subjected to transverse loading for the three different adhesive angles, three different adhesive thicknesses with different fibre angle orientations, i.e. the adhesive angles from 350 to 450 increased in steps of 50. The variation in stresses and deflection are studied when the fibre angle orientation is varied from 00 to 900 in steps of 150. The adhesive thickness varies from 0.05 to 0.15 insteps of 0.05mm. In all the above cases stresses and displacements at various locations are evaluated for the static boundary conditions
Predicting Resilient Modulus of Clayey Subgrade Soils by Means of Cone Penetr...Pouyan Fakharian
Resilient modulus (Mr) of subgrade soils is considered as one of the most important factors for designing flexible pavements using empirical methods as well as mechanistic-empirical methods. The resilient modulus is commonly measured by a dynamic triaxial loading test, which is complex and expensive. In this research, back-propagation artificial neural network method has been employed to model the resilient modulus of clayey subgrade soils based on the results of the cone penetration test. The prediction of the resilient modulus of clayey subgrade soil can be possible through the developed neural network based on the parameters of the cone tip resistance (qc), sleeve friction (fs), moisture content (w), and dry density (γd). The results of the present study show that the coefficients of determination (R2) for training and testing sets are 0.9837 and 0.9757, respectively. According to the sensitivity analysis results, the moisture content is the least important parameter to predict the resilient modulus of clayey subgrade soils, while the importance of other parameters is almost the same. In this study, the effect of different parameters on the resilient modulus of clayey subgrade soil was evaluated using parametric analysis and it was found that with increasing the cone tip resistance (qc), the sleeve friction (fs) and the dry density (γd) and also with decreasing the moisture content (w) of soils, the resilient modulus of clayey subgrade soils increases.
This document provides an overview of fracture mechanics. It discusses brittle and ductile fracture, the three modes of failure, energy release rate and crack resistance parameters like the J-integral and stress intensity factor. It also covers crack growth, applications of fracture mechanics like designing and material selection, and explains concepts such as the critical stress intensity factor and T-stress in less than three sentences.
This document summarizes a study on developing a fracture mechanics model to predict the insertion force of needles cutting through tissue. Experimental tests were conducted to determine the fracture toughness, shear modulus, frictional force, and crack length for different size needles inserted at various speeds into porcine skin. A force model was developed incorporating these parameters and validated against experimental force measurements, with errors less than 0.2 N. The model accurately predicts insertion forces and shows that 61% of the force comes from creating a crack in the tissue, while 21% is from friction and 18% from spreading the tissue. Increasing insertion speed was found to not reduce force for porcine skin.
Literature Review of Experimental Study on Load Bearing Masonry WallIOSRJMCE
Masonry load bearing wall subjected to vertical concentric and eccentric loading may collapse through instability. In this Paper the buckling behavior of masonry load bearing wall of different slenderness ratio were investigated by many researcher has been reviewed via testing a series of scale masonry wall subjected to concentric and eccentric vertical loading. The influence of nonlinear behavior of interface element, slenderness ratio and various end conditions have been investigated together with the effect of different end eccentricity of vertical load.
The document summarizes a study on heterogeneous deformation and dislocation dynamics in compressed copper micropillars using multi-scale discrete dislocation plasticity modeling. The model couples 3D finite element analysis to calculate stress distributions and image stresses with 3D discrete dislocation dynamics. It captures size effects, hardening behavior, and the influence of boundary conditions. Results show hardening is due to dislocation entanglement and stagnation, with stress concentrations affecting heterogeneous deformation.
STRUCTURAL RELIABILITY ASSESSMENT WITH STOCHASTIC PARAMETERSP singh
The performance of a structure [23] is assessed by its safety [1], serviceability [1] and economy [1]. Since we do not know the exact details of loads [4] acting on a structure at any time, there is always some uncertainty about the total loads on structure. Thus random variables (means stochastic variable) of loads and other parameters are the main criteria of design variables [18]. They vary with space and time. The input variables is never certain and complete. The safety factor provided in the existing codes and standers primarily based on practice, judgment and experience, may not be adequate and economical. Using the techniques presented earlier, we can design or analyze individual members in the contest of structural reliability [2][3][22][24]. However we are not examined how the system performs [23] or how to calculate the reliability of the structure as a whole.
Soil sheet pile interaction part i a review of theories and design methodsIAEME Publication
This document summarizes theories and modeling methods for studying the interaction between soil and sheet pile walls. It discusses the complex nonlinear behavior of soil-sheet pile interaction and reviews various modeling approaches used to analyze it, including the Mohr-Coulomb and cap models. It also reviews conventional design theories for sheet piles, such as the Coulomb and Rankine theories. The document emphasizes the importance of numerical analysis tools like the finite element method in accurately modeling the interaction between soil and sheet piles.
A new proposed approach for moment capacity estimation of ferrocement members...Pouyan Fakharian
Ferrocement composites are widely used as a novel method for many different structural purposes recently. The uniform distribution and the high surface area-to-volume ratio of the reinforcement of such composites would improve the crack-arresting mechanism. Given these properties, ferrocement is an ideal option as a replacement for some traditional structures methods. In members with axially loaded reinforced concrete ferrocement composite, it would be the best alternative to use ferrocement members. Lack of sufficient research in this approach is the cause of not well defining this field for RC structures. This study has aimed to evaluate the moment capacity of ferrocement members using the GMDH method. Mechanical and geometrical parameters including the width of specimens, total depth specimens, compressive strength of ferrocement, ultimate strength of wire mesh and volume fraction of wire mesh are considered as inputs to predict the moment capacity of ferrocement members. For evaluating this model, mean absolute error (MAE), root mean absolute error (RMAE), normalized root mean square error (NRMSE) and mean absolute percentage error (MAPE) were carried out. The results conducted that the GMDH model is significantly better than some previous models and comparable to some other methods. Moreover, a new formulation for moment capacity of ferrocement members based on GMDH approach is presented. Finally, Sensitivity analysis is operated to understand the influence of each input parameters on moment capacity of ferrocement members.
Some Studies on Mode-II Fracture of Light Weight Blended Aggregate ConcreteIOSR Journals
Blended aggregate in concrete and arriving at the structural properties of blended aggregate
concrete is a thrust area. Pumice is very light and porous igneous rock that is formed during volcanic
eruptions.Cinder is a waste material obtained from steel manufacturing units. Shear strength is a property of
major significance for wide range of civil engineering materials and structures. Shear and punching shear
failures particularly in deep beams, in corbels and in concrete flat slabs are considered to be more critical and
catastrophic than other types of failures. This area has received greater attention in recent years. For
investigating shear type of failures, from the literature it is found that double central notched (DCN) specimen
geometry proposed by Prakash Desai and V.Bhaskar Desai is supposed the best suited geometry. In this present
experimental investigation an attempt is made to study the Mode-II fracture property of light weight blended
aggregate cement concrete combining both the pumice and cinder in different proportions, and making use of
DCN test specimen geometry . By blending the pumice and cinder in different percentages of 0, 25, 50, 75 and
100 by volumeof concrete, a blended light weight aggregate concrete is prepared. By using this the property
such as in plane shear strength is studied. Finally an analysis is carried out regarding Mode-II fracture
properties of blended concrete. It is concluded that the Ultimate load in Mode-II is found to decrease
continuously with the percentage increase in Pumice aggregate content. It is also observed that the ultimate
stress in Mode II is found to increase continuously with percentage increase in cinder aggregate content.
This document summarizes a study that investigated the compressive behavior of rigid polyvinyl chloride (PVC) foam at strain rates up to 200 s-1. Tests were conducted on PVC foam samples with densities ranging from 45 to 200 kg/m3 in directions parallel and perpendicular to the foam's rise direction. Both quasi-static and dynamic compression tests were performed using a customized drop tower device. The results showed that strain rate effects were observed at higher densities when loading in the foam rise direction, with increased compressive strength and plateau stress at higher strain rates. However, no significant strain rate effect was observed when loading perpendicular to the foam rise direction. Scanning electron microscopy analysis indicated that plastic hinges were the primary deformation
The document summarizes a study of test data on the compressive strength of masonry walls made of hollow clay units. It finds that the geometrical properties of the units, such as the ratio of bearing area to gross area (b), have an important effect on wall strength beyond just the compressive strength of the units. For end-constructed walls, the study derived an empirical equation (Equation 4) that expresses wall strength M as a function of the mortar strength m, unit strength u, and the b ratio. This simple equation was found to reasonably fit the available test data.
The document summarizes a neighbor assisted distributed self-healing protocol (NDSP) for compromised node recovery in wireless sensor networks. The NDSP protocol allows a compromised sensor node to continuously and collectively recover from a compromised stage to a normal stage with the help of its neighbor nodes. The protocol detects compromised nodes and then replaces their seed values, which are used to generate encryption keys, with the seed values from neighboring healthy nodes in order to recover the compromised nodes and maintain data secrecy across the network. Simulation results showed that the presented NDSP scheme is effective and efficient at recovering compromised sensor nodes.
1) The document summarizes a study that evaluated non-clinical HIV/AIDS activities in Lagos State, Nigeria through surveys of secondary school and university students.
2) The study found gaps in HIV/AIDS awareness related to behavioral challenges, understanding of sexually transmitted infections, lack of transmission awareness, condom use, and fear of HIV/AIDS stigma.
3) To address these gaps, the study proposed a validated knowledge management framework to enhance HIV/AIDS information sharing and awareness of transmission and prevention factors in Lagos State.
Numerical modeling of uneven thermoplastic polymers behaviour using experimen...Marcos Bianchi (Msc_Mba)
This document discusses numerical modeling of the behavior of uneven thermoplastic polymers using experimental stress-strain data and pressure dependent yield criteria to improve design practices. It presents the following:
1) Four polymers (PA-66, PA-6, PP, HDPE) were tested under tension and compression to determine their unevenness levels. PA-6 and PP showed significant unevenness, with compressive yield strengths 25-70% higher than tensile strengths.
2) Pressure dependent yield criteria that account for unevenness, such as conical and parabolic modified von Mises models, were reviewed. These criteria incorporate the effect of hydrostatic pressure on yield strength.
3) Experimental stress-strain data was
Peculiarities of irrecoverable straining in stress-drop testIJERA Editor
The paper concerns with analytical description of the phenomena observed in stress drop tests, namely, negative increment in plastic and creep deformation due to the sudden decrease in the acting stresses while the net stress remains positive. The model is developed in terms of the synthetic theory of irrecoverable deformation which has been generalized by introducing interplay between the deformation properties of material in the direction of acting load and opposite to it.
This document discusses the use of cohesive zone modeling to simulate fatigue crack growth and retardation. Cohesive zone models define cohesive stresses around a crack tip that are related to crack opening width. Crack propagation occurs when cohesive stresses reach a failure value. The models can account for material properties through a cohesive law. Finite element implementations use cohesive elements located at crack fronts. The models can simulate crack closure effects, wedge effects, and predict crack growth under various loading conditions like overloads through an unloading-reloading hysteresis. Cohesive theory provides a unified way to model long cracks under constant loading as well as short cracks and overloads.
Framework for assessment of shear strength parameters ofIAEME Publication
This document discusses a framework for assessing the shear strength parameters of residual tropical soils. It begins by providing background on shear strength and how it is typically measured through laboratory tests like direct shear tests and triaxial tests. However, these tests have limitations in simulating field conditions. The objective of the paper is then presented - to develop a phenomenological model to predict shear strength parameters from index properties that are easier to measure, like liquid limit and maximum dry density. This could provide a way to rapidly estimate shear strength when traditional testing methods are not available or feasible. The paper reviews previous studies on correlating index properties with shear strength and predicting unsaturated soil strength. It then discusses soil state and volumetric strain, and defines bulk modulus as
This document presents a study on using damage delocalization to model localization phenomena in the Bammann-Chiesa-Johnson (BCJ) constitutive model for metals. The study shows that modifying the BCJ model to include a nonlocal damage evolution equation, as proposed by Pijaudier-Cabot and Bazant, prevents unlimited localization of strain and damage. Specifically, it is shown that no discontinuities in the velocity gradient occur and dissipation energy is continuously distributed rather than localized into vanishing bands. Finally, finite element simulations of shear banding in a plate under tension illustrate the effects of imperfections and size on strain and damage localization within the nonlocal BCJ model framework.
This document summarizes a research paper that develops a modified grain contact theory to better model the pressure-dependent elastic properties of uncemented sediments. The Hertz-Mindlin theory typically overpredicts shear modulus values compared to laboratory measurements and does not capture the observed increasing ratio of bulk to shear modulus with decreasing effective pressure. The authors introduce two new pressure-dependent calibration parameters to account for grain relaxation effects and porosity changes not included in existing theories. Their modified model provides an improved fit to laboratory data and can predict elastic properties over a wider range of effective pressures.
Shear Strength Prediction of Reinforced Concrete Shear Wall Using ANN, GMDH-N...Pouyan Fakharian
To provide lateral resistance in structures as well as buildings, there are some types of structural systems such as shear walls. The utilization of lateral loads occurs on a plate on the wall's vertical dimension. Conventionally, these sorts of loads are transferred to the wall collectors. There is a significant resistance between concrete shear walls and lateral seismic loading. To guarantee the building's seismic security, the shear strength of the walls has to be prognosticated by using models. This paper aims to predict shear strength by using Artificial Neural Network (ANN), Neural Network-Based Group Method of Data Handling (GMDH-NN), and Gene Expression Programming (GEP). The concrete's compressive strength, the yield strength of transverse reinforcement, the yield strength of vertical reinforcement, the axial load, the aspect ratio of the dimensions, the wall length, the thickness of the reinforced concrete shear wall, the transverse reinforcement ratio, and the vertical reinforcement ratio are the input parameters for the neural network model. And the shear strength of the reinforced concrete shear wall is considered as the target parameter of the ANN model. The results validate the capability of the models predicted by ANN, GMDH-NN, and GEP, which are suitable for use as a tool for predicting the shear strength of concrete shear walls with high accuracy.
Improving the Properties of Self-compacted Concrete with Using Combined Silic...Pouyan Fakharian
The viscosity is the main property of self- compacted concrete (SCC) and using of pozzolan material such as metakaolin (MK) and Silica fume (SF) can help to achieve that goal. The effect of simultaneous substitution of MK and SF instead of cement on the rheological and mechanical properties of self-compacted concrete was experimentally investigated in this paper. Seventeen mix designs were cast with a substitution weight percentage (5, 10, 15, 20 %) in water to adhesive material ratio equal 0.32. All mixes were examined by compressive, tensile strengths and water absorption tests with an appropriate fluidity, without having signs of segregation or instability. The test results were indicated that the SCC mixes containing MK and SF had higher compressive and tensile strengths in comparison with no-pozzolan concrete. The comparison of linear multiple regression techniques (LMRT) and nonlinear multiple regression technique outputs with experimental results showed an appropriate similarity.
The present investigation deals with the static analysis of adhesively bonded inner tapered double lap joint in laminated FRP composites subjected to transverse loading using three-dimensional theory of elasticity based finite element method. Many researchers studied the influences of various parameters on the failure behaviour on the composites. In those studies, the typical bonding parameters are surface conditions, fillet, bond line thickness, and environmental conditions. In the present study the stresses and deformation characteristics of adhesively bonded inner tapered double lap joint made of generally and especially orthotropic laminates (FRP) subjected to transverse loading for the three different adhesive angles, three different adhesive thicknesses with different fibre angle orientations, i.e. the adhesive angles from 350 to 450 increased in steps of 50. The variation in stresses and deflection are studied when the fibre angle orientation is varied from 00 to 900 in steps of 150. The adhesive thickness varies from 0.05 to 0.15 insteps of 0.05mm. In all the above cases stresses and displacements at various locations are evaluated for the static boundary conditions
Predicting Resilient Modulus of Clayey Subgrade Soils by Means of Cone Penetr...Pouyan Fakharian
Resilient modulus (Mr) of subgrade soils is considered as one of the most important factors for designing flexible pavements using empirical methods as well as mechanistic-empirical methods. The resilient modulus is commonly measured by a dynamic triaxial loading test, which is complex and expensive. In this research, back-propagation artificial neural network method has been employed to model the resilient modulus of clayey subgrade soils based on the results of the cone penetration test. The prediction of the resilient modulus of clayey subgrade soil can be possible through the developed neural network based on the parameters of the cone tip resistance (qc), sleeve friction (fs), moisture content (w), and dry density (γd). The results of the present study show that the coefficients of determination (R2) for training and testing sets are 0.9837 and 0.9757, respectively. According to the sensitivity analysis results, the moisture content is the least important parameter to predict the resilient modulus of clayey subgrade soils, while the importance of other parameters is almost the same. In this study, the effect of different parameters on the resilient modulus of clayey subgrade soil was evaluated using parametric analysis and it was found that with increasing the cone tip resistance (qc), the sleeve friction (fs) and the dry density (γd) and also with decreasing the moisture content (w) of soils, the resilient modulus of clayey subgrade soils increases.
This document provides an overview of fracture mechanics. It discusses brittle and ductile fracture, the three modes of failure, energy release rate and crack resistance parameters like the J-integral and stress intensity factor. It also covers crack growth, applications of fracture mechanics like designing and material selection, and explains concepts such as the critical stress intensity factor and T-stress in less than three sentences.
This document summarizes a study on developing a fracture mechanics model to predict the insertion force of needles cutting through tissue. Experimental tests were conducted to determine the fracture toughness, shear modulus, frictional force, and crack length for different size needles inserted at various speeds into porcine skin. A force model was developed incorporating these parameters and validated against experimental force measurements, with errors less than 0.2 N. The model accurately predicts insertion forces and shows that 61% of the force comes from creating a crack in the tissue, while 21% is from friction and 18% from spreading the tissue. Increasing insertion speed was found to not reduce force for porcine skin.
Literature Review of Experimental Study on Load Bearing Masonry WallIOSRJMCE
Masonry load bearing wall subjected to vertical concentric and eccentric loading may collapse through instability. In this Paper the buckling behavior of masonry load bearing wall of different slenderness ratio were investigated by many researcher has been reviewed via testing a series of scale masonry wall subjected to concentric and eccentric vertical loading. The influence of nonlinear behavior of interface element, slenderness ratio and various end conditions have been investigated together with the effect of different end eccentricity of vertical load.
The document summarizes a study on heterogeneous deformation and dislocation dynamics in compressed copper micropillars using multi-scale discrete dislocation plasticity modeling. The model couples 3D finite element analysis to calculate stress distributions and image stresses with 3D discrete dislocation dynamics. It captures size effects, hardening behavior, and the influence of boundary conditions. Results show hardening is due to dislocation entanglement and stagnation, with stress concentrations affecting heterogeneous deformation.
STRUCTURAL RELIABILITY ASSESSMENT WITH STOCHASTIC PARAMETERSP singh
The performance of a structure [23] is assessed by its safety [1], serviceability [1] and economy [1]. Since we do not know the exact details of loads [4] acting on a structure at any time, there is always some uncertainty about the total loads on structure. Thus random variables (means stochastic variable) of loads and other parameters are the main criteria of design variables [18]. They vary with space and time. The input variables is never certain and complete. The safety factor provided in the existing codes and standers primarily based on practice, judgment and experience, may not be adequate and economical. Using the techniques presented earlier, we can design or analyze individual members in the contest of structural reliability [2][3][22][24]. However we are not examined how the system performs [23] or how to calculate the reliability of the structure as a whole.
Soil sheet pile interaction part i a review of theories and design methodsIAEME Publication
This document summarizes theories and modeling methods for studying the interaction between soil and sheet pile walls. It discusses the complex nonlinear behavior of soil-sheet pile interaction and reviews various modeling approaches used to analyze it, including the Mohr-Coulomb and cap models. It also reviews conventional design theories for sheet piles, such as the Coulomb and Rankine theories. The document emphasizes the importance of numerical analysis tools like the finite element method in accurately modeling the interaction between soil and sheet piles.
A new proposed approach for moment capacity estimation of ferrocement members...Pouyan Fakharian
Ferrocement composites are widely used as a novel method for many different structural purposes recently. The uniform distribution and the high surface area-to-volume ratio of the reinforcement of such composites would improve the crack-arresting mechanism. Given these properties, ferrocement is an ideal option as a replacement for some traditional structures methods. In members with axially loaded reinforced concrete ferrocement composite, it would be the best alternative to use ferrocement members. Lack of sufficient research in this approach is the cause of not well defining this field for RC structures. This study has aimed to evaluate the moment capacity of ferrocement members using the GMDH method. Mechanical and geometrical parameters including the width of specimens, total depth specimens, compressive strength of ferrocement, ultimate strength of wire mesh and volume fraction of wire mesh are considered as inputs to predict the moment capacity of ferrocement members. For evaluating this model, mean absolute error (MAE), root mean absolute error (RMAE), normalized root mean square error (NRMSE) and mean absolute percentage error (MAPE) were carried out. The results conducted that the GMDH model is significantly better than some previous models and comparable to some other methods. Moreover, a new formulation for moment capacity of ferrocement members based on GMDH approach is presented. Finally, Sensitivity analysis is operated to understand the influence of each input parameters on moment capacity of ferrocement members.
Some Studies on Mode-II Fracture of Light Weight Blended Aggregate ConcreteIOSR Journals
Blended aggregate in concrete and arriving at the structural properties of blended aggregate
concrete is a thrust area. Pumice is very light and porous igneous rock that is formed during volcanic
eruptions.Cinder is a waste material obtained from steel manufacturing units. Shear strength is a property of
major significance for wide range of civil engineering materials and structures. Shear and punching shear
failures particularly in deep beams, in corbels and in concrete flat slabs are considered to be more critical and
catastrophic than other types of failures. This area has received greater attention in recent years. For
investigating shear type of failures, from the literature it is found that double central notched (DCN) specimen
geometry proposed by Prakash Desai and V.Bhaskar Desai is supposed the best suited geometry. In this present
experimental investigation an attempt is made to study the Mode-II fracture property of light weight blended
aggregate cement concrete combining both the pumice and cinder in different proportions, and making use of
DCN test specimen geometry . By blending the pumice and cinder in different percentages of 0, 25, 50, 75 and
100 by volumeof concrete, a blended light weight aggregate concrete is prepared. By using this the property
such as in plane shear strength is studied. Finally an analysis is carried out regarding Mode-II fracture
properties of blended concrete. It is concluded that the Ultimate load in Mode-II is found to decrease
continuously with the percentage increase in Pumice aggregate content. It is also observed that the ultimate
stress in Mode II is found to increase continuously with percentage increase in cinder aggregate content.
This document summarizes a study that investigated the compressive behavior of rigid polyvinyl chloride (PVC) foam at strain rates up to 200 s-1. Tests were conducted on PVC foam samples with densities ranging from 45 to 200 kg/m3 in directions parallel and perpendicular to the foam's rise direction. Both quasi-static and dynamic compression tests were performed using a customized drop tower device. The results showed that strain rate effects were observed at higher densities when loading in the foam rise direction, with increased compressive strength and plateau stress at higher strain rates. However, no significant strain rate effect was observed when loading perpendicular to the foam rise direction. Scanning electron microscopy analysis indicated that plastic hinges were the primary deformation
The document summarizes a study of test data on the compressive strength of masonry walls made of hollow clay units. It finds that the geometrical properties of the units, such as the ratio of bearing area to gross area (b), have an important effect on wall strength beyond just the compressive strength of the units. For end-constructed walls, the study derived an empirical equation (Equation 4) that expresses wall strength M as a function of the mortar strength m, unit strength u, and the b ratio. This simple equation was found to reasonably fit the available test data.
The document summarizes a neighbor assisted distributed self-healing protocol (NDSP) for compromised node recovery in wireless sensor networks. The NDSP protocol allows a compromised sensor node to continuously and collectively recover from a compromised stage to a normal stage with the help of its neighbor nodes. The protocol detects compromised nodes and then replaces their seed values, which are used to generate encryption keys, with the seed values from neighboring healthy nodes in order to recover the compromised nodes and maintain data secrecy across the network. Simulation results showed that the presented NDSP scheme is effective and efficient at recovering compromised sensor nodes.
1) The document summarizes a study that evaluated non-clinical HIV/AIDS activities in Lagos State, Nigeria through surveys of secondary school and university students.
2) The study found gaps in HIV/AIDS awareness related to behavioral challenges, understanding of sexually transmitted infections, lack of transmission awareness, condom use, and fear of HIV/AIDS stigma.
3) To address these gaps, the study proposed a validated knowledge management framework to enhance HIV/AIDS information sharing and awareness of transmission and prevention factors in Lagos State.
DSNs & X.400 assist in ensuring email reliabilityIOSR Journals
This document discusses tools that can help ensure email reliability by automatically responding to reports of undeliverability. It describes how Delivery Status Notifications (DSNs) and the Alternate Recipient Assignment Service from the X.400 protocol can help detect email failures and retransmit messages to alternate recipients. The document provides background on how SMTP works and how messages can get lost, before explaining how DSNs provide positive and negative delivery feedback. It also discusses issues with using alternate recipients and describes an implementation of these reliability tools as a Java proxy application.
Development of Shape Based Leaf CategorizationIOSR Journals
The document describes a methodology for shape-based leaf categorization using image processing and computer vision techniques. The approach involves binarizing leaf images, detecting corners using Harris corner detection, determining the convex hull by joining corner points, and characterizing shapes by calculating internal angles of the convex hull. The internal angles of the input leaf image are compared to those of images in a database to retrieve the most similar leaf images based on matching angle arrays. Key steps include corner detection, convex hull formation, angle calculation, and angle array comparison for classification and retrieval of leaf images by shape.
This document summarizes an aerodynamic analysis of a car model conducted using computational fluid dynamics (CFD) software to reduce drag force. The original Swift Dzire car model and two modified models - a "fastback" design with a sloped rear and a model with a rear spoiler - were simulated at 144 km/hr. The original model had a drag coefficient of 0.375. The fastback design had a lower drag coefficient of 0.335 due to delayed flow separation at the rear. The spoiler model had an even lower drag coefficient of 0.35, as the inverted wing spoiler produced downward force to increase traction at high speeds. CFD analysis provided insight into pressure and velocity contours to understand
The document analyzes the chemical and nutritional profiles of the mesocarp (edible fleshy part) of three common varieties of Terminalia catappa (tropical almond tree). Proximate analysis found the mesocarp contains moderate amounts of protein, fiber, fat, ash and carbohydrates. Mineral analysis found it contains magnesium, potassium, calcium, sodium, iron and phosphorus. Anti-nutritional factors tannin and phytate were present but in low amounts not likely to cause health issues. The study concluded the three varieties have comparable nutritional compositions and the mesocarp is a good source of nutrients comparable to other fruits, making it suitable for human consumption.
The document proposes a new security method called Yours Advanced Security Hood (YASH) to prevent password cracking through brute force and dictionary attacks. YASH uses a two-level security approach:
1. It tracks the number of incorrect login attempts and activates a virtual machine crosschecking (VMC) process if the attempt threshold is exceeded, preventing the password from being matched to attempted passwords.
2. It allows the true user to initiate an unauthorised access control (UAC) using their mobile phone to signal that no attempts should be matched, protecting the account until the user deactivates UAC.
3. The system can then detect the true user by their ability to deactivate UAC through their
1) The document presents the results of a linear and non-linear analysis of reinforced concrete frames with members of varying inertia (non-prismatic beams) for buildings ranging from G+2 to G+10 storeys.
2) Both bare frames and frames with infill walls were analyzed considering different beam cross-sections - prismatic, linear haunch, parabolic haunch, and stepped haunch.
3) The linear analysis was performed using ETABS and considered parameters like fundamental time period, base shear, and top storey displacement. The non-linear analysis used pushover analysis in SAP2000 to determine effective time period, effective stiffness, and hinge formation patterns.
Bus Data Acquisition and Remote Monitoring System Using Gsm & CanIOSR Journals
This document describes the design of a bus data acquisition and remote monitoring system using GSM and CAN networks. The system uses wireless data acquisition units connected to sensors to acquire signals wirelessly. The data is transmitted to a receiver unit using Zigbee wireless transmission. The receiver unit then sends the data to a remote monitoring service center using GSM. The system implements CAN networks within the bus to connect electronic control units and allow communication between nodes. The goal is to remotely monitor and control bus systems from an off-site location.
Business Intelligence: A Rapidly Growing Option through Web MiningIOSR Journals
This document discusses web mining techniques for business intelligence. It begins with an introduction to web mining and its subfields of web content mining, web structure mining, and web usage mining. It then focuses on web usage mining, describing the process of preprocessing log data, discovering patterns using techniques like statistical analysis and association rule mining, and analyzing the patterns. The goal is to understand customer behavior and improve business functions like marketing through data collected from web servers, proxy servers, and clients.
IOSR Journal of Pharmacy and Biological Sciences(IOSR-JPBS) is an open access international journal that provides rapid publication (within a month) of articles in all areas of Pharmacy and Biological Science. The journal welcomes publications of high quality papers on theoretical developments and practical applications in Pharmacy and Biological Science. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
1) The document proposes a new energy-aware tree-based routing protocol for wireless sensor networks called Fast Convergence and Quick Route Updates Based Energy Aware Tree-Based Routing Protocol.
2) The protocol uses AODV routing to select paths based on distance and residual energy of sensor nodes. It performs load balancing to increase network lifetime.
3) The protocol was tested in NS-2 simulator and showed improvements in network lifetime, throughput, data loss and delay compared to existing models.
IOSR Journal of Humanities and Social Science is an International Journal edited by International Organization of Scientific Research (IOSR).The Journal provides a common forum where all aspects of humanities and social sciences are presented. IOSR-JHSS publishes original papers, review papers, conceptual framework, analytical and simulation models, case studies, empirical research, technical notes etc.
This document proposes a new approach called the Count based Secured Hash Algorithm. It introduces a new parameter β that represents the number of bits rotated to the right in the preprocessing step, which depends on the count of 1s in the input message. This increases security compared to traditional SHA algorithms where the rotation is fixed. It modifies the SHA-256, SHA-384 and SHA-512 functions by replacing the fixed rotation with a rotation based on the count. The algorithm has higher time complexity but provides better security by making the digest dependent on the message content through the count variable.
This document provides a review of evolutionary algorithms that have been used to optimize wireless sensor networks (WSNs). It begins with background on WSNs and discusses common issues like energy efficiency. It then reviews heuristic and metaheuristic approaches that have been used for clustering and routing in WSNs. The main part of the document focuses on four commonly used evolutionary algorithms - genetic algorithms, particle swarm optimization, harmony search algorithm, and flower pollination algorithm. For each algorithm, it provides an overview and details on how the algorithm works and pseudo-code. It concludes that these nature-inspired metaheuristic techniques can help optimize challenges in WSNs like cluster formation and energy consumption better than classical algorithms.
This document investigates how changing the position of the tool point on the moving platform affects the dynamic performance of a 3RRR planar parallel manipulator. Lagrange-d'Alembert formulation is used to develop the dynamic model. The manipulator's dimensions and parameters remain the same, while only the tool point position is changed. Simulation results show that locating the tool point at an optimal position reduces the generalized forces and energy consumption of the manipulator, improving its dynamic performance.
Wireless Data Acquisition System Using ARM Cortex M-3IOSR Journals
The document describes a wireless data acquisition system using an ARM Cortex M-3 processor. The system collects data from gas, humidity, and temperature sensors and transmits the data wirelessly via Bluetooth to a host computer. The host computer uses virtual instrument software to process and display the received data in real-time. The system provides wireless and real-time data collection that can be used in applications like industrial monitoring and mobile meter reading.
1) The document proposes an automated model to detect fake profiles and botnets on online social networks using steganography and watermarking techniques.
2) It describes embedding unique information like a user's email or username into profile pictures during upload using watermarking. This allows detecting stolen pictures used for fake profiles.
3) The model is extended to also search uploaded pictures against billions of online images to detect multiple uses of the same picture for different profiles, as watermarking alone may fail if the picture is edited. Detected users must then prove ownership rights to the picture.
Implementation of Efficiency CORDIC Algorithmfor Sine & Cosine GenerationIOSR Journals
Abstract: This paper presents an area-time efficient coordinate rotation digital computer (CORDIC) algorithm that completely eliminates the scale-factor. A generalized micro-rotation selection technique based on high speed most-significant-1-detection obviates the complex search algorithms for identifying the micro-rotations. This algorithm is redefined as the elementary angles for reducing the number of CORDIC iterations. Compared to the existing re-cursive architectures the proposed one has 17% lower slice-delay product on Xilinx Spartan XC2S200E device. The CORDIC processor pro-vides the flexibility to manipulate the number of iterations depending on the accuracy, area and latency requirements. Index Terms—coordinate rotation digital computer (CORDIC), cosine/sine, field-programmable gate array(FPGA),most-significant-1, recursive architecture.
A six-stroke engine provides two power strokes in each cycle, improving efficiency over a traditional four-stroke engine. It works by using the heat from the exhaust stroke to generate a secondary expansion and power stroke. The first four strokes are identical to a four-stroke engine. In the fifth stroke, water is injected into the hot combustion chamber and turns to steam, expanding to drive the piston down for a second power stroke. This recovers waste heat from the exhaust to improve fuel efficiency over a four-stroke engine by up to 30-40%. However, additional systems are required to inject water and utilize the secondary expansion, increasing complexity over a traditional design.
Experimental Determination of Fracture Energy by RILEM Methodtheijes
This paper deals with investigation of fracture energy (GF) of concrete. The study involves experimental determination of fracture energy (GF) by testing three point bend concrete beams of same size but varying notch to depth ratios. RILEM fracture energy (GF) and Stress Intensity factor values is determined
Can fracture mechanics predict damage due disaster of structureseSAT Publishing House
This document discusses how fracture mechanics can be used to better predict damage and failure of structures. It notes that current design codes are based on small-scale laboratory tests and do not account for size effects, which can lead to more brittle failures in larger structures. The document outlines how fracture mechanics considers factors like size effect, ductility, and minimum reinforcement that influence the strength and failure behavior of structures. It provides examples of how fracture mechanics has been applied to problems like evaluating shear strength in deep beams and investigating a failure of an oil platform structure. The document argues that fracture mechanics provides a more scientific basis for structural design compared to existing empirical code provisions.
Review on the Effect of Shear Connectors on Composite Deck SlabsIJAEMSJORNAL
This paper presents a review on the effect of shear connectors on composite deck slabs. Composite deck slabs consist of profile deck sheet and concrete. Several researchers have been studying the behaviour of composite slab but due to its complex behaviour yet it is not completely understood. The behaviour of composite slab directly depends on the deformability and contact strength. Here, some important literature reviews regarding composite slab behavior incorporating different profiles were discussed.
Study of Damage to ABS Specimens Submitted To Uniaxial Loadingtheijes
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
Theoretical work submitted to the Journal should be original in its motivation or modeling structure. Empirical analysis should be based on a theoretical framework and should be capable of replication. It is expected that all materials required for replication (including computer programs and data sets) should be available upon request to the authors.
The International Journal of Engineering & Science would take much care in making your article published without much delay with your kind cooperation.
The cutting-edge applications that the engineers are bringing with using finite element procedure for the human civilization and the emergence of new techniques in solving real-life scenarios in finite element procedures.
1) The document reviews several expressions proposed by researchers to calculate the equivalent width of diagonal struts used to model masonry-infilled reinforced concrete (RC) frames.
2) It applies these expressions to a sample one-bay one-story RC frame and analyzes the results using ABAQUS software to validate the modeling approach.
3) The study finds that the Paulay and Priestley expression, which defines the equivalent strut width as one-fourth the diagonal length of the infill panel, provides an average value that gives a reasonably accurate model for further analysis of RC infilled frames.
Vibration analysis of a cantilever beam with crack depth and crack location e...editorijrei
This document summarizes a study that analyzed the natural frequency of a cracked cantilever beam made of different metal alloys using finite element analysis. The researchers varied the crack depth and location in the beam and measured the resulting changes in natural frequency. They found that increasing crack depth or moving the crack location closer to the fixed end resulted in decreasing natural frequency. Aluminum alloy beams exhibited the highest natural frequencies while magnesium alloy beams had the lowest.
The Effect of Earthquake-induced Pounding on the Response of a Series of Neig...IJAEMSJORNAL
The phenomenon of pounding that occurs during earthquakes for adjacent buildings may cause severe damage to the structure and may cause a complete collapse of the structure. This paper aims to make a comparison between the practical and theoretical results resulting from the work of Matlab Code, taking into account the calculation of the pounding force between adjacent towers, and study the effect of changing the coefficient of restitution on the acceleration time history and pounding force between adjacent buildings, study the peak impact force with respect to the stiffness of impact spring element. An impact simulation is carried out numerically using a nonlinear viscoelastic model. The results showed that the higher the coefficient of restitution, the lower the pounding forces between adjacent buildings and the maximum acceleration value. It also resulted from the study that the higher the impact stiffness parameter, the greater the pounding force between adjacent buildings.
This document discusses the results of an investigation into splitting of timber dowel joints. It summarizes the following key points in 3 sentences:
The document critiques the empirical methods used in previous studies, arguing they do not fit theoretical models and have high variability. It then precisely fits the experimental data from one study to limit analysis theory, demonstrating a 10% coefficient of variation. The analysis shows the empirical data can be trusted but that exact theory, not empirical approaches, provides the proper design rules for timber dowel joints.
This paper presents a novel approach using cellular automata to model the durability analysis of concrete structures exposed to aggressive environmental agents. The diffusion of these agents is modeled using cellular automata, which represent physical systems with discrete space, time, and state values. Mechanical damage from diffusion is evaluated using degradation laws. The interaction of diffusion and structural behavior is captured by modeling stochastic effects in mass transfer. Nonlinear structural analyses over time are performed using a deteriorating concrete beam element within a finite element framework. The approach is demonstrated on applications including a concrete box girder, T-beam, and arch bridge to identify critical members.
Under repeated impact composite domes subjected 6 J energy, changes locally with
increasing drop height. The action of the dynamic load generates reactions at the
support and bending moments at points on the surface of the composite. The peak loads
were noted to increase and stabilise about some mean value; and the 150mm diameter
shell was more damage tolerant compared to the 200 mm diameter one.
Experimental composite dome under low velocity impact loadalilimam2
The document summarizes a study that characterized the impact response of glass fiber reinforced composite dome structures with diameters of 150mm and 200mm under repeated low-energy impacts. Key findings include:
1) Peak impact loads initially increased and stabilized with repeated impacts, and the 150mm diameter dome showed higher peak loads and was more damage tolerant.
2) Damage mechanisms included matrix cracking, delamination, and fiber pull-out. Delamination absorbed a large percentage of the impact energy.
3) Both dome configurations exhibited non-linear impact behavior, with stiffness reducing and energy dissipation decreasing with accumulated damage from repeated impacts.
An Experimental Study of Low Velocity Impact (Lvi) On Fibre Glass Reinforced ...theijes
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
All structures are subjected to degenerative effects that may
cause initiation of structural defects such as cracks which,
as time progresses, lead to the catastrophic failure or
breakdown of the structure. Thus, the importance of
inspection in the quality assurance of manufactured
products is well understood.
The document summarizes research on modeling the seismic pounding response of adjacent structures. It discusses two common methods for simulating pounding: the contact element method using linear springs and the stereomechanical method using impulse-momentum principles. The paper then presents the mathematical formulation for analyzing the time-domain response of a three-structure system with adjacent elastic and inelastic SDOF structures undergoing one-sided or two-sided pounding. The response is computed using the Newmark-Beta method with a linear spring contact element model.
Prediction of Ultimate Shear Strength of Moderate Deep Concrete Beam Includin...IRJET Journal
The document discusses predicting the ultimate shear strength of moderate deep concrete beams. It begins by defining shallow, moderate deep, and deep beams based on their span-to-depth and shear span-to-depth ratios. It then discusses how the stress distribution in moderate deep beams is non-linear and more complex than in shallow beams. The document proposes modifying an existing equation for predicting ultimate load by incorporating a size effect factor related to effective depth and compressive strength. The modified equation is checked against test data from 54 beams and shows good agreement compared to other code provisions and formulas.
1) The document investigates the effect of low-velocity impact and fatigue loading on woven glass fiber/epoxy composite laminates of different thicknesses (2mm and 4mm).
2) Specimens were subjected to low-velocity impact testing at different energy levels. Impacted specimens and non-impacted specimens were then subjected to tension-tension fatigue testing.
3) Results showed that impact velocity significantly influenced the fatigue life of composite laminates. The 2mm thick impacted laminates saw a drastic reduction in fatigue life compared to the 4mm laminates.
Engineering Fracture Mechanics. Engineers try to have high-strength, high ductility, high crack resistance, and faultless structures. The most reliable approach is "No cracks - no problems,"
When all is not possible, there are different methods of prevention of catastrophic failure: increase crack resistance by ductile material, by local heating; decrease SIF by placing holes on the crack path, by patching, by stiffing elements or by using composite materials. "Leak-before-break" is an effective strategy to prevent catastrophic failure of pressure vessels. It is better to allow a semi-elliptical crack to grow through the wall and to detect it by leaking than to have the dynamic start and failure of the whole vessel. There are two characteristics of the material: crack resistance for semi-elliptical crack and crack resistance for through crack.
This document summarizes research on the size effect in punching shear strength of reinforced concrete slabs. It reviews 87 experimental tests of slabs without shear reinforcement and compares the results to design codes like Eurocode 2 and the Critical Shear Crack Theory. The comparison shows Eurocode 2 and the Critical Shear Crack Theory provide reasonably accurate predictions of punching shear strength, while some other codes underestimate strength, especially for thinner slabs with low reinforcement ratios. Research indicates punching shear strength decreases as slab thickness increases, and size effect must be considered in accurate design calculations.
There appears to have been no review made of existing test data in which the size effect in punching has been given any special consideration and the proposed paper seeks to fill this gap. Its objectives are to set out the current state of knowledge on size effects and the parameters that influence them by considering of experimental results of 87 reinforced concrete flat slabs without shear reinforcement. These tests are carefully selected to form a large database, including specimens with a significant variation of effective depth. These experimental results are compared with design codes of EUROCODE 2, FIB Model 2010 and to the Critical Shear Crack Theory (CSCT) by Muttoni et al. The comparison show that both EC2 and CSCT have good prediction to test results
while MC90 is rather underestimate the punching shear strength of thinner slab compared to EC2 particularly for reinforcement ratio less than 0.1% and this is due to ignoring the limit on the factor of size effect beyond of 2.0.
This document provides a technical review of secure banking using RSA and AES encryption methodologies. It discusses how RSA and AES are commonly used encryption standards for secure data transmission between ATMs and bank servers. The document first provides background on ATM security measures and risks of attacks. It then reviews related work analyzing encryption techniques. The document proposes using a one-time password in addition to a PIN for ATM authentication. It concludes that implementing encryption standards like RSA and AES can make transactions more secure and build trust in online banking.
This document analyzes the performance of various modulation schemes for achieving energy efficient communication over fading channels in wireless sensor networks. It finds that for long transmission distances, low-order modulations like BPSK are optimal due to their lower SNR requirements. However, as transmission distance decreases, higher-order modulations like 16-QAM and 64-QAM become more optimal since they can transmit more bits per symbol, outweighing their higher SNR needs. Simulations show lifetime extensions up to 550% are possible in short-range networks by using higher-order modulations instead of just BPSK. The optimal modulation depends on transmission distance and balancing the energy used by electronic components versus power amplifiers.
This document provides a review of mobility management techniques in vehicular ad hoc networks (VANETs). It discusses three modes of communication in VANETs: vehicle-to-infrastructure (V2I), vehicle-to-vehicle (V2V), and hybrid vehicle (HV) communication. For each communication mode, different mobility management schemes are required due to their unique characteristics. The document also discusses mobility management challenges in VANETs and outlines some open research issues in improving mobility management for seamless communication in these dynamic networks.
This document provides a review of different techniques for segmenting brain MRI images to detect tumors. It compares the K-means and Fuzzy C-means clustering algorithms. K-means is an exclusive clustering algorithm that groups data points into distinct clusters, while Fuzzy C-means is an overlapping clustering algorithm that allows data points to belong to multiple clusters. The document finds that Fuzzy C-means requires more time for brain tumor detection compared to other methods like hierarchical clustering or K-means. It also reviews related work applying these clustering algorithms to segment brain MRI images.
1) The document simulates and compares the performance of AODV and DSDV routing protocols in a mobile ad hoc network under three conditions: when users are fixed, when users move towards the base station, and when users move away from the base station.
2) The results show that both protocols have higher packet delivery and lower packet loss when users are either fixed or moving towards the base station, since signal strength is better in those scenarios. Performance degrades when users move away from the base station due to weaker signals.
3) AODV generally has better performance than DSDV, with higher throughput and packet delivery rates observed across the different user mobility conditions.
This document describes the design and implementation of 4-bit QPSK and 256-bit QAM modulation techniques using MATLAB. It compares the two techniques based on SNR, BER, and efficiency. The key steps of implementing each technique in MATLAB are outlined, including generating random bits, modulation, adding noise, and measuring BER. Simulation results show scatter plots and eye diagrams of the modulated signals. A table compares the results, showing that 256-bit QAM provides better performance than 4-bit QPSK. The document concludes that QAM modulation is more effective for digital transmission systems.
The document proposes a hybrid technique using Anisotropic Scale Invariant Feature Transform (A-SIFT) and Robust Ensemble Support Vector Machine (RESVM) to accurately identify faces in images. A-SIFT improves upon traditional SIFT by applying anisotropic scaling to extract richer directional keypoints. Keypoints are processed with RESVM and hypothesis testing to increase accuracy above 95% by repeatedly reprocessing images until the threshold is met. The technique was tested on similar and different facial images and achieved better results than SIFT in retrieval time and reduced keypoints.
This document studies the effects of dielectric superstrate thickness on microstrip patch antenna parameters. Three types of probes-fed patch antennas (rectangular, circular, and square) were designed to operate at 2.4 GHz using Arlondiclad 880 substrate. The antennas were tested with and without an Arlondiclad 880 superstrate of varying thicknesses. It was found that adding a superstrate slightly degraded performance by lowering the resonant frequency and increasing return loss and VSWR, while decreasing bandwidth and gain. Specifically, increasing the superstrate thickness or dielectric constant resulted in greater changes to the antenna parameters.
This document describes a wireless environment monitoring system that utilizes soil energy as a sustainable power source for wireless sensors. The system uses a microbial fuel cell to generate electricity from the microbial activity in soil. Two microbial fuel cells were created using different soil types and various additives to produce different current and voltage outputs. An electronic circuit was designed on a printed circuit board with components like a microcontroller and ZigBee transceiver. Sensors for temperature and humidity were connected to the circuit to monitor the environment wirelessly. The system provides a low-cost way to power remote sensors without needing battery replacement and avoids the high costs of wiring a power source.
1) The document proposes a model for a frequency tunable inverted-F antenna that uses ferrite material.
2) The resonant frequency of the antenna can be significantly shifted from 2.41GHz to 3.15GHz, a 31% shift, by increasing the static magnetic field placed on the ferrite material.
3) Altering the permeability of the ferrite allows tuning of the antenna's resonant frequency without changing the physical dimensions, providing flexibility to operate over a wide frequency range.
This document summarizes a research paper that presents a speech enhancement method using stationary wavelet transform. The method first classifies speech into voiced, unvoiced, and silence regions based on short-time energy. It then applies different thresholding techniques to the wavelet coefficients of each region - modified hard thresholding for voiced speech, semi-soft thresholding for unvoiced speech, and setting coefficients to zero for silence. Experimental results using speech from the TIMIT database corrupted with white Gaussian noise at various SNR levels show improved performance over other popular denoising methods.
This document reviews the design of an energy-optimized wireless sensor node that encrypts data for transmission. It discusses how sensing schemes that group nodes into clusters and transmit aggregated data can reduce energy consumption compared to individual node transmissions. The proposed node design calculates the minimum transmission power needed based on received signal strength and uses a periodic sleep/wake cycle to optimize energy when not sensing or transmitting. It aims to encrypt data at both the node and network level to further optimize energy usage for wireless communication.
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1. IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE)
e-ISSN: 2278-1684,p-ISSN: 2320-334X, Volume 12, Issue 3 Ver. II (May - Jun. 2015), PP 54-59
www.iosrjournals.org
DOI: 10.9790/1684-12325459 www.iosrjournals.org 54 | Page
Models and Size Effects: A Review
A. Mohammed1, N. Muazu2, B. S. Waziri2 & T. Y Ahmad1
1
Lecturer, Civil Engineering Department, Abubakar Tafawa Balewa University, Bauchi,
2
Lecturer, Civil Engineering Department, University of Maiduguri
Abstract: Small scale modelling of structures is normally employed as a means to study the structural behaviour
of engineering structures in order to predict the real behaviour of such structures under various conditions of
loading as well as under the influence of extreme weather events like flooding, earthquakes, severe wind storms
etc. But in order to use small scale models to predict prototype behaviour, understanding is necessary of the
effect of scale on such models. The fracture mechanics perspective of the effects of size on models is explored
from available literature and its significance to reliable model studies is established in this review.
Keywords: Models, size effects, small scale, fracture mechanics, strength.
I. Introduction
Historically the value in scale models lies in being able to predict the behaviour of a prototype model
from the scale model. Presently small models are usually used to validate numerical models which will then be
used to predict the structural behaviour of whole structures like model arch bridges and buildings. However for
a researcher to be able to predict this with some degree of confidence, knowledge is required of the effect of size
or scale on the model material. This becomes more important in the case of composites like masonry where the
constituent brick and mortar have different properties. Therefore an appreciation is needed of the effect of size
or scale on the model material, if reliable model studies are to be made.
Size effect
Scale effect is a phenomenon related to the change, usually an increase in strength that occurs when the
specimen size is reduced [1]. The importance of this effect cannot be overemphasised as more and more reduced
scale model studies are being undertaken for the prediction of various aspects of prototype behaviour and design
strengths (that is in codes and standards). Correct understanding of size effects is also necessary for the accurate
interpretation of material properties tests of various sizes and shapes in different parts of the globe.
History
The subject of size effect of objects was discussed by Leonardi da Vinci as early as the 1500’s, and
concluded that “among cords of equal thickness the longest is the least strong”. He also added that a cord “is so
much stronger … as it is shorter”[2]. After more than a century Galileo, in 1638, rejected Leonardo’s
exaggerated rule and argued that cutting a long cord at various points should not necessarily make the remainder
stronger. However he added that a size effect is seen because large animals have relatively bulkier bones than
small ones, which he referred to as the “weakness of giants”.
Some decades later Mariotte experimented with ropes, paper and tin and concluded that “a long rope
and a short one always support the same weight except that in a long rope there may happen to be some faulty
place in which it will break sooner than in a shorter (one)” He suggested that this is as a result of the principle of
“the inequality of matter whose absolute resistance is less in one place than (in) another”. In effect he had put
the foundations of the statistical theory of size effect, two and half centuries before Weibull.
Griffith’s [2]famous work in 1921 followed, which founded the theory of fracture mechanics and also
introduced fracture mechanics into study of size effect. Griffith concluded from his observations that “the
weakness of isotropic solids… is due to the presence of discontinuities or flaws. The effective strength of
technical materials could be increased 10 or 20 times at least if these flaws could be eliminated”. His work in
effect provided an experimental basis of Mariottes’s statistical concept of size effect rather than a discovery of a
new type of size effect[2]. Weibull then completed the statistical size effect initiated by Mariotte in a series of
papers over 17 years from 1939-1956[2]. Most of the studies thereafter until the 1980s dealt with the purely
statistical origin for size effect on the strength of quasi-brittle materials, therefore until the mid 1980’s size
effect on strength was thought of as having a statistical origin. This is seen in Sabnis’s review[3] of studies in
the area in which he only discussed the known statistical concepts at that time of bundled strength and weakest
link. The most notable of the statistical concepts was the latter, which holds that, the presence of a single severe
defect in any of the constituent elements is adequate to cause failure of the whole material. Consequently the
failure strength of a specimen subjected to uniform stress is determined by the strength of the weakest element
present. The most prominent exponent of this theory was Weibull [3].
2. Models And Size Effects: A Review
DOI: 10.9790/1684-12325459 www.iosrjournals.org 55 | Page
The energetic and deterministic size effect
In Linear Elastic Fracture Mechanics (LEFM), where the failure criterion is expressed in terms of the
energy consumed per unit crack length increment. The fracture process is assumed to occur at one point, the
crack tip, which exhibits the strongest possible size effect. In this case the nominal strength is inversely
proportional to the square root of structure size [4]. But this is only true if the cracks are large and there is a
sudden failure at the start of cracking. This theory can therefore, only be true for very large structures in which
failure occurs immediately after crack initiation. However it has been observed that concrete test data do not
follow LEFM criteria, neither do they obey strength theory, in which there is no size effect. Therefore there is
need for a non-linear form of fracture mechanics that takes into account the stable crack growth and the large
micro-cracked zone of the fracture surface. This criteria or law as shown in Figure 1, bridges the zero size effect
of the strength criterion and the size effect predicted by LEFM because it recognizes the large size of the micro-
cracked zone of quasibrittle materials like concrete, rocks and clay bricks. It is seen from the figure that most
structures lie in between the strength criterion (most laboratory tests) and LEFM (very large structures like
dams). This figure suggests that there may not be a strong size effect for most tests conducted in laboratories
with a relatively small size for a reference structural size D (as defined below). This could apply to this
investigation since the tests would be on small masonry assemblies and not large masonry structures.
The size effect derived by [5] is based on the theory of stress redistribution and fracture energy release.
It is assumed that the length of a crack at maximum load is proportional to a reference structure size D (say
beam depth) while the size (width) of a fracture process zone at maximum load is constant, related to the
heterogeneity of the material. The fracture energy, Gf is defined as a material property representing the amount
of energy required to propagate a unit area of crack, then the energy used and released by fracture is
proportional to GfD[2]. Because the energy required to produce a unit fracture extension is approximately
independent of the structural size, the nominal stress at failure of a larger structure is lower than for a smaller
one, so that the energy release would exactly match the energy required for the fracture formation[6].
The size effect on structural strength is taken as the effect of the characteristic structure size (say D) on
the nominal strength N of the structure when geometrically similar structures are compared. This size effect in
two dimensions is defined in terms of a nominal stress at failure in Equation 1
σN = Cn( Pu/bD) (1)
Where Pu = maximum (ultimate) load, b = thickness of specimen or structure, D = characteristic dimension, and
Cn = dimensionless constant. This is rewritten in terms of size effect of fracture mechanics type in the form of
Equation 2
σN =
)1(
to fB
, D /Do (2)
Where ft = is a measure of material strength introduced to make Bo non-dimensional and Bo and Do are empirical
constants; coefficients Bo and Do represent specimen shape and size. This assumes that the thickness b =
constant for different D and also the specimen proportions are constant for all sizes. When the specimen is
small, plasticity is also small, size effect does not manifest at these smaller values of β, and effectively results in
a horizontal curve as seen in Figure 1. At intermediate values, there is a smooth transition and in the case of
LEFM at large sizes (β→∞) at which case size effect is very pronounced it approaches the asymptote with slope
of 1:2[1].
Equation 2 can be transformed to a linear plot in the form of Equations 3 and 4
Y = AX+ C (3)
Where X = D, Y =
2
1
N
, A = 22
1
too fBD
, and C = ADo (4)
The intercept C and slope A can be determined through linear regression analysis of data.
Some criticisms abound in the literature regarding the applicability of the law to unnotched structures.
[7] observed that in deriving the formula the energy dissipated to cause fracture in a notched specimen is
proportional to GfD, and D is proportional to the crack length. But for unnotched specimens the length of the
characteristic flaw responsible for crack propagation is independent of specimen size, which therefore causes the
anomalous behaviour of Bazant’s formula. However [8] argues it is misleading to use Equation (1) for
unnotched specimens since its modification has been derived to cater for unnotched specimens as given in
Equation 5;
3. Models And Size Effects: A Review
DOI: 10.9790/1684-12325459 www.iosrjournals.org 56 | Page
r
b
N
D
rD
k
1
0 1
(5)
Equation (5) was derived for the modulus of rupture of a notchless concrete beam, where
tfLD 320 and bD is the thickness of the boundary layer of cracking are both constants because the
ratio D/L is constant for geometrically similar structures. D and L are the beam depth and length respectively, r
and k are positive constants (usually k = 1 and r = 1 or 2)[9].
The theory of Crack Fractality or the Multifractal Scaling Laws (MFSL).
Theory of crack fractality or the Multifractal scaling Laws (MFSL) can be of two types;
1. Invasive fractality of the crack surface; referring to the fractal nature of surface roughness.
2. Lacunar fractality; referring to the fractal distribution of microcracks.
This theory proposed by Carpenteri and his co workers[10-12] holds that the difference in fractal
characteristics of cracks at different scales of observation is the main source of size effect in disordered
materials. The nominal stress from this law is given by Equation 6
2
1
1
b
l
f ch
tU (6)
Where b is the characteristic dimension of the structure and lch is a characteristic length related to the
material microstructure. The scaling relationship shown in Figure 2(a) is a two-parameter model, where the
asymptotical value of the nominal strength ft corresponding to the lowest tensile strength is reached only in the
limit of infinite sizes. The dimensionless term (1+ lch/b) in Equation 6 represents the variable influence of
disorder, consequently quantifying the difference between the nominal quantity measured at scale b and the
asymptotic value. In the logarithmic plot shown in Figure 2(b), the transition from the fractal regime to the
homogeneous becomes clear. The threshold of this transition is represented by point Q, whose ordinate and
abscissa are log ft and log lch respectively.
Some observations have been made by [2, 8] on the MFSL some of which are:
1. That the MFSL is identical to a special case of the energetic- statistical scaling law for failure at crack
initiation (Equation (5)).
2. That the derivation of MFSL from fractal concepts includes problematic steps which invalidate it and that
the MFSL does not follow mathematically from the fractal hypothesis made by its proponents.
3. That the MFSL cannot predict the dependence of size effect law parameters on the structure geometry. On
the other hand, the energetic theories are able to predict their dependence.
It can be seen that taking k = 1 and r = 2 in Equation (5) gives
2
1
0
2
1
D
Db
N (7)
The remarkable similarity between Equations 5 and 7 is then apparent, and the constants in the equations can
easily be obtained through statistical regression of test data as before.
Karihaloo’s size effect formula for notched quasi-brittle structures
[13] used the concept of a fictitious crack model (FCM) to arrive at a size effect formula for the nominal
strength of notched three point bend fracture specimens of concrete and other quasi-brittle structures defined as
2
1
1
W
B
AN (8)
Where
g
g
lBA p
2
1
; (9)
Where pl and refer to the size of the fracture process zone in a very large specimen W and its
nominal strength, while g and g are a non- dimensional geometry factor and its first derivative,
4. Models And Size Effects: A Review
DOI: 10.9790/1684-12325459 www.iosrjournals.org 57 | Page
respectively. They depend on the notch to depth ratio Wa . Deficiencies and refinements to Equation (8)
have been discussed by [14] and [15] and will not be covered here.
Factors affecting size/scale Effect
A number of factors affect the strength properties and ultimately the overall behaviour of quasi-brittle
materials. Some of the strength properties include compressive, tensile, tensile, bond and fatigue strengths, and
various dimensional changes including creep. The materials affected by size effect range from naturally
occurring rock, timber etc to man made materials like concrete, steel etc and even composites like masonry[16].
Random strength
Random strength describes the effect random distribution of flaws has in a heterogeneous material. It
plays an important role in the micro mechanisms determining the strength of materials. Thus a larger specimen
should have more flaws and consequently less strong than a smaller specimen with fewer flaws[1].
Compaction
Generally smaller specimens of mortar or concrete will tend to achieve better compaction and higher
density and thus a higher strength because of their smaller volumes. This is especially the case when standard
compaction procedures are employed through vibration for a given time or specific number of tampings[1].
Curing and drying
Curing is an important variable influencing mortar strength. Two specimens of different sizes will cure
differently because the surface to volume ratio increases with decrease in specimen size. The strength of the
material will vary from the surface of the specimen to its centre, depending on its size, since hydration may not
be uniform throughout the specimen at the time of testing[1].
Drying of the specimen will also influence the gain in strength as a result of the surface to volume ratio,
which varies inversely with the specimen size[1].
Loading rate and state of stress
The rate of loading influences the strength of specimens, because higher loading rates lead to higher
strengths. The stress of stress, for example compression, tension, and flexure, also influences the strength of the
specimen. For instance the strength of compressive specimens depends on the accuracy of the loaded ends, and
on parallelism, if rotating heads are not used. It is also possible to achieve a higher level of capping accuracy in
smaller specimens, which will result in higher strength[1].
Testing machine and loading platens
Properties of the testing machine such as the stiffness of the loading platens have a profound effect on
test results. Stiff end plates tend to apply uniform strain conditions to the specimen under test, thus resulting in a
higher strength than if thinner plates were used[1].
Compaction of mortar bed by masonry units
Because of the heavier masses of larger masonry units, they tend apply more pressure on the mortar
bed than smaller units. This observation was made by [17] as a possible cause for the decrease in stiffness as
masonry model size is reduced.
II. Conclusions
The forgoing has shown the importance of size effects if reliable and repeatable model studies are to be
made. The importance of this effect cannot be overemphasised more so, because of the different specimen sizes
around the world and also as more and more reduced scale model studies are being undertaken for the prediction
of various aspects of prototype behaviour and design strengths in codes and standards.
5. Models And Size Effects: A Review
DOI: 10.9790/1684-12325459 www.iosrjournals.org 58 | Page
0
2
4
6
8
10
12
14
0.01 0.1 1 10 100Log (Size)
NominalStressatFailure,sN
Most structures
2
1
Strength or yield criterion
LEFM
Nonlinear Fracture
Mechanics
Most lab tests
Figure 1- Size effect according to strength criteria, linear and nonlinear fracture mechanics.
logb
Logf t
log s u
Q
logl ch
Extreme disorder
(fractal regime)
(b)
b
f t
s U
1
2
Extreme order (homogeneous regime)
(a)
logb
Logf t
log s u
Q
logl ch
Extreme disorder
(fractal regime)
(b)
b
1
2
Extreme order (homogeneous regime)
y
x
s y
Figure 2 - (a) Multifractal scaling law (MFSL) for tensile strength, (b) Bilogarithmic diagram for the same.
References
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[2]. Bazant ZP. Scaling of structural strength. London: Hermes Penton Ltd 2002.
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conference. Knoxville, TN 1980:649-68.
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6. Models And Size Effects: A Review
DOI: 10.9790/1684-12325459 www.iosrjournals.org 59 | Page
[6]. Lourenco PB. Two aspects related to the analysis of masonry structures: size effect and parameter sensitivity.: Delft University of
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