This document summarizes experimental and analytical investigations of the 3-D vibrations of a base isolated school building in Macedonia. Ambient vibration tests were performed to determine the building's natural frequencies and mode shapes. Forced vibration tests were also conducted to further characterize the building's dynamic properties. A 3-D finite element model was developed and analyzed to calculate the natural frequencies and compare with experimental results. The results from both experimental and analytical studies of the base isolated structure are presented and discussed.
Effectiveness Evaluation of Seismic Protection Devices for Bridges in the PB...Franco Bontempi
Seismic protection measures for bridges can be used both for obtaining acceptable performances from new structures that for retrofitting existing ones. With the modern design philosophy based on probabilistic Performance-Based Earthquake Engineering (PBEE) approaches, the engineers are allowed to investigate different design solutions in terms of vulnerability assessment. However, if probabilistic PBEE approaches are nowadays well established and widely studied also for bridges, the topic of using the PBEE frameworks for the evaluation of the effectiveness of seismic protection devices for bridges is not extensively treated in literature.
The first objective of this work is to deal with the problem of assessing the earthquake performance of an highway bridge equipped with different bearing device: the
elastomeric bearings (ERB) and the friction pendulum systems (FPS). The second purpose is to evaluate the efficiency of a structure-dependent IM in case of isolated system. The examined structure is an highway bridge with concrete piers and steel truss deck. A FE model of the bridge is developed by using nonlinear beam-column elements with fiber section and the devices are modeled by specific elements implementing their
nonlinear behavior. The effectiveness of the different retrofitting strategies has been carried out in terms of damage probability. Choosing the example of slight damage, and referring to the curvature ductility as EDP, the probability of damage during a period of 50 years is: 23% for the structure without isolation, 7% for the structure equipped with ERB, and 3% for the structure equipped with FPS isolation.
The International Journal of Engineering and Science (The IJES)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.
Comparative Analysis of Frames with Varying InertiaIJERA Editor
This paper presents an elastic seismic response of reinforced concrete frames with 3 variations of heights, i.e. (G+2), (G+4), (G+6) storey models are compared for bare frame and frame with brick infill structures which have been analyzed for gravity as well as seismic forces and their response is studied as the geometric parameters varying from view point of predicting behavior of similar structures subjected to similar loads or load combinations. In this study, two different cases are selected i.e. frames with prismatic members and frames with non-prismatic members. The structural response of various members when geometry changes physically, as in case of linear and parabolic haunches provided beyond the face of columns at beam column joints or step variations as in case of stepped haunches was also studied. Frames have been analyzed statically as well as dynamically using ETABS-9.7.4 software referring IS: 456-2000, IS: 1893 (Part-1)2002 and the results so obtained are grouped into various categories.
Out of Plane Behavior of Contained Masonry Infilled Frames Subjected to Seism...paperpublications3
Abstract: Brick masonry infill although considered as non-structural element largely affects the strength, stiffness and ductility of the reinforced concrete frames during the application of lateral loads due to wind or earthquake. Contained masonry refers here to the brick masonry which is used as infill in a reinforced concrete frame, wound round with 8mm diameter mild steel wires in vertical and horizontal directions and stitched to the brick masonry as well as to the reinforced concrete frames. This thesis focuses on the seismic behaviour of reinforced concrete structures with contained masonry infill, with a particular interest in the development of rational procedures for the analysis and design of RC frames with contained masonry infill. The estimation of the natural frequencies of the structural system is the basic investigation in dynamic analysis of a structure. Therefore the analysis is primarily to find out the modal frequencies of the structure and to simulate the mathematical model to earthquake loads. The structure vibrates in different modes when the earthquake takes place. The methodology suggested is to carry out a detailed study on the influence of contained masonry infill including un-reinforced masonry infill in multi-storey Reinforced Concrete frames on the fundamental natural frequencies and response due to various earthquake excitation forces. Numerical Finite element analysis is carried out on two dimensional Reinforced Concrete Frames under different configurations of contained masonry infill in addition to plain masonry and bare frames. The RC frames were designed and detailed as per relevant Indian standard codes. The present work consists of study of the behaviour of five storeyed RC frames infilled with contained masonry and also infilled with plain masonry, subjected to various earthquake excitation forces. Three types of models are considered for analysis; five storey frames of 4m wide, 5m wide and 6m wide models having total height of 16m with plain masonry infill and contained masonry infill are considered.
In this study, Non-linear response of concrete with differential value of Young’s Modulus is determined by the stress strain expression. The modulus of elasticity is varied throughout to evaluate the non-linear response of concrete structure at a constant load. The modeling of structure is done in STAAD PRO Vi8 software. In this study, single storey-single bay frame is modeled which is subjected to dead load and uniform loads, has been considered for the non-linear response of concrete structures. A structural element such as Column is used for evaluation of the non-linear response of concrete material. From this, deflection of the column element is carried out by using STAAD PRO software with different initial tangent modulus of elasticity at a constant loading.
Effectiveness Evaluation of Seismic Protection Devices for Bridges in the PB...Franco Bontempi
Seismic protection measures for bridges can be used both for obtaining acceptable performances from new structures that for retrofitting existing ones. With the modern design philosophy based on probabilistic Performance-Based Earthquake Engineering (PBEE) approaches, the engineers are allowed to investigate different design solutions in terms of vulnerability assessment. However, if probabilistic PBEE approaches are nowadays well established and widely studied also for bridges, the topic of using the PBEE frameworks for the evaluation of the effectiveness of seismic protection devices for bridges is not extensively treated in literature.
The first objective of this work is to deal with the problem of assessing the earthquake performance of an highway bridge equipped with different bearing device: the
elastomeric bearings (ERB) and the friction pendulum systems (FPS). The second purpose is to evaluate the efficiency of a structure-dependent IM in case of isolated system. The examined structure is an highway bridge with concrete piers and steel truss deck. A FE model of the bridge is developed by using nonlinear beam-column elements with fiber section and the devices are modeled by specific elements implementing their
nonlinear behavior. The effectiveness of the different retrofitting strategies has been carried out in terms of damage probability. Choosing the example of slight damage, and referring to the curvature ductility as EDP, the probability of damage during a period of 50 years is: 23% for the structure without isolation, 7% for the structure equipped with ERB, and 3% for the structure equipped with FPS isolation.
The International Journal of Engineering and Science (The IJES)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.
Comparative Analysis of Frames with Varying InertiaIJERA Editor
This paper presents an elastic seismic response of reinforced concrete frames with 3 variations of heights, i.e. (G+2), (G+4), (G+6) storey models are compared for bare frame and frame with brick infill structures which have been analyzed for gravity as well as seismic forces and their response is studied as the geometric parameters varying from view point of predicting behavior of similar structures subjected to similar loads or load combinations. In this study, two different cases are selected i.e. frames with prismatic members and frames with non-prismatic members. The structural response of various members when geometry changes physically, as in case of linear and parabolic haunches provided beyond the face of columns at beam column joints or step variations as in case of stepped haunches was also studied. Frames have been analyzed statically as well as dynamically using ETABS-9.7.4 software referring IS: 456-2000, IS: 1893 (Part-1)2002 and the results so obtained are grouped into various categories.
Out of Plane Behavior of Contained Masonry Infilled Frames Subjected to Seism...paperpublications3
Abstract: Brick masonry infill although considered as non-structural element largely affects the strength, stiffness and ductility of the reinforced concrete frames during the application of lateral loads due to wind or earthquake. Contained masonry refers here to the brick masonry which is used as infill in a reinforced concrete frame, wound round with 8mm diameter mild steel wires in vertical and horizontal directions and stitched to the brick masonry as well as to the reinforced concrete frames. This thesis focuses on the seismic behaviour of reinforced concrete structures with contained masonry infill, with a particular interest in the development of rational procedures for the analysis and design of RC frames with contained masonry infill. The estimation of the natural frequencies of the structural system is the basic investigation in dynamic analysis of a structure. Therefore the analysis is primarily to find out the modal frequencies of the structure and to simulate the mathematical model to earthquake loads. The structure vibrates in different modes when the earthquake takes place. The methodology suggested is to carry out a detailed study on the influence of contained masonry infill including un-reinforced masonry infill in multi-storey Reinforced Concrete frames on the fundamental natural frequencies and response due to various earthquake excitation forces. Numerical Finite element analysis is carried out on two dimensional Reinforced Concrete Frames under different configurations of contained masonry infill in addition to plain masonry and bare frames. The RC frames were designed and detailed as per relevant Indian standard codes. The present work consists of study of the behaviour of five storeyed RC frames infilled with contained masonry and also infilled with plain masonry, subjected to various earthquake excitation forces. Three types of models are considered for analysis; five storey frames of 4m wide, 5m wide and 6m wide models having total height of 16m with plain masonry infill and contained masonry infill are considered.
In this study, Non-linear response of concrete with differential value of Young’s Modulus is determined by the stress strain expression. The modulus of elasticity is varied throughout to evaluate the non-linear response of concrete structure at a constant load. The modeling of structure is done in STAAD PRO Vi8 software. In this study, single storey-single bay frame is modeled which is subjected to dead load and uniform loads, has been considered for the non-linear response of concrete structures. A structural element such as Column is used for evaluation of the non-linear response of concrete material. From this, deflection of the column element is carried out by using STAAD PRO software with different initial tangent modulus of elasticity at a constant loading.
Dislocation and twin substructure evolution during strain hardening of an Fe–22 wt.% Mn–0.6 wt.% C TWIP steel observed by electron channeling contrast imaging
Numerical Study of Star Anchor Plate Embedded in Cohesive SoilIJERA Editor
Indonesia as an archipelago country has a very long coastline about 90.000 kms. Specifically for shore and offshore, there are many buildings utilizing structures including floating deck, mooring dolphin, offshore platforms etc. Those requires a solution to maintain the stability of the structures due to the vertical movement of tides and horizontal movement of currents, wind and waves. To maintain the stability due to buoyant force, structure of anchors are needed. Various types of the anchor have been widely used such as drag, helical, anchor plate circular shape and square. This study aims to do the development of new modifications of a plate anchor type star with 4 leaves with an area of a fixed and diameter equivalent different on any variations. Ultimate pullout capacity was obtained by using numerical geomechanics analysis within finite difference method. A perfectly plastic soil model was used with a tresca yield criterion. Results are presented including break-out factors based on various anchor shapes and embedment depth. Our findings are also compared with previous numerical and empirical solutions.
Investigation of the Behaviour for Reinforced Concrete Beam Using Non Linear...IJMER
This study presents theoretical investigation that reinforced concrete and composite
construction might be suitably combined to give a new structural material : composite reinforced
concrete. To study theoretically the composite beam, non-linear three-dimensional finite elements
have been used to analyze the tested beam.
The 8-node brick elements in (ANSYS) are used to represent the concrete, the steel bars are modelled
as discrete axial members connected with concrete elements at shared nodes assuming perfect bond
between the concrete and the steel. The results obtained by finite element solution showed good
agreement with experimental results.
The main objective of the present investigation is to carry out a nonlinear analysis of reinforced
concrete beams resting on elastic foundation. Material nonlinearities due to cracking of concrete,
plastic flow, crushing of concrete and yielding of reinforcement are considered. Foundation
representation is assumed linear using Winkler model.
The reinforced concrete beam is modelled by using three dimensional finite elements with steel bars
as smeared layers. The examples have been chosen in order to demonstrate the applicability of the
modified computer program (Dynamic Analysis of Reinforced Concrete Beams on Elastic
Foundations DARCEF ) by comparing the predicted behaviour with that from other experimental and
analytical observations. The program modified in the present research work is capable of simulating
the behaviour of reinforced concrete beams resting of Winkler foundation and subjected to different
types of loading. The program solutions obtained for different reinforced concrete beams resting on
elastic foundations are in good agreement with the available results. Maximum percentage difference
in deflection is 15 %
seismic response of multi storey building equipped with steel bracingINFOGAIN PUBLICATION
Steel bracing has proven to be one of the most effective systems in resisting lateral loads. Although its use to upgrade the lateral load capacity of existing Reinforced Concrete (RC) frames has been the subject of numerous studies, guidelines for its use in newly constructed RC frames still need to be developed. In this paper the study reveals that seismic performance of moment resisting RC frames with different patterns of bracing system. The three different types of bracings were used i.e. X - bracing system, V - bracing system and Inverted V - bracing system. This arrangement helped in reducing the structural response (i.e. displacement, interstorey drift, Shear Forces & Bending Moments) of the designed building structure. An (G+6) storey building was modelled and designed as per the code provisions of IS-1893:2002. And linear analysis is been carried out in the global X direction. The analysis was conducted with a view of accessing the seismic elastic performance of the building structure.
The foremost by-product of this paper is the automation of geological undertakings, for instance, dealing
with exceptionally thin sections of rocks that were subjected to deformation alongside finite steps of time
which can be recorded in video for later analysis using image processing and numerical analysis
procedures. Markers are used in order to trace gradients of deformation over a sample and study other
mechanical properties. Image processing and video sequence analysis can be a very powerful investigation
tool and this paper shows preliminary results from its use on microtectonics. The proposed algorithm is a
combination of two well-known approaches: feature extraction and block matching.
Programmable assembly of bi walled nonuniform beams concept, modeling and app...TalalSalem5
Postbuckling structural instabilities has been shown to have useful mechanical characteristics such as well deformation resistance and recovery. However, the difficulties in control and programmability, due to the complex interconnected sensitivities to geometric and material properties, severely hinder the phe- nomenon use in multifunctional structural applications. In this paper, we propose a concept of nonuni- form beam assembly to increase the the controllability of the postbuckling response. Bilaterally con- strained, nonuniform beams are theoretically investigated to obtain the buckling instability, and the pre- dictions are compared with the experimental and numerical results with satisfactory agreements. Para- metric studies are carried out to demonstrate the tunability of the reported beam assembly with respect to the geometric properties and material parameters (i.e., Young’s modulus) of the nonuniform beams. Fi- nally, the use of the proposed beam assembly method is investigated for novel applications as mechanical triggers and deformation detectors. This study demonstrates an exciting approach to tune the mechani- cal characteristics of engineered assembly structures for novel applications, such as material embedded mechanical sensing.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Seismic Vulnerability Assessment of Steel Moment Resisting Frame due to Infil...IDES Editor
Steel moment resisting frame with open first storey
(soft storey) is known to perform well compared with the RC
frames during strong earthquake shaking. The presence of
masonry infill wall influences the overall behavior of the
structure when subjected to lateral forces, when masonry infill
are considered to interact with their surrounding frames the
lateral stiffness and lateral load carrying capacity of structure
largely increase. In this paper, the seismic vulnerability of
building with soft storey is shown with an example of G+10
three dimensional (3D) steel frame. The open first storey is
an important functional requirement of almost all the urban
multi-storey buildings, and hence, cannot be eliminated.
Hence some special measures need to be adopted for this
specific situation. The under-lying principle of any solution
to this problem is in increasing the stiffness’s of the first
storey such that the first storey stiffness is at least 50% as
stiff as the second storey, i.e., soft first storeys are to be avoided,
and providing adequate lateral strength in the first storey. In
this paper, stiffness balancing is proposed between the first
and second storey of a steel moment resisting frame building
with open first storey and brick infills as described in models.
A simple example building is analyzed by modeling it with
nine different methods. The stiffness effect on the first storey
is demonstrated through the lateral displacement profile of
the building.
Maahanmuuttajanuorten Helsinki -hankkeen esittely 22.3. Ympäristö ministeriöIikka Lovio
Yksikään palvelukonsepti ei selviä ensimmäisestä kosketuksesta oikeaan asiakkaaseen. Kokemuksia yhteissuunnittelusta Maahanmuuttajanuorten Helsinki -hankkeessa
Dislocation and twin substructure evolution during strain hardening of an Fe–22 wt.% Mn–0.6 wt.% C TWIP steel observed by electron channeling contrast imaging
Numerical Study of Star Anchor Plate Embedded in Cohesive SoilIJERA Editor
Indonesia as an archipelago country has a very long coastline about 90.000 kms. Specifically for shore and offshore, there are many buildings utilizing structures including floating deck, mooring dolphin, offshore platforms etc. Those requires a solution to maintain the stability of the structures due to the vertical movement of tides and horizontal movement of currents, wind and waves. To maintain the stability due to buoyant force, structure of anchors are needed. Various types of the anchor have been widely used such as drag, helical, anchor plate circular shape and square. This study aims to do the development of new modifications of a plate anchor type star with 4 leaves with an area of a fixed and diameter equivalent different on any variations. Ultimate pullout capacity was obtained by using numerical geomechanics analysis within finite difference method. A perfectly plastic soil model was used with a tresca yield criterion. Results are presented including break-out factors based on various anchor shapes and embedment depth. Our findings are also compared with previous numerical and empirical solutions.
Investigation of the Behaviour for Reinforced Concrete Beam Using Non Linear...IJMER
This study presents theoretical investigation that reinforced concrete and composite
construction might be suitably combined to give a new structural material : composite reinforced
concrete. To study theoretically the composite beam, non-linear three-dimensional finite elements
have been used to analyze the tested beam.
The 8-node brick elements in (ANSYS) are used to represent the concrete, the steel bars are modelled
as discrete axial members connected with concrete elements at shared nodes assuming perfect bond
between the concrete and the steel. The results obtained by finite element solution showed good
agreement with experimental results.
The main objective of the present investigation is to carry out a nonlinear analysis of reinforced
concrete beams resting on elastic foundation. Material nonlinearities due to cracking of concrete,
plastic flow, crushing of concrete and yielding of reinforcement are considered. Foundation
representation is assumed linear using Winkler model.
The reinforced concrete beam is modelled by using three dimensional finite elements with steel bars
as smeared layers. The examples have been chosen in order to demonstrate the applicability of the
modified computer program (Dynamic Analysis of Reinforced Concrete Beams on Elastic
Foundations DARCEF ) by comparing the predicted behaviour with that from other experimental and
analytical observations. The program modified in the present research work is capable of simulating
the behaviour of reinforced concrete beams resting of Winkler foundation and subjected to different
types of loading. The program solutions obtained for different reinforced concrete beams resting on
elastic foundations are in good agreement with the available results. Maximum percentage difference
in deflection is 15 %
seismic response of multi storey building equipped with steel bracingINFOGAIN PUBLICATION
Steel bracing has proven to be one of the most effective systems in resisting lateral loads. Although its use to upgrade the lateral load capacity of existing Reinforced Concrete (RC) frames has been the subject of numerous studies, guidelines for its use in newly constructed RC frames still need to be developed. In this paper the study reveals that seismic performance of moment resisting RC frames with different patterns of bracing system. The three different types of bracings were used i.e. X - bracing system, V - bracing system and Inverted V - bracing system. This arrangement helped in reducing the structural response (i.e. displacement, interstorey drift, Shear Forces & Bending Moments) of the designed building structure. An (G+6) storey building was modelled and designed as per the code provisions of IS-1893:2002. And linear analysis is been carried out in the global X direction. The analysis was conducted with a view of accessing the seismic elastic performance of the building structure.
The foremost by-product of this paper is the automation of geological undertakings, for instance, dealing
with exceptionally thin sections of rocks that were subjected to deformation alongside finite steps of time
which can be recorded in video for later analysis using image processing and numerical analysis
procedures. Markers are used in order to trace gradients of deformation over a sample and study other
mechanical properties. Image processing and video sequence analysis can be a very powerful investigation
tool and this paper shows preliminary results from its use on microtectonics. The proposed algorithm is a
combination of two well-known approaches: feature extraction and block matching.
Programmable assembly of bi walled nonuniform beams concept, modeling and app...TalalSalem5
Postbuckling structural instabilities has been shown to have useful mechanical characteristics such as well deformation resistance and recovery. However, the difficulties in control and programmability, due to the complex interconnected sensitivities to geometric and material properties, severely hinder the phe- nomenon use in multifunctional structural applications. In this paper, we propose a concept of nonuni- form beam assembly to increase the the controllability of the postbuckling response. Bilaterally con- strained, nonuniform beams are theoretically investigated to obtain the buckling instability, and the pre- dictions are compared with the experimental and numerical results with satisfactory agreements. Para- metric studies are carried out to demonstrate the tunability of the reported beam assembly with respect to the geometric properties and material parameters (i.e., Young’s modulus) of the nonuniform beams. Fi- nally, the use of the proposed beam assembly method is investigated for novel applications as mechanical triggers and deformation detectors. This study demonstrates an exciting approach to tune the mechani- cal characteristics of engineered assembly structures for novel applications, such as material embedded mechanical sensing.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Seismic Vulnerability Assessment of Steel Moment Resisting Frame due to Infil...IDES Editor
Steel moment resisting frame with open first storey
(soft storey) is known to perform well compared with the RC
frames during strong earthquake shaking. The presence of
masonry infill wall influences the overall behavior of the
structure when subjected to lateral forces, when masonry infill
are considered to interact with their surrounding frames the
lateral stiffness and lateral load carrying capacity of structure
largely increase. In this paper, the seismic vulnerability of
building with soft storey is shown with an example of G+10
three dimensional (3D) steel frame. The open first storey is
an important functional requirement of almost all the urban
multi-storey buildings, and hence, cannot be eliminated.
Hence some special measures need to be adopted for this
specific situation. The under-lying principle of any solution
to this problem is in increasing the stiffness’s of the first
storey such that the first storey stiffness is at least 50% as
stiff as the second storey, i.e., soft first storeys are to be avoided,
and providing adequate lateral strength in the first storey. In
this paper, stiffness balancing is proposed between the first
and second storey of a steel moment resisting frame building
with open first storey and brick infills as described in models.
A simple example building is analyzed by modeling it with
nine different methods. The stiffness effect on the first storey
is demonstrated through the lateral displacement profile of
the building.
Maahanmuuttajanuorten Helsinki -hankkeen esittely 22.3. Ympäristö ministeriöIikka Lovio
Yksikään palvelukonsepti ei selviä ensimmäisestä kosketuksesta oikeaan asiakkaaseen. Kokemuksia yhteissuunnittelusta Maahanmuuttajanuorten Helsinki -hankkeessa
Seismic Response of Non-Structural Element Placed on Single Story Two-Way Asy...IJERA Editor
The seismic response of non-structural element placed on single-storey, two-way asymmetric building under
bi-directional excitations is investigated. The response is obtained by numerically solving the governing
equations of motion. The seismic response of the system and non-structural element is obtained by numerically
solving the equations of motion using state-space method under different system parameters. The comparative
performance is investigated of non-structural element placed at different places on single story asymmetric
building and finding a best place for survival during earthquake. It is found that non-structural element at
flexible edge along Y- direction gives less response of displacement and acceleration. So, non-structural
element placed at flexible edge along Y- direction on asymmetric SDOF system performs better in earthquake
than at other places.
APPLICATION OF TAGUCHI METHOD FOR PARAMETRIC STUDIES OF A FUNNEL SHAPED STRUC...ijmech
In this paper, attempt has been made to minimize sound reflection from the wall by using Taguchi’s method and to find optimal structure for the suggested test-section inside the cavitation tunnel. The suggested structure which was added to the test-section is funnel-shaped with a performance like a check valve. In order to obtain approximate values of five independent parameters, three levels were taken into account for each parameter. By combining parameters of different levels, 27 tests were designed using Taguchi’s method and Minitab Software. Different acoustic analyses were conducted in COMSOL Multiphysics software, and defined parameter of general reflection coefficient was obtained for 21 observer points. Applying the general reflection coefficients to Minitab Software and drawing the SNR graph, approximate values of the parameters were obtained. However, these values did not produce enough accuracy to design the optimal structure. For this reason, five levels around optimal values, obtained from the previous analysis, were considered for each parameter. Same steps were repeated again for the parameters at five
levels and optimal values were obtained. Optimal structure was modelled and analyzed. Consequently, appropriate defined parameters of general and local reflection coefficients were extracted which represented an optimal structure for the intended test section.
Experimental in Structural Dynamics Base Isolation System Modellingijtsrd
This project is to understand and have the ability to perform dynamic test. Furthermore in this project, the author can investigate how the dynamics of a multistory building is modified by base isolation. The dynamic properties are also very important for the dynamics analysis of the structure. The main task in this project is to determine the dynamic behavior of a 5 storey steel structure model with base isolation system and without base isolation system by experimentally and numerically. In this section the author examine the vibration properties, natural modes and the earthquake response of two systems 1 Five storey building on a fixed base, 2 Same five storey building supported on the isolation system. In this whole project, the following tasks have to do. First the five storey structure has to model in SAP2000 numerically. After that by the definition of reference sensor positions, sensor setups and excitation locations, the first experimental modal test has planned to do. Then the data assessments have to do like model identification, comparison of test results with the numerical model and also simulate the tests numerically. Again it needs to modify the structure in the numerical model and analyzed it again. In the second test, the system has to prepare with base isolation system. There also have to do second data assessments like model identification, comparison of test results with the numerical model with respect to base isolation system and braced system. Since the dynamic behavior of a linearly behaving structure can be described by its modal parameters natural frequencies, mode shapes, modal damping it is important to carry out tests to identify these parameters. From a numerical analysis study, how response of the building with proposed isolation system under multi direction excitation is then presented followed by the conclusion. Khin Thanda Htun | Kyaw Kaung Cho ""Experimental in Structural Dynamics (Base Isolation System: Modelling)"" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-3 , April 2019, URL: https://www.ijtsrd.com/papers/ijtsrd21704.pdf
Paper URL: https://www.ijtsrd.com/engineering/civil-engineering/21704/experimental-in-structural-dynamics--base-isolation-system-modelling/khin-thanda-htun
SEISMIC MITIGATION OF TWIN TOWER STRUCTURES USING AN ISOLATED CORRIDORharshilshah546931
The analytical expression of connected structures subjected to earthquake ground motions are derived and solve using step-by-step procedures. The seismic response of connected twin towers is compared with those of un-connected structures. It is
observed that the base isolated sky corridor reduces displacement demand, base shear and absolute acceleration significantly.
Rutherford Backscattering Spectrometry: A Laboratory Didactic Path About the ...SEENET-MTP
The SEENET-MTP Seminar: Trends in Modern Physics
19–21 August 2011, Niš, Serbia
Talk by Frederico Corni, Faculty of Education, University of Modena аnd Reggio Emilia, Italy
This paper addresses the fracture toughness ( ), or also known as critical stress intensity Factor, according to
conditions of Lineal Elastic Fracture Mechanics (LEFM). The characterization of the mechanical properties in
tensile and fracture toughness of structural steel pipes API-5L used in hydrocarbons transportation was
performed. For fracture toughness, the material was tested through fatigue crack propagation on standardized
compact specimen (CT) according to ASTM E-399 norm. A thickness (B) equal to and a crack size (a) equal
to 0.5w were used. With the porpoise of establishing the adequate conditions at the crack tip, the specimens were
subjected to fatigue pre-cracking by application of repeated cycles of load in tensile-tensile and constant load
amplitude with a load ratio of R = 0.1. The experimental Compliance method was used based on data obtained
from load vs. Crack Mouth Opening Displacement (CMOD). The results show a Stress Intensity factor of 35.88
MPa√m for a 25 mm crack size specimen. The device used for testing is a MTS-810 machine with capacity of
100KN and 6 kHz sampling rate, which meets the conditions of the ASTM E-399 standard. The cracking
susceptibility of steel is influenced by the size, morphology and distribution of non-metallic inclusions,
thermochemical interaction with the environment and microstructure.
Inelastic Period of Multi Degree of Freedom System Estimation using Wavelet T...
1683
1. 1683
ANALYSIS OF 3-D VIBRATIONS OF THE BASE ISOLATED SCHOOL BUILDING
"PESTALOZZI" BY ANALYTICAL AND EXPERIMENTAL APPROACH
Mihail A GAREVSKI1, James M KELLY2 And Nikola V ZISI3
SUMMARY
The results obtained by experimental dynamic ambient and forced vibration tests, as well as from the 3-D finite
element analyses on a base-isolated structure are presented and discussed in this paper. Since the isolators of the
structure were placed 30 years ago, one of the goals of these investigations was to discover whether the isolators
have been affected by aging, i.e., whether there has been a change of the dynamic characteristics of the structure.
First of all, the school building is described and the characteristics of the bearings are given. Then, the results
obtained by means of the ambient and forced vibration technique are presented. Based on these tests, some of the
necessary characteristics of the isolators to be used for formulation of the 3-D mathematical model of the school
were obtained.
Described is the mathematical model that is used in the analyses for obtaining of the fundamental frequencies
and mode shapes (fixed and isolated model). The results from these analyses are also presented in this text.
Finally, the results obtained analytically and experimentally are analysed and discussed.
INTRODUCTION
The primary school "Pestalozzi" in Skopje, built in 1969, is the first building in the world for which natural
rubber isolators were used for its protection against strong earthquakes. [4,5,6] Since the isolators on which the
school is placed are more than 30 years old, a project is currently being carried out jointly by IZIIS (Institute of
Earthquake Engineering and Engineering Seismology, University "St. Cyril and Methodius", Skopje, Republic of
Macedonia) and EERC (Earthquake Engineering Research Center at the University of California at Berkeley) to
evaluate the state of the isolators after passing of so many years. [2]
The behaviour of the school building under the effect of strong earthquakes shall be analysed by using a 3-D
mathematical model that shall include all the present characteristics of the isolators. To accurately formulate this
model, it is necessary to consider the effect of aging of the isolators, i.e., define their present stiffness
characteristics and equivalent damping. For the purpose of defining the mentioned characteristics, experimental
laboratory tests of two isolators taken from the foundation of the school building "Pestalozzi" are planned to be
performed. [2] To define the dynamic characteristics, in-situ, ambient and forced vibration tests were performed
obtaining thus the fundamental and some of the higher frequencies and the corresponding mode shapes for the
three orthogonal directions of the school building. [3,4] Two torsional modes of vibration and equivalent
damping for all the measured mode shapes were also defined.
A 3-D mathematical model of the school building and the bearings was formulated in order to analytically define
the dynamic characteristics of the structure. The discretization of the structure was done by using shell finite
elements, while the bearings were modelled with spring elements. In addition to the fundamental shapes of
vibration, higher vibration modes were also obtained analytically. Comparison between the experimental and
analytical results was done.
1
Institute of Earthquake Engineering and Engineering Seismology, University "St. Cyril & Methodius", Skopje, R. Macedonia
2
Earthquake Engineering Research Center, University of California at Berkeley, California, U.S.A.
3
Institute of Earthquake Engineering and Engineering Seismology, University "St. Cyril & Methodius", Skopje, R. Macedonia
2. The results from the ambient and forced vibration tests, as well as from the 3-D finite element analyses of the
school building "Pestalozzi", are given in the subsequent text.
DESRIPTION OF THE BUILDING
The building which is subject of the investigations, i.e., the primary school "J.H. Pestalozzi" in Skopje was
donated to Skopje by the Swiss Government after the catastrophic earthquake of July 26, 1963. The school
building consists of several units of different number of stories and outline. The base isolation system has been
applied only for the main school building, while the other units are founded in the classical way.
The main school building consists of a ground floor and two stories. The proportions of the stricture at plan are
11.0 m / 61.5 m, while its height is 10.0 m. It represents a reinforced concrete box system. The bearing wall
system is composed of shear walls with a thickness of 0.18 m, while the floor slabs are 0.20 m thick. The
building has a strip foundation forming a beam grid, which is sufficiently rigid to sustain all the effects from the
upper structure without heavier deformations. Along the edges of the building, there is a seismic gap with a
width of 0.3 m. The gap is covered with reinforced concrete plates.
The structure is base isolated by its placement on special rubber bearings incorporated between the foundation
structure and the first floor slab. (Fig.1) [8] There are a total of 54 bearings made of natural rubber, with a square
shape, a side of 0.7 m and a height of 0.35 m. Each bearing transfers an axial force amounting to approximately
455 kN. The Swiss firm HUBER-SUHNER from Zurich produced the rubber bearings. The isolators do not
contain reinforcing steel plates. They are fabricated by gluing together several rubber layers. The vertical
stiffness of such bearings is therefore not much greater than the horizontal one. In addition to the negative effect
of the low vertical stiffness of the bearings on the possible rocking motion, there is another disadvantage of these
bearings, which is the occurrence of large lateral deformations of the rubber bearings due to dead load effects.
[1]
Figure 1. Rubber bearings placed between the strip foundation and the building
DYNAMIC TESTING OF THE PRIMARY SCHOOL "J.H. PESTALOZZI"
Dynamic testing of the main (isolated) school building was performed by application of two independent testing
methods:
2 1683
3. Ambient vibration method - This method was used for fast obtaining of preliminary results on the dynamic
characteristics - resonant frequencies and mode shapes of vibration of the tested structure. The vertical vibration
of the structure obtained by this method was used as a referent one since the vibrators used for the forced
vibration tests cannot induce vertical displacements.
Forced vibration method - This method was applied to define some characteristic vibrations of the structure in
both horizontal directions as well as the torsional one.
To define the damping coefficients, two methods were used: (1) half-power bandwidth (frequency-response)
method and (2) logarithmic decrement (time-response) method.
The dynamic characteristics of the building were obtained for the state of reinforced concrete plates being
removed from the seismic gap and free motion of the isolated building in all directions was enabled. [3,4]
Fig. 2 displays the plan of the second storey of the structure with marked measuring points and position of
vibration exciters by which it was excited during the forced vibration tests.
Figure 2. Plan of the second storey of the tested structure with presentation of measuring points and position of
the two vibration exciters
Results From the Tests Performed by Applying the Ambient Vibration Method
To define the resonant frequencies of the structure in both orthogonal directions - transverse (N-S) and
longitudinal (E-W), and the vertical one, four Range Seismometers, Model SS-1 produced by Kinemetrics from
USA were used as sensors. Seismometer was placed in the central part of the structure, at the level of the second
storey, at point "C" (Fig. 2). Seismometers were placed at the ends of the structure (measuring points 1 and 5)
and also at the level of the second storey to define the resonant frequencies of the torsional vibration. The
Fourier amplitude spectra corresponding to the torsional vibrations of the structure were obtained by combining
the signals from both seismometers.
Fig. 3 shows the Fourier amplitude spectra recorded on the structure in the corresponding directions of vibrations
from which the resonant frequencies were defined. For such defined resonant frequencies of the structure, the
corresponding mode shapes were obtained. However, these and the mode shapes obtained by other
measurements are not presented in this paper due to lack of space.
3 1683
4. Figure 3. Fourier amplitude spectra on the isolated building recorded with the ambient vibration method
Results From Tests Performed by Using the Forced Vibration Method
In the process of testing, the resonant frequencies of the structure were first of all defined for both orthogonal
directions (N- S) and (E-W) and then for torsion. The structural response to the generated excitation, while
defining the resonant frequencies for the N-S and E-W directions, was recorded at several measuring points. The
recorded responses at the points located in the midst of the structure (point "C" or point "3") were considered
referent. The referent point for definition of the torsional resonant frequencies was point "5" on the east side of
the structure. Based on the recorded amplitudes of the response of the structure to the generated excitations, the
corresponding resonant frequency curves were established. (Fig. 4) Certain tests performed for definition of the
same frequency were carried out by different excitation forces for the purpose of evaluating the relation between
modification of the resonant frequency and the excitation intensity.
Figure 4. Resonant curves of the structural response obtained with the force excitation method
4 1683
5. Due to the flexibility of the isolators, some of the mode shapes could quite well be excited and even visually
observed. Therefore, apart from using accelerometers, which is the usual practice in performing these tests,
displacement-meters (LVDT-s) were also used.
The frequency curves presented in Fig. 4 were established based on the recorded amplitudes of structural
response to the generated excitations.
For such defined resonant frequencies, the corresponding mode shapes of vibration were also recorded.
3-D EIGENPAIR ANALYSIS
For both cases of support of the school building, the eigen values and the eigen vectors were computed. First, the
fundamental vibrations of the school fixed at its base were computed. Then, the fundamental frequencies and the
corresponding mode shapes of the school building placed on rubber bearings were obtained. The finite elements
mesh for both analyses was the same.
Description of the Finite Element Model
The analyses of the mathematical model of the "Pestalozzi" primary school building has been done by means of
the SAP2000 computer programme. [7] The structure itself has been modelled by a total number of 7189
"SHELL" elements. Due to the size of the model, the individual structural elements: floor slabs, bearing walls in
both orthogonal directions, staircase slabs, parapet walls and alike have been modelled separately. Then the
structure has been assembled as a whole by means of "welding" of the joints that share the same location. The
rubber bearings supporting the structure have been modelled by a total of 54 "NLLINK" elements. These have
been taken as one-joint grounded spring, and they are of the type of biaxial base isolators. During the analysis of
this model, it has been necessary to solve 43596 equilibrium equations.
Such a refined model (with a large number of finite elements) was used because the generation of the mesh was
not time consuming, as were also the analyses. Such a model is necessary for further analyses when the stress
state in the walls is to be analysed.
Analysis of the School Building Model Fixed at its Base
This analysis was necessary to be performed because of two reasons: (1) the fundamental frequencies of the
fixed structure had to prove whether the base isolation of the structure is justified; (2) this analysis had to prove
whether rigid-structure approximation is possible for the performance of a simpler analysis.
Table 1 shows the eigen frequencies of the first fundamental modes of vibration obtained by this analysis.
Analysis of the School Building Model on Rubber Isolators
Precise determination of stiffness characteristics in lateral and vertical direction was not possible at present since
force-displacement hysteretic loops of the installed rubber isolators were not available. Therefore, the
approximate values of stiffness characteristics of isolators were obtained via the measured values of fundamental
frequencies by using the following basic formula:
54
∑k
i =1
Bi = ω B M total
2
where: k_Bi - stiffness of i-th base isolator, ω_B - measured circular frequency of the base isolated building, and
M_total - total mass of building structure and base isolators.
5 1683
6. It is assumed that: (1) the structure is rigid (the fixed-base analysis (f_N-S = 12.97 Hz; f_E-W = 8.32 Hz did
confirm this assumption), and (2) the mass is known (it can be computed from the given geometry and the bulk
density of the concrete). However, it should be noted that the computation of the lateral stiffness in this way is
partially compromised since the fundamental modes of vibration in both orthogonal directions are not purely
translational, but there is also a rocking motion due to the low vertical stiffness of the isolators.
Table 1 shows the eigen frequencies of the first fundamental modes of vibration, while the characteristics mode
shapes are presented in Fig 5.
a) Mode: 1, Period: 1.408 s, Frequency: 0.710 Hz, Dominant direction: N-S (transversal)
b) Mode: 2, Period: 1.167 s, Frequency: 0.857 Hz, Dominant direction: E-W (longitudinal)
c) Mode: 3, Period: 1.133 s, Frequency: 0.882 Hz, Dominant direction: torsional
Fig 5 Characteristics mode shapes of the base isolated building model
6 1683
7. DISCUSSION OF THE RESULTS OBTAINED THROUGH THE EXPERIMENTAL
MEASUREMENTS AND ANALYTICAL PROCEDURES
Based on the data obtained from the performed testing of the structure, the following is concluded:
The values of the frequencies of the fundamental vibration modes in certain directions when the plates covering
the seismic gap are removed are: for transverse direction (N-S): f_1f = 0.76 Hz (forced vibration tests) and
f_1a = 0.96 Hz (ambient vibration tests); for torsion: f_2f = 0.84 Hz (forced vibration tests) and f_2a = 1.04 Hz
(ambient vibration tests); for the longitudinal direction (E-W): f_3f = 0.88 Hz (forced vibration tests) and
f_3a = 1.28 Hz (ambient vibration tests) and for vertical direction: f_5a = 2.56 Hz (ambient vibration tests).
Apart from the fundamental vibration modes, some of the higher modes were recorded. The frequency of
f_4f = 2.08 Hz represents the second natural frequency of the structure in the (N-S) direction, while f_6f= 3.20
Hz represents the second natural frequency at torsional excitation. The second natural frequency of the structure
in the E-W direction is very close (almost equal) to the corresponding frequency at torsional excitation
amounting to f = 3.20 Hz, i.e., f_7f= 3.28 Hz.
The recorded higher frequencies of f_8f = 3.44 Hz, f_9f= 5.28 Hz, f_12f = 5.92 Hz in the transverse direction
and f_10f = 5.28 Hz in the longitudinal direction, i.e., f_11f = 5.52 Hz at torsional vibrations are associated with
some of the higher mode shapes of vibration of the structure.
The frequencies and the corresponding damping measured by applying both methods are presented in Table 1.
Table 1
Mode Experimental Testing Analytical
No. Direction Ambient Forced vibration Fix Base Isolated
f f Damping Damping f f
[Hz] [Hz] [%] hp* [%] ld** [Hz] [Hz]
1 first (N-S) 0.96 0.76 3.8 3.5 12.97 0.71
2 first (E-W) 1.28 0.88 7.3 6.3 8.32 0.86
3 torsion 1.04 0.84 5.4 3.0 - 0.88
4 vertical 2.56 - - - - 1.87
*Half-power bandwidth method **Logarithmic decrement method
Analysing the recorded mode shapes, it can be said that the translatory components dominate over the first two
modes of vibration of the school building (f_1f = 0.76 Hz, f_2f = 0.88 Hz).
Characteristic for the second vibration modes in E-W direction (f_4f = 2.08 Hz) and N-S direction (f_7f = 3.28
Hz) is the rocking motion which is more pronounced for the mode with a frequency of f_4f = 2.08 Hz.
The experimentally measured mode shapes and those obtained analytically clearly point to the fact that the
modes, in addition to the translation component, contain also the component of a rocking motion.
The complex motions of the mode shapes result from the low vertical stiffness of the rubber bearings.
Since the fundamental modes for the two horizontal directions are not purely translatory (there are rotation
components), their frequencies are not identical. There occurs a difference of 15.8% in the values of their
frequencies.
The obtained results on damping presented in Table 1 point to similar damping obtained by both methods. The
damping values lead to the conclusion that the internal damping of the bearing is small since the coefficients of
viscous damping for the fundamental vibration modes are 3.5%, 3% and 6.3% of the critical one in the N-S and
E-W directions as well as torsion respectively.
The fundamental frequencies of the fixed base model do justify the performed isolation of the building.
However, the first modes of vibration for both orthogonal directions f_N-S = 0.76 Hz; f_E-W = 0.88 Hz
7 1683
8. obtained experimentally are far above the minimum frequency of f = 0.5 Hz which is necessary for the isolators
in order that they be efficient.
The mathematical discretization and analysis of the isolated structure has successfully been done since there is a
good correlation between the analytical and experimental values of the fundamental frequencies and their mode
shapes. However, evaluation of the efficiency of the base isolation could be made in the final phase of this
project when two isolators shall be taken off and the hysteresis curves obtained in laboratory conditions. The
final analyses shall be performed by use of these curves and shall lead to obtaining of the base shear and the
maximum displacements. From the laboratory testing on the taken off bearings and the analyses, one could
further conclude whether the old bearings are necessary to be replaced by new ones or whether it is only
necessary to add dampers for dissipation of the input energy from the earthquake.
ACKNOWLEDGMENT
This paper is based on the investigations sponsored by the Macedonian – US Joint Fund in cooperation with the
Macedonian Ministry of Science and US - NIST under project number 056/600. The authors are indebted to
these two institutions for the correct evaluation of the necessity for these investigations.
REFERENCES
1. Bridgestone corporation, 1991. Rubber technology for seismic isolation. Proc., 11th international conf.
on struc. mech. in reactor technology: 45-56, Tokyo, Japan.
2. Garevski, M. & Kelly, M. J., 1996. Evaluation of the proper functioning of the rubber isolators of the
primary school Pestalozzi in Skopje under strong earthquake. U.S.- Macedonian science and technology
program-project proposal.
3. Garevski, M., Kelly, M. J. & Bojadziev, M.,1998. Evaluation of the proper functioning of the rubber
isolators of the primary school Pestalozzi in Skopje under strong earthquake: part I- Full-scale dynamic testing
of the first rubber base-isolated building in the world. Report IZIIS.
4. Garevski, M., Kelly, J. M. & Bojadziev, M., 1998. Experimental dynamic tests on the first structure in
the world isolated with rubber bearings. 11th European Conference on Earthquake Engineering, Paris, France
5. Izumi, M., 1988. Base isolation and passive seismic response control. Proc., 9th world conference on
earthquake engineering, vol. VII: 386-396,Tokyo-Kyoto, Japan,.
6. Kelly, J.M., 1981. The Development of base isolation for the seismic protection of structures. Report
No. UCB/EERC-81/01, Earthquake Engineering Research Center, University of California, Berkeley, California.
7. SAP2000 Integrated Finite Element Analysis and Design of Structures; Analysis Reference, Vol. 1 &
2; Computers and Structures, Inc; Berkeley, California, USA
8. Staudacher, K., 1982. The Swiss full base isolation system (3D) for extreme earthquake safety of
structures. Proc. of the 1982 convention of the structural engineering association of California, Sacramento,
California.
8 1683