Experimental Evaluation of Fatigue Performance of Steel Grid Composite Deck J...IJERDJOURNAL
ABSTRACT:- The steel grid composite deck is a composite structure made of a concrete slab disposed over a steel grid. The joints of the deck segments precast with regular width can be designed by means of lap-spliced rebar or mechanical connection composed of concrete shear key and bolts. This study intends to evaluate comparatively the fatigue performance with respect to the type of joint based upon the results of fatigue tests conducted on deck specimens equipped with such joints. The evaluation reveals that there is practically no change in the stiffness regardless of the type of joint even after 2 million loading cycles and that the safety and serviceability are secured under cyclic loading since the maximum crack widths remained below the allowable values.
This is my M.Tech Project presentation. The project was carried out at R.V College of Engineering and B.M.S College of Engineering, Bangalore. In this project, the axial load carrying capacity of CFST Columns was studied and the experimental results were compared with Eurocode-4 and AISC-LRFD-2005. The flexural capacity of CFST frames was also carried out.
This paper presents a study on flexural behaviour of concrete filled steel tube based on the former
work carried out by Manojkumar. An ANSYS model is developed that can predict the behaviour of concrete
filled steel tube to determine moment carrying capacity at ultimate point for beam Concrete filled steel tube
beams are studied and verified by the finite element program ANSYS against experimental data. The Main
parameters affecting the behaviour and strength of concrete filled beams are geometrical parameters, material
nonlinearities, loading, boundary conditions and degree of concrete confinement. To account for all these
properties ANSYS model is developed. The main parameters varied in analysis study are D/t ratio,
characteristic strength of infilled concrete. The proposed model predicts ultimate moment capacity for CFT
beams. In the numerical analysis, circular and rectangular CFT cross sections are considered using different
grades of concrete. The predicted values are compared with experimental results. Numerical analysis has
shown that for rectangular CFT’s a good confining effect can be provided. Moment capacity results obtained
from the ANSYS model are compared with the values predicted by Lin Han (2004) and different codes such as
AISC-LRFD (1999) and EC4 (1994).
Behaviour of concrete column reinforced with prefabricated cageashlinvilson
To enhance the structural capacity and constructability of composite columns, a prefabricated cage system (PCS) was developed. By using the prefabricated steel cage, field rebar work is unnecessary, and the self-erectable steel cage can provide sufficient strength and rigidity to support the construction loads of beams and slabs. Nowadays the non-conventional reinforcement system is widely used reinforcement system for RC column reinforcement instead of conventional reinforcement system. In which, a new non-conventional reinforcement system named as Prefabricated Cage System is used recently. PCS is fabricated by perforating hollow steel tubes or steel plates. Various methods could be used to fabricate PCS reinforcement such as punching cutting methods and casting. Here, a comparison of PSC specimen and conventional rebar reinforcement columns are carried out. PCS reinforcement is prefabricated off-site and then placed inside the formwork eliminating the time consuming and costly labor associated with cutting, bending, and tying steel bars in traditional rebar construction. PCS can be used to reinforce almost any kind of concrete member which involves reinforcement and concrete. PCS can be used as the entire or part of the reinforcement in concrete columns one of the major applications of PCS is it’s in axial members, therefore; this study investigates the behavior of PCS reinforced column specimens tested under axial load with conventionally reinforced RC column specimens.
Experimental Evaluation of Fatigue Performance of Steel Grid Composite Deck J...IJERDJOURNAL
ABSTRACT:- The steel grid composite deck is a composite structure made of a concrete slab disposed over a steel grid. The joints of the deck segments precast with regular width can be designed by means of lap-spliced rebar or mechanical connection composed of concrete shear key and bolts. This study intends to evaluate comparatively the fatigue performance with respect to the type of joint based upon the results of fatigue tests conducted on deck specimens equipped with such joints. The evaluation reveals that there is practically no change in the stiffness regardless of the type of joint even after 2 million loading cycles and that the safety and serviceability are secured under cyclic loading since the maximum crack widths remained below the allowable values.
This is my M.Tech Project presentation. The project was carried out at R.V College of Engineering and B.M.S College of Engineering, Bangalore. In this project, the axial load carrying capacity of CFST Columns was studied and the experimental results were compared with Eurocode-4 and AISC-LRFD-2005. The flexural capacity of CFST frames was also carried out.
This paper presents a study on flexural behaviour of concrete filled steel tube based on the former
work carried out by Manojkumar. An ANSYS model is developed that can predict the behaviour of concrete
filled steel tube to determine moment carrying capacity at ultimate point for beam Concrete filled steel tube
beams are studied and verified by the finite element program ANSYS against experimental data. The Main
parameters affecting the behaviour and strength of concrete filled beams are geometrical parameters, material
nonlinearities, loading, boundary conditions and degree of concrete confinement. To account for all these
properties ANSYS model is developed. The main parameters varied in analysis study are D/t ratio,
characteristic strength of infilled concrete. The proposed model predicts ultimate moment capacity for CFT
beams. In the numerical analysis, circular and rectangular CFT cross sections are considered using different
grades of concrete. The predicted values are compared with experimental results. Numerical analysis has
shown that for rectangular CFT’s a good confining effect can be provided. Moment capacity results obtained
from the ANSYS model are compared with the values predicted by Lin Han (2004) and different codes such as
AISC-LRFD (1999) and EC4 (1994).
Behaviour of concrete column reinforced with prefabricated cageashlinvilson
To enhance the structural capacity and constructability of composite columns, a prefabricated cage system (PCS) was developed. By using the prefabricated steel cage, field rebar work is unnecessary, and the self-erectable steel cage can provide sufficient strength and rigidity to support the construction loads of beams and slabs. Nowadays the non-conventional reinforcement system is widely used reinforcement system for RC column reinforcement instead of conventional reinforcement system. In which, a new non-conventional reinforcement system named as Prefabricated Cage System is used recently. PCS is fabricated by perforating hollow steel tubes or steel plates. Various methods could be used to fabricate PCS reinforcement such as punching cutting methods and casting. Here, a comparison of PSC specimen and conventional rebar reinforcement columns are carried out. PCS reinforcement is prefabricated off-site and then placed inside the formwork eliminating the time consuming and costly labor associated with cutting, bending, and tying steel bars in traditional rebar construction. PCS can be used to reinforce almost any kind of concrete member which involves reinforcement and concrete. PCS can be used as the entire or part of the reinforcement in concrete columns one of the major applications of PCS is it’s in axial members, therefore; this study investigates the behavior of PCS reinforced column specimens tested under axial load with conventionally reinforced RC column specimens.
Effect of Caging and Swimmer Bars on Flexural Response of RC Deep BeamsIJERA Editor
Beams with shear span to depth ratio (a/d) less than or equal to 2 are considered as deep beams. They have wide
applications in pile caps, water tanks, shear walls, corbels etc. Their strength is controlled by shear. Swimmer
bars are small inclined bars, whose both ends are bent horizontally and welded to both top and bottom flexural
reinforcement. Swimmer bars forming a plane crack interceptor system is effective in carrying shear. Also, a
reinforcement caging provided at the centre of a simply supported beam is supposed to enhance its flexural
capacity. In this study, an experimental investigation on the flexural response of deep beams reinforced with
caging and swimmer bars is done. Various parameters like ultimate load, deflection and failure modes of
different reinforcement patterns are studied.
Retrofitting of Beam-Column Joint using Carbon Fibre Reinforced Polymer and G...Satyam Vijay Bhosale
Retrofitting of an existing building is immensely essential for the deteriorated and damaged structure in Engineering and Medical fields. It refers to endowing the structure with a service level higher than that initially planned by modifying the structures, not necessarily damage area. Beam-column joints, being the lateral and vertical load transferring connections in reinforced concrete structures are particularly vulnerable to failures and hence the satisfactory performance of these joints is key to control the performance of connecting structural members during any event.
The project involves the study of the load carrying capacity of the beam-column joint after the application of the CFRP (Carbon Fiber Reinforced Polymer) and GFRP (Glass fibre Reinforced Polymer) sheets. Five beam-column joint models were cast out of which one model was the control specimen and others were cast for the purpose of the retrofitting. Four specimens were retrofitted by L-shape and straight configurations. The project focused on the effect of using the CFRP sheets and GFRP sheets for enhancing the strength and ductility of the beam-column joint. The wraps were provided to prevent the shear failure of the beam-column joint. The failure criteria including ultimate capacity, mode of failure, initial stiffness, ductility and developed ultimate strain in the reinforcing steel and respective sheet were considered and then compared.
Numerical modeling on behaviour of reinforced concrete exterior beam column j...eSAT Publishing House
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.
Study of Buckling Restrained Braces in Steel Frame BuildingIJERA Editor
Conventional braces have limited deformation ductility capacity, and exhibit unsymmetrical hysteretic cycles, with marked strength deterioration when loaded in compression. To overcome the above mentioned problems, a new type of brace was developed in Japan called as buckling restrained braces, designated as BRB’s. These braces are designed such that buckling is inhibited to occur, exhibiting adequate behavior and symmetrical hysteretic curves under the action of both tensile and compressive cycles, produced by the action of seismic and wind forces. This paper presents experimental results concerning the lateral load carrying capacity of steel frame model by use of buckling restrained brace. This paper also includes the comparative study of lateral load carrying capacity of frame model for bare frame, frame with Conventional brace and frame with buckling restrained brace.
Capacity of strengthened Reinforced concrete columnsKhaled Mahmoud
this presentation show main points of research focused on the analysis of concrete and steel jackets to get simple equations for design. Therefore, an experimental program consists of twenty columns strengthened with concrete jackets and steel jackets are performed. The results were compared with some of the design equations in available literature. These equations were modified to match the theoretical and experimental results. Recommendations for column behavior after strengthening are presented to help structural engineers to maximize the benefits of strengthening operation.
Lateral Load Analysis of a Building with & Without Knee BracingIJERA Editor
In last decades steel structures has played an important role in construction industry. Providing strength, stability
and ductility are major purposes of seismic design. It is necessary to design a structure to perform well under
seismic loads. Steel braced frame is one of the structural systems used to resist earthquake loads in structures.
Steel bracing is economical, easy to erect, occupies less space and has flexibility to design for meeting the
required strength and stiffness. Bracing can be used as retrofit as well. There are various types of steel bracings
such as Diagonal, X, K, V, inverted V type or chevron and global type concentric bracings. In the present study,
it was shown that modelling of the G+4 steel bare frame with various bracings (X, V, inverted V, and Knee
bracing) by computer software SAP2000 and pushover analysis results are obtained. Comparison between the
seismic parameters such as base shear, roof displacement, time period, storey drift, performance point for steel
bare frame with different bracing patterns are studied. It is found that the X type of steel bracings significantly
contributes to the structural stiffness and reduces the maximum interstate drift of steel building than other
bracing systems.
Castellated beam optimization by using Finite Element Analysis: A Review.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.
System shear connector jakarta digunakan sebagai aplikasi dalam konstruksi bangunan untuk menghasilkan kekuatan coran beton lebih kuat dan stabil sesuai dengan perhitungan engineering civil. Dalam hal ini ada 2 hal perhitungan kekuatan secara umum yaitu kekuatan kelengketan stud pada batang baja sesudah dilas. Dan yang kedua adalah kekuatan stud bolt yang digunakan.
Effect of Caging and Swimmer Bars on Flexural Response of RC Deep BeamsIJERA Editor
Beams with shear span to depth ratio (a/d) less than or equal to 2 are considered as deep beams. They have wide
applications in pile caps, water tanks, shear walls, corbels etc. Their strength is controlled by shear. Swimmer
bars are small inclined bars, whose both ends are bent horizontally and welded to both top and bottom flexural
reinforcement. Swimmer bars forming a plane crack interceptor system is effective in carrying shear. Also, a
reinforcement caging provided at the centre of a simply supported beam is supposed to enhance its flexural
capacity. In this study, an experimental investigation on the flexural response of deep beams reinforced with
caging and swimmer bars is done. Various parameters like ultimate load, deflection and failure modes of
different reinforcement patterns are studied.
Retrofitting of Beam-Column Joint using Carbon Fibre Reinforced Polymer and G...Satyam Vijay Bhosale
Retrofitting of an existing building is immensely essential for the deteriorated and damaged structure in Engineering and Medical fields. It refers to endowing the structure with a service level higher than that initially planned by modifying the structures, not necessarily damage area. Beam-column joints, being the lateral and vertical load transferring connections in reinforced concrete structures are particularly vulnerable to failures and hence the satisfactory performance of these joints is key to control the performance of connecting structural members during any event.
The project involves the study of the load carrying capacity of the beam-column joint after the application of the CFRP (Carbon Fiber Reinforced Polymer) and GFRP (Glass fibre Reinforced Polymer) sheets. Five beam-column joint models were cast out of which one model was the control specimen and others were cast for the purpose of the retrofitting. Four specimens were retrofitted by L-shape and straight configurations. The project focused on the effect of using the CFRP sheets and GFRP sheets for enhancing the strength and ductility of the beam-column joint. The wraps were provided to prevent the shear failure of the beam-column joint. The failure criteria including ultimate capacity, mode of failure, initial stiffness, ductility and developed ultimate strain in the reinforcing steel and respective sheet were considered and then compared.
Numerical modeling on behaviour of reinforced concrete exterior beam column j...eSAT Publishing House
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.
Study of Buckling Restrained Braces in Steel Frame BuildingIJERA Editor
Conventional braces have limited deformation ductility capacity, and exhibit unsymmetrical hysteretic cycles, with marked strength deterioration when loaded in compression. To overcome the above mentioned problems, a new type of brace was developed in Japan called as buckling restrained braces, designated as BRB’s. These braces are designed such that buckling is inhibited to occur, exhibiting adequate behavior and symmetrical hysteretic curves under the action of both tensile and compressive cycles, produced by the action of seismic and wind forces. This paper presents experimental results concerning the lateral load carrying capacity of steel frame model by use of buckling restrained brace. This paper also includes the comparative study of lateral load carrying capacity of frame model for bare frame, frame with Conventional brace and frame with buckling restrained brace.
Capacity of strengthened Reinforced concrete columnsKhaled Mahmoud
this presentation show main points of research focused on the analysis of concrete and steel jackets to get simple equations for design. Therefore, an experimental program consists of twenty columns strengthened with concrete jackets and steel jackets are performed. The results were compared with some of the design equations in available literature. These equations were modified to match the theoretical and experimental results. Recommendations for column behavior after strengthening are presented to help structural engineers to maximize the benefits of strengthening operation.
Lateral Load Analysis of a Building with & Without Knee BracingIJERA Editor
In last decades steel structures has played an important role in construction industry. Providing strength, stability
and ductility are major purposes of seismic design. It is necessary to design a structure to perform well under
seismic loads. Steel braced frame is one of the structural systems used to resist earthquake loads in structures.
Steel bracing is economical, easy to erect, occupies less space and has flexibility to design for meeting the
required strength and stiffness. Bracing can be used as retrofit as well. There are various types of steel bracings
such as Diagonal, X, K, V, inverted V type or chevron and global type concentric bracings. In the present study,
it was shown that modelling of the G+4 steel bare frame with various bracings (X, V, inverted V, and Knee
bracing) by computer software SAP2000 and pushover analysis results are obtained. Comparison between the
seismic parameters such as base shear, roof displacement, time period, storey drift, performance point for steel
bare frame with different bracing patterns are studied. It is found that the X type of steel bracings significantly
contributes to the structural stiffness and reduces the maximum interstate drift of steel building than other
bracing systems.
Castellated beam optimization by using Finite Element Analysis: A Review.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.
System shear connector jakarta digunakan sebagai aplikasi dalam konstruksi bangunan untuk menghasilkan kekuatan coran beton lebih kuat dan stabil sesuai dengan perhitungan engineering civil. Dalam hal ini ada 2 hal perhitungan kekuatan secara umum yaitu kekuatan kelengketan stud pada batang baja sesudah dilas. Dan yang kedua adalah kekuatan stud bolt yang digunakan.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Finite Element Analysis of Cold-formed Steel ConnectionsCSCJournals
This paper presents a thorough investigation into the structural performance of cold-formed steel column base and beam column connections using single lipped C sections with bolted moment connections. Two specimens consisting of a column base and a beam column connection were carried out, and it was found that section failure under flexural buckling was always critical. Moreover, the proposed connections were demonstrated to be structurally efficient attaining moment resistances close to those of the connected sections. In order to examine the structural behavior of the column base and beam column connections, finite element models were established using shell and bar elements to model the sections and the bolted fastenings respectively. Material non-linearity was incorporated, and comparison between the test and the numerical results was presented in details. It was shown that the proposed analysis method was structurally adequate to predict the structural behavior for column base and beam column with similar connection configurations.
Nonlinear fe modelling of anchorage bond in reinforced concreteeSAT Journals
Abstract The transfer of forces from the surrounding concrete to the reinforcing bars in reinforced concrete (RC) can be influenced by several parameters. In this paper an attempt has been made to study the influence of specimen geometry, bar diameter, strength of concrete, lateral confinement and embedment length on the bond properties of concrete. The embedment length of the bar was varied between 50mm and 400mm by varying the diameter of the bar, strength of concrete and lateral confinement. The different bar diameters of 16, 20 and 25mm were selected along with three different concrete strengths of 25, 40 and 65MPa. The specimens with the above parameters were modeled by using a nonlinear finite element analysis package. It has been found that for the same geometry, the specimens with small bond length exhibited high bond strength. With the range of bar diameters considered the bond strength of concrete decreases as the diameter of the bar increases. The splitting failure has been observed in unconfined concrete, while the pullout failure was predominant when the concrete laterally confined. In case of large embedment length, the post peak plateau is prolonged with small diameter bars when compared to the large diameter bars. The descending branch of the bond stress-slip response with large diameter bars has been found to be steep. Keywords: Bond Stress, FE Analysis, Embedment Length, Confinement, Bar Diameter, Pull-out Specimens.
Analytical Investigation on External Beam-Column Joint Using ANSYS By Varying...IJERA Editor
The beam-column joint has been a topic of study for over 30 years now and still there are many things that yet to
be completely understood. The joint was considered to be rigid, however researches have shown that failure may
occur at the joint instead of the beam or column. This study was carried out to determine the effect of the
diameter of longitudinal reinforcement of the beam on the strength, deformation and ductility in the beamcolumn
joint using ANSYS. It was seen that the load carrying capacity and the deformation increases as the
diameter of reinforcement in the beam increases.
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
The Indian economy is classified into different sectors to simplify the analysis and understanding of economic activities. For Class 10, it's essential to grasp the sectors of the Indian economy, understand their characteristics, and recognize their importance. This guide will provide detailed notes on the Sectors of the Indian Economy Class 10, using specific long-tail keywords to enhance comprehension.
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The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
How to Split Bills in the Odoo 17 POS ModuleCeline George
Bills have a main role in point of sale procedure. It will help to track sales, handling payments and giving receipts to customers. Bill splitting also has an important role in POS. For example, If some friends come together for dinner and if they want to divide the bill then it is possible by POS bill splitting. This slide will show how to split bills in odoo 17 POS.
Ethnobotany and Ethnopharmacology:
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Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxEduSkills OECD
Andreas Schleicher presents at the OECD webinar ‘Digital devices in schools: detrimental distraction or secret to success?’ on 27 May 2024. The presentation was based on findings from PISA 2022 results and the webinar helped launch the PISA in Focus ‘Managing screen time: How to protect and equip students against distraction’ https://www.oecd-ilibrary.org/education/managing-screen-time_7c225af4-en and the OECD Education Policy Perspective ‘Students, digital devices and success’ can be found here - https://oe.cd/il/5yV
#2 2006 improving seismic performance of concrete filled tube to base connections (1)
1. Journal of Constructional Steel Research 62 (2006) 1333–1340
www.elsevier.com/locate/jcsr
Improving seismic performance of concrete-filled tube to base connections
H.-L. Hsu∗, H.-W. Lin
Department of Civil Engineering, National Central University, Chung-Li 32054, Taiwan
Received 19 September 2005; accepted 8 February 2006
Abstract
This study is focused on experimentally investigating the relationship between design details and column base performance, such as strength
and rigidity. Results from specimens tested under combined axial and lateral loads were used to define the effectiveness of the base connections.
It was observed from test comparisons that the rigidities of the base connections increased when the embedded depths were increased. It was also
found that the base connections possessed higher stiffness and energy dissipating capability when stiffeners were added to the base connections.
Finally, an empirical expression for base rigidity estimation is proposed for design references.
c 2006 Elsevier Ltd. All rights reserved.
Keywords: Concrete-filled tube; Base connections; Embedded depth; Seismic performance
1. Introduction
Concrete-filled tubes (CFT) possess high compressive
strength and significant ductility and thus are effective
structural forms for earthquake-resistant purposes [1–3].
The significant seismic performance of such designs can
be guaranteed only when adequate design details are
employed. Current studies on the behavior of CFT designs
under earthquake excitation are focused primarily on the
response of CFT members under axial load, bending or a
combination [4–7]. Information on the CFT column to base
design details and the influence of the connection effectiveness
upon the structural performance is still limited.
To fully develop the strength and ductility of CFT
members, the column base must possess sufficient strength
and rigidity to prevent premature failure. It has been
indicated in the investigation report from the 1995 Kobe
earthquake that much structural damage was directly related
to the failure of foundations [8]. Therefore, adequate
recommendations for base connection designs that promote
sustained structural performance are essential to CFT structural
system applications.
In general, column to base connections can be designed
in exposed or embedded forms. Exposed base connection
fabrication is easier than embedded connections. However,
∗ Corresponding author.
exposed connections are less reliable because the connection
rigidity relies solely on the effectiveness of the preset anchor
bolts. In such cases, anchor bolt yielding, as shown in Fig. 1(a),
which is disadvantageous to foundation rigidity, becomes
inevitable. Unless large numbers of anchor bolts and extremely
thick end plates are employed, which should be avoided
when construction costs are a concern, the base connection
effectiveness during earthquakes is susceptible [9,10].
For embedded base connections, connection rigidities can be
improved by the additional resistance of the concrete within the
embedded depth. Although the high stress at the anchor bolts
can be alleviated in such designs, concentrated stresses are still
likely to occur on the concrete at the interface between the
CFT column and surrounding base concrete if the connection
is not adequately detailed. Once the concrete at the contact
surface becomes crushed due to heavy stress, as shown in
Fig. 1(b), the rigidity of the base connections will be reduced,
and the structural performance will degrade accordingly. In
such situations, high level stress at the anchor bolts will
return and the effectiveness of the base connections becomes
questionable. Interaction among the embedded CFT column,
anchor bolts and surrounding concrete in the foundation
incurs a complicated load transmission mechanism. To prevent
undesirable stress distribution within the base concrete, a
simple and efficient remedy to improve the base connection
effectiveness is essential.
0143-974X/$ - see front matter c 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jcsr.2006.02.002
2. 1334 H.-L. Hsu, H.-W. Lin / Journal of Constructional Steel Research 62 (2006) 1333–1340
Fig. 1. Fabrication of column base connections: (a) exposed base connection; (b) embedded base connection; (c) proposed CFT to base connections.
A strengthening scheme involving adding stiffeners at the
embedded segments of the CFT columns, as shown in Fig. 1(c),
is proposed in this study. This strengthening scheme is intended
to minimize the tendency of the concrete to crush, shift the
critical section from the column bottom to the top of the base
concrete, improve the connection rigidity, and enhance the
design efficiency of CFT structural systems. To accomplish this
goal, a series of combined load tests on the CFT column base
connections with various stiffeners were conducted. Results
from specimens tested under combined axial and lateral loads
were used to define the relationship between the design
details and base connection performance, such as rigidity and
energy dissipation capability, and establish references for CFT
structural system design.
2. Experimental program
2.1. Specimens
Seven square CFT members at various lengths (0.5D, 1.0D
and 1.5D; D = section depth) embedded in corresponding
foundations were fabricated for testing. The dimensions of the
steel tubes for all CFT members were 350 × 350 × 7 mm
(width×depth×thickness),which resulted in a width/thickness
ratio of 50. The yield strength of the steel tube was 324 N/mm2.
Each steel tube was fillet-welded to a 32 mm thick end plate
before concrete casting. Foundation concrete was cast in two
pours: one for the anchor bolt mounting and a second to
complete the foundation and fill the core of the CFT members.
Concrete strengths were determined from cylinder tests for the
3. H.-L. Hsu, H.-W. Lin / Journal of Constructional Steel Research 62 (2006) 1333–1340 1335
Fig. 2. Specimen details: (a) top view; (b) side view.
first and second pours at 24.3 and 35.4 N/mm2, respectively.
Four ASTM A325 M27 anchor bolts were used to erect the CFT
member in each foundation. To investigate the feasibility of
this strengthening scheme, three specimens were stiffened with
different stiffener lengths and embedded into the foundations.
The stiffeners were made from 75×16 mm (width×thickness)
ASTM A36 steel plates and were attached to the CFT members
by fillet welding. This was conducted to investigate whether
surface failure could be moved from the highly-stressed CFT
embedded area to the surface of the foundation so that the
foundation integrity could be sustained and CFT member
performance fully developed. The stiffened and unstiffened
specimens were labeled S-series and U-series, respectively.
Specimen details are shown in Fig. 2. Table 1 also lists the
compositions of the specimens.
2.2. Test setup
Each specimen was mounted onto the strong floor with
four high strength rods. To obtain the flexural rigidity of
the base connection for future comparisons and establish
the relationship between the base rigidity and corresponding
fabrication details, specimens were first subjected to only
lateral loads within the elastic range. After the elastic load
tests, the specimens were unloaded and then tested under
combined constant axial and cyclic lateral loads. Two sets of
Table 1
Specimen compositions and the corresponding rigidities
Specimen Embedded depth (D) Stiffener Anchor bolt α
U-05 0.5D No Yes 2.13
U-10 1.0D No Yes 2.58
U-15 1.5D No Yes 2.80
S-00 0 Yes Yes 1.08
S-05 0.5D Yes Yes 2.41
S-10 1.0D Yes Yes 2.79
S-15 1.5D Yes Yes 2.92
D= depth of CFT = 350 mm.
Fig. 3. Displacement history.
load apparatus were used to generate the required loads. The
lateral load was generated using a servo-controlled hydraulic
actuator through a series of prescribed cyclic displacements,
as shown in Fig. 3. The constant axial load was generated
using two hydraulic jacks pushing against a stiffened loading
beam. The test setup is shown in Fig. 4. The magnitude of
the axial load for all specimens was set to 15% of the CFT
member’s compressive strength (Po), which could be calculated
as follows:
Po = As Fys + Ac fc (1)
in which As and Ac are the cross-sectional areas of the
steel tube and the in-filled concrete, and Fys and fc are the
yield strength of the tube and the compressive strength of the
concrete, respectively. Strain gages mounted on the anchor
bolts and the CFT tubes were used to measure the specimen
responses.
3. Observations
Fig. 5 shows the hysteretic relationships and the correspond-
ing failure patterns for specimens with various base com-
positions. It can be observed from the figure that inelastic
elongation of the anchor bolts was exhibited in the exposed
base connection, i.e. S-00. Only poor hysteretic performance
can be achieved with this specimen. Anchor bolt yielding was
significantly alleviated when the CFT members were embed-
ded in the foundations. From Fig. 5(b)–(g), whenever the base
connections possessed sufficient strength, the CFT members
were capable of developing full bearing capacity, such as U-10,
U-15, S-05, S-10, and S-15 specimens.
4. 1336 H.-L. Hsu, H.-W. Lin / Journal of Constructional Steel Research 62 (2006) 1333–1340
Fig. 4. Test setup: (a) front view; (b) side view.
Note that when further comparing the responses of the
S-05 and U-05 specimens, although the CFT columns in both
specimens were embedded in the foundations the same depth,
the stiffened S-05 successfully developed full CFT column
strength, while the unstiffened U-05 exhibited premature
cracking in the base concrete before the CFT member reached
its moment capacity. These phenomena revealed that the critical
embedded lengths, i.e. lengths to prevent base concrete failures,
can be significantly reduced when the strengthening scheme
is adopted. The critical embedded length for the unstiffened
specimen in this study was approximately 1D. This value
was significantly reduced to 0.5D in the stiffened specimen.
This reduction indicated an improved efficiency and justified
the effectiveness of the proposed strengthening scheme in
the base connection design. Further benefits of adopting the
stiffeners in the base connection designs can be validated by
the enhancements in the rigidity of the base connections and the
energy dissipation of the system, as discussed in the subsequent
sections.
4. Comparisons of test results
4.1. Rigidity of base connections
To effectively predict the structural responses of CFT
systems under earthquakes, the member stiffness and the
corresponding boundary conditions of the foundations must
first be adequately defined. For a column member rigidly
attached to the foundation and subjected to lateral load at
the member tip, i.e. a cantilever member as shown in Fig. 6,
the system’s flexural stiffness (K) can be evaluated using the
following expression:
K = 3E I/L3
. (2)
However, the theoretical rigid boundary does rarely exist in
a real structure. Therefore, a reasonable estimation on the
boundary rigidity with specified fabrication details is more
feasible and essential for structural designs. This concern is
particularly critical for the design of CFT structures, because
the structures usually possess higher strength and stiffness than
steel or reinforced concrete structures with similar member
dimensions. In such cases, influence due to discrepancy in base
rigidity estimation will become significant because analytical
results based on inadequate information will be biased.
To account for the effectiveness of the base connections, the
flexural stiffness of specimens with various fabrication details
can be expressed in the following form:
K = αE I/L3
(3)
in which α is a coefficient related to the various foundation
placement details. The α values for the specimens are evaluated
using the information obtained from the elastic load tests, listed
in Table 1 and compared in Fig. 7.
As indicated in the previous section the failures of base
connections are usually governed by the length of the embedded
segment. Once the embedded member depth is larger than
the critical value, the CFT member reaches its capacity prior
to foundation failure. Under this circumstance, it can still be
observed from Fig. 7 that the base rigidities varied even though
the specimens possessed sufficient strength and similar failure
patterns, such as U-10 and S-10. In general, the base rigidities
increased with increasing embedded length; however, the
increments were at different rates for stiffened and unstiffened
bases. They were:
(For U-series) α = −0.4763D2
+ 1.627D + 1.4313 (≤3) (4)
(For S-series) α = −0.4878D2
+ 1.4888D + 1.7882 (≤3). (5)
It can be observed from Fig. 7 that significant improvement
was achieved whenever the strengthening stiffeners were
presented. It is also interesting to find that when the embedded
length reached an extreme value, 1.5D, which is too costly
in construction projects, the achievable member stiffness is
still less than the theoretical 3E I/L3, therefore, the above
5. H.-L. Hsu, H.-W. Lin / Journal of Constructional Steel Research 62 (2006) 1333–1340 1337
Fig. 5. Hysteretic relationships and the corresponding failure patterns for specimens with various placement details: (a) S-00; (b) U-05; (c) S-05; (d) U-10; (e) S-10;
(f) U-15; (g) S-15.
6. 1338 H.-L. Hsu, H.-W. Lin / Journal of Constructional Steel Research 62 (2006) 1333–1340
Fig. 5. (continued)
expressions can serve as more feasible design references for
design purposes.
4.2. Load transmission mechanism
For base connections with embedded CFT segments and
anchor bolts, the connection strength can be evaluated by
summing the component strengths of the anchor bolts and
confining concrete. As stated in previous sections that reduction
in stress concentration to avoid anchor bolt yielding is a major
concern in the effective CFT base connection design. This
concern can be investigated by comparing the stress levels
of anchor bolts in base connections with various placement
details. Fig. 8 shows the comparisons of the ratios between the
moments resisted by the anchor bolts, (Mbolt), and the whole
base connection, (Mbase). The load induced on the anchor bolts
was calculated using the strain measurements installed on the
anchor bolts.
It can be found from the figure that for CFT base connection
with less embedded segment, strength requirement for the
anchor bolts became extremely critical. For example, the anchor
bolts of the U-05 specimen were required to provide 33%
of the base connection’s moment resisting capacity when the
column top reached 3% drift ratio. This induced heavy stress
7. H.-L. Hsu, H.-W. Lin / Journal of Constructional Steel Research 62 (2006) 1333–1340 1339
Fig. 6. Cantilever member subjected to lateral load at member tip.
concentration on the anchor bolts and increased the possibility
of concrete fracturing at the bolt locations. However, when
pairs of stiffeners were added to the embedded CFT segment
at the base connection with details the same as U-05, i.e. S-
05, the induced stress, at the same drift, on the anchor bolts
was significantly reduced, approximately to 2/3 of that of
U-05. These phenomena, in conjunction with the achievable
Fig. 7. Comparisons of base rigidities.
base rigidities described in previous sections, demonstrated the
effectiveness of the stiffening scheme to the improvement of
base connection performance.
4.3. Energy dissipation
To further investigate the effect of the proposed strength-
ening scheme on the seismic performance of CFT base con-
nections, the systems’ energy dissipation capacities were com-
Fig. 8. Comparisons of moment resisting ratios: (a) specimens with different embedded depths; (b) specimens with various stiffening schemes.
8. 1340 H.-L. Hsu, H.-W. Lin / Journal of Constructional Steel Research 62 (2006) 1333–1340
Fig. 9. Comparisons of energy dissipations.
pared. Energy dissipation was calculated by the total area
bounded by the hysteresis loops. Fig. 9 shows energy dissipa-
tion comparisons for the tested specimens. It can be found from
the figure that the exposed base connection, i.e. S-00, mounted
with anchor bolts only, exhibited poor performance due to in-
adequate energy dissipation mechanism. An improved energy
dissipating performance was achieved in specimen S-05 when
the CFT member was embedded in the foundation. The energy
dissipation capability continued to increase when the embedded
depth increased. This phenomenon stabilized when the embed-
ded depth, for the stiffened specimens, reached a critical value,
approximately 1.0D. Further comparisons of energy dissipa-
tion capabilities between the stiffened and unstiffened spec-
imens also showed that the former designs possessed higher
seismic resistance than the latter when they were embedded to
the same depth, which justified the applicability of the strength-
ening schemes.
5. Conclusions
This study focused on the experimental investigation of
the relationship between design details and column base
performance. Results from specimens tested under combined
axial and lateral loads were used to define the effectiveness
of the base connections. Test results showed that the rigidities
of the base connections increased when the embedded depths
were increased. It was also found that the base connections
possessed higher stiffness and energy dissipation capability
when stiffeners were added to the embedded segment. An
empirical expression for base rigidity estimation is proposed
for design references.
Acknowledgments
This study was partially supported by the National Science
Council of the Republic of China under Grant No. NSC
90-2625-Z-008-011 and NSC 91-2625-Z-008-011, which is
gratefully acknowledged.
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