• Earthquakes and Structures
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• 제10권4호
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• pp.769-788
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• 2016

The present study aimed at investigating the effect of a special plaster on the out-of-plane behavior of masonry walls. A reference specimen, plastered with conventional plaster, and a specimen plastered with a special plastered were tested under reversed cyclic lateral loading. The specimens were identical in dimensions and material properties. The special plaster contained an additive, which increased the adherence strength of the plaster to the wall. The amount of the additive in the mortar was adjusted based on the preliminary material tests. The influence of the plaster on the wall behavior was evaluated according to the initial cracking load, type of failure, energy absorption capacity (modulus of toughness), and crack pattern of the wall. Despite having limited contribution to the ductility, the special plaster increased the ultimate load capacity of the wall about 25%. The failure mode of the wall with special plaster resembled the plastic failure mechanism of a reinforced concrete slab in the formation of yielding lines along the wall. The deflection at failure and the modulus of toughness of the wall with special plaster were measured to be in order of 60% and 75% of the corresponding values of the reference wall.

• Earthquakes and Structures
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• 제11권4호
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• pp.665-680
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• 2016

This paper focuses on the study of seismic behavior of steel reinforced concrete special-shaped column-beam joints. Six specimens, which are designed according to the principle of strong-member and weak-joint core, are tested under low cyclic reversed load. Key parameters include the steel form in column section and the ratio of column limb height to thickness. The failure mode, load-displacement curves, ductility, stiffness degradations, energy dissipation capacity and shear deformation of joint core of the test subassemblies are analyzed. The results indicate that SRC special-shaped column-beam joints have good seismic behavior. All specimens failed due to the shear failure of the joint core, and the failure degree between the two sides of joint core is similar for the exterior joint but different for the corner joint. Compared to the joints with channel steel truss, the joints with solid web steel skeleton illustrate better ductility and energy dissipation capacity, but the loading capacity and stiffness are roughly close. With the increasing of the ratio of column limb height to thickness, the joints illustrate higher loading capacity and stiffness, better energy dissipation capacity, but worse ductility.

• International Journal of Concrete Structures and Materials
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• 제6권1호
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• pp.19-29
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• 2012

In this study, three isolated interior flat slab-column connections that include three types of shear reinforcement details; stirrup, shear stud and shear band were tested under reversed cyclic lateral loading to observe the capacity of slab-column connections. These reinforced joints are 2/3 scale miniatures designed to have identical punching capacities. These experiments showed that the flexural failure mode appears in most specimens while the maximum unbalanced moment and energy absorbing capacity increases effectively, with the exception of an unreinforced standard specimen. Finally, the results of the experiments, as wel l as those of experiments previously carried out by researchers, are applied to the eccentricity shear stress model presented in ACI 318-08. The failure mode is therefore defined in this study by considering the upper limits for punching shear and unbalanced moment. In addition, an intensity factor is proposed for effective widths of slabs that carry an unbalanced moment delivered by bending.

• Structural Engineering and Mechanics
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• 제51권3호
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• pp.413-431
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• 2014

By carrying out the experiment of eight pieces of brick masonry walls with pilaster strengthened by Glass fiber reinforced polymer (GFRP) and one piece of normal masonry wall with pilaster under low reversed cyclic loading, the failure characteristic of every wall is explained; Seismic performances such as hysteresis, stiffness and its degeneration, deformation, energy consumption and influence of some measures including strengthening means, reinforcement area proportion between GFRP and wall surface, "through-wall" anchor on reinforcement effects are studied. The test results showed that strengthening modes have little influence on stiffness, stiffness degeneration and deformation of the wall, but it is another thing for energy consumption of the wall; The ultimate load, deformation and energy consumption of the walls reinforced by glass fiber sheets was increased remarkably, rigidity and its degeneration was slower; Seismic performance of the wall which considers strengthening means, reinforcement area proportion between GFRP and wall surface, "through-wall" anchor at the same time is better than under the other conditions.

• Structural Monitoring and Maintenance
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• 제1권3호
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• pp.273-292
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• 2014

The effectiveness of a retrofitting method for concrete columns with particular weaknesses is experimentally evaluated and presented in this paper. Structural deficiencies namely the inadequacy of transverse reinforcement and short length of lap splices are very common in columns found in structures built prior to the 1960s and 1970s. Recent earthquakes worldwide have caused severe damages and collapses of these structures. Nevertheless, the importance of improving the load transfer capacity between the deficiently lap-spliced bars is usually underestimated during the strengthening procedures applied in old buildings, though critical for the safety of the residents' lives. Thus, the seismic performance of the enhanced columns is frequently overestimated. The retrofitting approach presented herein involves reinforced concrete jacketing of the column sub-assemblages and welding of the lap-spliced bars to prevent the splice failure and conform to the provisions of modern design Codes. The cyclic lateral loading response of poorly confined original column specimens with insufficient lap splices and the seismic behavior of the retrofitted columns are compared. Test results clearly demonstrate that the retrofitting procedure followed is an effective way of significantly improving the seismic performance of substandard columns found in old buildings.

• Computers and Concrete
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• 제10권4호
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• pp.361-377
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• 2012

Four Reinforced Concrete (RC) single span structural walls having various opening sizes and locations were constructed and tested under lateral reversed cyclic loading at the structural laboratory of Kyoto University. These specimens were scaled to 40% and represented the lower three stories of a six-storied RC building. The main purposes of the experimental tests were to evaluate the shear behavior and to identify the influence of opening ratios on the cracks distribution and shear strength of RC structural walls. The shear strength of the specimens was estimated by combining the shear strength of structural wall without openings and the reduction factor that takes into account the openings. Experimental and analytical results showed that the shear strength was different depending on the loading direction due to opening locations. A two-dimensional finite element analysis was carried out to simulate the performance of the tested specimens. The constructed finite elements model simulated the lateral load-drift angle relations quite well.

• Steel and Composite Structures
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• 제31권3호
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• pp.217-232
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• 2019

Modular steel buildings consist of prefabricated room-sized structural units that are manufactured offsite and installed onsite. The inter-module connections must fulfill the assembly construction requirements and soundly transfer the external loads. This work proposes an innovative assembled connection suitable for modular buildings with concrete-filled steel tube columns. The connection uses pretensioned strands and plugin bars to vertically connect the adjacent modular columns. The moment-transferring performance of this inter-module connection was studied through monotonic and cyclic loading tests. The results showed that because of the assembly construction, the connected sections were separated under lateral bending, and the prestressed inter-module connection performed as a weak semirigid connection. The moment strength at the early loading stage originated primarily from the contact bonding mechanism with the infilled concrete, and the postyield strength depended mainly on the tensioned strands. The connection displayed a self-centering-like behavior that the induced deformation was reversed during unloading. The energy dissipation originated primarily from frictional slipping of the plugin bars and steel strands. The moment transferring ability was closely related to the section dimension and the arrangements of the plugin bars and steel strands. A simplified strength calculation and evaluation method was also proposed, and the effectiveness was validated with the test data.

• Structural Engineering and Mechanics
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• 제90권5호
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• pp.447-458
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• 2024

This study investigated the influence of scale ratio and vertical load on the seismic performance of Puzuo joints in traditional Chinese timber structures. Three low-cyclic reversed loading tests were conducted on three scaled specimens of Bujian Puzuo in Yingxian Wooden Pagoda. This study focused on the deformation patterns and analyzed seismic performance under varying scale ratios and vertical loads. The results indicated that the slip and rotational deformations of Bujian Puzuo were the primary deformations. The scale of the specimen did not affect the layer where the maximum interlayer slip occurred, but it did decrease the proportion of slip deformation. Conversely, the reducing vertical load caused the layer with the maximum slippage and the position of the damaged Dou components to shift upward, and the proportion of slip deformation increased. When the vertical load was decreased by 3.7 times, the maximum horizontal bearing capacity under positive and negative loadings, initial stiffness, and energy dissipation of the specimen decreased by approximately 60%, 58.79%, 69.62%, and 57.93%, respectively. The horizontal bearing capacity under positive loading and energy dissipation of the specimen increased by 35.63% and 131.54%, when the specimen scale was doubled and the vertical load was increased by 15 times.

• Steel and Composite Structures
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• 제27권5호
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• pp.577-598
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• 2018

The imperfect steel-concrete interface bonding is an important deficiency of the concrete-filled double skin tubular (CFDST) columns that led to separating concrete and steel surfaces under lateral loads and triggering buckling failure of the columns. To improve this issue, it is proposed in this study to use longitudinal and transverse steel stiffeners in CFDST columns. CFDST columns with different patterns of stiffeners embedded in the interior or exterior surfaces of the inner or outer tubes were analyzed under constant axial force and reversed cyclic loading. In the finite element modeling, the confinement effects of both inner and outer tubes on the compressive strength of concrete as well as the effect of discrete crack for concrete fracture were incorporated which give a realistic prediction of the seismic behavior of CFDST columns. Lateral strength, stiffness, ductility and energy absorption are evaluated based on the hysteresis loops. The results indicated that the stiffeners had determinant role on improving pinching behavior resulting from the outer tube's local buckling and opening/closing of the major tensile crack of concrete. The lateral strength, initial stiffness and energy absorption capacity of longitudinally stiffened columns with fixed-free end condition were increased by as much as 17%, 20% and 70%, respectively. The energy dissipation was accentuated up to 107% for fixed-guided end condition. The use of transverse stiffeners at the base of columns increased energy dissipation up to 35%. Axial load ratio, hollow ratio and concrete strength affecting the initial stiffness and lateral strength, had negligible effect of the energy dissipation of the columns. It was also found that the longitudinal stiffeners and transverse stiffeners have, respectively, negative and positive effects on ductility of CFDST columns. The conclusions, drawn from this study, can in turn, lead to the suggestion of some guidelines for the design of CFDST columns.

• Steel and Composite Structures
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• 제19권3호
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• pp.547-567
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• 2015

The paper makes the experimental and finite-element-analysis investigation on the seismic behavior of the rebar-penetrated joint between gangue concrete filled steel tubular column and reinforced gangue concrete beam under low cyclic reversed loading. Two specimens are designed and conducted for the experiment to study the seismic behavior of the rebar-penetrated joint under cyclic loading. Then, finite element analysis models of the rebar-penetrated joint are developed using ABAQUS 6.10 to serve as the complement of the experiment and further analyze the seismic behavior of the rebar-penetrated joint. Finite element analysis models are also verified by the experimental results. Finally, the hysteretic performance, the bearing capacity, the strength degradation, the rigidity degradation, the ductility and the energy dissipation of the rebar-penetrated joint are evaluated in detail to investigate the seismic behavior of the rebar-penetrated joint through experimental results and finite element analysis results. The research demonstrates that the rebar-penetrated joint between gangue concrete filled steel tubular column and reinforced gangue concrete beam, with full and spindle-shaped load-displacement hysteretic curves, shows generally the high ductility and the outstanding energy-dissipation capacity. As a result, the rebar-penetrated joint exhibits the excellent seismic performance and meets the earthquake-resistant requirements of the codes in China. The research provides some references and suggestions for the application of the rebar-penetrated joint in the projects.