Punching performance of RC slab-column connections with inner steel truss

Shi, Qingxuan,Ma, Ge,Guo, Jiangran,Ma, Chenchen Techno-Press 2022 Advances in concrete construction Vol.14 No.3

As a brittle failure mode, punching-shear failure can be widely found in traditional RC slab-column connections, which may lead to the entire collapse of a flat plate structure. In this paper, a novel RC slab-column connection with inner steel truss was proposed to enhance the punching strength. In the proposed connection, steel trusses, each of which was composed of four steel angles and a series of steel strips, were pre-assembled at the periphery of the column capital and behaved as transverse reinforcements. With the aim of exploring the punching behavior of this novel RC slab-column connection, a static punching test was conducted on two full-scaled RC slab specimens, and the crack patterns, failure modes, load-deflection and load-strain responses were thoroughly analyzed to explore the contribution of the applied inner steel trusses to the overall punching behavior. The test results indicated that all the test specimens suffered the typical punching-shear failure, and the higher punching strength and initial stiffness could be found in the specimen with inner steel trusses. The numerical models of tested specimens were analyzed in ABAQUS. These models were verified by comparing the results of the tests with the results of the analyzes, and subsequently the sensitivity of the punching capacity to different parameters was studied. Based on the test results, a modified critical shear crack theory, which could take the contribution of the steel trusses into account, was put forward to predict the punching strength of this novel RC slab-column connection, and the calculated results agreed well with the test results.

Seismic behavior of steel reinforced concrete (SRC) joints with new-type section steel under cyclic loading

Qiuwei Wang,Qingxuan Shi,Hehe Tian 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.19 No.6

No significant improvement has been observed on the seismic performance of the ordinary steel reinforced concrete (SRC) columns compared with the reinforced concrete (RC) columns mainly because I, H or core cross-shaped steel cannot provide sufficient confinement for core concrete. Two improved SRC columns by constructing with new-type section steel were put forward on this background: a cross-shaped steel whose flanges are in contact with concrete cover by extending the geometry of webs, and a rotated cross-shaped steel whose webs coincide with diagonal line of the column's section. The advantages of new-type SRC columns have been proved theoretically and experimentally, while construction measures and seismic behavior remain unclear when the new-type columns are joined onto SRC beams. Seismic behavior of SRC joints with new-type section steel were experimentally investigated by testing 5 specimens subjected to low reversed cyclic loading, mainly including the failure patterns, hysteretic loops, skeleton curves, energy dissipation capacity, strength and stiffness degradation and ductility. Effects of steel shape, load angel and construction measures on seismic behavior of joints were also analyzed. The test results indicate that the new-type joints display shear failure pattern under seismic loading, and steel and concrete of core region could bear larger load and tend to be stable although the specimens are close to failure. The hysteretic curves of new-type joints are plumper whose equivalent viscous damping coefficients and ductility factors are over 0.38 and 3.2 respectively, and this illustrates the energy dissipation capacity and deformation ability of new-type SRC joints are better than that of ordinary ones with shear failure. Bearing capacity and ductility of new-type joints are superior when the diagonal cross-shaped steel is contained and beams are orthogonal to columns, and the two construction measures proposed have little effect on the seismic behavior of joints.

Research on the Physical Inter-story Drift Ratio and the Damage Evaluation of RC Shear Wall Structures

Feng Wang,Qingxuan Shi,Peng Wang 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.6

Based on the analysis of the lateral displacement mode and the deformation composition of shear wall structures, the inter-story displacement is divided into physical inter-story displacementand non-physical inter-story displacement. Then, the calculation method of the physical inter-story displacement of a shear wall in the elastic stage and simplified calculation methods in the elastic-plastic stage are given. On this basis, the proportion of the shear and bending deformations of the shear wall structure are analysed using Perform-3D finite element (FE) software. The variation law of the section rotation angle, the inter-story drift ratio, and the physical inter-story drift ratio along the height of the coupled shear wall and wall limb shear wall structure are analysed. Subsequently, a new dual control damage index of the deformation and energy is proposed, and the damage of the structure is evaluated. The results show that the inter-story drift ratio of the shear wall structure should be controlled by the physical inter-story drift ratio, and the shear displacement should not be ignored in the calculation of the inter-story displacement. The proposed dual control damage index of the deformation and energy can better reflect the damage of the structure.

Seismic behaviour of enlarged cross steel-reinforced concrete columns under various loadings

Peng Wang,Qingxuan Shi,Feng Wang,Qiuwei Wang 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.1

Based on finite element software, a simulation programme is used to evaluate the seismic behaviour of new-type steel-reinforced concrete (SRC) columns, called enlarged cross steel-reinforced concrete (ECSRC) columns. With abundant simulations, the effects of the loading paths, number of loading cycles, incremental amplitude of displacement and variable axial load on the seismic response of the ECSRC columns were investigated. The results indicate that the seismic behaviour of the column is highly dependent on the loading paths, and it was observed that the loading paths produced a significant effect on the hysteretic response of the columns. Compared with those under uniaxial loading, the yield load, maximum load, ultimate displacement and ductility coefficient of the ECSRC columns under biaxial loading are reduced by 13.47%, 18.01%, 12.17% and 32.64%, respectively. The energy dissipation capacity of the columns is highly dependent on the loading paths. The skeleton curves are not significantly influenced by the number of loading cycles until the yield point of steel and longitudinal reinforcement is reached. With an increase in loading cycles, the yield load, yield displacement, ductility coefficient and maximum load, as well as the corresponding horizontal displacement of the column, are reduced, while the energy dissipation grows. In addition, the yield displacement, yield load, and ductility coefficient increase with an increase in the incremental amplitude of displacement; however, the energy dissipation decreases under these conditions. The seismic performance of the SRC column under variable axial loads clearly exhibits asymmetry that is worse than that observed under constant axial loads.

Optimal Design of Tall Residential Building with RC Shear Wall and with Rectangular Layout

Jinjie, Men,Qingxuan, Shi,Zhijian, He Council on Tall Building and Urban Habitat Korea 2014 International journal of high-rise buildings Vol.3 No.4

The objective of optimization is to present a design process that minimizes the total material consumption while satisfying current codes and specifications. In the research an optimization formulation for RC shear wall structures is proposed. And based on conceptual design methodology, an optimization process is investigated. Then optimal design techniques and specific explanations are introduced for residential buildings with shear wall structure, especially for that with a rectangular layout. An example of 30-story building is presented to illustrate the effectiveness of the proposed optimal design process. Furthermore, the influence of aspect ratio on the concrete consumption and the steel consumption of the superstructure are analyzed for this typical RC shear wall structure; and their relations are obtained by regressive analysis. Finally, the optimal material consumption is suggested for the residential building with RC shear wall structure and with rectangular layout. The relation and the data suggested can be used for guiding the design of similar RC shear wall structures.

Experimental study on shear capacity of SRC joints with different arrangement and sizes of cross-shaped steel in column

Qiuwei Wang,Qingxuan Shi,Hehe Tian 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.2

The seismic performance of the ordinary steel reinforced concrete (SRC) columns has no significant improvement compared to the reinforced concrete (RC) columns mainly because I, H or core cross-shaped steel cannot provide sufficient confinement for core concrete. Two improved SRC columns by constructing with new-type shaped steel were put forward on this background, and they were named as enlarging cross-shaped steel and diagonal cross-shaped steel for short. The seismic behavior and carrying capacity of new-type SRC columns have been researched theoretically and experimentally, while the shear behavior remains unclear when the new-type columns are joined onto SRC beams. This paper presents an experimental study to investigate the shear capacity of new-type SRC joints. For this purpose, four new-type and one ordinary SRC joints under low reversed cyclic loading were tested, and the failure patterns, load-displacement hysteretic curves, joint shear deformation and steel strain were also observed. The ultimate shear force of joint specimens was calculated according to the beam-end counterforce, and effects of steel shape, load angel and structural measures on shear capacity of joints were analyzed. The test results indicate that: (1) the new-type SRC joints display shear failure pattern and has higher shear capacity than the ordinary one; (2) the oblique specimens have good bearing capacity if designed reasonably; and (3) the two proposed construction measures have little effect on the shear capacity of SRC joints embedded with diagonal cross-shaped steel. Based on the mechanism observed from the test, the formulas for calculating ultimate shear capacity considering the main factors (steel web, stirrup and axial compression ratio) were derived, and the calculated results agreed well with the experimental and simulated data.

Axial capacity of reactive powder concrete filled steel tube columns with two load conditions

Qiuwei Wang,Qingxuan Shi,Zhaodong Xu,Hanxin He 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.31 No.1

Reactive powder concrete (RPC) is a type of ultra-high strength concrete that has a relatively high brittleness. However, its ductility can be improved by confinement, and the use of RPC in composite RPC filled steel tube columns has become an important subject of research in recent years. This paper aims to present an experimental study of axial capacity calculation of RPC filled circular steel tube columns. Twenty short columns under axial compression were tested and information on their failure patterns, deformation performance, confinement mechanism and load capacity were presented. The effects of load conditions, diameter-thickness ratio and compressive strength of RPC on the axial behavior were further discussed. The experimental results show that: (1) specimens display drum-shaped failure or shear failure respectively with different confinement coefficients, and the load capacity of most specimens increases after the peak load; (2) the steel tube only provides lateral confinement in the elastic-plastic stage for fully loaded specimens, while the confinement effect from steel tube initials at the set of loading for partially loaded specimens; (3) confinement increases the load capacity of specimens by 3% to 38%, and this increase is more pronounced as the confinement coefficient becomes larger; (4) the residual capacity-to-ultimate capacity ratio is larger than 0.75 for test specimens, thus identifying the composite columns have good ductility. The working mechanism and force model of the composite columns were analyzed, and based on the twin-shear unified strength theory, calculation methods of axial capacity for columns with two load conditions were established.

Behaviour of FRP composite columns: Review and analysis of the section forms

Rong, Chong,Shi, Qingxuan,Zhao, Hongchao Techno-Press 2020 Advances in concrete construction Vol.9 No.2

As confining materials for concrete, steel and fibre-reinforced polymer (FRP) composites have important applications in both the seismic retrofit of existing reinforced concrete columns and in the new construction of composite structures. We present a comprehensive review of the axial stress-strain behaviour of the FRP-confined concrete column. Next, the mechanical performance of the hybrid FRP-confined concrete-steel composite columns are comprehensively reviewed. Furthermore, the results of FRP-confined concrete column experiments and FRP-confined circular concrete-filled steel tube experiments are presented to study the interaction relationship between various material sections. Finally, the combinations of material sections are discussed. Based on these observations, recommendations regarding future research directions for composite columns are also outlined.

Estimation of the load-deformation responses of flanged reinforced concrete shear walls

Bin Wang,Qingxuan Shi,Wen-Zhe Cai,YI-Gong Peng 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.73 No.5

As limited well-documented experimental data are available for assessing the attributes of different deformation components of flanged walls, few appropriate models have been established for predicting the inelastic responses of flanged walls, especially those of asymmetrical flanged walls. This study presents the experimental results for three large-scale T-shaped reinforced concrete walls and examines the variations in the flexural, shear, and sliding components of deformation with the total deformation over the entire loading process. Based on the observed deformation behavior, a simple model based on moment-curvature analysis is established to estimate flexural deformations, in which the changes in plastic hinge length are considered and the deformations due to strain penetration are modeled individually. Based on the similar gross shapes of the curvature and shear strain distributions over the wall height, a proportional relationship is established between shear displacement and flexural rotation. By integrating the deformations due to flexure, shear, and strain penetration, a new load-deformation analytical model is proposed for flexure-dominant flanged walls. The proposed model provides engineers with a simple, accurate modeling tool appropriate for routine design work that can be applied to flexural walls with arbitrary sections and is capable of determining displacements at any position over the wall height. By further simplifying the analytical model, a simple procedure for estimating the ultimate displacement capacity of flanged walls is proposed, which will be valuable for performance-based seismic designs and seismic capacity evaluations.

Experimental research on seismic behavior of novel composite RCS joints

Jinjie Men,Zhifeng Guo,Qingxuan Shi 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.19 No.1

Results from an experimental study on the seismic response of six composite reinforced concrete column-to-steel beam interior joints are presented. The primary variable investigated is the details in the joint. For the basic specimen, the main subassemblies of the beam and column are both continuous, and the steel beam flanges extended to the joint are partly cut off. Transverse beam, steel band plates, cove plates, X shape reinforcement bars and end plates are used in the other five specimens, respectively. After the joint steel panel yielded, two failure modes were observed during the test: local failure in Specimens 1, 2 and 4, shear failure in Specimens 3, 5 and 6. Specimens 6, 3, 5 and 4 have a better strength and deformation capacity than the other two specimens for the effectiveness of their subassemblies. For Specimens 2 and 4, though the performance of strength degradation and stiffness degradation are not as good as the other four specimens, they all have excellent energy dissipation capacity comparing to the RC joint, or the Steel Reinforced Concrete (SRC) joint. Based on the test result, some suggestions are presented for the design of composite RCS joint.