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.

Bond-slip behavior of reactive powder concrete-filled square steel tube

Qiuwei Wang,Lu Wang,Hang Zhao 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.45 No.6

This paper presented an experimental study of the bond-slip behavior of reactive powder concrete (RPC)-filled square steel tube. A total of 18 short composite specimens were designed forstatic push-out test, and information on their failure patterns, load-slip behavior and bond strength was presented. The effects of width-to-thickness ratio, height-to-width ratio and the compressive strength of RPC on the bond behavior were discussed. The experimental results show that:(1) the push-out specimens remain intact and no visible local buckling appears on the steel tube, and the interfacial scratches are even more pronounced at the internal steel tube of loading end; (2) the bond load-slip curves with different width-to-thickness ratios can be divided into two types, and the main difference is whether the curves have a drop in load with increasing slip; (3) the bond strength decreases with the increase of the width-to-thickness ratio and height-width ratio, while the influence of RPC strength is not consistent; (4) the slippage has no definite correlation with bond strength and the influence of designed parameters on slippage is not evident. On the basis of the above analysis, the expressions of interface friction stress and mechanical interaction stress are determined by neglecting chemical adhesive force, and the calculation model of bond strength for RPC filled in square steel tube specimens is proposed. The theoretical results agree well with the experimental data.

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.

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.

Protective association of Klotho rs495392 gene polymorphism against hepatic steatosis in non-alcoholic fatty liver disease patients

Wen-Yue Liu,Xiaofang Zhang,Gang Li,Liang-Jie Tang,Pei-Wu Zhu,Rafael S. Rios,Kenneth I. Zheng,Hong-Lei Ma,Xiao-Dong Wang,Qiuwei Pan,Robert J. de Knegt,Luca Valenti,Mohsen Ghanbari,Ming-Hua Zheng 대한간학회 2022 Clinical and Molecular Hepatology(대한간학회지) Vol.28 No.2

Background/Aims: Non-alcoholic fatty liver disease (NAFLD) is closely associated with metabolic dysfunction. Among the multiple factors, genetic variation acts as important modifiers. Klotho, an enzyme encoded by the klotho (KL) gene in human, has been implicated in the pathogenesis of metabolic dysfunctions. However, the impact of variants in KL on NAFLD risk remains poorly understood. The aim of this study was to investigate the impact of KL rs495392 C>A polymorphism on the histological severity of NAFLD. Methods: We evaluated the impact of the KL rs495392 polymorphism on liver histology in 531 Chinese with NAFLD and replicated that in the population-based Rotterdam Study cohort. The interactions between the rs495392, vitamin D, and patatin-like phospholipase domain containing 3 (PNPLA3) rs738409 polymorphism were also analyzed. Results: Carriage of the rs495392 A allele had a protective effect on steatosis severity (odds ratio [OR], 0.61; 95% confidence interval [CI], 0.42–0.89; P=0.010) in Chinese patients. After adjustment for potential confounders, the A allele remained significant with a protective effect (OR, 0.66; 95% CI, 0.45–0.98; P=0.040). The effect on hepatic steatosis was confirmed in the Rotterdam Study cohort. Additional analysis showed the association between serum vitamin D levels and NAFLD specifically in rs495392 A allele carriers, but not in non-carriers. Moreover, we found that the rs495392 A allele attenuated the detrimental impact of PNPLA3 rs738409 G allele on the risk of severe hepatic steatosis. Conclusions: The KL rs495392 polymorphism has a protective effect against hepatic steatosis in patients with NAFLD.