Study on the Bond-Slip Performance of CFSSTs Based on Push-Out Tests

Lai Wang,Huirong Chen,Hongyan Yang,Wei Xuan,Jitao Zhong,Haitao Chen,Shuai Mi

doi:10.1155/2018/2959827

Lai Wang, Huirong Chen + Show 5 more

Open Access

https://doi.org/10.1155/2018/2959827

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Abstract

To study the interfacial bond-slip performance of concrete-filled square steel tubes (CFSSTs), taking the core concrete strength, slenderness ratio, and width-to-thickness ratio as the influencing factors; 9 specimens were designed with 3 factors and 3 levels for the orthogonal test method. In addition, different from the above 9 specimens, one specimen without rust removal was designed for the purpose of comparison. Based on the bond stress distribution and deformation coordination relationships between the specimens during the push-out tests, a theoretical formula for calculating the relative slip of a CFSST was deduced. The results show that with the increase of load, the relative slip at the loading ends was earlier than that at the free ends of the specimens; the interfacial bond failure and relative slip gradually developed from the two ends towards the centre of the specimens; the increase of the bond stress in the middle part was faster than that at the ends of the specimens. The order of these factors from main to secondary is the presence of rust in the inner wall of the square steel tube, the slenderness ratio, the core concrete strength, and the width-to-thickness ratio.

Highlights

CFST structures have the advantages of a high bearing capacity, good plasticity and toughness, convenient construction, and good economic benefits [1, 2]
Due to the differences in material properties of the steel tube and core concrete, their strains are not completely continuous under the action of load. ere is a certain slippage and bond strength between the steel tube and the core concrete. e cooperation between the composition of the steel tube and the core concrete in the CFST is the fundamental reason for this series of advantages, and the bond strength between the steel tube and core concrete directly affects the ability of the two kinds of materials to work together
The influence of the concrete strength, the slenderness ratio, the width-to-thickness ratio, and the presence of rust in the inner wall of the square steel tube on the bond-slip performance of concrete-filled square steel tubes (CFSSTs) is investigated, and 10 CFSST specimens are utilized for push-out tests

Summary

Introduction

CFST (concrete-filled steel tube) structures have the advantages of a high bearing capacity, good plasticity and toughness, convenient construction, and good economic benefits [1, 2]. Virdi and Dowling [10, 11] have adopted the method of push-out tests to study the bond-slip behaviour of CFSTs. Advances in Materials Science and Engineering e test results show that the strength of the core concrete does not clearly influence the bond strength of CFSTs. e trend of the interfacial bond strength is not obvious with the variation in the diameter-to-thickness ratios of the circular steel tubes, and the dispersion of the experimental results is relatively large. The influence of the concrete strength, the slenderness ratio, the width-to-thickness ratio, and the presence of rust in the inner wall of the square steel tube on the bond-slip performance of CFSSTs is investigated, and 10 CFSST specimens are utilized for push-out tests. A theoretical formula for the relative slip of CFSSTs is deduced, which has important theoretical significance and practical value in engineering for improving the design theory of CFSTs [21]

Experimental Study

Test Result and Analysis

E2s t2u ln

Findings

Conclusion