Experimental Investigation of Flexural Behavior of Ultra-High-Performance Concrete with Coarse Aggregate-Filled Steel Tubes.

Fanghong Wu,Xuetao Lyu,Ben Li,Yanqin Zeng

doi:10.3390/ma14216354

Fanghong Wu, Xuetao Lyu + Show 2 more

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https://doi.org/10.3390/ma14216354

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Abstract

This paper presents an experimental investigation of flexural behavior of circular ultra-high-performance concrete with coarse aggregate (CA-UHPC)-filled steel tubes (CA-UHPCFSTs). A total of seven flexural members were tested under a four-point bending load. The failure modes, overall deflection curves, moment-versus-curvature relationships, moment-versus-strain curves, strain distribution curves, ductility, flexural stiffness and ultimate flexural capacity were evaluated. The results indicate that the CA-UHPCFSTs under bending behaved in a good ductile manner. The CA-UHPC strength has a limited effect on the ultimate flexural capacity, while the addition of steel fiber can improve the ultimate flexural capacity. Increasing the steel tube thickness leads to higher flexural stiffness and ultimate flexural capacity. There is a significant confinement effect between the steel tube and the CA-UHPC core in the compressive zone and centroidal plane after the specimen enters the elastic-plastic stage, while the confinement effect in the tensile zone is minimal. Moreover, the measured flexural stiffness and ultimate flexural capacity were compared with the predictions using various design specifications. Two empirical formulas for calculating the initial and serviceability-level flexural stiffness of CA-UHPCFSTs are developed. Further research is required to propose the accurate design formula for the ultimate flexural capacity of CA-UHPCFSTs.

Highlights

Accepted: 19 October 2021Concrete-filled steel tubes (CFSTs) combine the advantages and overcome the shortcomings of concrete and steel materials [1]
Various design codes and specifications were adopted to predict the flexural stiffness and ultimate flexural capacity of circular CA-UHPC-filled high-strength steel tube (UHPCFST) beams subjected to pure bending load, including EC4 (2004) [19], AISC/LRFD (1999) [24], AIJ (1999) [25], AS 5100.6 (2004) [26], BS 5400-5 (2005) [27], GB 50936 (2014) [28], and the design formula proposed by Han [34]
All the CA-UHPCFST members behaved in a good ductile manner

Summary

Introduction

Concrete-filled steel tubes (CFSTs) combine the advantages and overcome the shortcomings of concrete and steel materials [1]. Due to the confinement action of the steel tube, the compressive strength and ductility of concrete core can be substantially improved. The infilling of concrete effectively delays the global and local buckling of the steel tube. The limitations of natural resources and the seriousness of environmental disruption have produced an urgent need for sustainable and high-performance materials. Ultra-high-performance concrete with coarse aggregate (CA-UHPC), an innovative cement-based composite material with ultra-high strength, good ductility, superior durability and relatively low cost, has broad application prospects in bridges, roads, ocean engineering, military buildings and infrastructure [2]. The properties of UHPC have been extensively investigated in the last 30 years

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