Abstract
This paper concentrates on the compressive bearing capacity of one composite column of a Concrete-Filled Square Steel Tube (CFSST) reinforced by a circular steel tube inside. Some tests were conducted to consider the compression behaviour of the stub columns under axial compressive loading. Through an elastoplastic limit analysis based on Unified Strength Theory (UST), the ultimate load capacity of the CFSST columns reinforced by inner circular steel tube under axial compression has been derived, which has a good agreement with the experimental results in comparison with other empirical models. So this model is extended to predict the optimal design of the inner tube, namely, Di/ti and Di/B. In addition, another simple model is also proposed to testify the optimal section of this composite column. With the optimal circular steel tubes inside the CFSST column, the composite column can result in significant savings in column size, which ultimately can lead to significant economic savings and higher bearing capacity. The results show that it has a theoretical significance and application value to adopt circular steel tube to strengthen CFSST column.
Highlights
Concrete-filled steel tube (CFST) has been applied widely in civil engineering for many years
The typical failure mode of the composite column was local failure mechanism as same as the pure concrete-filled square steel tube (CFSST) column caused by the expansion of the concrete under axial compression
Through an elastoplastic limit analysis based on Unified Strength Theory (UST), an analytical formula, capable of predicting the axial bearing capacity of the CFSST columns reinforced by inner circular steel tubes subjected to axial compression, has been developed
Summary
Concrete-filled steel tube (CFST) has been applied widely in civil engineering for many years. Jiang et al (2008) has introduced the concretefilled circular steel tubular column reinforced by circular steel tube inside, and it was concluded that the composite column could improve the compressive capacity as well as the shear capacity and ductility. This column with no more than 600 mm in diameter has been used in Wuppertal city building in German. One new model is proposed for predicting the squash load of the CFSST column reinforced by an inner circular steel tube. Concrete was in the plastic state and continually developed micro-cracks inside until the destruction of the specimen
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