Axial compression capacity of circular CFST columns transversely strengthened by FRP

Abstract

Fiber reinforced polymer (FRP) jackets have been recently used for strengthening purpose of concrete filled steel tube (CFST) composite columns and also for the suppression of outward local buckling that CFST columns may suffer. This study intends to investigate the axial compression capacity of circular CFST columns transversely strengthened by FRP. For this, an attempt has been made to implement gene expression programming (GEP) technique for the development of axial capacity of confined CFST prediction model. The database required for the derivation of the GEP model is based on the extensive experimental results of the FRP confined CFST columns tested in compression (92 test specimens). Moreover, these test specimens wrapped with the carbon or glass fiber sheets have different length to diameter ratios of 2.0–4.5. The input predictor variables used in the study are the properties of the FRP (the type, thickness and sheet wrap layers, tensile strength and elastic modulus of FRP), the steel tube (outer diameter, thickness, length and tensile strength of steel tube) and unconfined concrete (compressive strength of in-filled concrete). To verify the effectiveness of the model, the values from GEP were examined statistically against those of existing equations given by various researchers. After analyzing and comparing the proposed model with the existing formulas, it was found that the results obtained by GEP have significantly less errors and far more accurate.