Concrete Filled Double Skin Tubular Deep Beam Having Outer Circular and Inner Square Sections under Bending-shear

The present study aims to investigate experimentally mechanical behavior of CFDST deep beam having an outer circular section and an inner square section (CS-CFDST) under bending-shear through asymmetric four-point loading testing method. Two selected test parameters are inner square width to outer circular diameter and the large diameter-to-thickness ratios of the steel tubes. As the results, observed failure modes were shear failure of in-filled concrete or outer tube's cracking at the position of maximum bending moment. Method to predict bending-shear capacities of CS-CFDST deep beam is mainly discussed. Furthermore, biaxial stress behavior of outer circular steel tube based upon elasto-plastic theory under plane stress conditions is also mentioned.