UNIAXIAL LOADING TESTS AND THE CALCULATION MODEL OF THE BEARING CAPACITY FOR DOUBLE-LAYER SHOULDER BEAMS WITH DOUBLE-LIMB MIDDLE COLUMNS OF CONCRETE-FILLED STEEL TUBES

Targeted at a new type of double-layer shoulder beams with double-limb middle columns of concrete-filled steel tubes (CFST), the failure process, failure mode and strain distribution of two specimens were studied by in-plane uniaxial loading test. The results showed that under the action of horizontal forces, most of the load was transferred to the lower shoulder beam of specimens, and finally shear failure occured at the grid web in the compression zone of the lower shoulder beam. The ductility of specimens was excellent, and the horizontal bearing capacity of specimens largely depended on the section of the web for the lower shoulder beam; the shear strain was mainly controlled by the upper and lower webs of the shoulder beam for specimens, and the strain distribution near the weld joint was different from that obtained by theory. The strain concentration existed at the flange of the shoulder beam. Based on the analysis results, the calculation model and formula for the horizontal bearing capacity of the double-layer shoulder beam with double-limb middle columns of concrete-filled steel tubes were proposed.