BEARING CAPACITY ANALYSIS AND CALCULATIONS OF DOUBLE-LAYER SHOULDER BEAMS WITH MULTI-LIMB MIDDLE COLUMNS OF CONCRETE-FILLED STEEL TUBES

In order to construct the calculation formula for the horizontal bearing capacity of double-layer shoulder beams with double-limb or quadruple-limb middle columns of concrete-filled steel tubes (CFST). Based on the results of previous tests and finite element simulations, 43 and 44 models of two kinds of double-layer shoulder beams were designed respectively. From the aspects of characteristic bearing capacity and displacement of the models, the section height ratio (the height ratio) of the upper layer to lower layer shoulder beams, the section height ratio of middle columns to lower layer shoulder beams (the column-beam height ratio), and the ratio of the long span or short span to the height of the lower shoulder beam (the span-height ratio) were analyzed, and the range of the parameters was given. The results showed that the horizontal bearing capacity of the two kinds of double-layer shoulder beams was similar in the change of parameters; with the increase of the height ratio of columns to beams, the model stiffness increased, the yield displacement decreased, and the bearing capacity increased in a parabola; with the increase of the span-height ratio, the bearing capacity of the model increased linearly, but the ductility became worse; with the increase of the ratio of the short span to the height, the flange area of the model for the double-layer shoulder beam with four-limb middle column increased, and the bearing capacity would increased slightly. Based on the results of parameter analysis, the load-shared proportion in each section was determined, and the formula for calculating the horizontal bearing capacity of the model was proposed, and the formula was modified based on the ductile failure.