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

Due to the special structure of double-layer shoulder beams with triple-limb middle columns, the internal force distribution is different from that of double-layer shoulder beams with double-limb or quadruple-limb middle columns. To construct the calculation formula of horizontal bearing capacity of double-layer shoulder beams with triple-limb middle columns, 42 models were designed on the basis of tests and finite element study. The key parameters influencing the horizontal bearing capacity of double-layer shoulder beams with triple-limb middle columns were analyzed by finite element method. The section height ratio of upper layers to lower layers (the height ratio), section height ratio of middle columns to lower layer shoulder beams (the column-beam height ratio) were discussed, the influence of the span-height ratio of the lower shoulder beam (the span-height ratio) on the horizontal bearing capacity of double shoulder beams with three-limb middle columns was studied. The characteristic bearing capacity and displacement of the model were analyzed, and the range of parameters was given. The results showed that the height ratio had little effect on the bearing capacity of the model; the larger the height ratio of the column and beam was, the greater the characteristic bearing capacity was; the larger the span-height ratio was, the greater the bearing capacity of the model was, but the faster the bearing capacity decreased in the later stage. Based on the analysis results, three failure modes and horizontal bearing capacity formulas of the double-layer shoulder beam with triple-limb middle columns were proposed, and the error of the formula was corrected based on the ductile failure of the model.