Bearing Capacity Calculation Method Of Pre-stressed Pre-cast Concrete Frame

Prestressed precast concrete（PPC） frame systems composed of precast beams andcolumns of being sent to sites and installed by stretching prestressed bars through reservedholes to form an integral stress system at construction sites, overcomes some kind ofshortcomings caused by the poor reliabilities of node connections in precast structures andthe inability of stress requirements under cyclic loads, improves the overall structuralseismic performance with satisfactory deformation and energy dissipation capacity.Based on a test of PPC frame, Considering the effect of the semi-rigid joints, thispaper established the internal force analysis model of the PPC frame under a vertical load,simulated the semi-rigid joint connection in the form of the helical spring to develop thebeam element stiffness matrix due to different relative rotation stiffness of the joints atbeam end, and then, made a loaded analysis on the testing frame. The research indicatesthat the beam end of the PPC frame had a somewhat lower moment under the influence ofthe semi-rigid joints. Compared with the simulation of rigid joints, the beam end moment ismore approximate to the actual state and experimental results.An experimental study of one-layer two-span PPC frame with the consideration ofnode semi-rigid effect analyzed the influence elements of ductility factors, derived theexpressions of yielding and ultimate curvatures, and computed the ductility factors incomparison with experimental results at the beam-end sections of PPC frame. Based on atest of two-story double-span PPC frame and considerations for the influence of semi-rigidnodes and the limits of crack width, the ductility factor and limit value of momentmodification with satisfaction to the bearing capacity and operation requirements at thebeam-end sections of PPC frame were deduced for its future theoretical design basis by therecommended limit value formulas and coefficient limits of moment modification. Also,destruction status under different loads at the frame beam-end was analyzed to initiate acalculation method of bearing capacity at the beam-end sections of PPC frame, whichoffers a complete theoretical basis for engineering applications.