Study on the Effect of Over-strength Caused by Casting Slab on the Moment Bearing Capability of Beam for Reinforced Concrete Frame Structures

By analyzing the failure model of various reinforced concrete frame structures in earthquake,it shows that the failure mechanism of strong column and weak beam expected could not achieve for a lot of casting reinforced concrete frame structures.Based on the effect of casting slab on the moment bearing capability of beam in reinforced concrete frame structures,the mechanism on the effect of the over-strength caused by casting slab on the negative moment bearing capability of beam end is studied.By analyzing an actual example according to design codes,it shows that although the increasing coefficients of moment of column end are enhanced in GB 50011-2010 code for seismic design of buildings,GB 50010-2010 code for design of concrete structures,and JG J3-2010 technical specification for concrete structures of tall building and higher ratios of reinforcement were used,the mechanism of strong column and weak beam cannot be surely achieved.In conclusion,some suggestions for structural design are given for reinforced concrete frame structures,such as how to strengthen bending moments at the ends of column,to calculate real negative bending moments at the ends of beam and so on.