Research On The Failure Mechanism Of Reinforced Concrete Frame Structure

In recent years, with the rapid development of economy of China, a large numberof buildings were built all over the country. Frame structure which is a basic form ofstructures was still used widely. Therefore, it is more and more being taken seriouslyon the seismic performance of the frame which is an important indicator on measuresafety of the structure. In order to ensure structures are safe when under earthquakecase, the seismic code of our country gives mandatory requirements on relevantparameters which can be used during structure design. The aims of these mandatoryrequirements are making sure the structure can reach ductile failure The forming ofplastic hinges can consume seismic energy. To make sure the structure can own theproperty of good ductility, the plastic hinges of structure should have a process ofdevelopment and change.However, most of damage survey shows the failure modes of destroyed structuresin earthquake zoon doesn’t follow what we expected when designing buildings; theydon’t follow the failure mode of “Weak Beam Strong Column”. On the contrary, mostcolumns of structures are severely damaged and even tilt or become into swaymechanism between lays which leads to partial varicable mechanism and eventuallylead to integer collapse. Compare to the damage of frame column, beam damage bringsmaller destroy. There’re three reasons on this kind of structure failure mode:1) Thequality of construction cannot be guaranteed for the local poor economic condition.2)The design of structures are not follow the national norms strictly.3) Lack ofconsideration of design assumptions, such as ignore the stiffness of infill walls.A structure is built in this paper. The structure is a office building in the city ofTianjin. Using structure design software according to the provisions of national normscalculates the reinforcement. Calculate the plastic hinges at the ends of componentsdirectly by Section Builder. Enter the model designed by PKPM into SAP2000whichis finite element structural analysis software. Do Push-over analysis and Dynamicanalysis on the model, obtain the development and change process of plastic hinges.There’re4different load cases applied to the structure. Specific load cases are bellow.Case1: Gravity load+Acceleration on X direction. Case2: Gravity load+Acceleration on Y direction. Case3: Gravity load+Mode1(transverse). Case4:Gravity load+Mode1(longitudinal). The order of creating plastic hinges is from thebeam ends in the first floor to the ends of columns then spread to the whole structure.Dynamic analysis shows that plastic hinges appear at the beam ends first which isnearly the same as the result of Push-over analysis.