The Resistance To Progressive Collapse Of Frame Structures With Different Aseismic Levels

In recent years,increasing attention has been paid to the performance and design method about resistance to progressive collapse.Research abroad in this field have been carried out for over 40 years and large numbers of achievements have been accomplished,many of which have been codified.The study conducted by Chinese researchers is also reflected in code provisions.In 2014,the first Chinese design code to resist progressive collapse CECS392 was released,which provided the basis for the design method of resistance to progressive collapse of structures.In addition,the newly revised code GB50010-2010(2015 Edition)and the code JGJ 3-2010 also include the provisions on the resistance to progressive collapse of structures.Using the nonlinear finite element analysis program SAP2000,multi-layer 3Dframe models of different structure types and with different seismic intensities reestablished in this study.By removing components,analysis is carried out on the progressive collapse performance of different floor columns under vertical load,which provides a reference for the practical design method to resist progressive collapse.The main work and conclusions of this study are as follows:1.Literature review about the design codes to resist progressive collapse is given and comparison is made between Chinese and American codes.2.The design method to resist progressive collapse is introduced in detail.Emphasis is put on the introduction of the design procedure of the alternative path method.The flow chart of the nonlinear static analysis is given and the implementation of the column removal in SAP2000 is explained.3.In accordance with the code CECS392(2014 Edition),YJK software is used to design the inner-corridor-type,gallery-type,equal-span multi-layer frames with seismic intensity of 8 and safety class of 1as well as seismic intensity of 8/7.5/7/6 and safety class of 2,following the 3-level seismic design concept.Under the condition of satisfying the requirements for the overall index of the structure(such as period ratio,drift ratio and displacement ratio,etc.)and for the reinforcement ratio,the static nonlinear method is used to investigate the progressive collapse performance of those models.For each model,the following failure positions are considered:Corner columns in the bottom,the middle and the top floor,middle columns in the long side and short side and the middle column.4.The resistance to progressive collapse of frame structures at different seismic levels are analyzed and compared in terms of the volume of concrete and steel,the state of plastic hinges of beams and columns and the maximum vertical displacement at the failed columns.5.According to the results,it is found that in addition to the corner columns,the inner-corridor-type,gallery-type frames with seismic intensity of 8 and safety class 1and 2 have certain resistance to progressive collapse.The resistance to progressive collapse of the frame with seismic intensity of 6/7safety 2 is the least,hardly having resistance to progressive collapse.