柱端弯矩增大系数对PC框架结构抗震性能影响的研究

Study on the Effects of Moment Magnifying Coefficients at Column Ends on the Seismic Capacity of Prestressed Concrete Frame

根据我国现行《预应力混凝土结构抗震设计规程》(JGJ 140-2004),以设防烈度为8度(0.2g)地区的多跨多层预应力混凝土框架结构柱端弯矩增大系数为研究对象,对其合理取值问题进行了探讨.在SAP2000与PERFORM-3D软件中,采用局部纤维铰梁单元,对6个PC平面框架建立了弹塑性分析模型,并对其进行了静力弹塑性分析(Pushover分析)与动力弹塑性时程分析.计算结果表明:按照现行规范设计的PC框架,基本上可以满足8度区罕遇地震作用下的抗震要求,但是结构在大震作用下形成的是以底层柱端出铰为主的梁柱铰屈服机制,对结构抗震不利;随着柱端弯矩增大系数的增加,结构的局部构件抗震性能以及屈服机制均有很大程度的改善,当边柱和中柱的柱端弯矩增大系数分别增加到2.0,1.8时,预应力混凝土框架结构能够实现对结构抗震有利的以梁出铰为主的梁柱铰屈服机制,甚至是梁铰屈服机制.因此,建议在进行预应力抗震技术规程的修订时,适当提高框架结构柱端弯矩增大系数的取值.

According to the current code for seismic design of prestressed concrete structures（JGJ140-2004）,this paper discussed the problem of reasonable value about moment magnifying coefficients at column ends of multi-layer prestressed concrete frame structure in the 8degrees（0.2g）seismic grade district.Six elasto-plastic analysis models with different moment magnifying coefficients at column ends based on local fiber hinge beam element were established in SAP2000 and PERFORM-3Drespectively,and the static elasto-plastic analysis（Pushover）and dynamic elastic-plastic analysis were proceeded.The analysis results show that PC frame designed by the current aseismic codes forms the beam-column hinge hybrid yield mechanism,in which column hinge occupies the priority,adverse to the earthquake.As the moment magnifying coefficients at column ends increased gradually,the seismic performance of local components and yield failure mechanism of structure showed significant improvement.If the moment magnifying coefficients of middle and side columns separately increased at 2.0and 1.8,PC frame can form beam-column hinge hybrid yield mechanism,in which beam hinge or even beam hinge yield mechanism occupied the priority,favorable to the earthquake.Therefore,suggestions were given to improve appropriately the moment magnifying coefficients at the frame column end in the revision of code for seismic design of prestressed concrete structures.