罕遇地震作用下直接基于位移设计的局部预应力混凝土框架目标位移控制研究

Study on the control of target displacement in design directly based on displacement for partially prestressed concrete frames under rare earthquakes

本文针对罕遇地震作用下,直接基于位移设计的预应力混凝土框架在"防止倒塌"性能水准下结构目标位移不能有效控制的问题进行研究。通过理论分析和预应力混凝土框架结构的设计实例模拟计算,总结出影响结构目标位移有效控制的主要原因有结构承载能力超强和性能点时刻位移模式与设计位移模式误差较大两个方面。结构承载能力超强是影响框架层间位移角有效控制的主要原因,位移模式误差则是通过影响等效单自由度体系的等效目标位移而影响目标位移的有效控制。文中提出了考虑强柱弱梁调整、材料强度取值以及其他构造措施等影响的基底剪力折减计算公式,以及采用结构在性能点时刻的位移模式对设计位移模式进行修正的改进方法,算例表明目标位移和其他各项性能参数的控制均得到了非常明显的改善。

The problem that the target displacement of partially prestressed concrete frame in design directly based on displacement at performance level of ＂collapse prevention＂ can not be controlled effectively is studied. By theo- retical analysis and analog computation of PPC frames, the principal factors affecting the control of target displace- ment can be described as： the obvious ultrastrength of bearing capacity of structures and the differnee between the displacement pattern at performance point and the design displacement pattern. The obvious ultrastrength of bearing capacity of structures is the main reason that affects the control of storey drift, and the error of the displacement pat- tern affects the control of target displacement by affecting equivalent target displacement in the equivalent SDOF system. The formula for calculating the reduction factor of base shear is proposed, in which strong column and weak beam adjustment, material strength value and detail measures are taken into account; also the displacement pattern of the performance point is adopted to modify the displacement pattern. It demonstrates that the control of target dis- placement and the other parameters are improved obviously in numerical examples.