超限高层结构中小偏心受拉混凝土剪力墙名义拉应力控制方法研究

Research on nominal tensile stress controlling method of concrete small eccentric tension shear wall in out-of-code high-rise structure

超限高层结构中的混凝土剪力墙易处于小偏心受拉状态,但当前标准及文献对其名义拉应力的控制方法不同,使得设计存在一定的不确定性。从钢筋或型钢与混凝土间的界面性能、中震可修验算方法、受剪计算模式、可能的破坏模式、构件延性、截面设计等方面研究了名义组合应力控制方法和标准。结果表明:型钢对界面粘结的需求较钢筋低,会较早地参与工作从而减小混凝土部分的拉应力水平;由《高层建筑混凝土结构技术规程》(JGJ 3-2010)的方法所得名义拉应力限值对应着混凝土充分开裂而退出工作这一物理状态,属于正常使用极限状态的验算范畴;建议的名义组合应力方法适用于中震可修验算,名义拉应力方法或名义剪应力方法均为这种方法的特例,名义拉应力和名义剪应力限值在非抗震工况下可取2.5ftk和0.5ftk,在抗震工况下可取2ftk和0.4ftk;当名义拉应力达到上述限值时,宜考虑纵筋直接受剪的破坏模式,当超过上述限值时,属于承载能力极限状态验算范畴,宜计算钢筋或钢板的组合应力,同时应考虑稳定性验算。最后,以一实际工程为例,验证了名义组合应力方法的可行性。

Concrete shear wall is often under small eccentric tension in out-of-code high-rise structures,different controlling methods are used in different specifications and literatures,which lead to uncertainties of design.Nominal composite stress controlling method and criteria were discussed in terms of interface performance between rebar(steel)and concrete,check method of recoverability under moderate earthquake,shear mode,possible failure modes,member ductility,section design,etc.Several suggestions were given as follows:demand of steel for interface bond is below that of rebar,steel will be active earlier to decrease the tensile stress of concrete;nominal tensile stress method in Technical specification for concrete structures of tall building(JGJ 3—2010)is corresponding with the state of concrete crack,which belongs to serviceability limit state;the suggested nominal composite stress method may apply to recoverability check under moderate earthquake,nominal tensile stress method and nominal shear stress method are particular solutions of nominal composite stress method;the limit values of nominal tensile stress and nominal shear stress are 2.5ftk and 0.5ftk respectively under non-seismic design cases,the limit values are 2ftk and 0.4ftk respectively under seismic design cases;the failure mode that longitudinal rebar is sheared directly should be considered when nominal tensile stress reaches the above values,the composite stress of rebar or steel should be calculated when nominal tensile stress exceeds the above values,which belongs to ultimate limit state and need check the stability.Lastly,an actual engineering was utilized to confirm the feasibility of the suggested method.