有初应力的钢管混凝土轴压柱设计计算方法研究

应用有限元计算方法,对有初应力的钢管混凝土轴压柱容许应力法和极限状态法中所对应的弹性极限荷载和塑性或稳定极限荷载进行了数值计算分析.分析表明,一般情况下钢管与管内混凝土不可能同时达到容许应力.传统的容许应力法计算的弹性极限荷载连两种材料的弹性极限荷载的简单叠加都无法达到,更不用说组合作用使承载力提高的部分了,因此,它存在着明显的不合理之处.建议定义钢管混凝土轴压构件弹性极限荷载为钢管的最大应力达到屈服应力时所对应的荷载.初应力的存在使构件弹性极限承载力下降明显,而对塑性或稳定极限荷载的影响相对不大.初应力度越大,构件弹性极限承载力与其塑性或稳定极限承载力的比值越小,以弹性极限荷载为控制的容许应力法计算结果越保守.对于钢管混凝土拱桥,其初应力度一般较大,设计计算建议采用极限状态法.

Research on design and calculated methods of concrete filled steel tube columns with initial stress under axial loads

Applying finite element method,the elastic ultimate load and plastic or stability ultimate load corresponding to the allowable stress method and ultimate state method of concrete filled steel tube(CFST) columns with initial stress under axial loads are calculated and analyzed.Results indicate that it is impossible for the steel and concrete stresses reaching their allowable stress simultaneously in generally,but the stress of steel is more feasible for the checking stress than the concrete's for the suited match of CFST.It can be regarded as the elastic ultimate load when the moment of the steel tube is yielded.The allowable stress method for calculating elastic ultimate load of members and structures of CFST is irrational in practice engineering.The presence of initial stress drops the elastic ultimate load more distinct than the strength and the ultimate load-carrying capacity.The ratio of elastic ultimate load to plastic ultimate load is decreased with the increasing of initial stress degree(ISD) and allowable stress method is conservative.As to the CFST arch bridge with large ISD,the ultimate state method is suited to use in practical engineering.