下弦与撑杆新构型张弦梁结构的抗连续倒塌性能

Progressive collapse resistance of beam string structure based on a new configuration of bottom chord and strut

由于传统张弦梁结构冗余度较低,下弦预拉索遭受意外作用断裂时易导致结构发生连续倒塌。通过改进传统张弦梁撑杆、下弦等杆件构型与连接形式,提出一种新型张弦梁结构。基于ANSYS/LS-DYNA程序平台,采用考虑初始状态的等效荷载瞬时卸载法,对具有不同撑杆交叉角度和交叉撑杆组数量的多个新型张弦梁结构模型进行抗连续倒塌分析。结果表明:合理设计后,任一段下弦失效时,交叉撑杆将代替失效处下弦为结构提供备用传力路径,新型张弦梁结构不会发生连续倒塌,但会导致下部撑杆内力骤增,下部撑杆设计需预留较大承载余量;撑杆交叉节点越靠近下弦,剩余结构空腹桁架作用越明显,承载能力越好;交叉撑杆组数越多,结构冗余度越高,新型张弦梁结构抗连续倒塌性能越优。

Due to the low redundancy of the traditional beam string structure,it is easy to cause a continuous collapse of a structure when the lower string prestay cable is broken by accident.A new type of beam string structure is proposed by improving the traditional tensioned beam spars,lower chords and the connection forms among members.Based on ANSYS/LS-DYNA program platform,some new beam string structure models with different spars crossover angles and spars numbers are analyzed for continuous collapse resistance by using the instantaneous unloading method of the equivalent load in the initial state.The results show that after reasonable design,the cross strut will replace the lower chord at the failure to provide a spare force transmission path for the structure when any section of the lower chord fails,and the new beam string structure will not progressive collapse,but the lower spar internal force will increase suddenly,the large bearing allowance shall be reserved for the design of the lower brace.And also show that the closer the brace cross node is to the bottom chord,the more obvious the effect of the vierendeel truss of the remaining structure and the better the load carrying capacity.The more cross brace groups,the higher the structural redundancy,and the better the progressive collapse resistance of the new beam string structure.