次边缘柱失效下预应力混凝土框架抗连续倒塌性能研究

PROGRESSIVE COLLAPSE PERFORMANCE OF PRESTRESSED CONCRETE FRAMES UNDER PENULTIMATE COLUMN REMOVAL SCENARIO

考虑到去柱后弯矩方向在去柱处出现反转并且可能与预应力筋布置形式相反,预应力混凝土结构具有较大的倒塌风险,该文通过拟静力试验和数值模拟研究了次边缘柱失效下无黏结预应力混凝土(PC)梁-柱子结构的抗连续倒塌性能。对2个具有不同预应力筋布置形式(直线型和抛物线型)的1/2缩尺梁-柱子结构进行Pushdown加载,分析了试件的破坏模式、抗力机制演变和极限承载力。为量化预应力筋的影响,制作了一个具有相同几何尺寸和非预应力筋配筋率的钢筋混凝土试件作为参考。结果表明:预应力筋可以显著提高结构承载力,同时改变结构的破坏模式,降低结构变形能力。预应力筋产生的水平拉力加剧了边柱的挠曲P-δ效应,使边柱提早发生大偏心受压破坏。为进一步了解预应力混凝土框架抗倒塌性能,基于有限元软件LS-DYNA建立了精细化有限元模型开展系列参数分析。数值分析表明,预压应力可以增强压拱机制,预应力筋对于大变形阶段承载力的提高贡献显著。

Considering that the direction of bending moment at the beam end nearby the removed column will reverse,which may disagree with the profile of prestressing strands.Thus,the prestressed concrete frame may have high vulnerability for progressive collapse.In this study,experimental and numerical studies were performed to study the performance of unbonded prestressed concrete(PC)beam-column sub-assemblies subjected to a penultimate column removal scenario to resist progressive collapse.Two half-scale PC beam-column subassemblies with different strand profiles were tested by Pushdown loading procedure.Failure modes,the involution of load resisting mechanisms,and ultimate load resistance were analyzed.To quantify the effect of the strand,a non-prestressed reinforced concrete beam-column sub-assembly was designed,the geometrical dimension and reinforcement ratio of which were consistent with the PC beam-column sub-assemblies.It is found that the presence of the strand leads to a greater load resistance,lower deformation capacity and different failure modes.The considerable tension in the strand cause significant second-order effects in the side column,leading to large eccentric compression failure.To further study the performance of PC frames against their progressive collapse,high-fidelity numerical models built by LS-DYNA were used to conduct a series of parameter studies.It is found that prestress forces can increase compressive an arch action.The strand can significantly enhance the ultimate load resistance at a large deformation stage.