对角斜筋小跨高比超高韧性水泥基复合材料剪力墙连梁的抗震性能

Aiming at insufficient ductility, difficult construction and severve damage in short span-depth ratio coupling beam when subjected to strong earthquake action, the current project will present a new diagnoally-reinforced short span-depth ratio coupling beam with ultrahigh toughness cementitious composite. It is believed that the ability of ultrahigh toughness cementitious composite to undergo larger deformation can improve ductility, shear capacity and energy dissipation of conventional concrete coupling beam, reduce the amount of stirrups as well as eliminate the problems of congested detailings and the poor concrete casting quality. Low-cycle tests, theoretical analysis based on stru-and-tie model and nonlinear finite element simulation are carried out on the proposed new coupling beams and conventional ones. The main concerns are to understand the dominant force transition mechanisms, failure mechanis as well as their influencing trends with span-depth ratio. Besides, the present project is also for the purposes of finding out the influences of span-depth ratio, shear-compression ratio and the amount of stirrups on seismic performance of the new developed coupling beam, constructing shear prediction equation, suggesting the allowable values of the maximum shear-compression ratio and the mimimun amount of stirrups saved by ultrahigh toughness cementitious composites. The resluts of this project will provide a new solution to coupling beam with the advantages of easy construction, high ductility, high energy dissipation and low damage, which is of significances for guiding the design of practical engineerings.

针对小跨高比联肢墙连梁在遭受强震下抗剪延性不足、施工复杂及破坏严重等问题，提出一种对角斜筋超高韧性水泥基复合材料新型抗震连梁，利用超高韧性水泥基复合材料优异的非线性变形能力，提高小跨高比连梁的抗震延性、抗剪承载力和耗能，同时减少连梁箍筋用量，解决配筋过密造成的混凝土浇筑不密实问题。采用低周反复载荷试验、拉杆-压杆理论和有限元数值模拟相结合的研究方法，对该新型连梁和普通混凝土连梁的抗震性能进行研究，以期揭示该新型连梁的主要传力机制和耗能破坏机理及其随跨高比的影响规律，获得跨高比、剪压比和配箍特征值对该新型连梁抗震性能的影响关系，建立小跨高比对角斜筋超高韧性水泥基复合材料连梁抗剪设计的实用计算公式，提出剪压比最大允许限值，提出该新材料可取代的最小配筋量。研究成果可为小跨比连梁在高剪压比下实现施工简单、高延性、高耗能及低损伤提供一种新技术途径，为工程设计提供科学依据，具有重要的学术和工程意义。

连梁是剪力墙体系中一个重要的耗能部件，它除了能连接墙肢外，还能约束墙肢，利用其梁端的塑性变形能力来耗散地震能量，减轻甚至避免墙肢底部结构过早发生破坏。但由于建筑开洞的尺寸限制，连梁往往具有跨高比小、剪压比高的特点，即使在密布箍筋下也难以满足我国现行《混凝土结构设计规范》（GB50010-2010）和《高层建筑混凝土结构技术规程》（JGJ3 -2010）规定的剪压比限值，在遭受强震下往往易于过早发生剪切破坏，导致联肢墙体系抗震延性不足及破坏严重、可修复性差等问题。为此，本项目将超高韧性水泥基复合材料代替普通混凝土应用于联肢剪力墙抗震连梁，以规范采用的对角斜筋和综合斜筋作为连梁的主要抗剪配筋形式，采用自行设计的纯剪试验装置针对跨高比为1.0、1.25和1.5三种跨高比共计17个连梁进行了低周往复抗震试验，分析了跨高比、斜筋/箍筋配筋强度比以及斜筋/菱形筋配筋强度比、纵筋配筋率等参数对连梁抗震性能的影响，同时对连梁的地震损伤进行了评估，最后采用拉杆-压杆理论对比分析了超高韧性连梁的非线性受力全过程。结果表明，超高韧性水泥基复合材料连梁较普通混凝土连梁有着高的抗剪承载力、延性性能和耗能能力，且震后的可修复性高，即使在远低于规范最小配箍率要求且对角斜筋不加设拉筋下延性系数依然能够大于3.0，可以将规范限定的剪压比上限从0.20放宽到0.25，给出了超高韧性连梁的损伤指标并划分了损伤状态等级，提出了修正的损伤评估模型。通过试验与数值的对比分析，验证了连梁的非线性分析理论，考虑了连梁压杆的压缩和转动以及压缩软化，最后基于拉压复合提出了连梁抗剪承载力计算公式。研究成果可为小跨高比连梁在高剪压比下实现施工简单、高延性、高耗能及低损伤提供一种新的技术途径，为后续工程推广应用提供了科学技术支撑，具有重要学术和工程意义。