构件截面形状和荷载历程对超高层建筑竖向变形的影响及机理研究

The adverse effects of differential axial shortening for high-rise buildings are enhanced with the increasing height of buildings. The current models in codes can not describe shrinkage and creep strains of concrete shear wall accurately, and the question whether Boltzmann superposition principle is appropriate for evaluating creep strains of high strength concrete is not fully resolved. According to above shortcomings, this project will be carried out as follows: Firstly, the influence of cross-section shape on shrinkage and creep of concrete will be studied, and shrinkage and creep equations of concrete shear wall will be built; Secondly, the load history of vertical components in construction will be simulated by step loading with different time and amplitude, and then the influence of load history on creep and dynamic mechanical properties of early-age high-strength concrete will be experimentally studied to build stress - strain - time coupled constitutive relation and rate-type constitutive equation; Thirdly, The interaction mechanism between aggregate and mortar will be experimentally studied, based on smart-aggregate monitoring platform, to discuss the effects of delayed elasticity and recovery on creep of concrete; Finally, the typical finite element model of high-rise building will be established to conduct axial shortening analysis considering construction process and time-varying characteristics of concrete. Furthermore, the seismic and wind performance of high-rise building with differential axial shortening are studied. The research achievement has important significance in fields of precise design, life-cycle structural performance evaluation of high-rise buildings.

随着建筑高度的不断增加，竖向变形差对结构性能的影响越来越显著。目前现行规范模型不能准确描述混凝土剪力墙的收缩、徐变变形，而且Boltzmann叠加原理适用于计算高强混凝土徐变变形的合理性还存在争论。本课题针对上述问题在以下几个方面展开系统研究：首先，研究构件截面形状对普通、高强混凝土收缩、徐变变形的影响机制，建立混凝土剪力墙构件的收缩、徐变变形预测公式；其次，研究荷载历程对早龄期高强混凝土收缩、徐变变形和动态力学性能的影响，建立早龄期高强混凝土应力-应变-时间耦合的本构关系和考虑荷载历程的率型本构关系；再次，基于压电智能骨料监测平台，探讨骨料延迟弹性及恢复对混凝土徐变变形的影响机制；最后，建立典型超高层建筑的有限元模型，对其进行考虑施工过程和混凝土时变特性的竖向变形分析，并在此基础上进行抗震和抗风性能研究。该研究对超高层建筑的精细化设计与全寿命过程结构性能评估具有重要的理论意义和应用价值。

考虑施工过程的竖向变形分析已成为超高层建筑设计、施工阶段的必要步骤，然而大多数竖向变形分析仅是从规范模型出发来预测混凝土构件的收缩、徐变变形，没有考虑到高性能混凝土材料的应用和结构体系发展所带来的原有材料模型和计算方法的局限性。本课题在以下几个方面进行了系统研究：（1）在有效厚度一致的前提下，试验研究了截面形状对普通、高强自密实混凝土的收缩、徐变变形，基于水分迁移理论对B3模型中的截面形状因子进行了修正，提高了不同截面形状下混凝土收缩、徐变模型的预测精度；（2）通过逐级加载的方式模拟了施工阶段超高层建筑竖向构件的受荷历程，试验研究了不同持时和应力幅值下高强混凝土的时变变形发展，并提出了考虑荷载历程影响的混凝土时变变形计算方法；（3）通过对相似比为1：2钢筋混凝土剪力墙构件进行长达1年的收缩和徐变变形测试，探讨了现行规范推荐收缩、徐变模型对钢筋混凝土剪力墙构件的适用性；（4）通过考虑混凝土的时变特性和结构的施工过程，对深圳某超高层建筑有限元模型的竖向变形做了分析。结合常见的6种规范模型，探讨了不同规范预测下超高层建筑竖向变形发展的区别，最后分别考虑了截面形状因子以及荷载历程因子对混凝土时变变形的影响，对结构的竖向变形进行了分析。本课题研究成果有利于更准确的模拟真实结构中不同截面形状混凝土构件的时变变形，提高了施工荷载历程下高强混凝土竖线构件时变变形的预测精度，对超高层建筑的精细化设计与全寿命过程结构性能评估具有重要的理论意义和应用价值。