利用动力有限元程序LS —DYNA，对纽约世界贸易中心受飞机撞击后的倒塌，进行了力学分析和仿真，并根据计算结果进行了参数讨论。仿真计算的结果与真实倒塌过程非常接近，说明通过适当的选取计算参数和计算模型，可以对这种特殊的复杂破坏过程进行模拟分析和仿真。计算结果说明，世界贸易中心倒塌的直接原因，是火灾导致的钢材软化和楼板塌落冲击荷载引起的连锁反应。如果能够提高结构的抗火能力或者提高结构的延性, 将有可能避免结构倒塌，避免惨剧再次发生。

External bonding of fiber-reinforced polymer (FRP) plates or sheets has recently emerged as a popular method for the strengthening of reinforced concrete (RC) structures. The behavior of such FRP-strengthened RC structures is often controlled by the behavior of the interface between FRP and concrete, and this interfacial behavior is commonly studied through a pull test in which an FRP sheet or plate is bonded to a concrete prism and is subject to tension. In this paper, a meso-scale finite element (FE) model implemented with the MSC.MARC program is presented for the simulation of interfacial debonding failures in a pull test. In this model, very small nearly square elements (0.25–0.5 mm in size) are used with the fixed angle crack model (FACM) to capture the development and propagation of cracks in the concrete layer adjacent to the adhesive layer. The effect of element size is taken into account in modeling both the tensile and shear behavior of cracked concrete. Comparisons between the predictions of this model and test results are presented to demonstrate the capability and accuracy of this FE model. The debonding mechanism is also examined using results obtained with the FE model. Finally, a method for the determination of the local bond–slip curve of the FRP-to-concrete interface from the FE results is described.

An accurate local bond–slip model is of fundamental importance in the modelling of FRP-strengthened RC structures. In this paper, a review of existing bond strength models and bond–slip models is first presented. These models are then assessed using the results of 253 pull tests on simple FRP-to-concrete bonded joints, leading to the conclusion that a more accurate model is required. In the second half of the paper, a set of three new bond–slip models of different levels of sophistication is proposed. A unique feature of the present work is that the new bond–slip models are not based on axial strain measurements on the FRP plate; instead, they are based on the predictions of a meso-scale finite element model, with appropriate adjustment to match their predictions with the experimental results for a few key parameters. Through comparisons with the large test database, all three bond–slip models are shown to provide accurate predictions of both the bond strength (i.e. ultimate load) and the strain distribution in the FRP plate.

The behaviour of reinforced concrete (RC) structures strengthened with externally bonded fibre-reinforced polymer (FRP) reinforcement in the forms of thin plates or sheets is often dominated by debonding of the FRP reinforcement from concrete. As a result, a large number of studies have addressed debonding failures in FRP-strengthened RC structures, with many of them being focussed on understanding the behaviour of simple FRP-to-concrete bonded joints in which an FRP plate/sheet is bonded to a concrete prism and is subject to a tensile force. Despite the many existing studies, there are still substantial uncertainties and difficulties with the finite element modelling of debonding failures due to the complex behaviour of cracked concrete. This paper explores the use of different crack models in modelling and compares their predictions of the debonding behaviour of FRP-to-concrete bonded joints. The results presented in this study show that a non-coaxial rotating angle crack model (RACM) is required to accurately predict this debonding behaviour. Furthermore, the debonding mechanism is also examined using results obtained with a nonco- axial RACM.

结构在大震作用下会进入非线性并产生损伤，准确预测地震荷载下钢筋混凝土结构的非线性行为，对评估混凝土结构的抗震安全性具有重要意义。清华大学土木工程系近年来开发的适用于钢筋混凝土杆系结构的纤维模型THUFIBER 程序，适用于预应力混凝土杆系结构的纤维模型NAT-PPC 程序，以及适用于剪力墙结构的分层壳墙元模型的非线性分析程序。这些程序可以直接将构件的非线性节点力(轴力、剪力和弯矩)、节点变形(平动和转动)和材料的非线性应力-应变行为联系起来，可以模拟各种复杂受力构件的滞回行为和轴力－双向弯曲－剪切耦合行为，借助通用有限元程序方便的前后处理功能和非线性计算功能，该程序可以准确模拟地震作用下结构的三维非线性地震响应，也可模拟爆炸、倒塌等极端非线性行为，通过一系列的数值分析与试验结果的对比和工程应用算例，说明所研发程序的精度和计算能力。

结构的连续倒塌已成为严重威胁公共安全的重要问题。国外自1968年英国Ronan Point公寓倒塌事件发生以来，已经对连续倒塌问题进行了30余年的研究，并编制了相关设计规范，而我国规范目前尚未规定详细抗连续倒塌设计方法。参考美国国防部编制的《结构抗连续倒塌设计》（DoD2005）提供的设计流程，对按照我国现行混凝土结构设计规范设计的3层钢筋混凝土框架进行了连续倒塌仿真，分析了其抗连续倒塌能力。并应用拉结强度法和拆除构件法，对该框架进行了抗连续倒塌设计，建立了将国外规范中的抗连续倒塌设计方法应用于我国框架结构的设计实例，指出了其中存在的一些问题。

超高车辆和立交桥梁之间的碰撞事故屡见不鲜，深入研究车2桥碰撞机理，为提出车2桥碰撞桥梁损害计算方法奠定基础，具有重要的现实意义。基于高性能非线性有限元，对超高车辆2立交桥碰撞进行了高精度仿真分析，并对不同车速导致的桥梁损害情况进行了讨论。分析结果可为深入研究车2桥碰撞问题提供参考。

大型高架桥梁是城市交通的重要生命线工程,准确预测高架桥(高架桥体系) 在地震下的破坏模式,对减灾、救灾工程有着重要意义。本文基于高性能并行计算和非线性分析,对大型高架桥梁的破坏进行了模拟,并考虑了地震行波效应、桥墩塑性铰、上部结构落梁等多种破坏模式。计算结果表明,本文建议模型可以真实模拟大型高架桥梁的地震破坏。并对主要参数的影响加以讨论,为深入研究高架桥梁体系在地震灾害下的破坏模式和安全状况提供依据。

准确预测地震荷载下钢筋混凝土柱的受力性能，对评估震后混凝土框架结构及桥梁结构的安全性和震害损失具有重要意义。由于复杂的材料性能和受力行为，地震作用下钢筋混凝土柱受力性能的准确计算目前仍需主要借助数值模拟，并且对数值模型中混凝土和钢筋材料的滞回本构关系提出了更高的精度要求。该文基于纤维分析模型，采用更加完善的反复荷载下钢筋和混凝土的本构，编制了可精确分析钢筋混凝土杆系结构及构件在往复荷载下受力性能的计算程序，并对不同轴压比和不同配筋率的2 根压弯柱试件进行了数值模拟，计算结果与试验结果吻合良好。

Reinforced concrete (RC) beams strengthened in flexure with a bonded fiber-reinforced polymer (FRP) plate may fail by intermediate crack (IC) debonding, in which debonding initiates at a critical section in the high moment region and propagates to a plate end. This paper first presents a finite-element (FE) model based on the smeared crack approach for concrete for the numerical simulation of the IC debonding process. This finite-element model includes two novel features: (1) the interfacial behavior within the major flexural crack zone is differentiated from that outside this zone and (2) the effect of local slip concentrations near a flexural crack is captured using a dual local debonding criterion. The FE model is shown to be accurate through comparisons with the results of 42 beam tests. The paper also presents an accurate and simple strength model based on interfacial shear stress distributions from finite-element analyses. The new strength model is shown to be accurate through comparisons with the test results of 77 beams, including the 42 beams used in verifying the FE model, and is suitable for direct use in design.