Development of New Method and Its Application Software for Numerical Analysis of Dynamic Fracture Process of Reinforced Concrete

本文旨在阐明近源地震中钢筋混凝土结构局部开裂、发展和钢框架脱落的机理。这些断裂过程受到近源地震引起的初始强运动的影响。1998-1999年，基于离散元法的二维数值分析软件被开发出来，用于阐明这些断裂过程。对一些简单的动力问题进行了分析验证，并与以往的分析结果和其他通用程序的计算结果进行了比较，证实了计算的准确性。采用动力有限元法对实例进行了数值分析。以t型和门型桥墩为例，研究了桥墩的振动问题。在2000-2001年期间，将开发的软件扩展到能够处理三维问题，并对计算的准确性进行了检验。前后处理部分和数值计算部分分别用Visual c++和FORTRAN编程，各功能都有较大的增强。在预处理部分，实现了用对话框编写的分区重划功能，使负载、限制等条件的设置变得非常容易。通过与另一个通用有限元程序的配合，实现了对大规模问题的分析。基于动态有限元方法的数值分析也不断进行。对尼尔森桥型桥梁支座和高层建筑箱形柱的脆性断裂进行了研究。数值计算结果表明，脆性断裂很可能是由动载荷引起的。

It is desired to clarify the mechanism of local cracking, its development and falling out of steel frame in the RC structure at near-source earthquakes such as the great Hanshin-Awaji earthquake. These fracture processes are affected by the initial strong motion due to near-source earthquake. At the term 1998-1999, an all-purpose software for 2-dimensional numerical analysis, which is useful for clarifying those fracture processes, was newly developed based on the discrete-element method. Some analyses of simple dynamic problems were conducted for verification, and the calculation with good accuracy was confirmed by the comparison with the past analytical results and those obtained by other all-purpose programs.The numerical analyses for case study were also conducted by the dynamic finite-element method. For example, the uckling problems of T-type and Gate-type bridge piers were investigated.At the term 2000-2001, the developed software was extended to be able to deal with 3-dimensional problems, and the accuracy of calculation was also examined. The pre/post-processing parts and the numerical calculation part were programmed by using Visual C++ and FORTRAN, respectively, and each function was enhanced greatly. In the pre-processing part, the rezoning function written in dialogue was realized, and the setting of conditions such as load, restriction etc. become very easy. The analysis of large-scale problem was realized by the cooperation with another all-purpose finite-element code.The numerical analyses based on the dynamic finite-element method for case study were also conducted continuously. The brittle fracture of the bridge bearing of the Nielsen bridge type and that of the box column of the tall-building were investigated. The obtained numerical results show a high possibility that the brittle fractures were caused by dynamic load.