Applications And Redevelopments Of Object-Oriented And Open-Sourced Program OpenSees On RC Structure Nonlinear Analysis

Numerical simulation acts as a significant role in civil engineering. Recent several decades, many powerful structure finite element analysis programs have been developed, which, as an important complement of experimentation, are widely used to simulate or predict structure responses under external loads or earthquake excitations.However, most existing finite element software packages are developed in procedural-based programming languages. These packages are normally monolithic and difficult for a programmer to maintain and extend. On the other hand, object-oriented design principles and programming techniques can be utilized in finite element analysis programs to support better data encapsulation and to facilitate code reuse. For these reasons, object-oriented techniques are becoming one of the main directions in the developement of programming design. In addition, common structural analysis softwares often accumulate their programming codes inside which, in fact, obstruct end-users' redevelopement on these software procedures. Free software is issued and rapidly developed for solving this problem. This new kind software complies with Open-Source principle and put it's partial or whole internal codes open to everyone. By open and free communication and interaction of procedure developers and end-users, free software can have unbelievable update velocity and gradually become a new trend in software engineering.Such a structural analysis package OpenSees, which is object-oriented and Open-Sourced, is deeply described in this paper. OpenSees is a software framework for developing applications to simulate the performance of structural and geotechnical systems subjected to earthquakes and is under continual development.The fist part of this paper is about structure models and commands supported by OpenSees, and corresponding contents are the basis of application and redevelopement on this software. Trational stiffness-based beam-column element is based on displacement interpolation fuctions which often fail to simulate the exact responses when structure enters seriously nonlinear period, while flexibility-based element adopts force interpolation functions which reproduce element internal forces in a strict sense even into nonlinear period. In OpenSees procedure how to incorporate flexibility-based beam-column element into traditional FEA code is introduced in this paper. With necessary modification of OpenSees, these two nonlinear beam-column elements are then combined with fiber section to analyze several plane problems. The third part of this paper mainly contrast OpenSees with another existing procedure and conclude with that new FEA package is suitable for nonlinear dynamic analysis. And in the fourth chapter, some new elements and components are added into existening procedure for OpenSees comply with object-oriented programming techniques and Open-Sourced design principles.