Nonlinear Analysis Of Frame Structures Based On The QR Method And Its Software Development

Frame structure with its flexible layout and easy reconstruction and extension is applicated in industrial and civil construction widely through precast members in factory and assemble them in site, especially the framework of the reinforced concrete has been most widely used as a building structure. The steel frame also has high strength, ductility, excellent seismic performance, a higher degree of mechanization, can all be recycled. This structure is favor for environmental protection and sustainable development. With the improvement of China’s steel production and economic level, this structure will become the main structure in now and the future. The main difference between analysis of the steel frame and reinforced concrete frame is that the steel frame relatively slim,the apparent second-order effects and local and overall instability, and instability often occurs in the material plastic carry to a certain extent. Besides, the semi-rigid connection problem is between beams and columns. The software now we used such as PKPM, SAP2000, SATWE cannot take this main problems influence into considerations together, accurately described the process of the destruction of the steel frame under the strong earthquake and correctly judge limits of the structural system carrying capacity and instability and failure mode. The code about the calculation of beam-column semi-rigid connection is blank and the nodes taken as completely rigid connection or ideal hinged are inconsistent with the actual situation. Although the general-purpose finite element software such as ANSYS, ABAQUS provide a powerful computational tools for structural analysis, it is difficult to compare the calculated results based on material plasticity model in plastic analysis with pole structures commonly used plastic hinge model. When rigid, hinged, plastic hinges and semi-rigid connection node exist together, the general-purpose finite element software is very difficult to deal with high computational cost and efficiency needs to be improved.Professor Qin Rong put forward QR method using spline basis functions and orthogonal polynomials combination to construct overall displacement field, taking generalized displacement parameters of discrete spline nodes as basic unknown constants. In the whole nonlinear analysis, the unknown constants are not varied to avoid redraw network after plastic hinges appear and redefine work of unknown constants. Especially when dealing with multiple nodes exist simultaneously and the nodal degrees of freedom uncoordinated, QR method is superior than finite element method. QR method in high-rise buildings have been some studies, but rarely used in the actual project. The reason is the lack of common computational tools and computational software. This article used nonlinear analysis for steel frame systems and develop a set of corresponding analysis software to provide practical and effective analysis tool for the analysis and design of steel frame structures. At the same time, the software can also be used for the reinforced concrete frame structures with nonlinear calculation.This paper based on former research with my professor and senior students improves the QR method application for nonlinear analysis of steel frame systems. The computer-oriented algorithm calculation is improved. In order to improve the efficiency of the calculation, the core of the program is programmed with VC language including four programs the flexibility of the frame structure static, the second-order elastic, ideal elastic-plastic, second-order elastic-plastic analysis. The before and after processing interface are developed with VB language, and all functions are integrated in a graphical user interface. According to the software development of standards, a set application software of nonlinear analysis of steel frame structures based on QR method is developed. It provides a simple and high-efficiency computational tool for nonlinear analysis, stability analysis, ultimate bearing capacity analysis and also lay the foundation and framework for the follow-up general-purpose software develop-ment.