Design Method Research Of Engineering Structure On Character Parameter Analysis

Structural frequency and mode are decided by mass and stiffness, only related with its material property and geometric dimension,and not relevant with other factors. So frequency and mode are called by structural inherent character parameter. Frequency vector is the absolute ratio between the global mass and the global stiffness;mode vector is the relative ratio between the local mass and the local stiffness.The order of mode vector is also the sequence of decomposing response under external environment. Character parameter can be used to supervise structural concept design, mechanical design and performance-based design.During the whole structure design, the concept design is the soul centre and the most complex stage, which determines the load-carrying capability and destruction form. Combing structure character parameter with concept design, mechanical design and performance-based design, it gives structure design a new research direction. Supported by the National Natural Science Foundation of China(50978232),the thesis successively researches on the facotors impacting the character parameter and scope of application. Firstly, mode is classified and quantized.And then some creative work is done by structural design based frequency and mode, using character parameter as tool to supervise performance-based design.It realizes exploratory research of the quantized concept design and mechanical design. According to those original achievements, the thesis achieves main conclusions as following:1 Mode classification and quantizationMode is classified as favourable mode and unfavourable mode. The favourable mode is mainly composed of translation mode, bending mode and axial direction mode and so on;the unfavourable mode consists of shear mode, torsion mode, local mode, coupling mode with single one, for example, the coupling mode including shear-torsion mode, shear-bending mode and torsion-bending mode and so on. Modal direction coefficient can identify the mode vibration character.2 Character parameter supervising concept design and mechanical designBecause the mode is the self-contained orthogonal matrix of all response, structure internal force, stress and strain can be expanded by mode matrix.The three discriminants for number mode of displacement expansion is proposed. By the analysis and control of effective participation mass, it is reasonable to advance the order of the favorable mode and to postpone the order of the unfavorable mode. There is a quantization tool for concept design and mechanical design.3 To establish the elevation of fundamental frequency principle of towering structure For boosting the fundamental frequency of towering structure, it is wise to reduce the upper structural mass and to elevate the bottom stiffness. Some structural factors impacting frequency such as shear wall number and its thickNess, floor thickNess, height of gravitational centre and inclined brace height and angle and so on are discussed. Relevant laws are firstly drawn by finite element method, and then those ones are validated by structural experiment. Those conclusions can be extended to similar project.4 The description of core mechanical character of beam-column joint In order to show the core mechanical character of beam-column joint, the core degree of modal participation can describe its basic property. The degree of modal participation factors are decreased when the span-depth ratio of beam and shearing-span ratio of column increase. The core degree of modal participation can quantize the core mechanical property of beam-column joint. At the same time, the core degree of modal participation proves the scope of common beam and moderate column in the code is conservative.5 The equivalent load method of prestress force effect on frequency The straight prestress rebar, crease prestress rebar and curved prestress rebar effect on frequency are discussed. Utilizing the equivalent load method, dynamic equation is derived, and then the results are confirmed by finite element method. Some general laws of prestress effect on beam frequency are obtained.6 Multiple mode adptive Pushover method (MMAPM) put forward Because Pushover method being simple and feasible for structure calculation, now it is widely used in performance-based design and antiseismic retrofit design. In order to conquer defects of conventional Pushover method, multiple mode adptive Pushover method (MMAPM) is put forward. MMAPM not only conquers conventional Pushover defects, but also gives the method for detemination number of mode.The combination method is advised according to the degree of frequency correlation, choosing SRSS method or CQC method.The MMAPM is a feasible method for performance-based design.7 Energy methods for high pier with P-delta effect Energy methods can be used for high pier with P-delta effect including vertical earthquake load.Compared with other method, energy method is simple and easy for designer, and can be extended to similar projects.