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Morphological Analysis and Engineering Applications of Branching Structures

Author: ZhangJianLiang
Tutor: ShenShiZuo；WuYue
School: Harbin Institute of Technology
Course: Structural Engineering
Keywords: branching structure morphological analysis stability analysis effective length coefficients form-active structure
CLC: TU399
Type: Master's thesis
Year: 2011
Downloads: 51
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Abstract

Branching structure, as a structural morphological concept, was put forward by German architect Frei Otto in 1960s. With novel and beautiful configurations and reasonable force-bearing characteristics, branching structures are favored by architects, and have been employed in many engineering applications. However, research on branching structures is still at the exploratory stage at home and abroad, and there are no clear and definite provisions for branching structure design in current codes, which restrict the development of branching structures to some extent. From the standpoint of present researches, studies on branching structure are mainly on form-finding method, mechanical behavior, joint form and construction technology. Based on the former achievements, this research focused on form-finding method and stability design of the branching structure. Finally these research results were applied in two practical projects, which contributed the development of branching structure in our country.The main research contents are presented as following:1. Based on summarizing the geometric and mechanical characteristics of branching structure, and referencing to the inverse-hang method, a new method which named inverse-hang recursive method was put forward for branching structure form-finding. The fundamental idea of this method can be illustrated as following: if all the higher-order branches point to the force center of the branches which generated from themselves, then all the bars of the branching structure will only bears axial forces, it means the structure is a form-active structure. The method has advantage in simple principle and convenient operation. Via compared with former form-finding method and applied in engineering, the validity and applicability of inverse-hang recursive method is proved.2. Two typical types of branching structures, one with side sway and the other with no sway, were analyzed systemically for their stability properties, which revealed that the buckling form of branching structure is similar to the conventional column. The lowest order buckling form of branching structure with side sway is flexural buckling with form of a half wave, and the lowest order buckling form of branching structure with no sway is flexural buckling with form of a whole wave. Furthermore, methods for deciding effective length coefficients (ELC) were summarized, and the method based on the entire buckling was put forward to calculate the ELC of branching structures. Parameter analysis was carried out and some suggestion values of the ELC of branching structures were given. Besides, refereeing to the concept of stepped column, the equivalent stiffness method was put forward as a simplified calculation method for the ELC of branching structures.3. The inverse-hang recursive method was applied in the branching structure designs of the Mohe toll-station gateway and the new Heilongjiang museum. Moreover, the eigenvalue buckling analysis and the whole process analysis considering geometric nonlinearity and material nonlinearity of the branching structures were carried out. ELC of the branching structures was computed out. Obviously, the inverse-hang recursive method has strong engineering applicability, and the result on effective length coefficients is basically in accordance with parameter analysis result. Some suggestions in ELC selection have been proposed for engineering applications.

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