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Optimum design of wide span cable-stayed roof structures
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This paper investigates the structural response of wide span structures where the primary structural system is cable-stayed roof, and aims at optimizing the design of such structures. Finite element analysis is carried out using commercial software taking into consideration the nonlinear formulation of cables. In order to check the accuracy and capability of the present approach, several examples are presented for nonlinear analysis of cable structures, and the response is found to agree with published results. Additionally, finite element discretization and nonlinear analysis are carried out for an existing cable-stayed roof structure under all possible loading conditions. A numerical study is conducted where four different systems are suggested for the same structure: plane truss, space truss, cable-stayed plane truss and cable-stayed space truss systems. For each system, structural analysis is made under all design load combinations and optimization of design in order to reach the least possible weight and cost. The numerical results indicate the capability of the proposed approach in predicting the forces and deformations of cable structures and optimizing the design of structural element. It was concluded that the space truss and the cable-stayed space truss providing efficient performance as well as economy.
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... A significant amount of study has been done to research a stress-strain state (SSS) of cable-stayed structures. The design of wide-span cable-stayed structures is justified in [1]. In article [2], a calculation of a ceiling for a unit load in the joints of the bottom boom is performed. ...
... In the works devoted to research of steel-reinforced concrete cable-stayed structures, the issue of using and developing calculating composite stay for methods ropes with fiber structure is not considered in works [1][2][3][4][5]. ...
The purpose of research is to justify a calculation method for a stay rope of composite fiber structure with a breakage in fiber continuity. Research methodology is in constructing and solving a deformation model of a composite fiber stay rope with continuity breakage of one of its fibers. The calculation method of a stress-strain state of a stay rope of composite fiber structure considering the breakage of one of its fibers is established. The scientific novelty of research is in determining that the length of manifestation of a local disturbance of a stress-strain state of composite stay rope is proportional to a square root of a ratio of tensile modulus of a reinforcing element material and shear modulus of an elastic material that connects them. The practical value of the research is in that the calculation method allows reasonable prediction of a tractive capacity loss of a stay rope as a result of breakage of any of its reinforcing elements. The known value of residual tractive capacity allows reasonable selection of a safety margin for a stay rope, which ensures a sufficient level of reliability of a cable-stayed bridge.
... rking stress method, which results in economical design of truss design. Objective of this study is to analyze and design Pratt truss of 30m span with Limit State Method (LSM) and Working Stress Method (WSM) of design of steel structures. Pratt truss model is analyzed in STAAD Pro. The truss is analyzed for the dead load, live load and wind loads. Gehan A. Hamdy et. al. (2018) This study investigates the structural response of wide span structures where the primary structural system is cable-stayed roof, and aims at optimizing the design of such structures. A numerical study is conducted where four different systems are suggested for the same structure: plane truss, space truss, cable-stayed plane truss and c ...
In structural mechanics, traditional analyses methods usually employ matrix operations for obtaining displacement and internal forces of the structure under the external effects, such as distributed loads, earthquake or wind excitations, and temperature changing inter alia. These matrices are derived from the well-known principle of mechanics called minimum potential energy. According to this principle, a system can be in the equilibrium state only in case when the total potential energy of system is minimum. A close examination of the expression of the well-known equilibrium condition for linear problems, P=KΔ, where P is the load vector, K is the stiffness matrix and Δ is the displacement vector, it is seen that, basically this principle searches the displacement set (or deformed shape) for a system that minimizes the total potential energy of it. Instead of using mathematical operations used in the conventional methods, with a different formulation, meta-heuristic algorithms can also be used for solving this minimization problem by defining total potential energy as objective function and displacements as design variables. Based on this idea the technique called Total Potential Optimization using Meta-heuristic Algorithms (TPO/MA) is proposed. The method has been successfully applied for linear and non-linear analyses of trusses and truss-like structures, and the results have shown that the approach is much more successful than conventional methods, especially for analyses of nonlinear systems. In this study, the application of TPO/MA, with Harmony Search as the selected meta-heuristic algorithm, to cables net system is presented. The results have shown that the method is robust, powerful and accurate.
This paper presents an explicit analytical iteration method for form-finding analysis of suspension bridges. By extending the conventional analytical form-finding method predicated on the elastic catenary theory, two nonlinear governing equations are derived for calculating the accurate unstrained lengths of the entire cable systems both the main cable and the hangers. And for the gradient-based iteration method, the derivation of explicit calculation for the Jacobian matrix while solving the nonlinear governing equation enhances the computational efficiency. The results from sensitivity analysis show well performance of the explicit Jacobian matrix compared with the traditional finite difference method. According to two numerical
examples of long span suspension bridges studied, the proposed method is also compared with those reported approaches or the fundamental criterions in suspension bridge structural analysis, which eventually confirms the accuracy and efficiency of the proposed approach.
This paper introduces a new and effective design amplification factor-based approach for reliable optimum design of trusses. This paper may be categorized as in the family of decoupled methods that aiming for a reliable optimum design based on a Design Amplification Factor (DAF). To reduce the computational expenses of reliability analysis, an improved version of Response Surface Method (RSM) was used. Having applied this approach to two planar and one spatial truss problems, it exhibited a satisfactory performance.
This paper presents a spatial catenary cable element for the nonlinear analysis of cable-supported structures. An incremental-iterative solution based on the Newton-Raphson method is adopted for solving the equilibrium equation. As a result, the element stiffness matrix and nodal forces are determined, wherein the effect of self-weight and pretension are taken into account. In the case of the initial cable tension is given, an algorithm for form-finding of cable-supported structures is proposed to determine precisely the unstressed length of the cables. Several classical numerical examples are solved and compared with the other available numerical methods or experiment tests showing the accuracy and efficiency of the present elements.
A Harmony Search (HS) and Genetic Algorithms (GA), two powerful metaheuristic search techniques, are used for minimum weight designs of different truss structures by selecting suitable profile sections from a specified list taken from American Institute of Steel Construction (AISC). A computer program is coded in MATLAB interacting with SAP2000-OAPI to obtain solution of design problems. The stress constraints according to AISC-ASD (Allowable Stress Design) and displacement constraints are considered for optimum designs. Three different truss structures such as bridge, dome and tower structures taken from literature are designed and the results are compared with the ones available in literature. The results obtained from the solutions for truss structures show that optimum designs by these techniques are very similar to the literature results and HS method usually provides more economical solutions in multi-element truss problems.
An equivalent friction element is proposed to simulate the friction in cable-strut joints. Equivalent stiffness matrixes and load vectors of the friction element are derived and are unified into patterns for FEM by defining a virtual node specially to store internal forces. Three approaches are described to verify the rationality of the new equivalent friction element: applying the new element in a cable-roller model, and numerical solutions match well with experimental results; applying the element in a continuous sliding cable model, and theoretical values, numerical and experimental results are compared; and the last is applying it in truss string structures, whose results indicate that there would be a great error if the cable of cable supported structures is simulated with discontinuous cable model which is usually adopted in traditional finite element analysis, and that the prestress loss resulted from the friction in cable-strut joints would have adverse effect on the mechanical performance of cable supported structures.
The paper proposes an unitary strategy for the static analysis of general cable nets under conservative loads. A form-finding is first performed in order to initialize the successive non linear analysis. The numerical procedures carried on in both steps, form finding and structural analysis of the net, employ a three dimensional elastic catenary element. Equilibrium conditions at internal nodes and kinematic compatibility at the end nodes of each cable are used to derive the global equations of the net. When the pre-stresses are high and the topology of the net is involved, an accurate initializing solution is essential for the convergence of the successive numeric non linear structural analysis (performed by Newton method). The numerical applications highlight the capability of the proposed procedure to solve three dimensional problems with taut and slack cables, out of plane distributed forces (modeling wind loads), point loads along the cables. The contemporary presence of cables and compression truss elements is also considered testing the effectiveness of the method in the analysis of tensegrity structures.