8 results on '"Structural frames -- Analysis"'
Search Results
2. Damage diagnosis of frame structures using modified modal strain energy change method
- Author
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Hsu, Ting-Yu and Loh, Chin-Hsiung
- Subjects
Noise control -- Analysis ,Noise control -- Methods ,Structural dynamics -- Analysis ,Structural frames -- Analysis ,Structural frames -- Design and construction ,Science and technology - Abstract
This work presents a modified modal strain energy change (M-MSEC) method and its corresponding iteration process to detect damage to frame structures. Analytical results of a three-dimensional frame structure demonstrate that the quantity of damage can be identified correctly by using different modes in the M-MSEC method. A full-scale experimental study is also performed to evaluate the robustness of the M-MSEC method on damage detection as well as damage quantification. Satisfactory results are shown in relation to the modeling error, noise effect, and limited measurements. DOI: 10.1061/(ASCE)0733-9399(2008)134:11(1000) CE Database subject headings: Damage; Structural dynamics; Strain energy; Three-dimensional analysis; Framed structures.
- Published
- 2008
3. Alternative formulations for structural optimization: an evaluation using frames
- Author
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Wang, Qian and Arora, Jasbir S.
- Subjects
Structural frames -- Design and construction ,Structural frames -- Analysis ,Engineering and manufacturing industries ,Science and technology - Abstract
Two altemative formulations based on the concept of simultaneous analysis and design are presented and evaluated for optimal design of framed structures. Different behavior variables, such as nodal displacements and member forces, are also treated as optimization variables in addition to the actual design variables for the problem. With these formulations, the equilibrium equations become equality constraints in the optimization process. The objective and all constraints become explicit functions of the optimization variables. Therefore, their derivatives can be obtained quite easily compared to those for the conventional approach where special design sensitivity analysis procedures must be used to calculate derivatives. It is also easier to use existing analysis software for optimization with the alternative formulations because the sensitivity equations are not formed or solved. A sequential quadratic programming method that exploits sparsity of problem functions is used to solve sample problems and evaluate the formulations. Implementation of the alternative formulations with an existing analysis program is explained. Advantages and disadvantages of the formulations are discussed. It is concluded that the alternative formulations work quite well for optimization of framed structures and have potential for further development. CE Database subject headings: Simulation; Optimization; Framed structures; Computer programming; Frames.
- Published
- 2006
4. Structural weight optimization of frames using tabu search. II: evaluation and seismic performance
- Author
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Kargahi, Mohsen and Anderson, James C.
- Subjects
Structural frames -- Analysis ,Computer-generated environments -- Usage ,Computer simulation -- Usage ,Engineering and manufacturing industries ,Science and technology - Abstract
In a companion paper, a structural optimization computer program based on tabu search (TS) was developed and used to optimize three two-dimensional moment resisting frames. All three frames were representative of current design practice for steel structures in the Los Angeles area and were part of an SAC program of study following the Northridge earthquake. The weight reduction obtained for the three-story/three-bay, the nine-story/five-bay, and the twenty-story/five-bay frames in the initial study were 26.4, 18.3, and 25.5%, respectively. In this paper, the seismic performance of the optimized structures is evaluated by calculating the rotation demands in the plastic hinges that form in the structural elements during nonlinear time history analyses. Twenty ground motion records having the return probability of 10% in 50 years are considered in the study. The frames were expected to achieve the Life Safety performance level as outlined in the FEMA-273 guidelines, and in general, they were able to achieve this level of performance. Next, the same frames are optimized using the optimization module of a commercially available program, with the same assumptions (starting point sections, loading, etc.). The TS optimization program was able to achieve a larger weight reduction than the commercially available program. The performance of the final commercial program designs is then briefly evaluated by one nonlinear time history analysis for each building using the ground motion record that produced the most severe responses for the TS designs. Performance of these frames was very similar to the TS design frames. Finally, the performance of the three TS designed frames is compared to that of the original design frames, which were designed under the same code lateral forces. The original frame designs are analyzed for the ground motion record (or records) that resulted in the largest plastic hinge rotations in the TS design frames. The values of the maximum story plastic hinge rotations, story displacements, and interstory drift ratios are compared. The response of the TS optimized frames was comparable to the original frames. CE Database subject headings: Weight; Optimization; Seismic effects; Frames; Structural analysis.
- Published
- 2006
5. Structural weight optimization of frames using tabu search. I: optimization procedure
- Author
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Kargahi, Mohsen, Anderson, James C., and Dessouky, Maged M.
- Subjects
Algorithms -- Usage ,Structural frames -- Analysis ,Earthquake engineering ,Algorithm ,Engineering and manufacturing industries ,Science and technology - Abstract
A class of search techniques, heuristic search methods, and their suitability for structural optimization are considered for discrete optimization problems. The tabu search method is selected for application to structural weight optimization of skeleton structures. The search method is first tested to find the minima of a function in a nonlinear nonconvex optimization mathematical problem, and an algorithm is developed. Further, a computer program is developed that uses tabu search for weight minimization of two-dimensional framed structures. The program, written in the FORTRAN computer language, performs search, structural analysis, and structural design in an iterative procedure. The program is used to optimize the weight of three previously designed frames including three-story/three-bay, nine-story/five-bay, and 20-story/five-bay steel moment resisting frames. The program demonstrated its capability of optimizing the weight of these medium size frames in a reasonable amount of time without requiring engineer interference during the search. The structural weights for the three frames are reduced by an average of 23.4% from their original design weight. CE Database subject headings: Weight; Optimization; Seismic effects; Frames; Structural analysis.
- Published
- 2006
6. Sequential hybrid inverse mapping for state-specified design of frames
- Author
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Ito, Hitoshi and Nakamura, Tsuneyoshi
- Subjects
Algorithms -- Analysis ,Structural frames -- Design and construction ,Structural frames -- Analysis ,Structural stability -- Analysis ,Algorithm ,Engineering and manufacturing industries ,Science and technology - Abstract
A new method via inverse problem formulation including frame stability (P-[delta] and P-[DELTA] effects) is presented for state-specified design of an arbitrary planar elastic frame. The well-known governing equations for second-order analysis with respect to unknown displacements for a set of prescribed member stiffnesses of a frame are here regarded as those with respect to unknown member stiffnesses for a set of prescribed member-end strains and displacements. A method of sequential mapping for such a 'direct design' problem is generalized for a hybrid inverse problem of an arbitrary plane frame such that a combined set of unknown member stiffnesses and unknown member-end strains (or displacements) is to be found for a set of prescribed member-end strains (or displacements) and prescribed member stiffnesses. The concept of 'state-design vector' is shown to be useful for such a general problem of hybrid-inverse mapping. A general design program has been developed on the basis of the proposed algorithm on the first-order equations. Four design examples not only demonstrate the program performance but also disclose P-[delta] and P-[DELTA] effects on the design. A guideline is described for practical application in compliance with an allowable stress design code. DOI: 10.1061/(ASCE)0733-9445(2006) 132:9(1441) CE Database subject headings: Structural design; Stiffness; Frames; Structural stability; Buckling; Mapping; Computer programming.
- Published
- 2006
7. Stability requirements for beams in seismic steel moment frames
- Author
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Okazaki, Taichiro, Liu, Dawei, Nakashima, Masayoshi, and Engelhardt, Michael D.
- Subjects
Structural frames -- Analysis ,Structural stability -- Analysis ,Building, Iron and steel -- Analysis ,Engineering and manufacturing industries ,Science and technology - Abstract
An analytical study was conducted on the cyclic loading behavior of beams in steel moment frames. Lateral--torsional buckling and local buckling were explicitly considered in the analysis. Beam cross-sectional dimensions were varied to represent a wide range of rolled wide flange shapes. The unbraced length of the beams corresponded to slenderness ratios about the weak axis ranging between 60 and 100. Based on the analyses, flange and web width-thickness limits were established that would permit the beam to achieve various target rotation capacities. These limits are presented in terms of limit curves which plot the flange width-thickness ratio against the web width-thickness ratio. The limit curves clearly show strong flange--web interaction. Different limit curves were developed for a range of target rotation angles, weak axis slenderness ratios, and residual strength levels. Postbuckling behavior and strength degradation mechanism were studied. The results of the analyses are compared against current building code requirements for beam stability in seismic steel moment frames, and the adequacy of the current code requirements are evaluated. DOI: 10.1061/(ASCE)0733-9445 (2006) 132:9(1334) CE Database subject headings: Steel beams; Seismic design; Cyclic loads; Slenderness ratio; Numerical analysis; Structural stability.
- Published
- 2006
8. Elastoplastic large deflection analysis of three-dimensional steel frames
- Author
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Shugyo, Minoru
- Subjects
Joints (Engineering) -- Testing ,Structural frames -- Analysis ,Building, Iron and steel -- Testing ,Engineering and manufacturing industries ,Science and technology - Abstract
A beam element is presented for analysis of the elastoplastic large deflection of three-dimensional (3D) frames that have steel members with semirigid joints. A plastic hinge type formulation was employed, combining the 'modified incremental stiffness method,' the updated Lagrangian formulation, and numerical integration about the end sections of the element. The end sections of the element are discretized into small areas to estimate the plastic deformations of the element. The elastic and plastic deformations of the element are treated separately. The behavior of a semirigid joint is modeled as the element-end compliance. The method can treat comprehensively the plastic deformations due to torsion and warping. Considering the assumptions of the method, a four-element approximation for a member gives excellent results for a 3D analysis of semirigid and pin-connected steel frames as well as for rigid frames. The adequacy of the method is verified by comparing the results with experimental ones obtained by the writer. Some examples are presented to demonstrate the accuracy and efficiency of the method. DOI: 10.1061/(ASCE)0733-9445(2003)129:9(1259) CE Database subject headings: Steel frames; Elastoplasticity; Deflection; Joints; Plastic hinges; Warpage.
- Published
- 2003
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