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Thesis (M.S.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains xv, 141 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 139-141).

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 32-33). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 32-33). Also available on the World Wide Web.

For the sustainability of today’s infrastructure, it is critical that engineers are capable of developing economical and safe design solutions for structures such as bridges and buildings. Multiple things must be considered for structural design. Structural members must be sized to resist applied loading conditions while satisfying design code capacity requirements. Design is also dependent on geometry, constructability, cost, material, availability, etc. The focus of optimization is to determine the best solution for a problem that is defined by a set of given constraints. For structural optimization applications, typically the problem is set up to determine the member cross-sectional areas that will yield an overall minimum weight or cost. It can also be a beneficial tool to compare different design alternatives quickly, especially in the preliminary stages of a project. Various approaches for solving optimization problems have been implemented in different fields of research. Traditional techniques such as linear/non-linear programming are available and more recently heuristic algorithms, which simulate patterns of natural phenomena, have been developed. For this research a heuristic Harmony Search (HS) algorithm is used to optimize a steel plate girder bridge. The HS algorithm is a more recent optimization concept that has been implemented within structural engineering research for solving many truss and frame optimization problems. There has been a limited amount of research on the HS algorithm for bridge structure optimization problems. For this project, HS algorithm will be used to optimize two steel plate girder bridges with varying cross-section configurations. Finite Element Models of the structures using the optimized properties will be used to verify demand/capacities and adequacy of the optimized design. Results will also be compared to traditional preliminary bridge sizing methodologies and programs. / Civil Engineering

published_or_final_version / Civil Engineering / Master / Master of Philosophy

There is significant interest in the used of Steel-plate composite (SC) walls for protective structures, particularly for impactive and impulsive loading. The behavior of SC walls is fundamentally different from that of reinforced concrete (RC) walls due to the addition of steel plates on the exterior surfaces, which prevent concrete scabbing and enhance local perforation resistance.<div><br></div><div>Laboratory-scale SC wall specimens were fabricated, cast with concrete, and then tested in an indoor missile impact test-setup specially-built and commissioned for this research. The parameters included in the experimental investigations were the steel plate reinforcement ratio (3.7% - 5.2%), tie bar spacing, size, and reinforcement ratio (0.37% - 1.23%), and the steel plate yield strength (Gr.50 - Gr.65). Additional parameters include the missile diameter (1.0 in., 1.5 in.), weight (1.3 lbs, 2.0, lbs, 3.5 lbs), and velocity (410 - 760 ft/s). A total of sixteen tests were conducted, the results of which are presented in detail including measurements of missile velocity, penetration depth, rear steel plate bulging deformation, and test outcome (stopped or perforated). The test results are further used to illustrate the significant conservatism of a design method developed previously by researchers (Bruhl et al. 2015a), and the sources of this conservatism including differences in the missile penetration mechanism, dimensions of the concrete conical frustum (breaking out), and the penetration depth equations assumed in the design method.<br></div><div><br></div><div>Numerical models were developed to further investigate local damage behavior of SC walls. Three-dimensional finite element models were built using LS-DYNA software and employed to simulate the missile impact tests on the SC wall specimens. The numerical analysis results were benchmarked to the experimental test results for the validation of the models.<br></div><div><br></div><div>Two sets of parametric studies were conducted using the benchmarked numerical models. The first set of the parametric studies was intended to narrow the perforation velocity ranges from the experimental results for use in evaluating the accuracy of a rational design method developed later in this research. The second set of the parametric studies was intended to evaluate the influence of design parameters on the perforation resistance of SC walls. It was found that flexural reinforcement ratio and steel plate strength are significant parameters which affect the penetration depth. However, shear reinforcement ratio has negligible influence.<br></div><div><br></div><div>Results from the experimental investigations and the numerical parametric studies were used to develop a rational design method which modifies the three-step design method. The modified design method incorporates a proposed modification factor applicable to the penetration depth equations and the missile penetration mechanism observed from the experiments. The modified design method was verified using the larger-scale missile impact test data from South Korean tests as well.<br></div><div><br></div><div>Additional research was performed to evaluate the local failure modes when the perforation was prevented from missile impactive loading on SC walls. Through numerical parametric studies, three different local failure modes (punching shear, flexural yielding, and plastic mechanism formation) were investigated. Also, an innovative approach to generating static resistance functions was proposed for use in SDOF or TDOF model analysis.<br></div>

The behavior of steel plate shear walls under the effects of lateral loads depends on the stiffness of the surrounding frame members. Previous research has quantified the minimum required stiffness of columns in the middle stories of steel plate shear wall systems. As the columns of the steel plate shear wall system are subjected to both large axial forces and bending moments, use of composite columns is a viable option in this system. Among the different types of composite columns, the recently developed partially encased composite columns with built-up steel sections have some advantages over other types of composite columns and thus their performance as columns in steel plate shear wall systems needs to be studied. In the first part of this research, a numerical and analytical study has developed a new design parameter and determined the minimum required stiffness of end beams in end panels of the steel plate shear wall system. The effect of the rigidity of the frame connections on the uniformity of the tension field has also been studied in this part. The second part of this research includes two large scale tests on steel plate shear walls with built-up partially encased composite (PEC) columns. One of the test specimens was modular and the other one used reduced beam sections in the frame. The results of the tests show that the columns were stiff enough to anchor the infill plate. The PEC columns in these tests performed in a ductile manner. The overall system behavior was ductile, stable and the specimens showed good seismic behavior and redundancy. Based on the results and observations of this research, design recommendations for PEC columns used as the vertical boundary members of steel plate shear walls are provided. / Structural Engineering

Finite element method and strip method are two widely used techniques for analyzing steel plate shear wall (SPSW) systems. Past research mostly focused on the prediction of lateral load capacity of these systems using these numerical methods. Apart from the lateral load carrying capacity, the lateral stiffness of the wall system needs to be determined for a satisfactory design. Lateral displacements and the fundamental natural frequency of the SPSW system are directly influenced by the lateral stiffness. In this study the accuracy of the finite element method and strip method of analysis are assessed by making comparisons with experimental findings. Comparisons revealed that both methods provide in general solutions with acceptable accuracy. While both methods offer acceptable solutions sophisticated computer models need to be generated. In this study two alternative methods are developed. The first one is an approximate hand method based on the deep beam theory. The classical deep beam theory is modified in the light of parametric studies performed on restrained thin plates under pure shear and pure bending. The second one is a computer method based on truss analogy. Stiffness predictions using the two alternative methods are found to compare well with the experimental findings. In addition, lateral stiffness predictions of the alternate methods are compared against the solutions provided using finite element and strip method of analysis for a class of test structures. These comparisons revealed that the developed methods provide estimates with acceptable accuracy and are simpler than the traditional analysis techniques.