Browsing by Author "Vernon Matzen, Committee Member"

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Analytical and Experimental Investigation of the Damping Matrix in Shear Building Models
(2006-04-27) Cropper, Michael Evan; Abhinav Gupta, Committee Chair; Vernon Matzen, Committee Member; John Baugh, Committee Member
In this thesis, we present a study conducted on investigating the nature of damping matrix associated with multi degree of freedom simple shear building models. The various conventional methods of creating damping matrices in structures are summarized and numerical examples are used to illustrate the inconsistencies among them. Numerical examples are also used to illustrate the significance of non-zero off diagonal terms in the transformed damping matrix obtained after pre and post multiplication with mode shape matrix, i.e. the significance of non-classical nature of damping matrix in certain cases. The analytical study is followed by the description of a laboratory experiment that is developed to evaluate the validity of analytical results. The results from experimental studies of simple 2-DOF and 3-DOF shear building models, both with and without supplemental damping devices, are presented to validate the inconsistencies associated with the conventional methods of creating damping matrices in structures. It is also shown that the incorrect formulation of damping matrix results in highly incorrect responses. Several formulations for damping matrices are then proposed and their validity is evaluated by comparison with experimental results.
Finite Element Modeling of Light Frame Wood Structures An Integrated Approach
(2009-06-26) Collins, Michael Scott; Bohumil Kasal, Committee Chair; Mervyn Kowalsky, Committee Member; Jim Nau, Committee Member; Vernon Matzen, Committee Member
This research aims to improve the framework and practicality for the analysis and design of light frame wood structures. The light frame wood structure is broken down into its constituent components for modeling: connections, shearwalls and diaphragms, then the assembled structure. This work relies extensively on available finite element technologies to identify key components and modeling methods of those key components. Finite element modeling strategies were developed to investigate the response of light framed wood structures. The models developed are intended to be general in nature and not restricted to a particular type of loading and cover static monotonic, dynamic monotonic, static cyclic and dynamic loading. In doing so, modeling strategies are proposed to make the models more computationally efficient and reduce the complexity without a loss of information of the response. Experiments were conducted on connections, components, and the assembled structure and designed to evaluate the response of wood structures and their components and verify the developed models. Criteria used to evaluate the models include hysteresis shape, energy dissipation, strains, local displacements and forces, and observed failure modes. and compared with results of experiments designed and verify the model.
Implementation of Direc Displacement Based Design for Pile and Drilled Shaft Bents
(2006-02-08) Suarez, Vinicio; Vernon Matzen, Committee Member; Mohammed Gabr, Committee Member; Mervyn Kowalsky, Committee Chair
The work in this thesis attempts to implement the Direct Displacement Based Design (DDBD) method to the seismic design of long reinforced concrete pile and drilled shaft bents embedded in soft soils. DDBD has been successfully used to design bridge columns that are fixed at ground level and without soil interaction. The implementation of DDBD for column bents, however, requires the consideration of soil-structure interaction effects--namely added flexibility and damping. The main objective of this research is to develop an equivalent model to predict yield displacement and ductility and to assess the equivalent viscous damping as a function of ductility demand and soil type. The proposed equivalent cantilever model replaces a nonlinear soil-column system. In the equivalent model, the column is considered fixed at some depth below ground at the point of maximum moment and possible formation of an underground plastic hinge. The yield displacement of the column is matched with the yield displacement of the soil-column model by introducing a coefficient and the energy dissipation characteristics are matched by the introduction of equivalent viscous damping as function of ductility and soil type. Charts and equations are provided to compute all the parameters involved in the equivalent formulation. These aids resulted from parametric studies that involved nonlinear static and nonlinear time history analyses of soil-column systems.
Seismic Analysis and Reliability-based Design of Secondary Systems
(2005-09-19) Saigal, Rakesh Kumar; M. Shammur Rahman, Committee Member; Abhinav Gupta, Committee Chair; Ajaya Gupta, Committee Member; Vernon Matzen, Committee Member
Seismic qualification of secondary systems such as piping is performed using the response spectrum method. Structural responses evaluated using response spectrum method are used for checking the design equations specified by the ASME Section III Boiler and Pressure Vessel (ASME BPV) Code. This dissertation addresses the topics of combining modal responses in response spectrum method and the reliability associated with the ASME design equations. In the method for combining modal responses, the validity of the existing expressions for rigid response coefficient is evaluated for the case of floor motions which represents earthquake input to the secondary systems. A closed-form formulation is proposed for the rigid response coefficient and is verified using time history analysis for both the cases of ground and floor motions. The closed-form expression is then extended to response spectrum method by developing a simplified procedure for evaluating relative Fourier amplitudes of few significant pulses from the floor response spectrum. In the reliability-based design of piping systems using ASME BPV code design equations, performance functions are formulated to characterize the different failure modes in a straight pipe segment. These performance functions are then used to determine the implicit reliability levels associated with the design equations in ASME-BPV code. This calibration of the existing design equations is intended to provide an input for future studies related to the development of Load and Resistance Factor (LRFD) design equations which require an estimate of implicit reliability levels in existing equations in order to establish the target reliabilities.
Two-Way Behavior and Fatigue Performance of 3-D GFRP Sandwich Panels
(2009-07-16) Taylor, Elliott; Emmett Sumner, Committee Member; Sami Rizkalla, Committee Chair; Vernon Matzen, Committee Member
This research presents the two-way bending and fatigue behavior of an innovative 3-D glass fiber reinforced polymer (GFRP) pultruded sandwich panel. The panels consist of two GFRP face sheets separated by a foam core with through thickness GFRP fiber insertions to achieve the composite action between the top and bottom layers of the panel. The panels tested under two-way bending include six different configurations to consider the effect of number of skin plies, fiber insertion patterns, panel thicknesses, and the foam type. All panels were simply supported at the four edges, loaded by a single concentrated load at mid span, and tested subjected to a quasi-static loading condition up to failure. The parameters under consideration for testing the two-way panels were also used in a one way configuration under two fatigue loading condition. The fatigue test consists of three point flexural loading configuration in which the panel is subjected to cyclic loading for a minimum of 600,000 cycles or up to failure. The research also presents the finite element analysis (FEA) which was used to describe the behavior of the 3-D GFRP sandwich panel under the effect of the applied load used in the experimental program. The effect of the various parameters including: the aspect ratio, thickness, number of skin plies, skin strength, and insertion density were considered. The experimental results were used to calibrate the analysis and produce design guidelines for practitioners. The proposed design guidelines can be used for design of the panels for various applications such as truck trailer elements, temporary mats, and pedestrian bridge decks.