Not available / text

A considerable amount of research has focused on load-sharing and system effects in repetitive-member wood floor systems subject to transverse loading. However, relatively few studies have been conducted to investigate load-sharing and system effects in repetitive-member wall systems which may be subject to combined transverse and gravity (vertical) loading, and which may have different boundary conditions from floors. This research investigates load-sharing and system effects in light-frame wood wall systems and seeks to develop repetitive-member system factors for codified design that rationally account for load sharing and other system effects. These factors are intended for use in the design of individual wall members, much as repetitive-member factors are used in the design of parallel-member floor and roof systems. As part of this research, an analytical model was developed to account for partial composite action, two-way action, and openings in the wall system. The model was validated using experimental test results and was shown to be able to predict reasonably well the response of light-frame wall systems. The model was then incorporated into a Monte Carlo simulation to perform reliability analyses of light-frame wall systems. Since the structural model is complex, and including a time-history analysis within the time-dependent simulation was not computationally practical, the load combination issue was considered separately from the reliability analysis. Sensitivity studies were conducted to investigate how different system parameters affect strength and reliability of light-frame wall systems. The reliability of light-frame wall systems was next evaluated using a portfolio of representative light-frame wall systems designed according to current code provisions. This portfolio approach was also used in evaluating system factors for light-frame wall systems. Thus, two different approaches (a reliability-based approach and a strength-ratio approach) were considered for developing system factors for member-design to account for load sharing, partial composite action and other system effects. Using the strength-ratio approach, a new framework for system factors (i.e., partial system factors) is suggested in which the effects of partial composite action, load sharing, load redistribution and system size (number of members) are treated separately. / Graduation date: 2003

The Linked Column Frame (LCF) is a new brace-free lateral structural steel system intended for rapid return to occupancy performance level. LCF is more resilient under a design level earthquake than the conventional approaches. The structural system consists of moment frames for gravity that combines with closely spaced dual columns (LC) interconnected with bolted links for the lateral system. The LC links are sacrificial and intended to be replaced following a design level earthquake. The centerpiece of this work was a unique full-scale experiment using hybrid simulation testing; a combination of physical test of a critical sub-system tied to a numerical model of the building frame. Hybrid simulation testing allows for full scale study at the system level accounting for the uncertainties via experimental component and having the ability to model more conventional behavior through numerical simulation. The experimental subsystem consisted of a two story LCF frame with a single bay while the remainder of the building was numerically modeled. Two actuators per story were connected to the specimen. The LC links have been designed to be short and plastically shear dominated and the LCF met the design intent of 2.5% inter-story drift limits. For evaluating the LCF response, hybrid testing was performed for ground motion at three different intensities; 50%, 10% and 2% probability of exceedence in 50 years for Seattle, Washington ground motions. The system overall had exhibited three distinct performance levels; linearly elastic, rapid return to occupancy where only the replaceable links would yield, and collapse prevention where the gravity beam components also became damaged. Results demonstrated a viable lateral system under cyclic and seismic loading, offering a ductile structural system with the ability to rapidly return to occupancy.

Most of the current optimization techniques for the design of light-weight structures are unable to generate structural alternatives at the concept stage of design. This research tackles the challenge of developing an optimization method for the early stage of design. The main goal is to propose a procedure to optimize material and shape of stiff shafts in torsion. / Recently introduced for bending stiffness design, shape transformers are presented in this thesis for optimizing the design of shafts in torsion. Shape transformers are geometric parameters defined to classify shapes and to model structural efficiency. The study of shape transformers are centered on concept selection in structural design. These factors are used to formulate indices of material and shape selection for minimum mass design. An advantage of the method of shape transformers is that the contribution of the shape can be decoupled from the contribution of the size of a cross-section. This feature gives the designer insight into the effects that scaling, shape, as well as material have on the overall structural performance. / Similar to the index for bending, the performance index for torsion stiffness design is a function of the relative scaling of two cross-sections. The thesis examines analytically and graphically the impact of scaling on the torsional efficiency of alternative cross-sections. The resulting maps assist the selection of the best material and shape for cross-sections subjected to dimensional constraints. It is shown that shape transformers for torsion, unlike those for bending, are generally function of the scaling direction. / The efficiency maps ease the visual contrast among the efficiency of open-walled cross-sections and that of close-walled cross-sections. As expected, the maps show the relative inefficiency of the former compared to the latter. They can also set the validity range of thin- and thick-walled theory in torsion stiffness design. The analytical results are validated with the numerical data obtained from ANSYS to guarantee the consistency of the models. The thesis concludes with three case studies that demonstrate the method.

No description available.

Developing a rational method of design has long been the goal of structural engineering. For steel structures, through the development of plastic design and electronic computation, this now seems possible. Several methods have been proposed within the last five years, and one method has been programmed for the digital computer. Five methods are here discussed and compared and the method of Heyman and Prager is investigated in detail. The assumptions and restrictions of the Heyman-Prager method, along with the computer program developed by Kalker, are investigated and discussed. The author attempts to evaluate the usefulness of, and place the Heyman-Prager method in a proper perspective in the overall planning, design, analysis phases of the total structural evolution. It is concluded that a more efficient computer program could be developed to facilitate the structural solution and some methods by which this might be accomplished are suggested. A comprehensive bibliography is provided which traces the development of practical minimum weight, plastic design from its inception up to the present time. / Master of Science