Not available / text

No description available.

No description available.

No description available.

No description available.

No description available.

Cable stayed bridges are the state of the art in long span bridges. Developments in cable response analysis and computer hardware and software have allowed engineers to design and build many cable stayed bridges. Bridges of many different configurations with longer and longer spans are being built. With the long spans and high axial loads in the deck, the stability of cable stayed bridges becomes a growing concern. Current analysis procedures use a parabolic approximation to the true catenary response of cables, which is quite accurate for tight cables; however, for near instability conditions with the accompanying large deflections and consequently loose cables, a catenary model is called for. Herein, a study is conducted on the elastic stability of cable stayed bridges utilizing a true catenary model of cable response. A dimensional analysis of cable stayed bridge stability is undertaken as well as deck maximum deflection and moment under service load conditions. A computer program written by this author is the analysis tool used in this work. The program is given the acronym ULA which stands for Ultimate Load Analysis. ULA is a nonlinear plane frame program with catenary cable elements and an interactive graphics interface. The dimensional analysis is carried out by comparing the computer model of a cable stayed bridge to the theoretical model of a beam on an elastic foundation. Two preliminary simplified cable stayed bridge backspan models are studied first in order to develop the dimensionless ratios that are applicable to the bridge response and to gain an insight into the cable stayed bridge behaviour. The final model is that of an entire cable stayed bridge. Because of the multitude of parameters governing cable stayed bridge behaviour it is not possible to describe all cable stayed bridges. Instead, the dimensionless behaviour of a standard model is examined and the sensitivity of this standard to various parameter variations is given in the form of dimensionless charts. Finally, a preliminary design and analysis aid is developed from the dimensionless charts and is then applied to two existing bridge designs. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The increase in the speed of the automobile and the increase in the volume of traffic has presented many problems to the highway designer, one of the most important being the elimination of grade crossings. The rigid frame bridge, introduced in this country in the early 1920's, offered a very satisfactory solution to the problem of grade separation. This type of structure was used quite extensively by the Westchester County Park Commission in the expansion of the highway system of lower New York State. The rigid frame is more economical, has greater simplicity, and is more adaptable to architectural treatment than the more conventional deck or through girder bridge. The problem of grade separation was simplified to a still greater degree by the use of the skewed rigid frame, but due to the complexity of analyzing this type of structure its use was limited in early installations. Early theories for the analysis of the skewed type of structure were based on the theories of the right rigid frame and arch, but when these theories proved inadequate it was necessary to develop a more rigorous analysis. Although the new theories were accurate, they were also much too involved for practical use and certain assumptions were made to reduce their complexity. Although the newly developed theories did solve the problem of analyzing the skewed rigid frame, another problem arose, namely that or the validity of the assumptions. Although structural failures were few, the use of high, and in some respects indeterminate, factors of safety may well have compensated for any errors in the assumptions. Committee 314 of the A.C.I . is now making a study of the rigid frame bridge. It is hoped that at some time in the near future a theory, more in keeping with the true behavior of the skewed rigid frame, will be developed. The Committee has decided that model tests offer a convenient solution to many of the problems arising in the development of a new theory. It is the purpose of this thesis to find the stress distribution at the knee of a skewed rigid frame bridge model for various loading conditions. / Master of Science

The routine procedure for designing bridge superstructures relies heavily on the past experience of the designer and is extremely time consuming and costly to try out alternative designs. Typically, a designer is more concerned about satisfying the design requirements laid down by the American Association of State Highway and Transportation Officials (AASHTO) than in coming up with the best possible design from the economic point of view. Thus, application of suitable mathematical programming techniques to determine optimal designs can result in tremendous savings. In this thesis, a procedure based on Generalized Geometric Programming (GGP) is developed to optimally design and select bridge superstructures. The bridge superstructure design problems are formulated as GGP problems incorporating all the design considerations as specified by AASHTO and the Virginia Department of Transportation (VDOT). A primal based algorithm is used in which, the resulting optimization problems are transformed to the solution of a series of Linear Programming problems that are easy to solve. A computer implementation of the algorithm is also developed. The software is extremely versatile and user friendly. It provides several options to help determine the optimal solution under varying design conditions, and is implemented on several representative problems provided by VDOT. Comparison of the resulting optimal with the existing designs promises huge savings in terms of both cost and effort. The methodology that is developed can be used to solve other Engineering Designs Problems as well. / Master of Science

Gusset plate connections are commonly used in steel truss bridges to connect individual members together at a node. Many of these bridges are classified as non-load-path-redundant bridges, meaning a failure of a single truss member or connection could lead to collapse. Current gusset plated design philosophy is based upon experimental work from simplified, small-scale connections which are seldom representative of bridge connections. This makes development of a refined methodology for conducting high-fidelity strength capacity evaluations for existing bridge connections a highly desirable goal. The primary goal of this research effort is to develop an analytical model capable of evaluating gusset plate stresses and ultimate strength limit states. A connection-level gusset connection model was developed in parallel with an experimental testing program at Oregon State University. Data was collected on elastic stress distributions and ultimate buckling capacity. The analytical model compared different bolt modeling techniques on their effectiveness in predicting buckling loads and stress distributions. Analytical tensile capacity was compared to the current bridge gusset plate design equations for block shear. Results from the elastic stress analysis showed no significant differences between the bolt modeling techniques examined, and moderate correlation between analytical and experimental values. Results from the analytical model predicted experimental buckling capacity within 10% for most of the bolt modeling techniques examined. Tensile capacity was within 7% of the calculated tensile nominal capacity for all bolt modeling techniques examined. A preliminary parametric study was conducted to investigate the effects of member flexural stiffness and length on gusset plate buckling capacity, and showed an increase in member length or decrease in member flexural stiffness resulted in diminished gusset plate buckling capacity.