Most of existing North American bridge infrastructure is reported to be deficient. Present infrastructure management mainly relies on qualitative evaluation, where bridge safety and serviceability are judged through routine visual inspection. With the successive increase in the number of severely deficient bridges and the limited available resources, it is crucial to develop a performance-based quantitative assessment evaluation approach that enables an accurate estimation of aging bridges ultimate and seismic capacities and ensures their serviceability. Reinforcement corrosion is the main cause of most of North American concrete infrastructure deterioration. Experimental investigations prove that reinforcement corrosion results in reduction of the steel reinforcement cross sectional area, localized (or global in very extreme cases) loss of bond action, concrete spalling, loss of core concrete confinement, and structural collapse. Field observations show that damage due to reinforcement corrosion in reinforced concrete (RC) bridge columns is localized in highly affected zones by splash of deicing water. In this thesis, an innovative performance-based semi-quantitative assessment framework is developed using newly developed simplified nonlinear static and dynamic finite element analysis approaches. The framework integrates the bridge’s available design and after-construction information with enhanced inspection and additional material testing as sources for accurate input data. In order to evaluate the structural performance and the capacity of the corrosion-damaged bridge columns, four nonlinear static and dynamic analysis approaches have been developed: (i) simplified nonlinear sectional analysis (NLSA) approach that presents the basis of the analysis approaches to estimate the ultimate and seismic capacities, and serviceability of bridge columns; (ii) simplified nonlinear finite element analysis (NLFEA) approach, which enables estimating the ultimate structural capacity of corrosion-damaged RC columns; (iii) simplified hybrid linear/nonlinear dynamic finite element analysis (SHDFEA) approach to evaluate the serviceability of the bridge; and, (iv) simplified non-linear seismic analysis (SNLSA) approach to evaluate the seismic capacity of the bridge columns. The four analysis approaches are verified by comprehensive comparisons with available test experimental and analytical results. The proposed semi-quantitative assessment framework suggests three thresholds for each performance measure of the evaluation limit states to be decided by the bridge management system team. Case studies are presented to show the integrity and the consistency of using the proposed assessment framework. The proposed assessment framework together with the analysis approaches provide bridge owners, practicing engineers, and management teams with simplified and accurate evaluation tools, which lead to reduce the maintenance/rehabilitation cost and provide better safety, and reduce the variation in the data collected using only traditional inspection methods.

The purpose of this thesis is to demonstrate that two-girder or two-web structural systems can be employed to design efficient bridges with an adequate level of redundancy. The issue of redundancy in two-girder bridges is a constraint for the bridge designers in North America who want to take advantage of efficiency in this type of structural system. Therefore, behavior of two-girder or two-web structural systems after failure of one main load-carrying component is evaluated to validate their safety. A procedure is developed to perform system-level reliability analysis of bridges. This procedure is applied to two bridge concepts, a twin steel girder with composite deck slab and a concrete double-T girder with unbonded external tendons. The results show that twin steel girder bridges can be designed to fulfill the requirements of a redundant structure and the double-T girder with external unbonded tendons can be employed to develop a robust structural system.

The purpose of this thesis is to demonstrate that two-girder or two-web structural systems can be employed to design efficient bridges with an adequate level of redundancy. The issue of redundancy in two-girder bridges is a constraint for the bridge designers in North America who want to take advantage of efficiency in this type of structural system. Therefore, behavior of two-girder or two-web structural systems after failure of one main load-carrying component is evaluated to validate their safety. A procedure is developed to perform system-level reliability analysis of bridges. This procedure is applied to two bridge concepts, a twin steel girder with composite deck slab and a concrete double-T girder with unbonded external tendons. The results show that twin steel girder bridges can be designed to fulfill the requirements of a redundant structure and the double-T girder with external unbonded tendons can be employed to develop a robust structural system.

No description available.

Bridges form a vital link in the physical infrastructure and must be maintained in a "safe working order" at all times. It is estimated that there are currently 20,000 timber road bridges in service throughout Australia. Increasing demands on these bridges due to heavier and faster moving loads, together with deterioration are placing these aging structures at a higher risk of collapse. Unfortunately, many local governments and government departments have neglected the benefits of preventative maintenance and have opted for "just in time" repairs. This is especially true for timber bridges. This past neglect has placed bridge stock in a poor state that is only now being recognised as a significant problem. A key component of this research is to develop improvements to this current situation. This research thesis generates detailed knowledge on the load carrying capacities of timber bridges and new non destructive testing techniques that can be substituted for conventional testing procedures. For the first time guidelines have been developed for undertaking capacity assessment on timber bridges by specifying intervention levels for notched timber and limiting maximum allowable strains in timber members. This newly acquired knowledge will enable Asset Managers to more accurately determine the capacity of sniped timber bridge girders to enable appropriate retrofitting and maintenance while also allowing the safe movement of heavy vehicles. The knowledge generated through destructive testing of timber girders and the analysis of the vast amount of experimental data has enabled the first instance of developing specifications for replacement girders. These specifications detail both functional and performance related targets for three different types of replacement girders. Testing of these replacement girders also demonstrates that through some minor modifications that the specification targets can be met. The outcomes of this thesis provide an innovative approach to accessing the condition and capacity of timber girders and to increasing the safety and life of timber bridges in Queensland. By using new techniques such as Non-destructive testing, species identification and limiting maximum allowable strains, as described in this thesis, the road transport network can be safety used by heavy and permit vehicles. It is only through the effective management of timber bridge maintenance and rehabilitation that Australia can have an efficiently running road transportation network.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 223-229). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 223-229). Also available on the Internet.

Hoists and cranes exist in many contexts around the world, often carrying veryheavy loads. The safety for the user and bystanders is of utmost importance. Thisthesis investigates whether it is possible to perform fault detection on a systemlevel, measuring the inputs and outputs of the system without introducing newsensors. The possibility of detecting dangerous faults while letting safe faultspass is also examined.A mathematical greybox model is developed and the unknown parametersare estimated using data from a labscale test crane. Validation is then performedwith other datasets to check the accuracy of the model. A linear observer of thesystem states is created using the model. Simulated fault injections are made,and different fault detection methods are applied to the residuals created withthe observer. The results show that dangerous faults in the system or the sensorsthemselves are detectable, while safe faults are disregarded in many cases.The idea of performing model-based fault detection from a system point ofview shows potential, and continued investigation is recommended.

O presente trabalho faz uma comparação entre resultados obtidos por um método prático e simplificado e o Método dos Elementos Finitos na determinação de esforços solicitantes em pontes celulares curvas em planta, submetidas à protensão. Na primeira parte, teórica, apresenta-se os conceitos fundamentais das vigas celulares curvas, mostrando-se principalmente as diferenças de seu comportamento em relação ao das vigas retas. Em seguida discute-se a protensão de peças de concreto com ênfase no seu efeito em vigas curvas. Finalmente, são apresentados os métodos a serem utilizados no cálculo, percorrendo as diversas situações de carregamento, mas sempre enfatizando o carregamento de protensão. Na segunda parte, prática, é elaborado um estudo comparativo, tomando-se como exemplo duas pontes rodoviárias em viga unicelular, sendo uma biapoiada e outra contínua, submetidas a protensão. Após a construção de modelos, tais vigas são processadas através de um programa comercial de elementos finitos. Alguns resultados são então comparados com aqueles obtidos através do método simplificado, elaborando-se assim observações práticas e que possam ser utilizadas nos projetos corriqueiros de engenharia. / This work compares the results from a practical and simplified method and the Finite Element Method to determinate section efforts in prestressed box-girder curved bridges. The first part, theoretical, introduces the basic principles of the cellular curved beams, showing the differences of its behavior comparing with straight beams. Next, prestressing of concrete members is discussed, emphasizing its effects in curved beams. Finally, calculation methods are presented, covering many loading situations, but always emphasizing the prestressing load. In the second part, practical, a comparative study is elaborated, taking two road unicellular bridges, one simply supported and another continuum, submitted to prestressing load. After models construction, such beams are calculated using a commercial software of Finite Element Method. Then, some results are compared with those calculated by simplified method, thus elaborating practical comments that can be used in the current designs of engineering.

Based on the definition given in the AASHTO LRFD Bridge Design Specifications, twin steel box-girder bridges are classified as bridges with fracture critical members (FCMs), in which a failure of a tension member is expected to lead to a collapse of the bridge. However, a number of such bridges with either a partial or full-depth crack in one girder have been reported and are still providing service without collapsing. The main objective of this research project is to understand the behavior of twin steel box-girder bridges and to develop methods for evaluating their redundancy level in the event of the fracture of one tension member. The research project included an experimental investigation on a small-scale steel twin box-girder bridge, field testing of a full-scale twin box-girder, analysis of existing research and design data, and an extensive amount of numerical analyses carried out on calibrated 3-D nonlinear finite element models. The results from this study provide in-depth understanding of twin steel box-girder bridge behavior before and after a fracture in the tension member occurs. In addition to the experimentally verified finite element method, the report also proposes simplified methods for evaluating the load-carrying capacity of twin steel box-girder bridges under vii concentrated loads and provides a list of important factors that could control the reserve capacity of the damaged bridge. The main conclusion of this research is that the redundancy exists in twin steel boxgirder bridges in an event that a fracture of a tension member(s) takes place. This research project also provides a comprehensive roadmap for assessing the redundancy of twin steel box-girder bridges in which the elements of the roadmap are identified, and solutions for several of the steps are provided. The development of solutions for remaining steps of the roadmap is proposed for a future research.