In this study, dynamic effects on high speed railway bridges under moving traffic are investigated. Within this context, the clear definition of the possible dynamic effects is provided and the related studies that exist in literature are investigated. In the light of those studies, analytical procedures that are defined to find the critical dynamic responses such as deflections, accelerations and resonance conditions are examined and a MatLab programming language is written to obtain the responses for different train loading and velocity values. The reliability of the written program is conformed by comparing the results with the related studies in literature. In addition to the analytical procedures, the approaches in the European standards concerning the dynamic effects of railway traffic are defined. A case study is investigated for a bridge that is in the scope of the Ankara-Sivas High Speed Railway Project. The related bridge is modeled by using finite element program, SAP2000 according to the definitions that are stated in European standards. The related high speed railway bridge is analysed with a real train which is French TGV together with the HSLM trains that are defined in Eurocode and the results obtained are compared with each other. This study also includes the analysis of the bridges performed for 7 different stiffness and 3 different mass values to determine the parameters affecting dynamic behaviour.

Proper bridge design is based on consideration of structural, hydraulic, and geotechnical conformities at an optimum level. The objective of this study is to develop an optimization-based methodology to select appropriate dimensions for components of a river bridge such that the aforementioned design aspects can be satisfied jointly. The structural and geotechnical design parts uses a statisticallybased technique, artificial neural network (ANN) models. Therefore, relevant data of many bridge projects were collected and analyzed from different aspects to put them into a matrix form. ANN architectures are used in the objective function of the optimization problem, which is modeled using Genetic Algorithms with penalty functions as constraint handling method. Bridge scouring reliability comprises one of the constraints, which is performed using Monte-Carlo Simulation technique. All these mechanisms are assembled in a software framework, named as AIROB. Finally, an application built on AIROB is presented to assess the outputs of the software by focusing on the evaluations of hydraulic &ndash / structure interactions.

Integral bridges (IBs) are defined as a class of rigid frame bridges with a single row of piles at the abutments cast monolithically with the superstructure. In the last decade, IBs have become very popular in North America and Europe as they provide many economical and functional advantages. However, standard design methods for IBs have not been established yet. Therefore, most bridge engineers depend on the knowledge acquired from performance of previously constructed IBs and the design codes developed for conventional jointed bridges to design these types of bridges. This include the live load distribution factors used to account for the effect of truck loads on bridge components in the design as well as issues related to the seismic design of such bridges. Accordingly in this study issues related to live load effects as well as seismic effects on IB components are addressed in two separate parts. In the first part of this study, live load distribution formulae for IB components are developed and verified. For this purpose, numerous there dimensional and corresponding two dimensional finite element models (FEMs) of IBs are built and analyzed under live load. The results from the analyses of two and three dimensional FEMs are then used to calculate the live load distribution factors (LLDFs) for the components of IBs (girders, abutments and piles) as a function of some substructure, superstructure and soil properties. Then, live load distribution formulae for the determination of LLDFs are developed to estimate to the live load moments and shears in the girders, abutments and piles of IBs. It is observed that the developed formulae yield a reasonably good estimate of live load effects in IB girders, abutments and piles. In the second part of this study, seismic performance of IBs in comparison to that of conventional bridges is studied. In addition, the effect of several structural and geotechnical parameters on the performance of IBs is assessed. For this purpose, three existing IBs and conventional bridges with similar properties are considered. FEMs of these IBs are built to perform nonlinear time history analyses of these bridges. The analyses results revealed that IBs have a better overall seismic performance compared to that of conventional bridges. Moreover, IBs with thick, stub abutments supported by steel H piles oriented to bend about their strong axis driven in loose to medium dense sand are observed to have better seismic performance. The level of backfill compaction is found to have no influence on the seismic performance of IBs.

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.

In highway bridge construction, composite curved girder bridges are becoming more popular recently. Reduced construction time, long span coverage, economics and aesthetics make them more popular than the other structural systems. Although there exist some methods for the analysis of such systems, each have shortcomings. The use of Finite Element Method (FEM) among these methods is limited except in the academic environments. The use of commercial FEM software packages in the analysis of such systems is cumbersome as it takes too much time to form a model. Considering such problems a computational software was developed called UTRAP in 2002 which analyzes bridges for construction loads by taking into account the early age deck concrete. As the topic of this thesis work, this program was restructured and new features were added. In the following thesis work, the program structure, modeling considerations and recommendations are discussed together with the parametric studies.

ABSTRACT EFFECTS OF VERTICAL EXCITATION ON SEISMIC PERFORMANCE OF HIGHWAY BRIDGES AND HOLD-DOWN DEVICE REQUIREMENT Domani&ccedil / , Kemal Arman M.S., Department of Civil Engineering Supervisor: Assist. Prof. Dr. Alp Caner February 2008, 152 pages Most bridge specifications ignore the contribution of vertical motion in earthquake analyses. However, vertical excitation can develop significant damage, especially at bearing locations as indeed was the case in the recent 1999 izmit Earthquake. These observations, combined with recent developments in the same direction, supplied the motivation to investigate the effects of vertical component of strong ground motion on standard highway bridges in this study. Reliability checks of hold-down device requirements per AASHTO Bridge Specifications have been conducted in this context. Six spectrum compatible accelerograms were generated and time history analyses were performed to observe the uplift at bearings. Selected case studies included precast pre-stressed I-girders with concrete slab, composite steel I-girders, post-tensioned concrete box section, and composite double steel box section. According to AASHTO specifications, hold-down devices were required in two cases, for which actual forces obtained from time history analyses have been compared with those suggested per AASHTO. The only non-linearity introduced to the analyses was at the bearing level. A discussion of effects on substructure response as well as compressive bearing forces resulting from vertical excitation is also included. The results of the study confirmed that the provisions of AASHTO governing hold-down devices are essential and reasonably accurate. On the other hand, they might be interpreted as well to be suggesting that vertical ground motion components could also be included in the load combinations supplied by AASHTO, especially to be able to estimate pier axial forces and cap beam moments accurately under combined vertical and horizontal excitations.

Current seismic design approach of bridge structures can be categorized into two distinctive methods: (i) force based and (ii) performance based. AASHTO LRFD seismic design specification is a typical example of force based design approach especially used in Turkey. Three different importance categories are presented as &ldquo / Critical Bridges&rdquo / , &ldquo / Essential Bridges&rdquo / and &ldquo / Other Bridges&rdquo / in AASHTO LRFD. These classifications are mainly based on the serviceability requirement of bridges after a design earthquake. The bridge&rsquo / s overall performance during a given seismic event cannot be clearly described. Serviceability requirements specified for a given importance category are assumed to be assured by using different response modification factors. Although response modification factor is directly related with strength provided to resisting column, it might be correlated with selected performance levels including different engineering response measures. Within the scope of this study, 27216 single circular bridge column bent models designed according to AASHTO LRFD and having varying column aspect ratio, column diameter, axial load ratio, response modification factor and elastic design spectrum data are investigated through a series of analyses such as response spectrum analysis and push-over analysis. Three performance levels such as &ldquo / Fully Functional&rdquo / , &ldquo / Operational&rdquo / and &ldquo / Delayed Operational&rdquo / are defined in which their criteria are selected in terms of column drift measure corresponding to several damage states obtained from column tests. Using the results of analyses, performance categorization of single bridge column bents is conducted. Seismic responses of investigated cases are identified with several measures such as capacity over inelastic demand displacement and response modification factor.

Long span bridges are susceptible to wind. Hence it is important to study their wind-induced vibrations to avoid any probable structural failures. In this thesis, the results of an experimental and computational investigation of the aerodynamic characteristics of trapezoid bridge deck cross-sections with three different aspect ratios (10, 12 and 15) and four different side angles (75&ordm / , 60 &ordm / , 45 &ordm / and 30 &ordm / ) are analyzed and presented. The flow around rigid fixed bridge deck models is investigated to obtain the relevant aerodynamic coefficients and the vortex shedding frequency and Strouhal number. Two dimensional unsteady Reynolds Averaged Navier-Stokes equations are solved using commercial CFD software at different Reynolds numbers. The numerical results are compared with the experimental data obtained by testing the model bridge decks geometries in a low speed wind tunnel. The results of this study demonstrate that the models aerodynamic parameters except their lift coefficient are almost dependent on the aspect ratio. In addition, the influence of side angle on all aerodynamic parameters has to be taken in account.

Infrastructure systems are crucial facilities. They supply the necessary transportation, water and energy utilities for the public. However, while aging, these systems gradually deteriorate in time and approach the end of their lifespans. As a result, they require periodic maintenance and repair in order to function and be reliable throughout their lifetimes. Bridge infrastructure is an essential part of the transportation infrastructure. Bridge management systems (BMSs), used to monitor the condition and safety of the bridges in a bridge infrastructure, have evolved considerably in the past decades. The aim of BMSs is to use the resources in an optimal manner keeping the bridges out of risk of failure. The BMSs use the lifetime performance curves to predict the future condition of the bridge elements or bridges. The most widely implemented condition-based performance prediction and maintenance optimization model is the Markov Decision Process-based models (MDP). The importance of the Markov Decision Process-based model is that it defines the time-variant deterioration using the Markov Transition Probability Matrix and performs the lifetime cost optimization by finding the optimum maintenance policy. In this study, the Markov decision process-based model is examined and a computer program to find the optimal policy with discounted life-cycle cost is developed. The other performance prediction model investigated in this study is a probabilistic Bi-linear model which takes into account the uncertainties for the deterioration process and the application of maintenance actions by the use of random variables. As part of the study, in order to further analyze and develop the Bi-linear model, a Latin Hypercube Sampling-based (LHS) simulation program is also developed and integrated into the main computational algorithm which can produce condition, safety, and life-cycle cost profiles for bridge members with and without maintenance actions. Furthermore, a polynomial-based condition prediction is also examined as an alternative performance prediction model. This model is obtained from condition rating data by applying regression analysis. Regression-based performance curves are regenerated using the Latin Hypercube sampling method. Finally, the results from the Markov chain-based performance prediction are compared with Simulation-based Bi-linear prediction and the derivation of the transition probability matrix from simulated regression based condition profile is introduced as a newly developed approach. It has been observed that the results obtained from the Markov chain-based average condition rating profiles match well with those obtained from Simulation-based mean condition rating profiles. The result suggests that the Simulation-based condition prediction model may be considered as a potential model in future BMSs.