Current specifications of the American Association of State Highway and Transportation Officials (AASHTO) include restrictions on the live load deflections of highway bridge girders. Conventional practice, which utilizes hand calculations to estimate girder deflections, assumes that all girders of a highway bridge deflect to the same degree. In addition, the conventional equations do not account for AASHTO specifications requiring the evaluation of extreme force effects. As such, the accuracy of the conventional approach for calculating girder deflections is under question. The purpose of this study is, therefore, to check the accuracy of the conventional approach by testing the two aforementioned assumptions made by the equations. A composite steel girder bridge example has been selected from Design of Highway Bridges: An LRFD Approach, Third Edition by Richard M. Barker and Jay A. Puckett. The design example specifies the dimensions for all structural elements, as well as the girder type and spacing. The design example does not include specifications for the bridge bearings, and so bearing pads are designed according to the Illinois Department of Transportation (IDOT) Bridge Manual (2012). This study consists of two steps. First, a hand-calculated live load deflection for the bridge example is derived from the conventional approach (assuming all girders deflect to the same degree and without consideration for extreme force effects). Next, the finite element analysis software, NISA/Display IV, is utilized to model and analyze the real-world deflections of the bridge model. Three live loading conditions are applied to the finite element model, in accordance with AASHTO specifications. For first live load condition, the live loads are positioned at the center of each traffic lane. The second and third conditions apply extreme force effects to an interior girder and exterior girder, respectively. The results for each finite element analysis are then compared with the conventional, hand-calculated deflection. The results of this study contradict the two aforementioned assumptions made by the conventional equations for calculating girder deflections. Firstly, this study demonstrates that interior girders experience a significantly greater live load deflection than interior girders. More importantly, the results indicate that the conventional equations underestimate the live load deflection of an interior girder subjected to extreme force effects. None of the results, however, suggest that the bridge example is at risk of excessive deformation, and so the extent to which these drawbacks present a concern can be left to the discretion of the engineer.

Many older bridges and tunnels were constructed using standards by now many decades out-of-date, at a time when trucks and other large vehicles were smaller. A bridge or tunnel strike is an incidence in which a vehicle, typically a lorry (truck) or double-decker bus, tries to pass under a bridge or tunnel that is lower than its height, subsequently colliding with the structure. These strikes lead to an increased cost of bridge repairs, clogged up roadways and increased potential for catastrophic events: hazardous spillage and/or total collapse. Today, Network Rail reports on average a strike every 4.5 hours. There are a number of reasons why strikes occur, and why drivers of heavy goods vehicles sometimes fail to recognise the warning signs, consequently striking the bridge or tunnel. At first glance, it may seem like the problem is a fairly easy one to solve; however, no matter how well planned the road system, human error is an ever-present risk. The research proposes to address the problem of bridge and tunnel strike prevention and management. The intent of the research is to develop an affordable, reliable and robust early warning over-height detection system bridge-owners can implement at locations with high strike occurrences. The research aims to test and validate a novel vision-based system using a single camera to accurately detect over-height vehicles using a set of optimised parameters. The system uses a camera installed at the offending height, which acts as an “over-height plane” formed by the averages of the maximum allowable heights across all lanes in a given traffic direction. Any vehicle exceeding this plane is analysed within a region of interest using a trigger-based approach for accurate detection and driver warning. If the vehicle is deemed to be over-height, a warning is issued to the driver. As a result, prolonging life expectancy of structures while decreasing the cost of repairs, maintenance and inspections.

Master of Science / Civil Engineering / Hayder Rasheed / Reverse diagonal shear cracking at the supports of many reinforced concrete girders is a phenomenon affecting a number of KDOT’s low-volume bridges built in the early-to-mid 1900’s. This phenomenon is not addressed in the AASHTO Bridge Design Manual (2002) or ACI specifications. This study investigates the causes of this cracking and creates BRIDGE (Bridge Rating of Inclined Damage at Girder Ends), an Excel-based software to determine the load rating of a user specified bridge exhibiting reverse diagonal shear cracking at the girder supports. A user-interface is created which allows a user to create a grillage model of an existing bridge and to place various rating trucks on the bridge. Equivalent flexibility analysis is used to distribute the truck live loads from within the deck panels to the surrounding girders and diaphragms. Stiffness matrices are utilized to find the nodal displacements then the reactions at the girder supports caused by the truck live loads and bridge dead load. These reactions are checked against RISA software models to test the accuracy of the stiffness matrix application. ABAQUS FE models and Mohr’s circle stress distribution is used to find the driving and clamping forces on the crack. These forces are caused by resolving the dead and live load reactions and the friction force generated between the concrete girder and the rusty steel bearing pad along the shear crack orientation. These clamping and driving forces are used, along with the simplified modified compression field theory to determine the shear capacity of each girder at the reverse cracks. A modified version of Equation 6B.4.1 from the Manual for Bridge Evaluation (2011) is used to find the operating and inventory rating factors for the bridge.

To meet the economic, social and infrastructure needs of the community for safe and efficient transportation systems, long span bridges have been built throughout the world. Long span bridges are one of the most challenging kinds of structures in civil engineering. The cable-stayed bridges are of great interest mainly as an alternative and a more economic solution than the one of suspension bridges. In addition, the fiber reinforced polymer (FRP) composites are, nowadays, successfully used for constructing modern bridges, where the significant weight saving provides additional benefits. Because of the great flexibility, modern long-span cable-stayed bridges are usually very susceptible to dynamic loads especially to the earthquake and strong winds. Therefore, the earthquake-resistant and wind-resistant designs become one of key issues for successful construction of bridges. The objective of the present research is to develop a very efficient spline finite strip technique, for modelling and analysis of both conventional and hybrid FRP cable-stayed bridges. The study falls into the categories of bending, free vibration, seismic, and aerodynamic flutter analysis. The spline finite strip method (SFSM) is one of the most efficient numerical methods for structural analysis of bridges, reducing the time required for estimating the structural response without affecting the degree of accuracy. In the finite strip method, the degrees of freedom could be significantly reduced due to the semi-analytical nature of this method. However, the previous versions of SFSM are not able to model the entire bridge system. For that reason, the structural interactions between different structural components of the bridge could not be handled. In addition, the vibrations and displacements of the towers and cables could not be investigated. In the present formulation, all these obstacles have been eliminated. Moreover, the proposed finite strip technique is very efficient and accurate due to the drastic reduction in the formulation time, simplicity of data preparation, rapid rate convergence of the results, and the semi-analytical nature. Last but not least, and for the first time, a fully finite strip solution is extended to the area of wind engineering. Using the spline finite strip discretization, the aerodynamic stiffness and mass properties of the long-span cable-stayed bridge are derived. The aerodynamic properties along with the structural properties of long-span plates and bridges are formulated in the aerodynamic equation of motion and are used to analyze the flutter problem. The accuracy and efficiency of the proposed advanced finite strip method is verified against the finite element and field measurement results. The results demonstrate that this methodology and the associated computer code can accurately predict the dynamic and aerodynamic responses of the conventional and FRP long-span cable-stayed bridge systems. The outcome of the present research will lead to a comprehensive structural analysis of bridges in the framework of the proposed discretization which is more efficient and straightforward than the finite element analysis.

O trabalho tem por objetivo o estudo teórico e experimental de pontes protendidas de madeira para pequenos vãos utilizando madeiras de reflorestamento. Para esta finalidade foram avaliados os parâmetros elásticos destas madeiras e o efeito da presença de juntas de topo na rigidez longitudinal do tabuleiro da ponte. A metodologia utilizada para obter os parâmetros elásticos é a experimentação em laboratório de placas ortotrópicas submetidas à torção. Os efeitos das juntas de topo foi verificado em ensaio de modelo reduzido e comparado a uma simulação numérica em computador utilizando o programa AnSYS 5.2 de elementos finitos, módulo Shell, com propriedades ortotrópicas. Finalmente é proposto um critério de dimensionamento para estas estruturas a partir dos resultados experimentais obtidos e de disposições de códigos internacionais. / The aim of this work is the theoretical and experimental study of prestressed timber bridges to small spans using reforestation species. To this purpose elastics characteristics are analysed as well the butt joint effects on timber deck stiffeness. The experimental methodology was used to find the elastics characteristics is torsional tests in orthotropic plates. The butt joints effects was made in a reduced model and the results compared with a computer numerical analysis using the software AnSYS 5.2, shell module, with ortotropic characteristics. Finally, a design criteria was proposed to these structures using the experimental results obtained and the international codes recomendations.

[No abstract submitted] / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

<p>This report defines a present problem with U.S. bridges and suggests several reasons for bridge infrastructure deterioration and degradation, such as traffic overload, expired life cycles, environmental and operational conditions, and budget cuts. The most commonly used nondestructive evaluation (NDE) methods for determining the health of bridge infrastructure are summarized and compared. Advantages and disadvantages of each NDE technique are provided, and the lack of an adequate method which can quantitatively monitor the structural integrity of bridges is noted.</p> <p>This report then discusses the possibility of health monitoring sensor systems for the quantitative NDE of bridge infrastructure. Several types of sensors that may be used to collect paSSlve and quantitative data related to the structural integrity of bridges are evaluated, and the extrinsic Fabry-Perot interferometric (EFPI) fiber optic sensor is suggested as the preferred sensor.</p> <p>The fabrication processes and operational principles of EFPIs are presented. Two case studies which demonstrate the performance of EFPI sensors when used in health monitoring sensor systems are provided. Finally, a design criteria checklist suggests several questions that need to be asked (or more thoroughly defined) concerning the usefulness, reliability, durability, and sensitivity of EFPI-based health monitoring sensor systems.</p> / Master of Science

The new Ashton Bridge is a concrete tied-arch structure with a cable-supported deck, which spans 110 metres below the arching ribs. The tie-beam members, connecting the arch ribs, each have six longitudinal tendons that have primarily straight profiles. The author set out to validate the structural behaviour of the tie-beams, after the post-tensioning construction stage. This objective was achieved by validating selected finite element model parameters with field conducted tests. The input parameter, which is the prestress loading onto the structure, was validated with tendon elongation measurements and tendon lift-off tests. The output parameter, which is the strain and displacement response of the structure, was verified by measuring the elastic deck shortening and the strain gauge readings. Lower tendon extensions were encountered during tensioning. This required calibration of the friction coefficients and model updating. Lift-off tests and deck shortening measurements provided and order size estimation of the structural behaviour, but was not adequate for model validation. The strain gauge readings showed a close correlation with the expected strain state of the structure and offered insight into the behaviour of the structure during post-tensioning. The methods described in this dissertation may be used for validating the structural behaviour of concrete bridges subject to post-tensioning. Suggestions for improving tendon lift-off tests and deck shortening measurements are also presented.

Many steel railway bridges in Europe are older than 50 years whilethey are subjected to higher loads than they were originally designedfor. As many of these bridges are approaching the end of their designlife it is crucial to carry out accurate fatigue assessments in order toensure their safety and keep them in service. Usually the influence ofdynamics on fatigue damage is taken into account using dynamicamplification factors from design codes whereas the actual influenceof dynamics has not been thoroughly studied.   During this study the importance of dynamics on fatigue damage isexamined on two specific examples, namely the Söderstöm Bridgeand the Åby älv bridge, which are good examples of open deckbridges that are common among steel railway bridge population.   Different train speeds, the cross beam effect and load distributionwere studied in order to assess the importance of dynamics on fatiguedamage. Three dimensional finite element models were created andlater modified to perform dynamic analysis. Moving point loads wereused to simulate the loading of moving trains. Fatigue damages werecalculated at the various locations to evaluate the influence ofdynamics on fatigue damage.   The results show that the dynamics has small influence on fatiguedamage at studied speeds and damage is not dependent on speed.Assessed cross beam effect was not detected on studied bridges interms of dynamics, but has great influence in terms of statics.

This research focuses on the creation, validation, automation, and deployment of a nondestructive vertical electrical impedance (VEI) bridge deck assessment apparatus. A multichannel impedance analyzer with a moving platform is developed that can assess the deterioration state of a bridge deck without stationary traffic control. The multichannel apparatus is capable of taking over 500 impedance samples a second and can scan a bridge deck over 500 times faster than more traditional techniques. This research also shows VEI measurements are inversely proportional to the diffusivity of ions through concrete and that an impedance measurement frequency of 25 kHz is the most predictive measurement frequency of diffusivity. Finally, this research demonstrates the utility of VEI measurements by inspecting five asphalt overlaid bridges. VEI measurements were sensitive to defects in membranes and are one of the only nondestructive measurements that provide useful information about the deterioration state of asphalt overlaid bridge decks.