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.

The purpose of this study is to investigate how accurately the distribution factor method estimates the live load deflections under the principles of the 2012 AASHTO LRFD Bridge Design Specifications (AASHTO LRFD specifications) compared to the results of the NISA finite element analysis software. The simple span bridge model analyzed is developed very similarly to the design example of the PCI Bridge Design Manual. The main difference is a shorter span length and smaller AASHTO-PCI bulb tee sections. Three main finite element models are created to estimate the live load deflections under the recommended live load conditions as per AASHTO LRFD specifications. The first model is simulated with simple support conditions. The purpose of this model is two-fold: compare the deflections to the distribution factor method and to the deflections of the second model that is simulated with elastomeric steel reinforced bearing pads. Thus, the stiffnesses of the elastomeric bearing pads of the second model are varied within the AASHTO LRFD specifications acceptable limits and under low temperature conditions the stiffness is increased accordingly for two cases. The purpose is to investigate if the stiffness have any significant affect on the deflections of the girders. Then a third model is created to investigate if the removal of the intermediate diaphragms have any affect on the deflections. The results of the first and second models, including the models with the allowed varied stiffnesses of the bearing pads, found only the interior girders deflecting up to 4% more and the exterior girders were deflecting up to 5.55% less than the estimates of the distribution factor method. In the case when the diaphragms are removed, the deflections of the inner most interior girders are deflecting up to 10.85% more compared to the same girders of the model which includes the intermediate diaphragms and the bearing pads. In the unique case of the second model where the bearing pads may stiffen significantly under low temperatures, the girders are deflecting up to 23% less than when at room temperature conditions. All these findings and other summarized results are discussed in greater detail in this study.

Bridge load rating is a procedure to determine the live load carrying capacity of a bridge. This rating is generally given out on a two-year period, which leaves the structural capacity unknown for this time interval. Conventional bridge load rating is obtained according to the bridge inspection results and commercial bridge rating software. However, this approach cannot effectively reflect actual live load carrying performance of the bridge, due to intrinsic limitation of visual inspection. Structural sensing has been utilized for measuring realistic structural behaviors to reflect the live load carrying capacity. However, this expensive and time-consuming process requires a known-weight vehicle and a substantial number of sensors under controlled full-scale field test conditions. In this research, a continuous live load performance index (LLPI) is proposed to monitor the live load capacity that the bridge can withstand without knowing the vehicle weight while also using a limited number of sensors. The LLPI uses existing bridge load rating methodology, in conjunction with experimental data and numerical simulations, to generate a value that describes the performance of the bridge due directly to the live load applied. Furthermore, the LLPI procedure utilizes an advanced state estimation algorithm, known as the Kalman Filter, to estimate the strain responses of the bridge at various locations while using a limited number of sensors. This procedure allows for an efficient structural health monitoring approach to determine the live load carrying capacity that the bridge can withstand. This research uses a lab-scaled truss structure with known properties for numerical and experimental validation. Because of this, this paper proposes a framework as to which the live load carrying performance can be monitored in real time. Future updates include testing on a real-life bridge structure while also determining optimal sensor placement for obtaining the LLPI. This research looks to develop a new live load performance index (LPPI) by considering: (1) the benefits and limitations of conventional bridge load rating approach, (2) the system identification and multi-metric data acquisition for the bridge structure, (3) numerical modeling and updating to best reflect the current dynamic properties of the bridge, (4) augmented Kalman Filter to estimate structural responses at various unknown locations, (5) LLPI formulation using experimental data, current bridge load rating methodology, and model-response estimations. The results obtained from this research provide a progressive live load capacity performance template to promote the advancement in civil infrastructure smart monitoring.

Adjacent box beam bridges are economical bridge systems for accelerated bridge construction. The box beams are constructed at precast plants and are traditionally connected by a shear key filled with grout. This system is ideal for short spans with low clearance restrictions. However, due to the grout deteriorating and debonding from the precast concrete in the shear key, reflective cracking propogates through the deck allowing water and chemicals to leak down into the joints. This can lead to the prestressing steel inside the precast member and the transverse tie steel corroding. This necessitates the bridge being rehabilitated or replaced which shortens the life-span of the bridge system and negates the economical value it had to begin with. This research project aimed to design a rehabilitation plan for an adjacent box beam bridge with deteriorated joints using Very High Performance Concrete (VHPC). VHPC was chosen as an economical alternative to the proprietary Ultra High Performance Concrete (UHPC) and extensive material tests were performed. The results of the material testing of VHPC and grout revealed that VHPC had higher compressive and tensile strengths, a higher modulus of elasticity, gained strength faster, bonded better to precast concrete, was more durable over time, and shrank less than conventional grout. The results of this research project were applied to rehabilitate the Buffalo Branch Bridge and further testing will be completed to determine the effectiveness of the rehabilitation. / Master of Science

The Hampton Roads Bridge-Tunnel is one of the oldest prestressed concrete structures in the United States. The 3.5 mile long twin structure includes the world's first underwater tunnel between two man-made islands. Throughout its 60 years in service, the harsh environment along the Virginia coast has taken its toll on the main load carrying girders. Concrete spalling has exposed prestressing strands within the girders allowing corrosion to spread. Some of the more damaged girders have prestressing strands that have completely severed due to the extensive corrosion. The deterioration has caused select girders to fail the necessary load ratings. The structure acts as an evacuation route for the coast and is a main link for the local Norfolk Naval Base and surrounding industry. Because of these constraints, load posting is not a viable option. Live load testing of five spans was performed to investigate the behavior of the damaged spans. Innovative techniques were used during the load test including a wireless system to measure strains. Two different deflection systems were implemented on the spans, which were located about one mile offshore. The deflection data was later compared head to head. From the load test results, live load distribution factors were developed for both damaged and undamaged girders. The data was also used by the local Department of Transportation to validate computer models in an effort to help pass the load rating. Overall, this research was at the forefront of the residual strength of prestressed concrete girders and the testing of in-service bridges. / Master of Science

O aumento nos limites de pesos estabelecidos pela legislação brasileira e o surgimento de novas combinações de veículos de carga nos últimos anos tornam necessária a verificação da segurança estrutural das pontes quando submetidas ao tráfego real. Este trabalho verifica o desempenho das obras de arte sob jurisdição do DER-SP através do índice de confiabilidade 'beta' e obtém limites para o peso de caminhões de modo a não comprometer sua integridade estrutural. São consideradas as superestruturas das pontes em concreto armado ou protendido, classes 36 e 45. Verifica-se o estado limite último nas seções transversais mais solicitadas por momento fletor positivo e negativo. No caso de pontes em concreto protendido, acrescenta-se o estado limite de formação de fissuras. Para a representação do tráfego real, é desenvolvido um modelo de carregamento móvel com base em pesagens de caminhões efetuadas em rodovias do estado de São Paulo. Admite-se a presença simultânea de veículos sobre a ponte e diferentes relações entre seus pesos. Os parâmetros estatísticos da resistência são determinados através da técnica de Monte Carlo. Apresenta-se os limites de peso em forma de equações, denominadas ECPLs (equações comprimento-peso limite), aplicáveis a quaisquer grupo de eixos consecutivos. Os resultados indicam restrições à circulação de algumas composições, especialmente ao rodotrem de 740 kN e 19,80 metros de comprimento. Considerando-se apenas o estado limite de serviço, as obras de arte classe 45 apresentam menores limites de peso devido à ponderação de ações durante o projeto / The increase in gross weight limits allowed by Brazilian legislation and the appearance of new truck configurations in last years require the assessment of bridges structural safety when submitted to real traffic. This thesis verifies the performance of the bridges under DER-SP jurisdiction using the reliability index 'beta' and obtains truck weight limits in order to guarantee its structural integrity. The superstructure of reinforced and prestressed concrete bridges, classes 36 and 45, is considered. The ultimate limit state is verified in cross sections submitted to critical positive and negative bending moments. In case of prestressed bridges, the tension limit state in concrete is added. To represent the real traffic, a live load model is developed based on weighting data collected from stations located at highways of the state of Sao Paulo. Multiple presence of vehicles over the bridge and different relations between weights are admitted. The statistical parameters of resistance are determined using the Monte Carlo technique. The gross weight limits are presented in the form of equations, known as bridge formulas, to be applied on any group of two or more consecutive axles. The results indicate restrictions to the traffic of some vehicles, especially the 740 kN and 19,80 meters length roadtrain. Considering only the serviceability limit state, bridges class 45 exhibit lower weight limits due to the load factors recommended by the code during design

This thesis presents an approach to evaluate and develop a live load model. Although the main purpose of this work is with the impact of truck traffic on bridges, the data presented in this work can be used in many engineering fields that are concerned with truck characteristics of geometry and weight. Data from two different WIM stations were considered. One in Fernão Dias highway in the State of São Paulo which is comprised of a same-direction two adjacent lanes and the sample is comprised of 20 months (September 2015 to August 2017). The second station is in Rio Grande do Sul State. This road is a same-direction three adjacent lanes. The sample is comprised of 78 days (March 2014 to June 2014) In order to evaluate and develop a new live load model, an approach to compute load effects in terms of bending moments and shear forces is proposed. It makes use of single and multiple truck presence to evaluate the live load effects for different bridge spans. Three cases of multiple presence are considered: following, side-by-side and staggered. The proposed approach to evaluate the multiple truck presence effects is compared with the approach used by AASHTO LRFD. The approach for estimating the bias factors shows that considering only full correlated trucks is too conservative, mostly for short spans where there is a lack of occurrences, especially following events. On the other hand, taking into account no correlation at all yields very low bias factors. At last, a more rational live load model was developed based on WIM data. Another purpose of this thesis is to use existing Brazilian bridges to calibrate the live load model as in NBR7188:2013. Reliability analysis is performed with sixty existing Brazilian bridges. The bridges are taken from different states of Brazil. Out of the sixty bridges, 39 are prestressed and 21 reinforced concrete bridges. Those bridges are located in five different states: Pernambuco, Ceará, Bahia, São Paulo, Minas Gerais. Probability of failure was estimated in terms of moment and shear for interior girders and box girders. Only ultimate state limit was considered. It was found that reliability indices are higher in prestressed bridges when compared to reinforced bridges. Also, the reliability indices tend to decrease as the span length increases. This means that for larger spans the probability of failure is higher than the ones for shorter spans. / Este trabalho apresenta uma abordagem para avaliação e desenvolvimento de modelo de carga móvel. Embora o principal objetivo desta tese seja averiguar o impacto de caminhões nas pontes, os dados apresentados aqui podem ser usados em qualquer aplicação de engenharia que dependa das características do tráfego de caminhão. Dados de duas estações WIM foram utilizados. Uma estação fica na Autoestrada Fernão Dias no Estado de São Paulo e possui 20 meses (Setembro de 2015 a Agosto de 2017) de dados coletados. A outra estação fica no estado do Rio Grande do Sul. Esta amostra tem 78 dias e foi coletada de Marco de 2014 a Junho de 2014. Com o objetivo de avaliar e desenvolver um novo modelo de carga móvel, uma abordagem para estimar o efeito de carga em termos de momento fletor e esforço cortante é proposta. Este método faz uso de estatísticas de caminhões em múltiplas presenças e isolados. Três casos de múltiplas presenças são considerados: \"Following\", \"Side-by-side\" e \"Staggered\". A abordagem proposta é comparada com o método usado pela AASHTO LRFD. A abordagem para estimar os \"bias factors\" mostra que considerar apenas caminhões totalmente correlacionados é muito conservador, principalmente para períodos curtos onde há uma falta de ocorrências, especialmente para eventos \"Following\". Por outro lado, não considerar a correlação de peso dos caminhões resulta em valores muito baixos de \"bias factors\". Por fim, um modelo de carga móvel mais racional foi desenvolvido com base nos dados WIM. Outro objetivo desta tese foi usar pontes brasileiras existentes para calibrar o modelo de carga móvel descrito na NBR7188:2013. Análises de confiabilidade foram realizadas em uma amostra de sessenta pontes brasileiras, sendo que destas 39 são protendidas e 21 armadas. Elas estão localizadas em cinco diferentes estados: Pernambuco, Ceará, Bahia, São Paulo e Minas Gerais. As probabilidades de falha foram estimadas em termos de momento fletor e cisalhamento para vigas internas e vigas caixão. Apenas o estado limite último foi considerado. Verificou-se que os índices de confiabilidade são maiores nas pontes protendidas quando comparadas às pontes armadas. Além disso, os índices de confiabilidade tendem a diminuir à medida que o comprimento do vão aumenta.

The Long Term Bridge Performance (LTBP) Program is a 20-year program initiated by the Federal Highway Administration to better understand the behavior of highway bridges as they deteriorate due to environmental variables and vehicle loads. Part of this program includes the periodic testing of selected bridges. The Lambert Road Bridge was subjected to nondestructive testing in the fall of 2009. Part of this testing included a live load test. This test involved driving two heavy trucks across the instrumented bridge on selected load paths. The bridge was instrumented with strain, displacement, and tilt sensors. This collected data was used to calibrate a finite element model. This finite element model was used to determine the theoretical live load distribution factors. Using the controlling distribution factor from the finite element model, the inventory and operating ratings of the bridge were determined. These load ratings were compared to those obtained from using the controlling distribution factor from the AASHTO LRFD Specifications. This thesis also examined how different parameters such as span length, girder spacing, parapets, skew, continuity, deck overhang, and deck thickness affect the distribution factors of box girder bridges. This was done by creating approximately 40 finite element models and comparing the results to those obtained by using the AASHTO LRFD Specifications.

As part of the Federal Highway Administration's Long-Term Bridge Performance Program, Live Load and Dynamic tests were conducted. A long-term monitoring plan was developed and presented for the Utah Pilot Bridge based on Live Load and Dynamic tests. As one of seven pilot bridges, the Utah Pilot Bridge is one of the first bridges used to initiate the LTBP Program. A formal permit approval process, with the Utah Department of Transportation, was followed to gain permission to conduct the tests and install long-term instrumentation. Analysis provided good results for each test completed, with a summary of test results presented. A Finite Element Model was created and refined based off test data. Instrumentation was installed and checked to ensure quality data was streaming to the collection site.

Structural analysis of highway bridges using complicated 3-D FEMs to determine live load effects in bridge components is possible due to the readily available computational tools in design offices. However, building such complicated 3-D FEMs is tedious and time consuming. Accordingly, most design engineers prefer using simplified 2-D structural models of the bridge and live load distribution equations (LLDEs) available in current bridge design codes to determine live load effects in bridge components. Basically, the live load effect obtained from a 2-D model is multiplied by a factor obtained from the LLDE to calculate the actual live load effect in a 3-D structure. The LLDE available in current bridge design codes for jointed bridges were also used for the design of straight and skewed integral bridges by bridge engineers. As a result, these bridges are either designed conservatively leading to additional construction cost or unconservatively leading to unsafe bridge designs. Recently, LLDEs for integral bridges (IBs) with no skew are developed. To use these equations for skewed integral bridges (SIBs) a correction factor is needed to multiply these equations to include the effect of skew. Consequently, in this research study, skew correction factors for SIBs are developed. For this purpose, finite element models of 231 different three dimensional and corresponding two dimensional structural models of SIBs are built and analyzed under live load. The analyses results reveal that the effect of skew on the distribution of live load moment and shear is significant. It is also observed that skew generally tends to decrease live load effects in girders and substructure components of SIBs. Using the analyses results, analytical equations are developed via nonlinear regression techniques to include skew effects in the LLDEs developed for straight IBs. The developed skew correction factors are compared with FEAs results. This comparison revealed that the developed skew correction factors yield a reasonably good estimate of the reduction in live load effects due to the effect of skew.