Spliced girder technology continues to attract attention due to its versatility over traditional prestressed concrete highway bridge construction. Relatively limited data is available in the literature, however, for large-scale tests of post-tensioned I-girders, and few studies have examined the behavior of the cast-in-place (CIP) splice regions of post-tensioned spliced girder bridges. In addition to limited knowledge on CIP splice region behavior, a wide variety of splice region details (e.g., splice region length, mild reinforcement details, cross-sectional geometry, etc.) continue to be used in the field. In response to these issues, the research program described in this dissertation was developed to (i) study the strength and serviceability behavior of the CIP splice regions of spliced I-girders, (ii) identify design and detailing practices that have been successfully implemented in CIP splice regions, and (iii) develop design recommendations based on the structural performance of spliced I-girder test specimens. To accomplish these tasks, an industry survey was first conducted to identify the best practices that have been implemented for the splice regions of existing bridges. Splice region details were then selected to be included in large-scale post-tensioned spliced I-girder test specimens. Two tests were conducted to study splice region behavior and evaluate the performance of the chosen details. The failure mechanisms of both test girders were characterized by a shear-compression failure of the web concrete with primary crushing occurring in the vicinity of the top post-tensioning duct. Most significantly, the girders acted essentially as monolithic members in shear at failure. Web crushing extended across much of the test span and was not localized within the splice regions. To supplement the spliced girder tests, a shear-friction experimental program was also conducted to gain a better understanding of the interface shear behavior between precast and CIP concrete surfaces at splice regions. The findings of the shear-friction study are summarized within this dissertation. Based on the results of the splice region research program, design recommendations were developed, including recommended CIP splice region details.

This thesis focuses on the forensic analysis of ten full-scale post-tensioned beam specimens after four years of aggressive exposure testing. The research was funded by FHWA and TxDOT. Post-tensioned structures have been under scrutiny due to their vulnerability to corrosion damage. Recent corrosion failures have been traced to inadequate materials and construction procedures. The purpose of this research project is to evaluate the corrosion performance of new and upcoming post-tensioning materials and systems and to determine their suitability for preventing durability issues which were found in older structures. The following variables were tested in the full-scale beam specimens: strand type, duct type, duct coupler type, anchorage type, tendon encapsulation. Non-destructive and destructive testing methods for evaluating corrosion damage were examined. Cost analysis of each material was conducted using tendon quantities from a typical post-tensioned bridge for comparison. Galvanized steel ducts performed poorly, showing substantial pitting and area loss. Plastic ducts were intact, but elevated grout chloride levels indicate that moisture was able to enter the ducts at the locations of couplers and grout vents. Strand corrosion was minor and uniform for all the types which were examined, suggesting that chloride traveled the length of the tendons through strand interstices. Stainless steel strands were nearly corrosion-free. Pourback quality was found to protect anchorages more than galvanization of bearing plates. The electrically isolated tendon did not completely prevent strand corrosion, but the system resulted in much lower chloride concentrations along the tendon than the conventional systems. / text

A harsh, cold, and icy environment is of no surprise to the conditions of a winter climate, where the wide use of de-icing salts on roads and highways allows for the initiation of chloride-induced corrosion of the reinforcement of concrete structures; a reduced service life, loss of structural integrity, visible damages, and ultimately structural failure are among the many unwanted effects of rebar corrosion. Chloride ingress into concrete has been extensively studied for the last four decades; however, most of the relevant research to date does not take into account the effects of sustained loading on chloride transport properties. Therefore, the objectives of this study were to investigate the influence of sustained compressive and tensile stresses on chloride ingress into concrete, and ultimately to understand what the effect of sustained stress is on chloride penetration depth, on chloride concentration by % weight of concrete, and on apparent diffusion coefficients by comparing results to those of unloaded control specimens. To achieve these objectives, six post-tensioned and four non-reinforced control concrete beams were constructed with different water-to-cement (w/c) ratios and completely submerged in a 4-5% de-icing salt (NaCl) solution for 12 weeks, allowing chloride transfer to be completely governed by continuous diffusion. The effects of supplementary cementing material on chloride ingress are also studied. Concrete beams were post-tensioned to induce variable sustained compressive and tensile stresses along the beam. After 12 weeks of exposure, beams were fractured at specific locations and sprayed with a 0.1N silver nitrate (AgNO3) solution to determine average penetration depths; chloride concentration profiles were obtained from potentiometric titration of grinded powder samples. Apparent chloride diffusion coefficients were then obtained from the results of spraying AgNO3 and titration, the latter by non-linear regression curve-fitting to Fick’s second law of diffusion. A good agreement between results from both methods reveals that the use of AgNO3 in field is acceptable in predicting the rate of chloride ingress in concrete sustaining stress. The chloride diffusivity for each profile, relative to that of the unstressed section, was related to the compressive and tensile stresses in the concrete section. The experimental results indicate the dependence of chloride ingress and concentration on the type and level of sustained stress. An analysis of the results to study the effects of the w/c ratio using colourimetric (silver nitrate spray) and potentiometric titration methods was also completed.

A protensão não-aderente caracteriza-se pela liberdade de deslocamento relativo entre o cabo de protensão e a fibra de concreto adjacente. A tensão na armadura de protensão no estado limite último é de difícil obtenção, não sendo dependente apenas das deformações em uma determinada seção transversal, mas sendo função de todas as deformações que ocorrem no concreto adjacente ao perfil de protensão. Para que seja obtida a tensão última, é necessária a integração das curvaturas ao longo de todo o elemento a fim de se obter o alongamento no cabo de protensão, o que se consegue com precisão apenas recorrendo-se a ferramentas numéricas, devido às não-linearidades físicas envolvidas no problema. O método construtivo com protensão não aderente vem sendo cada vez mais utilizado na execução de edifícios no Brasil. O principal sistema de protensão não aderente é o que utiliza a mono-cordoalha engraxada e plastificada, que alia os benefícios da protensão e a simplicidade necessária às obras moldadas no local. Apesar disso, não há no Brasil um volume de pesquisa sobre o comportamento dos elementos com protensão não aderente, compatível com a demanda da indústria da construção civil. Visando contribuir para o desenvolvimento das formulações nacionais de projeto dos elementos com protensão não aderente, o presente trabalho é a continuação de uma pesquisa que vem sendo realizada no Programa de Pós-Graduação em Engenharia Civil – PPGEC/UFRGS, a qual foi iniciada com a implementação de um modelo numérico capaz de analisar elementos com protensão não aderente e seguida de uma análise paramétrica sobre as principais variáveis que influenciam na tensão última na armadura de protensão. O trabalho que ora se apresenta traçou uma correlação entre os resultados não-aderentes obtidos da análise paramétrica com resultados aderentes, os quais são de mais fácil obtenção, pois se baseiam na compatibilidade de deformações na seção transversal. Foram feitas análises numéricas e analíticas com aderência dos mesmos protótipos estudados anteriormente sem aderência. Os resultados obtidos mostraram incrementos de tensão maiores no caso aderente, bem como maiores capacidades portantes. Estudou-se também uma metodologia capaz de computar a tensão última na armadura não aderente com análises do tipo compatibilidade de deformações, com a utilização de um coeficiente Lo/L redutor de aderência. Os resultados iniciais mostraram-se bons para carregamento nos terços, mas insatisfatórios para carregamentos distribuído e concentrado. Através de um ajuste no coeficiente Lo/L baseando-se nos dados da pesquisa precedente, bons resultados foram obtidos para todos os tipos de carregamento. A metodologia apresentada foi validada pela comparação com diferentes protótipos analisados numericamente, bem como protótipos ensaiados experimentalmente por diversos autores. / Unbonded post-tensioning is characterized for allowing relative displacement between the tendon and the concrete adjacent fiber. The ultimate stress in the unbonded tendon is difficult to be obtained, because it is not only dependent on the deformed shape of a cross section, but on the whole deformations occurring in the tendon profile adjacent concrete. To evaluate this ultimate stress, it is necessary to integrate all curvatures along the whole element, in order to obtain the total tendon elongation. This can only be precisely obtained using numerical tools, due to the non-linear factors involved in the problem. Unbonded post-tensioning is becoming ever more used in Brazilian building construction. The main unbonded post-tensioning system uses the unbonded mono-strand, that joins the benefits of prestressing with the necessary building simplicity. Nevertheless, there is no research effort in Brazil compatible with the construction industry demand. This study seeks to contribute to the development of the national formulations design of unbonded posttensioning elements. This work is a continuation of a research being undertaken at PPGEC/UFRGS. A numerical model able to determine the behavior of unbonded posttensioned elements was first developed, followed by a parametric study about the main parameters influencing the ultimate stress in unbonded tendons. The present work traced a correlation between the results for unbonded elements, obtained from the parametric analysis, with results for bonded elements. The latter are easily obtained, because they are based on the compatibility of strains in the cross section. Numerical and analytical calculations were performed for the same prototypes studied in the previous research, but now considering the existence of bond in the tendons. The results showed greater increments in stress for the bonded cases and also greater ultimate resistance. It was also devised a calculation method able to determine the ultimate stress in the unbonded tendon using an analysis similar to strain compatibility, but with a reduction bond coefficient Lo/L. The initial results obtained for a third-point loading showed a good agreement, but that not happened for the results of distributed and concentrated loads. However, by an adjustment of the Lo/L coefficient, based on the data of the previous research, good agreement was observed for all loading types. The presented methodology was validated by comparing results with other prototypes analyzed by the numerical model, and also results of experimental studies carried out by several authors.

A protensão não-aderente caracteriza-se pela liberdade de deslocamento relativo entre o cabo de protensão e a fibra de concreto adjacente. A tensão na armadura de protensão no estado limite último é de difícil obtenção, não sendo dependente apenas das deformações em uma determinada seção transversal, mas sendo função de todas as deformações que ocorrem no concreto adjacente ao perfil de protensão. Para que seja obtida a tensão última, é necessária a integração das curvaturas ao longo de todo o elemento a fim de se obter o alongamento no cabo de protensão, o que se consegue com precisão apenas recorrendo-se a ferramentas numéricas, devido às não-linearidades físicas envolvidas no problema. O método construtivo com protensão não aderente vem sendo cada vez mais utilizado na execução de edifícios no Brasil. O principal sistema de protensão não aderente é o que utiliza a mono-cordoalha engraxada e plastificada, que alia os benefícios da protensão e a simplicidade necessária às obras moldadas no local. Apesar disso, não há no Brasil um volume de pesquisa sobre o comportamento dos elementos com protensão não aderente, compatível com a demanda da indústria da construção civil. Visando contribuir para o desenvolvimento das formulações nacionais de projeto dos elementos com protensão não aderente, o presente trabalho é a continuação de uma pesquisa que vem sendo realizada no Programa de Pós-Graduação em Engenharia Civil – PPGEC/UFRGS, a qual foi iniciada com a implementação de um modelo numérico capaz de analisar elementos com protensão não aderente e seguida de uma análise paramétrica sobre as principais variáveis que influenciam na tensão última na armadura de protensão. O trabalho que ora se apresenta traçou uma correlação entre os resultados não-aderentes obtidos da análise paramétrica com resultados aderentes, os quais são de mais fácil obtenção, pois se baseiam na compatibilidade de deformações na seção transversal. Foram feitas análises numéricas e analíticas com aderência dos mesmos protótipos estudados anteriormente sem aderência. Os resultados obtidos mostraram incrementos de tensão maiores no caso aderente, bem como maiores capacidades portantes. Estudou-se também uma metodologia capaz de computar a tensão última na armadura não aderente com análises do tipo compatibilidade de deformações, com a utilização de um coeficiente Lo/L redutor de aderência. Os resultados iniciais mostraram-se bons para carregamento nos terços, mas insatisfatórios para carregamentos distribuído e concentrado. Através de um ajuste no coeficiente Lo/L baseando-se nos dados da pesquisa precedente, bons resultados foram obtidos para todos os tipos de carregamento. A metodologia apresentada foi validada pela comparação com diferentes protótipos analisados numericamente, bem como protótipos ensaiados experimentalmente por diversos autores. / Unbonded post-tensioning is characterized for allowing relative displacement between the tendon and the concrete adjacent fiber. The ultimate stress in the unbonded tendon is difficult to be obtained, because it is not only dependent on the deformed shape of a cross section, but on the whole deformations occurring in the tendon profile adjacent concrete. To evaluate this ultimate stress, it is necessary to integrate all curvatures along the whole element, in order to obtain the total tendon elongation. This can only be precisely obtained using numerical tools, due to the non-linear factors involved in the problem. Unbonded post-tensioning is becoming ever more used in Brazilian building construction. The main unbonded post-tensioning system uses the unbonded mono-strand, that joins the benefits of prestressing with the necessary building simplicity. Nevertheless, there is no research effort in Brazil compatible with the construction industry demand. This study seeks to contribute to the development of the national formulations design of unbonded posttensioning elements. This work is a continuation of a research being undertaken at PPGEC/UFRGS. A numerical model able to determine the behavior of unbonded posttensioned elements was first developed, followed by a parametric study about the main parameters influencing the ultimate stress in unbonded tendons. The present work traced a correlation between the results for unbonded elements, obtained from the parametric analysis, with results for bonded elements. The latter are easily obtained, because they are based on the compatibility of strains in the cross section. Numerical and analytical calculations were performed for the same prototypes studied in the previous research, but now considering the existence of bond in the tendons. The results showed greater increments in stress for the bonded cases and also greater ultimate resistance. It was also devised a calculation method able to determine the ultimate stress in the unbonded tendon using an analysis similar to strain compatibility, but with a reduction bond coefficient Lo/L. The initial results obtained for a third-point loading showed a good agreement, but that not happened for the results of distributed and concentrated loads. However, by an adjustment of the Lo/L coefficient, based on the data of the previous research, good agreement was observed for all loading types. The presented methodology was validated by comparing results with other prototypes analyzed by the numerical model, and also results of experimental studies carried out by several authors.

Doctor of Philosophy / Department of Civil Engineering / Robert J. Peterman / Possibly the most pressing need in highway construction today is the repair or replacement of existing bridges. Due to increased needs and growing traffic, in addition to aging and extensive use, more than 2000 bridges in Kansas alone need to be replaced during the next decade. The majority of these bridges has spans of 100 ft or less, and has relatively shallow profiles. It is becoming increasingly important to implement a standard method for replacement in which the process is expedited and accomplished in cost-effective manner. Requirements for design and construction of concrete bridges have drastically changed during recent years. A main change in design is live-load requirements. Nebraska inverted-T bridge system has gained increasing popularity for its lower weight compared to I-girder bridges. However, there are some limiting issues when using IT system in replacing existing CIP bridges. Implementation of a post-tensioned IT system, which is the focus of this research, is believed to be one excellent solution for the IT deficiencies. Post-tensioning is added by placing a draped, post-tensioning duct in the stems of the IT members. Post-tensioning will lead to a higher span-to-depth ratio than IT system, and will reduce the potential transverse cracks in the (CIP) deck. Finally, the undesired cambers of pretensioned beams will be reduced, because fewer initial prestressing will be needed. This study was intended to explore the behavior of the PT-IT system, identify major parameters that control and limit the design of this system, and investigate different construction scenarios. This was achieved by conducting an extensive parametric study. For that purpose, PT-IT analysis program was developed and written using C++ programming language. The program was used to analyze various post-tensioning procedures for the post-tensioned inverted-T system. A Visual Basic friendly interface was provided to simplify the data input process. The findings of this research included recommendation of construction scenario for PT-IT system, as well as examining different methods for estimating time-dependent restraining moments. Effect of different concrete strengths on the behavior of PT-IT system was also determined. Most importantly, the effect of timing on different construction stages was also evaluated and determined.

A harsh, cold, and icy environment is of no surprise to the conditions of a winter climate, where the wide use of de-icing salts on roads and highways allows for the initiation of chloride-induced corrosion of the reinforcement of concrete structures; a reduced service life, loss of structural integrity, visible damages, and ultimately structural failure are among the many unwanted effects of rebar corrosion. Chloride ingress into concrete has been extensively studied for the last four decades; however, most of the relevant research to date does not take into account the effects of sustained loading on chloride transport properties. Therefore, the objectives of this study were to investigate the influence of sustained compressive and tensile stresses on chloride ingress into concrete, and ultimately to understand what the effect of sustained stress is on chloride penetration depth, on chloride concentration by % weight of concrete, and on apparent diffusion coefficients by comparing results to those of unloaded control specimens. To achieve these objectives, six post-tensioned and four non-reinforced control concrete beams were constructed with different water-to-cement (w/c) ratios and completely submerged in a 4-5% de-icing salt (NaCl) solution for 12 weeks, allowing chloride transfer to be completely governed by continuous diffusion. The effects of supplementary cementing material on chloride ingress are also studied. Concrete beams were post-tensioned to induce variable sustained compressive and tensile stresses along the beam. After 12 weeks of exposure, beams were fractured at specific locations and sprayed with a 0.1N silver nitrate (AgNO3) solution to determine average penetration depths; chloride concentration profiles were obtained from potentiometric titration of grinded powder samples. Apparent chloride diffusion coefficients were then obtained from the results of spraying AgNO3 and titration, the latter by non-linear regression curve-fitting to Fick’s second law of diffusion. A good agreement between results from both methods reveals that the use of AgNO3 in field is acceptable in predicting the rate of chloride ingress in concrete sustaining stress. The chloride diffusivity for each profile, relative to that of the unstressed section, was related to the compressive and tensile stresses in the concrete section. The experimental results indicate the dependence of chloride ingress and concentration on the type and level of sustained stress. An analysis of the results to study the effects of the w/c ratio using colourimetric (silver nitrate spray) and potentiometric titration methods was also completed.

There are a great number of old structures around the world, some of which were designed for completely different purposes than in their current application. Swedish railway bridges were for example only designed for maximum axle loads of 200 kN in the beginning of the 20th century, while the highest axle loads of today are twice as high. The traffic intensities have also increased dramatically and the velocities are now higher than ever before. Reinforced concrete trough bridges were typically designed and built in the mid-20th century and it is still one of the most frequent railway bridge types in Sweden. The trough bridges were normally designed for traffic loads which were smaller than the loads today and in order to maintain an old structure as the loads increases, structural upgrading of the load bearing capacity might be necessary. Upgrading the load carrying capacity can be performed in two ways, namely administrative upgrading or strengthening. Administrative upgrading refers to refined design calculations, using real material data, geometry and loads, which provides a higher capacity than the original design and the bridge can thereby be upgrading with minor physical impact. Upgrading by strengthening on the other hand, refers to, often, larger physical alteration of the structure in order to enhance the original load carrying capacity.Upgrading methods for increased flexural resistance of concrete trough bridges has been developed and tested previously, but strengthening methods for increased shear resistance in the bridge deck are still absent. The objective of this thesis is therefore to find an existing- or develop a new strengthening method which can be applied in order to enhance the shear resistance of concrete trough bridge decks. The difficulties associated to strengthening of existing railway bridges include traffic during the strengthening work and concrete surfaces concealed by the ballast.The State-of-the-Art indicated that none of the existing strengthening techniques were sufficient for this application and internal unbonded post-tensioning in the transverse direction was nominated as the most promising method. The research was thereafter focused on testing the possibilities and strengthening effects of post-tensioning. Two laboratory investigations were performed during the research project and the method was finally tested in a field test on a 50 years old trough bridge in Haparanda, Sweden. The strengthening procedure of internal unbonded post-tensioning consists of four consecutive steps:1.Transverse drilling of the horizontal holes through the bottom slab.2.Installation of the prestressing system.3.Post-tensioning of the system.4.Sealing of the prestressing system.The laboratory and field tests were successful and the results proved that the internal steel reinforcement within the concrete was compressed when the trough bridge was post-tensioned. Due to the compression, a higher load could be carried by the bridge deck before the tensile reinforcement yields and the bridge fails. In other words, the flexural capacity of the bridge deck was increased. The field test actually showed that eight steel bars, post-tensioned with 430 kN per bar on the Haparanda Bridge, completely counteracted the tensile stresses caused by a train with 215 kN axle loads. The effect on the shear resistance was however not as easy to measure, but the laboratory test recorded a significant strain reduction in the tensile reinforcement which was bent up at the transition zone between the bridge deck and the main girders. The reduced strain might be interpreted as lower shear stresses and post-tensioning can thereby be considered to have a positive effect on the shear resistance of the bridge deck. Shear design according to the protocol of Eurocode 2 or BBK was however found to be restrictive in predicting the post-tensionings effect on the shear capacity and further research is proposed in chapter 8. / Det finns ett stort antal gamla konstruktioner runtom i världen och många byggdes för helt andra användningsområden än vad de numera används till. Som ett exempel kan nämnas att svenska järnvägsbroar i början av 1900-talet byggdes för att klara av att bära axellaster på maximalt 200 kN, medan några av våra nybyggda broar är konstruerade för dubbelt så stora axellaster. Även traffikmängden har mångdubblats och tåghastigheterna är nu högre än någonsin. Trågbroar i armerad betong är en typisk bro som byggdes i Sverige framförallt på 50-talet och den är fortfarande en av de vanligaste brotyperna i Sverige. Trågbroarna konstruerades normalt för att bära lägre laster än vad vi har idag och för att kunna ha kvar dessa broar när lasterna ökar kan det krävas någon form av uppgradering av bärförmågan. Det finns två sätt att förbättra bärförmågan på en gammal bro, nämligen administrativ uppgradering eller förstärkning. Administrativ uppgradering innebär att nya förbättrade beräkningsmetoder används tillsammans med verkliga materialhållfastheter, geometrier och laster för att mer noggrant räkna ut brons bärförmåga. Normalt visar det sig att bärförmågan är högre än vad de ursprungliga beräkningarna antydde. På så vis höjs kapaciteten med minimal fysisk åverkan på bron. Uppgradering genom förstärkning innebär däremot att konstruktionens bärförmåga höjs genom att förändra bron ur ett rent fysiskt perspektiv. Metoder för att öka böjkapaciteten på trågbroar i betong har utvecklats och testats tidigare, men förstärkningsmetoder för att höja tvärkraftskapaciteten saknas däremot fortfarande. Målet för denna avhandling ligger därför i att utveckla en förstärkningsmetod som kan användas för att förbättra tvärkraftskapaciteten för bottenplattan på trågbroar i betong. Det finns dock några svårigheter sammankopplade med förstärkning av befintliga järnvägsbroar, t.ex. tågtraffik under förstärkningsförfarandet och att viktiga betongytor är skyddade av ballast.Inga befintliga förstärkningsmetoder bedömdes däremot som lämpliga för det avsedda användningsområdet vid ”State-of-the-Art’’ studien. Invändig efterspänning av broplattan i tvärledd bedömdes som den bäst lämpade förstärkningsmetoden och efterföljande forskning fokuserades på att reda ut möjligheter för och förstärkningseffekter av efterspänning. Två olika laboratorieförsök genomfördes under forskningsprojektet och förstärkningsmetoden testades slutligen vid ett fältförsök på en 50 år gammal järnvägsbro i Haparanda.Själva tillvägagångssättet för förstärkningsmetoden består av fyra viktigaoch sammanhängande arbetssteg:1. Borrning av horisontella hål tvärs igenom trågbrons bottenplatta.2. Installation av själva försstärkningssystemet.3. Efterspänning av förstärkningssystemet.4. Förslutning av förstärkningssystemet.Både laboratorie och fältförsöken blev lyckade och resultaten visade att stålarmeringen inuti betongen trycktes ihop när trågbron efterspänndes. Tack vare denna kompression så kan broplattan bära högre laster innan dragarmeringen börjar flyta och bron slutligen går sönder. Med andra ord så höjdes brons böjkapacitet. Fältförsöket visade att de åtta spännstagen, efterspännda med 430 kN per stag, helt och hållet motverkade dragarmeringens påkänningar av ett tåg med axellasten 215 kN. Förstärkningsmetodens effekt på tvärkraftskapaciteten är däremot inte lika lätt att påvisa men laboratorieförsöken visade att töjningen reducerades betydligt i den uppbockade dragarmeringen, i zonen där plattan fäster i huvudbalkarna. De lägre töjningsnivåerna kan tolkas som lägre skjuvpåkänningar och efterspänningen kan därmed ha en positiv effekt på broplattans tvärkraftskapacitet. Laboratorieförsöken visade däremot att både Eurokod 2 och BBK är restriktiva när det gäller att uppskatta efterspänningens effekt på tvärkraftskapaciteten. En ny förstärkningsmetod för trågbroar i betong har därmed föreslagits i och med denna avhandling, men en del frågetecken kvarstår och i kapitel 8 ges därför förslag på fortsatta forskningsområden.

No description available.

Full-depth precast concrete panels offer an efficient alternative to traditional cast-in-place concrete for replacement or new construction of bridge decks. Research has shown that longitudinal post-tensioning helps keep the precast bridge deck in compression and avoid problems such as leaking, cracking, spalling, and subsequent rusting on the beams at the transverse panel joints. Current design recommendations suggest levels of initial compression for precast concrete decks in a very limited number of bridge configurations. The time-dependent effects of creep and shrinkage in concrete and relaxation of prestressing steel complicate bridge behavior, making the existing recommendations for post-tensioning in precast deck panels invalid for all bridges with differing girder types, sizes, spacings, and span lengths. Therefore, the development of guidelines for levels of post-tensioning applicable to a variety of bridge types is necessary so designers may easily implement precast concrete panels in bridge deck construction or rehabilitation. To fulfill the needs described, the primary objective of this research was to determine the initial level of post-tensioning required in various precast concrete bridge deck panel systems in order to maintain compression in the transverse panel joints until the end of each bridge's service life. These recommendations were determined by the results of parametric studies which investigated the behavior of bridges with precast concrete decks supported by both steel and prestressed concrete girders in single spans as well as two and three continuous spans. The three primary variables in each parametric study included girder type, girder spacing, and span length. The age-adjusted effective modulus method was used to account for the ongoing effects of creep and shrinkage in concrete. Results from the Mathcad models used in the parametric studies were confirmed through comparison with results obtained from finite element models generated in DIANA. Initial levels of post-tensioning for various bridge systems are proposed based on the trends observed in the parametric studies. The precast decks of the simple span bridges with steel girders and the one, two, and three span bridges with prestressed concrete girders needed only 200 psi of initial post-tensioning to remain in compression under permanent and time-dependent loads throughout each bridge's service life. The precast decks of the two and three span continuous bridges with steel girders, however, needed a significantly higher level of initial compression due to the negative moments created by live loads. / Master of Science