Дисертації з теми "Live loads Bridges"
Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Live loads Bridges.
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "Live loads Bridges".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Memory, Terry James. "On the dynamic behaviour of highway bridges : a thesis." Thesis, Queensland University of Technology, 1992. https://eprints.qut.edu.au/36245/1/36245_Memory_1992.pdf.
Повний текст джерелаАнотація:
Thomson (1910) first suggested that when designing a bridge the static stress should be increased to account for the dynamic nature of vehicle-bridge interaction. Since that time engineers have increased the static design loads on bridges by a factor usually referred to as the impact factor. Between 1925 and 1979 this impact factor was codified throughout the world as a function
of maximum span length. In 1979 the Ontario Highway Bridge Design Code (OHBDC) renamed the impact factor as the "Dynamic Load Allowance" (DLA) and specified it as a function of the first flexural frequency of bridge
superstructures. This code provision was subsequently adopted by the National Association of Australian State Road Authorities (NAASRA), now known as AUSTROADS. Neither the OHBDC nor the NAASRA bridge design
specification suggest analysis methods for evaluating the first flexural frequency of bridge superstructures. Consequently, this thesis investigates, in
detail, methods used to estimate the fundamental frequency of bridge superstructures and proposes a simple, accurate and quick method for simply
supported bridges. As the correlation between field results and theoretical estimates was considered paramount, the significance of transverse and
longitudinal support stiffness, dynamic modulus of elasticity and idealisation complexity were assessed. Subsequent to this, a relationship between support
stiffness and the shift in fundamental frequency, relative to the frictionless case, was developed.
A second major component of this thesis is the concept of Dynamic Load Allowance itself. To gain an appreciation of this phenomenon, full scale bridge testing was undertaken. Results obtained raised several questions
about the significance of higher modes of bridge excitation and about the ability of a DLA-first flexural frequency code provision to embody vehiclebridge
interaction. The results of the bridge testing led to the suggestion that the dynamic load allowance should be codified as a function of both the first flexural frequency and the length of a bridge.
2
Ransom, Angela L. "Assessment of bridges by proof load testing." Thesis, Queensland University of Technology, 2000. https://eprints.qut.edu.au/36104/1/36104_Ransom_2000.pdf.
Повний текст джерелаАнотація:
Throughout the world, many countries are faced with the problem of ageing bridge infrastructure that is being called upon to carry increasing loads. With the difficulties associated with gaining funding to replace or rehabilitate these bridges, asset managers must ensure that the most efficient use is made of the existing
infrastructure. It has been shown that theoretical assessment of bridges by analytical means often leads to conservative estimates of capacity. Many bridges therefore have been posted with load limits which do not accurately reflect the structural capacity of these
bridges. Various methods of assessing bridge capacity are adopted by. road authorities throughout the world. These forms of assessment include analytical rating, calibration of analytical models by supplementary load testing and assessment by proof load testing.
Proof load testing has consistently demonstrated that bridges often have reserves of
strengths in excess of that indicated by theoretical analysis. The aim of proof load
testing is to determine a realistic bridge load rating which accurately reflects the load capacity of the bridge. This thesis investigates the use of proof load testing in the assessment of bridges and its application to the Australian bridge infrastructure. The procedures used in proof load testing do not vary greatly between countries but the magnitude of the loads applied and the load factors used to calculate a load rating vary significantly. The procedures and practices adopted internationally were reviewed and adapted to suit Australian bridge infrastructure and conditions. The
methodology was evaluated through a series of pilot proof load tests and
subsequently potential improvements were identified.
One of the challenges associated with proof load testing is the determination of the proof load that should be applied. In this thesis, structural reliability methods have been used to determine the proof load required to achieve a desired level of safety after testing. These methods were extended to incorporate the expected residual life of the structure and to investigate the resulting effect on the proof load required.
Reliability theory has also been used to assess the risks involved, and the benefits gained by proof load testing. These risks and benefits are expressed in terms of a
decreased probability of failure or an increased safety index after a successful proof load test. The methods developed have been applied to the results of the proof load test conducted on the South Pine River Bridge.
3
程遠勝 and Yuansheng Cheng. "Vibration analysis of bridges under moving vehicles and trains." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B3124001X.
Повний текст джерела
4
Kabani, Matongo. "Reliability based live loads for structural assessment of bridges on heavy-haul railway lines." Doctoral thesis, Faculty of Engineering and the Built Environment, 2018. http://hdl.handle.net/11427/30126.
Повний текст джерелаАнотація:
The highest live loads on railway lines are on dedicated freight corridors operated as heavy-haul lines. These lines carry high axle loads above 25 tonnes and total tonnage above 20 million tonnes per annum over distances greater than 150km. The South African iron ore line currently operates long trains of length 4.1km with 30 tonne per axle wagons on a narrow gage (1065mm) line over a distance of 861km. The operation of heavy haul lines require close monitoring and structural performance evaluation of existing bridges. This study covered both analytical studies and field measurements of bridge dynamic response and static vertical loads required to compute moments shear for beam-type bridges. The field study of dynamic amplification factors was based on strain measurements on the Olifants bridge located on the heavy-haul iron line in South Africa. The Olifants bridge is a 23 span box girder consisting of 2 continuous span segments of 11 spans at either end and a drop span in the middle. The collected strain data consisted 1174 loaded and 1372 empty train crossing events from June 2016 to March 2017. The probabilistic study was based on weigh-in-motion data of heavy-haul freight collected from January 2016 to August 2016. The study was limited to single span, 2 span and 4 span bridges with equal spans and did not consider fatigue. The dynamic response parameters of interest were frequency time evolution of bridge under heavy loads and dynamic amplification factors. An approximate formula derived using 2 dimensional beam model with moving masses is presented. The approximate formulae predicts the reduced frequency within 12% of the estimate from field vibration measurements of an 11 span continuous bridge with train to bridge linear mass ratio of 88%. The approximate formula underestimates the frequency as the stiffening contribution from train suspension system is ignored in a moving mass approximation. Dynamic amplification factors from strain measurements of a continuous 11 span bridge where considerably higher with maximum of 12% compared to 5% from a moving force analytical model for train speed below 60km/h. The amplification from measurements were considerably higher due to the additional local amplification of strains in upper flange of the box girder. A comparison of amplification factors for loaded and empty trains shows that increase in gross weight increases amplification factors. Furthermore, dynamic amplification factors are not dependent on changes in speed during train crossing. Different extrapolation techniques were used to obtain load effects from the same block maxima data. It was shown that the normal, GEV and Bayesian extrapolation methods give load effects within 1% of each other with the normal extrapolation being marginally on the lower end. This observation holds across beam types and span lengths from 5m to 50m. Although the GEV allows for all the three extreme type distributions, an analysis based on available weigh-in-motion data of axle weights show that the fitted distributions using Bayesian and Maximum Likelihood Estimate for all load effects for the span ranges are all Weibull type. On the other hand it is known that the domain of attraction for the normal distribution is Gumbel type. The study also found that extrapolated loads effects are less sensitive to increase in return period beyond 50 years. This aspect is significant as return period is a measure of safety target when determining design values for loads. The study investigated the impact of traffic volume increase and wagon axle load dependencies. The load effects on heavy-haul were shown to be more sensitive to the weak dependence than to traffic growth over the remaining service life of 50 years. The increase in return levels of load effects is less than 1% for traffic volume growth of 4% over a period of 50 years in contrast to the much higher values between 6% and 9% reported on highway bridges for 3% traffic volume growth over 40 year period. Assessment loads that account for some wagon axle dependence have lower return values of load effects than the assume that axle loads are independent which is consistent with theory.
5
Erhan, Semih. "Effect Of Vehicular And Seismic Loads On The Performance Of Integral Bridges." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613739/index.pdf.
Повний текст джерелаАнотація:
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.
6
姜瑞娟 and Ruijuan Jiang. "Identification of dynamic load and vehicle parameters based on bridge dynamic responses." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31244270.
Повний текст джерела
7
Barthelot, Shyamalie Lorraine. "Development of a probability based load criterion for the NAASRA Bridge Design Specification in LSD format." Thesis, Queensland University of Technology, 1989. https://eprints.qut.edu.au/36456/1/36456_Barthelot_1989.pdf.
Повний текст джерелаАнотація:
The objective of this research is to develop a rational
approach to the safety analysis of highway bridge
superstructures. The developed models have been
demonstrated on examples of short and medium span,
prestressed concrete deck unit and girder bridges.
Probabilistic models for structural resistance and load
effects have been constructed using measured data. The
load components considered were dead load and traffic
live load. The ultimate resistance was assumed to be
lognormally distributed, while dead load was assumed to
be normally distributed. The Gumbel distribution was
selected to model traffic live load effects.
Safety was measured
Reliability indices
in terms of a reliability index.
were calculated for the ultimate
strength limit state for bridge superstructures.
Structural reliability is calculated using the advanced
methods, allowing consideration of actual distributions
of loads and resistance.
Safety was evaluated for prestressed concrete
designed to the existing NAASRA Bridge
Specification and also in accordance with the
Bridge Design Code in Limit States format. The
members
Design
draft
draft
code has achieved a more uniform level of reliability
for all structures.
8
Malan, Andreas Dawid. "Critical normal traffic loading for flexure of bridges according to TMH7." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80013.
Повний текст джерелаАнотація:
Thesis (MScEng)--Stellenbosch University, 2013.ENGLISH ABSTRACT: Different types of live loading due to traffic may act on bridges. The focus of this study is on normal traffic loading according to the South African specification of TMH7. Heavy vehicles are not included in normal traffic loading. TMH7 represents the code of practice for the design of highway bridges and culverts in South Africa. The aim of the study is to provide an insight into the flexural analysis of skew bridges, under the effects of normal traffic loading. The need for the study arose since the specification of TMH7 does not explicitly specify application patterns for normal traffic loading. Only the intensity of normal traffic loading is specified and it should be applied to yield the most adverse effects. For these reasons, a set of so-called standard application patterns are investigated and developed through the course of this study. The envelope of the values from the standard application patterns are compared to the most adverse application pattern for flexural effects in certain design regions of the bridge deck. Flexure, as in the context of this study, translates into the bending and twisting of the bridge deck under loads. A number of numerical experiments are performed for typical single span and multi-span continuous carriageways, where the standard application patterns are compared to the most adverse application patterns. The results from the numerical experiments are documented and compared as the angle of skew of the bridge deck increases in plan-view. For this purpose, the development of effective and specialized software was necessary. It was found that the set of standard application patterns can be used as a preliminary approximation for the most adverse effects of normal traffic loading, for specific flexural resultants in certain design regions of a bridge deck. However, for a large number of secondary flexural effects, the set of standard application patterns did not represent a good approximation for the most adverse values.
AFRIKAANSE OPSOMMING: Verskillende tipes lewendige belasting, as gevolg van verkeer, kan op brûe inwerk. Die fokus van die studie is op normale verkeers-belasting volgens die Suid-Afrikaanse spesifikasie van TMH7. Swaar-voertuie word nie ingesluit by normale verkeers-belasting nie. TMH7 verteenwoordig die kode vir die ontwerp van padbrûe en duikers in Suid-Afrika. Die doel van die studie is om insig te verskaf in die buig-analise van skewe brûe, as gevolg van die werking van normale verkeers-belasting. Die rede vir hierdie studie ontstaan aangesien die spesifikasie van TMH7 nie eksplisiet aanwendingspatrone vir normale verkeers-belasting voorskryf nie. Slegs die intensiteit van normale verkeersbelasting word voorgeskryf en dit moet aangewend word om die negatiefste effekte te verkry. Vir hierdie redes word 'n versameling van sogenaamde standaard aanwendings-patrone deur die loop van die studie ondersoek en ontwikkel. Die omhullings-kurwe van die waardes wat deur die standaard patrone gelewer word, word vergelyk met die waarde van die aanwendings-patroon wat die negatiefste buig-effek in sekere ontwerp-areas van die brugdek veroorsaak. Buig-effekte, soos van toepassing op hierdie studie, verwys na buig en wring van die brugdek as gevolg van belastings. 'n Aantal numeriese eksperimente, vir enkel-span sowel as multi-span deurlopende brugdekke, word uitgevoer en die standaard aanwendings-patrone word vergelyk met die aanwendings-patrone wat die negatiefste waardes lewer. Die resultate van die numeriese eksperimente word gedokumenteer en vergelyk soos die hoek van skeefheid van die brugdek in plan-aansig toeneem. Vir hierdie doel is die ontwikkeling van effektiewe en gespesialiseerde sagteware dus nodig. Daar is gevind dat die standaard aanwendings-patrone, vir spesifieke buig-resultante in sekere ontwerp-areas van die brugdek, as 'n voorlopige benadering vir die negatiefste effekte van normale verkeers-belasting gebruik kan word. Dit was egter verder gevind dat vir 'n groot aantal sekondêre buig-effkte, die versameling standaard aanwendings-patrone nie as 'n goeie benadering vir die negatiefste waardes dien nie.
9
Issa, Camille Amine. "Nonlinear earthquake analysis of wall pier bridges." Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/54297.
Повний текст джерелаАнотація:
Accurately predicting the response of complex bridge structures to strong earthquake ground motion requires the use of sophisticated nonlinear dynamic analysis computer programs not generally available to the bridge design engineer. The analytical tools that have been developed are generally applicable to bridges whose substructures can be idealized as beam-columns. Bridges with wall piers do not belong to this category
The major objective of this study is to develop an analysis tool capable of simulating the effects of earthquakes on monolithic concrete wall pier bridges. Thus, after surveying the literature, a mathematical model is developed for the geometrically nonlinear earthquake analysis of wall pier bridges. Mixed plate elements are used to model the wall pier. The plate element has eight nodes and the degrees of freedom per node are three displacements and three moments. Beam elements are used to model the bridge deck. The beam element accounts for shear deformation and it has two nodes with three displacements and three rotations as degrees of freedom per node. A transitional element is used to join the beam elements to the plate elements. The equation of dynamic equilibrium is solved using the Newmark method with modified Newton-Raphson type iteration at each time step.
The mixed plate element is used to model two plate structures and the results are compared with analytical and other finite element solutions. A two span wall pier bridge is modeled using the structural elements developed in this study. The digitized time history for the N-S component of the El Centro Earthquake of May 18, 1940, is used to seismically excite the bridge model.Ph. D.
10
Senthilvasan, Jeevanandam. "Dynamic response of curved box girder bridges." Thesis, Queensland University of Technology, 1997.
Знайти повний текст джерела
11
Spittka, Berndt F. (Berndt Friedrich) 1980. "Analysis of headless shear stud connections." Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74404.
Повний текст джерелаАнотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 115-117)
Highway bridges are exposed to numerous elemental and loading issues that are extremely difficult for a designer to anticipate and account for during design. The current state of practice is to design a bridge deck for a certain life span and then turn the bridge over to maintenance personnel who attempt to prolong the life of the deck through a variety of repair and rehabilitation measures. These repair measures are rarely, if ever, considered during the design process of the bridge deck. Numerous researchers have looked at making bridges, specifically decks, more repairable. The majority of these research efforts have focused on the bridge deck system as a whole. Other researchers have looked at individual elements of the bridge deck to girder connection to see if the required strength could be achieved while making the connections easier to take apart. One of the main components in the bridge deck to girder system is the steel shear stud connection, which is used to create composite action between the deck and the girder. Numerous researchers have studied this connection from a strength perspective, and the strength equations for the shear connection have been codified. Shear connections using headless studs have been researched as well, but always as a part of a larger deck to girder connection system. The headless stud has never been researched to see how it responds to a shear loading. This study looks at headless studs with varying levels of debonding along the stud shaft to analyze the impact on the load resistance that the levels of debonding would have. Granular materials for the shear transfer of load are also looked at. The results show that, as expected, the headless, debonded shear studs can carry less load than a bonded stud, but the difference in load carrying capacity is within the suggested over-estimation range of the codes that other researchers have suggested. These results suggest that the use of headless, debonded shear studs in a deck to girder connection is a feasible way to make that connection more repairable.
Funded by the U.S. Dept. of the Army.
by Berndt F. Spittka
S.M.
12
Karagania, Richard M. "Road roughness and infrastructure damage." Thesis, Queensland University of Technology, 1997. https://eprints.qut.edu.au/36011/1/36011_Karagania_1997.pdf.
Повний текст джерелаАнотація:
Scientific research has identified road roughness as a significant factor that
contributes to increased vehicle dynamic wheel loads and therefore damage to
pavements and bridges. The other factors include vehicle speed and vehicle
suspension type. More specifically and regarding road roughness, research has
shown that damaging effects are caused by certain wavelengths and features in road
profiles and not the overall road roughness. Various methods of classifying road
roughness based on the ride quality are available. These methods, though important,
are limited in identifying the location of features along road profiles that cause
exceptionally high dynamic wheel loads hence damage. It is the development of a
methodology for identifying the location of these abnormally high dynamic wheel
forces that this thesis addresses.
A vehicle-road interaction model was developed for this research. This computer
model uses a quarter vehicle model and recorded road profile elevation data to
simulate the response of half a vehicle axle (quarter vehicle) driving along a road. 47
road profiles over 17 bridges were measured to run the model.
Signal processing techniques developed by electrical and mechanical engineers have
been used as an additional tool to road profile analysis. These techniques are very
powerful and their application to road profile investigations is significant. Using
computer simulation and by combining ride and damage criteria analysis, a
methodology of identifying segments of road that induce high dynamic wheel forces
and the location of abnormally high dynamic wheel forces has been established.
13
Aagard, Adam D. "Rectification of 2-D to 3-D Finite Element Analysis in Buried Concrete Arches Under Discrete Loading." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1768.pdf.
Повний текст джерела
14
Hevener, Wesley D. "Simplified live-load moment distribution factors for simple span slab on I-girder bridges." Morgantown, W. Va. : [West Virginia University Libraries], 2003. http://etd.wvu.edu/templates/showETD.cfm?recnum=3103.
Повний текст джерелаАнотація:
Thesis (M.S.)--West Virginia University, 2003.Title from document title page. Document formatted into pages; contains x, 141 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 137-141).
15
Wu, Haiyong. "Influence of live-load deflections on superstructure performance of slab on steel stringer bridges." Morgantown, W. Va. : [West Virginia University Libraries], 2003. http://etd.wvu.edu/templates/showETD.cfm?recnum=3117.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--West Virginia University, 2003.Title from document title page. Document formatted into pages; contains xx, 332 p. : ill. (some col.), map. Includes abstract. Includes bibliographical references (p. 256-264).
16
May, Jeremy James. "Live load distribution factors for glued-laminated timber bridges." [Ames, Iowa : Iowa State University], 2008.
Знайти повний текст джерела
17
Williams, Mark Erik. "Using neural networks to position live loads on bridge piers." [Florida] : State University System of Florida, 2000. http://etd.fcla.edu/etd/uf/2000/amt2436/MW%5FDissert.pdf.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--University of Florida, 2000.Title from first page of PDF file. Document formatted into pages; contains xv, 187 p.; also contains graphics. Vita. Includes bibliographical references (p. 182-186).
18
Menkulasi, Fatmir. "Development of a Composite Concrete Bridge System for Short-to-Medium-Span Bridges." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/50413.
Повний текст джерелаАнотація:
The inverted T-beam bridge system provides an accelerated bridge construction alternative for short-to-medium-span bridges. The system consists of adjacent precast inverted T-beams finished with a cast-in-place concrete topping. The system offers enhanced performance against reflective cracking, and reduces the likelihood of cracking due to time dependent effects. The effects of transverse bending due to concentrated wheel loads are investigated with respect to reflective cracking. Transverse bending moment are quantified and compared to transverse moment capacities provided by a combination of various cross-sectional shapes and transverse connections. A design methodology for transverse bending is suggested. Tensile stresses created due to time dependent and temperature effects are quantified at the cross-sectional and structure level and strategies for how to alleviate these tensile stresses are proposed. Because differential shrinkage is believed to be one of the causes of deck cracking in composite bridges, a study on shrinkage and creep properties of seven deck mixes is presented with the goal of identifying a mix whose long terms properties reduce the likelihood of deck cracking. The effects of differential shrinkage at a cross-sectional level are numerically demonstrated for a variety of composite bridge systems and the resistance of the inverted T-beam system against time dependent effects is highlighted. End stresses in the end zones of such a uniquely shaped precast element are investigated analytically in the vertical and horizontal planes. Existing design methods are evaluated and strut-and-tie models, calibrated to match the results of 3-D finite element analyses, are proposed as alternatives to existing methods to aid designers in sizing reinforcing in the end zones. Composite action between the precast beam and the cast-in-place topping is examined via a full scale test and the necessity of extended stirrups is explored. It is concluded that because of the large contact surface between the precast and cast-in-place elements, cohesion alone appears to provide the necessary horizontal shear strength to ensure full composite action. Live load distribution factors are quantified analytically and by performing four live loads tests. It is concluded that AASHTO's method for cast-in-place slab span bridges can be conservatively used in design.Ph. D.
19
Smolenski, Peter James. "Field instrumentation and live load testing to evaluate behaviors of three reinforced concrete bridge decks." Thesis, Montana State University, 2004. http://etd.lib.montana.edu/etd/2004/smolenski/SmolenskiP0805.pdf.
Повний текст джерела
20
Thornton, Nathan Paul. "Live Load Testing of Appalachia, Va Concrete Arch Bridges for Load Rating Recommendation." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/35195.
Повний текст джерелаАнотація:
As Americaâ s infrastructure ages, many of the nationâ s bridges approach the end of their service life. In order to develop a method for handling the rising number of deficient and functionally obsolete bridges, nondestructive tests and evaluations must be undertaken. Valuable information from these tests regarding the strength and condition of bridges will help in making decisions about their rehabilitation and replacement. Two adjoining open spandrel reinforced concrete arch bridges in downtown Appalachia, Virginia were selected for live load testing by Virginia Department of Transportation (VDOT). Both bridges have supported an increasing amount of extreme coal truck traffic throughout their service life and are essential to the efficient transport of coal in the region. Because of their age, having been built in 1929, and the amount of visible damage and repairs, VDOT was concerned about their remaining capacity and safe operation.
The live load tests focused on global behavior characteristics such as service strain and deflection as well as local behavior of the arches surrounding significant repairs. It was found that the strain and deflection data collected during load testing displayed linear elastic behavior, indicating excess capacity beyond the test loads. Also, given the loading applied, the measured strains and deflections were small in magnitude, showing that the bridges are still acting as stiff structures and are in good condition.
Data collected during these tests was compared to results from a finite element model of the bridges to determine the coal truck size which is represented by the live load test loading configurations. The model comparisons determined the test loads produced comparable deflections to those produced by the target coal truck load. Through this approach, a recommendation was given to VDOT regarding the satisfactory condition of the aging bridges to aid in the process of load rating and maintenance scheduling for the two bridges.
Master of Science
21
Erol, Mehmet Ali. "Effect Of Skew On Live Load Distribution In Integral Bridges." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611344/index.pdf.
Повний текст джерелаАнотація:
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.
22
Suthar, Kunal. "Effect of dead, live and blast loads on a suspension bridge." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7181.
Повний текст джерелаАнотація:
Thesis (M.S.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept. of Civil and Environmental Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
23
Xiao, Yilin. "Analyses of reinforced concrete cantilever bridge decks under the live truck loads." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ31659.pdf.
Повний текст джерела
24
Ferreira, Luciano Maldonado. "Aplicação da teoria da confiabilidade na obtenção de limites para o peso de veículos de carga em pontes de concreto." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-27072006-110602/.
Повний текст джерелаАнотація:
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 projetoThe 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
25
Walcker, Andrew Jon, and Andrew Jon Walcker. "Model-based Hybrid Framework for Live Load Carrying Performance Monitoring of Bridges." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/626386.
Повний текст джерелаАнотація:
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.
26
Parker, Walter P. "Proposed New Military Live Load for Highway Bridges in the United States." ScholarWorks@UNO, 2019. https://scholarworks.uno.edu/td/2631.
Повний текст джерелаАнотація:
This thesis presents the results of a mathematical analysis of various live load combinations on highway bridge spans up to 304.8 meters (1,000 feet) total lengths. The analysis included continuous beams, but only the results for simple beams is presented. The analysis was performed using an independently developed Microsoft EXCEL spreadsheet computation, based on superposition and classical mechanics.
In this thesis, several actual bridge live loadings and several hypothetical live loadings were analyzed and compared to the American Association of State Highway and Transportation Officials Load and Resistance Factor Design method. Also considered was the new bridge design method adopted by the Louisiana Department of Transportation in March 2015. The evolution of bridge design loads is discussed, and the concept of the Military Load Classification is introduced and adapted to the bridge design analysis. The results of the analysis are presented, compared and interpreted for use in future bridge design.
27
Lin, Min. "Verification of AASHTO-LRFD specifications live load distribution factor formulas for HPS bridges /." Cincinnati, Ohio University of Cincinnati, 2004. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1108697828.
Повний текст джерела
28
Lin, Min. "Verification of AASHTO-LRFD Specifications Live Load Distribution Factor Formulas for HPS Bridges." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1108697828.
Повний текст джерела
29
Reilly, James Joseph. "Load Testing Deteriorated Spans of the Hampton Roads Bridge-Tunnel for Load Rating Recommendations." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/74302.
Повний текст джерелаАнотація:
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
30
Jefferson, Thomas Seth. "Computation of Live Load Deflections for a Composite, Steel-Girder Bridge." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/2027.
Повний текст джерелаАнотація:
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.
31
Hodson, Dereck J. "Live Load Test and Finite Element Analysis of a Box Girder Bridge for the Long Term Bridge Performance Program." DigitalCommons@USU, 2011. https://digitalcommons.usu.edu/etd/835.
Повний текст джерелаАнотація:
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.
32
Zhang, Qinghe. "Development of skew correction factors for live load shear and reaction distribution in highway bridge design a dissertation presented to the faculty of the Graduate School, Tennessee Technological University /." Click to access online, 2009. http://proquest.umi.com/pqdweb?index=0&did=1707210441&SrchMode=1&sid=2&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1268938179&clientId=28564.
Повний текст джерела
33
Arginhan, Oktay. "Reliability Based Safety Level Evaluation Of Turkish Type Precast Prestressed Concrete Bridge Girders Designed In Accordance With The Load And Resistance Factor Desing Method." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612723/index.pdf.
Повний текст джерелаАнотація:
The main aim of the present study is to evaluate the safety level of Turkish type precast prestressed concrete bridge girders designed according to American Association of State Highway and Transportation Officials Load and Resistance Factor Design (AASHTO LRFD) based on reliability theory. Span lengths varying from 25 m to 40 m are considered. Two types of design truck loading models are taken into account: H30S24-current design live load of Turkey and HL93-design live load model of AASHTO LRFD. The statistical parameters of both load and resistance components are estimated from local data and published data in the literature. The bias factors and coefficient of variation of live load are estimated by extrapolation of cumulative distribution functions of maximum span moments of truck survey data (Axle Weight Studies) that is gathered from the Division of Transportation and Cost Studies of the General Directorate of Highways of Turkey. The uncertainties associated with C40 class concrete and prestressing strands are evaluated by the test data of local manufacturers. The girders are designed according to the requirements of both Service III and Strength I limit states. The required number of strands is calculated and compared.
Increasing research in the field of bridge evaluation based on structural reliability justifies the consideration of reliability index as the primary measure of safety of bridges. The reliability indexes are calculated by different methods for both Strength I and Service III limit states. The reliability level of typical girders of Turkey is compared with those of others countries. Different load and resistance factors are intended to achieve the selected target reliability levels. For the studied cases, a set of load factors corresponding to different levels of reliability index is suggested for the two models of truck design loads. Analysis with Turkish type truck models results in higher reliability index compared to the USA type truck model for the investigated span lengths
34
Paulse, Sheryl Dawn. "Analysis and comparison of the South African and Eurocode live load models for railway bridges." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29698.
Повний текст джерелаАнотація:
This dissertation is an analytical study that compares the South African Transport Services (SATS) and Eurocode (EC) live load models for railway bridges. The study is specifically concerned with the critical load effects of shear and bending moment. The load models are simulated as moving loads over the full length of simply supported and continuous railway systems with speeds not exceeding 180km/h. The study is limited to short to medium spans ranging from 5m – 40m analysed in increments of 5m. The position of the maximum load effects for simply supported systems was determined using the frame analysis module in Prokon. Maximum load effects were determined using the influence line method. Maximum load effects for the continuous systems were determined using the moving load option in STRAP. It was found that SATS live load models imposed on single span railway bridges, produce conservative load effects for short span bridges but become over conservative with an increase in span, when compared with characteristic values of the EC load model 71 (LM71). For heavy loads (α = 1,10) in LM71, there is a good comparison with that of the EC for static and design moment (for a track with standard maintenance) with values of 5% lower at 10m but become moderately conservative (2% - 5%) with an increase in span. In the case of design bending moment (for a carefully maintained track) the SATS code is moderately conservative (6% - 8%) over the full range of spans for a carefully maintained track. For heavy loads (α = 1,10) in LM71, there is a good comparison with that of the Eurocode for static and design shear (for a carefully maintained track) with values of 4% lower at 10m but becoming moderately conservative (1% - 5%) with an increase in span. In the case of design shear (for a track with standard maintenance) the SATS code compares well with that of the EC, with values of 5% lower at 10m but becoming moderately conservative (4% - 13%) with an increase in span. Live traffic loads imposed on equal span (limited to 2) continuous railway bridges, produce conservative static and design shear load effects (for a carefully maintained track) in the mid-range of spans but become moderately conservative with increase in span for heavy loads (α = 1,10) for load model SW/0. There is a good comparison with that of the EC for design shear force (for a carefully maintained track) with moderately conservative (1% - 9%) for short span and long span systems for heavy loads (α = 1,10) for load model SW/0. A similar comparison occurs for heavy loads (α = 1,21) for SW/0 for static and design shear for a carefully maintained track. Live traffic loads imposed on equal span (limited to 2) continuous railway bridges produce over conservative static bending moment load effects for short span and long span bridges (2 x 30m – 2 x 40m) for characteristic values and heavy loads (α = 1,10 and α = 1,21) for load model SW/0. Generally, there is not a good comparison with that of the EC for static and design bending moment, for two span continuous railway bridges. Live traffic loads imposed on equal span (limited to 3) continuous railway bridges produce moderately conservative static shear force effects for heavy loads (α = 1,10 and α = 1,21) for load model SW/0. The only significant value is at the 3 x 5m span (21% higher) and the 3 x 15 – 3 x 20m range of spans (9% - 10% lower) for heavy loads (α = 1,10) and (α = 1,21) respectively. A similar comparison is observed for design shear effects for both types of track for heavy loads (α = 1,10) and (α = 1,21) for a carefully maintained track. Generally, there is not a good comparison with that of the Eurocode for static and design bending moment, for three span continuous railway bridges.
35
Morrill, Jake L. "Live-Load Test and Finite-Element Model Analysis of a Steel Girder Bridge." DigitalCommons@USU, 2016. https://digitalcommons.usu.edu/etd/5077.
Повний текст джерелаАнотація:
The Utah Transportation Center, in conjunction with the Mountain Plains Consortium, sponsored a study that investigated the distribution factors and load ratings of a continuous, steel I-girder bridge. The SH-52 Bridge over the Snake River is located on the Idaho-Oregon border near Payette, Idaho. The bridge was built in the 1950’s and presently supports two lanes of traffic.
A finite-element model of the bridge was calibrated with the results from a liveload test. For the live-load test, the bridge was instrumented at nine longitudinal cross section locations with 62 strain gauges attached on the girders, stringers, and intermediate diaphragms. The live-load was applied with two heavy trucks that were driven along three predetermined load paths.
The calibrated finite-element model was used to quantify moment distribution factors and load ratings for the bridge. The finite-element distribution factors were compared to those calculated according to the AASHTO Standard and AASHTO LRFD Specifications. The distribution factors from both AASHTO codes were found to be unconservative for the girders and overly conservative for the stringers.
The model was also used to quantify the effect of the transverse diaphragm members on the live-load distribution. Distribution factors were calculated with and without the diaphragm members. The diaphragms were found to increase the distribution of moments by over 20% for both positive and negative moments.
36
Jamali, Shojaeddin. "Assessing load carrying capacity of existing bridges using SHM techniques." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/134484/1/Shojaeddin_Jamali_Thesis.pdf.
Повний текст джерелаАнотація:
This research provides a multi-tier framework for load carrying capacity assessment of bridges using structural health monitoring techniques. In this framework, four tiers are developed ranging from simplified to detailed tiers for holistic bridge assessment. Performance of each tier has been validated using various numerical and experimental examples of bridges and beam-like structures.
37
Petroff, Steven M. "The Utah Pilot Bridge, Live Load and Dynamic Testing, Modeling and Monitoring for the Long-Term Bridge Performance Program." DigitalCommons@USU, 2010. https://digitalcommons.usu.edu/etd/723.
Повний текст джерелаАнотація:
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.
38
Mutashar, Rana O. "Response of Skewed Composite Adjacent Box Beam Bridge to Live and Environmental Load Conditions." Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1597020452615694.
Повний текст джерела
39
Fausett, Robert W. "Live-Load Test and Finite-Model Analysis of an Integral Abutment Concrete Girder Bridge." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/2018.
Повний текст джерелаАнотація:
As part of the Long Term Bridge Performance (LTBP) Program, a single-span, prestressed, integral abutment concrete girder pilot bridge near Perry, Utah was instrumented with different sensors at various locations onto the bridge for long-term monitoring and periodic testing. One of the periodic tests conducted on this bridge was a live-load test. The live-load test included driving trucks across the bridge, as well as parking trucks along different lanes of the bridge, and measuring the deflection and strain. The data collected from these tests was used to create and calibrate a computer model of the bridge. The model was afforded the same dimensions and characteristics as the actual bridge, and then the boundary conditions (how the bridge is being supported) were altered until the model data and the live-load data matched. Live-load distribution factors and load ratings were then obtained using this calibrated model and compared to the AASHTO LRFD Bridge Design Specifications. The results indicated that in all cases, the AASHTO LRFD Specification distribution factors were conservative by between 55% to 78% due to neglecting to take the bridge fixity (bridge supports) into account in the distribution factor equations. The actual fixity of the bridge was determined to be 94%.Subsequently, a variable study was conducted by creating new models based on the original bridge for changes in span length, deck thickness, edge distance, skew (angle of distortion of the bridge), and fixity to see how each variable would affect the bridge. Distribution factors were then calculated for each case and compared with the distribution factors obtained from the AASHTO LRFD Specifications for each case. The results showed that the variables with the largest influence on the bridge were the change in fixity and the change in skew. Both parameters provided ranges between 10% non- conservative and 56% conservative. The parameter with the least amount of influence was the deck thickness providing a range between 4% non-conservative and 19% non- conservative. Depending on which variable was increased, both increases and decreases in conservatism were exhibited in the study.
40
Torres, Victor J. "Live Load Testing and Analysis of a 48-Year-Old Double Tee Girder Bridge." DigitalCommons@USU, 2016. https://digitalcommons.usu.edu/etd/4962.
Повний текст джерелаАнотація:
A 48-year-old prestressed double tee girder bridge located on Icy Springs road in Coalville, Utah, was tested for live load. The test measured strains, deflections and rotations. The instruments used for measuring the respective measurements were strain gages, deflectometers ("twangers") and tiltmeters.
From the recorded measurements a finite element model (FEM) was calibrated to validate the modeling techniques based on the test data. The FEM implemented two joint link elements to connect the flanges of the FEM deck to model the transverse load distribution of the bridge deteriorated shear connectors. The abutment restraints were modeled by one joint link elements. The deck and the stems were modeled using shell element.
After validating the modeling techniques, a parametric study was developed to study the prediction of FEM girder distribution factors (GDF). The FEM GDF predictions were compared to the prediction proposed by the American Association of State Highway and Transportation Officials (AASHTO) in the provision AASHTO LRFD 2010. The parametric study considered the variable parameters of span length, slab thickness, number of double tees, angle of skew, and stem spacing.
The AASHTO specification provides an inaccurate prediction, therefore a new statistical model was proposed to better predict GDF. Furthermore, rating factors based on different girder distribution factors were studied for the Icy Springs bridge. The bridge has a passing rate for operating level.
41
Collins, William Norfleet. "Live Load Testing and Analysis of the Southbound Span of U.S. Route 15 over Interstate-66." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/34364.
Повний текст джерелаАнотація:
As aging bridges around the United States begin to near the end of their service lives,
more funding must be allocated for their rehabilitation or replacement. The Federal Highway
Administrationâ s (FHWA) Long-Term Bridge Performance (LTBP) Program has been developed
to help bridge stakeholders make the best decisions concerning the allocation of these funds.
This is done through the use of high quality data obtained through numerous testing processes.
As part of the LTBP Pilot Program, researchers have performed live load tests on the
U.S. Route 15 Southbound bridge over Interstate-66. The main performance and behavior
characteristics focused on are service strain and deflection, wheel load distribution, dynamic load
allowance, and rotational behavior of bridge bearings.
Data from this test will be used as a tool in developing and refining a plan for long-term
bridge monitoring. This includes identifying the primarily loaded girders and their expected
range of response under ambient traffic conditions. Information obtained from this test will also
aid in the refinement of finite element models by offering insight into the performance of
individual bridge components, as well as overall global behavior. Finally, the methods and
results of this test have been documented to allow for comparison with future testing of this
bridge, which will yield information concerning the changes in bridge behavior over time.Master of Science
42
Taghinezhadbilondy, Ramin. "Extending Use of Simple for Dead Load and Continuous for Live Load (SDCL) Steel Bridge System to Seismic Areas." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2986.
Повний текст джерелаАнотація:
The steel bridge system referred to as Simple for Dead load and Continuous for Live load (SDCL) has gained popularity in non-seismic areas of the country. Accordingly, it results in many advantages including enhanced service life and lower inspection and maintenance costs as compared to conventional steel systems. To-date, no research studies have been carried out to evaluate the behavior of the SDCL steel bridge system in seismic areas. The main objective of this research was to extend the application of SDCL to seismic areas.
The concept of the SDCL system was developed at the University of Nebraska-Lincoln and a complete summary of the research is provided in five AISC Engineering Journal papers. The SDCL system is providing steel bridges with new horizons and opportunities for developing economical bridge systems, especially in cases for which accelerating the construction process is a priority. The SDCL steel bridge system also provides an attractive alternative for use in seismic areas.
The SDCL concept for seismic areas needed a suitable connection between the girder and pier. In this research, an integral SDCL bridge system was considered for further investigation. The structural behavior and force resistance mechanism of the proposed seismic detail considered through analytical study. The proposed connection evaluated under push-up, push-down, inverse and axial loading to find the sequence of failure modes. The global and local behavior of the system under push-down forces was mainly similar to non-seismic detail. The nonlinear time history analysis indicated that there is a high probability that bottom flange sustains tension forces under seismic events. The finite element model subjected to push-up forces to simulate the response of the system under the vertical component of seismic loads. However, the demand-capacity ratio was low for vertical excitation of seismic loads. Besides finite element results showed that continuity of bottom flange increased ductility and capacity of the system. While the bottom flange was not continuous, tie bars helped the system to increase the ultimate moment capacity. To model the longitudinal effect of earthquake loads, the model subjected under inverse forces as well as axial forces at one end. In this case scenario, dowel bars were most critical elements of the system. Several finite element analyses performed to investigate the role of each component of preliminary and revised detail. All the results demonstrated that continuity of the bottom flange, bolts area (in the preliminary detail), tie bars over the bottom flange (in the revised detail) were not able to provide more moment capacity for the system. The only component increased the moment capacity was dowel bars. In fact, increasing the volume ratio of dowel bars could be able to increase the moment capacity and prevent premature failure of the system.
This project was Phase I of an envisioned effort that culminated in the development of a set of details and associated design provisions to develop a version of the SDCL steel bridge system, suitable for the seismic application. Phase II of this project is an ongoing project and currently the component specimen design and test setup are under consideration. The test specimen is going to be constructed and tested in the structures lab of Florida International University. A cyclic loading will be applied to the specimen to investigate the possible damages and load resistance mechanism. These results will be compared with the analysis results. In the next step, as phase III, a complete bridge with all the components will be constructed in the structures lab at the University of Nevada-Reno. The connection between steel girders will be an SDCL connection and the bridge will be subjected to a shake table test to study the real performance of the connection due to earthquake excitation.
43
Laurendeau, Matthew P. "Live-Load Testing and Finite-Element Analysis of a Steel Cantilever Deck Arched Pratt Truss Bridge for the Long-Term Bridge Performance Program." DigitalCommons@USU, 2011. https://digitalcommons.usu.edu/etd/904.
Повний текст джерелаАнотація:
The Long Term Bridge Performance (LTBP) program is an organization within the Federal Highway Administration that inspects, tests, analyzes, and observes, for an extended period of time, a variety of bridge types throughout the United States. Part of the program includes periodic testing of select bridges of a span of 20 years. The Kettle River Bridge located outside of Sandstone, Minnesota was selected for study due to its unique design.
The Kettle River Bridge is a historical steel cantilevered deck arched Pratt truss bridge. The bridge was instrumented with 151 strain gauges on various floor and truss members along with eight displacement gauges strategically placed along the truss. All gauges were read simultaneously as the bridge underwent non-destructive live loading. The recorded gauge readings were analyzed to determine bridge behavior and then used in the assistance of calibrating a working finite-element model.
After a working model was verified the distribution factors for the interior and exterior floor stringers were determined. By using the controlling distribution factor, a load rating for the bridge was determined for both inventory and operating. The distribution factors and load ratings determined using the working finite-element model were then compared to the AAHSTO LRFD specifications.
44
Field, Carrie Stoshak. "VHPC Material Characterization and Recommendations for the Buffalo Branch Bridge Rehabilitation." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/75066.
Повний текст джерелаАнотація:
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
45
Duran, Heriberto C. "ASSESSMENT OF LIVE LOAD DEFLECTIONS IN A SIMPLE SPAN COMPOSITE BRIGDE WITH PRESTRESSED PRECAST CONCRETE GIRDERS." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/1862.
Повний текст джерелаАнотація:
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.
46
Dykas, Julia Catherine. "Behavior during construction of ramp B over I-40 in Nashville, TN." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43711.
Повний текст джерелаАнотація:
The construction of curved I-girder bridges generally requires detailed attention to the steel erection plan as well as the deck placement sequence. There is limited quantitative information available on the performance of large curved bridges under construction. This study seeks to address this limitation through the study of a curved ramp I-girder bridge. The bridge under study is the last of several bridges needed to complete the interchange between I-40 and Briley Parkway (TN SR155) in western Nashville, TN.
The study consists of three parts. First, the bridge was instrumented and its behavior during construction was monitored using vibrating wire strain gages, clinometers, and a robotic total station. Through these technologies it was possible to monitor changes in strain/stress, angle of rotation, and deflections throughout the girder erection, installation of concrete formwork, and concrete placement. Second, a static load test of the completed bridge was conducted using ten trucks loaded to a total weight of 72 kips each, during which measurements of the stress/strain and deflections were acquired. Finally, the collected data was compared to analytical results obtained from a 3D finite element analysis (FEA) model to assess the correlation between measurements and refined analytical predictions. The refined 3D FEA predictions are used as a baseline for evaluation of various simplified analysis methods in a parallel National Cooperative Highway Research Program project, NCHRP 12-79, Guidelines for Analytical Methods and Construction Engineering of Curved and Skewed Steel Girder Bridges. Overall, the comparisons show that the 3D FEA model provides a reasonable approximation of the bridge's behavior in terms of both stresses and deflections.
47
Kang, Wen. "A line and load independent zero voltage switching dc/dc full bridge converter topology." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ59307.pdf.
Повний текст джерела
48
Pockels, Leonardo A. "Live-Load Test and Computer Modeling of a Pre-Cast Concrete Deck, Steel Girder Bridge, and a Cast-in-Place Concrete Box Girder Bridge." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/508.
Повний текст джерелаАнотація:
The scheduled replacement of the 8th North Bridge, in Salt Lake City, UT, presented a unique opportunity to test a pre-cast concrete deck, steel girder bridge. A live-load test was performed under the directions of Bridge Diagnostic Inc (BDI) and Utah State University. Six different load paths were chosen to be tested. The recorded data was used to calibrate a finite-element model of this superstructure, which was created using solid, shell, and frame elements. A comparison between the measured and finite-element response was performed and it was determined that the finite-element model replicated the measured results within 3.5% of the actual values. This model was later used to obtain theoretical live-load distribution factors, which were compared with the AASHTO LRFD Specifications estimations. The analysis was performed for the actual condition of the bridge and the original case of the bridge, which included sidewalks on both sides. The comparison showed that the code over predicted the behavior of the actual structure by 10%. For the original case, the code's estimation differed by as much as 45% of the theoretical values. Another opportunity was presented to test the behavior of a cast-in-place concrete box girder bridge in Joaquin County, CA. The Walnut Grove Bridge was tested by BDI at the request of Utah State University. The test was performed with six different load paths and the recorded data was used to calibrate a finite-element model of the structure. The bridge was modeled using shell elements and the supports were modeled using solid elements. The model was shown to replicate the actual behavior of the bridge to within 3% of the measured values. The calibrated model was then used to calculate the theoretical live-load distribution factors, which allowed a comparison of the results with the AASHTOO LRFD Specifications equations. This analysis was performed for the real conditions of the bridge and a second case where intermediate diaphragms were not included. It was determined that the code's equations estimated the behavior of the interior girder more accurately for the second model (within 10%) than the real model of the bridge (within 20%).
49
Turer, Ahmet. "CONDITION EVALUATION AND LOAD RATING OF STEEL STRINGER HIGHWAY BRIDGES USING FIELD CALIBRATED 2D-GRID AND 3D-FE MODELS." University of Cincinnati / OhioLINK, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ucin985895002.
Повний текст джерела
50
Kasera, Sudarshan Chakradhari. "Simulation of the effect of deck cracking due to creep and shrinkage in single span precast/prestressed concrete bridges." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1416233864.
Повний текст джерела