Serviceability-related Issues for Bridge Live Load Deflection and Construction Closure Pours
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This study investigated the design criteria and practices in an effort to improve the quality of bridge designs in the State of Maryland and beyond. This first criterion investigated was the live load deflection for steel bridges. The second design/construction criterion investigated was designing and detailing bridge deck closure pours. Previous and current practices and future planning on the serviceability of bridges have been documented. State-of-the-practice methods from federal and other state agencies were collected. Three bridges were chosen for refined analyses to investigate the live load deflections. Field measurements for these three bridges were collected from the research team to facilitate this study. Thirty steel girder bridges from the Maryland State Highway Administration’s (SHA) inventory were selected for statistical analyses. Steel bridges designed with the live load deflection limit have been evaluated. Closure-pour analyses were conducted by line-girder models, two-dimensional grid models or three-dimensional finite element models. All three methods generate accurate enough camber diagrams to predict differential deflections between stages for straight girder systems, if creep is not considered. Creep effect could be alleviated by proper camber and scheduling on pouring.Keywords:
Serviceability (structure)
Limit state design
Structural load
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In recent years, prestressed concrete bridges have dominated the bridge type selection processes in Colorado. This can be attributed to a lack of steel mills combined with a strong presence of precast fabricators in the region. In addition, a lack of readily available economical and innovative procedures to design and construct steel bridges has hindered the industry in certain areas such as Colorado. During this research it was identified that designing steel girders as simply supported for the non composite dead loads and continuous for composite dead loads and live loads would provide economy. A preliminary girder selection software was created using this design procedure. The software takes user inputted data, such as span length, width, number of girders along with various other design inputs, and displays the lightest wide flange beam size that would support the loads using AASHTO Load and Resistance Factor Design (LRFD) Specifications. Using the girder selection software, design charts and tables were created to outline structural steel weight to span length and number of girders. The design charts will aid the bridge type selection process by giving designers an accurate measurement of minimum steel requirements for numerous one, two, and three span steel bridges. This research has provided the Colorado Department of Transportation (CDOT) and others who will use the software or design charts a tool that will facilitate the construction of innovative steel girder bridges.
Flange
Precast concrete
Bridge (graph theory)
Structural load
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Transversely stressed precast concrete deck unit bridges are a common type of small and medium span bridge on the Queensland road network. This type of bridge is unique in design featuring transverse posttensioned stressing bars with a low level of prestressing, stiff upright kerb units and no shear keys. Recent structural assessments of these bridge types has yielded varied and at times inconsistent results, with theoretical structural deficiencies identified at odds with the lack of evidence of structural distress, demonstrating acceptable performance. A test program was developed to address this disparity and improve understanding of the structural performance of these bridge types. This included static and dynamic load testing with various vehicle types, and long-term monitoring of the behaviour of a representative bridge under ambient traffic. The test results have enabled improved understanding of the behaviour and true capacity of this bridge type, as well as providing inputs to enable validation of analytical structural modelling techniques.
Precast concrete
Bridge (graph theory)
Structural Health Monitoring
Bridge deck
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Limit state design
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Bridge (graph theory)
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Bridge (graph theory)
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The history and present use of bridge testing are reviewed. The benefits of bridge testing include safety and reliability, the money saved by not constructing a new bridge, the improvement of bridge analysis and design procedures, the development of new bridge measurements as a load survey tool, and the maintenance of testing procedures as an integral part of inventory and rating. Bridge tests are used to determine load distribution, ultimate load, load history, and dynamic response. Both highway and railroad bridges are explored, and the examples of bridges tested include: steel, concrete, aluminum, orthotropic plate decks, suspension spans, rigid frame, timber and prestressed concrete. Tests which evaluate cracks and hardness are examined. Steps for testing transducers, signal conditioning and amplification, and data recording and processing are described. The text was prepared by the ASCE working committee on Safety of Bridges under the Technical Committee on Structural Safety and Reliability.
Bridge (graph theory)
Load testing
Prestressed concrete
Orthotropic material
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The inspection and evaluation of bridges in Indiana is critical to ensure their safety to better serve the citizens of the state. Part of this evaluation includes bridge load rating. Bridge load rating, which is a measure of the safe load capacity of the bridge, is a logical process that is typically conducted by utilizing critical information that is available on the bridge plans. For existing, poorly-documented bridges, however, the load rating process becomes challenging to adequately complete because of the missing bridge information. Currently, the Indiana Department of Transportation (INDOT) does not have a prescribed methodology for such bridges. In an effort to improve Indiana load rating practices INDOT commissioned this study to develop a general procedure for load rating bridges without plans. The general procedure was developed and it was concluded that it requires four critical parts. These parts are bridge characterization, bridge database, field survey and inspection, and bridge load rating. The proposed procedure was then evaluated on two bridges in Indiana that do not have plans as a proof of concept. As a result, it was concluded that load rating of bridges without plans can be successfully completed using the general procedure. A flowchart describing the general procedure was created to make the load rating process more user-friendly. Additional flowcharts that summarize the general procedure for different type of bridges were also provided.
Bridge (graph theory)
Flow chart
Load testing
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The bridges built during the development of the Dutch road network after the Second World War are reaching their originally devised service life. A large subset of the Dutch bridge stock consists of reinforced concrete slab bridges. This bridge type often rates insufficient according to the recently introduced Eurocodes. Therefore, more suitable methods are developed to assess reinforced concrete slab bridges to help transportation officials make informed decisions about the safety and remaining life of the existing bridges. If information about a bridge is lacking, if the reduction in structural capacity caused by material degradation is unknown, or if an assessment shows insufficient capacity but additional capacity can be expected, a bridge might be suitable for a field test. A proof load test demonstrates that a given bridge can carry a certain load level. In the Netherlands, a number of existing reinforced concrete slab bridges have been proof loaded, and one bridge has been tested to collapse. Bridges with and without material damage were tested. These bridges were heavily instrumented, in order to closely monitor the behavior of the bridge. Critical positions for bending moment and shear were studied. Based on the proof load tests that were carried out over the past years, a set of recommendations for the systematic preparation, execution, and analysis of proof load test results is compiled. These recommendations will ultimately form the basis of the guideline for proof load testing for the Netherlands, which is currently under development.
Bridge (graph theory)
Eurocode
Slab
Service life
Load testing
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