"December 2018."; Includes bibliographical references (pages 26-29).; Final Report; Spo... more "December 2018."; Includes bibliographical references (pages 26-29).; Final Report; Sponsoring agency: Ohio Department of Transportation; State job number 135499Final report (30 pages, 90 unnumbered pages) -- [Fact sheet] (2 pages).Many bridge pier caps are deep due to short shear spans. When analyzed using the slender beam theory (i.e., the sectional method), a large number of pier caps are found to be shear-overloaded even though they don't exhibit any noticeable cracking or signs of distress. AASHTO LRFD 2017 recommends the use of either a strut-and-tie or nonlinear finite element model for the analysis and design of deep members. Both methods are more sophisticated and require more effort than the sectional method. The objective of this study was to simplify the strut-and-tie method for pier caps to obtain larger and less conservative shear capacity predictions. For this purpose, a solution algorithm (computer program) was developed based on Section 5.8.2 Strut-and-Tie Method of AASHTO LRFD 2017. The program, named STM-CAP (Strut-and-Tie Method for pier CAPs), is implemented in Microsoft Excel using Visual Basic macro codes. An adaptive graphical solution procedure was employed to minimize the input errors and give the analyst options for optimizing the automatically generated model. STM-CAP calculates the utilization ratio for every element, which reflects the condition (overload or reserve capacity percentage) of the pier cap. If overloaded, STM-CAP indicates the calculated failure mode and its location. Suitable rehabilitation methods and load limits can then be determined accordingly. STM-CAP is verified using a generalpurpose strut-and-tie software, CAST (Computer Aided Strut and Tie) and VecTor2 (a nonlinear finite element analysis software) for eight existing pier caps located in Ohio. In addition, the sectional method calculations were performed to demonstrate the extra shear capacity predictions obtained from the strut-and- tie method. The strut-and-tie method predicted 2 to 3 times higher shear capacities for beams with shear span-to-depth ratio (a/d) of 0.50. The predictions by STM-CAP and the sectional method converge as the a/d ratios approach 3.0. The research results have a potential to result in significant cost savings by rehabilitating fewer pier caps and reducing the associated construction work and traffic disruption. The developed program, STM-CAP, can also be used when load rating concrete pier caps
IABSE Congress, New York, New York 2019: The Evolving Metropolis, 2019
A significant portion of the nation’s aging bridge inventory consists of bridges with deep cap be... more A significant portion of the nation’s aging bridge inventory consists of bridges with deep cap beams which were not designed to carry modern traffic loads. A strength assessment of these bridges is required for accurately predicting their load and deformation capacities. This paper proposes a two-stage strength assessment methodology for deep cap beams based on a nonlinear finite element analysis. To validate the finite element modeling approach, five pier caps experimentally investigated in the literature were analyzed. Crack patterns, load-displacement response, failure modes, and governing critical members were investigated under near collapse conditions. The complete proposed methodology was employed on a case study involving five existing bridges located in Ohio and the predicted capacities were compared with the traditional sectional and strut-and-tie methods. The proposed methodology has the potential to reduce the number of bridges found overloaded using traditional methods,...
Synopsis: Due to the increase in traffic and transported freight in the past decades, a significa... more Synopsis: Due to the increase in traffic and transported freight in the past decades, a significant number of in-service bridges have been subjected to loads above their original design capacities. Bridge structures typically incorporate deep concrete elements, such as cap beams or bent caps, with higher shear strengths than slender elements. However, many in-service bridges did not account for the deep beam effects in their original design due to the lack of suitable analysis methods at that time. Nonlinear finite element analysis (NLFEA) can provide a better assessment of the load capacity of deep bridge bent beams while accounting for the deep beam action. However, there is little guidance on how to conduct a numerical strength evaluation using the NLFEA. This study presents a nonlinear modeling methodology for the strength evaluation of deep bridge bents while considering advanced concrete behavior such as tension stiffening, compression softening, and dowel action. Five existin...
"December 2018."; Includes bibliographical references (pages 26-29).; Final Report; Spo... more "December 2018."; Includes bibliographical references (pages 26-29).; Final Report; Sponsoring agency: Ohio Department of Transportation; State job number 135499Final report (30 pages, 90 unnumbered pages) -- [Fact sheet] (2 pages).Many bridge pier caps are deep due to short shear spans. When analyzed using the slender beam theory (i.e., the sectional method), a large number of pier caps are found to be shear-overloaded even though they don't exhibit any noticeable cracking or signs of distress. AASHTO LRFD 2017 recommends the use of either a strut-and-tie or nonlinear finite element model for the analysis and design of deep members. Both methods are more sophisticated and require more effort than the sectional method. The objective of this study was to simplify the strut-and-tie method for pier caps to obtain larger and less conservative shear capacity predictions. For this purpose, a solution algorithm (computer program) was developed based on Section 5.8.2 Strut-and-Tie Method of AASHTO LRFD 2017. The program, named STM-CAP (Strut-and-Tie Method for pier CAPs), is implemented in Microsoft Excel using Visual Basic macro codes. An adaptive graphical solution procedure was employed to minimize the input errors and give the analyst options for optimizing the automatically generated model. STM-CAP calculates the utilization ratio for every element, which reflects the condition (overload or reserve capacity percentage) of the pier cap. If overloaded, STM-CAP indicates the calculated failure mode and its location. Suitable rehabilitation methods and load limits can then be determined accordingly. STM-CAP is verified using a generalpurpose strut-and-tie software, CAST (Computer Aided Strut and Tie) and VecTor2 (a nonlinear finite element analysis software) for eight existing pier caps located in Ohio. In addition, the sectional method calculations were performed to demonstrate the extra shear capacity predictions obtained from the strut-and- tie method. The strut-and-tie method predicted 2 to 3 times higher shear capacities for beams with shear span-to-depth ratio (a/d) of 0.50. The predictions by STM-CAP and the sectional method converge as the a/d ratios approach 3.0. The research results have a potential to result in significant cost savings by rehabilitating fewer pier caps and reducing the associated construction work and traffic disruption. The developed program, STM-CAP, can also be used when load rating concrete pier caps
IABSE Congress, New York, New York 2019: The Evolving Metropolis, 2019
A significant portion of the nation’s aging bridge inventory consists of bridges with deep cap be... more A significant portion of the nation’s aging bridge inventory consists of bridges with deep cap beams which were not designed to carry modern traffic loads. A strength assessment of these bridges is required for accurately predicting their load and deformation capacities. This paper proposes a two-stage strength assessment methodology for deep cap beams based on a nonlinear finite element analysis. To validate the finite element modeling approach, five pier caps experimentally investigated in the literature were analyzed. Crack patterns, load-displacement response, failure modes, and governing critical members were investigated under near collapse conditions. The complete proposed methodology was employed on a case study involving five existing bridges located in Ohio and the predicted capacities were compared with the traditional sectional and strut-and-tie methods. The proposed methodology has the potential to reduce the number of bridges found overloaded using traditional methods,...
Synopsis: Due to the increase in traffic and transported freight in the past decades, a significa... more Synopsis: Due to the increase in traffic and transported freight in the past decades, a significant number of in-service bridges have been subjected to loads above their original design capacities. Bridge structures typically incorporate deep concrete elements, such as cap beams or bent caps, with higher shear strengths than slender elements. However, many in-service bridges did not account for the deep beam effects in their original design due to the lack of suitable analysis methods at that time. Nonlinear finite element analysis (NLFEA) can provide a better assessment of the load capacity of deep bridge bent beams while accounting for the deep beam action. However, there is little guidance on how to conduct a numerical strength evaluation using the NLFEA. This study presents a nonlinear modeling methodology for the strength evaluation of deep bridge bents while considering advanced concrete behavior such as tension stiffening, compression softening, and dowel action. Five existin...
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