Field Monitoring and Evaluation of Curved Girder Bridges with Integral Abutments

The National Cooperative Highway Research Program (NCHRP) has shown concerns regarding the design, fabrication, and erection of horizontally curved steel girder bridges due to unpredicted girder displacements, fit-up, and locked-in stresses. Nationally, up to one-quarter of steel girder bridges are being designed with horizontal curvature, an alarming figure when considering the unknown behaviors of this type of bridge. The primary objective of this work was to monitor and evaluate the behavior of four in-service, horizontally curved, steel-girder bridges with integral and semi-integral abutments. Additionally, the influence and behavior of fixed and expansion piers were considered. A number of steps were performed in order to meet the project objectives. First, a national state department survey was conducted and a literature review was performed in order to understand the state-of-art regarding these types of structures. Second, a monitoring program was developed and installed on six bridges located at the I-35, I-235, and I-80 interchange northeast of Des Moines. Third, a monthly survey was conducted on each bridge with the purpose of tracking the bridge movements, and lastly, the data gathered during the monitoring period of the project was post-processed. The following general conclusions were made from the results of the study: There was no measureable difference between the horizontally curved bridges and straight bridges used in this work with regard to bridge behavior; internal strains were recorded in the composite girders as a result of thermally induced restrained expansion and contraction, and of the recorded strains, axial strain showed the largest ranges; the bridges expanded and contracted with seasons and showed more expansion and contraction near expansion piers than fixed piers. The equivalent cantilever method of steel pile analysis fell short of accurately predicting the relationship between weak axis bending strain in the piles and the pile head displacement; the measured internal stress in the abutment piles due to expansion and contraction of the bridge were generally below 50% of yield stress; and the soil pressures on the abutment backwalls were generally below approximate passive soil pressures

Field Monitoring of Curved Girder Bridges with Integral Abutments

Nationally, there are questions regarding the design, fabrication, and erection of horizontally curved steel girder bridges due to unpredicted girder displacements, fit-up, and locked-in stresses. One reason for the concerns is that up to one-quarter of steel girder bridges are being designed with horizontal curvature. There is also an urgent need to reduce bridge maintenance costs by eliminating or reducing deck joints, which can be achieved by expanding the use of integral abutments to include curved girder bridges. However, the behavior of horizontally curved bridges with integral abutments during thermal loading is not well known nor understood. The purpose of this study was to investigate the behavior of horizontal curved bridges with integral abutment (IAB) and semi-integral abutment bridges (SIAB) with a specific interest in the response to changing temperatures. The long-term objective of this effort is to establish guidelines for the use of integral abutments with curved girder bridges. The primary objective of this work was to monitor and evaluate the behavior of six in-service, horizontally curved, steel-girder bridges with integral and semi-integral abutments. In addition, the influence of bridge curvature, skew and pier bearing (expansion and fixed) were also part of the study. Two monitoring systems were designed and applied to a set of four horizontally curved bridges and two straight bridges at the northeast corner of Des Moines, Iowa—one system for measuring strains and movement under long term thermal changes and one system for measuring the behavior under short term, controlled live loading. A finite element model was developed and validated against the measured strains. The model was then used to investigate the sensitivity of design calculations to curvature, skew and pier joint conditions. The general conclusions were as follows: (1) There were no measurable differences in the behavior of the horizontally curved bridges and straight bridges studied in this work under thermal effects. For preliminary member sizing of curved bridges, thermal stresses and movements in a straight bridge of the same length are a reasonable first approximation. (2) Thermal strains in integral abutment and semi-integral abutment bridges were not noticeably different. The choice between IAB and SIAB should be based on life – cycle costs (e.g., construction and maintenance). (3) An expansion bearing pier reduces the thermal stresses in the girders of the straight bridge but does not appear to reduce the stresses in the girders of the curved bridge. (4) An analysis of the bridges predicted a substantial total stress (sum of the vertical bending stress, the lateral bending stress, and the axial stress) up to 3 ksi due to temperature effects. (5) For the one curved integral abutment bridge studied at length, the stresses in the girders significantly vary with changes in skew and curvature. With a 10⁰ skew and 0.06 radians arc span length to radius ratio, the curved and skew integral abutment bridges can be designed as a straight bridge if an error in estimation of the stresses of 10% is acceptable

Field Monitoring and Evaluation of Curved Girder Bridges with Integral Abutments

The National Cooperative Highway Research Program (NCHRP) has shown concerns regarding the design, fabrication, and erection of horizontally curved steel girder bridges due to unpredicted girder displacements, fit-up, and locked-in stresses. Nationally, up to one-quarter of steel girder bridges are being designed with horizontal curvature, an alarming figure when considering the unknown behaviors of this type of bridge. The primary objective of this work was to monitor and evaluate the behavior of four in-service, horizontally curved, steel-girder bridges with integral and semi-integral abutments. Additionally, the influence and behavior of fixed and expansion piers were considered. A number of steps were performed in order to meet the project objectives. First, a national state department survey was conducted and a literature review was performed in order to understand the state-of-art regarding these types of structures. Second, a monitoring program was developed and installed on six bridges located at the I-35, I-235, and I-80 interchange northeast of Des Moines. Third, a monthly survey was conducted on each bridge with the purpose of tracking the bridge movements, and lastly, the data gathered during the monitoring period of the project was post-processed. The following general conclusions were made from the results of the study: There was no measureable difference between the horizontally curved bridges and straight bridges used in this work with regard to bridge behavior; internal strains were recorded in the composite girders as a result of thermally induced restrained expansion and contraction, and of the recorded strains, axial strain showed the largest ranges; the bridges expanded and contracted with seasons and showed more expansion and contraction near expansion piers than fixed piers. The equivalent cantilever method of steel pile analysis fell short of accurately predicting the relationship between weak axis bending strain in the piles and the pile head displacement; the measured internal stress in the abutment piles due to expansion and contraction of the bridge were generally below 50% of yield stress; and the soil pressures on the abutment backwalls were generally below approximate passive soil pressures.</p

Field Monitoring of Curved Girder Bridges with Integral Abutments

Nationally, there are questions regarding the design, fabrication, and erection of horizontally curved steel girder bridges due to unpredicted girder displacements, fit-up, and locked-in stresses. One reason for the concerns is that up to one-quarter of steel girder bridges are being designed with horizontal curvature. There is also an urgent need to reduce bridge maintenance costs by eliminating or reducing deck joints, which can be achieved by expanding the use of integral abutments to include curved girder bridges. However, the behavior of horizontally curved bridges with integral abutments during thermal loading is not well known nor understood. The purpose of this study was to investigate the behavior of horizontal curved bridges with integral abutment (IAB) and semi-integral abutment bridges (SIAB) with a specific interest in the response to changing temperatures. The long-term objective of this effort is to establish guidelines for the use of integral abutments with curved girder bridges. The primary objective of this work was to monitor and evaluate the behavior of six in-service, horizontally curved, steel-girder bridges with integral and semi-integral abutments. In addition, the influence of bridge curvature, skew and pier bearing (expansion and fixed) were also part of the study. Two monitoring systems were designed and applied to a set of four horizontally curved bridges and two straight bridges at the northeast corner of Des Moines, Iowa—one system for measuring strains and movement under long term thermal changes and one system for measuring the behavior under short term, controlled live loading. A finite element model was developed and validated against the measured strains. The model was then used to investigate the sensitivity of design calculations to curvature, skew and pier joint conditions. The general conclusions were as follows: (1) There were no measurable differences in the behavior of the horizontally curved bridges and straight bridges studied in this work under thermal effects. For preliminary member sizing of curved bridges, thermal stresses and movements in a straight bridge of the same length are a reasonable first approximation. (2) Thermal strains in integral abutment and semi-integral abutment bridges were not noticeably different. The choice between IAB and SIAB should be based on life – cycle costs (e.g., construction and maintenance). (3) An expansion bearing pier reduces the thermal stresses in the girders of the straight bridge but does not appear to reduce the stresses in the girders of the curved bridge. (4) An analysis of the bridges predicted a substantial total stress (sum of the vertical bending stress, the lateral bending stress, and the axial stress) up to 3 ksi due to temperature effects. (5) For the one curved integral abutment bridge studied at length, the stresses in the girders significantly vary with changes in skew and curvature. With a 10⁰ skew and 0.06 radians arc span length to radius ratio, the curved and skew integral abutment bridges can be designed as a straight bridge if an error in estimation of the stresses of 10% is acceptable.See also 2-page Techn Transfer Summary "Field Monitoring of Curved Girder Bridges with Integral Abutments" for overview of the report. Transportation Pooled Fund partners: Ohio DOT, Pennsylvania DOT, Wisconsin DOT, and Iowa DOT (lead state),</p