In the state of Ohio, semi-integral bridges have become more popular because these bridges eliminate high maintenance joints. The girders in a semi-integral bridge are encased in a diaphragm supported on elastomeric pads that bear on the abutment. Movement of the diaphragm caused by thermal change is theoretically resisted by backfill and also by the wingwalls for skewed bridges. The wingwalls are subjected to forces as a skewed bridge rotates during thermal expansion.
Jointless bridges, such as semi-integral and integral bridges, have become more popular in recent years because of their simplicity in the construction and the elimination of high costs related to joint maintenance. Prior research has shown that skewed semi-integral bridges tend to expand and rotate as the ambient air temperature increases through the season. As a result of the bridge movement, forces are generated and transferred to the wingwalls of the bridge. ODOT does not currently have a procedure to determine the forces generated in the wingwalls from the thermal expansion and rotation of skewed semi-integral bridges. In this study, two semi-integral bridges with skews were instrumented and monitored for behavior at the interface of the bridge's diaphragm and wingwall. A parametric analysis was also performed to determine the effects of different spans and bridge lengths on he magnitude of the forces. Based on the field results from the study it is recommended for the design of the wingwalls turned to run nearly parallel with the longitudinal axis of skewed semi-integral bridges should include a 100 psi loading at the wingwall/diaphragm interface from the thermal expansion of the bridge. In addition, analytical evaluations showed that longer spans and higher skews than allowed by ODOT's BDM could be used. However, additional considerations for larger movements and stresses generated at the wingwall/diaphragm interface would need to be considered in designs. Finally, bearing retainers in diaphragms, if used, require adequate cover to avoid spalling of concrete.
Bridges that utilize expansion joints have an overall higher maintenance cost due to leakage at the expansion joint leading to deterioration of the joint, as well as structural components beneath the joint including the superstructure and substructure. Jointless bridges, such as semi-integral and integral bridges, have become more popular in recent years because of their simplicity in the construction and the elimination of expansion joints. Jointless bridges also improve riding quality, promote lower impact loads, reduce snowplow damage to decks and approach slabs, as well as improve the seismic resistance of the bridge.
As jointless bridges become more popular, there is a greater need to understand all aspects of their behavior. Significantly more research has been conducted on integral abutment bridges than there has been on semi-integral abutment bridges, therefore there is a need for more investigation into this type of bridge. Parametric studies on jointless bridges in the past often dealt with variations of the superstructure like altering the span length or skew. This research is an examination of a unique case for a jointless bridge that aims to provide a look into the behavior of the substructure. The subject for the research is a semi-integral abutment bridge with turned back wingwalls and drilled shafts. Semi-integral bridges are less common than integral bridges, and one with turned back wingwalls is constructed even less frequently. The turned back wingwall style of this bridge makes it a good subject for research because little is known about the effect of wingwall orientation on the stress patterns throughout semi-integral abutments. This research will provide a look into the behavior of a semi-integral abutment as the wingwall angle is changed from turned back to flared.
This project was designed to enhance the Virginia Department of Transportation's expertise in the design of integral bridges, particularly as it applies to highly skewed structures. Specifically, the project involves extensive monitoring of a semi-integral (integral backwall) bridge with a 45-degree skew. Long-term, continuous monitoring of strains developed in foundation piles, earth pressures exerted on the backwall by the adjacent approach embankment, and concrete buttress reactions preventing the superstructure from rotating in the horizontal plane will be performed. Overall, 120 strain gages, 16 earth pressure cells, and 2 high-capacity load cells, interfaced with electronic dataloggers, will be used in the study. This report provides a record of work carried out from the start of construction in January 2006 to the beginning of May 2006. It specifically describes the instrumentation of the bridge. Future reports will provide an analysis of the results of the field monitoring program. The study is expected to continue for the next 2 years in order to capture the bridge's response over a wide range of climatic conditions.
The finite element models generally confirmed the findings of Smith (2014). The results of the 11- and 38-foot abutment finite element models confirmed that the wingwall on the obtuse side of the 45° skewed abutments experienced approximately 4 to 5 times the amount of horizontal soil pressure and 5 times the amount of bending moment compared to the non-skewed abutment. Increases in the pressures and bending moments are likely caused by soil confined between the obtuse side of the abutment and the wingwall.
A comparison of passive force per unit width suggests that MSE wall abutments provide 60% more passive resistance per unit width compared to reinforced concrete wingwall and unconfined abutment geometries at zero skew. These findings suggest that changes should be made to current codes and practices to properly account for skew angle in bridge design.
