Evaluation of bridge component design and construction techniques: A look at integral abutment bridge precast approach slabs and post grouted drilled shafts

Abstract

The bump at the end of the bridge and the high cost of deep embedded drilled shafts have long been recognized by many bridge owners. This research aims to mediate the bump at the end of the bridge and to validate the use of post grouting to increase drilled shaft capacity. Performance monitoring and full scale test programs were used to evaluate these technical issues. The bump at the end of the bridge is typically due to settlement of the approach soils and cracking of the approach pavements. The settlement and cracking in integral abutment bridges are typically dealt with by connecting the approach slab to the integral abutment bridge. Two integral abutment bridges with integrally connected precast approach slabs were evaluated using long-term monitoring systems to study their structural performance and determine the range of forces that should be considered when designing such approach slabs. This study has identified design and construction considerations for integrally connected precast approach slabs. The approach slab study revealed the source and magnitude of forces to be considered in the design and construction of approach slabs integrally connected to integral abutment bridges. Consideration of these forces in the design and construction of such approach slabs could potentially lead to reduced maintenance costs associated with the bump at the end of the bridge. The required deep embedment length of drilled shafts is due to the inability to fully mobilize the end bearing resistance of the shaft before reaching service displacement criteria. Post grouting of drilled shafts can be used to effectively increase the end bearing capacity within service displacement limits, often times allowing the drilled shaft to be shortened without sacrificing capacity. Through a load test program and long-term performance monitoring of production shafts, the increase in capacity and performance of post grouted drilled shafts were investigated. This study has identified design and construction considerations for post grouted drilled shafts. The post grouted drilled shaft study verified the use of post grouting as a technique for increasing the end bearing resistance of drilled shafts and also identified design and construction considerations for post grouted drilled shafts. Increasing the end bearing resistance of drilled shafts through the use of post grouting can