In-Span Splicing for Continuous Prestressed Concrete Girder Bridges

Abstract

When bridge spans exceed 45 m it is necessary to have modular construction methods to effectively join the segments in-span and form a continuous structure with substantially longer span lengths. In-span splicing of prestressed concrete girders to extend span length of bridges have been effectively used in several recent bridge construction projects. However, the extent and limitation of such a construction approach, as well as associated analysis and design challenges have not been systematically explored.

Concepts of deflection balancing and load balancing were considered to provide a platform for design of slab-on-in-span spliced prestressed concrete girder bridges. Three methods of construction were investigated that benefit from in-span splices: shored, partially shored, and heavy-lift construction. Design procedures and construction sequences were compared and contrasted, and discussed in detail. A prototype bridge geometry was designed for all three methods of construction approaches, and the results compared and conclusions drawn.

From the prototype design, an experimental test specimen was abstracted and an experimental testing investigation described. Three test setups were adapted to investigate the performance of each of the three splices, in three different load combinations. Results were presented for the full-scale laboratory tests on each splice regions under service load through to failure.

Based on the results of the experimental investigation, diagonal cracks in the splice regions of prestressed concrete girder bridges may adversely affect the flexural behavior of the splices and reduce their post-cracked ultimate strength and deformability. A generalized moment-curvature approach was developed along a diagonal crack plane to directly account for the effects of flexure-shear interaction. A formulation was provided to calculate the nominal capacity of such sections incorporating the interacting effects of flexure and shear.

A Compatibility Strut-and-Tie Modeling (C-STM) was introduced as an effective alternative method of structural analysis for when members were subjected to high moment demands coupled with high shear intensity. The C-STM approach was advanced to model the behavior of slab-on-spliced prestressed concrete girder bridges where shear-flexure interaction may influence system performance particularly near regions that are spliced. The efficacy of the approach was demonstrated by modeling the experimental performance of the test specimen.