Joint-free bridges with engineered cementitious composite sliding approach slabs under static and fatigue loading

Abstract

Bridge end joints can be eliminated by sliding approach slab (SAS), where the deck extends over the abutment backwall onto approach fill. Engineered Cementitious Composite (ECC) exhibits crack control under tension and was incorporated into SASs in this study. Specimens made of end bridge span with ECC SAS were tested under static and fatigue (for 1,000,000 cycles) loading. Performance of the ECC SAS was assessed based on load–deflection and concrete/steel strain development responses during and after fatigue loading. It was observed that the approach slab transferred deflection and strain to the bridge span which should be considered in the design. ECC approach slab developed fine distributed cracks during the entire loading history, even after 1,000,000 fatigue cycles, and full depth cracking only occurred prior to failure. Finite element model of the end bridge span with ECC SAS was developed based on test results under static loading to conduct a parametric study on the impact of approach settlement on the structural capacity and failure mode. Parametric study revealed that the approach settlement caused a decrease in load and deflection capacity of SAS by 16% and 63%, respectively compared to no settlement. Parametric study with normal concrete sliding approach slab showed sudden increase in concrete and rebar strain, suggesting discrete brittle cracking compared with distributed cracking of its ECC counterpart. ECC SAS can help to improve flexibility under tension which is needed to accommodate bridge movements, and crack control for better structure durability.