Development of Headed Bars in Slab-Column Joints of Reinforced Concrete Slab Bridges

摘要

This paper presents results o f an investigation on the developmento f headed bars extending from a column into the slab o f areinforced concrete slab bridge. Three full-scale slab-columnspecimens were tested under quasi-static cyclic lateral loading todetermine the minimum embedment length requiredfor the headedbars to develop their full tensile capacity, and the reinforcementdetails needed in the slab-column joint region to prevent prematureanchorage failure, when a plastic hinge forms at the top o fthe column. The experimental results showed that for 5000 psi(34.5 MPa) concrete and Grade 60 steel, a development lengthequal io 11 times the bar diameter is adequate for headed bars inslab-column joints designed according to Caltrans specificationswith a minimum o f 2 in. (50.8 mm) o f clear concrete cover. Specimenswith shorter embedment lengths were able to develop themoment capacity o f the columns and showed significant ductility,but exhibited moderate to severe punching cracks in the coverconcrete o f the slabs. Finite element analyses o f slab-columnassemblies showed that punching damage can be eliminated byincreasing the concrete cover above the bar heads.