Abstract
Half-joint beams, also referred to as dapped-end beams, have been the subject of several studies, primarily focussing on the design optimisation of new reinforced concrete beams and bridge decks. Existing half-joint structures, however, often show signs of deterioration and can exhibit improper reinforcement detailing. In order to gain a better insight into the impact of local corrosion, anchorage cracking, limited amounts of provided shear reinforcement, and improper reinforcement detailing, a test program was designed. Full-scale tests on nine half-joint beams were performed.The results of the study show that even though the impact of an individual shortcoming on the load carrying capacity of reinforced concrete half-joint beams might not be substantial, inspectors and assessors should pay attention to the possibility of combined effects. When multiple deterioration processes are noted and/or questions are raised with respect to the reinforcement detailing, the impact on the load carrying capacity of the beam might be larger than the linear combination of the individual effects.
Highlights
Existing half-joint structures are vulnerable to deterioration processes and can exhibit improper reinforcement detailing
In order to gain a better insight into the impact of local corrosion at the inner nib, different degrees of cracking around the longitudinal tensile reinforcement, limited shear reinforcement, and improper reinforcement detailing, a test program studying these aspects was designed
Full-scale tests on 700 mm height, 400 mm wide half-joint beams led to the following observations:
Summary
Nicholas [6] reported the inspection details for two reinforced concrete half-joint bridges in Australia In both bridges, severe signs of deterioration were noted. Cracks were noted in the concrete on both the upper and lower half-joint nibs These cracks were partly attributed to the improper placement of the bearings and partly to reinforcement corrosion. Limited guidance is available for the assessment of concrete half-joints [1,2,12] These documents mainly relate to the effects of corrosion and crack widths. Reinforcement layout and detailing deficiencies can exist in older half-joint structures, as shown in the past by inspections that revealed discrepancies between as-designed and as-built reinforcement layouts [7] These inconsistencies may include missing reinforcing bars, relocated reinforcement and/or improper execution of reinforcement detailing (e.g. anchorages). After identifying the impact of these commonly found individual shortcomings, the stage is to look at the combination of deterioration and detailing deficiencies and start to provide the basis for guidance to assessors
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