Bursting and Spalling in Pretensioned U-Beams - Ferguson ...

The amount of transverse reinforcement provided in an end region was also foundto influence maximum transverse-bar stresses at transfer of prestress. The specimens inthe database were split between those meeting and those not meeting the AASHTOLRFD requirement for transverse reinforcement within the h/4 design length. Half ofbeams not meeting the code requirement had a maximum bursting/spalling stressexceeding the 20-ksi limit; a quarter of those meeting the code exceeded the limit(Figure 4.23).Figure 4.23 Contribution of reinforcement provided within end h/4 region(normalized by that required by AASHTO LRFD)to high maximum transverse-bar bursting/spalling stressThe effect of bottom-fiber stress on maximum transverse-bar bursting/spallingstress appears to be quite strong (Figure 4.24), but is moderated by the fact thatapproximately 60% (8 of 14) of the specimens subject to high sectional stresses also hadLRFD-insufficient transverse reinforcement in their end-regions. Still nearly 80% ofspecimens with bottom-fiber stresses greater than 3.6 ksi (i.e. 60% allowable compressive177