A Simplified Analytical Approach for Web-Shear Strength Predictions of Extruded PCHC Slabs

Prestressed concrete hollow core (PCHC) slabs are efficient structural members in residential or industrial buildings. However, the shear capacity of such slabs became a concern due to the reduced sectional areas and the lack of shear reinforcement. Previous studies show that web-shear capacity predictions by existing approaches for PCHC slabs are still far from satisfactory. To fill this gap, a modified analytical model was proposed in this study to achieve more rational shear-capacity predictions for PCHC slabs. In the model, a biaxial compression-tension failure criterion was employed to overcome the maximum tensile stress failure criterion in traditional approaches. Further, the critical point was assumed to start at an angle of 35°C from inner edge of supports, interacting with the midheight of PCHC slabs with circular voids or the intersection point of the bottom flange and the web for noncircular-void slabs. The assumption regarding the critical point is based on a minor adjustment from EN 1168:2005+A3:2011 and Yang’s method. The proposed model was then validated using experimental data of 171 hollow-core slabs from published literatures; a series of sensitivity studies were also conducted to finalize design parameters of the model. Comparisons between existing approaches and the proposed model were performed to evaluate the new method. It was shown that the application of the biaxial failure criterion had a significant impact on providing reasonable and accurate shear-strength predictions for deep PCHC slabs. Parametric studies were also conducted by the model to evaluate the effects of transmission length, bearing size, and prestressing level on web-shear behavior of PCHC slabs. Shear strength reduced with increasing transmission length, decreasing bearing size or reducing prestress level.