Numerical web-shear strength assessment of precast prestressed hollow core slab units

The shear strength of precast prestressed hollow core (PPHC) slabs is numerically assessed for 200, 265, 320, 370, 400 and 500 mm thick units, the cross-sections of which present both circular and non-circular voids. The evolution of shear stress distributions and crack patterns is predicted by detailed nonlinear solid finite element (FE) analyses, matching experimental test data. A comparison is provided between experimental results and analytical estimates obtained by common design Codes (EC2, EN 1168, ACI and CSA), quantifying the inaccuracy of previous proposals which was shown to be particularly evident for deep slab sections with flat webs where the shear stress peak is localized below the centroidal axis. Numerical observations revealed the sensitivity of web-shear failure mechanism and related shear capacity to hollow core shape and related non-circularity of the voids, inherent web width variation along depth and concrete chords above and below the void. In light of these trends, a closed-form expression is proposed to be used as a preliminary-design-stage tool for analytical web-shear strength assessment of these members.