Concrete building construction typically relies on prestressed concrete hollow core slabs. The slabs’ hollow core makes them lighter weight than solid concrete and ultimately lowers material and transportation costs. Despite having high flexural capacity, PCHC slabs have shown relatively weak shear capacity, which is attributed to the limitations of the extrusion method that does not allow the placement of shear reinforcement in the slabs. Therefore, the shear strength of PCHC slabs is limited to concrete compression and tensile strengths. Researchers Shengxin Fan, Yao Zhang, T. N. Hang Nguyen, and Kang Hai Tan looked to develop a rational analysis method to predict the shear capacity of PCHC slabs without shear reinforcement.
The authors proposed a strut-and-tie based solution to model the mechanical response of PCHC slabs subjected to concentrated loads. Their study “Toward Consistent Prediction of Web-Shear Capacity for Hollow-Core Slabs Using Strut-and-Tie Models” in the Journal of Structural Engineering uses two types of STMs: a combined single- and two-panel STM and a multi-panel STM. Learn more about the effects of a/d ratio and compression zone depth on shear resistance predictions for PCHC slabs at https://doi.org/10.1061/(ASCE)ST.1943-541X.0003346. The abstract is below.
This paper proposes an analytical solution based on a strut-and-tie model (STM) for RC deep and short beams to predict the web-shear capacity of precast prestressed concrete hollow-core (PCHC) slabs. The proposed solution is applicable to PCHC slabs within a wide range of slab thicknesses and shear-span-to-effective-depth (a/d) ratios. Additionally, the model accounts for different cross-sectional properties of this type of slabs, geometric properties of longitudinal voids, and diameters and transmission length of prestressing strands. The proposed STM was validated against a database of 46 tests on PCHC slabs, whose capacity was also predicted using shear equations from current standards. In addition, this research investigates effects of a/d ratio and assumed depth of compression zone on shear-strength predictions for PCHC slabs. In summary, based on comparison between experimental data and analytical results, it can be concluded that the proposed STM approach is capable of providing predictions for PCHC slabs that are as reliable as current code methodologies. In addition, a direct noniterative STM approach is proposed as well to avoid challenges of iterations and refinements.
The complete paper is available in the ASCE Library at https://doi.org/10.1061/(ASCE)ST.1943-541X.0003346.