Abstract
Multi-tee-type precast concrete (PC) slab systems are widely used for the construction of modular high-load long-span buildings. However, the structural safety of the dapped end is uncertain, owing to the unanchored shear reinforcement at the construction stage. This study proposes the use of clip-type shear reinforcement at the dapped ends of multi-tee PC slabs to secure their structural performance at the construction stage. To investigate the performance of this approach, a monotonic loading test was performed on simply supported PC slabs, considering structural safety at the construction stage. The reinforcement details of the PC slab’s dapped end (with existing Z-type or proposed clip-type shear reinforcement) and the shear-to-span ratio (12.8 or 6.4) were considered as test parameters. The load–deflection relationship, failure mode, strength ratios to the predicted strength, and shear reinforcement strains were analyzed. The results showed that the tested flexural strength ratio of the PC slabs at the construction stage to the design flexural strength was 1.20–1.40. The enclosed shape and diagonal arrangement of the clip-type shear reinforcement enabled sufficient anchorage performance at the dapped end, indicating that clip-type shear reinforcement can be viable for use at the dapped ends of PC slabs under construction loads.
Highlights
Mn and Pm are the flexural moment and corresponding load, respectively, at the flexural yielding at the slab center, Vc is the shear strength of the concrete in the slab, Pv-cent is the load applied to the precast concrete (PC) slab center for a shear failure of the member, Vc-dap and Vn-dap are the shear strength at the dapped ends excluding and including the contribution of the shear reinforcement, respectively, Pv-dap(c) and Pv-dap(n) are the corresponding loads at the slab center for Vc-dap and Vn-dap, respectively, Plower is the smallest value among Pm, Pv-cent, and Pv-dap(c), Pupper is the smallest value among Pm, Pv-cent, and Pv-dap(n), and Ptest is the tested peak strength
ZS-12.8 with Z-type shear reinforcement, cracks occurred at the dapped end approximately when the load was increased to 160 kN, whereas no damage was observed at the dapped end in Specimen CS-12.8 with clip-type shear reinforcement until the end of the test
The purpose of this study was to compare the performance of the Z-type shear reinforcement and the proposed clip-type shear reinforcement installed at a PC slab’s dapped end during the construction stage
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Owing to the rising labor costs in the construction market, precast concrete (PC) systems have been increasingly used in modular high-load long-span buildings (e.g., underground parking lots, logistics centers, and large shopping malls). To improve the construction and economic efficiency by reducing the number of PC structural members, one-way PC structure systems using prestressed PC girders and PC slabs are mainly used (Figure 1a). PC slabs make up most of this one-way PC structural system. Reducing the PC slab volume has a great influence on the construction cost.
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