Anchorage failure and shear design of hollow‐core slabs

Abstract

A number of studies in recent years have attempted to understand and calculate the shear strength of hollow‐core slabs, but no consensus has been reached on this issue. The current design methods for hollow‐core shear resistance are derived from experimental results and elastic theories that are not usually directly related to the behaviour at the ultimate limit state. Moreover, some manuals on this subject do not discuss anchorage failures, which although not common in this type of slab, may influence the shear strength. This paper considers the anchorage failure of strands using the concepts of Eurocode 2 and presents an analytical methodology for shear design based on the modified compression field theory (MCFT). Furthermore, the safety concepts of Eurocode 2 are properly presented and evaluated using the experimental data available in the literature. The proposed methodology is proved to be accurate and is simple enough for use in design. Comparisons with CSA A23.3 and Eurocode 2 are also shown.

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

“…Recently, Sgambi et al [1] have shown the mismatch between EN 1168 [34] and numerical simulations that were based on classical principles of nonlinear fracture mechanics [36][37][38][39][40][41][42]. Similarly, Araujo et al [30] have performed nonlinear FE modeling on PPHC slabs to show the inaccuracy of CSA [43], when applied for these elements, and to propose an alternative analytical design methodology, based on modified compression field theory (MCFT) [44] and concepts of Eurocode 2 (EC2) [33].…”

“…The accuracy of the approach increases, as the nominal depth increases: the mismatch with experimental results is 38% for 265 mm thick units, while it approximately ranges from 15% to 25% for the other depths considered. Being based on simplified modified compression field theory [49] which treats concrete as a diagonally shear cracked material and evaluates the aggregate interlocking as a function of the average tensile strength, CSA [43] provides estimates safer than EC2 [33], EN 1168 [34] and ACI [32] for any slab depth and hollow core shape analyzed, explicitly representing a sort of robust, sometimes overconservative, lower bound applicable for design purposes [28][29][30]. Nevertheless, CSA [43] was shown to have the highest standard deviation of the four analytical approaches, for any slab depth considered (see Table 1).…”

“…In the last three decades, PPHC units have been extensively studied, experimentally [2,3,[26][27][28] and numerically [1,7,25,29,30], to understand and calculate the shear strength of these members, but no consensus has been reached on this issue [30,31]. In addition, the current design methods for shear resistance are derived from experimental results [32] and elastic theories [33,34] that are not usually directly related to the behavior at the ultimate limit state, which may be affected by many sources of nonlinearity and complex thermo-hygro-mechanical effects [35].…”

Shear load testing of damaged hollow‐core slabs

“…Under single loads near the support, there is also a danger that shear cracks develop when the principal tensile stress reaches the tensile strength of the concrete. These shear cracks rapidly spread into the compression zone and to the anchorage and thus cause a sudden shear failure . In experimental investigations, shear compression failures have also been observed.…”

“…Considering all the aforementioned safety factors for the transfer of the test results, the target test load was V tar = 1.5*1.8*V Ed = 123.80 kN. The design value of the shear resistance was V Rd = 66.80 kN and the most probable shear load at failure without any safety factors and with mean values of the material strengths was V R,calc = 163.75 kN …”