Abstract
Shear strength of precast concrete ribbed slabs reinforced with electro-welded lattice girders of variable height is experimentally verified. Technical justification is given for the use of high latticework in the reinforcement of precast lightweight double-tee ribbed slabs and precast reinforced concrete slabs 30 cm in thickness. It was established that the contribution of concrete to shear strength was always higher than the expected values according to Spanish standards. Furthermore, as low lattice ribbed slabs exhibited lower ultimate shear strength values than the ones expected based on the standards, the need arose to provide an adequate height of lattices in ribbed slabs to ensure anchorage of the compressed area in order to develop the strut-and-tie mechanisms. Consequently, lattice girders with approximately 80% of specimen height are highly recommended in reinforced concrete ribbed slabs, when the length of lattice chords is 20 cm.
Highlights
Resistance of Reinforced Concrete (RC) components to shear force is a topic that has aroused great interest since the end of the nineteenth century [1]
The general pattern of all graphs involved a peak corresponding to the shear cracking that propagated from one face of the test specimen to the other, and the load fell abruptly as the lattice reinforcement rods were broken
In both specimens with double lattice (15 and 24 cm specimens), the shear strength of concrete obtained in the test (TVcu) is by approximately three times higher than the one expected theoretically (EVcu)
Summary
Resistance of Reinforced Concrete (RC) components to shear force is a topic that has aroused great interest since the end of the nineteenth century [1]. Recent investigations have resulted in the development of numerical models that are capable of estimating strength mechanisms under tangential forces and, shear forces occurring in RC structures, the formulas for manual calculation of shear stress forces still entail a large empirical content. These highly non-linear forces are characterized by a strong multi-axial tensile deformation mechanism [6,7,8,9,10,11,12] that produces oblique cracking non-parallel to the plane of the main section. The following is specified in Article 44.2.3.4.1 of the Spanish RC standard with regard to the longitudinal distance between transverse reinforcement, st [18]: st ≤ 0,75 · d · (1 + cota) ≤ 600 mm if Vrd ≤ 1/5 · Vu1
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