Abstract
Abstract There are many theories and empirical formulas for estimating the shear strength of reinforced concrete structures without transverse reinforcement. The security factor of any reinforced concrete structure, against a possible collapse, is that it does not depend on the tensile strength of the concrete and the formation of any collapse is ductile, thus giving advance warning. The cracking from tensile stress can cause breakage of the concrete and should be avoided at all cost, with the intent that any such breakage does not incur any type of failure within the structure. In the present research study, experiments were performed in order to analyze the complementary mechanisms of the shear strength of lattice beams of reinforced concrete frames without transverse reinforcement. The experimental program entails the testing of eight frames that were subjected to a simple bending process. Two concrete resistance classes for analyzing compressive strength were considered on the construction of frames, 20 MPa and 40 MPa. To resist the bending stresses, the beams of the frames are designed in domain 3 of the ultimate limit states. Different rates and diameters of longitudinal reinforcement were used, 1.32% and 1.55% with 12.5 mm diameter and 16.0 mm in longitudinal tensile reinforcement. From the obtained results, an analysis was made of the criteria already proposed for defining the norms pertinent to the portion of relevant contribution for the shear resistance mechanisms of concrete without the use of transverse reinforcement and the influence of the concrete resistance and longitudinal reinforcement rates established in the experimental numerical results.
Highlights
Ruptures in reinforced concrete beams are subject to the characteristics of the constituent material, concrete and steel, the dimensions of the element, the type of load and the design and details of the reinforcing steel, where a desired requirement is that it be of a ductile type
The ABNT NBR 6118:2014 [2] states that the resistance of a beam to shear, shear strength, is usually considered from two portions, Vc is the portion that is resisted by the concrete and complementary mechanisms on the truss, that contribute to the concrete and Vsw the portion resisted by the transverse reinforcement
In regards to shear strength in beams without transverse reinforcement, there does not exist a consensus in the available codes and norms concerning the parameters and phenomena that govern the problem of shear, which in many cases are based on empirical formulas [6,7,8]
Summary
Ruptures in reinforced concrete beams are subject to the characteristics of the constituent material, concrete and steel, the dimensions of the element, the type of load and the design and details of the reinforcing steel, where a desired requirement is that it be of a ductile type. In regards to shear strength in beams without transverse reinforcement, there does not exist a consensus in the available codes and norms concerning the parameters and phenomena that govern the problem of shear, which in many cases are based on empirical formulas [6,7,8]. In the case of rectangular beams, with the format of an inclined crack, the shear stress transferred through the various mechanisms is proportionally 20% to 40% for the non-cracked concrete compression zone, 33% to 50% for the aggregate mesh and 15% for the pin effect, KIM and PARK [10]. Besides the meshing of aggregates, other shear stress transference mechanisms were cited in Ruiz et al [8], such as the resistance to concrete traction, the arc effect and the pin effect. In Bentz [12], shear strength is explained through a consideration of aggregate meshing in accordance with Walraven [9]
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