Shear strengthening of reinforced concrete beams by means of vertical prestressed reinforcement

Abstract

Strengthening RC elements critical to shear with prestressed transversal reinforcement can be an efficient method to increase the shear resistance of structures, allowing the development of the full flexural capacity. However, research on the performance of this technique is very scant, and methods for designing the optimum amount of prestressed transversal reinforcement and assessing the retrofitted structure have not been produced yet. Nonlinear FE models are an important tool regarding predicting the efficiency of these interventions. In this paper a shear-sensitive fibre beam formulation is extended in order to account for the effects of unbonded vertical external prestressed reinforcement in the structural response of RC beams. The model is validated with experimental tests available in literature, succeeding in capturing the gain of shear strength brought by different strengthening solutions. A parametric study is performed to find the optimal quantity of transversal reinforcement that ensures flexural failure mechanism in a beam with insufficient internal shear reinforcement. The relative simplicity of the numerical model makes it suitable for engineering practice.

Shear strengthening of concrete members with unbonded transverse reinforcement

“…Many authors have studied flexural failures of shear strengthened beams with vertical unbonded bars, but very few studied the influence on the shear failure behaviour. The effects of unbonded transverse reinforcement on the shear strength of slender beams were studied experimentally by Suntharavadivel [4], Elstner and Hognestad [5] and Lechner and Feix [6], while Ferreira, Bairán et al [7] performed finite element analyses. These authors have observed that before shear cracking, unbonded transverse reinforcement shows almost no increase in strain.…”

Shear Behavior of RC Beams Strengthened by External Vertical Prestressing Rebar

“…Lampropoulo [24] conducted a numeric study on full-scale beams strengthened with ultra-high performance fibre reinforced concrete (UHPFRC) layers and jackets, and the interface between the concrete beam and the UHPFRC was modelled using special two-dimensional elements, representing a well-roughened interface for the analysis of reinforcement technology. Ferreira et al [25] extended a shear-sensitive fibre beam model to account for the effects of unbonded vertical external prestressed reinforcement in the structural response of RC beams. Bahraq et al [10] presented a study on the shear behaviour of RC beams strengthened by jacketing the surfaces of beams using UHPC by experiments and numerical analysis.…”

Comparison of the Mechanical Properties of Different Tendon Profiles with External Prestressed Reinforcement

“…To improve the service property of bridges, many types of reinforcement and maintenance methods have been proposed [1][2][3]. External prestressing as a common method widely used in rehabilitation of existing structures [4][5][6][7][8], where prestressing tendons are placed outside of a concrete section, is an attractive technique in new construction and the strengthening of existing structures due to its ability to actively control stresses and deflections, speed of replacement, and ease of inspection under service conditions.…”