Shear Behavior of RC Beams Strengthened by External Vertical Prestressing Rebar

Abstract

Shear design is an important part of structural design. External vertical prestressing rebars (EVPRs) have proven to be an effective way to enhance structural shear resistance. The objectives of this study are to simulate EVPR strengthening of concrete beams using a nonlinear three-dimensional finite element model and to explore its shear enhancement features under different EVPR stirrup ratios, vertical compressive stress degrees, and optimal arrangements of EVPRs. Concrete, common reinforced bars, and EVPRs use solid, steel, and truss elements, respectively. In addition, the total strain crack model is used to characterise the concrete. The results indicate that the EVPR stirrup ratio can reduce the diagonal crack width and improve the shear capacity, and the vertical compressive stress degree can effectively control crack development in the initial loading. A “small-area EVPR dense arrangement” is the recommended EVPR configuration method. Both experiments and numerical analyses show that EVPRs can effectively improve the shear performance of concrete.

Cyclic Shear Performance of Reinforced Concrete Columns Strengthened by External Steel Rods

“…A prestress of about 4 kN was introduced to the external steel rods immediately before the loading by rotating the reverse-threaded couplers with a torque wrench. According to a previous report [22], prestressing effectively suppresses initial cracking. However, introducing a prestress to external reinforcements over a certain level can cause a decrease in the ductility after the maximum load while increasing the initial stiffness of the columns [36].…”

“…The transverse confinement techniques that are widely applied to the reinforcement and retrofitting of RC columns with insufficient seismic capacity include external steel jacketing [5][6][7][8][9][10][11], fiber-reinforced plastic (FRP) composite wrapping [12][13][14][15][16][17], external posttensioning or prestressing [4,[18][19][20][21][22], and bonded steel plating [23][24][25][26][27][28]. These reinforcement methods should improve the RC columns' seismic capacity and provide precision, simplicity, and economic feasibility in construction, as well as convenience in maintenance.…”

“…However, when the spacing of the strand stirrup was increased, the confinement force on the concrete core was not significantly increased, even if the prestressing level was increased. Li et al [22] conducted an experimental and analytical study on the shear behavior of the RC beams reinforced with External Vertical Prestressing Rebars (EVPR). The parametric study based on the experimental results showed that the vertical compressive stress increase effectively controls the cracking in the initial loading stage, but the increase in the EVPR stirrup ratio effectively improves the shear resistance by decreasing the width of the diagonal cracks.…”

Strengthening Shear Resistance of Beams without Web Reinforcements Using Vertical Prestressed Steel Bars

“…A shear-sensitive ber beam formulation proposed by Ferreira et al [39] was extended to account for the e ects of unbonded vertical external prestressed reinforcement on the structural response of RC beams. Li et al [40] used the total strain crack model of concrete and established a nonlinear three-dimensional nite element analysis to model shear strength in Midas/FEA, in which the parameters included the vertical compressive stress degree and VPSB stirrup ratio, and the optimal arrangement of VPSBs were discussed. Fiset et al [41] investigated the behaviour of thick concrete members strengthened in shear with unbonded VPSBs, as well as performed loading tests and numerical analysis.…”

Shear-flexural cracking strength of RC beams with external vertical prestressing rebars: Theoretical investigation and numerical simulation

“…Recently, it has been found that increasing the EVPR stirrup ratio can reduce the width of shear cracks and improve the shear resistance by numerical simulation. The configuration method “small-area EVPR dense arrangement” was recommended (Li et al, 2021).…”