Experimental tests on shear capacity of naturally corroded prestressed beams

Abstract

An experimental campaign was carried out on full-scale naturally corroded prestressed concrete (PC) beams without transverse reinforcement to investigate the corrosion effects on failure modes, shear capacity, and ductility. The analyzed PC beams, structural members of a thermal power plant, were subjected for 10 years to refrigerating wetting cycles with marine water. In this paper, the experimental results of four-point bending tests, carried out at the Institute "Eduardo Torroja" in Madrid, are described. Before tests, a visual inspection was conducted to detect the damages induced by corrosion. During the tests, displacements and strains were measured by using linear variable displacement transducer (LVDT) and digital image correlation (DIC). After the tests, strands were removed from beams and cut in pieces, which were weighed to measure the mass loss. Last, it was proved that the residual life of PC beams, exposed to chloride attack, is strongly affected by corrosion, whose effects reduce the shear capacity in terms of both resistance and ductility. K E Y W O R D S digital image correlation, natural corrosion, prestressed concrete beams, shear capacity 1 | INTRODUCTION In the last years, corrosion has been considered as one of the main factors that causes detrimental effects on durability and resistance of reinforced concrete (RC) and prestressed concrete (PC) structures and infrastructures. After the recent bridge collapses occurred worldwide, such as the Ynys-y-gwas Bridge in 1985 in

Residual Flexural Capacity of Corroded Prestressed Reinforced Concrete Beams

“…The studies are grouped in order to clearly distinguish the members subjected to different corrosion processes (natural or accelerated). Among them, four articles [29][30][31][32] dealt with the behavior of beams extracted by a decommissioned bridge (DB_N); three works [33][34][35] investigated the performance of beams with reduced dimensions with respect to the previous ones and subjected to a naturally corrosive environment (B_N); eleven papers [36][37][38][39][40][41][42][43][44][45][46][47] experimentally tested the flexural performance of PRC beams damaged by artificial corrosion (B_A). • ∆R max *** ∼ = 50% for the beam with some wire cross-section loss up to 75%.…”

“…Belletti et al [34] carried out an experimental campaign on full-scale PRC beams extracted from the refrigeration tower of a thermal power plant. During their lifecycle, the beams were subjected to refrigerating wetting cycles with marine water for 10 years.…”

“…Corrosion caused longitudinal cracks, swelling, splitting phenomena and spalling of concrete cover. According to the authors of [34], the mass loss suffered by the prestressing tendons varied along each beam. To carefully report the corrosion distribution along the beams, the authors subdivided the tendons into different segments to classify them on the basis of the corrosion level (CL) observed.…”

“…Three ranges of values pertaining to the measured mass loss were observed: a low corrosion level (<2%), a medium corrosion level (2-10%) and a high corrosion level (>10%). For the sake of clarity, a diagram of the corrosion level distribution along the tested beams presented in [34] is provided in Figure 2a. Each beam is characterized by a combination of two or three corrosion levels; therefore, each element is subjected to a different deterioration distribution.…”

“…More recently, the Polcevera Viaduct in Genoa, which was in service for over 50 years, collapsed, likely due to the combined effects of corrosion and fatigue [23][24][25]. Although scientific efforts are being devoted to the assessment of the residual structural performance of prestressed RC members damaged by corrosion [26][27][28], few experimental studies have been conducted to explore the flexural behavior of corroded pretensioned reinforced concrete (PRC) beams [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]. The beams realized with the pretensioning technique, where the strands are adherent to the concrete, respond differently to the corrosion phenomenon with respect to the case of beams realized with the post-tensioning technique [38,48].…”