The Combined Strengthening Effect of CFRP Wrapping and NSM CFRP Laminates on the Flexural Behavior of Post-Tensioning Concrete Girders Subjected to Partially Strand Damage

Abstract

The studies on unbonded post-tensioned concrete members strengthened with Carbon Fiber Reinforced Polymers (CFRPs) are limited and the effect of strengthening on the strain of unbonded pre-stressed steel is not well characterized. Estimating the flexural capacity of unbound post-tensioned members using the design methodology specified in the design guidelines for FRP strengthening techniques of bonded post-tensioned members does not provide a reliable evaluation. This study investigates the behavior of unbonded post-tensioned concrete members with partial strand damage (14.3% and 28.6% damage) and strengthened with CFRP laminates using a near-surface mounted technique with and without U-wrap anchorages. The experimental results showed that the use of CFRP laminates significantly affects strand strain, especially with the use of anchors. The CFRP reinforcement affected flexural strength, crack width, and midspan deflection. However, the flexural stiffness of strengthened members during the serviceability phases is critical as strand damage ratios increase. In comparison with the nondamaged girder, the NSM-CFRP laminates enhanced the flexural capacity by 11% and 7.7% corresponding to strand damage of 14.3% and 28.6% respectively. Additionally, semiempirical equations were proposed to predict the actual strain of unbonded strands whilst considering the effects of FRP laminates. The suggested equations are simple to apply and provide accurate predictions with little variance.

Reinforced Concrete Columns Insulated by Different Gypsum Layers Exposed to 900°C One Side Fire Flame

“…A 24-channel temperature-capable data logger was used to collect the data. The two ends of the column specimens were connected by two steel bars that were welded to them, and the other two sides were fastened with a steel plate with holes cut for one steel bar to allow the other to move freely [12][13][14]. The second dial gauge was positioned using the same process on the bottom side.…”

Effect of Double Interior Stiffeners on the Flexural Behavior of Concrete Filled Steel Tube Composite Box Girders

“…However, the flexural stiffness of the strengthened members during the serviceability phases is critical as strand damage ratios increase. In comparison with the non-damaged girder, the NSM-CFRP laminates enhanced the flexural capacity by 11% and 7.7%, corresponding to strand damage of 14.3% and 28.6%, respectively [18].…”

Investigation of the Experimental Shear Resistance of RC T-beams after Strengthening with Carbon Fiber-Reinforced Polymer (CFRP) Bars

“…During the recent years, there has been a growing interest in the use of Carbon Fiber Reinforced Polymer (CFRP) composites for reinforcing concrete parts to rehabilitate infrastructure. The use of CFRP reinforcement demonstrates a diverse array of applications, entailing the construction of innovative structures and the rehabilitation of pre-existing ones [1][2][3][4][5][6][7]. The shear strength of Reinforced Concrete (RC) beams is influenced by many factors [8][9][10].…”