Effect of CFRP Shear Strengthening on the Flexural Performance of the RC Specimen under Unequal Impact Loading

Abstract

Strengthening with externally bonded CFRP reinforcement is widely used in structural reinforcement and attractive to stakeholders and engineers because of ease and speed of construction, corrosion resistance, lightweight, high strength, and versatility stiffness which can be oriented according to the need. Numerous research studies were carried out to explore RC beams’ flexural and shear performance when subjected to dynamic impact loading. The results were auspicious in using such a technique of strengthening. Regular square section reinforced concrete frame members strengthened by CFRP material is taken as the research object. However, little attention to the impact behavior of CFRP-shear-strengthened square reinforced concrete (RC) specimens has been paid. The dynamic response of CFRP to reinforced concrete members under unequal cross-impact is discussed. This paper investigates the effectiveness of CFRP strengthening on the square RC specimen in preventing shear failure and evaluation of the flexural performance of the strengthened specimen under the impact load. The drop hammer impact test is firstly conducted on RC specimens with and without CFRP strengthening. The results show that using CFRP to strengthen the RC specimen in shear is very effective at preventing shear failure and leading the specimen’s response to flexural domination. This result is also the motivation for developing a numerical model supported by experimental tests to study the flexural performance of strengthened RC specimens. It is found that the strengthened specimen is prone to exhibit pure bending deformation under the impact load in terms of dynamic amplification factor (DAF) for section moment. Then, an extensive parameter study is carried out to evaluate further the influence of impact velocity, reinforcement ratio, and concrete strength on the flexural performance of the strengthened specimen and CFRP layers. Such a holistic study may provide preliminary research regarding the use of CFRP to strengthen RC specimens in shear under impact loads and will enhance the current state of knowledge in this area; also, the optimal value of the CFRP reinforcement layer was proposed.

Dynamic simulation of CFRP‐shear strengthening on existing square RC members under unequal lateral impact loading

“…The initial impact velocity of the impactor is adjusted from 1.0–6.0 m/s while the impact mass is kept constant at 270 kg. This part uses an RC specimen (FH2) from previous research 62 to deepen the debate and make it more credible. Figure 22 illustrates the lateral displacement responses with respect to impact duration.…”

Numerical study on existing RC circular section members under unequal impact collision

“…On the other hand, the remainder of the mesh is a lot more sparsely distributed. The drop hammer deforms very little during the impact, which is close to a rigid body, so it is considered a rigid cube in the finite element simulation 1 , 3 , 36 , 51 , with a cross-sectional size of 80 mm × 30 mm, consistent with the cross-sectional size of the impact body in the test. As a result of this treatment, the analysis time required for the drop hammer contact to RC collision simulations can be reduced by 43%.…”

“…The strength, deformation, elasticity, and confining effect are influenced due to the changes in the cross-section, reinforcement, and the width-to-thickness ratio of the members under the lateral impact loads 1 – 4 . There has been some investigation into these factors in the previous literature.…”

“…While the reinforced concrete members usually produce large deflection deformation at the impact point with unequal impact load position, and the flexural crack occurs with the steel rebar 1 – 3 , 24 , 25 .…”

Dynamic Equilibrium of CFRP-RC Square Elements under Unequal Lateral Impact

“…Additionally, other properties for CFRP (Tokyo, Japan) are shown in Table 2. After the epoxy resin was impregnated and cured, the CFRP sheet was tested in three directions by a pull-up tester [21]. The epoxy adhesive used in the test was Araldite XH 180 (Tokyo, Japan), used for improving the properties of the concrete surface, which is in direct contact with the carbon fiber system.…”