Analysis methods for CFRP blast retrofitted reinforced concrete wall systems

Abstract

A blast retrofit technique for concrete structures using carbon fiber-reinforced polymer (CFRP) layers was investigated for use in large infrastructure systems with the overarching goal of preventing against major loss of life and considerable damage that would require extensive repair. Large-scale experiments were conducted and the retrofit behavior was investigated for application on relatively large reinforced concrete walls subjected to blast-like loadings. The experimental program utilized the University of California San Diego (UCSD) Blast Simulator. The Blast Simulator is able to induce various blast-like shock waves to the test specimen in a controlled laboratory environment. The performance of this blast retrofit was tested and then analyzed using SDOF and finite element modeling methods. A finite element model was created using LS-DYNA and utilized contact algorithms for the CFRP-concrete interface. Results and comparisons between the two analysis methods are given. Keywords: blast, CFRP, finite element, reinforced concrete, SDOF. INTRODUCTIONFiber-reinforced polymer (FRP) laminates have been shown in many studies to effectively retrofit and repair reinforced concrete structural elements [1][2][3][4][5]. The use of FRP as a retrofit is popular as it can be installed post-construction to strengthen the structure. It allows for fast installation, and has a very high stiffness and tensile strength [6,7]. Often times anchorage systems are used to mechanically restrain the FRP and to prevent delamination between the FRP and concrete, and in order to try and achieve the full tensile capacity of the FRP. Many tests have been conducted and the results are mixed and inconclusive [8][9][10].The performance of anchorage systems in retrofits is extremely important, as failure modes of the FRP are not tensile failures, but failures due to local stress concentrations by the anchors and delamination of the FRP to the concrete [1,[11][12][13][14]. These failures are much more sudden and less ductile than a tensile strength failure of the FRP, which emphasizes the need to achieve an anchoring system that allows the FRP to achieve full tensile failure.

Influence of EBR on the structural resistance of RC slabs under quasi-static and blast loading: Experimental testing and numerical analysis

“…In a more recent study, Pezzola et al [13] developed a finite element model of an RC beam retrofitted with FRP. The model was detailed with special attention to the concrete-to-FRP interface, where a tiebreak contact was used to simulate the interfacial behaviour of the epoxy bond.…”

Experimental and numerical study on CFRP strip strengthened clay brick masonry walls subjected to vented gas explosions

“…Alsayed et al [20] conducted field blast tests and numerical study on the GFRP sheet strengthened infill CMU masonry walls under C4 charge explosions by using ANSYS/AUTODYN. Explicit boundary modelling was used to simulate the interaction with supports, which may result in membrane effect and enhance the resistance of structures [18,20,21]. In order to improve the computational efficiency, the homogenized material model was employed for masonry walls and the composites were simulated as shell elements to reduce element number and the discrepancy between element sizes [20].…”

Load-Displacement Assessment of One-Way Reinforced Concrete (RC) Slabs Externally Strengthened Using CFRP Strips under Blast Loads

“…Their results presented a good prediction of the failure mode when compared to experimental results. Pezzola et al [2] studied the blast performance of CFRP retrofitted RC walls, where the composite material was included in the analysis assuming it behaves like tensile reinforcement. The solution was controlled by a strain limit representation of the FRP debonding.…”