Experimental study of blast response of RC slabs with externally bonded reinforcement

The present paper discusses experimental work on the efficiency of externally bonded reinforcement (EBR) on reinforced concrete (RC) slabs under blast loads using an explosive driven shock tube (EDST). This study focuses on four tests which have been performed on simply supported RC slabs retrofitted with carbon fiber reinforced polymer (CFRP) strips and subjected to explosions for the same pressure and impulse. Pressure transducers are fixed at the end of the tube to measure the pressure of each experiment. Maximum deflection and strain distribution in the concrete and CFRP strips are recorded using digital image correlation (DIC) measurements. Due the explosion, the RC slabs are submitted to a dynamic vibration in both directions and during the first inbound displacement phase, the kinetic energy of the retrofitted specimen is stored as elastic strain energy in CFRP strips. All this elastic strain energy stored in FRP strips is violently released as kinetic energy during the rebound phase of the slab. The results indicate that EBR increases significantly the flexural capacity and the stiffness of RC slabs under blast loads

Blast response of RC slabs with externally bonded reinforcement under two independent explosions

The use of carbon fiber reinforced polymer (CFRP) as externally bonded reinforcement (EBR) for strengthening reinforced concrete (RC) structures that are loaded by a blast wave is confirmed as an efficient solution. This in addition to other advantages of CFRP such as high tensile strength, light weight and durability. This paper aims to investigate the blast response of reinforced concrete (RC) slabs retrofitted with carbon fiber reinforced polymer (CFRP) as externally bonded reinforcement (EBR) under two independent explosions. In order to achieve this objective, four simply supported slabs were tested using an explosive driven shock tube (EDST) to generate a reflected pressure equal to 3 MPa in the first explosion and a reflected pressure equal to 7.5 MPa in the second explosion. Digital image correlation (DIC) is used to measure the strain evolution in the concrete and the CFRP strips during the first explosion. The slabs retrofitted with increasing the quantity of fibers show a reduction in the residual deflection after two independent explosions. The results show that for the first explosion, EBR increases the flexural response and the stiffness of the RC slabs. In the second explosion, a total debonding of the CFRP strips occurs and initiates from the midspan of the slabs toward the supports. When the total debonding of the CFRP strips occurs, the strain distribution in the steel rebars are the same for all slabs regardless of the quantity of applied EBR

Numerical analysis of retrofitted RC slabs with CFRP strips under blast loading

This paper investigates the effectiveness of carbon fiber reinforced polymer (CFRP) as externally bonded reinforcement (EBR) to improve the flexural resistance of reinforced concrete (RC) slabs under blast loads. Three simply supported RC slabs are subjected to blast loading using an explosive driven shock tube (EDST). The obtained experimental results of the RC slabs without and with EBR are presented and discussed with the aim of evaluating the influence of EBR on the blast response of the RC slabs. A numerical analysis is carried out using the finite element software LS-DYNA to complement the experimental results. The bond interface between CFRP strips and concrete is simulated with a specific contact algorithm including the normal and shear stresses at the interface with failure criteria. The numerical analysis shows good agreement with the experimental results for the maximum deflection at the mid span of the slabs and good prediction of the distribution of cracks. CFRP strips as EBR increase the flexural capacity and the stiffness of the slabs. A reduction in the blast induced maximum deflection is recorded for the slabs retrofitted with CFRP strips

New technique to protect RC slabs against explosions using CFRP as externally bonded reinforcement

In recent years, numerous explosions related to industrial accidents and terrorist attacks causing loss of life and severe damage to infrastructures have occurred all over the world. However, existing reinforced concrete (RC) structures are not designed to resist blast loads and could collapse after the incident. As a consequence, the emerging challenge of critical infrastructure protection has been recognized and nowadays there is a desire to upgrade the blast resistance of existing RC structures. The present paper provides an experimental and numerical analysis of the efficiency of using carbon fiber reinforced polymer (CFRP) as externally bonded reinforcement (EBR) on RC slabs under blast loads to increase the flexural resistance of the structure. Moreover, the effect of the propagation of the blast wave within the retrofitted specimens and how it affects the bond interface between the CFRP strip and concrete during the blast loading is discussed

Numerical analysis of debonding between CFRP strips and concrete in shear tests under static and blast loads

The present paper deals with the finite element (FE) analysis of the bond slip between concrete and carbon fiber reinforced polymer (CFRP) strips in a single bond shear test under static loads and in a double bond shear test under blast loading. A plastic damage material model and an elastic material model are used to model the concrete prism and the unidirectional CFRP strip, respectively. The bond interface between concrete and CFRP strip is simulated using a cohesive bond model. For the static loads, the numerical model is validated with experimental tests available in the literature. The debonding failure mode, the delamination loads and the strain distribution along the CFRP strip are predicted. The numerical results show a good agreement with the experimental data using the cohesive bond model. For the blast loads, the validated cohesive bond model is used. A parametric study with respect to the width and the length of the CFRP is conducted. Moreover, the reflected pressure and impulse are varied to highlight the effect of the propagation of the blast wave in the debonding process under blast loads

Blast response of RC slabs with externally bonded reinforcement : experimental and analytical verification

The present paper provides an analysis of the efficiency of externally bonded reinforcement (EBR) on reinforced concrete (RC) slabs under blast loads. Five simply supported slabs with a span of 2m are tested under explosive charge. One of the slabs is used as a reference specimen and the remaining slabs were strengthened with different ratios of carbon fiber reinforced polymer (CFRP). An analytical analysis is carried out using the simplified singledegree- of-freedom (SDOF) approach to predict the maximum deflection at midspan. Digital image correlation (DIC) is used to measure the maximum deflection at the midspan of the slab and the strain distribution in the concrete and the EBR. Given the challenge to combine these displacement field measurements with blast, an explosive driven shock tube method has been adopted in this study. The results indicate that CFRP as EBR increases significantly the flexural capacity and the stiffness of RC slabs under blast loads. The impact of the blast wave on the RC slabs generates high strains in concrete, steel reinforcement and CFRP strips. Good correspondence in the prediction of the maximum deflection between the experimental and the analytical results, is obtained, showing that analytical analysis by means of the simplified SDOF approach leads to a reliable prediction

Numerical modeling of brittle mineral foam in a sacrificial cladding under blast loading

Cellular materials, such as aluminum foams, have proven to be excellent energy absorbents. They can be used as crushable core in sacrificial cladding (SC) for blast load mitigation. In this study, the blast absorption capacity of a brittle mineral foam-based SC is investigated through finite element modeling using the LS-DYNA software. The experimental set-up used consists of a rigid steel frame with a square cavity of 300 mm x 300 mm in the center The structure to be protected is simulated by a thin aluminum plate clamped into the rigid steel frame. The blast load is generated by 20 g of C4 high explosive set at a distance of 250 mm from the center of the plate. The blast absorption capacity of the considered SC is evaluated by comparing the maximum out-of-plane displacement of the center of the plate with and without the protective brittle mineral foam. The presence of the brittle mineral foam reduces the maximum out-of-plane displacement of the center of the plate at least by a factor of two. The brittle mineral foam is modeled both in solid elements and smoothed-particle hydrodynamics (SPH) by using Fu Chang's constitutive material law based exclusively on the results of quasi-static compression tests of the foam and a phenomenological relationship between stress, strain and strain rate. The SPH model predicts the maximum out-of-plane displacement of the center of the aluminum plate with an average relative error of 5% with respect to the experimental values

Reinforced concrete beam-column inverted knee joint behaviour after ground corner column loss-numerical analysis

Beam-column joints are critical component in the load path of reinforced concrete (RC) frames, due to their role in transferring loads among different RC frame components. The loss of a ground corner column in a RC frame turns an exterior joint into an inverted knee joint and recent code provisions for exterior joints are not sufficient to knee joints because of reinforcement defects in terms of joint vertical stirrups and improper column bar anchorage. This paper investigates numerically the behaviour of these joints under a closing moment using nonlinear finite element (FE) analysis with LS-DYNA. Beam’s bar anchorage type and joint vertical stirrups are the main parameters considered next to concrete compressive strength, longitudinal reinforcement ratio and lateral beam effect. This study indicates that, anchorage beam’s bar with U shaped produces better behaviour than 90° standard hooks or headed ends. Contribution of joint vertical stirrups is more influential with headed bars anchorage. Increasing concrete compressive strength and beam reinforcement ratio improve joint ultimate capacity. The presence of lateral beams reduces the rate of concrete degradation in the joint after reaching ultimate capacity and increases joint carrying capacity.SCOPUS: ar.jinfo:eu-repo/semantics/publishe