Experimental bond behaviour of GFRP and masonry bricks under impulsive loading

Fibre Reinforced Polymers have become a popular material for strengthening of masonry structures. The performance of this technique is strongly dependent on the bond between the FRP and the substrate. Understanding the strain rate effect on these materials and strengthening techniques is important for proper design and proper modelling of these systems under impacts or blast loads. This work aims to study the behaviour of the bond between GFRP and brick at different strain rates. A Drop Weight Impact Machine specially developed for pull-off tests (single shear tests) is used with different masses and different heights introducing different deformation rates. The strain rate effect on the failure mode, shear capacity and effective bond length is determined from the experimental results. Empirical relations of dynamic increase factors (DIF) for these materials and techniques are also presented.This work was performed under Project CH-SECURE (PTDC/EMC/120118/2010) funded by the Portuguese Foundation of Science and Technology – FCT. The authors acknowledge the support. The first author also acknowledges the support from his PhD FCT grant with the reference SFRH/BD/45436/2008

Experimental Studies on Bond Performance of BFRP bars reinforced Coral Aggregate Concrete

As part of this study, has been developed a numerical method which allows to establish abacuses connecting the normal force with bending moment for a circular section and therefore to predict the rupture of this type of section. This may be for reinforced concrete (traditional steel) or concrete reinforced with steel fibers. The numerical simulation was performed in nonlinear elasticity up to exhaustion of the bearing capacity of the section. The rupture modes considered occur by plasticization of the steel or rupture of the concrete (under compressive stresses or tensile stresses). Regarding the fiber-reinforced concrete, the rupture occurs, usually, by tearing of the fibers. The behavior laws of the different materials (concrete and steel) correspond to the real behavior. The influence of several parameters was investigated, namely; diameter of the section, concrete strength, type of steel, percentage of reinforcement and contribution of concrete in tension between two successive cracks of bending. A comparison was made with the behavior of a section considering the conventional diagrams of materials; provided by the BAEL rules. A second comparative study was performed for fibers reinforced section

Damage evaluation of ultra-high performance concrete columns after blast loads

As emerging advanced construction material, ultra-high performance concretes have seen increasing field applications over the past two decades to take advantages of their ultra-high mechanical strength and durability; yet the systematic study on its dynamic behaviour under impact and blast loads is not commonly seen. This article presents an experimental and numerical study on the static and dynamic behaviour of an existing ultra-high performance concrete material. Experimental study on its flexural behaviour under static loads is conducted and an inverse study is carried out to derive its uniaxial tensile constitutive law. The derived relationship is used in the material model in hydro-code LS-DYNA together with dynamic material properties to study ultra-high performance concrete columns under blast loads. The residual loading capacity of the column is studied and pressure–impulse diagrams for assessing the ultra-high performance concrete column damage under blast loads are proposed. Parametric study on effects of ultra-high performance concrete strength, column height, cross-section size and reinforcement ratio is performed and analytical equations are proposed for generating pressure–impulse diagrams for generic ultra-high performance concrete columns

Failure and impact resistance analysis of plain and fiber-reinforced-polymer confined concrete cylinders under axial impact loads

This study conducts an experimental and numerical investigation on the failure and impact resistance of plain and fiber-reinforced polymer-confined concrete. The impact resistance of concrete cylinders wrapped with different types of fibers including carbon fiber and glass fiber is examined. Drop-weight tests are utilized to conduct the impact tests while the numerical simulation is conducted using LS-DYNA. The experimental and numerical results have proved that fiber-reinforced polymer can be efficiently used to improve the impact resistance of concrete cylinders. In general, fiber-reinforced polymer ruptures at a lower strain than those in static tests and the rupture strain of glass fiber is much higher than that of carbon fiber. The findings in the experimental tests are confirmed by the numerical results. Glass fiber, therefore, exhibits a much better performance than carbon fiber. It is recommended to use glass fiber to enhance the impact resistance of concrete structures strengthened with fiber-reinforced polymer. In addition, the stress evolution of the specimens is analyzed to investigate the failure mechanism