A. Si Larbi

Mechanical in-plane behaviour of masonry walls reinforced by composite materials: Experimental and analytical approaches

Masonry is a traditional building system in most countries of the world, including France. However, in recent decades, earthquakes have caused significant damage to masonry structures. The possibility of using textile-reinforced concrete or fibre-reinforced polymers to strengthen masonry structures has been recently assessed. This article addresses the effectiveness of externally bonded composite materials, particularly those based on newly developed cementitious matrices, to strengthen masonry structures. Experimental tests were performed in a previous study on six masonry walls, five of which were strengthened on both sides with either textile-reinforced concrete or fibre-reinforced polymers. This experimental campaign has been supplemented to determine the mechanical properties of the materials involved in design models, and it is used to check the potential of analytical models to predict lateral strength. This study identifies the interests and the restrictions governing the use of traditional empirical design approaches (employed for fibre-reinforced polymer-strengthened walls) when next-generation textile-reinforced concrete composites are used as strengthening materials. Adjustments taking into account the specificities of textile-reinforced concrete behaviour have been introduced, and their impact on the relevance of the models has been quantified.

In-Plane Behavior of Seismically Damaged Clay Masonry Walls Repaired with External TRC

Recently earthquakes with quite high magnitude have continuously occurred in the Vietnam territory which cause the dangerous to masonry buildings. The stringent seismic design requirements for masonry structure will be therefore considered in the construction field of Vietnam. The paper, which an exploratory study, focuses on the behavior of clay solid brick masonry walls, especially walls repaired on both sides with TRC (Textile Reinforced Concrete) composite under cyclic in-plane loading condition. This work is the first step towards defining the potentiality including both technical and scientific aspects of using TRC in seismic strengthening and repairing the masonry structure in Vietnam. Thus, an experimental program has been performed at laboratory scale. Two walls have been submitted for cyclic shear-compression tests in-plane solicitation: the first one (unreinforced wall) is tested to the pre-defined damage level and failure mode, and then repaired with TRC strips as the second one. A comparative study on global behavior and on mechanism of failure is performed and, although the limited number tests, highlights that, thanks to the contribution of TRC strips, the wall’s residual strength and deformation ability are upgraded. In addition, compared to the unreinforced specimen, the repaired one is more stable strength and stiffness change at later stages. Furthermore, the TRC strips help to reduce the risk of out-of plane failure. However, it seems to be that, the low reinforcement ratio and (or) the relatively unsuitable formulation of mortar, especially the grain size, in TRC limit its efficiency in reinforcing solutions.

Optimization of Quasi-isotropic Formulation of Fiber-Cement Laminates: Polar Method and Experimental Validation

The development of Textile Reinforced Concrete (TRC) requires the development of design methods. As cement based composites present anisotropic behavior at different levels, we suggest to consider the initial elastic stage of the elementary layer behavior law in tension, compression and shear, limited by a crack opening threshold. Then, we apply the polar method, allowing to optimize a multilayer stacking sequence in order to obtain an overall quasi-isotropic behavior of a composite plate.

Assessment of the Long-term Shear Behavior of Epoxy Polymer Lap Joint Used to Bond Steel and Concrete Composite Structure

This article presents the results of an experimental study concerning the evolution in time of the shear modulus of an epoxy resin used for bonding together steel girders and concrete slabs. For this purpose, two experimental methodologies are set up. The first one, based on mechanical spectroscopy measurements allows to assess a rheological model adapted to the polymer resin (Zener’s model). In this case, the analysis of the shear behavior of the material itself is carried out. The second one, based on the time-temperature equivalency principle, analyzes the long-term shear behavior of epoxy joints under real loading conditions: double shear tests are performed on steel-concrete lap joint bonded together with an epoxy adhesive. The results of the two procedures permit to assess the evolution of the shear modulus for a time period of 109 s (~50 years). Analyzing only the intrinsic behavior of the material is insufficient for this time range, because additional mechanisms occur at the concrete-epoxy interface.