Retrofitting Of Masonry Structures Research Articles

Retrofit of Masonry Structures with Seismic Control Methods and Architectural Design Requirements

Retrofit of Masonry Structures with Seismic Control Methods and Architectural Design Requirements

Limit analysis of locally reinforced masonry arches

The use of composite on the strengthening and retrofitting of masonry structures over the past few decades has gained considerable importance. In this paper, the influence of partial reinforcement on the structural response of masonry arches is studied. An upper bound limit analysis numerical approach has been implemented to compute the collapse multipliers and reproduce the collapse mechanisms of two different study cases by increasing the cohesion value of the reinforced inter-block joints. The results thus obtained, have been compared to numerical simulation outcomes reported by other authors on the literature. The numerical approach adopted on this work, which requires few input parameters, is relatively fast in comparison to alternative numerical simulation methods, provided good agreement in terms of collapse loads and mechanisms.

Experimental procedures for the mechanical characterization of composite reinforced mortar (CRM) systems for retrofitting of masonry structures

Fiber-reinforced composites can be arranged in the form of bi-dimensional grids and employed as internal reinforcement of mortar plasters to realize composite reinforced mortar (CRM) systems. Recently, CRM were applied as externally bonded reinforcement of existing masonry members showing promising improvements of load-carrying and deformation capacities. However, since CRM systems are still in their infancy, limited research is available regarding their mechanical properties and their bond behavior with respect to masonry substrates. In this paper, a series of experimental tests are performed on a CRM system comprising a glass fiber-reinforced composite grid and a lime-based matrix. Namely, tensile tests of bare grid yarns and of CRM coupons, shear tests of grid joints, and single-lap direct shear tests of CRM-masonry joints were performed. These tests are aimed at providing a comprehensive mechanical characterization of the CRM, which results can be used to design strengthening applications with this system. Namely, the tensile properties of bare grid yarns in warp and weft direction are obtained and compared with those of CRM coupons tested following the indications of the Italian and U.S. acceptance criteria for inorganic-matrix composites. Furthermore, the grid joints are subjected to shear tests to determine if the yarns orthogonal to the applied load direction provide a contribution to the system load-carrying capacity. Finally, CRM-masonry joints are subjected to single-lap direct shear tests to study the CRM bond behavior. This work provides an insight on the behavior of CRM that can be useful to formulate reliable design procedures for these systems.

Experimental investigation of engineered cementitious composites (ECC) retrofitted masonry structures

Earthquake has proven the most damaging natural hazard in the world. So, structures in the earthquake-prone areas are need to be retrofitted prior and post of the calamity. It has been observed that most of the research solutions available focus upon reinforced concrete and steel constructions. Engineered cementitious composites (ECC) developed for economical utilization of fibres in retrofitting of masonry structures have been focused herein. The performance of beam-like masonry specimens subjected to their out-of-plane forces are experimentally and numerically investigated in this paper. Twelve beam-like specimens were cast and retrofitted with polyvinyl alcohol engineered cementitious composites (PVA-ECC) for the purpose. The casting of the retrofitting layer was done by varying percentages of PVA fibres that are 1%, 1.5% and 2% addition by the total volume of mortar. The performance of out-of-plane direction is investigated trough static two-point loading. The specimens were tested at a constant load increment of 0.1 mm per second. Work was conducted to simulate the ultimate cracking loads, maximum tension/deflection and load to deflection relationships of retrofitted and non-retrofitted specimens. Preliminary experimental data were used for numerically modelling the specimens in finite element package. Numerical results for deflection and strength were finally compared with experimental results. Experimental results revealed that the maximum load-carrying capacity with retrofitted samples increased by 11.8, 10.15 and 11.13% for 1%, 1.5% and 2% fibre addition, respectively. Simultaneously, deflection before complete collapse increases 5, 8 and 10% for 1%, 1.5% and 2% fibre additions. It can be finally said that utilization PVA-ECC as retrofitting material is an economical and easy method available.

Grout Injection Effect on the Shear Behavior of FRCM Strengthened Stone Masonry Panels

During the last decades, several seismic phenomena have shown the high vulnerability of existing stone masonry structures subject to horizontal actions. Innovative composite materials, such as Fiber Reinforced Cementitious Matrix (FRCM), can be adopted for the retrofitting of masonry structures. The use of these innovative FRCM systems is usually combined with a more traditional retrofitting technique: grout injection. It allows to restore or improve the transversal connection between wall leaves, ensuring a monolithic behavior of the structural element. The objective of this research was to analyze the effect of the quality of the grout injection on the shear response of FRCM strengthened stone masonry panels. Results from an experimental campaign, where stone masonry specimens were subject to diagonal compression tests, are therefore presented in this paper. Two samples were subject to grout injection and one of them was strengthened with Steel Reinforced Grout (SRG). Comparisons between the experimental results showed that grout injection alone, if correctly executed, could determine a significant improvement in the shear capacity of masonry panels. The application of the FRCM strengthening system could further enhance the behavior of the samples, especially influencing the failure mode. Comparisons with analytical formulations for the evaluation of the capacity of strengthened walls are also presented.

Retrofitting of Masonry Structures Considering the Architectural Perspective: A Case Study in Foca, Izmir

Masonry structures have been preferred for centuries in most of the countries across the world because they are easy to build and economical due to the use of local materials in their construction. As a result of high usage volume, masonry structures that created the architectural section of history and culture constitute an important part of the current building stock despite the developing and diversified construction techniques nowadays. The protection of these structures, which are important both in terms of their cultural values and their transfer to future generations, is of great importance in the architectural point of view. For this purpose, a masonry structure from Foca is selected. The material properties and architectural plan of the structure are determined in accordance with the original one. The structure is modelled by using a software program under seismic effects. Displacement and stress values for each acceleration record are obtained. Besides, an evaluation is made in the direction of the analysis results and it is determined according to the seismic performance of the structure. After that, the structure is retrofitted according to the current design codes and without distorting the architectural perspective. This study aims to increase the structural strength of the case building by using conventional and modern techniques for the recovery of the structure.

Some remarks on the retrofitting of masonry structures with composite materials

This paper presents some numerical simulations, aimed to the assessment of the structural performance of masonry walls, reinforced with FRP composite materials. The problem is modeled in two dimensions, and the effects of seismic loads and of foundation settlements are studied numerically. The tool we use to perform the numerical analysis, is a new minimization software developed by the authors to analyze masonry constructions, modeled as unilateral structures. The material model we adopt, no-tension with elastic–plastic (associated) behavior in compression, is path-dependent and rate-independent. The trajectory of the system, under a given loading history, is approximated as a sequence of minimizers of a path dependent form of energy, updated at each stage of the step-by-step, time-discretized procedure. The results we obtain confirm that the application of fiber reinforced composites must be done carefully, since the increase of strength in some structural elements, due to the retrofitting, may prevent the structure from developing its natural, stress relieving, kinematics.