Shear Strength Of Masonry Walls Research Articles

Experimental characterization of the in-plane shear strength of unreinforced masonry walls with damp-proof course and thermal break layer

Due to the highly demanding energy standards in Europe and challenging weather conditions, thermal break elements, such as aerated autoclaved concrete (AAC), have become increasingly popular in modern day residential buildings made of masonry cavity walls. Furthermore, a damp-proof course (DPC) layer is also used on top of the thermal break element to prevent water seeping and eventual entrapment due to capillary action. The presence of an AAC layer and of a DPC can have an adverse effect on the in-plane shear strength of a masonry wall, although information on this is barely available in the existing literature. This study aims at filling that knowledge gap through experimental investigations on traditional masonry walls and composite masonry walls, i.e. with an AAC and a DPC layer. The in-plane shear behaviour is compared between both types of wall specimens on the base of load-displacement curves and observation of failure modes. The capacity of analytical design approaches in predicting the test results has also been assessed. For the tested configurations, it can be concluded that the presence of AAC and DPC makes the failure mode switch from diagonal shear sliding combined with flexural toe crushing to horizontal shear sliding with crushing localized in the AAC layer, associated to a drop of the resistance by 6 to 9% depending on the type of clay units and mortar. The proposed analytical method, derived from EN 1996-1-1, is providing a safe estimate of the test results with a similar level of accuracy for traditional and composite configurations (predicted values in the range of 75 to 86% of the measured values). Finally, the influence of the definition of the compressed length and of the shear span ratio are shortly discussed.

Experimental investigation of FRCM under shear loading

Fabric Reinforced Cementitious Matrix (FRCM) can be used to improve the shear strength of masonry walls. The contribution of the FRCM is evaluated, accordingly to existing standard, taking into account the FRCM-to-substrate bond strength and the tensile strength of bare fabrics, neglecting the mortar matrix. Nevertheless, to date, there are no experimental tests that provide the actual shear capacity of the FRCM alone and not bonded to the substrate. To this scope, a four-hinge articulated steel frame was designed to investigate the shear behaviour of small-scale square specimens, as well as the mechanism of shear stress transfer between the fabric and the mortar. This paper presents the outcomes of shear tests performed on four FRCM composites, comprising of two basalt fabrics embedded in either lime- or cement-based mortars, in order to assess the influence of the single components. Digital image correlation (DIC) was also used to determine the displacement fields, strains and to detect the crack pattern of the specimens.

Experimental study on shear performance of improved high-performance polymer cement mortar–glass fiber reinforced plastic reinforced masonry wall

The improved high-performance polymer cement mortar (PCM) and glass fiber reinforced plastic (GFRP) system reinforcement was used in the research to strengthen and repair the masonry structure, so as to improve its bond stress, anchoring force, and integral performance without changing the original structure and further study the shear performance of masonry structure strengthened by the combination of the two. The optimum ratio of improved high-performance PCM was determined by analyzing the bend-press ratio of PCM test block. Improved high-performance PCM and GFRP were combined to strengthen the damaged masonry wall, and a five-piece masonry wall composed of “improved high-performance PCM+ with or without GFRP+ different original wall failure modes before reinforcement” was designed. Through diagonal loading shear test, the shear strength, vertical displacement, horizontal relative displacement, and failure models of masonry walls were obtained, and the effects of five different reinforcement methods and different materials on shear strength, stiffness, ductility, and failure modes of masonry walls were studied. The results show that compared with the unreinforced original wall, the shear strength of the masonry wall reinforced with the improved O4PCM is 43.5% higher, and its stiffness is also greatly improved, but the failure mode is still brittle failure; the shear strength of masonry walls strengthened by O4PCM and GFRP is 6.5% higher than that of masonry walls strengthened by O4PCM alone, and the stiffness is also increased. Its failure mode changes from brittle failure to ductile failure; with a failure mode of ductile failure, the shear strength of masonry walls strengthened by P4PCM and GFRP and that strengthened by P6PCM and GFRP are 4.8% and 12.7% higher than that strengthened by O4PCM and GFRP, respectively, and the stiffness is also increased compared with that strengthened by O4PCM and GFRP. After experimental comparison, it is the best scheme to strengthen masonry wall with improved P6PCM and GFRP.

Behavior of masonry infilled Chuandou timber frames subjected to in-plane cyclic loading

The Chuandou timber frame is a traditional timber structural system widely used for nonengineered residential houses in southwestern China; this system is featured by beam-to-column joints with direct penetration tenons and free-standing column bases. As concluded by a previous study, the Chuandou timber frames with proper infills have exhibited better seismic performance than un-reinforced masonry structures in terms of collapse prevention, although the mortise-tenon connections, masonry infills, timber beams and columns may have sustained various extents of damage. To investigate the seismic behavior of the structural system, six full-scale Chuandou timber frame subassemblies were subjected to in-plane quasi-static loading, four of which were infilled with masonry walls. The test results show that the masonry infills provided the most lateral resistance of the system, whereas the timber frames could sustain a large lateral drift without losing their vertical stability. The observed failure modes were identified from different specimens. The lateral strengths of the specimens in the current test were evaluated using the existing code equations. The results suggest the necessity of considering the aspect ratio in calculating the shear strength of masonry walls.

Analytical model based on artificial neural network for masonry shear walls strengthened with FRM systems

Abstract In the future Fiber Reinforced Polymer (FRP) materials will be considered a common strengthening system for civil structures thanks to several research efforts made in the last decades. For those applications in which FRP materials show some restrictions such as, above all, the incompatibility with heritage buildings, a new generation of fibrous materials has been developed. Researchers have investigated Fiber Reinforced Mortars (FRM) as external structural and seismic reinforcement. One of the most attractive applications of these materials is related to the in-plane shear strength of masonry walls. In this scenario, an analytical model based on Artificial Neural Network (ANN) is proposed and discussed in respect of the geometrical and mechanical variables that control the mechanical problem. An ANN is presented in the paper by showing its possible productive application in the civil engineering field. The proposed model seems able to predict the shear strength of FRM strengthened masonry; the approach is considered efficient since it includes both a theoretical method and a large test calibration, illustrated herein. Thanks to a quite small input database of laboratory results, ANN seems able to provide a theoretical solution to the problem with accuracy and precision.

Parametrical study of masonry walls subjected to in-plane loading through numerical modeling

This paper deals with the numerical assessment of the influence of parameters such as pre-compression level, aspect ratio, vertical and horizontal reinforcement ratios and boundary conditions on the lateral strength of masonry walls under in-plane loading. The numerical study is performed through the software DIANA® based on the Finite Element Method. The validation of the numerical model is carried out from a database of available experimental results on masonry walls tested under cyclic lateral loading. Numerical results revealed that boundary conditions play a central role on the lateral behavior of masonry walls under in-plane loading and determine the influence of level of pre-compression as well as the reinforcement ratio on the wall strength. The lateral capacity of walls decreases with the increase of aspect ratio and with the decrease of pre-compression. Vertical steel bars appear to have almost no influence in the shear strength of masonry walls and horizontal reinforcement only increases the lateral strength of masonry walls if the shear response of the walls is determinant for failure, which is directly related to the boundary conditions.