International Concrete Abstracts Portal

This paper presents the details of experimental testing of block masonry triplets using the direct shear test to investigate the shear behaviors of block unit-mortar interfaces. Hollow blocks of 100 and 150 mm (4 and 6 in.) thickness and solid blocks of 100 mm (4 in.) thickness were included in the testing program. These were combined with mortars of three grades to cast a total of 84 triplets. In addition to testing the triplets in an unconfined state, three increasing levels of precompression stresses were used separately to test the confined specimens. The shear behaviors of the tested triplets were not influenced by block strength, while shear strength increased (almost) linearly with mortar strength. The mean peak shear stress for the unconfined triplets was 0.4 MPa (58 psi), whereas the average shear modulus of the joint for these triplets was 6.20 times the mortar compressive strength. The Mode II fracture energy of the masonry joints increased at higher precompression levels. The methods of determining shear strength, shear modulus, and shear strength parameters for the mortar joint in block masonry are proposed using the observed data.

An experimental study on the shear behavior of autoclaved aerated concrete (AAC) confined masonry walls is presented. A total of eight full-scale confined walls were tested in the laboratory under in-plane reverse cyclic loads. The variables studied were the aspect ratio and the axial compressive stress of walls. The shear behavior was characterized by diagonal cracks or flexure-shear and diagonal cracks. The final cracking pattern of the walls was defined by the traditional “X” pattern. Equations for shear strength and flexure-shear strength based on experimental data obtained in this and previous studies are proposed for AAC confined walls. A limit is established for the shear strength of walls as a function of axial compressive stress. The proposed equations predicted well the experimental strength of the AAC confined walls considered in this study.

Masonry walls are particularly vulnerable to large shear forces during earthquakes because of their low tensile strength and the heterogeneity of their material. In this paper, experimental results are presented for four masonry walls reinforced with textile-reinforced mortars (TRMs) and one unreinforced wall (URW) tested under quasi-static in-plane loading. These full-scale masonry walls were tested in the LMDC laboratory at the National Institute of Applied Sciences (INSA) Toulouse. Clay bricks and lime mortar were used in a traditional construction technique to build the walls. The four specimens were tested and damaged until failure. One of them was strengthened along its diagonals and the other three over their entire surfaces. Displacements and crack patterns were monitored using a network of sensors and a digital image correlation system. A comparison of the experimental results determined whether TRM could efficiently reinforce masonry walls and increase their loadbearing capacity. An increase in peak load and cumulative energy, respectively, was hence observed during the tests (140 kN and 3176 J for an unreinforced wall, and 343 kN and 13,303 J for one of the reinforced walls). These results provide valuable information about masonry wall strengthening for architects, structural engineers, and the scientific community.

Lightweight (LW) aggregates (LWAs) improve fire resistance, moisture resistance, and durability in addition to reducing the selfweight of concrete. However, the ACI 318 code includes a modification factor (lambda) to account for reduced tensile capacity in LW concrete. LWAs are not currently permitted for use in masonry grout due to lack of test data to establish appropriate modification factors for the TMS 402/602 code. This study is a pilot study that aims to experimentally determine how the tensile breakout and shear breakout capacity of cast-in-place bent-bar anchors in masonry assemblies with LW grout compare with the predictions of TMS 402-16 for anchors in normal weight (NW) grout, and with results in the literature for assemblies using NW grout to see if additional testing would be needed to determine a lambda factor for shear and tensile behavior of LW grout. The results indicate that a reduction factor for bent-bar anchor bolts in masonry constructed with LW grout may not be needed, but additional testing should be conducted with smaller bar diameters to demonstrate the consistency of these results across bar sizes.

The cyclic out-of-plane behavior of unreinforced masonry (URM) walls strengthened with externally bonded glass fiber-reinforced polymer (GFRP) strips is experimentally studied in this paper. A total of four fired clay brick masonry walls were prepared in this study. Three walls were seismically retrofitted by bonding vertical GFRP strips and one specimen was unreinforced and was used as built. All masonry walls were subjected to one-directional cyclic out-of-plane lateral loadings. The lateral cyclic out-of-plane behavior in terms of failure patterns, force-displacement behavior, ultimate strength and displacement capacity, secant stiffness, and hysteretic energy dissipation of each specimen was studied. The test results indicate that externally bonded vertical GFRP retrofitting significantly improves the cyclic out-of-plane performance of brick masonry walls. The ultimate out-of-plane flexural and displacement capacity of strengthened walls was increased up to 1000% and 300%, respectively, compared to the companion URM wall. Based on the principles of strain compatibility and internal force equilibrium, an analytical model is proposed for calculating the ultimate out-of-plane flexural capacity of GFRP-strengthened walls for different failure patterns. In addition, several design recommendations, such as the strain in GFRP strips at delamination failure and the maximum and minimum GFRP reinforcement ratio, were proposed based on strain compatibility.