Bed joint reinforcement and the shear capacity of masonry beams

The design of reinforcement in masonry beams is strait forward. A few, relatively small diameter bars in one or two bottom layers is often sufficient to form a tie while in the masonry compressive struts develop. In the layers further away from the tensile area, often reinforcement is applied with the idea that this decreases the risk of crack development and might increase shear capacity. Masonry beams with a height of 490 mm, 550 mm or 625 mm and a span of 1400 mm, with and without extra bed joint reinforcement were tested. The results of these tests are presented and the effect of the extra reinforcement on shear capacity discussed.\u3cbr/\u3eIn a number of cases, bed joint reinforcement with a closed hoop configuration was applied. Extra reinforcement did not always increase shear capacity; on the contrary, the capacity was sometimes smaller because the extra reinforcement affected the capacity of the compression struts negatively

Effects of support conditions on lintel-masonry interaction

This paper describes research into the behaviour of so-called composite lintels i.e. load bearing masonry in combination with prefabricated concrete lintels. Eighteen identical walls were loaded in plane to rupture. Nine layers of stretcher bond masonry, 562.5 mm in height, were built on prefab concrete lintels (60×100 mm2) with a span of 2800 mm. The effects of two types of supports and two types of loading on the mechanical behaviour of in plane loaded composite lintels were studied. Roller supports were simulated by suspending steel blocks from the roof beam of the test frame. A support condition, often used in practice, was simulated by a layer of felt on a brick. Two series of six walls were symmetrically loaded at four points. A third series of six walls were asymmetrically loaded at one point. The mean failure shear load for the four point loading condition was Vfail = 31 kN. For the one point condition it was Vfail = 24.4 kN. On average, the ultimate load (Fult) was 15% higher than the failure load (Ffail). Supported on rollers, three walls failed in the constant moment area (mid span). The fifteen other walls failed in the maximum shear load area near the supports. The height of the compression zone at mid span depended on the support condition and was largest for the felt support condition, where horizontal movement of the lintel was restrained. The support condition (rollers or felt) had a negigible effect on the load bearing capacity

Variation in shear properties of masonry

Simultaneously with building masonry walls for lintel-tests, mortar prisms and shear-triplets were made. About four hundred mortar prisms were tested according to EN 1052-11 to validate the mechanical properties of the industrially made masonry mortar used. A series of tests was performed in which the mortar properties were varied by adding sand to study its effect on shear strength. Shear triplets were made using bricks but also using pieces of concrete lintel. More than two hundred triplets were tested in shear according to EN 1052-3. The features of the shear test set-up used, are discussed. The goal of the shear tests was to establish the strength variation due to a deliberate variation of mortar properties and mortar-unit interface. Shear strength increased and mortar compressive strength decreased when more sand was added. Suggestions for improvement of the test set-up are given

Composite action in CASIEL TLM walls, a literature review and experimental results

The paper gives a literature review of studies into the composite action between masonry and supporting beams aimed at the applicability of calcium silicate element walls in situations where they would act as deep beams. The experimental part of this study concerned a wall, made of calcium silicate elements, which stood on a floor above an underground car park. The test wall was made on a 1:3 scale. The bottom beam thickness was varied to study the effect of beam stiffness on load transfer. The effect of crack development on load transfer was studied by loading the bottom beam, simulating floor loading. The study showed that the areas around the supports are critical and that pre-cracking of the wall at mid span could be advantageous to prevent sudden extreme deformations. Suggestions for improvements of the structure are presented