Caracterização mecânica das argamassas de assentamento para alvenaria estrutural – previsão e modo de ruptura

Este trabalho pretende avaliar o comportamento mecânico das argamassas de assentamento para o uso estrutural, por meio das propriedades de resistência à compressão, tração na flexão e módulo de elasticidade, sob estados de tensões uniaxial e multiaxial. Portanto, estabelecer correlações entre os resultados mecânicos de diferentes traços de argamassas, relações água/cimento e geometria da amostra associada ao modo de ruptura. As principais conclusões obtidas, entre outras, são: existe uma relação potencial entre a resistência a compressão da amostra de geometria cúbica, cilíndrica e a resistência à flexão (amostra de geometria prismática) em função da relação água/cimento; a função linear é a que melhor ajusta os valores médios do módulo de elasticidade em função da resistência à compressão; a envoltória de ruptura da argamassa confinada lateralmente pode ser representada como uma relação linear de Mohr-Coulomb; observou-se, por meio de ensaios de microscopia eletrônica de varredura a existência de fissuras de retração na interface pasta-agregado e poros isolados, devido ao fluxo ascendente de água causado pela exsudação

Structural behavior of mortarless interlocking load bearing hollow block wall panel under out-of-plane loading.

Experimental and numerical investigation of interlocking mortarless wall panels with 1.0 m height, 1.2 m width and 150 mm thickness are conducted. Behaviour of both hollow and partially grouted masonry wall panels is studied. The panels were tested under constant pre-compressive vertical load and out-of-plane lateral load. Lateral load carrying capacity, deflection at mid height, dry joint opening between block layers and mode of failure are investigated. Strain characteristics throughout the loading process are also monitored. A finite element analysis is presented for the system and a good agreement between the experimental and modelling results is achieved. Parametric study using the finite element model is also presented and the effect of different parameters; amount of pre-compressive load and slenderness ratio is studied. The study reveals that pre-compressive vertical load and reinforcement significantly affect the structural behaviour of mortarless walls under out-of-plane loading. Useful expressions for the capacity are obtained from the analysis

Continuity and change; Peruvian education.

Meeting: Seminar on Continuity and Change in Contemporary Peru, 1973, New York, N.Y., USPhotocopy of original.IDRC pers CRDI. Paper on educational development and educational reform in Peru, especially under the Revolutionary Government of the Armed Forces - discusses role of the educational system in social change, educational administration, level of literacy, educational policy especially regarding the language of instruction in the rural areas, reform of university education. Bibliographic notes

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

Introduction to post-tensioned shear walls of calcium silicate element masonry

In Western Europe, load-bearing masonry structures are frequently built with calcium silicate elements (CASIELs) combined with thin layer mortar. The height of CASIEL masonry shear walls is limited by the overturning moment. The recent development of high strength CASIELs opens new perspectives. By prestressing masonry, the moment and shear capacity of shear walls can be increased, providing overall stability of higher buildings. Unfortunately, application of this construction method in building practice is limited due to lack of design rules for prestressed masonry in European standards, e. g. Eurocode 6 [1]. Additionally, experimental data on prestress losses due to creep and shrinkage of high strength CASIEL masonry are not yet available. At Eindhoven University of Technology, a project has been set up to systematically investigate the moment and shear capacity of post-tensioned shear walls of CASIEL masonry by means of experimental, numerical and analytical research. Final goals of the project are the development of design rules for post-tensioned (CASIEL) masonry and guidelines for simple and effective post-tensioning systems which ensure overall stability of buildings during construction and working life

Mechanical response of solid clay brickwork under eccentric loading. Part I: Unreinforced Masonry

The compressive strength of eccentrically loaded masonry, affecting the strength of arches, vaults, pillars and out-of-plane loaded masonry panels, is addressed in this paper both from the experimental and numerical point of view. The aim is that of relating the eccentric compressive strength to the concentric value, to the mechanical characteristics of the constituents, i.e. mortar and bricks, and to the brickwork bond. In the paper, displacement controlled compression tests on solid clay brick and cement-lime mortar masonry prisms, under concentric and moderate-to-highly eccentric loading, are presented and discussed. The experimental outcomes and the results of FEM models give a preliminary insight in the mechanical response of masonry up to collapse. It is found that edge effects may affect the load carrying capacity of the brickwork, while detailed measurements on the mortar joints show that the plane section assumption, typical of many design procedures, is reasonably verified up to the limit load, giving way to simplified but reliable design procedures