Masonry materials, properties

The masonry material properties that characterize interested to see those effects can be grouped into the following categories ... 

This chapter provides material properties and response criteria necessary to design facilities constructed of reinforced concrete, reinforced masonry, structural stcc and cold formed steel. Static and dynamic properties are covered for the materials used in these facilities. Allowable response criteria are covered for both... 

At present, no readily available models are yet available for the beam-column joints, which are commonly neglected or assumed rigid in current practice. Another important issue is modeling the effects of the frame infills. It is well known that masonry infills influence the behavior of RC frames, but modeling the interaction is not easy. Strut elements have been proposed, but the selection of the material properties is not straightforward. 

Table 3.5 Material properties for brick and stone masonry and soil/rock ...

It should be noted that given the great variability of the masonry materials (piece and mortar) many types, compositions, geometries, resistances, etc. is necessary to study the variation of the thermal properties as a function of temperature through the literature. 

At high temperatures, the clay masonry presents thermomechanical effects (such as thermal expansion of the piece and the mortar, spallings, and loss of strength) as well as variation of the material properties due to the degradation. This chapter describes the characteristics of the thermal and mechanical properties that are of particular relevance to the variation of the temperature and then particularized to the piece and the mortar are described. The independent behavior of these elements will greatly influence the subsequent response of the masonry wall as a single homogeneous material. 

Since the geometry of the tower was surveyed on site and accurately described in the model, the main uncertainties are related to the characteristics of the material and boundary conditions. In order to reduce the number of uncertainties in the model calibration, the following initial assumptions were introduced (a) homogeneous distribution of the masonry elastic properties (b) the weight per unit volume of the masonry and Poisson s ratio of the masonry were assumed as 17.0 kN/m and 0.15, respectively and (c) the tower footing was considered as fixed since the soil-structure interaction is hardly... 

Regarding the modeling of the infill panels, the great number of influencing factors, such as dimension and anisotropy of the bricks, joint width and arrangement of bed and head joints, material properties of both brick and mortar, and quality of workmanship, make the simulation of plain brick masonry extremely difficult. The level of complexity of the analytical model depends on whether masoiuy is considered as one-, two-, or three-phase material, where the three phases are comprised of the units, mortar, and unit-mortar interface. 

Besides the review on masonry material components, it is important to present and discuss the most important mechanical properties of masonry assemblages, together with a discussion of the main parameters affecting the seismic performance of masonry under distinct loading configurations. Understanding the response of the basic masonry materials is essential for interpreting the seismic response of masonry structural systems. 

Unreinforced masonry structures present low tensile strength, and the linear analyses seem to not be adequate for assessing their structural behavior. On the other hand, the static and dynamic nonlinear analyses are complex, since they involve large time computational requirements and advanced knowledge of the practitioner. The nonlinear analysis requires advanced knowledge on the material properties, analysis tools, and interpretation of results. The limit analysis with macro-blocks can be assumed as a more practical method in the estimation of maximum load capacity of structure. Furthermore, the limit analysis requires a reduced number of parameters, which is an advantage for the assessment of ancient and historical masonry structures, due to the difficulty in obtaining reliable data. 

The macro-blocks are portions of a structure with similar material properties and structural behavior, to which the mechanical properties of the material can be assigned or, by simplification, they can be assumed to be infinitely rigid. The interfaces in a macro-modelling represent, in general, the cracks associated to the failure mechanisms. However, in a micro-modelling strategy applied to masonry, in which the units and the joints are individually considered, the interfaces simulate the behavior of the joints. Furthermore, different criteria for the strength parameters of macro-blocks and interfaces can be considered. 

Finally, the uniaxial behavior of the composite material is anisotropic, i.e., depending on the loading direction with respect to the material axes, namely, the directions parallel and normal to the bed joints. The compressive strength of masomy in the direction normal to the bed joints has been traditionally regarded as the sole relevant structural material property, at least until the recent introduction of numerical methods for masonry structures. A test frequently used to obtain this uniaxial compressive strength is the... 

The analytical determination of the gravity load distribution between the frame and the infill wall requires several considerations. First, a part of the gravity loads may be applied onto the RC columns before the construction of the infill walls because these walls could be constructed after the frame has been completed. Second, long-term effects such as concrete and masonry creep, concrete shrinkage, and brick masonry expansion with time due to water absorption can significantly affect the gravity load distribution. While refined finite element models with viscoelastic material properties can be employed for the determination of the gravity load distribution, the increased computational burden of such analyses may not necessarily produce results of increased accuracy due to lack of experimental data to allow the cahbration of multiaxial viscoelastic constitutive models. 

Due to the highly alkaline nature of most masonry materials, one of the fundamental properties required for high performance long-life coatings on such a substrate is resistance to saponification. Unlike alkyds (polyesters), acrylic polymers have a carbon-carbon backbone which is much less vulnerable to chemical attack. Whilst isomerised rubber and chlorinated rubber coatings are stable when applied over alkaline substrates, thermoplastic acrylics offer better hght-fastness for exterior use and also confer ... 

A substance that, because of its physicochemical nature, will not mix or blend with another substance.. All hydrophobic materials have water-repellent properties due largely to differences in surface tension or electric charges, e.g., oils, fats, waxes, and certain types of plastics. Silicone resin coatings can keep water from penetrating masonry by lining the pores, not by filling them they will not exclude water under pressure. 

Anchoring systems are materials used mainly for securing bolts, bars, tendons or dowels in drilled or formed holes in concrete, masonry or natural rock. Polyester anchors are widely used because of their fast curing property and high early strength (Fosroc International, undated a). Epoxy anchors are applied in areas where there is a risk of alkaline hydrolysis. 

Polyurethane rigid foam is an excellent insulation material, particularly well suited for applications requiring high mechanical properties. In the form of laminated boards, they are applied on roofs, ventilated facades, ventilated double walls, masonry construction, single-wall masonry interior walls, floors and ceilings and for floor heating systems. 

Silicones have been used as masonry water repellents for more than 40 years. Mineral btiilding materials absorb water and change their properties. The source of water is moisture, frost and efflorescence. The absorption of water depends on the porosity of the material. Water conveys destructive agents inside the building material, causing damage to the building. The absorption of water occurs by a number of routes (Wacker-Chemie, 1989), as will now be described. 

Finally, it must be stressed that designers, suppliers, and installers of each of the three main elements the chemically-resistant masonry, the membrane and the wooden support must cooperate, discussing and agreeing on the total final design so that the diverse properties of the materials are combined for maximum economy, performance and safety. Failure to obtain such agreement can result in the failure of any structure created by the marriage of such diverse elements. 

PVDF exhibits the excellent resistance to harsh environments, characteristic of fluoropolymers. It is widely used in the chemical processing industry, in piping systems, vales, tanks (both molded and lined), and other areas where its combination of excellent mechanical properties and superb resistance to most chemicals make it an ideal material for fluid handling equipment. Increasingly important is use of PVDF as the base resin for long-life, exterior coatings on aluminum, steel, masonry, wood, and plastics. 

Bond properties at elevated temperatures. The bond, which relies heavily on the mechanical (shear) properties of the polymer matrix or adhesive, can be expected to be severely reduced at temperatures exceeding the glass transition temperature, Tg, of the matrix or the adhesive. Essentially no information is currently available on the specific behaviour of the bond between unprotected externally bonded FRP materials and concrete or masonry at high temperature. For example, in the case of insulated FRP systems, it is not clear exactly how long the bond between the externally bonded FRPs and the substrate can be maintained during a fire. 

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