Assessment of mortar properties in vintage clay brick unreinforced masonry buildings

Mortar is a principal structural component of unreinforced masonry (URM) buildings, with mortar mechanical properties having an important influence on the behaviour of URM buildings when subjected to earthquake induced shaking. However, the mechanical properties of in situ mortar have long been known to be difficult to obtain. Recommendations on mortar properties for preliminary assessment of URM buildings, as well as details of field assessment procedures for in situ mortar characterisation have been previously suggested in national standards and guidelines in the USA, New Zealand and seismically active countries in Europe. An experimental study was implemented in order to investigate an improved characterisation procedure for vintage mortars, to be used by structural engineering practitioners with the aim to improve the accuracy of building seismic assessments, computer modelling and subsequent seismic retrofit designs. The tested mortar samples were extracted from 60 different vintage URM buildings throughout New Zealand. A non-standard mortar compression test procedure was developed, and an alternative in situ assessment technique to estimate mortar compressive strength was investigated. Supplementary tests to estimate the mortar aggregate/binder ratio and to predict the presence of cement in the mortar are also discussed.     

Shell scientist honoured at AIChE conference

Jose Bravo of Shell Global Solutions (US) Inc was honoured at the recently-held annual meeting of the American Institute of Chemical Engineers (AIChE) for his achievements in the field of separations technology for the process industry.     

Determining the best departments by their best publications: A strategy best avoided

The technique of sampling a department'sk best publications as a means of assessing the quality of its research performance is investigated. It is shown that this procedure confounds merit with departmental size, and leads to a substantial overestimation of the research achievement of larger departments. The 1985–86 evaluation of research performance conducted by the University Grants Committee of the United Kingdom contained a sampling error of this kind.     

Salt diffusion in brick structures

Salts causes surface damages and efflorescence for masonry walls. This has increased the interest to understand the salt transfer phenomena taking place in porous matrix. There is still however a lack of published transport data in the literature. Especially the diffusion coefficients of salts in different brick structures are lacking. In this work a method for measuring the rate of diffusion of salt in ceramic material is presented and applied to the measurement of diffusivity of NaCl in three different brick materials. Fick's first law of diffusion was applied to calculate the diffusion coefficients in a pseudo stationary state by means of linear regression analysis. The result for the diffusivity of 0.05 molar NaCl in water in new Finnish red brick was (0.499 ± 0.004 ) * 10^–5 cm²/s in the temperature of 25 ± 0.05°C. The corresponding values for the old light brick and old dark brick was (0.453 ± 0.008) * 10^–5 cm²/s and (0.337 ± 0.009) * 10^–5 cm²/s respectively. The diffusion coefficients are given as an effective diffusion coefficients calculated with the porosity value measured to each of the specimen. The concept of salt diffusion and diffusion mechanism inside the porous matrix are also discussed.     

Movement of brick panel cladding

Movements of masonry brick panels, determined from dimensional changes measured at the joints, have been measured in three directions: horizontal and vertical in the plane of the wall and perpendicular to it. They were analysed as a function of temperature change and as a function of time. The analyses supported the hypothesis that thermal movement in the horizontal direction is altered by moisture content variations in the porous panels. Movements caused by moisture attenuated, and in some cases overrode, thermal movements. In the vertical direction the panels made one large movement in winter corresponding to the yearly temperature change and oscillated in other seasons. Movements perpendicular to the panel indicated curling of the edges.     

An 8-node brick finite element

An 8-node brick element based on the assumed stress hybrid formulation is described. With three additional stress fields, the element stiffness matrix now has the required rank of 18, and the ‘bending’ response is exact with rectangular elements. Surprisingly, the 2 × 2 × 2 Gauss rule suffices for all numerical integrations, to satisfy the constant stress patch test.     

Studies on brick masonry under compression

In China, brick masonry is extensively used in the construction of multi-storey dwellings, as well as in single-storey industrial plants and warehouses. Therefore, studies in this field are numerous. This paper presents only the experimental studies and proposed calculations for unreinforced and reinforced brick masonry under compression.     

Studying of salt diffusion behaviour in brick

In this paper, an analysis of the diffusion behaviour of salts in fully saturated brick is presented. This paper extends the previous work to including more salt types and measurement data. Dependence of diffusion coefficient on temperature and other factors is discussed. Starting from the mathematical model which has been verified before, the obtained results are 2-fold: first the diffusion coefficients for different types of salts are given which are evaluated from measurements; moreover, dependence of temperature and ambient salt concentration on diffusion coefficient is presented.     

In-plane behavior of perforated brick masonry walls

This paper reports the results of experimental and theoretical research conducted on perforated brick masonry walls under in-plane loading. The walls?? structural behavior depends strongly on their specific features, e.g. geometry, mechanical properties of the masonry material, brick arrangement and loading conditions. The experimental program was designed to study the incidence of brick arrangement in the spandrels and piers, and of the acting vertical load on the failure mode and load-bearing capacity of the walls. Six specimens of brick masonry wall with a central opening were submitted to a constant vertical load and a monotonic horizontal force that was gradually increased until the kinematic mechanism condition was reached. The object of the theoretical research was to develop a simplified analytical model for describing the kinematic mechanism of the walls. The results of the experiments indicate that brick arrangement strongly influences the failure mode and load-bearing capacity of the walls. Proper a priori assessment of the failure mode of walls becomes fundamental to an accurate evaluation of their load-bearing capacity using the proposed model.     

Added value and employment effects of brick industry

In Germany manufacturing and distribution of bricks care for direct employment of about 10,000 persons. Procurement of preliminary work and the utilisation of the payed salaries, social security contributions, taxes, and profits secure more than further 25,000 jobs. It can be assumed that a substitution of masonry by other building materials is not possible in the near term, since the masonry has increased its market share in the past few years even slightly. Thereby the masonry participates in the added value based on the shell construction of buildings in the amount of 32.4 billion Euro, and in the employment of 480,000 working people. The expansion of these buildings leads to further added value in the amount of 39 billion Euro and further employment of 691,000 employees. In the year 2016 in total, the construction of buildings with masonry has led to an overall economic added value amounting to more than 70 billion Euro and to an employment of about 1.17 million persons. Masonry products form the basis of this added value and employment, without which the construction of the buildings would not be possible.     

An improved EAS brick element for finite deformation

A new enhanced assumed strain brick element for finite deformations in finite elasticity and plasticity is presented. The element is based on an expansion of shape function derivatives using Taylor series and an extended set of orthogonality conditions that have to be satisfied for an hourglassing free EAS formulation. Such approach has not been applied so far in the context of large deformation three-dimensional problems. It leads to a surprisingly well-behaved locking and hourglassing free element formulation. Major advantage of the new element is its shear locking free performance in the limit of very thin elements, thus it is applicable to shell type problems. Crucial for the derivation of the residual and consistent tangent matrix of the element is the automation of the implementation by automatic code generation.     

随机需求物品最佳订购量及最佳客户服务水平分析

对一类具有正态分布随机需求,销售时期只订购一次的物品,建立数学模型,分析了最佳客户服务水平以及最佳订购量,求出了最优订货决策,并运用EXCEL表格软件对理论结果进行了模拟仿真验证.