A non-destructive method for fixing placards with masonry structures

It is common practice for government agencies to fix signs – and indeed even official temporary notices – onto masonry structures using steel nails. This method of fixing is destructive; it causes irreversible damage to the material fabric, which has a bearing on the overall aesthetic of the building, a scenario which is more acute if the site is of cultural heritage significance. Stones and concrete blocks (locally referred to as concrete bricks), the latter introduced in the 1950s, are the main materials used in masonry construction in Malta. Clay bricks are not utilized, as in Malta there is a blanket prohibition on the extraction of local clay. The main building material used in Malta since time immemorial is Lower Globigerina Limestone. This article puts forward the case for a non-destructive, reversable method to fix notices to building which respects the integrity of the dimension stones. Instead of being hammered into masonry blocks, the proposed removable plugs are installed in the mortar. Their size is relative to the thickness of the mortar bed and the load they are designed to carry, the latter being of negligible importance in the case of lightweight placards. The proposed solution applies equally to other masonry structures, whether erected in dimension or randomly placed stones, concrete blocks or clay bricks, as long as the construction in question uses mortar in the joints between the units.peer-reviewe

A FULLY IMPLICIT MATERIAL RESPONSE CODE WITH ABLATION AND PYROLYSIS FOR SIMULATION OF THERMAL PROTECTION SYSTEMS

The purpose of this paper is to introduce and describe a 2-D fully implicit numerical simulation tool capable of evaluating the behaviour of an ablative charring thermal protection system during atmospheric entry. In particular, the computational tool can model the heat transfer inside a solid porous material and the decomposition of the latter, pyrolysis gas density, pressure and speed distributions and surface recession. The governing equations are fully coupled and are integrated using a time-implicit scheme. The grid can contract to simulate the recession phenomenon and the recession rate can be evaluated using different ablation models, depending on the problem and on the available data. Spatial and temporal convergence tests demonstrated that the tool is second order accurate in space and time and comparisons with available numerical results are shown here for code verification

Lending a helping, healing hand

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Thermal behavior evaluation of ventilated roof under summer and winter conditions

One of the European Directive priorities is the development of new strategies for \u201cvery low energy buildings\u201d. In regions with high level of solar radiation, ventilation allows the cooling load during summer period and contributes to the reduction of the energy needs of buildings. The most important advantages are the reduction of the heat fluxes transmitted by the structures exposed to solar radiation, thanks to the combined effect of shading surfaces and heat removed by the air flow rate within the ventilated air gap. This paper illustrates a numerical investigation on a prototypal ventilated roof for residential use. The investigation is performed in order to evaluate thermofluidodynamic behaviors of the ventilated roof as a function of the different conditions applied on the top wall and the bottom wall of the ventilated cavity in summer and winter regimes. Different values of heat fluxes are applied on the top wall of the ventilated cavity to simulate typical summer and winter days conditions, whereas the bottom wall is assumed isothermal and different values of wall temperature are considered. The problem is solved by means of the commercial code Ansys-Fluent. Results are given in terms of temperature and velocity distributions, air velocity and temperature profiles along different longitudinal and cross sections of the ventilated layer in order to estimate differences between analyzed conditions

Thermal behavior evaluation of ventilated roof under variable solar radiation

A ventilated roof has a good configuration for energy purposes, in order to respect the European Directive priority for building performance requirement to reduce energy consumption. In Mediterranean regions, with high level of solar radiation, the roof design should respect comfort and energy saving, considering that climatic conditions change depending on seasons and territories. This paper illustrates a numerical investigation on a prototypal ventilated roof for residential use, in order to evaluate its thermofluidodynamic behaviors as a function of the solar radiation applied on the top wall of the roof simulating summer and winter conditions. The roof is modeled as a single side and it is analyzed as two-dimensional, in air flow, thanks to the commercial code Ansys-Fluent. Results are given in terms of temperature and pressure distributions, air velocity and temperature profiles along longitudinal and cross sections of the ventilated layer, in order to estimate the differences between the various conditions. Ventilated roof configuration results significant to reach optimal thermal and hygrometric conditions in summer and winter conditions