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Snow distribution on a building surface is uneven due to the complicated drift movements of snow grains affected by the wind. Therefore, an accurate estimation of the snow distribution on a building’s roof is essential in protecting its structure. The existing wind tunnel tests of snow distribution on roofs do not consider the influences of falling snow, resulting in deviations between the test results and the actual snow distribution. In this study, a wind tunnel test method considering the snow falling process was proposed to simulate the irregular snow distribution on stepped flat roofs during snowfall. Based on the test data, the variation rule of snow distribution on the stepped flat roof with different test methods and conditions is summarized. (1) The results of the conventional snow erosion test, which neglected the influences of falling snow, deviated from the existing measurement results. (2) The test results of the proposed method with varying wind speeds and grain sizes met the double-linear or triple-linear rule, which conformed to the measurement results. (3) The initial snow significantly influenced the snow distribution on the front of the lower roof on windward side but only slightly affected the snow distribution on the other locations. The research conclusions could provide significant contributions to the actual engineering design.

The article analyses the impact of wind suction on roof coverings glued with polyurethane adhesives to flat roofs, i.e., roofs with an up to 20% slope. The impact of the cyclical wind was simulated in fatigue tests, gradually increasing the test pressure in repeated sequences until the first delamination occurred. The tests were carried out for eight test sets, with concrete and trapezoidal sheets used as a construction substrate, on whose surface thermal insulation layers were glued with polyurethane adhesive; the thermal insulation layers were EPS (expanded polystyrene) and PIR (polymer mainly of polyisocyanurate groups), respectively, followed by flexible sheets, i.e., a laminated PVC membrane (polyvinylchloride) and an EPDM (terpolymer of ethylene, propylene and a diene with a residual unsaturated portion of diene in the side chain)-type rubber-based membrane. The test results were compared with the functional requirements determined with computational simulation methods for the maximum wind load values on the example of wind loads for Poland. The tests confirmed that some polyurethane adhesives could ensure the operation of flexible sheets used as flat roof coverings that are failure-free from the point of view of resistance to wind suction.

The Sustainable Development Center of the University of Brasilia is one of the modernist buildings that make up the Darcy Ribeiro campus. The architectural project contains several recommendations for the execution of a flat roof waterproofing system, as well as details for rainwater runoff and drainage, which reveals the architect’s concern with watertightness. This research seeks to identify the relationship between the pathological manifestations recognized on the roof and the details of the semicircular shape of the building, assessing the state of conservation using damage maps as an auxiliary analysis tool. This study is based on a field survey using aerophotogrammetry with a drone, the application of vector drawing software for graphic representation and discussion of the possible causes, and the agents and mechanisms of degradation at work. The results show the importance of mechanical protection for the good performance of the waterproofing system, as well as the need for correct sizing of expansion joints to absorb and relieve the stresses caused by hygrothermal variations. The incorporated methodology proved to be effective and economical in diagnosing and monitoring pathological manifestations, making it possible to plan maintenance actions that extend the useful life and preserve the intrinsic characteristics of building systems.

The contribution is focused on the numerical verification of the correct design of compact flat wooden roofs in the external boundary conditions of Central Europe (Vienna - Bratislava); the internal boundary conditions of the analysis met the requirements for human habitation. Using the WUFI 2D software, the compositions of compact flat roofs were analyzed using a vapor barrier and a variable vapor retarder with a low dispersion of diffusion thickness values and a variable vapor retarder with a high dispersion of diffusion thickness values. Each of these three compositions was assessed in versions without shading and with shading of the surface (by graveling the roof covering from the exterior side). The length of the analyzed period was 5 years. The main goal was to verify the accumulation of moisture in layers of the structure and whether critical moisture conditions suitable for the formation of molds and fungi causing rot will be reached in any of the compositions. The measurement results showed the different functioning of compact flat wooden roofs depending on the shading, as well as other conclusions for the design and realization of the composition of compact flat wooden roofs.

The assessment of extreme wind loading on solar arrays plays a significant role in ensuring their safe operation under strong winds. Therefore, this paper investigates the extreme wind loading on solar arrays mounted on a flat roof by taking into account the wind directionality effect. The estimation process is conducted by using in situ wind speeds obtained from meteorological stations and wind loading coefficients on solar arrays obtained from wind tunnel tests based on the joint probability distribution of multiple variables and their conditional probabilities. This allows a discussion regarding how the extreme wind loading of solar arrays would be affected by such factors as the uncertainty of wind loading coefficient, the structural orientation of buildings on which solar arrays are mounted, and the directional characteristics of wind speeds. Finally, a comparison among the proposed methods, considering the wind directionality in current wind loading codes, is performed. The extreme wind loading determined by multivariate extreme value theory is found to be comparable to the corresponding estimate calculated according to the independent assumption of directional extreme wind speed. The results of this study provide a valuable reference for the design of wind-resistant solar arrays that takes account of wind directionality effect.

The new fabricated box-shaped steel grid-concrete composite thin-shell roof structure is a new structure based on the large-span steel-concrete composite thin-shell roof. An assembly unit composed of thin-walled steel ribs with bolt holes, a steel bottom plate, and concrete, and a thin-shell roof structure formed by assembly connection between the assembly units. A comparative analysis of the deformation and stress of the flat roof and arched roof structure shows that when the span is less than 30m, the difference between the deformation and stress of the two structures is not large, and it is more reasonable to choose the flat assembled composite roof structure. The construction difficulty is lower. When the span is 40m, the maximum vertical displacement of flat roof and arched roof are 53.73mm and 17.81mm respectively, and the difference gradually increases from 40m. After the span exceeds 40m, the stress between the steel box and concrete of the flat roof structure. The ratio increases sharply, and the arched roof shows a uniform change trend. The material utilization rate of the arched roof is higher than that of the flat roof.

The structure of parabolic condensers makes them susceptible to wind load because of their thin and large windward mirrors. In this paper, the wind pressure on a model of a condenser mirror (1:35) on multistorey flat roofs is analysed via pressure measurement in a wind tunnel. The mean wind-pressure distribution law of flat-roof condenser mirrors (including the change law with working conditions and the maximum distribution characteristics) and the distribution law of fluctuating and extreme wind pressure are obtained. Furthermore, by comparison with the ground-based condenser distribution law, similarities and differences between the two are obtained. Research results show that the wind-pressure distribution law of flat-roof parabolic condenser mirrors is the same as those on the ground, but the mean wind-pressure coefficient (absolute value) is generally ~30% smaller. Furthermore, the maximum effect is generally located at the windward mirror edge and the mirror is more susceptible to wind pressure in wind directions of 30° and 135°–150°. The results of this study can provide a theoretical reference for wind-resistant structure design and multistorey flat-roof condenser-related research.

PurposeUnderstanding the dynamic hygrothermal behavior of building elements is very important to ensure the optimal performance of buildings. The Laboratory for Quality Control in Buildings of the Basque Government tested a flat roof designed by a construction company that developed a building to be constructed using prefabricated modules. This is a five to eight floor building with ventilated façade and a flat roof covered by gravel with the possibility of changing it to a green cover. The paper aims to discuss this issue.Design/methodology/approachThe interest of this research was threefold. The first objective was to accurately test, under real dynamic weather conditions, the roof design in a PASLINK test cell to obtain the U-value and the thermal capacitance of the different roof layers, and of the roof as a whole, through the precise calibration of resistance-capacitance mathematical models of the roof. Based on the parameters and experimental information of these calibrated models, a second goal was to calibrate and validate a Wufi model of the roof.FindingsThis second calibrated model was then used to simulate the dynamic hygrothermal behavior of the roof, obtaining the roof’s hourly thermal demand per square meter for a whole year in different locations considered in the Spanish Building Code. These simulations also permitted the authors to study the risk of condensation and mold growth of the tested component under different climatic conditions.Originality/valueThe successful combination of the PASLINK method to calibrate the Wufi hygrothermal model is the main novelty of this research.

The paper deals with the monetization assessment of the environmental impacts of current systems of flat roofs. Monetization techniques are commonly used for evaluation of the negative environmental impact. Environmental impact can be defined as a change in the environment, whether favourable or unfavourable, which is wholly or partly due to human activity. Very often, environmental impacts are characterized by climate change such as global warming, acidification, eutrophication, ozone depletion, etc. With regard to the different units of the individual parameters of environmental impacts, it is very difficult to make a comprehensive assessment of the environmental impact. The goal of the paper is the case study of the economic evaluation of the environmental impacts of the building's structures. The monetization process is represented on the assessments of current systems for flat roofs. The roofs act an essential view of the sustainability of the urban area. Roof structures influence economic, environmental and social impacts in the context of the urban area. Environmental impacts and its monetization are assessed throughout the life cycle of a building element or structure.

Proper selection of thermal insulation materials is an essential part of almost any construction project, whether it is a new construction, renovation or revitalization. There is a large number of materials available on the market and it is often very difficult to have a good grasp. Though some material has very similar features, they often cannot replace each other. The same applies to single-shell flat roofs. So far the most often used thermal insulation boards are from polystyrene and mineral wool. Their installation is accompanied by a large volume of waste. The experimental part deals with the general assessment of the behavior and properties of foam concrete. This allows simplification of technology of thermal insulation laying. Besides the construction speed up and the overall cost reduction the improvement in mechanical properties of the roof structure has been achieved.