Roof Shape Research Articles

EFFECTS OF ROOF SHAPES ON WIND PRESSURE DISTRIBUTION OF MULTI-SPAN LOW-RISE BUILDINGS

The present study demonstrates the numerical investigation to find out the effects of roof shapes on the wind pressure distribution of multi-span low-rise buildings. Most of the wind load standards of various nations are provided with wind load information of isolated low-rise buildings which in turn practically came out to be inapplicable during the designing of low-rise buildings with multi-spans. Also, most of the wind load studies are carried out using boundary layer wind tunnel (BWLT) which is sometimes not available, time taking process, and is expensive. Therefore, in the present research, numerical simulation has been done for the model of a low-rise building. For investigation, the Ansys CFX platform has been used with the k-ε turbulence model for different angles of wind incidence at an interval of 15°. The wind pressure distribution has been investigated for the model low-rise building with a rectangular plan having six spans of different roof forms i.e., cylindrical roof, mono-slope roof, hip roof, and dome roof. The outcomes of the present numerical investigations are presented in the contour plots of wind pressure and coefficients of wind-induced pressure on the different roof forms of low-rise buildings. The outcomes of the study will be so much beneficial to structural design engineers while considering the wind loads calculations on the different roof forms for low-rise buildings.

Effects of Roof Shape and Roof Pitch on Extreme Wind Fragility for Roof Sheathing

Wind fragility curves for roof sheathing were developed for single-family building models to investigate the effects of roof shape and roof pitch on the wind performance of roof sheathing. For gable roofs, it was found that more complex roof shapes are more likely to suffer roof sheathing damage when subjected to high winds. The probability of no roof sheathing failure can be up to 36% higher for a simple gable roof than for a complex gable roof. For hip roofs with different configurations, variation in roof shape has minimal effect on roof sheathing fragility. Roof pitch effects were also evaluated for 10 pitch angles, ranging from 14° to 45°. Results suggest that for roof pitches smaller than 27°, the effects of this angle are more substantial on the performance of gable roofs than on hip roofs. For gable roofs, the probability of no roof sheathing failure can be up to 23% higher for a 23° roof pitch than that for an 18° roof pitch. Furthermore, the inclusion of complex roof shapes in a regional hurricane loss model for New Hanover County, North Carolina, accounted for a 44% increase in estimated annual expected losses from roof sheathing damages compared to a scenario in which all roofs are assumed to have rectangular roof shapes. Therefore, to avoid an underestimation of roof damages due to high-wind impact, the inclusion of complex roof geometries in hurricane loss modeling is strongly recommended.

Evaluation of the Influences of Different Roof Shapes on the Flow Properties and Performance of Small Wind Turbines

Small wind turbines offer a complement to photovoltaic systems and are becoming an interesting solution in the wake of rising energy prices. The measurement results indicate that some locations on and around the building are not suited for installing wind turbines, while others show increased wind potential. Due to limited space, rooftop mounting is an interesting alternative to free mounting on a mast from a technical point of view. For this reason, the influence of roof shapes on the flow on and behind the building was measured and the performance of two different types of small wind turbines was investigated. The turbines assessed in the project are VertikonM with a vertical axis and helix-shaped rotor blades, and Superwind 1250 wind turbine with a horizontal axis and centrifugal force pitch control. The results showed that there is an average increase in wind speed of 0.2 m/s on gable roofs at hub height (7 m). In comparison, there is an increase of 0.4 m/s on flat roofs at hub height (7 m). In relation to the performance of the turbines, high turbulence on the roof seems to cancel out this effect. The performance of the horizontal axis small wind turbine has not increased in comparison with gable roof and free-standing mast. For the vertical-axis turbine, a power increase by a factor of 2.23 was achieved between free-standing mast and gable roof. Vertical wind flow above the gable roof was identified as the main cause for power increase. The experiment was conducted on the Lichtenegg energy research park (Lower Austria) and its results make it possible to better identify all effects that affect the turbine output power.

STUDY ON SNOW CORNICE ON EAVES OF FLAT ROOFS

To establish of estimation for snow cornice on flat roofs, the authors conducted wind tunnel test using natural snow and field observation subjected to the two buildings, and then examined the methods to estimate the snow cornice using roof shape coefficient based on the wind speed.

Geometric reasoning for the freehand-drawn delineation of 2D geometries

The mapping from aerial imagery and the creation of technical line drawings are prominent examples of the application of interactive software. These systems usually restrict the user’s interaction to enforce human-made structures such as orthogonality and parallelism. We propose a modeless approach that evaluates freehand-drawn pen strokes as the only user input. The approximating uncertain straight line segments are the basis for a reasoning process, comprising the recognition of geometric relations and their immediate enforcement via an efficient adjustment procedure. This approach avoids the possibly tedious and time-consuming selection of appropriate tools. Furthermore, during a step-by-step construction, the user needs not to be aware of the underlying design principles explicitly. We demonstrate the feasibility and usability of the approach by considering applications in the context of educational technology and large-scale mapping from imagery—the study of closure theorems and the polygonal tracing of roof shapes in orthophotos.

Vulnerability of Buildings to Meteorological Hazards: A Web-Based Application Using an Indicator-Based Approach

Recent events have demonstrated the devastating impact of meteorological hazards on buildings and infrastructure. The possible effects of climate change on their frequency and intensity but also the rise in the value of assets may increase future risks significantly. It is crucial, therefore, for decision-makers to analyze these risks, focusing on the vulnerability of the built environment to reduce future consequences and the associated costs. However, limited studies focus on the vulnerability of buildings to meteorological hazards. The aim of the present paper is to introduce an indicator-based vulnerability assessment approach for buildings subject to three meteorological hazards (windstorms, heavy rainfall, and hail). The selection of vulnerability indicators (e.g., material, roof shape, etc.) was based on a thorough literature review. The results of an expert survey were analyzed using M-MACBETH software, and the Analytic Hierarchy Process (AHP) was used to weigh each indicator according to the expert opinions and to aggregate them into an index. A web-based application was developed that gives homeowners and other end-users the opportunity to assess the vulnerability of specific buildings by indicating the municipality, the building type, and other building characteristics. The web-application is publicly available and free of charge. The resulting index is a valuable tool for decision-makers, homeowners, authorities, and insurance companies. However, the availability of empirical damage data from real events could contribute to enhancing the performance of the presented approach.

Stability and optimization of small-spacing two-well (SSTW) gas storage salt caverns in bedded salt formation

Many rock salts in China have a bedded structure, consisting of several thin interlayers and salt layers. To eliminate the limitations of the conventional single-well gas storage caverns, the small-spacing two-well (SSTW) salt caverns can be utilized. In this paper, under the geological conditions of Pingdingshan salt formation in Henan province, China, a geomechanical model was established to evaluate the stability of the SSTW salt cavern. The deformation, volume shrinkage rate, and safety factor were used for the cavern stability evaluation. The optimal cavern roof shape, two-well spacing, and cavern roof height were determined by analyzing the salt cavern stability under constant pressure conditions. Based on the optimal salt cavern morphology, the stability of the salt cavern and interlayers under various injection and withdrawal cycle frequencies are investigated. The results show that the rampant arch-shaped SSTW salt cavern has good feasibility in Pingdingshan salt formation. The cavern roof vertical displacement and volume shrinkage decrease with the increase of cavern roof height, and it is suggested that the ratio of cavern roof height to cavern height is at least 0.26. With the continuous increase of the two-well spacing, the cavern volume shrinkage also increases. It is recommended that the ratio of the two-well spacing to the single cavern radius should be no more than 0.625. The increase in cycle frequency reduces the duration of salt caverns under low-pressure conditions, thus improving the mechanical stability of the cavern and interlayers. This paper provides design and operation parameters for the SSTW salt cavern in Pingdingshan salt formation and can also be a reference for the construction of other SSTW salt caverns.

Thermal Environment Analysis of Selected Polyethene Cladded Single-Span Greenhouse Shapes Models Towards Cooling Needs

Greenhouse energy management is one of the most significant factors of consideration in greenhouse agriculture. Besides implementing energy supply systems to the facility, energy-saving measures must also be taken into consideration. To address the issue of energy demand by greenhouses in a tropical environment, three greenhouse models were developed to simulate their thermal environments utilizing the Transient Systems Simulation Program (TRNSYS 18) as a building energy simulation (BES) platform. The proposed models were used to examine the impact of greenhouse design parameters; roof shape, orientation, covering (polyethene), and ventilation, on their temperature, relative humidity (RH), vapour pressure deficit (VPD), and cooling load. It was found that the most suitable roof design and orientation was the split-gable roof design with the ventilation switched on and 0o (E-W) orientation that had the lowest mean temperature of 24.12 oC and the least cooling demand of 454.59W. While the tunnel greenhouse had the highest cooling load of 21.30 kW. The split-gable greenhouse had. Also, the RH and VPD in the split-gable greenhouse with ventilation were within the acceptable ranges of 50-75% and 0.8 and 1.1 kPa, respectively, for successful greenhouse crop production. The developed models can aid greenhouse farmers in knowing the cost-benefit of a greenhouse before venturing into greenhouse agriculture in the tropical regions.

Akulturasi Arsitektur Kolonial terhadap Perbedaan Iklim di SDN Ditotruman Lumajang dan Rumah Dinas Bakorwil Madiun

<p><em><span lang="EN-US">The phenomenon of acculturation between Dutch and Indonesian cultures occurs a lot in colonial cultural heritage objects. This condition is a description of a Dutch building during the colonial period. Differences in climate are fundamental between the Netherlands and Indonesia, colonial buildings in Indonesia exist as a form of adaptation to the climate in Indonesia. Adaptations to colonial buildings in the form of openings, roof shapes, and ceiling heights. Acculturation can be seen in spatial patterns, and column shapes. The method in this study is descriptive qualitative, and data collection is a literature study related to colonial architecture. The objects in the field have colonial architectural characteristics in the exterior and interior elements. The purpose of this research is to analyze the architectural elements of colonial architecture in Indonesia. The results of the research can add insight into the forms of adaptation to climate in colonial architecture.</span></em></p>

Front face shaping of the inner wall tiles in the COMPASS Upgrade tokamak

The central column of the COMPASS Upgrade tokamak, where the plasma discharges will be started and shut down, is covered by a continuous first wall composed of 8 bulk tungsten guard limiters with recessed Inconel tiles in between. In diverted configurations, the plasma will be limited for a short duration (∼0.2 s–0.4 s) during the plasma current ramp-up and ramp-down phases but high heat fluxes due to short power decay lengths are foreseen. An adapted shaping is therefore needed to spread the heat loads over a maximum area. A novel method taking into account the different magnetic equilibria and the incident angle of the field lines was used to design a roof shape able to ensure a constant heat flux on the toroidal direction, accounting for the λqnear−SOL and λqfar−SOL. Due to the diversity of plasma scenarios considered on COMPASS-U, the optimized shape of the inner wall tiles strongly differs from one scenario to another, thus a compromise has to be found among all foreseen scenarios. The tile shaping also needs to take into account possible short wave misalignments. Calculations with the 3D magnetic field line tracing code PFCFlux validates the design, confirming the constant toroidal profile of deposited heat flux for the COMPASS-U workhorse scenarios, or slightly decreasing or increasing heat flux profiles (from the center to the sides of the tile) for scenarios with smaller or higher λqnear−SOL, respectively, within the expected large range (1.7 mm<λqnear−SOL<5 mm), but still providing acceptable loads. Estimated heat fluxes are in the range of 5 MW/m2 to 35 MW/m2 on the 8 guard limiters, receiving 70%–80% of the power deposited to the inner wall. In case of shortwave misalignments up to 0.5 mm in the radial direction, calculations show that leading edges are still protected, confirming the robustness of the design.

Numerical simulation of hydrogen leakage diffusion in seaport hydrogen refueling station

Ningbo's seaport hydrogen refueling station was used as the research object. The effects of different leakage angles, wind direction, roof shape, leakage hole diameters, temperature, and humidity on the diffusion of hydrogen leakage were studied by numerical simulation. The influence of leakage angle on hydrogen leakage is mainly reflected in the presence or absence of obstacles. The volume of the flammable hydrogen cloud was reduced by 31.16%, and the volume of the hazardous hydrogen cloud was reduced by 63.22% when there was no obstacle. The wind direction can significantly impact hydrogen leakage, with downwind and sidewind accelerating hydrogen discharge and reducing the risk. At the same time, headwind significantly increases the volume of the flammable hydrogen cloud. Compared with no wind, the volume of the flammable hydrogen cloud increased by 71.73% when headwind, but the volume of the hazardous hydrogen cloud decreased by 24.00%. If hydrogen shows signs of accumulation under the roof, the sloping roof can effectively reduce the hydrogen concentration under the roof and accelerate the hydrogen discharge. When the leakage angle θ = 90°, the sloping roof reduced the volume of the flammable hydrogen cloud by 11.74%. The leakage process was similar for different leak hole diameters in the no wind condition. The inverse of the molar fraction of hydrogen on the jet centerline was linearly related to the dimensionless axial distance of the jet in different cases. Using a least squares fit, the decay rate was obtained as 0.0039. In contrast, temperature and humidity have almost no effect on hydrogen diffusion. Hydrogen tends to accumulate on the lower surface of the roof, near the roof pillars and the hydrogen dispenser. In this paper, a set of hydrogen detector layout schemes was developed, and the alarm success rate was verified to be 83.33%.

Typology of Malay Traditional Building Construction Case Study: Bawi Malay House In Kampung Empat Balai, Kampar

Kampung Empat Balai is one of the old villages in Kuok District, Kampar Regency. The kampung comprises traditional Malay houses as cultural heritages that urge to preserve. The house has a unique roof shape and carvings pattern. However, the house is endangering due to a lack of maintenance. This research has aimed to identify the construction of houses that belong to the Bawi ethnic group people. A qualitative descriptive approach has been carried out to investigate and analyse this Malay house. This research found that the Bawi's house has a curving roof type which is known as part of the Lotiok roof type. This stilt house has a structural system in the form of a series of line elements with non-rigid joints that bind each other using notches and pegs as a connection system that is anticipated for earthquakes. Materially, this Bawi'House uses wooden-based materials throughout its construction systems, such as floors, walls, columns, girder beams and roof trusses.Malay house; traditional construction; lontiok roof; wooden-based materials

The Effects of Roadside Buildings Roof Shapes and Tree Plantings on the Vehicle Exhaust Gas Pollution Dispersion in the Urban Street

In this study, the effects of roadside building roof shapes and roadside tree plantings on the dispersion of vehicle exhaust gas pollution in the urban street have been carefully explored. Three typical roof shapes, i.e., flat, triangle and round shapes, are considered in the present work. Firstly, the numerical simulations of air pollution transport in the atmospheric turbulent boundary layer with/without the vegetation canopy have been performed using Computational Fluid Dynamics (CFD). Secondly, the mean flow patterns and the distribution of turbulent kinetic energy (TKE) are then examined. Finally, the concentrations of the air pollution have been carefully explored. It is found that the triangle roof could result in a lower concentration of air pollution in the street canyon. The existence of the roadside trees could decrease the air pollution concentration, although its influence is much weaker than the roof shape. It is also found that the concentration of air pollution is quite related to the flow pattern and TKE distribution. This study could provide helpful guidance on the urban planners on the design of the urban street in the future.

An accessible experiment to assess the impact of shapes of buildings and roofs on wind resistance

Hurricanes cause extensive amounts of damage in coastal communities each year. Rebuilding is costly, and the impact of hurricanes can be alleviated by mitigating the destruction to buildings. As such, buildings that are resistant to high winds are the key to increasing the resilience of communities to hurricanes. Here, we designed an accessible experiment to evaluate the effects of house and roof shape on wind resistance. We built four types of house models: box-shaped houses with pyramid hip roofs, box-shaped houses with flat roofs, round houses with pyramid hip roofs, and round houses with flat roofs. To evaluate the stability of these house models, we applied strong winds using a leaf blower. We determined stability by measuring the distance between the leaf blower and the house models when they were blown away, and the time it took for the houses to be blown away if the distance was 0 cm. The smaller the distance and the longer the time, the more resistant the houses are to strong winds. We found round houses were more resistant to strong winds than box-shaped houses, and houses with pyramid hip roofs were more resistant to strong winds than houses with flat roofs if other attributes of the houses were kept the same. Furthermore, we found roof shape was more important than house shape among the different combinations of house shapes and roof shapes we studied. Our study provides scientific data to facilitate policy making in improving coastal resilience, particularly through updating building codes that account for house and roof shape.

Numerical investigation of thermal buckling and post-buckling behavior of an EN AW 6016-T4 car roof assembled in a steel body-in-white

The automotive industry is undergoing significant changes driven by factors such as reducing carbon dioxide emissions, advancing technology, evolving regulations, and the emergence of new energy sources. Lightweight materials, particularly aluminum alloys, are being extensively researched and integrated into vehicles to reduce weight and improve performance. However, the heating process during vehicle production can cause thermal buckling in thin aluminum alloy structures, affecting their appearance and quality. While thermal buckling has been studied in other industries, research in the automotive sector, particularly for non-structural parts like car roofs, is limited. This study uses numerical simulation to predict thermal buckling and post-buckling behavior of a EN AW 6016-T4 alloy car roof assembled in a predominantly steel body-in-white. The research findings indicate that roof buckling occurs at a relatively low temperature difference of approximately 60 °C, which is lower than the maximum temperatures experienced during the painting phases in the automotive industry. Consequently, undulations in the roof's shape become apparent, underscoring the importance of design modifications to ensure visual conformity. Validation through physical testing confirms the model's accuracy, providing valuable insights for designing lightweight structures with improved performance and aesthetics.

A DES study of the flow around a full-scale train under crosswind condition

A numerical study on the flow around a full-scale train subjected to crosswind has been conducted on the basis of detached-eddy simulation (DES). Finite-volume method is applied to unstructured mesh generated around a three-car-train model whose running speed is fixed to 120 km/h while the crosswind speed is set to 5 m/s,15 m/s, and 25 m/s. A clear longitudinal vortex structure is recognized in the case of the crosswind speed of 25 m/s, where two longitudinal vortices are evolved respectively from the roof and floor of the head car (roof-edge and floor-edge vortices), forming a characteristic vortex pair. This longitudinal vortex structure around the head car is discussed with a focus on its non-trivial role in the side-force mechanism. Our simulation suggests a causal association between these two vortices, which implies an importance of optimum designing of the underfloor equipment in addition to the roof and head shapes of the head car.

The influence of attics space geometrical shape on ignition and flashover stages in residential building fires in dense settlements

As an artificial physical place, residential building is formed by various functional spaces, such as residential space and the space between the ceiling space and the roof, i.e. the attics. The phenomenon of fires in residential buildings in densely populated areas is suspected of having occurred in the attics. Hitherto, research on the fire space model concerning the stages of ignition and flashover usually employs the Steckler's compartment model in the form of a cube/box. On the contrary, the fire model with a triangular roof shape is still rarely studied. The purpose of this study was to analyse the influence of the geometric shape of the attics on the ignition and flashover stages in residential fires located in densely populated settlements. This study employs an experimental method by conducting scaled experiments of the geometric model of the ceiling space in the form of a triangular gable roof and shed roof, focusing on the ignition and flashover stages. The results showed that the ignition stage in the gable roof and shed roof models occurred in the 3rd and 4th minutes with a temperature ranging from 270 ⁰C- 476 ⁰C. The flashover stage also occurred in the 5th to 9th minute with regular results close to 500 ⁰C.

A numerical study of the effect of building height and shape on amount of wind energy available on the roof

With the aid of renewable energy, carbon footprints can definitely be reduced. Wind energy is such a renewable energy source because it is not depleted when used. Wind energy utilization through a wind turbine and its outstanding conversion efficiency makes any building construction economic. Building height and contour of its roof shape plays an important role in the design of wind turbine placement. In this research, a numerical study was conducted to estimate wind speed, the intensity of turbulence, and wind-specific energy available on the surface of several different shapes and heights of buildings designed using the ANSYS program. The main objective is to choose the appropriate location for installing a wind turbine on the roof of the building to convert wind energy into electrical energy. In order to ensure the objective, numerical modeling of the reference building along with the wind effect on its roof was validated with experimental reference values. ANSYS software was used for numerical modeling of the building with different shapes of the roofs along with different heights respectively and comparing the results of the cases studied on the surface of the building, an optimal design shape was chosen that gives the largest amount of wind that can be harvested, by adopting the value of the highest speed and the intensity of the minimum turbulence as a measure of comparison.

Drying edible jellyfish (Lobonema smithii) using a parabolic greenhouse solar dryer

Thailand is one of Southeast Asia’s top exporters of salted edible jellyfish. Jellyfish products are generally exported in the form of semi-dried jellyfish. A recent survey on jellyfish distribution in coastal areas in the Gulf of Thailand and the Andaman Sea indicated that most edible jellyfish in the area belong to Lobonema smithii and Rhopilema hispidum. Drying is an alternative method to preserve food products. In this work, parabolic roof shape greenhouse solar drying of edible jellyfish (Lobonema smithii) was studied, and the quality of the dried jellyfish was assessed. The solar dryer system has a 300 kg loading capacity for jellyfish and the resulting dried and rehydrated jellyfish products are described. The moisture content of dried jellyfish decreased to 7.05-11.70% (wb) from 91-92% (wb) after drying for three days and the protein, fat, crude fibre, ash, and carbohydrate content of the dried jellyfish were 68.68%, 0.74%, 0.43%, 9.27%, and 4.67%, respectively. The moisture of the rehydrated jellyfish increased to 37.67-39.07% (wb) after soaking in distilled water for 5 hrs. In terms of colour, the rehydrated jellyfish products were found to be highly similar to salted jellyfish products.

Effects of sea-breeze natural ventilation on thermal comfort in low-rise buildings with diverse atrium roof shapes in BWh regions

The purpose of this study is to evaluate the effects of the atrium ceiling on catching sea breeze, indoor thermal comfort, and natural ventilation in the buildings in coastal areas with BWh climate during warm seasons. This study was further sought to forerun the internal thermal comfort through Fanger's theory considering environmental and turbulence parameters in atrium-roofed low-rise buildings in BWh coastal areas, assuming that the results would be practical for engineers and designers in BWh onshore regions. To achieve these purposes, 12 atrium ceiling shapes have been studied in a three-story building in Bushehr (Iran) with BWh climate. Specimens were simulated in Ansys Fluent for 2:00 p.m. on 29th July as the hottest day of the year. The experimental data of wind tunnels have been employed to validate the results, with an observed 1.5% difference between CFD and experimental findings that confirm the validity of the data simulated. Specimen #12 which has a cube-shaped roof with a blade with distance on atrium output to create air pressure difference had the highest volumetric flow rate from the atrium outlet (2 m3 s−1) and the best condition in terms of natural ventilation. In addition, specimens #12 and #3 which has a cube-shaped form, and the atrium outlet was placed on the roof maintained the best performance in terms of thermal comfort than other specimens, with PMV values of 2.6 and 2.4, respectively. Furthermore, the PMV values are correlated with air velocity (r = 0.61), dry temperature (r = 0.72) and air pressure (r = 0.52) as the environmental parameters. The correlation coefficient has been calculated between PMV and Ti (r = 0.61), Tke (r = 0.45), and Tdf (r = 0.37). PPD had a substantial correlation with velocity (r = 0.71), temperature (r = 0.6) and air pressure (r = 0.45). Furthermore, the highest correlation coefficient has been observed between PPD and Ti (r = 0.54) and Tke (r = 0.37), and the least correlation has been seen between PMV and Tdf as r value equals 0.27.