Hip Roof Buildings Research Articles

DETERMINANTS OF THE OPTICAL ILLUSIONS EFFECT ON THE DALEM AGENG PRABAYEKSA ROOF, DALEM MANGKUBUMEN AREA, YOGYAKARTA

Javanese buildings can be understood both physically and non-physically, one of them is the Dalem Ageng Prabayeksa which is in the Dalem Mangkubumen complex. This building has the most important and sacred position in the complex with the uniqueness of the hip roof (limasan), which cannot be found in other hip roof buildings. This study focuses on optical illusions that occur on the roof of the building in front (south) and rear (north) views using explorative descriptive methods. Optical illusions that affect visual perception occur because of the imaginary perspective lines formed from the diagonals of the roof of the building so that an illusion is created that make the roof of the building look wider and taller than it should be. The roof of the building is also formed from proportions that are in accordance with the reference for the building as a house and the building as a place of worship (temples) which supports how optical illusions can occur so that a visual perspective and meaning behind the design of the roof appears which makes sense and is in line with the position of the Dalem Ageng Prabayeksa building as the most important and sacred building in the Dalem Mangkubumen complex.

Large-Scale Wind Testing on Roof Overhangs for a Low-Rise Building

Roof overhangs are prone to wind damage because they are subject to wind load at both the upper and bottom surfaces. Wind standards assume that the pressure at the bottom covering of a roof overhang will be the same as the external pressure coefficient on the adjacent wall surface. A large-scale experimental campaign was carried out at the Wall of Wind (WOW) Research Experimental Facility to investigate the validity and possible limitations of such assumptions. The experimental setup considered two 1:10 scaled models [0.61 m (2 ft) and 1.83 m (6 ft) inclined overhangs with a soffit] of a low-rise hip roof building with roof slope 4:12, eave height of 7.5 m (24 ft), and horizontal dimensions of 12.2 m (40 ft)× 15.24 m (50 ft). The two models were tested for open terrain for 40 wind directions (WDs). The study provided information on pressure variations at the top and bottom surfaces of overhangs, adjacent roof areas, and underneath walls. Pressure and correlation coefficients were generated between soffits and underneath walls to quantify the effect of overhang width. The research showed that the 0.61 m (2 ft) overhang experienced higher suction coefficients at the edges compared to the 1.83 m (6 ft) overhang. In addition, the results confirmed that, for both configurations, soffit positive pressure coefficients may be assumed to be equal to the adjacent wall external pressure, as stated by a common standard, while this might not be applicable for negative pressure coefficients. Correlation and regression analyses between soffit pressure taps and wall upper taps show that the 1.83 m (6 ft) soffit appeared to be less correlated with the wall upper taps, compared to the 0.61 m (2 ft) soffit. Finally, area-averaged pressure coefficients for overhangs and adjacent roof areas were compared to the provisions in one standard for each specified zone, and differences were found.

Investigation of the Effects of the Classification of Building Stock Geometries Determined Using Clustering Techniques on the Vulnerability of Galvanized Iron Roof Covers Against Severe Wind Loading

In the risk assessment of buildings against severe wind loading, the vulnerability component of risk is highly affected by the geometry of the structure. Parameters such as the height, width, length, aspect ratio, eaves length, and roof slope, affect the pressure distribution around the structure, which in turn affects the response of galvanized iron (GI) roof covers to wind loadings. In developing countries, there is a large variation in the building geometric parameters which poses a challenge in determining the archetypes that would best represent the building population for risk assessment. This paper aims to develop and propose a method in determining the building archetypes based on its geometry. The hierarchy for grouping of geometries started with the roof type. These were gable type roofs, mono-slope type roofs and hip type roofs. The building datasets per roofing type were then clustered using a two-stage approach involving Hierarchical and K-means clustering which were based on the aforementioned geometric parameters. These algorithms will aggregate buildings having similar sets of geometric parameters but the number of clusters must be specified. In order to determine the optimal number of clusters, this study employs various validation tools or measures namely – dendrograms, variation of the variance ratio criterion (VRC) across number of clusters, validity indices such as, Davies Bouldin, Silhouette and Calinski Harabasz, and the elbow method. Although guided by these validation methods, the final selection of the number of clusters were determined considering computational time and resources. To define an archetype, the mean values of each parameter per cluster were selected. Resulting to 5, 3, and 3, archetypes for gable, hip, and mono-slope roof buildings, respectively. The selection of the archetype was further evaluated by investigating its effects on the vulnerability of GI roof covers in order to see how distinct each archetype would behave. A Kruskal Wallis test on the vulnerability curves of the different building archetypes showed that there is a significant difference between vulnerability curves under a roof shape category, which reinforces the distinction between the selected building archetypes.

Effects of roof geometry on tornado-induced structural actions of a low-rise building

Continued loss of property and lives in tornadoes including the 23-person death toll resulting from the Lee County AL tornado on March 3rd 2019 reflects the ever-present vulnerability of the community to tornadoes, and necessitates improvement in building standards for more accurately predicting such extreme loads. This article investigates effects of three roof geometries: flat, gable, and hip, on maximum overall and local wind-induced uplift, shear and moment on low-rise buildings by a translating tornado. To explore local structural actions, maximum of five frames along the longer horizontal dimension of each building were considered. Maximum structural actions, independent of building orientation and its distance to the center of the tornado-track were calculated, with results showing that a flat roof building experiences the largest amount of overall uplift, overall shear, local uplift, and moment. Only local shears on a hip roof building were equal to or larger than those of a flat roof building for same frame locations. This study also showed that gable and hip roof buildings experience moments of similar magnitudes, whereas a gable roof performs better against shear and a hip roof performs better against uplift. Experimentally-calculated structural actions were compared with predictions of ASCE7-16, with results showing that ASCE7-16 under-predicts overall and local uplifts, and moments, while over-predicts shear for all roof geometries. The maximum under-prediction of overall and local uplifts using ASCE7-16′s procedure were 41% and 55%, respectively, both for a gable roof building. Internal frames experienced maximum under-prediction of uplifts, which makes them a vulnerable location of low-rise buildings that are built in compliance with ASCE7-16 building standard. Finally, correction factors were introduced to modify and improve accuracy of ASCE7-16 in prediction of structural actions on low-rise buildings with different roof geometries.

Mitigation of Aerodynamic Uplift Loads Using Roof Integrated Wind Turbine Systems

Coastal areas of the US are affected by extreme wind events, including hurricanes. Roofs are the most vulnerable building components as they are often damaged by high wind uplift forces acting on the edges and corners. This study investigates the application of a mitigation strategy, in the form of an Aerodynamics Mitigation and Power System (AMPS) (US Patent, Gan Chowdhury et al., Patent Number: US 9,951,752 B2, April 2018), designed to simultaneously reduce wind damage and provide power to buildings. The system consists of horizontal axis wind turbines, integrated to roof edges with or without gutters. Four sets of testing on a flat roof low rise building model (without gutters) -- including a bare deck configuration (i.e. without AMPS) and three cases where the roof corner was fitted with AMPS -- were conducted at the Wall of Wind Experimental Facility at Florida International University. In one of the configurations, the wind turbines were placed slightly above the roof edge, while in the other two configurations, the turbines were placed closer to the roof edge. Wind directions tested ranged from 0o to 90o (considering roof geometric symmetry). Estimation of area-averaged mean and peak pressure coefficients were made for various locations on the roof for the three different configurations, and compared with the case of no mitigation. Results show that for wind directions tested, significant reduction in mean and peak pressure coefficients (reduced suction) were obtained in those cases where the wind turbines were placed closer to the roof edge as compared to the bare roof deck case. Flow visualization studies showed that the turbines helped to disrupt the conical vortices caused by cornering winds, thereby reducing the wind uplift forces on the roof. This study shows that the AMPS can be utilized to prevent wind-induced damage to the roof. Future research will include estimation of the: (1) potential wind energy production using the mitigation system under various wind conditions, (ii) effectiveness of AMPS in mitigating wind loading on other kinds of buildings (e.g., gable and hip roof buildings), and (iii) load transferred from the system to the roof.

An experimental study to assess the effect of soffit louvered vents on wind loads and wind driven rain intrusion on low rise buildings

Wind-driven rain (WDR) intrusion in buildings during hurricanes often leads to significant damage to building interior and contents, causing major losses. Many buildings in hurricane-prone U.S. coastal states are fitted with soffit vents with louvers that are designed to close during high winds and reduce rain intrusion. This paper focuses on the topic of WDR intrusion through soffit vents and, in particular, studies the effects of louvered soffit vents on (i) reduction of water intrusion, and (ii) overall aerodynamic loading of buildings’ roofs. A gable and a hip roof building retrofitted with open and closed vents were tested at the Wall of Wind (WOW) experimental facility. WDR intrusion studies were carried out only on the hip roof building, while wind pressure distributions were estimated for the gable and hip roof buildings. Results from the WDR intrusion study indicate a marked reduction in water intrusion for the closed vent roofs. Moreover, the net mean and peak pressure coefficients for the closed vent roofs are reduced in magnitude (less suction) compared to the open vent roofs. Future research is recommended to study the effect of different vent sizes and locations, besides considering other roof types (e.g. mono-slope).

Distribution of wind-driven rain deposition on low-rise buildings: Direct impinging raindrops versus surface runoff

Wind-driven rain (WDR) effects on various components of a building facade are dependent on the total volume of rainwater deposition. The total volume of WDR deposition at a specific location on the building facade has contributions from both directly impinging raindrops and accumulated surface runoff. The distribution of WDR deposition over the building surface is dependent on the nature of the storm and on the aerodynamic shape of the building. This paper presents an experimental study conducted to investigate the distribution of WDR deposition on the external facade of low-rise buildings. Two parameters that quantify the distribution of direct impinging raindrops and surface runoff rainwater over the building surface—rain admittance factor (RAF) and surface runoff coefficient (SRC), respectively—were measured separately under simulated WDR conditions. Test-based RAF and SRC datasets were developed for three types of building models (gable, flat, and hip-roof buildings) tested for various wind directions. Test results indicated a higher concentration of direct impinging raindrop deposition on windward vertical surfaces of the building when compared to the horizontal roof components. The test results also demonstrated that the leading edge/corner regions of the buildings received less volume surface runoff rainwater, and the rainwater accumulation increases toward the leeward surfaces. The test-based RAF and SRC data developed in this work may be used for estimation of WDR deposition on façades of low-rise buildings as well as water intrusion through building envelope breaches, openings, and defects.

Partial turbulence simulation and aerodynamic pressures validation for an open-jet testing facility

This paper describes partial turbulence simulation and validation of the aerodynamic pressures on building models for an open-jet small-scale 12-Fan Wall of Wind (WOW) facility against their counterparts in a boundary-layer wind tunnel. The wind characteristics pertained to the Atmospheric Boundary Layer (ABL) mean wind speed profile and turbulent fluctuations simulated in the facility. Both in the wind tunnel and the small-scale 12-Fan WOW these wind characteristics were produced by using spires and roughness elements. It is emphasized in the paper that proper spectral density parameterization is required to simulate turbulent fluctuations correctly. Partial turbulence considering only high frequency part of the turbulent fluctuations spectrum was simulated in the small-scale 12-Fan WOW. For the validation of aerodynamic pressures a series of tests were conducted in both wind tunnel and the small-scale 12-fan WOW facilities on low-rise buildings including two gable roof and two hip roof buildings with two different slopes. Testing was performed to investigate the mean and peak pressure coefficients at various locations on the roofs including near the corners, edges, ridge and hip lines. The pressure coefficients comparisons showed that open-jet testing facility flows with partial simulations of ABL spectrum are capable of inducing pressures on low-rise buildings that reasonably agree with their boundary-layer wind tunnel counterparts.

Knowledge-Based Modeling of Buildings in Dense Urban Areas by Combining Airborne LiDAR Data and Aerial Images

In this paper, a knowledge-based algorithm is proposed for automatically generating three-dimensional (3D) building models in dense urban areas by using airborne light detection and ranging (LiDAR) data and aerial images. Automatic 3D building modeling using LiDAR is challenging in dense urban areas, in which houses are typically located close to each other and their heights are similar. This makes it difficult to separate point clouds into individual buildings. A combination of airborne LiDAR and aerial images can be an effective approach to resolve this issue. Information about individual building boundaries, derived by segmentation of images, can be utilized for modeling. However, shadows cast by adjacent buildings cause segmentation errors. The algorithm proposed in this paper uses an improved segmentation algorithm (Susaki, J. 2012.) that functions even for shadowed buildings. In addition, the proposed algorithm uses assumptions about the geometry of building arrangement to calculate normal vectors to candidate roof segments. By considering the segmented regions and the normals, models of four common roof types—gable-roof, hip-roof, flat-roof, and slant-roof buildings—are generated. The proposed algorithm was applied to two areas of Higashiyama ward, Kyoto, Japan, and the modeling was successful even in dense urban areas.

Component and Cladding Wind Loads for Soffits

The wind induced failure of soffits of low rise structures is a failure mechanism commonly observed in post hurricane damage investigations. The failure of the soffits has the potential to allow both wind and water to enter the attic space of the building. The current US national wind loading standard (ASCE 7) provides no guidance as to the wind load requirements for the design of soffits. In order to address this deficiency, wind tunnel tests on 1:50 scale models of one-, two-, and three-story hip and gable roof buildings were performed where measurements of the wind induced pressures and suctions on the soffits, roofs, and walls were obtained. The wind tunnel tests were performed in open and suburban terrain conditions, with and without surrounding buildings in place. The results of the tests clearly show that the soffit pressures are nearly fully correlated with nearby wall pressures, and a simple and accurate solution to the soffit loading deficiency in ASCE 7 is to prescribe that the component and cladding pressures for use in the design of soffits be identical to the component and cladding loads used for the design of wall components.

Three-dimensional linearised Euler model simulations of sound propagation in idealised urban situations with wind effects

A three-dimensional numerical time-domain model based on the linearised Euler equation is applied to idealised urban situations with elongated, isolated buildings beside a straight street with sound emissions. The paper aims at the investigation of principle relationships between the source–receiver geometry (street and building facades) and sound propagation under the consideration of ground and wind. By applying cyclic lateral boundary conditions for either one or both horizontal co-ordinates, two different idealised urban environments were considered: a single street and parallel streets. Numerical experiments were performed to elaborate the effects of different roof types, ground properties, wind flow, and turbulence in both urban environments with the focus on the back facades (‘quiet’ sides) of the buildings. As a result it was found that the back facades of flat-roof buildings are quieter than those of hip roof buildings despite equal cross-cut areas. The wind effect (resulting in quieter upwind and louder downwind facades) is more pronounced for hip-roof buildings. In the case of parallel streets upwind facades are slightly louder than downwind facades because they are simultaneously exposed to downwind propagating sound from the next parallel street.

Wind pressures on low-rise hip roof buildings

Seven hip roof building models for , , , , , and roof pitch with large overhangs of 1.1 m were tested in a wind tunnel at the university of Roorkee, India to investigate wind pressure distributions over hip roofs for various roof pitch and wind direction. The results show that the roof pitch and wind direction do significantly affect the magnitude and distribution of the roof pressures. The roof pitch has been found to experience the highest peak suctions at the roof corners amongst the seven hip roofs tested. Pressures on , and hip roofs are comparable with those reported by Xu and Reardon (1998). Meecham et al. (1991) for hip roof is compatible with hip roof of the present study. Holmes`s works (1994) on gable roof have also been compared with the present work. Zoning for codification has also been attempted since IS875 (Part-3) does not include this information. A comparison for design value has also been made with BRE Report No. 346.

Effect of geometry on wind pressures on low-rise hip roof buildings

A Texas Tech University building model at a geometric scale of 1:50 was tested under simulated atmospheric boundary layer conditions for calibration of this experiment. Overall six hip roof building models with roof pitch of 30° were constructed on 1:50 scale. Out of six, three were with overhang ratio 0.17, 0.26 and 0.38 (overhangs 0.5, 0.75 and 1.1 m) respectively for constant height aspect ratio 0.4 and the rest three were with height aspect ratio 0.4, 0.5 and 0.6 m, respectively, for constant overhang ratio 0.38. Overhang ratios were varied from 0.17 to 0.38 while height aspect ratios varied from 0.4 to 0.6 in the wind tunnel testing to investigate wind pressure distribution over hip roofs and the effect of overhang and aspect ratios on roof pressures. Both the overhang and aspect ratio were found to influence the magnitude and distribution of pressures on hip roof. The model with overhang ratio 0.26 amongst the first three models and the model with aspect ratio 0.6 amongst the next three models have been found to experience maximum negative peak pressure ( C pmin).

Interference effects on wind loads on low-rise hip roof buildings

The Natural wind in the wind tunnel was simulated at the University of Roorkee (India) on the basis of full/model-scale comparison. For this, the Texas Tech University (TTU) building model was fabricated on a geometric scale of 1:50 and tested in the simulated wind for comparison of the pressures with full-scale values. A hip roof building model (geometric scale 1:50) of plan dimensions 280 mm×140 mm×58 mm (eave height) with 30° roof slope was selected as the test building (T.B.) so as to examine interference with a similar building as well as three similar buildings placed on the upstream side at fifteen different locations ( Fig. 2). A quadrant portion of the model roof was divided into ten different zones to see the effect of interference at critical roof positions. Significant effects have been observed.

Wind-Induced Fatigue Loading and Damage to Hip and Gable Roof Claddings

Wind-induced fatigue loading and damage to roof claddings on gable-roof and hip-roof buildings are investigated in this study through both wind tunnel tests and computer analyses. The magnitude and distribution of wind pressures on both roofs are first measured at different wind directions. Fatigue characteristics of wind pressures are identified based on a rainflow count method for each tap at its critical wind direction in which its largest negative pressure occurs. Total fatigue loading at each tap on both roofs is then computed using the obtained fatigue characteristics and information on wind climate. Finally, fatigue damage to screw-fastened light-gauge steel roof sheetings of different profiles is estimated in terms of previously obtained S-N curves and a modified Miner's rule. The distributions of fatigue damage index over both roofs show that under the same strong winds, fatigue damage to the hip roof cladding is much less severe than that to the gable roof cladding. For each type of roof configu...

Study of wind forces on low-rise hip-roof building

A comprehensive numerical study of wind effects using Computational Fluid Dynamics (CFD) techniques on the low-rise hipped roof building is presented in this paper. Two Reynolds Averaged Navier–Stokes Equations (RANS) techniques such as the Standard k -e turbulence model and the Renormalization group (RNG) k - ε turbulence model were adopted in this study to predict the wind loads and the flow patterns around the hip-roof building. The computed wind pressure coefficients on the roof of the hip-roof buildings were compared with the wind-tunnel data. It was found that the results obtained using RNG k - ε turbulence model are in good agreement with that of the wind-tunnel data than the Standard k - ε turbulence model. It was also found that the CFD techniques are an effective and alternative tool, less time consuming, easy-to-handle, as well as low cost approach for evaluation of wind effects in comparison to wind-tunnel experiments, using the above turbulence models and with the available resources.Keywords: CFD, Computational Fluid Dynamics, Wind force, Hip-roof building, Low-rise building, RANS approach, Wind Engineering.