Hip Roof Research Articles

Effects of roof slope and wind direction on wind pressure distribution on the roof of a square plan pyramidal low-rise building using CFD simulation

Roof shape and slope are both important parameters for the safety of a structure, especially when facing wind loads. The present study demonstrates the pressure variations due to wind load on the pyramidal roof of a square plan low-rise building with 15% wall openings through CFD (Computational Fluid Dynamics) simulation. Many studies on roofed structures have been performed in the past; however, a detailed review of the literature indicates that the majority of these studies focused on flat, hip, gable and spherical roofs only. There is a lack of research that analyses these effects on pyramidal roof buildings. ANSYS (Analysis System) ICEM (Integrated Computer Engineering and Manufacturing)-CFD and ANSYS Fluent commercial packages have been used for modelling and simulation, respectively, and ANSYS CFD Post was used to obtain the results. A realizable k–ε turbulent model was used for the pressure distribution on the roof of the building model. In the present study, twenty-four models with different roof slopes (α), i.e. 0°, 10°, 20°, and 30°, with various wind incidence angles (ϴ), i.e. 0°, 15°, 30°, 45°, 60° and 75° were investigated. The influence of roof slope and wind incidence angle are analysed in this study. Results have been represented through pressure coefficient (Cp) contours on the roof surface and velocity streamlines of the flow field of the different cases. The optimization of the roof slope may be achieved by considering different wind incidence angles for buildings so that they may better withstand wind force in a specific area. When wind pressure coefficients from building models with openings were compared with pressure coefficients from building models without openings, it was found that the pressure coefficients for building models without openings are almost twice or three times that of the pressure coefficients for models with openings.

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.

Effects of curved slopes, high ridges and double eaves on wind pressures on traditional Chinese hip roofs

Traditional Chinese hip roofs have some special features, including curved slopes, high ridges and double eaves, which are different from conventional linear-sloped hip roofs. In order to investigate wind pressure characteristics acting on traditional Chinese hip roofs, wind tunnel tests are carried out in a boundary layer wind tunnel. Mean, fluctuating and peak wind pressures acting on traditional Chinese hip roofs have been examined and compared with those on conventional hip roofs, and the effects of the curved slopes, high ridges and double eaves are investigated.Mean, fluctuating and peak wind pressure coefficients of traditional curved Chinese hip roofs are larger in magnitude than those of conventional linear protruded-ridge hip roofs. The high ridges of conventional protruded-ridge hip roofs have significant effects on the distributions of mean and peak wind pressure coefficients, compared with conventional non-protruded-ridge hip roofs. For traditional Chinese hip roofs with double eaves, mean, fluctuating and peak wind pressure coefficients on the upper surfaces of the higher layer are significantly decreased in magnitude. Three components of mean and peak wind force coefficients acting on the roofs and the area-averaged net wind pressure coefficients acting on the roof slopes are also discussed and compared for the above cases.

Wind Pressures on 4∶12-Sloped Hip Roofs of L- and T-Shaped Low-Rise Buildings

AbstractA comprehensive wind tunnel experimental study for 4∶12-sloped hip roofs of L- and T-shaped low buildings was carried out in a simulated open terrain exposure to examine wind load character...

Framing Failures in Wood-Frame Hip Roofs under Extreme Wind Loads

Wood-frame residential roof failures are among the most common and expensive types of wind damage. Hip roofs are commonly understood to be more resilient during extreme wind in relation to gable roofs. However, inspection of damage survey data from recent tornadoes has revealed a previously unstudied failure mode in which hip roofs suffer partial failure of the framing structure. In the current study, evidence of partial framing failures and statistics of their occurrence are explored and discussed, while the common roof design and construction practice is reviewed. Two-dimensional finite element models are developed to estimate the element-level load effects on hip roof trusses and stick-frame components. The likelihood of failure in each member is defined based on relative demand-to-capacity ratios. Trussed and stick-frame structures are compared to assess the relative performance of the two types of construction. The present analyses verify the common understanding that toe-nailed roof-to-wall connections are likely to be the most vulnerable elements in the structure of a wood-frame hip roof. However, the results also indicate that certain framing members and connections display significant vulnerability under the same wind uplift, and the possibility of framing failure is not to be discounted. Furthermore, in the case where the roof-to-wall connection uses hurricane straps, certain framing members and joints become the likely points of failure initiation. The analysis results and damage survey observations are used to expand the understanding of wood-frame residential roof failures, as they relate to the Enhanced Fujita Scale, and provide assessment of potential gaps in residential design codes.

A city-scale roof shape classification using machine learning for solar energy applications

Abstract Solar energy deployment through PV installations in urban areas depends strongly on the shape, size, and orientation of available roofs. Here we use a machine learning approach, Support Vector Machine (SVM) classification, to classify 10,085 building roofs in relation to their received solar energy in the city of Geneva in Switzerland. The SVM correctly identifies six types of roof shapes in 66% of cases, that is, flat & shed, gable, hip, gambrel & mansard, cross/corner gable & hip, and complex roofs. We classify the roofs based on their useful area for PV installations and potential for receiving solar energy. For most roof shapes, the ratio between useful roof area and building footprint area is close to one, suggesting that footprint is a good measure of useful PV roof area. The main exception is the gable where this ratio is 1.18. The flat and shed roofs have the second highest useful roof area for PV (complex roof being the highest) and the highest PV potential (in GWh). By contrast, hip roof has the lowest PV potential. Solar roof-shape classification provides basic information for designing new buildings, retrofitting interventions on the building roofs, and efficient solar integration on the roofs of buildings.

Effects of roof height on local pressure and velocity coefficients on building roofs

Failures of roofing systems occur due to high local suctions on tiles or shingles, or because of a different failure mechanism triggered by high local wind velocities near the roof surface. In the latter case, the local velocity can induce positive pressures on the lip of a windward facing shingle or tile, which are transmitted underneath, adding to the external surface negative pressure and causing an increase of the net uplift force. Building codes provide estimates of the peak pressure coefficients (peak Cp) based on 3-s gust in the oncoming wind at the roof height. As an approximation, these coefficients are generally taken to be independent of roof height and exposure. This implies that wind tests of roofing system behaviour carried out at one roof height can be used to infer the system behaviour for other roof heights. One of the main objectives of the present study was to examine the validity of this approximation. Regarding the second failure mechanism discussed above, knowledge of surface wind speed is a key element to assess the uplift forces on shingles. Building codes do not address the wind velocities close to the roof surface and estimate it based on the approach wind speed in terms of a wind speed ratio. So the second objective of the present research was to examine the ratio of local wind velocity close to the roof surface to the velocity at roof height in the approach flow and investigate the effect of height on the velocity ratios. Wind tunnel tests were performed on four different gable-hip roof buildings, at various wind directions. Both surface pressures and near-surface velocities were measured and normalized with respect to upwind flow conditions at mean roof height. The results confirm that the velocity ratios and peak Cp values on the gable roof do not vary markedly with building height with no more than 10% change found at most locations. For the velocity ratios a similar conclusion was reached on the hip roof. However, for the Cp values in the corner zones of the hip roofs increases with height were identified and further investigation is recommended.

A Study on the Adjustment of Eaves Curve and Roof Length of Three-Bay-Kan Buddhist Temples with the Hipped and Gable Roof

A Study on the Adjustment of Eaves Curve and Roof Length of Three-Bay-Kan Buddhist Temples with the Hipped and Gable 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).

Wind loading on ridge, hip and perimeter roof tiles: A full-scale experimental study

Full-scale experiments were conducted to investigate wind loading on roof tiles in hip, ridge, and perimeter locations, identified from past storms as main points of damage initiation. The objectives were to: (i) provide test-based data on wind-induced loads for tiles, and (ii) evaluate characteristics of near-surface flows to assess tile loading models. The experiments included pressure measurements on the external surface and in the cavity underneath the tiles, and wind speed measurements near tile surfaces. The highest net uplift pressure (computed as external pressure minus the cavity pressure) was observed on the gable end ridge tiles. Except for a few non-critical cases, due to effects of pressure equalization net uplift was lower than external surface uplift. Mean wind speeds at tile surfaces were recorded that were up to 55% higher than the mean wind speed at mid-roof height in the approach flow. Two alternative models that use wind speeds near the tile surface to determine net design wind loads on tiles were investigated. The results showed that the models can underestimate wind loading. However, when used with appropriate parameters, the models can produce results comparable to those obtained using ASCE's external pressure coefficients in conjunction with pressure adjustment factors.

KNOWLEDGE BASED 3D BUILDING MODEL RECOGNITION USING CONVOLUTIONAL NEURAL NETWORKS FROM LIDAR AND AERIAL IMAGERIES

Abstract. In recent years, with the development of the high resolution data acquisition technologies, many different approaches and algorithms have been presented to extract the accurate and timely updated 3D models of buildings as a key element of city structures for numerous applications in urban mapping. In this paper, a novel and model-based approach is proposed for automatic recognition of buildings’ roof models such as flat, gable, hip, and pyramid hip roof models based on deep structures for hierarchical learning of features that are extracted from both LiDAR and aerial ortho-photos. The main steps of this approach include building segmentation, feature extraction and learning, and finally building roof labeling in a supervised pre-trained Convolutional Neural Network (CNN) framework to have an automatic recognition system for various types of buildings over an urban area. In this framework, the height information provides invariant geometric features for convolutional neural network to localize the boundary of each individual roofs. CNN is a kind of feed-forward neural network with the multilayer perceptron concept which consists of a number of convolutional and subsampling layers in an adaptable structure and it is widely used in pattern recognition and object detection application. Since the training dataset is a small library of labeled models for different shapes of roofs, the computation time of learning can be decreased significantly using the pre-trained models. The experimental results highlight the effectiveness of the deep learning approach to detect and extract the pattern of buildings’ roofs automatically considering the complementary nature of height and RGB information.

KNOWLEDGE BASED 3D BUILDING MODEL RECOGNITION USING CONVOLUTIONAL NEURAL NETWORKS FROM LIDAR AND AERIAL IMAGERIES

In recent years, with the development of the high resolution data acquisition technologies, many different approaches and algorithms have been presented to extract the accurate and timely updated 3D models of buildings as a key element of city structures for numerous applications in urban mapping. In this paper, a novel and model-based approach is proposed for automatic recognition of buildings’ roof models such as flat, gable, hip, and pyramid hip roof models based on deep structures for hierarchical learning of features that are extracted from both LiDAR and aerial ortho-photos. The main steps of this approach include building segmentation, feature extraction and learning, and finally building roof labeling in a supervised pre-trained Convolutional Neural Network (CNN) framework to have an automatic recognition system for various types of buildings over an urban area. In this framework, the height information provides invariant geometric features for convolutional neural network to localize the boundary of each individual roofs. CNN is a kind of feed-forward neural network with the multilayer perceptron concept which consists of a number of convolutional and subsampling layers in an adaptable structure and it is widely used in pattern recognition and object detection application. Since the training dataset is a small library of labeled models for different shapes of roofs, the computation time of learning can be decreased significantly using the pre-trained models. The experimental results highlight the effectiveness of the deep learning approach to detect and extract the pattern of buildings’ roofs automatically considering the complementary nature of height and RGB information.

Wind loads on contemporary Australian housing

Design pressures given in wind loading standards are based on wind tunnel studies conducted during the 1970s to 90s on rectangular hip and gable roofs. However, most contemporary houses have complex hip-roof geometries with a range of plan footprints. Wind tunnel model studies were carried out on representative one- and two-storey houses to determine cladding design and truss hold-down loads. These loads were compared to design loads determined from wind loading standards AS/NZS 1170.2 and AS 4055. AS 4055 gave conservative design loads in most situations, and AS/NZS 1170.2 underestimated the loads near the windward edges and ridge on the roof. AS/NZS 1170.2 does give satisfactory design loads for wall cladding and truss hold down.

Каркасы крыш и деревья теории графов

The problem of constructing roofs of many papers [1;
 6; 7; 9; etc.]. In this case, some studies suggested to use a computer
 and special programs [10; 13; 16; etc.]. The geometry of the
 efficient design of roofs is actual scientific direction, so in the
 educational process of architectural and building trades made corresponding
 innovations [2; 8; 14; 15; 17–20; etc.].
 The roofs considered in this article are defined as special geometric
 polyhedral surfaces, on the basis of two assumptions: (1) all
 eaves of a roof form a planar (simply-connected or k-connected)
 polygon called the base, (2) every hipped roof end makes the same
 slope angle with the (horizontal) plane which contains the base.
 All the vertices and edges of such a roof, forming the roof skeleton,
 determine a graph. The orthogonal projection of a roof skeleton
 onto the base plane leads to a planar graph. On the basis of [11] and [12] and continuing the investigations
 for regular roofs, we formulate further properties which enable studying
 the shapes of the roofs spread over simply connected v-gons for
 an arbitrary integer v (v ≥ 3). We also introduce new operations:
 splitting and grafting of graphs, and formulate some properties of
 these operations. By means of such operations, the creation of a
 graph with cycles using two or more trees is possible. In particular,
 the operation of the grafting of a roof allows modeling an atrial roof.

A prototype online database-enabled design framework for wind analysis/design of low-rise buildings

This study presents a development of an advanced cyberbased database-enabled design module for low-rise buildings (DEDM-LR) which provides estimation of the wind-induced responses for main wind force resisting frames by making direct use of pressure time histories measured at a large number of pressure taps over a suite of building models. These responses may be considered in lieu of code-specified load effects in which the overall accuracy may be influenced by the inherent simplifications in codes. In addition, this new automated approach is particularly attractive and advantageous as it allows a web-based online analysis/design via intuitive user-friendly interfaces for both the input and output in terms of familiar web-style forms that are nowadays very common in most of web-based services. Presently, the DEDM-LR hosts an aerodynamic database developed by the Tokyo Polytechnic University (TPU), Japan for a variety of building configurations like flat, gable, and hip roofs under suburban terrain flow condition with immediate application to other databases. The paper shows the efficacy and validity of the DEDM-LR by walking through its details and examples on selected gable-roofed buildings. The architecture of DEDM-LR platform offers the ability to pool resources by hosting other databases that may become available in the near future.

"Conical Hut": A Basic Form of House Types in Timor Island

Abstract. Timor Island situates in the southeast end of Southeast Asia. The island accommodates many ethnic groups, which produce many diverse house types. As visiting East Timor in 2012 and Timor Island in 2014, we found the “Pair- House Type” widely spread over Timor Island. Uma Lulik (holy house), accommodating the ancestry soul, fireplace and elder’s bed, and Uma Tidor (house for sleep), containing living, sleeping and working space, compose the pair-house. The research team visited 14 ethnic groups and their houses, some of which were measured and drawn into 3D models as back to Taiwan. Uma Tidors of each ethnic group are quite similar with rectangular volume and hip roof, however, one of the fourteen ethnic groups can build cylinder houses for Uma Tidor. Uma Luliks of different ethnic groups are diversified and special. One group of the Uma Luliks shows a rectangular or square volume sheltered by a hip roof. The other group of Uma Luliks presents a non-specific volume under a conical roof, that we called the “conical hut”. Seven ethnic groups, Atoni, Weimua, Makassae, Mambai, Bunaq, Kemak and Bekais, have built “conical huts” for the use of Uma Lulik. People of the seven ethnic groups can construct a reasonable structural system to support the conical roof, and take good advantage of the space under the conical roof to meet their sacred needs and everyday life. “Conical Hut” may be regarded as the basic form of the house types adopted by the seven ethnic groups. It contains the basic spatial limits and the formal properties that the construction systems have to follow. Based on the concise rules of the basic form, people of each ethnic group use their talents, skills and building materials to generate variations of “conical hut”, which are different in house scale, spatial layout, construction system and form. The “conical huts” contain the consistency that all the huts come from the basic form, meanwhile, they also present the diversification that each conical hut has differed. “Consistent but diversified”, is one of the most interesting issues in typological study that we can observe in Timorese houses.

構成要素の連携による寄棟屋根母屋・端部小屋束生成

The purpose of this study is building the part of hipped roof purlin and end strut generation of the frame element generation system by cooperation of constituents in timber framework construction house. The part of hipped roof purlin and end strut generation is built as a multi agent system that the purlin and end strut modeled in the straight line cooperates with close purlins and end struts, repeats correction and decide the right position based on the positioning rules by analyzing the positioning situation of purlin and end strut in hipped roofs and the information of the circumstances. In this study, the knowledge that is obtained on the building this part is reported.

Topological elevation connection analysis for 3D line detection from dense airborne LIDAR data

This paper proposes a kernel-based strategy to analyze the distribution of local point clouds and detect 3D lines from dense airborne LIght Detection and Ranging (LIDAR) data. The proposed method, namely topological elevation connection (TEC) analysis, employs geometric criteria with an automatic procedure instead of threshold operation. The focused targets include flat roofs with parapets, step roofs, hipped roofs, and gable roofs. By comparing with reference data, the accuracy between the detected lines and reference data can reach within 0.2 m. Three-dimensional boundaries and structure lines are essential for building modeling and data registration. Many related works have focused on the collection of co-planar LIDAR points to calculate intersection lines with optimized thresholds. In addition, they did not focus on parapets because of the limitations of developed assumptions and the criteria used. It is crucial to analyze the local point distribution for the automation improvement of detection processes. The major objective is to automatically detect 3D lines using the TEC analysis instead of threshold selection. The interesting targets include building boundaries and a variety of rooftops. The core concept of TEC is that the local relief along the alignment must be smoother than the local relief across the alignment. All consecutive point clouds, which belong to one line, must be sufficient for progressive elevations along the alignment and the linear shape. In the validation, the detected results are compared with reference data. The comparisons indicate that the proposed scheme can reach a detection accuracy of 0.2 m and provide a higher degree of modeling automation for varied building types.

3D RECONSTRUCTION OF BUILDINGS WITH GABLED AND HIPPED STRUCTURES USING LIDAR DATA

Abstract. Buildings are the most important objects in urban areas. Thus, building detection using photogrammetry and remote sensing data as well as 3D model of buildings are very useful for many applications such as mobile navigation, tourism, and disaster management. In this paper, an approach has been proposed for detecting buildings by LiDAR data and aerial images, as well as reconstructing 3D model of buildings. In this regard, firstly, building detection carried out by utilizing a Supper Vector Machine (SVM) as a supervise method. The supervise methods need training data that could be collected from some features. Hence, LiDAR data and aerial images were utilized to produce some features. The features were selected by considering their abilities for separating buildings from other objects. The evaluation results of building detection showed high accuracy and precision of the utilized approach. The detected buildings were labeled in order to reconstruct buildings, individually. Then the planes of each building were separated and adjacent planes were recognized to reduce the calculation volume and to increase the accuracy. Subsequently, the bottom planes of each building were detected in order to compute the corners of hipped roofs using intersection of three adjacent planes. Also, the corners of gabled roofs were computed by both calculating the intersection line of the adjacent planes and finding the intersection between the planes intersection line and their detected parcel. Finally, the coordinates of some nodes in building floor were computed and 3D model reconstruction was carried out. In order to evaluate the proposed method, 3D model of some buildings with different complexity level were generated. The evaluation results showed that the proposed method has reached credible performance.

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.