Gable Roof Buildings Research Articles

Wind loading on gable and multi-span roof buildings: Comparison between field monitoring, wind tunnel experiments, and design code provisions

The wind loading provisions in the National Building Code of Canada (NBCC) have not been updated for decades despite developments in wind tunnel methods since the original source data. This study aims to review the Nbcc 2020 provisions compared to wind tunnel experiments, field measurements, and the ASCE 7–22 provisions for single and multi-span gable roof buildings. Field measurements and wind tunnel tests are used to collect data for an isolated building and later for a multi-span gable. The pressure coefficients from the field measurements were mostly higher than the wind tunnel, which is consistent with previous studies. The results provided evidence that NBCC provisions for single-gabled roofs (with slope 7∘<α≤27∘) and multi-span gabled roofs (with slope 10∘<α≤30∘) are currently underestimated. New provisions are suggested for the corner (c), edge (s), and field (r) zones of the single-span gabled roof and for gable-end-edge (s’) zone of the multi-span. It is suggested to merge Zone s into Zone c to form a new perimeter Zone p for the single gabled roof and to merge Zone s’ into Zone c for the multi-span gabled roof. The proposed changes correct the current provision underestimation and add simplicity for easier construction.

Numerical Investigation of Cross Ventilation Flow in A Gable Roof Building with Asymmetric Opening Positions

Natural ventilation can be a suitable alternative to mechanical ventilation as it is cost-effective and environmentally friendly. Therefore, an effective design of the natural ventilation system is very crucial. In this work, an attempt has been made to investigate the impact of opening positions and roof pitch on the performance of wind-induced cross-ventilation in a gable roof building. Numerical simulations were carried out using the computational fluid dynamics (CFD) technique based on the steady Reynolds averaged Navier-Stokes equations (RANS) model. Six configurations with asymmetric openings on opposite facades were considered to evaluate the effect of opening positions. Further, for studying the influence of roof pitch on the flow properties, three roof pitches, viz. 3:10, 5:10 and 7.5:10 were considered. It is found that the configuration with a windward opening in the middle and a leeward opening at the bottom (Configuration D) has the highest flow rate. The configuration with a windward opening at the top and a leeward opening at the bottom (Configuration B) has the lowest flow rate. Furthermore, the investigation with different roof pitches reveals that buildings with lower roof pitches are more vulnerable to wind loading due to higher flow separation at the windward eave. The investigation concludes that the opening position and roof pitch significantly influences the indoor airflow characteristics thereby affecting the ventilation performance.

Assessment of lattice Boltzmann method for low-rise building wind flow simulation with limited resources

The study of low-rise buildings' interaction with wind is gravitating toward large eddy simulation (LES) for simulating airflow. As it is straightforward to implement and also offers the option to simulate particles, sound, and heat flow, the lattice Boltzmann method (LBM) may be an interesting option among the LES methods but has so far barely been explored for this application. In this work, the LBM is investigated and assessed as a tool for the analysis of wind flow around low-rise buildings. The hardware resources used are limited to one GPU to mimic the limited resources an industrial setting or a preliminary study might allow for. We suggest an efficient LBM simulation setup and compare its results from the wind flow around nine exemplary gable roofed low-rise buildings to findings of previous studies, both in detail and in terms of found behaviors. All comparisons show good agreement between our findings and the previous results obtained via other simulation methods or wind tunnel measurements. These results confirm that the LBM may be used to investigate low-rise buildings, even with limited hardware. It is thus a further contender among the available LES methods and our setup may serve as starting point for its application.

Breaking Boundaries in Wind Engineering: LSU WISE Open-Jet Facility Revolutionizes Solar Panel and Building Design

Experimental wind engineering is crucial for global structural design. This paper addresses limitations in aerodynamic testing, particularly in wall-bounded and small-scale scenarios. Open-jet testing, introduced as an advanced tool, overcomes turbulence modelling constraints, providing a more accurate representation of real-world conditions. The LSU WISE open-jet facility produces complete turbulence at a large scale, eliminating the need for corrections accompanied by partial turbulence simulation. This discovery holds significant implications in wind engineering and unsteady aerodynamics. Integrating photovoltaic panels with gable-roofed buildings may not require additional structural reinforcement, with a reduction in wind uplift forces by 45–63%. Building-integrated photovoltaics (BIPV) offer design flexibility and aesthetic appeal despite potential higher upfront costs. Strategic interventions, such as design optimization and cost-effective installation methods, can enhance the economic viability of BIPV systems. Contrary to long-held beliefs, the findings challenge the notion that wind loads on structures with sharp corners are insensitive to Reynolds number. Open-jet testing produces higher peak pressures, providing real-world justification for actual damage in high-rise buildings. These results validate the author’s hypothesis regarding the underestimation of peak loads (in small-scale testing) leading to cladding failure in high-rise buildings. They emphasize the superiority of large-scale open-jet testing, underscoring its critical role in designing resilient structures. The LSU WISE open-jet facility’s unique capabilities hold immense promise for revolutionizing wind engineering, addressing grand challenges, and creating more resilient and sustainable infrastructure. Its applications span critical infrastructure, promising significant economic, societal, and educational impacts in STEM fields.

Effects of Cornices on Wind Loads of Solar Panels Mounted on Gable Roof Building

The effects of various parameters of the solar panel and surrounding structure on wind loads acting on solar panels have been extensively investigated in prior studies. However, the parameter of cornice length has not been considered. With varying lengths of cornices, solar panels can be positioned either near or far away from the roof corner and edge, which are the locations where the largest wind-induced suction forces are likely to occur. To examine the effects of cornices, a wind tunnel test was conducted to measure the wind pressures on a solar module installed on a residential gable roof building. The cornice lengths varied from 0 m to 1.6 m, with an interval of 0.4 m. The results show that when wind blows perpendicular to the roof ridge, cornice can reduce the mean, STD, and peak pressure coefficients on the upper and lower surfaces and resulting net values. However, it should be noted that the most unfavorable area-averaged minimum peaks in the middle and trailing zones exhibit a gradual increase with the growing cornice length. Considering the potential risk of solar module failure resulting from high wind-induced suction forces, more caution is needed when installing solar modules on roofs with larger cornices.

Wind-induced fragility of a group of three gable-roof buildings with different roof slope and building spacing

The influence of the roof slope, building spacing, building orientation and joint probability of wind speed and direction on the wind-induced fragility (WIF) of a group of three gable-roof buildings was investigated. The results show that wind interference effects on the WIF of buildings are significant. The dependency of the WIF of buildings with a small roof slope of 10° is nearly opposite from that with a large roof slope of 35°. When the roof slope is 10°, wind shielding effects make the WIF of the center and downstream buildings less than that of the isolated building, the WIF decreases with the decrease of building spacing, and the maximum increase of the minimum critical wind speed among all wind directions reaches 14.1%. When the roof slope is 35°, wind amplification effects make the WIF of the upstream and center buildings greater than that of the isolated building, the WIF increases with the decrease of building spacing, and the maximum decrease of the minimum critical wind speed is 7.2%. When the buildings are located in Fuzhou, the WIF reaches the minimum (it means the most favorable building arrangement) for buildings with a roof slope of 10°, and it reaches the maximum (it means the most unfavorable building arrangement) for buildings with a roof slope of 35° at the building orientation of about 30° with a small building spacing.

Effects of slope curvature, ridge height and layered roofs on wind pressures on traditional-Chinese-style gable-hip and gable roofs

Curved slope profiles, high ridges and layered roofs are important features of traditional Chinese buildings, and they affect wind pressures and loads on roofs. Wind loadings on traditional Chinese hip roofs have been studied (Shan et al., 2018). However, traditional Chinese gable-hip roofs and gable roofs are as important as hip roofs, and their wind loading characteristics need to be investigated. Wind tunnel tests are performed on linear-slope gable-roof building models, as well as traditional Chinese building models with gable- and gable-hip roofs to investigate and estimate the necessary wind-resistant capacity of cladding tiles. Effects of roof curvature, ridge height and layered roofs on wind loadings on traditional Chinese gable roofs and traditional Chinese gable-hip roofs are investigated. Roof curvature of a gable roof can enlarge the peak area-averaged pressure and increase the resultant lift force. With increase in ridge height of a traditional Chinese gable roof, peak pressures increase while resultant lift forces decrease. Layered roofs decrease peak pressures but increase resultant lift forces on double-layer gable-hip roofs. As a result, wind pressures on traditional Chinese roofs can be significantly influenced by all three unique shape characteristics.

Wind induced pressures on a large low-sloped gable roof building with parapet

This paper experimentally investigates how parapets with varying heights can alter the flow pattern around a large aspect-ratio low-sloped gable roof building. We examine the benefits and challenges of existing methods and utilize an open-jet wind test section, to accurately simulate real-world atmospheric boundary layer conditions. A model of a low-rise building was fitted with solid parapets of varying heights and tested in a comparative study to understand their impact on roof pressures. The study compares the standard approach to the experimental results and suggests improvements to wind zones and pressure coefficients. The parapet of fourteen percent of the building height is the most efficient at reducing mean, peak, and area-averaged wind loads compared to other sizes. However, the standard provisions underestimate roof pressures for components and cladding design.

Macro Flow Dynamic Study of Wind Around a Gable Roof Building with Openings

Understanding the flow field developed in the proximity of a building due to the wind flow over it is a prerequisite for designing a building. The wind environment around buildings plays a pivotal role not only from the point of view of structural integrity but also impacts the ventilation performance, pedestrian comfort and dispersion of pollutants. With the emergence of the green building concept in the light of the sustainable living, modern buildings are equipped with various openings such as doors, windows and ventilators. These openings change the flow characteristics in and around the building remarkably and make the flow field much more complex. The current study seeks to improve the understanding of both the internal and external flow fields around the buildings with openings. In this work, an attempt has been made to investigate the influence of wind direction on the flow behavior of wind in and around gable roof buildings with six different opening configurations. Commercially available CFD software ANSYS-FLUENT is used for numerical simulations. The numerical simulations are carried out to solve the steady Reynolds Averaged Navier Stokes (RANS) equations. The results obtained from the numerical simulations are validated with the previously published experimental results, and a good agreement was observed.

Variation of wind load distribution on gable roof building

Wind forces and their impact on the structural integrity of roofs and walls are pivotal considerations in architectural and engineering design. This study discusses the effect of wind load on gable roof buildings with varying slopes. Gable roof structures find extensive application in industrial construction projects. Based on wind tunnels with rigid models, wind pressure distributions on gable roof buildings with different aspect ratios were measured simultaneously. Special attention is required for the safe design of the building. Information regarding the wind pressure coefficients on buildings is available in codes of practices of various countries dealing with wind loads; however, such information is very limited. The present study will examine the suitability of four building models with roof angles of 10º, 15º, 20º, and 25º and will be analyzed using IS 875 (Part 3), and various forces will be calculated. Then, the same buildings will be modeled using STAADPro/SAP2000, and the comparison of the analysis will be made. Further, a building situated at various slopes on a hill will be modeled using STAAD-Pro/SAP2000, and the variation of Wind Forces along the slope will be studied. The expected results of this study will be finding out the most critical slope of a gable roof on a building and reducing the effect of wind forces on it. Furthermore, the most savior location of a building along the hill slope will be investigated, and the ways to reduce the effect of these wind forces will be studied.

Effect of gable roof with various roof pitches and obstacle heights on natural ventilation performance for an isolated building

Numerical analysis based on CFD steady RANS equations was used to study the airflow characteristics around and within an isolated gable roof building. Parameters that are the main study focus of this research include: streamlines of normalized velocity, pressure coefficient and ventilation rate. The effect of gable roof with four different roof pitches namely 15º, 25º, 35º &amp; 45 were investigated against varying obstacle heights of 40, 50, 60 &amp; 70 mm. From the simulation results, the streamlines show that larger roof pitch leads to increased velocity at the window and roof openings due to the external and internal pressure difference in the building. The corresponding increment in internal obstacle height on the other hand leads to gradual alteration of airflow direction in front of the obstacle, and also an increase of the pressure coefficient inside the building because of wind blocking effect. This pressure coefficient also sees a reduction in value at the windward and inside of the building with an increase in steepness of the roof pitch due to increasing internal velocity. Hence, airflow behavior and characteristics are clearly dependent on roof pitch and internal obstacle height which indicates a good agreement with the findings from the previous studies. Gable roof with a steeper roof pitch building coupled with lower internal obstacle height will therefore yield better ventilation rates.

Interpretation of Machine-Learning-Based (Black-box) Wind Pressure Predictions for Low-Rise Gable-Roofed Buildings Using Shapley Additive Explanations (SHAP)

Conventional methods of estimating pressure coefficients of buildings retain time and cost constraints. Recently, machine learning (ML) has been successfully established to predict wind pressure coefficients. However, regardless of the accuracy, ML models are incompetent in providing end-users’ confidence as a result of the black-box nature of predictions. In this study, we employed tree-based regression models (Decision Tree, XGBoost, Extra-tree, LightGBM) to predict surface-averaged mean pressure coefficient (Cp,mean), fluctuation pressure coefficient (Cp,rms), and peak pressure coefficient (Cp,peak) of low-rise gable-roofed buildings. The accuracy of models was verified using Tokyo Polytechnic University (TPU) wind tunnel data. Subsequently, we used Shapley Additive Explanations (SHAP) to explain the black-box nature of the ML predictions. The comparison revealed that tree-based models are efficient and accurate in wind-predicting pressure coefficients. Interestingly, SHAP provided human-comprehensible explanations for the interaction of variables, the importance of features towards the outcome, and the underlying reasoning behind the predictions. Moreover, SHAP confirmed that tree-based predictions adhere to the flow physics of wind engineering, advancing the fidelity of ML-based predictions.

On the deviation of mean pressure coefficients in wind loading standards for a low-rise, gable-roofed building with boundary walls

The provisions in wind loading standards routinely overlook the influence of nearby small-size objects on wind loads of low-rise buildings. One such object is boundary walls that significantly modify the surrounding wind field thereby affecting the wind loading of low-rise buildings. To investigate this phenomenon, four low-rise, gable-roofed buildings: one with and three without boundary walls were tested in a boundary layer wind tunnel. The calculated external pressure coefficients (C¯p) were subsequently compared with the provisions given in ASCE 7 (2016), NBCC (2015), EN 1991-1-4 (2005), and AS/NZS 1170.2 (2011). The comparison showed a good agreement for the C¯p calculated using ASCE 7-16 (2016) and AS/NZS 1170.2 (2011) for the building without boundary walls with those of the wind tunnel test. However, all wind loading standards overestimated C¯p of the buildings with boundary walls because they did not account for the shielding effect of boundary walls. The largest discrepancies in magnitude and distribution of wind pressure were observed on the windward wall and the upwind roof slope. These modifications showed a strong dependency on the upstream and lateral separation distances between the building and the boundary walls.

Effects of roof configuration on natural ventilation for an isolated building

Numerical analyses based on CFD steady RANS were conducted to investigate the effects of roof configuration on wind-induced natural ventilation for an isolated roofed building. Gable roof and saltbox roof building models were tested with 15˚, 25˚, 35˚ and 45˚ roof pitch in present study. The flow field information and flow characteristics were obtained from the contours and plots generated by CFD. In accordance to the increment of roof pitch, the turbulence kinetic energy and mean velocity ratio show vigorous response. The flow separated at the windward corner do not reattach onto the roof, thus induced higher velocity gradient and form a large vortex at the roof ridge. The vortices behind then building caused by the flow separation at the roof ridge extend along the mixing layer and spread up to the roof. The pressure differences mainly rely on the roof shapes. Greater pressure differences between the upstream, interior and downstream was observed in saltbox roof cases. This is due to the extended roof height which boosted the impinging effect caused by the incoming wind. Generally, the saltbox roof configuration exhibit better performance than gable roof in terms of the measured parameters.

Risk and fragility assessment of residential wooden buildings subject to hurricane winds

Hurricanes are one of the major causes of damage and loss to residential wooden buildings in the United States. The study of hurricane-imposed risks to residential wooden buildings is, therefore, a fundamental step to mitigate these damages and losses. Within this context, a probabilistic methodology is provided for the fragility analysis of residential wooden buildings. Two damage mechanisms are considered in this methodology, excessive dynamic wind pressure and impact from windborne debris. Unlike existing frameworks, the methodology defines the geometric configuration as well as the required extension of the neighboring buildings to estimate the damage from both mechanisms. A case study illustrates the methodology on residential communities composed of archetype gable-roof buildings. Ten construction cases are defined to cover a range of resistances of building components for both considered damage mechanisms. Three floor-area ratios (FAR) are also considered. The resulting fragility curves highlight: (1) the effect of the FAR on enhancing the performance of residential buildings due to the effect of shielding; and (2) the significance of windborne debris in increasing the estimated hurricane risk. The estimated fragility curves can be used to directly model residential buildings in community resilience frameworks.

A Conditional Simulation Method for Predicting Wind Pressure Fields of Large-Span Spatial Structures

Wind load is among the control loads for large-span spatial structures. Wind tunnel test is one of the commonly used methods for measuring wind pressure fields of different kinds of structures. However, due to the limited wind pressure data obtained from wind tunnel testing, it is quite meaningful to employ the limited measured data to predict the unknown wind pressure at target points. Considering the complexity of wind pressure fields of large-span spatial structures, a simplified nonparametric method based on conditional simulation is proposed to predict the unknown pressures using the existing data. The Karhunen–Loève (KL for short) expansion is employed to represent wind pressure random variants as eigenfunctions of the covariance operator. To reduce the variant dimensionality, the nearest neighboring estimator is given for the transition distribution of the KL expansion. The targeted wind pressure fields are obtained by expanding the Fourier basis of the eigenfunction and estimating its expansion coefficients. The proposed method is applied to estimate wind pressures on a gable roof building. The relevant parameters of the wind pressure field are obtained, and the results compare well with those from wind tunnel testing, with higher efficiency. The proposed method effectively reduces the dimensionality of the predicted wind pressures, with reduced errors, higher accuracy, and increased efficiency.

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.

Field measurements of snowdrift characteristics on reduced scale building roofs based on the size effect study

Unbalanced snow distribution, which leads to an excessive snow load in a local area, is one of the main reasons for building collapses. The formation of uneven snowdrifts is closely related to the shape of the building as it seriously affects the turbulent structure and drifting snow process. Unfortunately, the design codes of different countries for applying snow load on building structures cannot give a clear explanation because of the discrepancies between them. Therefore, a series of reduced scale field measurements of snowdrifts on roofs were conducted to clarify such discrepancies. Firstly, the size effect of model scaling was investigated by observing snowdrifts around two models with a scale ratio of 1/2. The results show that the size effect has little influence on the snowdrift pattern on the premise of satisfying the similarity criterion. Thereafter, the snowdrift characteristics of two-level roofed and gable roofed buildings were explored and analyzed through the comparison with different national load codes and collapsed building cases. Overall, the provisions of the Chinese load code differ from the measurement results, which leads to an underestimation of roof snow load. ISO 4355 and Canadian NBC codes could give a better prediction of the snow load by comparison.

How gable roofs change the mechanisms of turbulent vertical momentum transfer: A LES study on two-dimensional urban canyons

A Large Eddy Simulation (LES) study on the presence of gable roofs in urban canyons is presented: two canyon aspect ratios, ARC= 1, 2, (ARC= W/H corresponding to the ratio of the canyon width, W, to the eaves’ height, H) and variable roof slope, α (α = 0°, 10°, 20°, 30°, 45°) in a periodic configuration are considered. The vertical turbulent momentum flux is analysed by means of the quadrant analysis both in terms of spatial maps and mean vertical profiles in order to assess how the presence of a gable roof and its slope affects the mechanisms of mixing in the roughness sublayer. A gradual modification with increasing roof slope is apparent for the mean flow patterns as well as for the shear layer thickness. On the contrary, the contribution of ejections and sweeps at the rooftop goes through an abrupt change when passing from flat-to gable-roof buildings. This behaviour arises for both the investigated canyon aspect ratios. With gable roofs the imbalance between sweeps and ejections is monotonically increasing with α. However, the case of flat roof differs from the small pitch ones, as it gives much higher values of imbalance, comparable to what was observed for the largest analysed pitches (45°).

Airflow over low-sloped gable roof buildings: Wind tunnel experiment and CFD simulations

In this study, the impact of roof slope on the flow characteristics over low-sloped gable roofs was investigated using steady computational fluid dynamics (CFD) simulations based on a k-ω SST turbulence model. A measurement database of the flow field over a scaled model of 15° was created using particle image velocimetry (PIV). Sensitivity analyses for the grid resolutions and turbulence models were performed. Among the three common Reynolds-averaged Navier-Stokes equations (RANS) models, the k-ω SST model exhibited a better performance, followed by the RNG model and then the realizable k- model. Next, the flow properties over the differently sloped (0° to 25°) building models were determined. It was found that the effect of roof slope on the flow characteristics was identified by changing the position and size of the separation bubbles, 15° was found to be approximately the sensitive slope at which the distribution of the separation bubbles changed significantly. Additionally, it is suggested additional attention focused on the distributions of the negative pressure on the windward surfaces (especially 5° and 10° roofs) and the possible snow redistribution on the leeward surfaces.