Large Roof Research Articles

A Novel Global-Local Feature Aggregation Framework for Semantic Segmentation of Large-Format High-Resolution Remote Sensing Images

In high-resolution remote sensing images, there are areas with weak textures such as large building roofs, which occupy a large number of pixels in the image. These areas pose a challenge for traditional semantic segmentation networks to obtain ideal results. Common strategies like downsampling, patch cropping, and cascade models often sacrifice fine details or global context, resulting in limited accuracy. To address these issues, a novel semantic segmentation framework has been designed specifically for large-format high-resolution remote sensing images by aggregating global and local features in this paper. The framework consists of two branches: one branch deals with low-resolution downsampled images to capture global features, while the other branch focuses on cropped patches to extract high-resolution local details. Also, this paper introduces a feature aggregation module based on the Transformer structure, which effectively aggregates global and local information. Additionally, to save GPU memory usage, a novel three-step training method has been developed. Extensive experiments on two public datasets demonstrate the effectiveness of the proposed approach, with an IoU of 90.83% on the AIDS dataset and 90.30% on the WBDS dataset, surpassing state-of-the-art methods such as DANet, DeepLab v3+, U-Net, ViT, TransUNet, CMTFNet, and UANet.

The effect of place of living on social acceptance of shared PV projects in Switzerland

In Switzerland, solar power has the greatest potential to further advance the energy transition. As conventional rooftop PV excludes a large share of citizens from personally contributing to climate change mitigation, shared PV (photovoltaics) projects offer a more inclusive alternative, e.g. also for urban residents who are less likely to have the option to install solar panels on their own roof. Thus, investigating people’s preferences depending on the degree of urbanity of their place of residence is crucial to determine socially acceptable PV project designs. Using original Swiss survey data (N = 3000) and applying conjoint analysis, different preferences both depending on respondents’ place of living as well as for different dimensions of social acceptance are found. Most notably, big city residents are generally most in favour of such projects but they exhibit the lowest willingness to actually invest. The conjoint experiment showed that, regarding the DVs of project rating and project choice, only the reimbursement by credit vouchers significantly improved project acceptance for big city residents. This also holds true for rural residents, where, in addition, tax deductions (reimbursement), traffic infrastructure, large consumer roofs (location) and electricity provider were also positively evaluated. For the DV specifying the amount of PV modules bought, no project attribute level managed to significantly increase this number, for which only investment-reducing factors were identified: Residents from big cities invest less when a PV project is located in a skiing area or when the investment is made at an information event. For rural residents, large consumer roofs as a location decrease the scale of an investment. These factors should therefore be avoided when planning a shared PV project in order to maximise investments. Fulfilling respective preferences (i.e. according to projects’ place-based target group) may prove relevant to enhance social acceptance of shared PV projects.

Non-stationary winds effects over large partially-open roofs: A CFD study regarding the role of unsteady aerodynamics

Non-stationary winds are increasingly attracting the attention of the scientific community and, despite not being explicitly considered in current design practice, they are known to produce important damages. In particular, the non-stationarity of such events has important consequences with respect to four main aspects which affect the definition of design wind loads: (i) the design wind speed definition, (ii) the wind profiles, (iii) the calculation of the structural response and (iv) the insurgence of unsteady aerodynamics effects. While the first three aspects already received considerable attention, the last one is still largely unclear and its relevance still to be assessed. In particular, for non-stationary winds such as macro- and micro-downbursts, the ramp-up time might become so short to trigger unsteady aerodynamic effects in the overall flow arrangement, which cannot be inferred from results obtained for stationary cases. In this paper, we propose a first investigation of such matter considering a large stadium roof using Large Eddy Simulations. Results show that, for the considered case, noticeable unsteady aerodynamic effects, which leads to an amplification of wind loads, can be triggered when the wind rump-up time is in the order of 30 s, and quickly decrease in importance for higher rump-up times.

Evapotranspiration evaluation using three different protocols on a large green roof in the greater Paris area

Abstract. Nature-based solutions have appeared as relevant solutions to mitigate urban heat islands. To improve our knowledge of the assessment of this ecosystem service and the related physical processes (evapotranspiration), monitoring campaigns are required. This was the objective of several experiments carried out on the Blue Green Wave, a large green roof located in Champs-sur-Marne (France). Three different protocols were implemented and tested to assess the evapotranspiration flux at different scales: the first one was based on the surface energy balance (large scale); the second one was carried out using an evapotranspiration chamber (small scale); and the third one was based on the water balance evaluated during dry periods (point scale). In addition to these evapotranspiration estimates, several hydrometeorological variables (especially temperature) were measured. Related data and Python programs providing preliminary elements of the analysis and graphical representation have been made available. They illustrate the space–time variability in the studied processes regarding their observation scale. The dataset is available at https://doi.org/10.5281/zenodo.8064053 (Versini et al., 2023).

Flat roof classification and leaks detections by Deep Learning

This paper presents an efficient and accurate method for detecting flat roof leaks using a combination of unmanned aerial vehicles (UAVs) and deep learning. The proposed method utilizes a DJI M300 drone equipped with RGB and thermal cameras to capture high-resolution images of the roof. These images are then processed to create orthomosaics and digital elevation models (DEMs). A deep learning model based on the U-NET architecture is then used to segment the roof into different classes, such as PVC foil, windows, and sidewalks. Finally, the damaged insulation is identified by analyzing the temperature distribution within the PVC foil segments. The proposed method has several advantages over traditional inspection methods. It is much faster and more efficient. A UAV can collect images of a large roof in a matter of minutes, while traditional methods can take several days or weeks. The orthomosaics and temperature maps generated by the UAV are much more detailed than the images that can be collected by a human inspector. Third, the UAV-based system is safer. The UAV can collect images of the roof without the need for a human inspector to climb onto the roof, which can be dangerous. The results of this study show that the proposed method is an effective and accurate way to detect flat roof leaks. The deep learning model was able to achieve an overall accuracy of 95% in segmenting the roof into different classes. The method was also able to identify damaged insulation with a high degree of accuracy.

Finding Attractive Electric-Vehicle-Charging Locations with Photovoltaic System Integration

The rise of electric mobility poses a challenge and an opportunity for the housing industry to provide charging infrastructure. The housing industry can take advantage of its large roof areas to install photovoltaic (PV) systems and use the electricity generated to charge electric vehicles. This study explores how the charging demand can be allocated to specific locations based on socio-economic parameters and determines whether PV integration is economically viable for EV charging. Two models are used, one with extensive spatial and traffic data to determine the charging demand for over 300 locations, and another with a time-series-based approach for four specific locations to analyze the seasonal dependencies. The results indicate that PV integration is economically advantageous when electricity purchase prices exceed 0.15 EUR/kWh. Higher electricity prices can lead to significant additional profits through PV integration. Slow charging and charging during the day are beneficial, as they increase self-consumption, making PV systems economically viable. However, fast-charging infrastructure should be combined with PV storage systems for effective PV integration.

Blood 25-hydroxyvitamin D3 concentration of Japanese Black cattle at two farms with different rearing environments, Kagoshima prefecture, Japan.

Forty-two Japanese Black cattle on two farms in Kagoshima prefecture, Japan were used in this study. The rearing style of farm A was in a dark barn with a large roof to block sunlight (n=21). The rearing style of farm B was grazing, and exposed to direct sunlight (n=21). Blood sampling was performed twice on the same cattle in August 2022 (summer) and February 2023 (winter). As the results, the serum 25(OH)D3 concentrations were significantly lower in cattle of farm A than in cattle of farm B (P<0.01), and were significantly lower in winter season than in summer season (P<0.01). These results showed that there were differences in blood 25(OH)D3 concentrations between the farms or seasons.

Deterministic risk assessment of hydrogen leak from a fuel cell truck in a real-scale hydrogen refueling station

Deterministic risk assessment for hydrogen installations offers an integrated solution for H2 risk assessment, incorporating a hydrogen release model, a site-specific 3D geometry model, a Computational Fluid Dynamics (CFD) tool, and a consequence analysis methodology. Empirical engineering models expedite the preparation of source terms and harm evaluations, while CFD generates 3D contours of radiation and overpressure loads. A case study is provided by investigating a gaseous hydrogen leak of a truck in a refueling station with a large roof. The effects of leak diameters, roof configurations, and ignition locations on hydrogen dispersion, combustion, and hazard analysis are examined. Results indicate that the majority of the burnable cloud accumulates in a half-meter layer under the ceiling, diminishing within a minute. The impact of thermal radiation on individuals is insignificant, but overpressures increase the likelihood of structure failures, indirectly affecting human fatality. These findings inform the optimization of refueling station design and safety management.

Technical and Financial Feasibility Analysis of Rainwater Harvesting Using Conventional or Green Roofs in an Industrial Building

Given the high annual water consumption for non-potable uses (1112.08 m3, 65%) of an industrial building with a large roof area (4638 m2) located in the Northeast of Portugal, this study aims to evaluate the technical and financial feasibility of a rainwater harvesting system for these uses, considering the existing conventional roof (scenario 1) and adapting a green roof to the existing roof (scenario 2). This evaluation was based on the impact of the two scenarios on the building’s water savings. Under scenarios 1 and 2, the expected water savings were 64.47% and 59.43%, respectively. Therefore, the expected reduction in the annual water bill was €3867.07 + VAT (scenario 1) and €3564.63 + VAT (scenario 2). For scenario 1, considering a reservoir with 70 m3 for non-potable purposes, such as washing the building’s floor and use in industrial machines, and an initial investment of €41,109.13 + VAT, the single payback will be 11.29 years. The single payback for scenario 2 largely exceeded the lifetime of the green roof. However, as they are considered interesting solutions to reduce the negative externalities of industrial settlements, financial incentives could be proposed for the implementation of the green roof in this typology of buildings.

COST-WINNERS: COST reduction WIth Neural NEtworks-based augmented Random Search for simultaneous thermal and electrical energy storage control

The combination of local renewable energy production, dynamic loads, and multiple energy storage systems with different dynamics requires sophisticated control systems to maximize the energy cost efficiency of the combined energy system. Battery and thermal energy storage systems can be combined to increase the local use of on-site renewable energy, reduce peak power demand, and exploit time-of-use energy pricing. In this paper, we focus on how the augmented random search algorithm and artificial neural networks can be used together to solve an energy cost optimization problem involving the control of a battery energy storage system and a thermal energy storage system at the same time in a smart warehouse. As part of this work, a simulated training environment made using the data from the smart warehouse’s operations. In addition to the energy storage systems, the warehouse energy system has integrated a large roof mounted photovoltaic power plant and an industrial-scale cooling system.The developed solution is able to minimize the energy costs by modulating both energy systems, depending on the situation. Additionally, when it is tested against the state-of-the-art solutions, our developed solution at worst matches performance when the alternative algorithm is allowed to increase training time by a factor of nearly three. On average, our presented solution doubles the performance of the benchmark algorithm with much less computational resource expenditure.

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.

Effect of mining-induced abutment pressure on gateroad and grouting-based bolting technology: A case study

Longwall roadway suffered from mining-induced abutment pressure caused by the consequent large roof movement is a major concern in underground mining. In this study, a novel grouting-based bolting technique was put forward for Headgate 1404# of Xintian Coal Mine, China. Compared with the traditional support methods of single prop and hydraulic support, the proposed method has the advantages of low labor intensity and high improvement of surrounding rock. The field investigation on the effect of mining-induced abutment pressure on the roadway and calibrated numerical models on parameter verification are the key technical design of the proposed grouting-based bolting method. The field investigation showed that in the range of 0–30 m from the faceline, roof-to-floor convergence and roof fracture of the roadway were significant, which affected the stability of the roadway. In our designed scheme, grouting anchor cable was employed for roof pre-reinforcement through grouting the cement and sodium silicate into the roof; the grouting depth was 8 m, and the grouting position was 30 m ahead of the mining operation. The reliability of this scheme was verified by the comparison of stress field, skin convergence, rock fracture and grouting diffusion via the numerical simulation. The simulation results show that after applying grouting-based bolting, the range of maximum principal stress reduction, deformation and the fractured zone around the roadway is smaller than that of the traditional single support. Compared with the traditional method, the convergence of roof-to-floor and rib-to-rib after the implementation of the proposed method decreases by 64.5 % and 82.0 %, and the fracture depth of the roof and ribs decreases by 66.4 % and 38.2 %, respectively. The proposed grouting-based rock bolting significantly improves the resistibility of roadway surrounding rock to the mining-induced abutment pressure, which is beneficial for roadway retaining after mining.

Strategic PV expansion and its impact on regional electricity self-sufficiency: Case study of Switzerland

Solar photovoltaics (PV) will play an important role in decarbonising the energy system. To date, most assessments of PV transition pathways focus on least-cost aspects, without neither considering the time needed to achieve a substantial PV deployment, nor the impacts on regional electricity supply equality. In this work, we propose two alternative PV expansion strategies for Switzerland: The first strategy prioritises the most productive roofs and reaches national PV targets by exploiting the minimum number of rooftops, while the second strategy aims at maximising regional self-sufficiency as proxy of PV supply equality. Both strategies are assessed for several PV expansion scenarios using real hourly PV potential data for the entire Swiss building stock. The scenarios are compared to hourly electricity demand profiles for the residential and service sector. Results suggest that when employing the first strategy, at least 46% of suitable rooftops – mostly large roofs with low tilt angles – are needed to reach Switzerland’s 2050 PV expansion target of 35 TWh. For the projected electricity demand in 2050, this leads to annual electricity self-sufficiency in about 40% of Swiss districts. This percentage can be increased to over 70% by following strategy two to maximise self-sufficiency – which may feature several economic and societal advantages – at the cost of covering 86% of suitable rooftops with PV. The findings may support policy makers and local utilities to find efficient and equitable pathways for a decentralised PV expansion, while at the same time reaching the ambitious national renewable energy targets within due time.

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.

Numerical Simulation Study on Stability Control Technology of Large-Area Wall Caving Area (LAWCA) in Large-Inclined Face

The caving characteristics of the goaf significantly impact the mining stability of the working face. The coal-forming environment of the steeply dipping coal seam is complex. After mining, the caving rock mass rolls to the lower part of the working face due to gravity, and the caving compaction characteristics of the working face are different from those of the flat and gently inclined working face, taking Huainan Xinji No. 2 Mine 211112 high-angle composite roof working face large-area gang roof fall area as the engineering background. To safely pass through a large roof fall area, a FLAC3D numerical simulation method considering the goaf’s compaction effect and the excavation’s additional damage is proposed. The Weibull distribution function is introduced to modify the elastic modulus parameters of the rock mass after excavation, which more accurately reflects the damage process of the rock mass after hole. Based on the goaf compaction theory, the elastic model is developed for the second time, and the accurate simulation of the caving rock mass is realized. On this basis, the proposed numerical simulation method is used to simulate the large-area roof caving of the large-angle working face, a scheme to control the stability of the working face by using the paste filling technology is proposed, and the material parameters of the filling body are determined. The research results show that when the water-cement ratio of the backfill is 3 : 1, the simulation and field trial results are good, and the safe and efficient mining of the large-angle composite roof working face is realized, which verifies the feasibility and correctness of the coupled simulation method. At the same time, the research results can provide a reference for controlling the roof fall area of the working face with a large inclination angle.

Supporting optimization of thick seam roadway with top coal based on orthogonal matrix analysis

Aiming at the problem of large deformation and difficulty in surrounding rock control of the top coal roadway in thick seam, theoretical analysis, theoretical analysis, numerical simulation, orthogonal matrix analysis and other methods were used to study the roof deformation and support parameter optimization of the top coal roadway in thick seam. Firstly, the structural model and roof mechanical model of the top coal roadway in thick seam were established, and the deformation coefficient TK was defined based on the relationship between curvature radius and bending moment, maximum bending moment and ultimate tensile strength of beam. According to the ratio of deformation rate between TK and beam to determine the roof deformation mode of top coal roadway, the discriminant conditions of roadway roof stability under two deformation conditions are obtained. Due to the characteristics of serious coal-rock fragmentation, large roof deformation, and integration of top coal and side coal. Therefore, the combined support method of “high prestressed long and short anchor cables” is proposed by double arch bearing structure control technology. Finally, based on the orthogonal matrix analysis method of supporting parameters optimization of the top coal roadway in thick seam, the analysis amount of supporting scheme is significantly reduced, the comprehensive evaluation of multi-factor and multi-supporting effect of roadway support is realized, and the optimal supporting scheme is obtained. Compared with the surrounding rock of the roadway without support, the deformation of the roof is reduced by 27.27%, the deformation of the two sides is reduced by 45.24%, and the tensile failure volume is reduced by 54.66%. The top coal roadway in thick seam has been effectively controlled, which provides guarantee for high yield and high efficiency of the mine.

Characteristics of Ground Pressure Disaster and Rockburst Proneness in Deep Gold Mine

Abstract To obtain rockburst characteristics at rock engineering, the rockburst event, in situ stress characteristics, and rockburst proneness are studied in a deep gold mine. The severity of rockburst increases with cover depth at the mine. The main locations of spalling and rockburst events include roof and sidewall. The in situ stress measurement results show this area that is controlled by horizontal constructional pressure, and the self-weight stress also has an important influence. The rockburst mechanism is analyzed from the principal stress and tangential stress. When the maximum tangential stress (MTS) does not exceed 0.4 times UCS of surrounding rock, no obvious disaster in tunnel is found. When the MTS of tunnel is between about 0.4 ~ 0.55 times UCS of rock, the tunnel may suffer spalling. When the MTS of tunnel exceeds 0.55 times UCS of rock, serious failure may occur in tunnel, such as rockburst and large roof collapse. When surrounding rock is relatively hard and complete (high impact energy index, elastic strain energy index, linear elastic energy index, and RQD index), the tangential stress plays a very important role in the rockburst at the mine.

Simulation Study on Spatial Form of the Suspended Roof Structure of Working Face in Shallow Coal Seam

Longwall fully comprehensive mechanized mining is mainly used for the working faces of shallow coal seam with large mining height, which usually have a large suspended roof at the face end. The overhang at the face end leads to stress concentration, which affects the safe mining of the working face. In this paper, we use the 15210 working face with a suspended roof (overhanging area 50~70 m2) of the Zhangjiamao coal mine as study background, with physical simulation, numerical calculation and theoretical analysis, the spatial morphologies and changes in the roof structure at the face ends of the working face in shallow coal seam are obtained, in which the suspended roof increase from the bottom to top, forming step-laminated structures. The caving interval of the suspended roof at the face end is about two times the period weighting interval, and the suspended roof area at the tailgate is smaller than at the headgate. The distribution of the shear and the principal stress field at the face-end region is arc-shaped, and the distribution of the plastic zone shows that the collapse of a suspended ceiling has obvious hysteresis. According to the simplified analysis of the Marcus plate, when the layers of the stepped curved triangular plates increase, the length of the suspended roof on the solid coal side also increases, which is consistent with the results of the physical simulation and numerical calculations. The formation mechanism of the roof at the end of the working face provides a research foundation for the control of roofs found at face ends and further improves the theory of roof structure and the safety mining of suspended roof areas.

Deformation Analysis of the Cable Reinforcement System of Large Section Box Culvert Roof Entry and Downward Penetration

For the underpass railway large-section box culvert jacking and pipe jacking project, the key to ensuring the normal operation of the existing railway is to maintain the smoothness and stability of the track, railway settlement monitoring and line reinforcement, and box culvert and pipe culvert attitude control are the keys to solving this problem. Taking the Beijing-Harbin high-speed railway project under a city road in Beijing as an example, the law of railway track settlement during the implementation of box culvert jacking was analyzed according to real-time monitoring data. The monitoring results show that accelerating the pouring of the bedding and grouting and strengthening the railway subgrade on both sides of the foundation pit can effectively control the settlement of the railway subgrade and reduce the impact of subsequent construction on the railway, and the line renovation and secondary grouting reinforcement can effectively improve the smoothness of the railway. Combined with the comparative analysis of numerical simulation results, the necessity of line refurbishment and rail fastening combination reinforcement in actual construction is verified.

Computational Investigation of Wind Loads on Tilted Roof-Mounted Solar Array

A detailed computational investigation of the wind field around tilted solar modules mounted on a large building roof has been undertaken, utilizing the Reynolds-Averaged Navier-Stokesv (RANS) approach supplied with the SST k − ω turbulence model. The study investigated the flow field for various tilt angle of modules at normal wind directions relative to the wall. Then the shape factors and moment coefficients of modules were explored. The results show that the recirculation vortex generated by the building edge is disintegrated to smaller local vortices. With the increasing of the tilt angle, an increasing number of local vortices emerged at the leading rows, leading to a relatively large wind pressure and shape factor at the corner of the array. In most tilt angles at 0° and 180° wind direction the shape factors are negative. However, for the 40° and 55° tilt angles at 180° wind direction, the shape factors on the lower surfaces are positive, due to the dominating of approaching flow rather than the local vortices. The array is divided into six zones based on the distribution of shape factors. As the shape factors on upper and lower are similar, the shape factors in most zones for tilt angles from 5° to 55° are quite small. However, shape factors in the leading row for 30°, 40° and 55° are relatively large. This indicates that the shading effect of front rows can significantly reduce the shape factors of the rear rows. Compared to the values calculated by Chinese, American and Japanese standards, the shape factors by simulation are quite small. The moment induced by nonuniform wind pressure, which is often ignored in the literature and standards, is quite large at the leading zones, with a maximum of 0.28 for 55° tilt angle. Ignoring the wind induced moment on the leading zones may make the wind resistance design of the solar module support structure unsafe.