This study analyzes the energy impact of applying green roofs on flat roofs of existing buildings,assessing their potential to reduce the demand for non-renewable primary energy for heating and cooling.Through dynamic...This study analyzes the energy impact of applying green roofs on flat roofs of existing buildings,assessing their potential to reduce the demand for non-renewable primary energy for heating and cooling.Through dynamic numerical simulations conducted on two real buildings located near Florence,Italy,and modeled in 130 different European locations,with a particular focus on the Mediterranean climate,it was possible to quantify the energy benefits derived from the application of green roofs on existing structures.The results show that,while the effect on heating is limited,with an average reduction in energy demand of only a few percentage points,the impact on cooling is significantly more pronounced,with average savings of 20%in non-renewable primary energy,particularly in Mediterranean climates with high CDD(cooling degree days)values.The study confirms that green roofs can be an effective solution to improve the energy efficiency of existing buildings with flat roofs in the Mediterranean climate,in line with European goals for reducing CO₂emissions and promoting renewable energy.展开更多
Microstructural heterogeneity of low-permeability sandstone roofs of deep unmineable coal seams due to diagenesis significantly affects rock mechanical behavior,greatly impacting the sealing potential of in situ CO_(2...Microstructural heterogeneity of low-permeability sandstone roofs of deep unmineable coal seams due to diagenesis significantly affects rock mechanical behavior,greatly impacting the sealing potential of in situ CO_(2) sequestration and the structural stability of the geological formation.However,little is known about how the microstructure of different mineral groups influences the multiscale mechanical behavior of deep sandstone.This study proposes a new method for quantitatively characterizing the multiscale mechanical properties of low-permeability sandstone and shows the mechanisms responsible for mechanical failure at the micro-,meso-,and macroscale.Triaxial compression tests and targeted nanoindentation tests were conducted to assess the micro-and macroscale mechanical properties of different types of sandstone.The micro-and macroscale experiments were coupled with numerical simulations of compression using a unified cohesive model based on Voronoi polygons to clarify the multiscale mechanical behavior.The results indicate that quartz,the primary mineral component of the sandstones examined,exhibits the strongest micromechanical properties,followed by feldspar,calcite,and clay minerals.Compared to polycrystalline quartz,monocrystalline quartz has a more stable microstructure and is mechanically stronger.The macro-mechanical properties of tight sandstone samples are weakened by increased microstructural inhomogeneity and larger grain size.This leads to a higher likelihood of splitting damage,characterized by a high degree of discrete and weak stress sensitivity.The major conclusion is that the positive rhythm lithofacies of medium-grained sandstone to siltstone are the most favorable for efficient CO_(2) sequestration in deep unmineable coal seams.展开更多
The present paper investigates the methods for estimating the maximum(positive)and the minimum(negative)peak wind force coefficients on domed free roofs based on the quasi-steady theory and the peak factor method,in w...The present paper investigates the methods for estimating the maximum(positive)and the minimum(negative)peak wind force coefficients on domed free roofs based on the quasi-steady theory and the peak factor method,in which the experimental results obtained from our previous studies(2019,2025)are used.Focus is on the distributions of the peak wind force coefficients along the centerline parallel to the wind direction considering that domed free roof is an axisymmetric body.Empirical formulas are provided to the distributions of mean wind force coefficient,RMS(root mean square)fluctuating wind force coefficient and peak factors as a function of the rise/span ratio of the roof and the turbulence intensity of the approach flow in the along-wind direction at the mean roof height.The proposed methods are validated by the experimental results for the peak wind force coefficients.The methods would provide useful information to structural engineers when estimating the design wind loads on cladding/components of domed free roofs.展开更多
Green roofs play a vital role in promoting sustainable urban development and achieving carbon neutrality by enhancing carbon sequestration, oxygen release, and efficiency of land use. Despite these benefits, living ro...Green roofs play a vital role in promoting sustainable urban development and achieving carbon neutrality by enhancing carbon sequestration, oxygen release, and efficiency of land use. Despite these benefits, living roof coverage in China remains limited. To address the challenges in policy formulation, operational monitoring, and the absence of multi-scale retrofit strategies supported by robust assessment methods, this study develops a comprehensive evaluation framework. The framework integrates vector data, building age information, and point-of-interest(POI) data, and applies an optimized Prophet model to classify six major climate zones. This approach facilitates the selection of appropriate plant species and substrates while quantifying the potential for carbon sequestration and oxygen release. An assessment of 90 cities reveals approximately 1.3861 billion square meters of rooftop area suitable for green roof implementation, with an estimated annual carbon sequestration potential of 67.30 million tons and oxygen release of 30.36 million tons. Commercial buildings contribute significantly, comprising 65% of the total suitable area. Climate zones 2 and 3 exhibit the most favorable outcomes. The current study provides a reliable quantitative reference for evaluating the carbon sequestration and oxygen release capacities of green roofs and supports the formulation of effective retrofit policies.展开更多
This study numerically involves the performance of thermal insulation of different types of composite walls and roofs to demonstrate the best model that can be used for energy-efficient building construction in Iraq.T...This study numerically involves the performance of thermal insulation of different types of composite walls and roofs to demonstrate the best model that can be used for energy-efficient building construction in Iraq.The mathematical model is solved by building its code using the Transmission Matrix Method in MATLAB software.The weather data of 21st July 2022 in Baghdad City/Iraq is selected as a test day.The wall types are selected:the first type consists of cement mortar,brick,and gypsum,the second type consists of cement mortar,brick,gypsum,and plaster and the third type consists of cement mortar,brick,gypsum,air cavity,and sheathing timber.The roof types are chosen:the first type consists of reinforced concrete,gypsum,and plaster,and the second type consists of the precast concrete flag,river sand,tar,reinforced concrete,gypsum,and plaster.The obtained solutions are compared with previous studies for the same city but with different types of walls and roofs.The findings display that the second and third types of walls reduce the entry heat flux by 4%and 10%as compared to the first type of wall.Also,the results indicate that the second type of roof reduces the entry heat flux by 21%as compared to the first type of roof.The results confirm that the best models of walls and roofs in Iraq are the third and second types,respectively,as compared to other models and hence,the performance of insulation material strongly depends on the materials used while building them.展开更多
In order to solve the problem that current theory models cannot accurately describe thick-hard roof(THR)elastic energy and assess the mine tremor disasters,a theoretical method,a Timoshenko beam theory on Winkler foun...In order to solve the problem that current theory models cannot accurately describe thick-hard roof(THR)elastic energy and assess the mine tremor disasters,a theoretical method,a Timoshenko beam theory on Winkler foundation was adopted to establish the THR’s periodic breaking model.The superposition principle was used for this complex model to derive the calculation formulas of the elastic energy and impact load on hydraulic supports.Then,the influence of roof thickness h,cantilever length L_(1),and load q on THR’s elastic energy and impact load was analyzed.And,the effect of mine tremor disasters was assessed.Finally,it is revealed that:(1)The THR’s elastic energy U exhibits power-law variations,with the fitted relationships U=0.0096L_(1)^(3.5866^),U=5943.9h^(-1.935),and U=21.049q^(2).(2)The impact load on hydraulic supports F_(ZJ) increases linearly with an increase in the cantilever length,thickness,and applied load.The fitted relationships are F_(ZJ)=1067.3L_(1)+6361.1,F_(ZJ)=125.89h+15100,and F_(ZJ)=10420q+3912.6.(3)Ground hydraulic fracturing and liquid explosive deep-hole blasting techniques effectively reduce the THR’s cantilever length at periodic breakages,thus eliminating mine tremor disasters.展开更多
Ground hydraulic fracturing plays a crucial role in controlling the far-field hard roof,making it imperative to identify the most suitable target stratum for effective control.Physical experiments are conducted based ...Ground hydraulic fracturing plays a crucial role in controlling the far-field hard roof,making it imperative to identify the most suitable target stratum for effective control.Physical experiments are conducted based on engineering properties to simulate the gradual collapse of the roof during longwall top coal caving(LTCC).A numerical model is established using the material point method(MPM)and the strain-softening damage constitutive model according to the structure of the physical model.Numerical simulations are conducted to analyze the LTCC process under different hard roofs for ground hydraulic fracturing.The results show that ground hydraulic fracturing releases the energy and stress of the target stratum,resulting in a substantial lag in the fracturing of the overburden before collapse occurs in the hydraulic fracturing stratum.Ground hydraulic fracturing of a low hard roof reduces the lag effect of hydraulic fractures,dissipates the energy consumed by the fracture of the hard roof,and reduces the abutment stress.Therefore,it is advisable to prioritize the selection of the lower hard roof as the target stratum.展开更多
The increasing demand for green spaces in cities underscores the urgent need for sustainable solutions to reduce the ecological impact of urban areas.This research focuses on converting unused rooftops into extensive ...The increasing demand for green spaces in cities underscores the urgent need for sustainable solutions to reduce the ecological impact of urban areas.This research focuses on converting unused rooftops into extensive green roofs in Nador,Morocco,offering an innovative approach to enhancing outdoor thermal comfort in this region.Several advanced techniques were used,including photogrammetric restitution(for creating land use maps),integration of light detection and ranging data(for three-dimensional urban modeling),and meteorological data collection(for modeling urban climate conditions).The urban-multiscale-environmental-predictor solar and longwave environmental irradiance geometry(UMEP-SOLWEIG)model was crucial for precisely evaluating the thermal performance of green roofs and their influence on urban microclimates.This model considers considered various parameters,such as the sky view factor,wall height and aspect,and shading conditions,for accurate,comprehensive analysis.Additionally,for accurate,comprehensive analysis,a comparative evaluation was performed between the UMEP-SOLWEIG and ENVI-met models to assess the UMEP SOLWEIG results.The findings were notable,demonstrating a substantial reduction(averaging over 3℃)in the mean radiant temperature on 60%of rooftops,covering 55%of the total surface area.This highlighted the effectiveness of green roofs in improving outdoor thermal comfort.Furthermore,green roofs were closely associated with reductions in air-conditioning energy consumption,with considerable reductions ranging from 17.53%to 43.82%.These savings translated to estimated financial benefits ranging from USD 1.63-4.07 million.These figures clearly verified the notable economic impact of green roofs despite their initially high costs(approximately USD 84.44 million).These potential long-term savings indicated that these investments are financially viable in the long run.The collected data were used to create thermal maps of the area using geographic-information-system tools.A thermal cadaster specific to green roofs was also developed,accessible online through Web mapping.Overall,this approach facilitates decision-making in urban planning by providing visual information on thermal variations,thereby aiding in the precise planning of measures against urban heat and promoting the use of green roofs to reduce environmental impact.展开更多
The stiffness required for the normal operation of membrane roof comes from the application of pre-tension. When the pre-tension is too small, it is easy to cause instability under the action of wind load, which leads...The stiffness required for the normal operation of membrane roof comes from the application of pre-tension. When the pre-tension is too small, it is easy to cause instability under the action of wind load, which leads to excessive deformation of the roof and local or overall damage. In order to ensure that the membrane roof is always in normal use state in the airflow field, this paper takes the membrane pretension as the control parameter to study the value of safety pretension of closed membrane roof. According to the theory of large deflection of membrane and Galerkin method, the nonlinear vibration differential equation of membrane roof under static wind is established, and the critical state of safe working of membrane roof is determined by judging the stability of the solution of the equation, and the expression of critical wind speed is obtained. By establishing the inequality relationship between local design wind speed and critical wind speed, the safety pretension limit of membrane roof under specific site can be obtained. The research shows that the safety pretension limits of closed membrane roofs are different in different areas under different design return periods. In addition, the value of safety pretension is related to the film geometry.展开更多
This experimental study is a contribution to the search for solutions to reduce indoor heat gain through sheet metal roofing in hot weather. It has evaluated the thermal impact of two different sheet metal roofs insid...This experimental study is a contribution to the search for solutions to reduce indoor heat gain through sheet metal roofing in hot weather. It has evaluated the thermal impact of two different sheet metal roofs inside of two identical test buildings in sunny weather and cloudy weather conditions. Test building 1 has a single sheet corrugated roof and the building 2 is covered with roof made from top to bottom with corrugated sheet metal, a 12 mm thick serpentine copper tube in which water is circulated, a sheet of aluminium foil acting as a heat reflector, a 4 cm thick polystyrene panel and a 1.5 cm thick plywood. A maximum reduction of 15.1˚C in the temperature of the inner face of the test Building 2 roof was obtained comparatively to the temperature of the inner face of the test Building 1 roof consisting of a single sheet of metal at the warmest hours. In addition, the simple corrugated sheet metal roof of the test building generates high and varied temperatures inside the building. Whereas the proposed heat recovery roof favours low and relatively uniform temperatures inside the building. The proposed sheet metal roof construction technique is very effective in reducing the heat gain through the roof considerably;thus improving the thermal comfort inside sheet metal roofed dwellings. Hot water has been produced by recovering heat from the metal sheet of the roof of test building 2. The temperature of the hot water produced reached of 39˚C. This study could be also an alternative for the reduction of energy consumption due to the use of mechanical means for cooling of sheet metal roofed houses and the reduction of the use of fossil fuels for domestic hot water production.展开更多
Based on the characteristics of membrane structures and the air influence factors,this paper presented a method to simulate the air aerodynamic force effects including the added air mass,the acoustic radiation damping...Based on the characteristics of membrane structures and the air influence factors,this paper presented a method to simulate the air aerodynamic force effects including the added air mass,the acoustic radiation damping and the pneumatic stiffness.The infinite air was modeled using the acoustic fluid element of commercial FE software and the finite element membrane roof models were coupled with fluid models.A comparison between the results obtained by FE computation and those obtained by the vibration experiment for a cable-membrane verified the validity of the method.Furthermore,applying the method to a flat membrane roof structure and using its wind tunnel test results,the analysis of nonlinear wind-induced dynamic responses for such geometrically nonlinear roofs,including the roof-air coupled model was performed.The result shows that the air has large influence on vibrating membrane roofs according to results of comparing the nodal time-history displacements,accelerations and stress of the two different cases.Meantime,numerical studies show that the method developed can successfully solve the nonlinear wind-induced dynamic response of the membrane roof with aerodynamic effects.展开更多
The wind pressure pulse events, among the most important characteristics of wind pressure fluctuations on large-span flat roofs, were investigated by wind tunnel tests in this paper. Incorporating the formation mechan...The wind pressure pulse events, among the most important characteristics of wind pressure fluctuations on large-span flat roofs, were investigated by wind tunnel tests in this paper. Incorporating the formation mechanism of wind pressure pulse events, the peak over threshold method was employed to study properties of this kind of events. The event duration time, the energy contribution, the number of the pulse events, and the distribution of average peak pressure were calculated. Probability density functions of some typical samples in separation region were also given. Results show that the non-Gaussian roof pressure is strong in the flow separation region owing to the wind pressure pulse events. Evaluations of the extreme peak pressures, which can be determined by the peak over threshold method effectively, are important to the design of building cladding.展开更多
This standard specifies the sort, technical requirement, test method, inspection rules, marking, packing, transportation, storage and quality certification of high alumina refractory bricks for electric arc furnace ro...This standard specifies the sort, technical requirement, test method, inspection rules, marking, packing, transportation, storage and quality certification of high alumina refractory bricks for electric arc furnace roofs.展开更多
The purpose and context for the study relates to urban growth. Australian cities are experiencing particularly rapid urbanization, taking the form of land clearing to accommodate outward expansion as well as developin...The purpose and context for the study relates to urban growth. Australian cities are experiencing particularly rapid urbanization, taking the form of land clearing to accommodate outward expansion as well as developing to higher densities in existing urban areas. Both forms of development degrade native biodiversity, resulting in loss of vegetation with the possibility that the remnant indigenous plants will become locally extinct. One endangered ecological community in Sydney, the Eastern Suburbs Banksia Scrub (ESBS), still survives along some sections of Sydney’s heavily urbanized coastline. At the time of European settlement, the ESBS covered approximately 5300 ha, but it is now a highly fragmented 146 ha across 24 sites with some sites under imminent threat of development. Conservation legislation enacted by the state of New South Wales (NSW), Australia has declared the ESBS as critically endangered. Despite recovery plans, in 2016 the NSW Threatened Species Scientific Committee indicated that the community faces an extremely high risk of extinction in Australia in the immediate future. A practical option in the face of declining open space in our cities is to examine the potential of urban rooftops for conserving and propagating threatened or endangered flora. While there is a limited amount of international research on using green roofs for endangered plant protection, there is no information from Australia about how green roofs perform in this geographic region. The approach taken in this research has been firstly, to review the current academic and “grey” literature from a global perspective to identify options for conserving endangered flora on green roofs. We derive an evidence-based research protocol to be used to test the green roof environment in Sydney for propagating the endangered ESBS. We establish the general applicability of green roofs for protecting vanishing flora through the literature review and conclude that our research design will be a suitable framework for the task for monitoring growth and germination performance over the ESBS community’s development cycle, with the longer-term objective of establishing a viable rooftop seed orchard.展开更多
Pressure and proximity measurements made in a tunnel indicate that a typical vehicle passage produced on the tunnel roof an initial pressure increase of small magnitude,followed by a sharp and more substantial drop in...Pressure and proximity measurements made in a tunnel indicate that a typical vehicle passage produced on the tunnel roof an initial pressure increase of small magnitude,followed by a sharp and more substantial drop in pressure below atmospheric.The magnitude of the pressure drop was found to increase with smaller clearances between the vehicle top and the tunnel roof,consistent with the Bernoulli relation and the vehicle speed.The dynamic pressures potentially may have significant effects on the vibration and noise environments on the lower floors of“air rights construction”buildings that span highways.展开更多
According to the engineering features of subgrade cave roof in karst region, the clamped beam model of subgrade cave roof in karst region was set up. Based on the catastrophe theory, the cusp catastrophe model for bea...According to the engineering features of subgrade cave roof in karst region, the clamped beam model of subgrade cave roof in karst region was set up. Based on the catastrophe theory, the cusp catastrophe model for bearing capacity of subgrade cave roof and safe thickness of subgrade cave roof in karst region was established. The necessary instability conditions of subgrade cave roof were deduced, and then the methods to determine safe thickness of cave roofs under piles and bearing capacity of subgrade cave roof were proposed. At the same time, a practical engineering project was applied to verifying this method, which has been proved successfu1ly. At last, the major factors that affect the stability on cave roof under pile in karst region were deeply discussed and some results in quality were acquired.展开更多
This work aimed at revealing the mechanism of strong ground pressure behaviour(SGPB)induced by high-position hard roof(HHR).Based on the supporting structures model of HHR,a modified voussoir beam mechanical model for...This work aimed at revealing the mechanism of strong ground pressure behaviour(SGPB)induced by high-position hard roof(HHR).Based on the supporting structures model of HHR,a modified voussoir beam mechanical model for HHR was established by considering the gangue support coefficient,through which the modified expressions of limit breaking span and breaking energy of HHR were deduced.Combined with the relationship between the dynamic-static loading stress of supporting body(hydraulic support and coal wall)and its comprehensive supporting strength,the criteria of ground pressure behaviour(GPB)induced by HHR were discussed.The types of Ⅰ_(1),Ⅰ_(2),Ⅱ_(1),andⅡ_(2) of GPB were interpreted.Results showed that types Ⅰ_(1) and Ⅰ_(2) were the main forms of SGPB in extra-thick coal seam mining.The main manifestation of SGPB was static stress,which was mainly derived from the instability of HHR rather than fracture.Accordingly,an innovative control technology was proposed,which can weaken static load by vertical-well separated fracturing HHR.The research results have been successfully applied to the 8101 working face in Tashan coal mine,Shanxi Province,China.The results of a digital borehole camera observation and stress monitoring proved the rationality of the GPB criteria.The control technology was successful,paving the way for new possibilities to HHR control for safety mining.展开更多
Hanging roofs or high hang-ups.a common problem in sublevel caving mining,usually result in a large ore loss and undermine mining safety.This paper analyzed the formation of a hanging roof and showed that increased co...Hanging roofs or high hang-ups.a common problem in sublevel caving mining,usually result in a large ore loss and undermine mining safety.This paper analyzed the formation of a hanging roof and showed that increased confining pressure and reduced free surface were its main characteristics.In order to break down a hanging roof,a new method based on shock wave collision and stress superposition was developed.In this method,two blastholes containing multi-primer at different positions are simultaneously initiated at first.By doing this,a new free surface and a swell room can be created.After these holes are fired,a long delay time is given to the next blasthole so that the fragments from the first twohole blasting have enough time to fall down.This new method was applied to three hanging roofs in one production area,and all of them were successfully broken down.Field inspection indicated that almost no damage was caused in the nearby drifts/tunnels due to the new method.In addition,the far field vibrations were found to be smaller than the maximum vibrations induced by some other blasts.展开更多
文摘This study analyzes the energy impact of applying green roofs on flat roofs of existing buildings,assessing their potential to reduce the demand for non-renewable primary energy for heating and cooling.Through dynamic numerical simulations conducted on two real buildings located near Florence,Italy,and modeled in 130 different European locations,with a particular focus on the Mediterranean climate,it was possible to quantify the energy benefits derived from the application of green roofs on existing structures.The results show that,while the effect on heating is limited,with an average reduction in energy demand of only a few percentage points,the impact on cooling is significantly more pronounced,with average savings of 20%in non-renewable primary energy,particularly in Mediterranean climates with high CDD(cooling degree days)values.The study confirms that green roofs can be an effective solution to improve the energy efficiency of existing buildings with flat roofs in the Mediterranean climate,in line with European goals for reducing CO₂emissions and promoting renewable energy.
基金supported by the project from the Exploration and Development Research Institute of PetroChina Daqing Oilfield Companyfinancial support from the research by the National Natural Science Foundation of China(42402148)+1 种基金Sichuan Provincial Fund(24NSFSC4997)Guizhou Outstanding Young Science and Technology Talent Program(YQK[2023]012).
文摘Microstructural heterogeneity of low-permeability sandstone roofs of deep unmineable coal seams due to diagenesis significantly affects rock mechanical behavior,greatly impacting the sealing potential of in situ CO_(2) sequestration and the structural stability of the geological formation.However,little is known about how the microstructure of different mineral groups influences the multiscale mechanical behavior of deep sandstone.This study proposes a new method for quantitatively characterizing the multiscale mechanical properties of low-permeability sandstone and shows the mechanisms responsible for mechanical failure at the micro-,meso-,and macroscale.Triaxial compression tests and targeted nanoindentation tests were conducted to assess the micro-and macroscale mechanical properties of different types of sandstone.The micro-and macroscale experiments were coupled with numerical simulations of compression using a unified cohesive model based on Voronoi polygons to clarify the multiscale mechanical behavior.The results indicate that quartz,the primary mineral component of the sandstones examined,exhibits the strongest micromechanical properties,followed by feldspar,calcite,and clay minerals.Compared to polycrystalline quartz,monocrystalline quartz has a more stable microstructure and is mechanically stronger.The macro-mechanical properties of tight sandstone samples are weakened by increased microstructural inhomogeneity and larger grain size.This leads to a higher likelihood of splitting damage,characterized by a high degree of discrete and weak stress sensitivity.The major conclusion is that the positive rhythm lithofacies of medium-grained sandstone to siltstone are the most favorable for efficient CO_(2) sequestration in deep unmineable coal seams.
文摘The present paper investigates the methods for estimating the maximum(positive)and the minimum(negative)peak wind force coefficients on domed free roofs based on the quasi-steady theory and the peak factor method,in which the experimental results obtained from our previous studies(2019,2025)are used.Focus is on the distributions of the peak wind force coefficients along the centerline parallel to the wind direction considering that domed free roof is an axisymmetric body.Empirical formulas are provided to the distributions of mean wind force coefficient,RMS(root mean square)fluctuating wind force coefficient and peak factors as a function of the rise/span ratio of the roof and the turbulence intensity of the approach flow in the along-wind direction at the mean roof height.The proposed methods are validated by the experimental results for the peak wind force coefficients.The methods would provide useful information to structural engineers when estimating the design wind loads on cladding/components of domed free roofs.
文摘Green roofs play a vital role in promoting sustainable urban development and achieving carbon neutrality by enhancing carbon sequestration, oxygen release, and efficiency of land use. Despite these benefits, living roof coverage in China remains limited. To address the challenges in policy formulation, operational monitoring, and the absence of multi-scale retrofit strategies supported by robust assessment methods, this study develops a comprehensive evaluation framework. The framework integrates vector data, building age information, and point-of-interest(POI) data, and applies an optimized Prophet model to classify six major climate zones. This approach facilitates the selection of appropriate plant species and substrates while quantifying the potential for carbon sequestration and oxygen release. An assessment of 90 cities reveals approximately 1.3861 billion square meters of rooftop area suitable for green roof implementation, with an estimated annual carbon sequestration potential of 67.30 million tons and oxygen release of 30.36 million tons. Commercial buildings contribute significantly, comprising 65% of the total suitable area. Climate zones 2 and 3 exhibit the most favorable outcomes. The current study provides a reliable quantitative reference for evaluating the carbon sequestration and oxygen release capacities of green roofs and supports the formulation of effective retrofit policies.
文摘This study numerically involves the performance of thermal insulation of different types of composite walls and roofs to demonstrate the best model that can be used for energy-efficient building construction in Iraq.The mathematical model is solved by building its code using the Transmission Matrix Method in MATLAB software.The weather data of 21st July 2022 in Baghdad City/Iraq is selected as a test day.The wall types are selected:the first type consists of cement mortar,brick,and gypsum,the second type consists of cement mortar,brick,gypsum,and plaster and the third type consists of cement mortar,brick,gypsum,air cavity,and sheathing timber.The roof types are chosen:the first type consists of reinforced concrete,gypsum,and plaster,and the second type consists of the precast concrete flag,river sand,tar,reinforced concrete,gypsum,and plaster.The obtained solutions are compared with previous studies for the same city but with different types of walls and roofs.The findings display that the second and third types of walls reduce the entry heat flux by 4%and 10%as compared to the first type of wall.Also,the results indicate that the second type of roof reduces the entry heat flux by 21%as compared to the first type of roof.The results confirm that the best models of walls and roofs in Iraq are the third and second types,respectively,as compared to other models and hence,the performance of insulation material strongly depends on the materials used while building them.
基金supported by the Chongqing Postdoctoral Special Support(No.2022CQBSHTB1022)the Autonomous General Projects of State Key Laboratory of Coal Mine Disaster Dynamics and Control(No.2011DA105287-MS202209)the State Key Laboratory of Coal Mine Disaster Dynamics and Control Faces the 2030 project(No.2011DA105287-MX2030-202002).
文摘In order to solve the problem that current theory models cannot accurately describe thick-hard roof(THR)elastic energy and assess the mine tremor disasters,a theoretical method,a Timoshenko beam theory on Winkler foundation was adopted to establish the THR’s periodic breaking model.The superposition principle was used for this complex model to derive the calculation formulas of the elastic energy and impact load on hydraulic supports.Then,the influence of roof thickness h,cantilever length L_(1),and load q on THR’s elastic energy and impact load was analyzed.And,the effect of mine tremor disasters was assessed.Finally,it is revealed that:(1)The THR’s elastic energy U exhibits power-law variations,with the fitted relationships U=0.0096L_(1)^(3.5866^),U=5943.9h^(-1.935),and U=21.049q^(2).(2)The impact load on hydraulic supports F_(ZJ) increases linearly with an increase in the cantilever length,thickness,and applied load.The fitted relationships are F_(ZJ)=1067.3L_(1)+6361.1,F_(ZJ)=125.89h+15100,and F_(ZJ)=10420q+3912.6.(3)Ground hydraulic fracturing and liquid explosive deep-hole blasting techniques effectively reduce the THR’s cantilever length at periodic breakages,thus eliminating mine tremor disasters.
基金the National Natural Science Foundation of China(No.51974042)National Key Research and Development Program of China(No.2023YFC3009005).
文摘Ground hydraulic fracturing plays a crucial role in controlling the far-field hard roof,making it imperative to identify the most suitable target stratum for effective control.Physical experiments are conducted based on engineering properties to simulate the gradual collapse of the roof during longwall top coal caving(LTCC).A numerical model is established using the material point method(MPM)and the strain-softening damage constitutive model according to the structure of the physical model.Numerical simulations are conducted to analyze the LTCC process under different hard roofs for ground hydraulic fracturing.The results show that ground hydraulic fracturing releases the energy and stress of the target stratum,resulting in a substantial lag in the fracturing of the overburden before collapse occurs in the hydraulic fracturing stratum.Ground hydraulic fracturing of a low hard roof reduces the lag effect of hydraulic fractures,dissipates the energy consumed by the fracture of the hard roof,and reduces the abutment stress.Therefore,it is advisable to prioritize the selection of the lower hard roof as the target stratum.
文摘The increasing demand for green spaces in cities underscores the urgent need for sustainable solutions to reduce the ecological impact of urban areas.This research focuses on converting unused rooftops into extensive green roofs in Nador,Morocco,offering an innovative approach to enhancing outdoor thermal comfort in this region.Several advanced techniques were used,including photogrammetric restitution(for creating land use maps),integration of light detection and ranging data(for three-dimensional urban modeling),and meteorological data collection(for modeling urban climate conditions).The urban-multiscale-environmental-predictor solar and longwave environmental irradiance geometry(UMEP-SOLWEIG)model was crucial for precisely evaluating the thermal performance of green roofs and their influence on urban microclimates.This model considers considered various parameters,such as the sky view factor,wall height and aspect,and shading conditions,for accurate,comprehensive analysis.Additionally,for accurate,comprehensive analysis,a comparative evaluation was performed between the UMEP-SOLWEIG and ENVI-met models to assess the UMEP SOLWEIG results.The findings were notable,demonstrating a substantial reduction(averaging over 3℃)in the mean radiant temperature on 60%of rooftops,covering 55%of the total surface area.This highlighted the effectiveness of green roofs in improving outdoor thermal comfort.Furthermore,green roofs were closely associated with reductions in air-conditioning energy consumption,with considerable reductions ranging from 17.53%to 43.82%.These savings translated to estimated financial benefits ranging from USD 1.63-4.07 million.These figures clearly verified the notable economic impact of green roofs despite their initially high costs(approximately USD 84.44 million).These potential long-term savings indicated that these investments are financially viable in the long run.The collected data were used to create thermal maps of the area using geographic-information-system tools.A thermal cadaster specific to green roofs was also developed,accessible online through Web mapping.Overall,this approach facilitates decision-making in urban planning by providing visual information on thermal variations,thereby aiding in the precise planning of measures against urban heat and promoting the use of green roofs to reduce environmental impact.
文摘The stiffness required for the normal operation of membrane roof comes from the application of pre-tension. When the pre-tension is too small, it is easy to cause instability under the action of wind load, which leads to excessive deformation of the roof and local or overall damage. In order to ensure that the membrane roof is always in normal use state in the airflow field, this paper takes the membrane pretension as the control parameter to study the value of safety pretension of closed membrane roof. According to the theory of large deflection of membrane and Galerkin method, the nonlinear vibration differential equation of membrane roof under static wind is established, and the critical state of safe working of membrane roof is determined by judging the stability of the solution of the equation, and the expression of critical wind speed is obtained. By establishing the inequality relationship between local design wind speed and critical wind speed, the safety pretension limit of membrane roof under specific site can be obtained. The research shows that the safety pretension limits of closed membrane roofs are different in different areas under different design return periods. In addition, the value of safety pretension is related to the film geometry.
文摘This experimental study is a contribution to the search for solutions to reduce indoor heat gain through sheet metal roofing in hot weather. It has evaluated the thermal impact of two different sheet metal roofs inside of two identical test buildings in sunny weather and cloudy weather conditions. Test building 1 has a single sheet corrugated roof and the building 2 is covered with roof made from top to bottom with corrugated sheet metal, a 12 mm thick serpentine copper tube in which water is circulated, a sheet of aluminium foil acting as a heat reflector, a 4 cm thick polystyrene panel and a 1.5 cm thick plywood. A maximum reduction of 15.1˚C in the temperature of the inner face of the test Building 2 roof was obtained comparatively to the temperature of the inner face of the test Building 1 roof consisting of a single sheet of metal at the warmest hours. In addition, the simple corrugated sheet metal roof of the test building generates high and varied temperatures inside the building. Whereas the proposed heat recovery roof favours low and relatively uniform temperatures inside the building. The proposed sheet metal roof construction technique is very effective in reducing the heat gain through the roof considerably;thus improving the thermal comfort inside sheet metal roofed dwellings. Hot water has been produced by recovering heat from the metal sheet of the roof of test building 2. The temperature of the hot water produced reached of 39˚C. This study could be also an alternative for the reduction of energy consumption due to the use of mechanical means for cooling of sheet metal roofed houses and the reduction of the use of fossil fuels for domestic hot water production.
文摘Based on the characteristics of membrane structures and the air influence factors,this paper presented a method to simulate the air aerodynamic force effects including the added air mass,the acoustic radiation damping and the pneumatic stiffness.The infinite air was modeled using the acoustic fluid element of commercial FE software and the finite element membrane roof models were coupled with fluid models.A comparison between the results obtained by FE computation and those obtained by the vibration experiment for a cable-membrane verified the validity of the method.Furthermore,applying the method to a flat membrane roof structure and using its wind tunnel test results,the analysis of nonlinear wind-induced dynamic responses for such geometrically nonlinear roofs,including the roof-air coupled model was performed.The result shows that the air has large influence on vibrating membrane roofs according to results of comparing the nodal time-history displacements,accelerations and stress of the two different cases.Meantime,numerical studies show that the method developed can successfully solve the nonlinear wind-induced dynamic response of the membrane roof with aerodynamic effects.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50708030 and 90815021)
文摘The wind pressure pulse events, among the most important characteristics of wind pressure fluctuations on large-span flat roofs, were investigated by wind tunnel tests in this paper. Incorporating the formation mechanism of wind pressure pulse events, the peak over threshold method was employed to study properties of this kind of events. The event duration time, the energy contribution, the number of the pulse events, and the distribution of average peak pressure were calculated. Probability density functions of some typical samples in separation region were also given. Results show that the non-Gaussian roof pressure is strong in the flow separation region owing to the wind pressure pulse events. Evaluations of the extreme peak pressures, which can be determined by the peak over threshold method effectively, are important to the design of building cladding.
文摘This standard specifies the sort, technical requirement, test method, inspection rules, marking, packing, transportation, storage and quality certification of high alumina refractory bricks for electric arc furnace roofs.
文摘The purpose and context for the study relates to urban growth. Australian cities are experiencing particularly rapid urbanization, taking the form of land clearing to accommodate outward expansion as well as developing to higher densities in existing urban areas. Both forms of development degrade native biodiversity, resulting in loss of vegetation with the possibility that the remnant indigenous plants will become locally extinct. One endangered ecological community in Sydney, the Eastern Suburbs Banksia Scrub (ESBS), still survives along some sections of Sydney’s heavily urbanized coastline. At the time of European settlement, the ESBS covered approximately 5300 ha, but it is now a highly fragmented 146 ha across 24 sites with some sites under imminent threat of development. Conservation legislation enacted by the state of New South Wales (NSW), Australia has declared the ESBS as critically endangered. Despite recovery plans, in 2016 the NSW Threatened Species Scientific Committee indicated that the community faces an extremely high risk of extinction in Australia in the immediate future. A practical option in the face of declining open space in our cities is to examine the potential of urban rooftops for conserving and propagating threatened or endangered flora. While there is a limited amount of international research on using green roofs for endangered plant protection, there is no information from Australia about how green roofs perform in this geographic region. The approach taken in this research has been firstly, to review the current academic and “grey” literature from a global perspective to identify options for conserving endangered flora on green roofs. We derive an evidence-based research protocol to be used to test the green roof environment in Sydney for propagating the endangered ESBS. We establish the general applicability of green roofs for protecting vanishing flora through the literature review and conclude that our research design will be a suitable framework for the task for monitoring growth and germination performance over the ESBS community’s development cycle, with the longer-term objective of establishing a viable rooftop seed orchard.
文摘Pressure and proximity measurements made in a tunnel indicate that a typical vehicle passage produced on the tunnel roof an initial pressure increase of small magnitude,followed by a sharp and more substantial drop in pressure below atmospheric.The magnitude of the pressure drop was found to increase with smaller clearances between the vehicle top and the tunnel roof,consistent with the Bernoulli relation and the vehicle speed.The dynamic pressures potentially may have significant effects on the vibration and noise environments on the lower floors of“air rights construction”buildings that span highways.
基金Project(50378036) supported by the National Natural Science Foundation of China
文摘According to the engineering features of subgrade cave roof in karst region, the clamped beam model of subgrade cave roof in karst region was set up. Based on the catastrophe theory, the cusp catastrophe model for bearing capacity of subgrade cave roof and safe thickness of subgrade cave roof in karst region was established. The necessary instability conditions of subgrade cave roof were deduced, and then the methods to determine safe thickness of cave roofs under piles and bearing capacity of subgrade cave roof were proposed. At the same time, a practical engineering project was applied to verifying this method, which has been proved successfu1ly. At last, the major factors that affect the stability on cave roof under pile in karst region were deeply discussed and some results in quality were acquired.
基金This work was jointly supported by the National Natural Science Foundation of China(No.51974042)the Shanxi Province Science and Technology Plan Exposed Bidding Project(No.20191101015)+3 种基金the Open Project Program of Key Laboratory of Mine Disaster Prevention and Control(No.JMDPC202102)the Scientific Research Project of Introducing Talents in Guizhou University(No.202045)the Open Project Program of National Engineering Technology Research Center of Development and Utilization for Phosphorus Resources(NECP202210)the Growth Project of Young Scientific and Technological Talents in Universities of Guizhou Province(KY2022139).
文摘This work aimed at revealing the mechanism of strong ground pressure behaviour(SGPB)induced by high-position hard roof(HHR).Based on the supporting structures model of HHR,a modified voussoir beam mechanical model for HHR was established by considering the gangue support coefficient,through which the modified expressions of limit breaking span and breaking energy of HHR were deduced.Combined with the relationship between the dynamic-static loading stress of supporting body(hydraulic support and coal wall)and its comprehensive supporting strength,the criteria of ground pressure behaviour(GPB)induced by HHR were discussed.The types of Ⅰ_(1),Ⅰ_(2),Ⅱ_(1),andⅡ_(2) of GPB were interpreted.Results showed that types Ⅰ_(1) and Ⅰ_(2) were the main forms of SGPB in extra-thick coal seam mining.The main manifestation of SGPB was static stress,which was mainly derived from the instability of HHR rather than fracture.Accordingly,an innovative control technology was proposed,which can weaken static load by vertical-well separated fracturing HHR.The research results have been successfully applied to the 8101 working face in Tashan coal mine,Shanxi Province,China.The results of a digital borehole camera observation and stress monitoring proved the rationality of the GPB criteria.The control technology was successful,paving the way for new possibilities to HHR control for safety mining.
文摘Hanging roofs or high hang-ups.a common problem in sublevel caving mining,usually result in a large ore loss and undermine mining safety.This paper analyzed the formation of a hanging roof and showed that increased confining pressure and reduced free surface were its main characteristics.In order to break down a hanging roof,a new method based on shock wave collision and stress superposition was developed.In this method,two blastholes containing multi-primer at different positions are simultaneously initiated at first.By doing this,a new free surface and a swell room can be created.After these holes are fired,a long delay time is given to the next blasthole so that the fragments from the first twohole blasting have enough time to fall down.This new method was applied to three hanging roofs in one production area,and all of them were successfully broken down.Field inspection indicated that almost no damage was caused in the nearby drifts/tunnels due to the new method.In addition,the far field vibrations were found to be smaller than the maximum vibrations induced by some other blasts.
