Roof Height Research Articles

Vertical life: impact of roof height on beetle diversity and abundance on wildflower green roofs

Abstract Despite their increasing popularity in an urban setting, we still know relatively little in how well-extensive green roofs support biodiversity in terms of vertical connectivity from terrestrial habitats. Most green roof biodiversity studies have not considered whether the roof height affects community composition and abundance of species present. This study focused on evaluating beetle diversity and abundance in relation to roof height, with emphasis on wildflower roofs. The key results of the study confirm previous studies found that extensive wildflower green roofs are capable of supporting fairly rich beetle communities, including some rare/scarce species. However, an increase of roof height was found to negatively impact both beetle abundance and richness, despite all recorded species being well adapted to active flight and thus dispersal. In addition forb cover decreased with roof height which consequently influenced beetle community structure. These results are therefore indicative that further research is required on species communities found on extensive green roofs that are less adapted to active flight and consequently vertical dispersal. This study further highlights the need for vertical and horizontal connectivity between green roofs and the surrounding natural habitats as a management tool to increase the general ecological value of urban green spaces.

Green roof and ground-level invertebrate communities are similar and are driven by building height and landscape context

Abstract Green roofs are increasingly promoted for urban biodiversity conservation, but the value of these novel habitats is uncertain. We aimed to test two hypotheses: (i) green roofs can support comparable invertebrate family and order richness, composition and abundances to ground-level habitats and (ii) green roofs planted with native species from local habitats will support a richer invertebrate community at family and order level than other green roofs. We sampled the invertebrate community on green roofs dominated by native grassland or introduced succulent species in Melbourne, Australia, and compared these to the invertebrate community in ground-level sites close by, and sites with similar vegetation types. The only significant differences between the invertebrate communities sampled on green roofs and ground-level habitats were total abundance and fly family richness, which were higher in ground-level habitats. Second hypothesis was not supported as invertebrate communities on green roofs supporting a local vegetation community and those planted with introduced Sedum and other succulents were not detectably different at family level. The per cent cover of green space surrounding each site was consistently important in predicting the richness and abundance of the invertebrate families we focussed on, while roof height, site age and size were influential for some taxa. Our results suggest that invertebrate communities of green roofs in Melbourne are driven largely by their surrounding environment and consequently the effectiveness of green roofs as invertebrate habitat is highly dependent on location and their horizontal and vertical connection to other habitats.

Modelling Indoor Environmental Conditions in a Commercial Broiler House

Turkey’s poultry industry has experienced significant growth in recent years, resulting in the construction of many new production facilities. It is important to maintain optimum environmental conditions for a profitable production. In this study, temperature, relative humidity and air velocity distribution inside a broiler house were analysed. Computational Fluid Dynamics (CFD) simulations (numerical method) and direct measurements (experimental method) were used to determine the appropriate indoor environmental conditions. Simulated values were validated by comparison with the measured values using the normalised mean square error (NMSE). The measured and predicted parameters of temperature, relative humidity and air velocity at birds’ height, human height, and roof height upon comparison gave average NMSE values of 0.139, 0.181 and 0.090, respectively. The results showed a good agreement between simulated and measured values as obtained NMSE values were less than 0.25. In conclusion, CFD simulation can be used as an alternative method for the analysis of poultry house indoor environment. A better understanding of indoor environment conditions in poultry house provides useful information for manufacturers and end users for better management decisions.

Analysis of peak heat load on the blanket module for JA DEMO

Plasma heat flux in the peripheral plasma reaches the first wall (FW) along a magnetic field line, and it sometimes causes several MW/m2 orders of magnitude high heat flux concentration at narrow region, such as the edge of the blanket module. Thus, to assess and to reduce the heat load is key issue in the DEMO design activity. In this research, a new heat load analysis code is introduced based on the e-folding model. In this code, the decay length λ is changed depending on wall connection length of magnetic field line (defined as the length of magnetic field line from the wall to the wall), and parallel heat flux q// is calculated in each flux tube. This code can calculate the FW heat load simulating actual blanket module shapes. The 0.23 MW/m2 peak heat load at inner midplane in the case of the ideal FW (without gaps between blanket modules) is increased to 22 MW/m2 at toroidal module edge in the case of box shaped module. To shadow the edge and reduce such peak heat load, toroidal, and poloidal roof shaping is applied. Required roof height is analyzed from this code calculation. After shaping, peak heat load is reduced to 1.2 MW/m2. This value is under the allowable value 1.5 MW/m2, and in this case, surface temperature is also less than allowable temperature.

Wind load evaluation approach for building cluster considering effect of neighboring buildings

Wind loading to a building is generally affected by neighboring buildings. Often, such an effect is neglected in case where wind loads to a large number of buildings must be evaluated; e.g. in the context of wind risk assessment for building portfolio. The present paper proposes a simple approach for wind load evaluation of buildings considering the effect of neighboring buildings. The underlying idea is that buildings in a portfolio is divided into clusters according to distances between neighboring buildings. Then, depending on the characteristics of the geometrical locations (edge or inner area) of individual buildings in each cluster, wind loadings to buildings are evaluated. A wind tunnel experiment with a simplistic configuration of a building portfolio is conducted to justify the proposed approach. The result suggests that buildings may be grouped in a same cluster when the distance to adjacent buildings is less than two times of the roof height; wind loadings to the buildings located in inner area up to the third outer layer in a cluster may be reasonably assumed to be identical; the effect of neighboring buildings on wind loading to the buildings located at the outmost and second outer layer becomes negligible when the distance to the neighboring buildings exceeds 14 times of the roof height.

Seismic retrofitting of existing earthen structures using steel plates

During past earthquakes, existing earthen buildings have suffered severe damage or total collapse leading to fatalities and major economic and cultural losses. Poor mechanical properties, out-of-plane instability, lack of seismic diaphragms, and low strength of the connections between structural elements are the most common problems with these types of vernacular constructions. In this research, a novel retrofitting solution, based on steel plates, is proposed to enhance the seismic performance of earthen structures while protecting the life of the occupants and reducing the expected damages. A comprehensive experimental program is conducted to evaluate the seismic behaviour of earthen structural components under both unretrofitted and retrofitted conditions. The experimental program includes four cyclic tests of the proposed connections between steel plates and walls, five cyclic tests of earthen piers, and three full scale shaking table tests of 3.50 m high × 0.60 m thick walls. Observed damage states were related to measured drifts (for cyclic tests) and peak ground accelerations (for dynamic tests). Tests results show that the proposed retrofitting technique substantially increases the stiffness, strength, ductility, and stability of the specimens, which reduces damages and permanent displacements. Retrofitted specimen supported accelerations larger than 1.64g at the roof height without collapse; residual drifts for these demands did not exceed 1.1%.

Community assembly on extensive green roofs: Effects of dispersal‐, abiotic‐ and biotic filtering on the spontaneous species‐ and functional diversity

AbstractQuestionsExtensive green roofs (EGRs) are novel ecosystems and essential tools in mitigating the negative effects of urbanization. However, the extent to which traditional community assembly insights apply to spontaneous plant and trait diversity and composition on EGRs and novel ecosystems in general is unclear: (a) is a dispersal filter present because of EGRs’ fragmented nature (e.g., roof height, urban environment); (b) can we confirm the strong abiotic filtering due to extreme EGR conditions (e.g., limited substrate depth); and (c) does the presence of the planted vegetation lead to biotic filtering?LocationThe Flanders and Brussels region of Belgium.MethodsThe vegetation of 129 EGRs was sampled during a field campaign. Information on local (e.g., substrate, roof height) and regional characteristics (e.g., connectivity indices) were collected and species traits were collected from multiple databases. All data were used to construct (generalized) linear mixed models that tested the effects of the dispersal‐, local abiotic‐ and local biotic filters on plant community formation. Redundancy analysis was used to investigate predictor effects on functional composition and null models were constructed to assess trait divergence/convergence.ResultsOur results show that the spontaneous plant species diversity is not affected by their landscape context (dispersal filtering), while their functional composition is. Additionally, the importance of abiotic filtering is confirmed, as substrate depth and exposure have a strong impact on species diversity and decreasing substrate depth negatively impacts functional diversity. Finally, we show that biotic filtering by increased planted species cover leads to trait divergence, changes in functional composition and reduced cover of spontaneous species.ConclusionsWe find that a broad perspective that includes the regional and local biotic and abiotic environment is needed to assess all factors that influence the vegetation on EGRs. As biotic interactions are present, EGRs should not be considered as static systems.

Validation of the Maxillary Sinus Roof as a Landmark for Navigating the Pediatric Skull Base.

To define a new anatomic relationship in pediatric sinus surgery, assessing the maxillary roof as a constant safe landmark to avoid skull base injury in the pediatric population. Retrospective analysis. Tertiary care children hospital. A retrospective analysis was performed of all computed tomography scans of the sinuses and facial bones at the emergency department of a tertiary children's hospital over the course of a year. Radiographic measurements included the lowest cribriform plate and planum sphenoidale (PS) heights, or posterior skull base when not yet pneumatized, as well as the highest maxillary roof height. The nasal floor was used for reference. Statistics were performed via Shapiro-Wilks test with a P-value of .05 indicating statistical significance. Three hundred and seven unique scans were reviewed (38.9% female; n = 122; P = .58). Age stratification was based on previously described sinus growth patterns. In all patients, the maximum maxillary height was inferior to the lowest measured cribriform lamella and PS (P < .001; CI, 98.5%-99%). Inter- and intrarater reliability and accuracy were verified through blinded review and re-review (ρ = .99 and .98 respectively, P ≤ .001). The validity of sole coronal measurements due to incomplete sagittal reformatting was also confirmed (ρ = 1.00, P ≤ .001). Despite variation in sinus growth and development in children, the current study demonstrated the validity of the maxillary sinus roof as a constant safe landmark in the pediatric population, offering a novel anatomic relationship for teaching safety in performing pediatric sinus surgery. 4.

Novel collector design for enhancing the performance of solar chimney power plant

The collector is an essential element of Solar Chimney Power Plant (SCPP). It converts the solar energy into heat by increase the internal energy of the air. An optimization of the collector design is required to recover further SCPP efficiency and to reduce the large plant area. In the present paper, a novel collector design with double-pass counter flow mode was proposed. For this purpose, a comparison between three models; conventional collector, double-pass collector with parallel flow and double-pass collector with counter flow was carried out using CFD methodology. The realizable k-ε turbulence model and the discrete ordinates (DO) non-grey radiation model were employed in the present simulations. Numerical results were validated for a reference design using test data gathered from a developed prototype built at the National School of Engineers of Sfax, in Tunisia. The distribution of the local fluid characteristics and the heat transfer modes were proven for the proposed systems. In addition, the global SCPP characteristics such as the efficiency and the driving pressure were compared. The effect of the second roof height on the system performance was analyzed for both double-passes collectors. Results show that the proposed designs are clearly affect the SCPP behavior. In fact, the double-passes counter flow collector presents an efficient solution which increases the collector efficiency by 28% comparing to the conventional collector.

Numerical investigations of heat transfer enhancement in a house shaped-corrugated channel: Combination of nanofluid and geometrical parameters

Improving the heat transfer rate is one of the main issues at the design stage of different thermal devices for various industries. In this research, a numerical simulation is performed to investigate the combined influences of nanofluid and various parameters designs of a house-shaped corrugated channel on the thermal and hydraulic performance under uniform heat flux of 10 kW/m2 and Reynolds number range of 10,000–30,000. In respect to the fluid medium, SiO2 nanoparticles are used and investigated with volume fraction up to 0.08. The impacts of geometrical parameters including height-to-width ratio (h/W), pitch-to-length ratio (p/L), and house ratio (e/r) on thermal and hydraulic characteristics are evaluated. The findings show that the (h/W) ratio has more influence on heat transfer promotion than the (p/L) ratio. At Reynolds number 30,000, there is a 16.63% increment in average Nusselt number due to a decrease of the (p/L) ratio from 0.175 to 0.075, while the increment 92.28% is achieved by an increase of the (h/W) ratio from 0.0 to 0.05. Heat transfer increases with roof height (r) and decreases with the vertical height of the house-shaped corrugation (e). The findings detect that a h/W of 0.05 with a p/L of 0.075and e/r = 0.6667 are optimum parameters that showed significant improvement in thermal performance. Moreover, new correlations for the Nusselt number and friction factor were developed and reported. Using nanofluid with the current channel is a useful source of reference to enhance thermal performance and produce more compact heat exchangers.

Fragility analysis of the roof structure of low-rise buildings subjected to tornado vortices

The fragility curves of roof failures for wood-frame low-rise building were developed in this study with the focus on the roof sheathing panels and roof-to-wall connections. Two different nail spacings for roof sheathing panels and three types of roof-to-wall connections were considered. This study focused on the first failure of roof sheathing panels without considering the sequential loss of the sheathing panels, and the unit failure of effective wind zones containing different numbers of roof-to-wall connections. The tornado simulator-based dataset was used for determination of the statistics of wind loads, without considering the translational motion effects of tornado vortices. The results show that the failure probability of roof is dependent on the proximity of a tornado to a building and the opening azimuth on walls. Additionally, the combined effects of pressure drop and aerodynamic interactions dominate the failure modes of roof system. The obtained fragility curves in this study can be used to estimate the maximum tangential wind speed of the tornado vortices and the local oncoming tangential wind speed at roof height. The estimation of tornado intensity using the present results is likely to approach the lower-bound of wind speed estimation in WSEC (2006) report.

Numerical Simulation and Optimization of Wind Effects of Porous Parapets on Low‐Rise Buildings with Flat Roofs

This paper presents a procedure to optimize the porosity of parapets to improve the aerodynamic behavior of low‐rise buildings with flat roofs, by coupling an optimization algorithm and computational fluid dynamics (CFD) simulations. The performance of solid parapets to decrease the wind suctions on flat roofs induced by conical vortices was firstly studied, based on four turbulence closure models (standard k‐ε, RNG k‐ε, SST k‐ω, and RSM). The simulation results were validated by comparing with the wind tunnel data. Additionally, the porous parapet was treated as a momentum sink in the governing momentum equation, and the RSM turbulence model was employed. As a result, six optimization studies focusing on the highest mean suction minimization that consider parapet height were presented. The aim of this paper is to search for the best performing porosity through an automatic CFD‐based optimization methodology. At low relative heights (hp/H = 0.01∼0.05, hp is the parapet height, and H is the roof height), the porous parapet with optimal porosity in between 38.2% and 52.3% seems to be more effective than solid parapets in attenuating high corner suctions generated by conical vortices; however, the solid parapet gives the best performance in the reduction of wind suctions when hp/H ≥ 0.07.

Key Parameters of Gob-Side Entry Retaining in A Gassy and Thin Coal Seam with Hard Roof

Gob-side entry retaining (GER) employed in a thin coal seam (TCS) can increase economic benefits and coal recovery, as well as mitigate gas concentration in the gob. In accordance with the caving style of a limestone roof, the gas concentration and air pressure in the gob were analyzed, and a roof-cutting mechanical model of GER with a roadside backfill body (RBB) was proposed, to determine the key parameters of the GER-TCS, including the roof-cutting resistance and the width of the RBB. The results show that if the immediate roof height is greater than the seam height, the roof-cutting resistance and width of the RBB should meet the requirement of the immediate roof being totally cut along the gob, for which the optimal roof-cutting resistance and width of RBB were determined by analytical and numerical methods. The greater the RBB width, the greater its roof-cutting resistance. The relationship between the supporting strength of the RBB and the width of the RBB can be derived as a composite curve. The floor heave of GER increases with increasing RBB width. When the width of the RBB increased from 0.8 m to 1.2 m, the floor heave increased two-fold to 146.2 mm. GER was applied in a TCS with a limestone roof of 5 m thickness; the field-measured data verified the conclusions of the numerical model.

Street-canyon pollution with respect to urban-array complexity: The role of lateral and mean pollution fluxes

The prediction of pollution within street canyons remains challenging due to the complexity of turbulent flows in urban environments. To improve our understanding of these flows and their relation to the ventilation of street-canyons, we studied pollution fluxes through all street-canyon openings and their balance with respect to urban-array complexity using large-eddy simulations (LES). We validated the LES with wind-tunnel measurements using mean velocities and concentrations and the mean total and turbulent pollution fluxes at the top and lateral openings of the street canyons with either uniform or nonuniform heights and pitched roofs. The LES confirm and extend recent findings about the importance of mean horizontal pollution fluxes for pollutant transport within a street network. The mean fluxes have at least the same dominance as the turbulent ones in case of lateral openings. In case of top openings, the mean fluxes clearly dominate if openings at the roof eaves are selected. While pollutant removal and entrainment through lateral openings are negligible in case of uniform canyons, they are notable in case of nonuniform canyons. We demonstrate that urban roof height nonuniformity does not necessarily enhance the street-canyon ventilation because it worsens (by a factor of 1.1) or improves (by a factor of 1.5) the ventilation compared with the urban uniform height.

An Assessment of the Wind Power Generation Potential of Built Environment Wind Turbine (BEWT) Systems in Fort Beaufort, South Africa

The physical and economic sustainability of using built environment wind turbine (BEWT) systems depends on the wind resource potential of the candidate site. Therefore, it is crucial to carry out a wind resource assessment prior to the deployment of the BEWT. The assessment results can be used as a referral tool for predicting the performance and lifespan of the BEWT in the given built environment. To date, there is limited research output on BEWTs in South Africa, with available literature showing a bias towards utility-scale or conventional ground-based wind energy systems. This study aimed to assess the wind power generation potential of BEWT systems in Fort Beaufort using the Weibull distribution function. The results show that Fort Beaufort wind patterns can be classified as fairly good and that BEWTs can best be deployed at 15 m for a fairer power output as roof height wind speeds require BEWTs of very low cut-in speeds of at most 1.2 ms − 1 .

Influence Mechanism of Main Roof Height on Surrounding Rock Stability of Gob-Side Entry Driving

Influence Mechanism of Main Roof Height on Surrounding Rock Stability of Gob-Side Entry Driving

A parametric study of the effect of roof height and morphology on air pollution dispersion in street canyons

We investigate the effect of conventional pitched roofs on ventilation and pollution in street canyons using Computational Fluid Dynamics and a parametric approach. We studied parallel street canyons with several street morphologies, created by assigning a set of streets with pitched roofs, and varying their pitch and arrangement for three different height-to-width aspect ratios. The distribution of flow properties and pollution concentrations within the street canyons are examined and the effect of different parameter combinations is assessed. We find the relationship between these properties and the street morphology to be complex and case specific.For most morphologies, the pitched roofs lead to higher average pollution concentrations, and in some cases to pollution hotspots near emission sources especially on the leeward side. The pitched roofs are rarely beneficial to ventilation of the street canyons, but a few roof arrangements lead to reduced concentrations on the windward side. Roof slope is shown to significantly relate to both average pollution concentrations and their distribution inside the street; in some street geometries more than others. The results have implications for pedestrian and residential pollution exposure, and for conservation of building facades on historical buildings.

Buzzing on top: Linking wild bee diversity, abundance and traits with green roof qualities

Green roofs are potentially valuable habitats for plants and animals in urban areas. Wild bees are important pollinators for crops and wild plants and may be enhanced by anthropogenic structures, but little is known about wild bees on green roofs in cities. This study investigates the effects of green roof qualities (floral resources, substrate character and depth, roof height and age) on wild bee diversity, abundance and traits (nesting type, sociality, pollen specialisation, body size) on green roofs in Vienna. Nine green roofs were sampled monthly between March and September 2014 by a semi quantitative approach. Wild bees were collected in pre-defined sub-areas for the same amount of time and floral resources were recorded. Over all green roofs, 992 individuals belonging to 90 wild bee species were observed. Wild bee diversity and abundance was strongly positively affected by increasing forage availability and fine substrates. Wild bees on roofs were characteristically solitary, polylectic and 8.3–11.2 mm. Regarding nesting type, the percentage of above-ground nesting bees was higher compared to the common species composition in Middle Europe. Ground-nesting wild bees were mainly eusocial, smaller (6.4–9.6 mm) and positively affected by roofs with fine substrates. During June, when forage availability by wildflowers on roofs was “low” (5–15% flower coverage), flowering Sedum species were an important forage resource. We conclude that wild bee diversity and abundance on green roofs are enhanced by floral resources. Furthermore, the installations of areas with finer and deeper substrates benefit ground nesting and eusocial wild bees.

Characteristics of the den trees of the yellow-bellied glider in western Victoria

Effective management of tree-hollow-dependent wildlife is enhanced by detailed knowledge of the trees used for shelter and breeding. We describe the characteristics of 52 den trees and hollows (cavities) used by the yellow-bellied glider (Petaurus australis) in the south-west of its geographic range. We compared the following attributes of den trees to reference trees: tree height, diameter at breast height, hollow entrance height, hollow entrance diameter, cavity diameter, cavity depth, cavity roof height and cavity wall thickness. Dens and reference trees showed a highly significant multivariate difference (P&amp;lt;0.001), with these variables explaining 64% of the variance. Univariate analyses revealed that hollow entrance height was significantly different between den trees (9.0±0.5m) and reference trees (5.5±0.3m). While not significant, den trees tended to have narrower hollow entrances, deeper cavities and thinner walls than reference trees; cavities used by yellow-bellied gliders, on average, measured 36.8cm deep and 18.0cm in diameter, and had entrances 10.6cm in diameter. These observations should assist forest management for this species.

Assessment of depth of olfactory fossa in pre-functional endoscopic sinus surgery computed tomography scan of paranasal sinuses

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; &lt;span lang="EN-GB"&gt;To evaluate the olfactory fossae depth according to the Keros' classification on pre functional endoscopic sinus surgery (pre-FESS) and determine the incidence and degree of asymmetry in the height of the ethmoid roof in the population of western Maharashtra&lt;/span&gt;&lt;span lang="EN-IN"&gt;. &lt;/span&gt;&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; &lt;span lang="EN-GB"&gt;Retrospective analysis of 200 multidetector CT studies (400 sides) of paranasal sinuses performed in between January to August, 2017&lt;/span&gt;&lt;span lang="EN-IN"&gt;. &lt;/span&gt;&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; &lt;span lang="EN-GB"&gt;According to the Keros’ classification, the incidence of different types of olfactory fossae was as follows: type I: 18.5%, type II: 74.5% and type III: 7%. Asymmetry in the ethmoid roof height was found in 11.5% of cases&lt;/span&gt;&lt;span lang="EN-IN"&gt;. &lt;/span&gt;&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; &lt;span lang="EN-GB"&gt;Keros’ type II was the commonest followed by type I and type III. There was asymmetry in the depth of the olfactory fossae in 11.5% cases. There was no significant gender predilection as far as type and asymmetry were considered&lt;/span&gt;&lt;span lang="EN-IN"&gt;.&lt;/span&gt;&lt;/p&gt;