Flat-roofed Buildings Research Articles

Evaluation of Reproductive Success in Red Wattled Lapwing (Vanellus indicus) in two Diverse Habitats of Jammu (J&K)

The present study is an attempt to analyse the reproductive success in Red Wattled Lapwing (Vanellus indicus) belonging to Order Charadriiformes, by comparing two nesting sites in Jammu. The nesting sites taken under consideration were open agricultural fields and the top of flat roofed buildings. The breeding season ranged from March to August with average clutch size of 3.53 ± 0.56 eggs (n=30) and an incubation period of 28-30 days. The most preferred site for nesting was found to be agricultural fields near some water source because of availability of food. In agricultural fields due to drying up of water source during peak summer, the scarcity in food resources for the young ones was noted thereby leading to the mortality of young ones of Red Wattled Lapwing, whereas it was also observed that on roof tops, eggs or hatchlings were easily predated by predators like monitor and the young ones were not able to land safely on the ground from such a height which caused their death.

Wind-tunnel simulations of wind influence on snow load distribution on roofs

The paper summarizes the problem of snow load prediction on building roofs, the importance of wind action in context of this load and the scope of wind tunnel applications in such research with more detailed description of experimental stand in Cracow University of Technology. Author reports the scope of experimental and theoretical research on snow load carried out over the years 2004-2012 in the boundary layer wind tunnel located at Wind Engineering Laboratory CUT. The research were conducted in the course of design processes on three models of arena-like buildings with large roofs, and one research on more general flat roof building.

Determination of the Average Wind Pressure of Circular Flat and Saddle Roof Building Based on the Numerical Wind Tunnel Method

For numerical wind tunnel method has the advantages of low cost, fast speed, the more comprehensive results, the paper using CFD knowledge and the FLUENT software, using RSM turbulence model, SIMPLE algorithm, simulation class D landform, to have numerical simulation of average wind pressure coefficient for of the circular planar and saddle roof building ,which the current code for the design of building structures did not give, to provide reference for determining the average wind pressure coefficient of the circular planar and saddle roof building .

Aspects of Designing Education Buildings in a Conservation Area: A Case Study of a Building Designed for the School of Civil Engineering at the University of Warmia and Mazury in Olsztyn

Designing architectural objects in a conservation area usually involves many problems, whose solution most often means complying with a series of restrictions, which pertain to elements of urban and architectural design. Creating spatial connections between the new and the existing, listed architecture is not an easy task. Many historic locations experience architectural chaos, which ensues from inapt attempts at combining these two types of architecture and the historic part of the academic campus in Kortowo is a good example in this resepct. This paper presents the architectural, structural and services design problems encountered while working on a design of an education and laboratory building localized in a conservation area. The building in question is to replace the existing, one-storey and flat-roofed building, which will be demolished. The main obstacles to designing the building caused by the conservation requirements were how to adapt the new building’s functions to the specific character of the civil engineering course of study and how to create an architectural form that would fuse with the historic shape of this part of the academic campus. The oldest part of the campus, which has been designated as a conservation area, in practice excludes construction of larger buildings on undeveloped land. This, however, does not mean that the area is completely closed to possible and, in some cases, necessary investment projects. New constructions, in compliance with the local development plan, should eliminate the buildings whose form, plan and architecture introduce discord to the historically defined space.

An assessment of construction details as indicators of the environmental impact of materials used on the “skin” in Greek cities

PurposeConstruction materials mostly affect the environment during the first stages of their life cycle. Their placement during the construction stage is of equal importance as it affects their environmental impact during the stage of use and the final stage of demolition and rejection. The purpose of this paper is to analyse the environmental impact of different construction details, which are typically used for different city surfaces in Greece.Design/methodology/approachThe analysis of the environmental impact of construction details is both quantitative and qualitative. The quantitative analysis is mainly based on embodied energy calculations of different possibilities of placement. The qualitative analysis of the different construction details considers other environmental issues, such as the water cycle in cities and the possibility of reuse and recycling, which are strongly influenced by the way materials are attached to the building shell or general substrate. All the data are gathered from bibliographical sources.FindingsFor urban open spaces and flat roofed buildings, the placement of various materials with and without the use of cement‐based mortars reveals significant differences in the environmental impact. The same applies to building façades with the current construction (cement‐based mortars or synthetic resins) compared to the ventilated façade system.Practical implicationsArchitects and designers can use the methodology and the findings of this study in order to carefully design the construction details of building façades and flat roofs, and urban open spaces.Originality/valueThe study points out the significance of the construction stage in the evaluation of the environmental impact of materials in Greece, where there is extensive use of cement mortars and concrete in the construction of the paving of urban open spaces.

Peak normal stresses and effects of wind direction on wind load combinations for medium-rise buildings

In order to examine wind load combinations, fluctuating surface pressure measurements are made for flat roof building models with square or rectangular plans. The fluctuating pressures are integrated over all their surfaces and results are obtained of along-wind force, across-wind force, vertical force, along-wind overturning moment, across-wind over-turning moment and torsional moment on their frames. The maximum wind force component and other simultaneously observed wind force components are examined, and some interesting facts regarding the effects of wind direction are discussed. In order to directly check the wind load combination effects, the maximum normal stresses in column members of simple frame models are examined, and a wind load combination factor is proposed.

Thermal analysis of vaulted roofs

In hot arid regions, cooling buildings by passive techniques is very important regarding energy saving and the need to keep clean the environment. In such areas, domed and vaulted roofs are widely used for centuries, such as in the Middle East region and central part of Iran. In this article analysis is made to explore east–west direction of wind flow around north–south vaulted roofs and flat roof buildings. Combined convection and solar radiation over the roofs is considered to studying thermal performances of vaulted roofs and comparing their heat transfer with flat roofs. Two-dimensional RNG k– ɛ turbulence model is incorporated to predict turbulent flow field as well as separation and recirculating patterns around the vaulted roofs and flat roof buildings. Solar radiation distribution over the roofs is determined based on an appropriate model applicable to hot arid regions of Iran. Pressure differences above the vaulted roof are compared with flat roof for various rim angles and different wind speeds. Heat transfer to the building with respect to time is determined for a certain inside ceiling design temperature, various wind flows and vault shapes, and results are compared with corresponding flat roof. It was found that daily average heat flux for all vaulted roofs, except vaulted roof of rim angle 180° is less than flat roof and it reduces further by increasing wind speed.

C203 低層建物に作用する風力成分と流速場

In this paper, fluctuating surface pressure measurements are made for four flat roofed building models with square or rectangular plans in order to examine wind load combinations. The fluctuating pressures are integrated over all their surfaces and results are obtained as along-wind force, crosswind force, vertical force and torsional moment their frames. The maximum wind force in consideration of the wind direction component and other simultaneously observed wind force components are examined, and some interesting facts regarding the wind force combinations are discussed on the basis of absolute value correlations, phase-plane expressions and so on. This investigation concurrently measured wind pressure applied to a wall surface and the resulting wind flow field around the building using a wind pressure model and DPIV systems. Data obtained through the measurements enabled identification of the wind flow field around the building that results from the maximum and minimum wind force applied to it.

Three-dimensional linearised Euler model simulations of sound propagation in idealised urban situations with wind effects

A three-dimensional numerical time-domain model based on the linearised Euler equation is applied to idealised urban situations with elongated, isolated buildings beside a straight street with sound emissions. The paper aims at the investigation of principle relationships between the source–receiver geometry (street and building facades) and sound propagation under the consideration of ground and wind. By applying cyclic lateral boundary conditions for either one or both horizontal co-ordinates, two different idealised urban environments were considered: a single street and parallel streets. Numerical experiments were performed to elaborate the effects of different roof types, ground properties, wind flow, and turbulence in both urban environments with the focus on the back facades (‘quiet’ sides) of the buildings. As a result it was found that the back facades of flat-roof buildings are quieter than those of hip roof buildings despite equal cross-cut areas. The wind effect (resulting in quieter upwind and louder downwind facades) is more pronounced for hip-roof buildings. In the case of parallel streets upwind facades are slightly louder than downwind facades because they are simultaneously exposed to downwind propagating sound from the next parallel street.

Thermal performance of non air-conditioned buildings with vaulted roofs in comparison with flat roofs

Vaulted or domed roofs have been frequently adopted by builders and architects throughout the Middle East and other hot dry areas. However, the thermal performance of such buildings under hot dry climatic conditions has rarely been quantitatively studied. In this paper, a detailed finite element model for the investigation of the thermal performance of non air-conditioned buildings with vaulted roofs (VR) is suggested based on two-dimensional unsteady heat transfer in such roofs and solar geometry. This model allows a comparison of the thermal performance of non air-conditioned buildings with a VR and a flat roof (FR) under different climatic conditions. Results obtained by numerical calculation show that, irrespective of building type the VRs are applied to, buildings with a VR have lower indoor temperatures as compared to those with a FR. The reason is that such roofs dissipate more heat than a FR does by convection and thermal radiation at night due to the enlarged curved surfaces. This implies that such roof forms are suitable for buildings located in hot dry regions but not for those located in hot humid areas, and reasonably explains why curved roofs have been extensively adopted by builders and architects in the hot dry areas in the past. However, with the decrease in the half rim angle of a VR, the difference of indoor thermal condition between a VR and a FR building becomes small and insignificant. Results also indicate that the indoor air temperature is slightly influenced by the half rim angle θ 0 and the orientation φ v of the VR. To be effective to create a favorable thermal condition inside buildings with a VR under hot dry climatic conditions, the half rim angle of a VR should be θ 0>50°, instead of θ 0 < 5 0 ∘ , which is the optimal half rim angle of a VR of air-conditioned buildings, as found by the present authors in a previous study.

04/00988 Demand controlled ventilation for office cubicles — can it be profitable?: Mysen, M. et al. Energy and Buildings, 2003, 35, (7), 657–662

Vaulted or domed roofs have been frequently adopted by builders and architects throughout the Middle East and other hot dry areas. However, the thermal performance of such buildings under hot dry climatic conditions has rarely been quantitatively studied. In this paper, a detailed finite element model for the investigation of the thermal performance of non air-conditioned buildings with vaulted roofs (VR) is suggested based on two-dimensional unsteady heat transfer in such roofs and solar geometry. This model allows a comparison of the thermal performance of non air-conditioned buildings with a VR and a flat roof (FR) under different climatic conditions. Results obtained by numerical calculation show that, irrespective of building type the VRs are applied to, buildings with a VR have lower indoor temperatures as compared to those with a FR. The reason is that such roofs dissipate more heat than a FR does by convection and thermal radiation at night due to the enlarged curved surfaces. This implies that such roof forms are suitable for buildings located in hot dry regions but not for those located in hot humid areas, and reasonably explains why curved roofs have been extensively adopted by builders and architects in the hot dry areas in the past. However, with the decrease in the half rim angle of a VR, the difference of indoor thermal condition between a VR and a FR building becomes small and insignificant. Results also indicate that the indoor air temperature is slightly influenced by the half rim angle θ0 and the orientation φv of the VR. To be effective to create a favorable thermal condition inside buildings with a VR under hot dry climatic conditions, the half rim angle of a VR should be θ0>50°, instead of θ0<50∘, which is the optimal half rim angle of a VR of air-conditioned buildings, as found by the present authors in a previous study.

An Improved Approach to Automatic Recognition of Civil Infrastructure Objects

Civil infrastructure objects are important elements in GIS applications. Due to the wide variety of object types, automatic recognition of infrastructure objects from imagery has been a challenging issue for the last two decades. Different approaches have been developed for recognition of buildings, one kind of infrastructure object most frequently dealt with in GIS. by defining and employing individual criteria. A Hopfield neural network can effectively combine different criteria in an overall network structure for a global optimization in finding object. In this paper we develop a holistic feature extraction approach including edge extraction, noise edge elimination by Gabor filters, contour extraction based on morphological operations, polygon simplification by local Hough transform, and building roof candidate selection using central contour sequence moment. In addition, shadows associated with buildings are extracted. This improved feature extraction approach greatly enhances the quality of recognition of objects, such as peaked-roofed and flat-roofed buildings, by a Hopfield neural network that accommodates similarity measures using the extracted features in a structured way. The achieved results demonstrate a promising approach for building recognition and can be extended to other infrastructure objects.

Quasi-static wind load combinations for low- and middle-rise buildings

Fluctuating surface pressure measurements are made for four flat roofed building models with square or rectangular plans in order to examine wind load combinations. The fluctuating pressures are integrated over all their surfaces and results are obtained of along-wind force, across-wind force, vertical force, along-wind overturning moment, across-wind overturning moment and torsional moment on their frames. The maximum wind force component and other simultaneously observed wind force components are examined, and some interesting facts regarding the wind force combinations are discussed on the basis of absolute value correlations, phase-plane expressions and so on. The maximum normal stresses in the column members of simple frame models are then examined in order to directly check the wind load combination effects.

Monocular Right-Angle Building Hypothesis Generation in Regularized Urban Areas by Pose Clustering

By decomposing the building extraction problem into three sequential steps (selection, indexing and correspondence), the complexity of monocular extraction from aerial imagery can be reduced. This paper focuses on the first step, selection, during which an image subset likely to contain a single building is extracted. Pose clustering can be one way to achieve this. Based on vote accumulation, pose clustering offers the advantages of reduced complexity and a false alarm rate prediction capability. This paper describes a voting scheme for right-angle flat-roof buildings, from which image space building location hypotheses may be efficiently generated for regularized urban areas. The proposed scheme incorporates weights, constraints and uncertainties that should be implemented due to the nature of aerial imagery. Additionally, based on an occupancy model, a random vote accumulation and threshold analysis of the proposed voting scheme is presented. The main limitation of the proposed scheme is the need for a scaled building model prior to the hypothesis generation phase. Results from simulated and real imagery show that the building detection percentages as well as the quality percentage are well within range, even without a verification process.

Assesment of grid-connected photovoltaic systems in the Kuwaiti climate

Grid-connected photovoltaic (PV) systems is one of the most promising applications of PV systems. Till now, no detailed studies have been carried out to assess the potential of grid-connected systems in Kuwait. This work investigates the feasibility of implementing grid-connected PV systems in the Kuwaiti climate. The proposed system consists of crystalline solar modules mounted on the building roof and an inverter to convert PV dc output to ac voltage. The building receives electricity from both the PV array and the utility grid. In this system, the load is the total electrical energy consumption in the building. The objective of this work is to examine the performance as well as the economic feasibility of grid-connected PV systems in the Kuwaiti climate. A program is written to evaluate the performance as well as the economic feasibility of such systems in Kuwait. The input to the program is the weather data for Kuwait, time dependent building loads, as well as the utility rates for Kuwait. Weather data generator subroutine included in the trnsys program is used to generate hourly weather conditions from the monthly average values of daily radiation on horizontal surface, and ambient temperature available for Kuwait. The five-parameter PV model, which is applicable to both crystalline and amorphous PV modules, is used to determine the performance of the solar modules used in this study. The transient simulation program ( trnsys) is used to link the components of the grid-connected PV system together. The inverter efficiency is represented as a linear function of input power. In this case, it is assumed that the AC output from the system will never be greater than the building load. Electricity tariffs will have an important impact on the cost-effectiveness of the system studied. The tariff used for electric utility is a flat rate per unit kWh of electrical energy. Simulations of the proposed system were carried out over the academic year. The building examined in this study is a flat roof building with a single story. The building roof area is large enough so that the PV arrays can be spaced widely to minimize shading losses. Different array slopes, and azimuth angles were studied to maximize the annual energy generated by the PV modules. Finally, the economic feasibility of grid-connected PV systems in Kuwait are examined.

The influence of small open fields on wind loads on low buildings

Abstract In established residential areas it is not uncommon for existing schools and shopping plazas to be well shielded by trees and dwellings for most directions but to be open over a very limited fetch of a playground or a parking area. Few codes provide advice on the evaluation of loads in such circumstances; but to ignore the shielding would result in a significant overestimate of the wind loads for the design of extensions or modifications to bring existing structures up to present day standards. This study predicts the uplift loads on these types of structures through an analysis of a database of calculated reactions measured on several structures. The paper outlines the development of local exposure factors that, by accounting for effects of small open fields, can refine the prediction of uplift forces on flat roof buildings in suburban areas. A modification to the National Building Code of Canada model is used to apply these factors. A study of the flow over an array of elements was used to develop a method to apply the local exposure factors to a structural system.

Influence of building size on rooftop dispersion of exhaust gas

An exhaust gas dilution model that accounts for initial near-source dilution and the influence of turbulence scale and intensity at roof level is presented. The performance of the model is compared with tracer gas measurements of rooftop concentrations from vertically directed flush vents on 11 flat-roofed building configurations in an urban boundary layer simulated in a wind tunnel. A power-law approximation for dispersion in homogeneous turbulence predicts that distance-dependent dilution should be proportional to the product of the square root of building frontal area, and the source-to-receptor distance to the 1.5 power. Comparison with existing wind-tunnel data shows that this building size-dependent relation is a better estimate for dilution than the usual assumption of dilution proportional to the square of downwind distance, independent of building size. The data supports the use of a linearly additive initial plume radius to account for near-source dilution, and shows that this initial dilution affects total dilution far downwind.

From the Memory of History: The Painted Room at Bardia

Bardia has a natural deep-water harbour confined by cliffs, making it an ideal submarine haven. It held a strategic position in the last war in connection with the capture of Tobruk, and was used by both the Germans and British as a supply base (Fig. 1). Set back from the shoreline were numerous single-storey, flat-roofed buildings overlooking the harbour, one of which was a lookout post where the mural under discussion survives.On 30th December 1941 the Allies launched a decisive attack on Bardia (Liddell Hart 1953, 177–178), which surrendered on 2nd January 1942 (Murphy 1961, 511–512). On 27 th January Rommel had struck again at Benghazi; General Auchinleck gave orders to withdraw, and formed a front line near Gazala in early February.According to its contemporary War Diary, the 5th Battalion, East Yorkshire Regiment arrived in the Western Desert from Palestine and Syria on 20th February, and two days later took over from the 11th Indian Brigade approximately 20 miles south of Gazala (W.O.169/5076). One of the soldiers in this batallion was Private John Frederick Brill 4617871 of the Royal Army Service Corps, the artist of the mural in the Painted Room at Bardia.

Snow on two-level flat roofs — measured vs. 1990 NBC loads

Between 1967 and 1982, depths and specific gravities of snow were recorded on 44 single- and multi-level flat-roofed buildings between Halifax and Edmonton. The average density of snow in the drifts where the roofs change elevation was about 3.0 kN/m3, the value used consequently in the 1990 National Building Code of Canada (NBC). This is some 25% higher than the value used in the 1985 NBC. Data on drift geometry and maximum loads in the drifts are presented and compared with provisions in the 1990 NBC. As well, the paper presents measured values of average and maximum roof-to-ground load ratios for upper level roofs and for lower roofs away from the drifts. These compare favourably with those recommended in the 1985 and 1990 NBC. The statistical variabilities of snow loads and densities are given, since these are required to establish load factors used for limit states design in the NBC. Further research needs are identified. Key words: snow loads, snow drifts, uniform snow, flat roofs, snow density, snow load variability, snow load survey.

Prediction of diffracted field strength in the shadow of a flat roofed building

A modification to previously developed slab diffraction models allows Babinet's principle to be applied to the problem resulting in simpler computation. An extension to the new model allows the case where a flat roof is surrounded by a parapet wall to be considered. Results show that in such cases the diffracted field strength can exceed that for a perfectly absorbing building. Predictions are supported by measurements made using real buildings and scale models.