Hypothetical Building Research Articles

Urban microclimate analysis with consideration of local ambient temperature, external heat gain, urban ventilation, and outdoor thermal comfort in the tropics

In year 2003, United Nations estimated that by year 2030, up to 5 billion people will live in urban areas which will be 61% of the world's population. Urbanization brings major modification on natural landscape; buildings are erected, soil has been transformed into roads and pavement, greenery has been vastly reduced, etc. The deterioration of the urban environment through urbanization can be seen from a phenomenon known as urban heat island (UHI); where cities record higher temperatures in comparison to their non-urbanized surroundings.This study explores the effect of urban texture, characterized by its physical density and form, on the receivable external heat gain, ambient temperature, urban ventilation and outdoor thermal comfort. Addressing these aspects would provide a more comprehensive methodology on urban microclimate analysis, rather being conducted separately. Hence, analyzing building performance should be looking not only at a stand-alone (isolated) setting, but also to consider the ‘neighborhood’ approach, where urban environment has a significant effect on the energy performance of individual buildings.A series of hypothetical building arrangements are being put into an empty block in a dense urban area, where each of scenarios goes through a series of microclimatic analyses. At the end, this parametric study would narrow down design options which have favorable microclimate condition and acceptable district energy performance.

Life cycle energy balance of residential buildings: A case study on hypothetical building models in Finland

This study has demonstrated the life cycle primary energy balance of the four residential building types (detached house, row house, townhouse and apartment block) based on current Finnish design. The differences in the energy balance arising from the geometrical characteristics of each housing type were investigated using hypothetical building models. In addition, the influence of structural frame material selection was observed in relation to the housing types. The results showed that there are clear differences between the housing types: the detached house is the highest energy consumer, the row house the second (about 20% less), the townhouse the third (about 30% less) and the apartment block the lowest (about 45% less), regardless of the frame materials selection. The differences appeared evenly among the building life cycle stages. A correlation has been observed between the geometrical factors and life cycle primary energy balance of the reference buildings.

The effect of material selection on life cycle energy balance: A case study on a hypothetical building model in Finland

A building is a complex system consisting of many different materials. The material selection, therefore, has a significant role in sustainable building design. This study has demonstrated the influence of material selection on the life cycle energy balance of a building based on current building codes and common building service systems in Finland. The influences of the selection were investigated on a relative basis using a hypothetical building model and in the three building component categories (structural frame, surface components and inner components).The results showed that, in general, the differences between the alternative materials are rather visible in the production stage of the building and the energy benefit from material recycling. But it was also revealed that the influences of the selection appear differently in each life cycle stage of the building depending on the building component categories. The selection of the structural materials has larger effect than the other two component categories and a combination of different structural frame materials seems to be effective in some cases. The material selection for sheathing, exterior cladding and thermal insulation has a relatively greater influence than the others in the surface and inner components categories. The energy recovery benefits of wood and plastic products have a great influence on the life cycle energy balance of the building.

Effect of Material Used in Concrete Mixture on the Foundation Stresses on Soil

Sustainable design, green architecture and sustainable construction are new methods for design and construction that are employed for environmental and economic challenges. Clay and bricks proved as sustainable building materials. In this paper, crush brick in the concrete mixture instead of normal coarse aggregate will be used. STAAD Prov8i software was applied for the designed of a hypothetical building in different sites of the three locations in Iraq (Mosul at the north, Baghdad at the center and Basrah at the south). The input model data used in the software were depending on the field and laboratory tests done for twenty three sites in the three locations of Iraq. Concrete properties values were used in the software for concrete mixture with crushed bricks. The results values of base pressure obtained from the software were low for the three locations. The maximum values of base pressure under the foundation for both the average and the minimum bearing capacity values for Mosul region for the normal strength concrete and air-entrained were (94, 84) kPa and (91, 82) kPa respectively, for Baghdad region were (89, 82) kPa and (86, 81) kPa respectively. Finally, for Basrah, the results for the base pressure were (84, 77) kPa and (82, 76) kPa, respectively. The results values of the base pressure were less for all locations compared with the base pressure values obtained from a previous work for the same locations. The use of crushed brick as aggregate in the concrete mixture is economical due to its availability as local material and it is durable materials with low weight.

A Parametric Study of Wind Catcher Model in a Typical System of Evaporative Cooling Tower Using CFD

The aims of the research work described in this paper is a part were to use computational fluid dynamics (CFD) to investigate the factors affecting the performance of a single-stage downdraught evaporative cooling device for low-energy cooling of buildings developed from a novel prototype device described by Pearlmutter et al. (1996; 2008); and to model and explore the performance of the device when integrated within a hypothetical building. This involved carrying out simulations: to select the most effective wind catcher geometry. Two types of wind catcher using curved deflector and closed cowl design were studied: In total five alternative arrangements were investigated. Arrangements 1 and 2 were bi-directional wind catchers. Arrangement 1 was modelled without a baffle and arrangement 2 was modelled with an extended baffle. Arrangements 3, 4 and 5 were uni-directional closed cowls. Arrangement 3 was modelled without a baffle, arrangement 4 was modelled with a short baffle and arrangement 5 was modelled with an extended baffle and an increased inner radius of 1 metre which had the effect of raising the mid-plane height of the cowl inlet by 1 metre. Initially, for comparison in all studies, the inlet wind speed was set at 10 m/s at a reference height of 11.5 metres which corresponded to the mid plane height of the wind catcher and wind cowl entry ducts for arrangements 1 to 4. The CFD simulations were carried out to define the optimum geometry of a wind catcher.

Influence of wind directionality on wind loads and responses

Different methods of allowing for wind directionality are discussed and their effects on predicted structural wind loads and responses of buildings and cladding pressures are examined. Results are presented for several tall buildings, for which wind tunnel model tests have been made, as well as for hypothetical buildings with generic aerodynamic signatures. Predictions of extreme wind loads and responses are made in both extra-tropical and tropical wind climates. Three of the analysis methods, namely the worst-case approach, the sector-by-sector method, and the up-crossings method are probabilistic procedures which rely on historical wind records. Also discussed is a time-domain analysis which tracks wind loads and responses during the passage of particular storms. This requires time histories of wind speed and direction that at this time are only available for tropical storms, where Monte Carlo simulations are used to determine time histories of the wind field. Directional factors are extracted from all predictions made in this study. These factors provide direct comparisons of extremes wind loads and effects predicted with particular methods of analysis to the corresponding predictions made with the worst-case method, which does not recognize the azimuthal variation of the aerodynamic data or the directional preferences of severe winds.

An illustration of the optimization of combined cooling heating and power systems using genetic algorithm

The performances of combined cooling, heating and power (CCHP) system are greatly dependent on its design, operation strategy and thermal and electric demands. This paper illustrates how the use of a genetic algorithm can provide speedy optimization, by applying it to two styles of buildings operated in different operation strategies. The primary energy consumptions of CCHP system following electric demand management (EDM) and thermal demand management (TDM) are firstly analyzed respectively. Then, sixteen hypothetical buildings are constructed to represent various energy demands. Primary energy saving (PES), annual total cost saving (ATCS), and CO2 emission reduction (CO2ER), are weighted to evaluate the integrated performances of CCHP system in comparison to separation production system. Finally, the optimized CCHP system for sixteen scenarios using GA are compared. Practical application: This paper provides an optimization design method for CCHP system. The performance analysis of CCHP systems running different operation modes for different buildings is believed by the authors to contribute to a significant guide for the fundamental design of CCHP systems. Although sensitivity to a number of other important design considerations such equipment performance, possible future changes in operating conditions, changes to the price or carbon intensity of grid-supplied energy etc are not addressed, the conclusions present a simple and effective direction and the proposed optimization algorithm and the evaluation method for CCHP system can be extended to other buildings.

Web-based construction waste estimation system for building construction projects

This paper proposes a web-based construction waste estimation system (WCWES) for building construction projects incorporating the concepts of work breakdown structure, material quantity takeoff, material classification, material conversion ratios, material wastage levels, and the mass balance principle. The WCWES integrates online data input modules and online analytical modules for the quantification of different kinds of waste generated in the construction process at the project level. It facilitates accessibility, interfacing, connectivity and information sharing of users in carrying out a wide range of construction waste estimation tasks for sustainable construction waste management. A hypothetical building construction project is used to demonstrate the application and usefulness of the WCWES. • Developing a web-based building construction waste estimation system • Allowing online analytical processing of construction waste • Improving the estimation accuracy of construction waste • Allowing multi-dimensional analysis of construction waste

Analysis and Assessments of Combined Cooling, Heating and Power Systems in Various Operation Modes for a Building in China, Dalian

Combined Cooling, Heating and Power (CCHP) systems have been widely used in different kinds of buildings to make better use of fuels because of their high overall efficiency. This paper presents a mathematical analysis of a CCHP system in comparison to a Heating, Ventilation and Air Conditioning (HVAC) system. The operation strategies following electric load (FEL), thermal load (FTL) and a hybrid electric-thermal load (FHL) are proposed and investigated in this study. Criteria, namely primary energy saving (PES), exergy efficiency (ηexergy), and CO2 emission reduction (CER) are defined to evaluate the performances of CCHP systems for a hypothetical building located in Dalian (China). The results indicate that: (1) a new mathematical foundation is established to find whether the recovered thermal energy and the amount of electricity generated by the power generation unit (PGU) are enough to provide the energy required; (2) the CCHP system does not always perform better than a HVAC system from an instantaneous perspective, especially in FTL mode; (3) the CCHP system in FEL operation mode can be seen as a suitable energy system in Dalian from the annual performance perspective. Furthermore, a sensitivity analysis is presented in order to show how the performances vary due to the changes of various technical variables.

Simulation of Reinforced Concrete Frames with Nonductile Beam-Column Joints

The accurate prediction of shear strength and flexibility of beam-column joints without transverse reinforcement is essential to assess the seismic performance of nonductile reinforced concrete (RC) buildings characterized by having such unreinforced beam-column joints. In this study, a multilinear backbone curve to represent the moment-rotation relationship of an unreinforced corner beam-column joint is proposed. The modeling parameters of the backbone curve are estimated based on experimental results of four corner joint specimens recently tested by the authors. Furthermore, the proposed backbone curve is modified to be applicable to interior and roof beam-column joints. These backbone curves are validated by accurate reproduction of the force-drift responses of the four corner joint specimens and eight other exterior and interior joint specimens from literature. Using these backbone curves, nonlinear dynamic analyses are performed on three hypothetical building frames. The analytical results demonstrate the importance of joint flexibility for seismic assessment of nonductile RC buildings.

Variability of building environmental assessment tools on evaluating carbon emissions

With an increasing importance of sustainability in construction, more and more clients and designers employ building environmental assessment (BEA) tools to evaluate the environmental friendliness of their building facilities, and one important aspect of evaluation in the BEA models is the assessment of carbon emissions. However, in the absence of any agreed framework for carbon auditing and benchmarking, the results generated by the BEA tools might vary significantly which could lead to confusion or misinterpretation on the carbon performance of a building. This study thus aims to unveil the properties of and the standard imposed by the current BEA models on evaluating the life cycle carbon emissions. The analyses cover the (i) weighting of energy efficiency and emission levels among various environmental performance indicators; (ii) building life cycle stages in which carbon is taken into consideration; (iii) objectiveness of assessment; (iv) baseline set for carbon assessment; (v) mechanism for benchmarking the emission level; and (v) limitations of the carbon assessment approaches. Results indicate that the current BEA schemes focus primarily on operational carbon instead of the emissions generated throughout the entire building life cycle. Besides, the baseline and benchmark for carbon evaluation vary significantly among the BEA tools based on the analytical results of a hypothetical building. The findings point to the needs for a more transparent framework for carbon auditing and benchmarking in BEA modeling.

Empirical Research Design on the Influencing Factors of Supply Chain Performance and their Relationships

Supply chain has become a leading role in this severely competitive market, while the research on supply chain performance has not been paid enough attention to improve overall operational abilities and effectiveness. Based on the view of an integrated supply chain, we develop a theoretical model of factors affecting supply chain performance from the points of material flow, commercial flow and information flow. It also describes the main procedure to finish this empirical research on this subject and explores hypothetical model building and measurement development. In this way, we pave the way for doing further empirical research on this subject.

Influence of spatial correlation of strong ground motion on uncertainty in earthquake loss estimation

AbstractIn addition to the mean values of possible loss during an earthquake, parameters of the probability distribution function for the loss to a portfolio (e.g. fractiles and standard deviation) are very important. Recent studies have shown that the proper treatment of ground‐motion variability and, particularly, the correlation of ground motion are essential for the estimation of the seismic hazard, damage and loss for distributed portfolios. In this study, we compared the effects of variations in the between‐earthquake correlation and in the site‐to‐site correlation on seismic loss and damage estimations for the extended objects (hypothetical portfolio) and critical elements (e.g. bridges) of a network. A scenario earthquake approach and a portfolio containing a set of hypothetical building and bridges were used for the purpose. We showed that the relative influences of the types of correlation on characteristics of loss distribution and the probability of damage are not equal. In some cases, when the median values of loss distribution or the probability that at least one critical element of a lifeline will be damaged are considered and when the spatial correlation of ground motion is used, the possible variations in the between‐earthquake correlation may be neglected. The shape of the site‐to‐site correlation function (i.e. the rate of decrease of the coefficient of spatial correlation with separation distance) seems also to be important when modelling spatially correlated ground‐motion fields. Copyright © 2010 John Wiley & Sons, Ltd.

Methodology to estimate building energy consumption using EnergyPlus Benchmark Models

The evaluation of building energy consumption usually requires building energy profiles on an hourly basis. Computer simulations can be used to obtain this information but generating simulations requires a significant amount of experience, time, and effort to enter detailed building parameters. This paper presents a simple methodology to estimate hourly electrical and fuel energy consumption of a building by applying a series of predetermined coefficients to the monthly energy consumption data from electrical and fuel utility bills. The advantage of having predetermined coefficients is that it relieves the user from the burden of performing a detailed dynamic simulation of the building. The coefficients provided to the user are obtained by running EnergyPlus Benchmark Models simulations; thus, the simulation process is transparent to the user. The methodology has been applied to a hypothetical building placed both in Atlanta, GA, and in Meridian, MS, and in both cases, errors obtained for the estimated hourly energy consumption are mainly within 10%.

Recycling lead-based paint contaminated deconstructed masonry materials as aggregate for Portland cement concrete—A cost effective and environmental friendly approach

Four lead-based paint (LBP) contaminated deconstructed masonry materials (two types of concrete blocks and two types of clay bricks) were crushed and used to replace all natural aggregate in conventional concrete. To reduce cost, the crushed materials were neither sieved nor re-graded. After their physical properties and lead-leaching ability were characterized, these masonry materials were used for concrete with various mix proportions. The workability, lead-leaching ability and compressive strength of the concrete were studied. A cost-savings analysis was conducted to compare such a masonry deconstruction method with tradition ones (including LBP removal, hazardous and non-hazardous material disposal) for three hypothetical buildings. The results indicated that after being used as aggregate in Portland cement concrete, the lead is sequestered, or rendered non-leachable, due to the high alkalinity of Portland cement, and the concrete no longer has the toxicity characteristic for lead. Well-designed and well-manufactured concrete made with all LBP-contaminated, recycled aggregates can have satisfactory workability and strength for a variety of constructions, including roadways, parking lots and foundations. The savings from eliminating LBP removal and waste material disposal as well as minimizing the use of secure landfills range from approximately $4.63 to $412.80/m 2, depending on the size of the deconstruction project and the applicable environmental protection regulations. Recycling such masonry materials as concrete aggregate is a cost effective and environmentally friendly approach.

Funciones de vulnerabilidad calculadas para edificaciones en muros de hormigón reforzado

En este documento se presenta una metodologia que valora el nivel de dano que pueden alcanzar las edificaciones correspondientes al sistema estructural de muros de hormigon reforzado. El modelo estima un indice de vulnerabilidad calculado en funcion de las caracteristicas de la estructura que mas influyen en su comportamiento sismico, y lo relaciona con un indice de dano, que a su vez depende de la accion del movimiento sismico. El modelo estima diferentes grados de vulnerabilidad, y por consiguiente, define distintos niveles de dano ante una misma accion. La relacion de la vulnerabilidad con el dano se materializa mediante una forma continua con las funciones de vulnerabilidad. El modelo se construyo sobre una muestra de edificaciones reales e hipoteticas las cuales representan las caracteristicas mas relevantes de las edificaciones de este tipo en el medio colombiano. Rev. ing. constr. [online]. 2010, vol.25, n.1, pp. 63-82. ISSN 0718-5073. http://dx.doi.org/10.4067/S0718-50732010000100003

Multi-criteria analysis of combined cooling, heating and power systems in different climate zones in China

The design and operation of combined cooling, heating and power (CCHP) systems are greatly dependent upon the seasonal atmospheric conditions, which determine thermal and power demands of buildings. This paper presents a mathematical analysis of CCHP system in comparison to separate system. The corresponding primary energy consumption in thermal demand management (TDM) and electrical demand management (EDM) operation modes are deduced. Three relative criteria, primary energy saving (PES), CO 2 emission reduction (CO 2ER), and annual total cost saving (ATCS) are employed to evaluate the respective performances of CCHP systems for a hypothetical building in five different climate zones from the technical, environmental and economic aspects. The results indicate that CCHP system in TDM mode in the cold area, where the building requires more heating during the year, achieves more benefit over separate system while CCHP system in EDM mode suits the building having stable thermal demand in mild climate zone.

Risk-based decision support for seismic rehabilitation of structures

This study presents a risk-based decision support framework for seismic retrofit of building structures where the decision criterion is to minimize the sum of the cost required for the rehabilitation and the expected seismic loss over a specified time period. Probabilistic seismic hazard model (PSHM) and probabilistic seismic demand model (PSDM) are utilized for manipulation of the uncertainty propagation from the seismic hazard to the structural damage. A mathematical formula is then developed for probabilistic estimation of the seismic damage and losses over a specified time period. The analysis procedure is developed such that the effect of the different configurations of the decision inputs can be promptly observed. The proposed procedure is demonstrated by performing a decision analysis for a hypothetical RC building structure for determination of the optimal level of seismic rehabilitation using steel bracings.

Use of Dissimilar Walling Systems on Residential Building Envelopes for Improving Their Thermal Performance

This paper summarises the results of a combined numerical, statistical and experimental study concerned with the use of dissimilar walling systems on the external parts of a given building envelope. The rational behind this “hybrid wall” concept, as opposed to conventional approaches where identical walls are used in a building envelope, is to achieve a more effective distribution of thermal mass across the envelope and, hence, improve the overall thermal performance of the building. The effectiveness of the “hybrid wall” concept was investigated using a series of hypothetical building modules of common Australian residential constructions, namely Light Weight (LW), Brick Veneer (BV), Reverse Brick Veneer (RBV) and Cavity Brick (CB). These designs were examined numerically using a commercial energy rating tool known as “AccuRate”, statistically using JMP software and experimentally using a novel bench-scale setup developed as part of this study. The performance of each design was evaluated by its energy consumption. The numerical predictions and experimental data highlighted that the east and west walls have the most impact on the energy consumption under Australian climatic conditions. It was found that considerable reductions in the energy consumption could be achieved in cases where the hybrid wall concept was implemented through the use of high thermal mass insulated walls on the east and west sides of the building envelope.

Estimation of Seismic Loss for Spatially Distributed Buildings

A simulation-based framework for assessing seismic risk of spatially distributed buildings is developed by taking the spatial correlation of seismic excitations into account. For each of seismic events compiled in a synthetic earthquake catalog, inelastic seismic demand on buildings that are approximated by bilinear single-degree-of-freedom systems is compared with uncertain structural capacity to evaluate seismic damage severity. The proposed framework is employed to investigate the sensitivity of the estimated seismic risk of sets of buildings to the degree of spatially correlated and simultaneously occurring seismic excitations. In particular, four correlation levels—no correlation, full correlation, and partial correlation with/without intra-event components—are considered. The assignment of the partial correlation is based on a recently developed spatial correlation model, and the sets of hypothetical buildings mimic existing building stocks in downtown Vancouver. The analysis results highlight that underestimation or overestimation of correlation of seismic demand could lead to very different probabilistic characteristics of aggregate seismic loss although its mean is unaltered. The sensitivity analysis results suggest that uncertainty in structural capacities as well as average local soil conditions is of relative importance.