This paper presents a simplified method of evaluating the seismic performance of buildings. The proposed method is based on the transformation of a multiple degree of freedom (MDOF) system to an equivalent single degr...This paper presents a simplified method of evaluating the seismic performance of buildings. The proposed method is based on the transformation of a multiple degree of freedom (MDOF) system to an equivalent single degree of freedom (SDOF) system using a simple and intuitive process. The proposed method is intended for evaluating the seismic performance of the buildings at the intermediate stages in design, while a rigorous method would be applied to the final design. The performance of the method is evaluated using a series of buildings which are assumed to be located in Victoria in western Canada, and designed based on the upcoming version of the National Building Code of Canada which is due to be published in 2005. To resist lateral loads, some of these buildings contain reinforced concrete moment resisting frames, while others contain reinforced concrete shear walls. Each building model has been subjected to a set of site-specific seismic spectrum compatible ground motion records, and the response has been determined using the proposed method and the general method for MDOF systems. The results from the study indicate that the proposed method can serve as a useful tool for evaluation of seismic performance of buildings, and carrying out performance based design.展开更多
The design code for each country is revised and updated based on an expected zone’s seismic intensities,geotechnical site classifications,structural systems,construction materials and methods of construction in order...The design code for each country is revised and updated based on an expected zone’s seismic intensities,geotechnical site classifications,structural systems,construction materials and methods of construction in order to provide more realistic considerations of seismic demand,seismic response,and seismic capacity.Based on the aforementioned provisions,structures designed according to different seismic codes may yield different performances for the same level of hazard.This study aims to investigate and compare the induced responses related to the earthquake-resistant design of reinforced concrete(RC)buildings according to the Saudi building code(SBC-301),American code(ASCE-7),uniform building code(UBC-97),and European code(EC-8).In order to account for the provision regarding the hazard specification and its effect on the induced seismic responses,four regions in the Kingdom of Saudi Arabia with different seismic levels are selected.The code provisions related to the specification of site classification and its effect on the induced design base shear are investigated as well.Significant differences are observed in the induced responses with the variation in seismic design codes for the considered seismic hazards and site classifications.展开更多
Amidst the recent development in the usage of curtain walls for office buildings, high utilization of energy and poor thermal comfort issues have become paramount. This paper assesses thermal comfort in multi storey (...Amidst the recent development in the usage of curtain walls for office buildings, high utilization of energy and poor thermal comfort issues have become paramount. This paper assesses thermal comfort in multi storey (naturally and mechanically ventilated) office buildings in Accra, the Capital city of Ghana using Fanger’s Predicted Mean Votes (PMV) and Predicted Percentage of Dissatisfied persons (PPD) model. The model relates to the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 55 (which gives an acceptable temperature range of 23℃ - 26℃) and the International Standards Organization (ISO) 7730. Indoor environmental parameters (temperature and relative humidity) of 4 multi storey office buildings were recorded over a 10 month period. The environmental parameters were analyzed using PMVcalc_v2 software which resulted in the generation of PMV-PPD values. The findings reveal high PMV-PPD values in the Naturally Ventilated Building (NVB) whiles the Mechanically Ventilated Buildings (MVB) fall within the comfort zone. Meanwhile, the Actual Mean Votes (AMV) by the occupants suggest all four buildings are relatively comfortable with the mechanically ventilated offices being more comfortable. Additionally, it is recommended that buildings are orientated with their longer sides facing north-south, with enough shading in order to improve the thermal comfort conditions of work spaces.展开更多
Building defect is an issue in existing buildings that needs urgent tackling to prevent further problems. This study assessed the defects in concrete elements in residential buildings of 30 years and above in the Onit...Building defect is an issue in existing buildings that needs urgent tackling to prevent further problems. This study assessed the defects in concrete elements in residential buildings of 30 years and above in the Onitsha metropolis of Anambra State, Nigeria. Data collection instruments in the study include structured questionnaire, interviews, visual inspection/observations, archival records, recordings, photographs;and non-destructive testing of the concrete elements in an existing building in the study area. The population of this study constituted of the construction registered professionals and the existing buildings in study area. The sample for the study was based on the calculated sample size using Taro Yamani Formula. A total of 158 registered professionals were sampled from the population of 260. The questionnaires were purposively distributed to the registered professionals up to the required sample sizes of 158 and 129 questionnaires were properly filled and returned. The study used the SPSS and Microsoft Excel to analyze the data. The results were analyzed in percentages and figures using descriptive statistics and presented in the form of pie charts and tables. The finding of the study revealed that the causes and effects of structural defects on the concrete elements in existing buildings in the study area according to the rating are;exposed/corrosion of the embedded metals, faulty workmanship, overload and impacts, chemical attack, freeze-thaw deterioration, fire/heat, restraint to volume change. The visual observation revealed that the structural elements are characterized by heavy defects such as deep vertical, horizontal and diagonal cracks, exposed/ corrosion of the embedded metals, spalling of the concrete slabs. The existence of defects in the concrete members led to the low compressive strength of the concrete elements and the structural instability of the existing buildings as revealed by the non-destructive test. The non-destructive test result revealed that most of the tested concrete elements have low compressive strength value and such were remarked poor as they did not satisfy the assumed value. Essentially, the study concluded by recommending that regular monitoring, inspections and non-destructive testing of concrete elements should be conducted on existing aged and defected buildings to detect the structural stability of the buildings;and it is imperative to evacuate occupants from heavy structurally deteriorated and defected buildings since most of them have lost their residual design life span and ability to sustain imposed loads.展开更多
The proliferation of multi-family residential building in Anambra State of Nigeria due to increasing demand without recourse to performance has broughtconcerns about the adequacy and sustainability of this housing typ...The proliferation of multi-family residential building in Anambra State of Nigeria due to increasing demand without recourse to performance has broughtconcerns about the adequacy and sustainability of this housing type.This study therefore,assessed the adequacy and sustainability performance of multi-family residential buildings in urban areas of Anambra State.The study sampled the opinions of 384 households living in multi-family residential buildings through a questionnaire survey.We conducted data analysis based on 214 responses that were useful for analysis.The study found that internal and building component variables and supporting neigh-borhood variables were adequate,but the surrounding environment variables were inadequate based on Mean Score Index.However,based on Sustainability Performance Index,the occupant sperceived social sustainability performance of the buildings as satisfactory,while environmental and economic sustainability performance were perceived as fairly satisfactory.The Pearson correlation coefficient result further established that adequacy of internal and building component variables was significantly and positively related to the residents'perceived social sustainability performance.Adequacy of the surrounding environmental variables was also found to be positively and significantly related to the residents'perceived environmental sustainability performance,whereas adequacy of supporting neighborhood facilities was found to be negatively and significantly related to the residents’perceived economic sustainability performance.This sug-gested that investors and owners of multi-family residential buildings should direct more efforts towards improving the surrounding environment to supplements other facilities and increase the economic benefit of the renters or occupiers with increasing economic sustainability performance in terms of value for money.展开更多
Energy consumed by buildings accounts for approximately one-third of the total energy consumption of the society.Moreover,energy systems employed in buildings emit hazardous pollutants,such as,NOx,PM2.5 and CO2,into t...Energy consumed by buildings accounts for approximately one-third of the total energy consumption of the society.Moreover,energy systems employed in buildings emit hazardous pollutants,such as,NOx,PM2.5 and CO2,into the environment.Consequently,increasing the energy efficiency of buildings constitutes an important problem concerning the field of building-energy and environment conservation.Thermal resistance and capacitance are two important thermophysical properties of building walls significantly impacting their heat-transfer performance.Traditional theories concerning these properties,however,face certain limitations:(1)the concept of thermal resistance is only valid for one-dimensional,steady heat conduction without existence of an internal heat source;(2)thermal resistance and capacitance are relevant,and can,therefore,not be used to analyze heat-transfer and storage performance,respectively,of building walls.Based on the entransy-dissipation-based impedance theory,a new approach towards realization of heat-transfer analysis and optimization has been proposed in this study.The weightiness of thermal resistance and capacitance with regard to heat-transfer performance has been described along with deduction of the corresponding substitutional relation via illustrative examples.The proposed approach has been demonstrated to effectively overcome aforementioned limitations of building energy conservation problems.展开更多
The local design and construction practices in the United Arab Emirates （UAE）, together with Dubai＇s unique rate of development, warrant special attention to the selection of Lateral Force-Resisting Systems （LFRS...The local design and construction practices in the United Arab Emirates （UAE）, together with Dubai＇s unique rate of development, warrant special attention to the selection of Lateral Force-Resisting Systems （LFRS）. This research proposes four different feasible solutions for the selection of the LFRS for tall buildings and quantifies the impact of these selections on seismic performance and cost. The systems considered are： Steel Special Moment-Resisting Frame （SMRF）, Concrete SMRF, Steel Dual System （SMRF with Special Steel Plates Shear Wall, SPSW）, and Concrete Dual System （SMRF with Special Concrete Shear Wall, SCSW）. The LFRS selection is driven by seismic setup as well as the adopted design and construction practices in Dubai. It is found that the concrete design alternatives are consistently less expensive than their steel counterparts. The steel dual system is expected to have the least damage based on its relatively lesser interstory drifts. However, this preferred performance comes at a higher initial construction cost. Conversely, the steel SMRF system is expected to have the most damage and associated repair cost due to its excessive flexibility. The two concrete alternatives are expected to have relatively moderate damage and repair costs in addition to their lesser initial construction cost.展开更多
Reversible protonic ceramic cells(RePCCs)hold promise for efficient energy storage,but their practicality is hindered by a lack of high-performance air electrode materials.Ruddlesden-Popper perovskite Sr_(3)Fe_(2)O_(7...Reversible protonic ceramic cells(RePCCs)hold promise for efficient energy storage,but their practicality is hindered by a lack of high-performance air electrode materials.Ruddlesden-Popper perovskite Sr_(3)Fe_(2)O_(7−δ)(SF)exhibits superior proton uptake and rapid ionic conduction,boosting activity.However,excessive proton uptake during RePCC operation degrades SF’s crystal structure,impacting durability.This study introduces a novel A/B-sites co-substitution strategy for modifying air electrodes,incorporating Sr-deficiency and Nb-substitution to create Sr_(2.8)Fe_(1.8)Nb_(0.2)O_(7−δ)(D-SFN).Nb stabilizes SF’s crystal,curbing excessive phase formation,and Sr-deficiency boosts oxygen vacancy concentration,optimizing oxygen transport.The D-SFN electrode demonstrates outstanding activity and durability,achieving a peak power density of 596 mW cm^(−2)in fuel cell mode and a current density of−1.19 A cm^(−2)in electrolysis mode at 1.3 V,650℃,with excellent cycling durability.This approach holds the potential for advancing robust and efficient air electrodes in RePCCs for renewable energy storage.展开更多
The cooling and heating load distribution of large area air-conditioned room such as “open” offices, shopping malls and waiting rooms is usually assumed to be even in air conditioning system design. However, it is n...The cooling and heating load distribution of large area air-conditioned room such as “open” offices, shopping malls and waiting rooms is usually assumed to be even in air conditioning system design. However, it is not the case in reality, and a low efficient air conditioning system results from this assumption. A simulation and analysis of the cooling load distribution of an office building in Hong Kong with TRANSYS software is provided in this paper. A typical office is divided into 13 zones for simulation, including external zone, medial zone and internal zone in the north, the south, the east and the west respectively and a central zone, instead of 4 directional zone. The result shows there is much cooling load difference between each zone, and more attention should be paid to uneven indoor cooling and heating load distribution to further guide the design.展开更多
The act of unauthorized siting of buildings has persisted in most developing countries. Despite numerous efforts at local levels to address this problem, its existence and effects keep on rising in various metropolise...The act of unauthorized siting of buildings has persisted in most developing countries. Despite numerous efforts at local levels to address this problem, its existence and effects keep on rising in various metropolises in Ghana. This research explores the causes of unauthorized siting of buildings in Asakae, a suburb of the Sekondi-Takoradi Metropolis, and suggests measures to curb them. In view of this, a sample size of 182 house-owners was chosen for the study. Accordingly, the sample size was determined using Fisher et al. formula and questionnaire survey approach was adopted for the study. More so, data generated from the survey were further analyzed, using Relative Importance Index. The findings of the survey indicated that ignorance on planning and building regulations, inadequate housing schemes, unrealistic zonings and the location of land are critical variables which influence unauthorized siting of buildings. It is recommended that the populace should be given regular public education on land-use planning and the building regulations of Ghana. More so, the Assemblies should automate their systems, with respect to monitoring and detection of buildings under construction;so that buildings that were being located at unapproved places could be quickly detected, and appropriate measures could be taken before their completion.展开更多
Degradation of timbers in building due to microorganisms was reported to cause enormous economic loses and species of Aspergillus are among the major cause of degradation of timbers in Nigeria. This research aims at e...Degradation of timbers in building due to microorganisms was reported to cause enormous economic loses and species of Aspergillus are among the major cause of degradation of timbers in Nigeria. This research aims at evaluating the cost of implications of biodegradations of Khaya grandifoliola by Aspergiilus spp in residential buildings empirically. Decayed Khaya grandifoliola samples were collected on residential buildings to extract, cultivate and identify the Aspergillus spp present. The cultivation went through serial dilutions and inoculations on sabouraud dextrose agar in petri dishes before incubation for 72 hours at 30 ~C. The species were identified through visual and microscopic observations. Percentage rate of degradation was determined under laboratory conditions by inoculating known weights of Khaya grandifoliola with the Aspergillus and incubating in a minimal medium for 24 weeks at 30 ~C. Weight loses and spore counts were recorded at four weeks intervals. A pattern of the degradation was forecasted. Accumulative weight loss of 16% for this period was obtained. Methods and costs of repair and replacement of decayed portions were evaluated. Residential Buildings constructed of Khaya grandifoliola experienced low cost of maintenance in this region but may not be in wetter regions where the conditions could be more favorable.展开更多
Moulds have been reported to destroy volumes of timbers in buildings annually. As a result, timber components within the built environment decline and fail to fulfill their basic requirements. This research focused on...Moulds have been reported to destroy volumes of timbers in buildings annually. As a result, timber components within the built environment decline and fail to fulfill their basic requirements. This research focused on the isolation and evaluation of the prevalence and effects of deteriorating moulds in the rain forest and swampy rain forest regions of Nigeria where the water activity is as high as 0.7. To accomplish this, decayed timber samples were aseptically collected on buildings from six strategic locations. The samples were serially diluted and inoculated onto Sabouraud Dextrose Agar medium in Petal dishes. The Petri dishes were incubated for 72 h at 30 ~C. Thereafter, moulds were isolated through visual and microscopic observations. The commonly encountered moulds were evaluated and analyzed. It was observed that, prevalence of moulds on buildings used for non residential purpose were higher. There was no significant difference between the prevalence on the components located inside the building and those outside the building. Ceiba pentandra exhibited highest degradation while Masonia altissima resisted most. The most deteriorating moulds were Aspergillus, Mucor, Rhizopus and Gliocladium. The deteriorations of Ceiba pentandra, Afzelia africana, Lophira alata, Anogessus leocarpus and Gossweilerodendron balsamiferum timbers under Aspergillus attack were projected.展开更多
Concrete is multicomponent composite material, consisting of coarse aggregate, fine aggregate, cement and water. Natural aggregates, as well as aggregates obtained after the reprocessing of buildings＇ demolition wast...Concrete is multicomponent composite material, consisting of coarse aggregate, fine aggregate, cement and water. Natural aggregates, as well as aggregates obtained after the reprocessing of buildings＇ demolition waste, can be used as coarse and fine aggregates. Characteristics of the hardened concrete depend on the raw materials, used for the preparation of concrete mixture, and their characteristics. The objective of the research is to analyse the sources of demolition waste, to describe the reprocessing technology of concrete waste, to investigate the production of the aggregate from the concrete waste, to analyse the main properties of these aggregates -- particles＇ density, bulk density, granulometric composition, hollowness and other properties, as well as to compare the obtained results with the requirements applicable to the aggregates based on natural materials.展开更多
Although disasters can occur anywhere, certain types of disasters are more likely to have more effects on some buildings than others, especially on those in urban areas. Buildings in Lagos have had nasty experiences f...Although disasters can occur anywhere, certain types of disasters are more likely to have more effects on some buildings than others, especially on those in urban areas. Buildings in Lagos have had nasty experiences from both natural and artificial disasters, claiming lives and properties in the past. This study aims at evaluating the disaster risks, vulnerabilities and response strategies in the high rise buildings in Lagos municipality. Structured questionnaire was administered to building owners, estate managers and disaster managers who manage the high rise buildings. The information obtained was supplemented by personal interviews conducted with tenants and rescue organizations. The study identified collapse of building, fire out break, and communication and power failure as the most likely potential disasters, power failure and collapse had the highest severity of impact, and the degree of preparedness achieved to confront the disasters was below satisfaction. However, the specific status of the response strategies was as expected, but there was room for improvements. The potential disasters were natural, human and environmental and the most vulnerable sectors were other properties rather than the high rise buildings themselves. The magnitude of risk levels could be contained with the level of response strategies already achieved if coordinated.展开更多
The behavior of building materials in constructions of civil structures is influenced by the surrounding moisture and it is a crucial for intensively examined field of the construction physics. Most standard building ...The behavior of building materials in constructions of civil structures is influenced by the surrounding moisture and it is a crucial for intensively examined field of the construction physics. Most standard building materials are characterized by a porous structure, which results in the ability to receive water in a liquid as well as gaseous form in the inner pores. The water fills the storage space of pores under certain conditions; it is transported and transferred back to the surroundings. Many technical studies show that the moisture monitoring is prevailingly based on experiments. Previous calculating methods introduced, e.g., by Glaser, which became the basis for the standard calculations in many European countries in the 1960s, are not always sufficient with respect to the demands of the civil structures. The moisture influences thermo-insulating properties of the material. By a change of the thermo insulation properties of the construction also the thermal and diffusion scheme of the construction is changed and its thermal resistance is decreasing. Faults in the thermo-technical projects occur when thermal conductivity coefficient L values for material in a dry state are substituted.The aim of the research is to determine the capillary conductivity coefficient as a characteristic material moisture parameter of the building materials by the means of a non-destructive method using the experimentally assembled apparatus developed at the Department of Civil Engineering, Brno University of Technology. Keywords： Capillary conductivity coefficient, moisture transfer, EMWR （electromagnetic microwave radiation）, diffusion展开更多
The importance of good site progress records in quality assurance; tracking project progress; preparing, analyzing and resolving claims; and placing responsibilities in the event of dispute in building contracts is wi...The importance of good site progress records in quality assurance; tracking project progress; preparing, analyzing and resolving claims; and placing responsibilities in the event of dispute in building contracts is widely recognized. This study engaged Public Building Supervisors in the assessment of site progress record keeping practices in Abuja. A simple structured questionnaire （which mainly assessed the nature and importance of records kept, reasons for keeping them; level of satisfaction with the current approach, challenges and practical ways of improving the practice） was administrated to a hundred of the supervisors, out of which seventy one was properly completed and returned. The results show that all five site progress documents （minutes of progress meetings, day-work sheets, photographs, weekly site records and personal site diaries） found in literature, are in use in Abuja, and have at least a high importance rating （i.e., relative importance index, 0.6 〈 RII 〈 0.8）. Prominent among the reasons for keeping the records are： control of ongoing work （R11 = 0.83） data for estimating future works and terms of contract requirement （each with RII = 0.823）. Though the present record keeping practices were largely assessed satisfactory, 95% of the Supervisors still yearned for improvement. The challenges to the current practice are consistent with those identified in literature and are： continuity consistency, legibility and accountability; in descending order of frequency of occurrence. Computerization, regular inspection of progress documents by assigned supervisors and in-house training of site staff are recommended for improving the record keeping practices.展开更多
BIM （building information modeling） is a technological innovation, not only during the design process, but also during the planning and preparation stages of a construction project, as it also supports making invest...BIM （building information modeling） is a technological innovation, not only during the design process, but also during the planning and preparation stages of a construction project, as it also supports making investment decisions. An innovation which is comparable, if only slightly less significant, was the transition from using 2D systems to the 3D structural model design. The article outlines the advantages of using BIM in the preparatory stages of a construction project. It also presents benefits which relate to the employment of the BIM system in cost estimation process. The article describes the Zuzia BIM system which uses the BIM model, as this system has just been created in Poland for the purpose of construction cost estimation. The preparation of the bill of quantities is automated in this system and this has been achieved on the basis of data directly obtained from virtual models of buildings, which were carried out thanks to the collaboration of various design sectors. The article authors, using their own experience, present difficulties which can be encountered by cost estimators in Poland when calculating the value of a building with the help of the BIM concept. The article shows the design errors that prevent or hinder takeoff automatic calculation based on BIM model. Design errors shown in the article are for example reinforcement bars have been defined by a designer as elements hollow in the middle or as one element for the whole building, one type of elements assigned as few different or incorrect defining of elements in relation to the type of works.展开更多
The effect of two nighttime ventilation strategies on cooling and heating energy use is investigated for a prototype office building in several northern America climates, using hourly building energy simulation softwa...The effect of two nighttime ventilation strategies on cooling and heating energy use is investigated for a prototype office building in several northern America climates, using hourly building energy simulation software （DOE2.1E）. The strategies include： scheduled-driven nighttime ventilation and a predictive method for nighttime ventilation. The maximum possible energy savings and peak demand reduction in each climate is analyzed as a function of ventilation rate, indoor-outdoor temperature difference, and building thermal mass. The results show that nighttime ventilation could save up to 32% cooling energy in an office building, while the total energy and peak demand savings for the fan and cooling is about 13% and 10%, respectively. Consequently, finding the optimal control parameters for the nighttime ventilation strategies is very important. The performance of the two strategies varies in different climates. The predictive nighttime ventilation worked better in weather conditions with fairly smooth transition from heating to cooling season.展开更多
There is a growing concern of the integration of bamboo as a material into the building construction industry even though its potential is underscored. Certain factors serve as barriers to the use of bamboo in buildin...There is a growing concern of the integration of bamboo as a material into the building construction industry even though its potential is underscored. Certain factors serve as barriers to the use of bamboo in building construction. This study employed a questionnaire survey which sought to investigate the perceptions of 84 Architects and 100 Senior Managers of small and medium scale Building construction firms on the factors that influence the use of bamboo in building construction. Relative Importance Index and Chi-squared tests were performed to identify the significant factors that influence the use of bamboo in building construction. The results showed that the building contractors considered nonspecification of bamboo for building projects by Architects, inadequate bamboo processing companies in Ghana and insufficient cooperation from government to be the key factors which influence the use of bamboo for building construction. The results further showed that the Architects considered lack of knowledge in bamboo detailing, limited knowledge of bamboo and lack of expertise to use it, and inadequate bamboo processing companies to be the key influential factors inhibiting the use of bamboo in building construction. The results are of value to the construction industry as it identifies significant factors which influence the usage of bamboo in building construction. Promotion of bamboo usage in building construction should be given the needed publicity to create the awareness of its potential as a building material.展开更多
This paper presents an investigation of the seismic behavior of reinforced concrete(RC)structures in which shear walls are the main lateral load-resisting elements and the participation of flat slab floor systems is n...This paper presents an investigation of the seismic behavior of reinforced concrete(RC)structures in which shear walls are the main lateral load-resisting elements and the participation of flat slab floor systems is not considered in the seismic design procedure.In this regard,the behavior of six prototype structures(with different heights and plan layouts)is investigated through nonlinear static and time history analyses,implemented in the OpenSees platform.The results of the analyses are presented in terms of the behavior of the slab-column connections and their mode of failure at different loading stages.Moreover,the global response of the buildings is discussed in terms of some parameters,such as lateral overstrength due to the gravity flat slab-column frames.According to the nonlinear static analyses,in structures in which the slab-column connections were designed only for gravity loads,the slab-column connections exhibited a punching mode of failure even in the early stages of loading.However,the punching failure was eliminated in structures in which a minimum transverse reinforcement recommended in ACI 318(2019)was provided in the slabs at joint regions.Furthermore,despite neglecting the contribution of gravity flat slab-column frames in the lateral load resistance of the structures,a relatively significant overstrength was imposed on the structures by the gravity frames.展开更多
文摘This paper presents a simplified method of evaluating the seismic performance of buildings. The proposed method is based on the transformation of a multiple degree of freedom (MDOF) system to an equivalent single degree of freedom (SDOF) system using a simple and intuitive process. The proposed method is intended for evaluating the seismic performance of the buildings at the intermediate stages in design, while a rigorous method would be applied to the final design. The performance of the method is evaluated using a series of buildings which are assumed to be located in Victoria in western Canada, and designed based on the upcoming version of the National Building Code of Canada which is due to be published in 2005. To resist lateral loads, some of these buildings contain reinforced concrete moment resisting frames, while others contain reinforced concrete shear walls. Each building model has been subjected to a set of site-specific seismic spectrum compatible ground motion records, and the response has been determined using the proposed method and the general method for MDOF systems. The results from the study indicate that the proposed method can serve as a useful tool for evaluation of seismic performance of buildings, and carrying out performance based design.
文摘The design code for each country is revised and updated based on an expected zone’s seismic intensities,geotechnical site classifications,structural systems,construction materials and methods of construction in order to provide more realistic considerations of seismic demand,seismic response,and seismic capacity.Based on the aforementioned provisions,structures designed according to different seismic codes may yield different performances for the same level of hazard.This study aims to investigate and compare the induced responses related to the earthquake-resistant design of reinforced concrete(RC)buildings according to the Saudi building code(SBC-301),American code(ASCE-7),uniform building code(UBC-97),and European code(EC-8).In order to account for the provision regarding the hazard specification and its effect on the induced seismic responses,four regions in the Kingdom of Saudi Arabia with different seismic levels are selected.The code provisions related to the specification of site classification and its effect on the induced design base shear are investigated as well.Significant differences are observed in the induced responses with the variation in seismic design codes for the considered seismic hazards and site classifications.
文摘Amidst the recent development in the usage of curtain walls for office buildings, high utilization of energy and poor thermal comfort issues have become paramount. This paper assesses thermal comfort in multi storey (naturally and mechanically ventilated) office buildings in Accra, the Capital city of Ghana using Fanger’s Predicted Mean Votes (PMV) and Predicted Percentage of Dissatisfied persons (PPD) model. The model relates to the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 55 (which gives an acceptable temperature range of 23℃ - 26℃) and the International Standards Organization (ISO) 7730. Indoor environmental parameters (temperature and relative humidity) of 4 multi storey office buildings were recorded over a 10 month period. The environmental parameters were analyzed using PMVcalc_v2 software which resulted in the generation of PMV-PPD values. The findings reveal high PMV-PPD values in the Naturally Ventilated Building (NVB) whiles the Mechanically Ventilated Buildings (MVB) fall within the comfort zone. Meanwhile, the Actual Mean Votes (AMV) by the occupants suggest all four buildings are relatively comfortable with the mechanically ventilated offices being more comfortable. Additionally, it is recommended that buildings are orientated with their longer sides facing north-south, with enough shading in order to improve the thermal comfort conditions of work spaces.
文摘Building defect is an issue in existing buildings that needs urgent tackling to prevent further problems. This study assessed the defects in concrete elements in residential buildings of 30 years and above in the Onitsha metropolis of Anambra State, Nigeria. Data collection instruments in the study include structured questionnaire, interviews, visual inspection/observations, archival records, recordings, photographs;and non-destructive testing of the concrete elements in an existing building in the study area. The population of this study constituted of the construction registered professionals and the existing buildings in study area. The sample for the study was based on the calculated sample size using Taro Yamani Formula. A total of 158 registered professionals were sampled from the population of 260. The questionnaires were purposively distributed to the registered professionals up to the required sample sizes of 158 and 129 questionnaires were properly filled and returned. The study used the SPSS and Microsoft Excel to analyze the data. The results were analyzed in percentages and figures using descriptive statistics and presented in the form of pie charts and tables. The finding of the study revealed that the causes and effects of structural defects on the concrete elements in existing buildings in the study area according to the rating are;exposed/corrosion of the embedded metals, faulty workmanship, overload and impacts, chemical attack, freeze-thaw deterioration, fire/heat, restraint to volume change. The visual observation revealed that the structural elements are characterized by heavy defects such as deep vertical, horizontal and diagonal cracks, exposed/ corrosion of the embedded metals, spalling of the concrete slabs. The existence of defects in the concrete members led to the low compressive strength of the concrete elements and the structural instability of the existing buildings as revealed by the non-destructive test. The non-destructive test result revealed that most of the tested concrete elements have low compressive strength value and such were remarked poor as they did not satisfy the assumed value. Essentially, the study concluded by recommending that regular monitoring, inspections and non-destructive testing of concrete elements should be conducted on existing aged and defected buildings to detect the structural stability of the buildings;and it is imperative to evacuate occupants from heavy structurally deteriorated and defected buildings since most of them have lost their residual design life span and ability to sustain imposed loads.
文摘The proliferation of multi-family residential building in Anambra State of Nigeria due to increasing demand without recourse to performance has broughtconcerns about the adequacy and sustainability of this housing type.This study therefore,assessed the adequacy and sustainability performance of multi-family residential buildings in urban areas of Anambra State.The study sampled the opinions of 384 households living in multi-family residential buildings through a questionnaire survey.We conducted data analysis based on 214 responses that were useful for analysis.The study found that internal and building component variables and supporting neigh-borhood variables were adequate,but the surrounding environment variables were inadequate based on Mean Score Index.However,based on Sustainability Performance Index,the occupant sperceived social sustainability performance of the buildings as satisfactory,while environmental and economic sustainability performance were perceived as fairly satisfactory.The Pearson correlation coefficient result further established that adequacy of internal and building component variables was significantly and positively related to the residents'perceived social sustainability performance.Adequacy of the surrounding environmental variables was also found to be positively and significantly related to the residents'perceived environmental sustainability performance,whereas adequacy of supporting neighborhood facilities was found to be negatively and significantly related to the residents’perceived economic sustainability performance.This sug-gested that investors and owners of multi-family residential buildings should direct more efforts towards improving the surrounding environment to supplements other facilities and increase the economic benefit of the renters or occupiers with increasing economic sustainability performance in terms of value for money.
基金support for the research,authorship,and/or publication of this article:the Youth Science Research Foundation of China Academy of Building Research(20160118331030053).
文摘Energy consumed by buildings accounts for approximately one-third of the total energy consumption of the society.Moreover,energy systems employed in buildings emit hazardous pollutants,such as,NOx,PM2.5 and CO2,into the environment.Consequently,increasing the energy efficiency of buildings constitutes an important problem concerning the field of building-energy and environment conservation.Thermal resistance and capacitance are two important thermophysical properties of building walls significantly impacting their heat-transfer performance.Traditional theories concerning these properties,however,face certain limitations:(1)the concept of thermal resistance is only valid for one-dimensional,steady heat conduction without existence of an internal heat source;(2)thermal resistance and capacitance are relevant,and can,therefore,not be used to analyze heat-transfer and storage performance,respectively,of building walls.Based on the entransy-dissipation-based impedance theory,a new approach towards realization of heat-transfer analysis and optimization has been proposed in this study.The weightiness of thermal resistance and capacitance with regard to heat-transfer performance has been described along with deduction of the corresponding substitutional relation via illustrative examples.The proposed approach has been demonstrated to effectively overcome aforementioned limitations of building energy conservation problems.
文摘The local design and construction practices in the United Arab Emirates （UAE）, together with Dubai＇s unique rate of development, warrant special attention to the selection of Lateral Force-Resisting Systems （LFRS）. This research proposes four different feasible solutions for the selection of the LFRS for tall buildings and quantifies the impact of these selections on seismic performance and cost. The systems considered are： Steel Special Moment-Resisting Frame （SMRF）, Concrete SMRF, Steel Dual System （SMRF with Special Steel Plates Shear Wall, SPSW）, and Concrete Dual System （SMRF with Special Concrete Shear Wall, SCSW）. The LFRS selection is driven by seismic setup as well as the adopted design and construction practices in Dubai. It is found that the concrete design alternatives are consistently less expensive than their steel counterparts. The steel dual system is expected to have the least damage based on its relatively lesser interstory drifts. However, this preferred performance comes at a higher initial construction cost. Conversely, the steel SMRF system is expected to have the most damage and associated repair cost due to its excessive flexibility. The two concrete alternatives are expected to have relatively moderate damage and repair costs in addition to their lesser initial construction cost.
基金supported by the Research Grants Council,University Grants Committee,Hong Kong SAR(Project Number:N_PolyU552/20)supported by the National Nature Science Foundation of China(22209138)Guangdong Basic and Applied Basic Research Foundation(2021A1515110464).
文摘Reversible protonic ceramic cells(RePCCs)hold promise for efficient energy storage,but their practicality is hindered by a lack of high-performance air electrode materials.Ruddlesden-Popper perovskite Sr_(3)Fe_(2)O_(7−δ)(SF)exhibits superior proton uptake and rapid ionic conduction,boosting activity.However,excessive proton uptake during RePCC operation degrades SF’s crystal structure,impacting durability.This study introduces a novel A/B-sites co-substitution strategy for modifying air electrodes,incorporating Sr-deficiency and Nb-substitution to create Sr_(2.8)Fe_(1.8)Nb_(0.2)O_(7−δ)(D-SFN).Nb stabilizes SF’s crystal,curbing excessive phase formation,and Sr-deficiency boosts oxygen vacancy concentration,optimizing oxygen transport.The D-SFN electrode demonstrates outstanding activity and durability,achieving a peak power density of 596 mW cm^(−2)in fuel cell mode and a current density of−1.19 A cm^(−2)in electrolysis mode at 1.3 V,650℃,with excellent cycling durability.This approach holds the potential for advancing robust and efficient air electrodes in RePCCs for renewable energy storage.
文摘The cooling and heating load distribution of large area air-conditioned room such as “open” offices, shopping malls and waiting rooms is usually assumed to be even in air conditioning system design. However, it is not the case in reality, and a low efficient air conditioning system results from this assumption. A simulation and analysis of the cooling load distribution of an office building in Hong Kong with TRANSYS software is provided in this paper. A typical office is divided into 13 zones for simulation, including external zone, medial zone and internal zone in the north, the south, the east and the west respectively and a central zone, instead of 4 directional zone. The result shows there is much cooling load difference between each zone, and more attention should be paid to uneven indoor cooling and heating load distribution to further guide the design.
文摘The act of unauthorized siting of buildings has persisted in most developing countries. Despite numerous efforts at local levels to address this problem, its existence and effects keep on rising in various metropolises in Ghana. This research explores the causes of unauthorized siting of buildings in Asakae, a suburb of the Sekondi-Takoradi Metropolis, and suggests measures to curb them. In view of this, a sample size of 182 house-owners was chosen for the study. Accordingly, the sample size was determined using Fisher et al. formula and questionnaire survey approach was adopted for the study. More so, data generated from the survey were further analyzed, using Relative Importance Index. The findings of the survey indicated that ignorance on planning and building regulations, inadequate housing schemes, unrealistic zonings and the location of land are critical variables which influence unauthorized siting of buildings. It is recommended that the populace should be given regular public education on land-use planning and the building regulations of Ghana. More so, the Assemblies should automate their systems, with respect to monitoring and detection of buildings under construction;so that buildings that were being located at unapproved places could be quickly detected, and appropriate measures could be taken before their completion.
文摘Degradation of timbers in building due to microorganisms was reported to cause enormous economic loses and species of Aspergillus are among the major cause of degradation of timbers in Nigeria. This research aims at evaluating the cost of implications of biodegradations of Khaya grandifoliola by Aspergiilus spp in residential buildings empirically. Decayed Khaya grandifoliola samples were collected on residential buildings to extract, cultivate and identify the Aspergillus spp present. The cultivation went through serial dilutions and inoculations on sabouraud dextrose agar in petri dishes before incubation for 72 hours at 30 ~C. The species were identified through visual and microscopic observations. Percentage rate of degradation was determined under laboratory conditions by inoculating known weights of Khaya grandifoliola with the Aspergillus and incubating in a minimal medium for 24 weeks at 30 ~C. Weight loses and spore counts were recorded at four weeks intervals. A pattern of the degradation was forecasted. Accumulative weight loss of 16% for this period was obtained. Methods and costs of repair and replacement of decayed portions were evaluated. Residential Buildings constructed of Khaya grandifoliola experienced low cost of maintenance in this region but may not be in wetter regions where the conditions could be more favorable.
文摘Moulds have been reported to destroy volumes of timbers in buildings annually. As a result, timber components within the built environment decline and fail to fulfill their basic requirements. This research focused on the isolation and evaluation of the prevalence and effects of deteriorating moulds in the rain forest and swampy rain forest regions of Nigeria where the water activity is as high as 0.7. To accomplish this, decayed timber samples were aseptically collected on buildings from six strategic locations. The samples were serially diluted and inoculated onto Sabouraud Dextrose Agar medium in Petal dishes. The Petri dishes were incubated for 72 h at 30 ~C. Thereafter, moulds were isolated through visual and microscopic observations. The commonly encountered moulds were evaluated and analyzed. It was observed that, prevalence of moulds on buildings used for non residential purpose were higher. There was no significant difference between the prevalence on the components located inside the building and those outside the building. Ceiba pentandra exhibited highest degradation while Masonia altissima resisted most. The most deteriorating moulds were Aspergillus, Mucor, Rhizopus and Gliocladium. The deteriorations of Ceiba pentandra, Afzelia africana, Lophira alata, Anogessus leocarpus and Gossweilerodendron balsamiferum timbers under Aspergillus attack were projected.
文摘Concrete is multicomponent composite material, consisting of coarse aggregate, fine aggregate, cement and water. Natural aggregates, as well as aggregates obtained after the reprocessing of buildings＇ demolition waste, can be used as coarse and fine aggregates. Characteristics of the hardened concrete depend on the raw materials, used for the preparation of concrete mixture, and their characteristics. The objective of the research is to analyse the sources of demolition waste, to describe the reprocessing technology of concrete waste, to investigate the production of the aggregate from the concrete waste, to analyse the main properties of these aggregates -- particles＇ density, bulk density, granulometric composition, hollowness and other properties, as well as to compare the obtained results with the requirements applicable to the aggregates based on natural materials.
文摘Although disasters can occur anywhere, certain types of disasters are more likely to have more effects on some buildings than others, especially on those in urban areas. Buildings in Lagos have had nasty experiences from both natural and artificial disasters, claiming lives and properties in the past. This study aims at evaluating the disaster risks, vulnerabilities and response strategies in the high rise buildings in Lagos municipality. Structured questionnaire was administered to building owners, estate managers and disaster managers who manage the high rise buildings. The information obtained was supplemented by personal interviews conducted with tenants and rescue organizations. The study identified collapse of building, fire out break, and communication and power failure as the most likely potential disasters, power failure and collapse had the highest severity of impact, and the degree of preparedness achieved to confront the disasters was below satisfaction. However, the specific status of the response strategies was as expected, but there was room for improvements. The potential disasters were natural, human and environmental and the most vulnerable sectors were other properties rather than the high rise buildings themselves. The magnitude of risk levels could be contained with the level of response strategies already achieved if coordinated.
文摘The behavior of building materials in constructions of civil structures is influenced by the surrounding moisture and it is a crucial for intensively examined field of the construction physics. Most standard building materials are characterized by a porous structure, which results in the ability to receive water in a liquid as well as gaseous form in the inner pores. The water fills the storage space of pores under certain conditions; it is transported and transferred back to the surroundings. Many technical studies show that the moisture monitoring is prevailingly based on experiments. Previous calculating methods introduced, e.g., by Glaser, which became the basis for the standard calculations in many European countries in the 1960s, are not always sufficient with respect to the demands of the civil structures. The moisture influences thermo-insulating properties of the material. By a change of the thermo insulation properties of the construction also the thermal and diffusion scheme of the construction is changed and its thermal resistance is decreasing. Faults in the thermo-technical projects occur when thermal conductivity coefficient L values for material in a dry state are substituted.The aim of the research is to determine the capillary conductivity coefficient as a characteristic material moisture parameter of the building materials by the means of a non-destructive method using the experimentally assembled apparatus developed at the Department of Civil Engineering, Brno University of Technology. Keywords： Capillary conductivity coefficient, moisture transfer, EMWR （electromagnetic microwave radiation）, diffusion
文摘The importance of good site progress records in quality assurance; tracking project progress; preparing, analyzing and resolving claims; and placing responsibilities in the event of dispute in building contracts is widely recognized. This study engaged Public Building Supervisors in the assessment of site progress record keeping practices in Abuja. A simple structured questionnaire （which mainly assessed the nature and importance of records kept, reasons for keeping them; level of satisfaction with the current approach, challenges and practical ways of improving the practice） was administrated to a hundred of the supervisors, out of which seventy one was properly completed and returned. The results show that all five site progress documents （minutes of progress meetings, day-work sheets, photographs, weekly site records and personal site diaries） found in literature, are in use in Abuja, and have at least a high importance rating （i.e., relative importance index, 0.6 〈 RII 〈 0.8）. Prominent among the reasons for keeping the records are： control of ongoing work （R11 = 0.83） data for estimating future works and terms of contract requirement （each with RII = 0.823）. Though the present record keeping practices were largely assessed satisfactory, 95% of the Supervisors still yearned for improvement. The challenges to the current practice are consistent with those identified in literature and are： continuity consistency, legibility and accountability; in descending order of frequency of occurrence. Computerization, regular inspection of progress documents by assigned supervisors and in-house training of site staff are recommended for improving the record keeping practices.
文摘BIM （building information modeling） is a technological innovation, not only during the design process, but also during the planning and preparation stages of a construction project, as it also supports making investment decisions. An innovation which is comparable, if only slightly less significant, was the transition from using 2D systems to the 3D structural model design. The article outlines the advantages of using BIM in the preparatory stages of a construction project. It also presents benefits which relate to the employment of the BIM system in cost estimation process. The article describes the Zuzia BIM system which uses the BIM model, as this system has just been created in Poland for the purpose of construction cost estimation. The preparation of the bill of quantities is automated in this system and this has been achieved on the basis of data directly obtained from virtual models of buildings, which were carried out thanks to the collaboration of various design sectors. The article authors, using their own experience, present difficulties which can be encountered by cost estimators in Poland when calculating the value of a building with the help of the BIM concept. The article shows the design errors that prevent or hinder takeoff automatic calculation based on BIM model. Design errors shown in the article are for example reinforcement bars have been defined by a designer as elements hollow in the middle or as one element for the whole building, one type of elements assigned as few different or incorrect defining of elements in relation to the type of works.
文摘The effect of two nighttime ventilation strategies on cooling and heating energy use is investigated for a prototype office building in several northern America climates, using hourly building energy simulation software （DOE2.1E）. The strategies include： scheduled-driven nighttime ventilation and a predictive method for nighttime ventilation. The maximum possible energy savings and peak demand reduction in each climate is analyzed as a function of ventilation rate, indoor-outdoor temperature difference, and building thermal mass. The results show that nighttime ventilation could save up to 32% cooling energy in an office building, while the total energy and peak demand savings for the fan and cooling is about 13% and 10%, respectively. Consequently, finding the optimal control parameters for the nighttime ventilation strategies is very important. The performance of the two strategies varies in different climates. The predictive nighttime ventilation worked better in weather conditions with fairly smooth transition from heating to cooling season.
文摘There is a growing concern of the integration of bamboo as a material into the building construction industry even though its potential is underscored. Certain factors serve as barriers to the use of bamboo in building construction. This study employed a questionnaire survey which sought to investigate the perceptions of 84 Architects and 100 Senior Managers of small and medium scale Building construction firms on the factors that influence the use of bamboo in building construction. Relative Importance Index and Chi-squared tests were performed to identify the significant factors that influence the use of bamboo in building construction. The results showed that the building contractors considered nonspecification of bamboo for building projects by Architects, inadequate bamboo processing companies in Ghana and insufficient cooperation from government to be the key factors which influence the use of bamboo for building construction. The results further showed that the Architects considered lack of knowledge in bamboo detailing, limited knowledge of bamboo and lack of expertise to use it, and inadequate bamboo processing companies to be the key influential factors inhibiting the use of bamboo in building construction. The results are of value to the construction industry as it identifies significant factors which influence the usage of bamboo in building construction. Promotion of bamboo usage in building construction should be given the needed publicity to create the awareness of its potential as a building material.
文摘This paper presents an investigation of the seismic behavior of reinforced concrete(RC)structures in which shear walls are the main lateral load-resisting elements and the participation of flat slab floor systems is not considered in the seismic design procedure.In this regard,the behavior of six prototype structures(with different heights and plan layouts)is investigated through nonlinear static and time history analyses,implemented in the OpenSees platform.The results of the analyses are presented in terms of the behavior of the slab-column connections and their mode of failure at different loading stages.Moreover,the global response of the buildings is discussed in terms of some parameters,such as lateral overstrength due to the gravity flat slab-column frames.According to the nonlinear static analyses,in structures in which the slab-column connections were designed only for gravity loads,the slab-column connections exhibited a punching mode of failure even in the early stages of loading.However,the punching failure was eliminated in structures in which a minimum transverse reinforcement recommended in ACI 318(2019)was provided in the slabs at joint regions.Furthermore,despite neglecting the contribution of gravity flat slab-column frames in the lateral load resistance of the structures,a relatively significant overstrength was imposed on the structures by the gravity frames.
