The purpose of this study was to assess the acceptance of a model of construction and demolition waste-minimization practices by construction management senior students.This approach assumed students can informally in...The purpose of this study was to assess the acceptance of a model of construction and demolition waste-minimization practices by construction management senior students.This approach assumed students can informally influence construction industry opinions,making their decisions vital to future construction-management education standards.The capstone class of the bachelor’s degree program of one of the foremost construction management programs in the country was the sample chosen to study.It was found that a majority of the students were knowledgeable about all of the practices and had favorable opinions based on that knowledge.Most had tried more than half of the practices on a limited basis and decided they would use the practices based on these trials.The largest part of the students did not have experience applying a good number of the practices;however,almost all of those with this experience would continue to use all the practices.Identifying successful trial and application experiences and asking students how they became involved in such experiences would be useful in the implementation of a school plan to increase acceptance.展开更多
Bulgarian cultural heritage is the most important part of the national wealth and a major factor in the accreditation of the Bulgarian cultural identity. Preservation of cultural and historical heritage valuables of o...Bulgarian cultural heritage is the most important part of the national wealth and a major factor in the accreditation of the Bulgarian cultural identity. Preservation of cultural and historical heritage valuables of one nation determines its development and presents an integrated project for their use in accordance with the contemporary needs of the society. Sustainable management and adaptation of Bulgarian cultural and historical heritage buildings are a guarantee for preservation of their value, including social, economical, political, scientific, aesthetic, philosophical, spiritual, architectural, structural, archeological and sentimental aspects of this value. Regarding to this, structural preservation presents a priority of the sustainable management of Bulgarian cultural and historical heritage buildings. For that type of buildings, the traditional methods for structural strengthening are not applicable and the development of individual rehabilitation programs is required. They must always reflect the specific conditions and building's importance. The existing technical regulations in Bulgaria are presented and general recommendations for their applications and future development are done. Regarding to the Bulgarian current law and governing regulations, the implementation plan for the conservation and management is presented in this paper. Based on the analysis of the principles of the sustainable management and especially of the structural preservation, some general conclusions are made.展开更多
After decades of civil war,Yemen is in a desperate situation,and the construction industry has been suffering from low productivity and poor performance.In order to improve the productivity for the Yemeni construction...After decades of civil war,Yemen is in a desperate situation,and the construction industry has been suffering from low productivity and poor performance.In order to improve the productivity for the Yemeni construction industry,Construction enterprises must adopt the best and new technologies,new management concepts and philosophies such as Total Quality Management(TQM)and concurrent engineering(CE)owing to achieve improvements in the process of product development.To ensure the successful implementation of CE in the Yemeni construction industry,it is necessary to assess the readiness of those companies to implement CE.In this paper,the BEACON model is used to assess the readiness of the Yemeni companies to implement the concept of CE,that assist in overcoming the construction industry's poor productivity and performance.A study assessing CE implementation readiness will help to promote successful CE implementation in the construction industry and enhance the efficiency of construction companies.The results show that most of the construction companies in the Yemen are not ready to implement CE.The main reason is that the enterprises rely heavily on traditional management methods,and need to improve the organization and management technology.The research results can provide theoretical support for construction companies,especially Yemen companies,to establish basis in implementing an appropriate CE approach for improving performance,and also help international construction companies entering the Yemen construction market to cooperate and implement CE.展开更多
RFID technologies have advanced greatly and deployed successfully in many industry sectors in recent years.Construction industry could benefit from the applications of RFID technologies but as yet has not found suffic...RFID technologies have advanced greatly and deployed successfully in many industry sectors in recent years.Construction industry could benefit from the applications of RFID technologies but as yet has not found sufficient application areas.This project gives a comprehensive awareness of the RFID technologies,which focus on the investigation on the UK construction industry.The current status of RFID in construction and its potentials are specified in the analysis of questionnaires and case studies.Finally,basing on the investigations,some further tasks in developing RFID technologies are carried,including some recommendations,for the construction industry.展开更多
There is a growing recognition that highway construction and maintenance have major environmental impacts.Despite the lack of a clear protocol for designing and constructing an environmentally-friendly highway,the ind...There is a growing recognition that highway construction and maintenance have major environmental impacts.Despite the lack of a clear protocol for designing and constructing an environmentally-friendly highway,the industry experimented with sustainable alternatives since the 1970s.With an ultimate goal to develop sustainable guidelines for highway construction practices,this paper presents a general framework for the design and construction of sustainable flexible pavement system.This framework follows a similar approach to the Leadership in Energy and Environmental Design(LEED®)methodology by employing a point system to award a rating that quantifies the sustainability of the structure.The proposed framework divides factors related to highway design and construction into six major categories:sustainable sites(eight points),energy efficiency(five points),site air quality(four points),materials(ten points),water efficiency(four points),and innovative and design process(three points).The developed rating framework,referred to as Sustainable Design of Flexible Pavements(SDFlex),may be used to award a certification for sustainable highway design and construction.Different levels of certification may be awarded depending on the total earned credits from the six categories(Platinum,Gold,Silver,and Certified).A maximum score of 34 may be achieved under the aforementioned categories.It is proposed that a highway construction that satisfies the prerequisites and achieves a passing score of 10 be awarded a certified rating.The developed framework takes into consideration available technologies and the nature of the highway industry.展开更多
This paper explains various factors that contribute to saltwater intrusion, including overexploitation of freshwater resources and climate change as well as the different techniques essential for effective saltwater i...This paper explains various factors that contribute to saltwater intrusion, including overexploitation of freshwater resources and climate change as well as the different techniques essential for effective saltwater intrusion management. The impact of saltwater intrusion along coastal regions and its impact on the environment, hydrogeology and groundwater contamination. It suggests potential solutions to mitigate the impact of saltwater intrusion, including effective water management and techniques for managing SWI. The application of A.I (assessment index) serves as a guideline to correctly identify wells with SWI ranging from no intrusion, slight intrusion and strong intrusion. The challenges of saltwater intrusion in Lagos and the salinization of wells were investigated using the hydro-chemical parameters. The study identifies four wells (“AA”, “CMS”, “OBA” and “VIL”) as having high electric conductivities, indicating saline water intrusion, while other wells (“EBM”, “IKJ, and “IKO”) with lower electric conductivities, indicate little or no salt-water intrusion, and “AJ” well shows slight intrusion. The elevation of the wells also played a vital role in the SWI across coastal regions of Lagos. The study recommends continuous monitoring of coastal wells to help sustain and reduce saline intrusion. The findings of the study are important for policymakers, researchers, and practitioners who are interested in addressing the challenges of saltwater intrusion along coastal regions. We assessed the SWI across the eight (8) wells using the Assessment Index to identify wells with SWI. Wells in “CMS” and “VIL” has strong intrusions. A proposed classification system based on specific ion ratios categorizes water quality from good (+) to highly (-) contaminated (refer to Table 4). These findings underscore the need for attention and effective management strategies to address groundwater unsuitability for various purposes.展开更多
Engineering designs for mountainous highways emphasize compliance checking to ensure safety. However, relying solely on compliance checking may lead designers to minimize costs at the expense of high risk indicators, ...Engineering designs for mountainous highways emphasize compliance checking to ensure safety. However, relying solely on compliance checking may lead designers to minimize costs at the expense of high risk indicators, since the overall risk level of the highway design is unknown to the designers. This paper describes a method for the simultaneous consideration of traffic safety risks and the associated cost burden related to the appropriate planning and design of a mountainous highway. The method can be carried out in four steps: First, the highway design is represented by a new parametric framework to extract the key design variables that affect not only the life-cycle cost but also the operational safety. Second, the relationship between the life-cycle cost and the operational safety risk factors is established in the cost-estimation functions. Third, a fault tree analysis (FTA) is introduced to identify the traffic risk factors from the design variables. The safety performance of the design solutions is also assessed by the generalized linear-regression model. Fourth, a theory of acceptable risk analysis is introduced to the traffic safety assessment, and a computing algorithm is proposed to solve for a cost-efficient optimal solution within the range of acceptable risk, in order to help decision-makers. This approach was applied and examined in the Sichuan–Tibet Highway engineering project, which is located in a complex area with a large elevation gradient and a wide range of mountains. The experimental results show that the proposed approach significantly improved both the safety and cost performance of the project in the study area.展开更多
A combined dam structure using different concrete materials offers many practical benefits.There are several real-world cases where largevolume heterogeneous concrete materials have been used together.From the enginee...A combined dam structure using different concrete materials offers many practical benefits.There are several real-world cases where largevolume heterogeneous concrete materials have been used together.From the engineering design standpoint,it is crucial to understand the deformation coordination characteristics and mechanical properties of large-volume heterogeneous concrete,which affect dam safety and stability.In this study,a large dam facility was selected for a case study,and various design schemes of the combined dam structure were developed by changing the configurations of material zoning and material types for a given dam shape.Elastoplastic analysis of the damfoundation-reservoir system for six schemes was carried out under dynamic conditions,in which the concrete damaged plasticity(CDP)model,the Lagrangian finite element formulation,and a surface-to-surface contact model were utilized.To evaluate the mechanical properties of zoning interfaces and coordination characteristics,the vertical distribution of the first principal stress at the longitudinal joint was used as the critical index of deformation coordination control,and the overall deformation and damage characteristics of the dam were also investigated.Through a comparative study of the design schemes,an optimal scheme of the combined dam structure was identified:large-volume roller-compacted concrete(RCC)is recommended for the dam body upstream of the longitudinal joint,and high-volume fly ash conventional concrete(CC)for the dam body downstream of the longitudinal joint.This study provides engineers with a reference basis for combined dam structure design.展开更多
Engineering, procurement and construction (EPC) contracts are becoming the most popular form to undertake construction works on large-scale hydropower projects.?The EPC general contractors in Vietnam have been coped w...Engineering, procurement and construction (EPC) contracts are becoming the most popular form to undertake construction works on large-scale hydropower projects.?The EPC general contractors in Vietnam have been coped with lots of difficulties during the construction phase of hydropower projects, resulting in significant schedule delays and cost overrun. One of the reasons is poor Subcontractors capacity.?In order to overcome above, the current study attempts?to research on identification and control Subcontractors risks of delay process of EPC hydropower project in Vietnam.?Through summarizing international research achievements of previous researches relating on EPC hydropower projects combining with analysis characteristics of developing construction of EPC hydropower projects in Vietnam, the current study pointed out all kinds of subcontractor risk of delay process of EPC hydropower project in Vietnam;?a questionnaire with 18 risk elements was designed and then delivered to experts in EPC hydropower project management area. Based on the risk model, 11 main risk elements were identified which can be categorized into 3 groups.?Lastly, the current study proposed suggestions to reduce or avoid risks as well as approach to control risks.?Furthermore, the findings of this study can be a good managerial reference for project management teams who are working in other countries that have similar economic and investment environment to Vietnam to get their EPC construction project completed on schedule, thus ensuring the benefits to the government, the investor, the contractor, and the parties involved.展开更多
Although it has been shown that the implementation of the HHT-α method can result in improved error propagation properties in pseudodynamic testing if the equation of motion is used instead of the difference equation...Although it has been shown that the implementation of the HHT-α method can result in improved error propagation properties in pseudodynamic testing if the equation of motion is used instead of the difference equation to evaluate the next step acceleration, this paper proves that this method might lead to instability when used to solve a nonlinear system. Its unconditional stability is verified only for linear elastic systems, while for nonlinear systems, instability occurs as the step degree of convergence is less than 1. It is worth noting that the step degree of convergence can frequently be less than 1 in pseudodynamic testing, since a convergent solution is achieved only when the step degree of convergence is close to 1 regardless of whether its value is greater or less than 1. Therefore, the application of this scheme to pseudodynamic testing should be prohibited, since the possibility of instability might incorrectly destroy a specimen. Consequently, the implementation of the HHT-α method by using the difference equation to determine the next step acceleration is recommended for use in pseudodynamic testing.展开更多
To quantify the energy consumption in the process of production, transportation and processing of energy carriers, the life cycle of building energy used can be divided into two phases: on-site phase and embodied pha...To quantify the energy consumption in the process of production, transportation and processing of energy carriers, the life cycle of building energy used can be divided into two phases: on-site phase and embodied phase. As for the embodied phase, with the data in existing statistic yearbook, the consumption items of energy production and transportation were investigated. And based on the life cycle theory, an embodied coefficient of energy carriers was proposed to quantify the embodied energy consumption. Moreover, a calculation method for the embodied coefficient of energy carriers was deduced using Leontief inverse matrix based on the existing data sources. With relevant data of 2005-2007 in China, the embodied coefficients in 2005-2007 were obtained, in which the values for natural gas and thermal power are around 1.3 and 3. l, respectively; while they are 1.03-1.08 for other selected energy carriers. In addition, it is also found that the consumption in the production and processing accounts for more than 75%.展开更多
Waste Glass(WGs)and Coir Fiber(CF)are not widely utilized,even though their silica and cellulose content can be used to create construction materials.This study aimed to optimize mortar compressive strength using Resp...Waste Glass(WGs)and Coir Fiber(CF)are not widely utilized,even though their silica and cellulose content can be used to create construction materials.This study aimed to optimize mortar compressive strength using Response Surface Methodology(RSM).The Central Composite Design(CCD)was applied to determine the optimization of WGs and CF addition to the mortar compressive strength.Compressive strength and microstructure testing with Scanning Electron Microscope(SEM),Fourier-transform Infrared Spectroscopy(FT-IR),and X-Ray Diffraction(XRD)were conducted to specify the mechanical ability and bonding between the matrix,CF,and WGs.The results showed that the chemical treatment of CF produced 49.15%cellulose,with an average particle size of 1521μm.The regression of a second-order polynomial model yielded an optimum composition consisting of 12.776%WGs and 2.344%CF with a predicted compressive strength of 19.1023 MPa.C-S-H gels were identified in the mortars due to the dissolving of SiO_(2) in WGs and cement.The silica from WGs increased the C-S-H phase.CF plays a role in preventing,bridging,and branching micro-cracks before reaching maximum stress.WGs aggregates and chemically treated CF are suitable to be composited in mortar to increase compressive strength.展开更多
Shopping malls are accessed by people from all walks of life and, therefore, provision of adequate fire safety measures is equally important. In Dares Salaam, Tanzania, at large construction, use of shopping malls is ...Shopping malls are accessed by people from all walks of life and, therefore, provision of adequate fire safety measures is equally important. In Dares Salaam, Tanzania, at large construction, use of shopping malls is a relatively new experience, and risks associated with use of shopping malls, such as fire outbreak, are not evident to frequent users. The main purpose of the study is to assess awareness of fire safety measures for users and staff of two shopping malls located in Dares Salaam. The research adopted a case study strategy, and 100 respondents were involved in the study. Both random and purposive sampling methods were used to select respondents for the study. Multiple sources of evidence were used in data collection, namely literature review, observations, questionnaires and interviews. Findings indicate that both shopping malls have in place fairly fire prevention measures with varying degrees. Majority of staff and users indicated that they know fire safety measures but their poor knowledge was reflected in assessing them on diferent equipment and installations, such as foam, hose reel, sprinklers and drenchers. The paper concludes that awarenes of fire safety measure of users and staff of the two shopping malls is relatively low. It is, therefore, recommended that provision of fire safety training and instructions, such as posters for users and seminars for staff of shopping malls, shall be a main focus of shopping malls owners and responsible authorities.展开更多
The article analysis the external market environment and the situation of requirement and the competitor in market of office building with the same rank and the same type according to market research, the aim is to re...The article analysis the external market environment and the situation of requirement and the competitor in market of office building with the same rank and the same type according to market research, the aim is to research the whole processing operation and management, including making the marker orientation, confirming and finding the potential lesse making the rent plan, negotiating and signing the contract.展开更多
Systematic approach to the maintenance of rural road network is a very important issue from the viewpoint of public costs. Most countries developed custom PMS (pavement management systems) based on deterministic or ...Systematic approach to the maintenance of rural road network is a very important issue from the viewpoint of public costs. Most countries developed custom PMS (pavement management systems) based on deterministic or probabilistic approach. The main goal is to ensure safety and continuity of road traffic on road network with low intensity and lower technical requirements. Article presents PMS used for Slovakia rural road network based on road construction diagnostics, traffic volume, climate factors and evaluation of maintenance works economics effectives by using of software tools like HDM-4 developed by World Bank. Local road administrators of rural road networks often lack the software equipment, most PMS, however effective, are often cumbersome, demanding in regard to energy, know-how and software equipment. The majority of local road administrators of rural road networks thus resort to non-effective reactive maintenance strategies. This article describes an easy to use method, based on predetermined maintenance repair and rehabilitation standards. A simple method, based on road user cost, is introduced that administrator can use to prepare a list of road section eligible for repair according to their repair priority.展开更多
A Geothermal Heat Pump (GHP) system is known to have enormous potential for building energy savings and the reduction of associated greenhouse gas emissions, due to its high Coefficient Of Performance (COP). The use o...A Geothermal Heat Pump (GHP) system is known to have enormous potential for building energy savings and the reduction of associated greenhouse gas emissions, due to its high Coefficient Of Performance (COP). The use of a GHP system in cold-climate regions is more attractive owing to its higher COP for heating compared to conventional heating devices, such as furnaces or boilers. Many factors, however, determine the operational performance of an existing GHP system, such as control strategy, part/full-load efficiency, the age of the system, defective parts, and whether or not regular maintenance services are provided. The omitting of any of these factors in design and operation stages could have significant impacts on the normal operation of GHP systems. Therefore, the objectives of this paper are to further investigate and study the existing GHP systems currently used in buildings located in cold-climate regions of the US, in terms of system operational performance, potential energy and energy cost savings, system cost information, the reasons for installing geothermal systems, current operating difficulties, and owner satisfaction to date. After the comprehensive investigation and in-depth analysis of 24 buildings, the results indicate that for these buildings, about 75% of the building owners are very satisfied with their GHP systems in terms of noise, cost, and indoor comfort. About 71% of the investigated GHP systems have not had serious operating difficulties, and about 85% of the respondents (building owners) would suggest this type of system to other people. Compared to the national median of energy use and energy cost of typical buildings of the same type nationwide, the overall performance of the actual GHP systems used in the cold-climate regions is slightly better, i.e. about 7.2% energy savings and 6.1% energy cost savings on average.展开更多
Bifacial photovoltaic (PV) modules offer potentially enhanced power output over conventional modules due to their reported ability to harvest reflected radiation, increasing output up to an additional 30%. However, th...Bifacial photovoltaic (PV) modules offer potentially enhanced power output over conventional modules due to their reported ability to harvest reflected radiation, increasing output up to an additional 30%. However, this enhancement has yet to be confirmed in the literature. This paper reports on a study comparing the power output of two nominally identical 700 W photovoltaic arrays utilizing equivalent system components and data logging equipment with varying configurations of reflecting geometries and materials. This study was undertaken at the Appalachian State University Solar Research Laboratory in Boone, NC, which houses two Class 1 pyranometers and pyrheliometer. PV power was reported under well-quantified irradiance conditions, including direct beam fraction. Six trials over six months (November-April) with varying reflective materials and geometries revealed that different reflecting materials did not significantly change power output. Mounting an array at 0° did adversely affect power output compared to the array at a 36° angle relative to horizontal using the same reflective material. Additional studies with varied materials, panel locations and geometries different from those tested may improve the power output.展开更多
Microbial-induced calcium carbonate precipitation is a promising technology for self-healing concrete due to its capability to seal microcracks.The main goal of this study was to evaluate the effects of adding hydroge...Microbial-induced calcium carbonate precipitation is a promising technology for self-healing concrete due to its capability to seal microcracks.The main goal of this study was to evaluate the effects of adding hydrogelencapsulated bacteria on the compressive strength and the self-healing efficiency of concrete.To achieve this objective,12 sets of mortar samples were prepared,including three different mineral precursors(magnesium acetate,calcium lactate,and sodium lactate),at two concentrations(67.76 and 75.00 mM/L),and under two different biological conditions(with and without bacteria).In addition,a set of plain mortar samples was prepared to serve as a control.For each sample set,three mortar cubes and three beams were prepared and subjected to compression and flexural strength tests.From the compression tests,it was found that the sample containing calcium lactate along with yeast extract and bacteria displayed the best results.As for the flexural tests,once cracked,the beams were subjected to 28 d of wet/dry cycles(16 h of water immersion and 8 h of drying),where the bottom crack width was monitored(at 0,3,7,14,28 d of wet/dry cycles).Once the sample with the highest healing efficiency was identified(the one containing calcium lactate and hydrogel-encapsulated bacteria),the study was scaled up to concrete specimens.Two sets of concrete cylinders(consisting of three control samples and three samples with bacteria along with calcium lactate)were tested under compression in order to evaluate the effect of the bacteria-precursor combination on the concrete mechanical properties.The samples that yielded the greatest compressive strength were the ones containing calcium lactate and bacteria,displaying an improvement of 17%as compared to the control specimen.Furthermore,a flexural strength recovery analysis was performed on the concrete specimens revealing that the control showed better flexural strength recovery than the bacteriacontaining variant(41.5%vs.26.1%)after 28 d of wet/dry cycles.A healing efficiency analysis was also performed on the cracked samples,revealing that the control displayed the best results.These results are due to the fact that the control specimen showed a narrower crack width in comparison to the bacteria-containing samples.展开更多
Based on real jobs, this study was carried out the railway maintenance works in Taiwan. It hopes to use GIS (geographic information system) and BIM (building information modeling) for changing the maintenance mode...Based on real jobs, this study was carried out the railway maintenance works in Taiwan. It hopes to use GIS (geographic information system) and BIM (building information modeling) for changing the maintenance model from "post-damage repair" to "preventive maintenance" accordingly, this research will build a railway repairing database that installs all repair data. This database will also connect to GIS so that can be the source of analysis and statistic for repair paln. The main results of research are as follows: (l) all data stored on cloud space that raises the ability to manage and plan on repair; (2) simplify the file work and increase the quantity of case data to the manager who can get more reliable source; (3) the data offer objective judgment to avoid subjective argument. The GIS information can be added to improve the maintenance because of good analysis.展开更多
文摘The purpose of this study was to assess the acceptance of a model of construction and demolition waste-minimization practices by construction management senior students.This approach assumed students can informally influence construction industry opinions,making their decisions vital to future construction-management education standards.The capstone class of the bachelor’s degree program of one of the foremost construction management programs in the country was the sample chosen to study.It was found that a majority of the students were knowledgeable about all of the practices and had favorable opinions based on that knowledge.Most had tried more than half of the practices on a limited basis and decided they would use the practices based on these trials.The largest part of the students did not have experience applying a good number of the practices;however,almost all of those with this experience would continue to use all the practices.Identifying successful trial and application experiences and asking students how they became involved in such experiences would be useful in the implementation of a school plan to increase acceptance.
文摘Bulgarian cultural heritage is the most important part of the national wealth and a major factor in the accreditation of the Bulgarian cultural identity. Preservation of cultural and historical heritage valuables of one nation determines its development and presents an integrated project for their use in accordance with the contemporary needs of the society. Sustainable management and adaptation of Bulgarian cultural and historical heritage buildings are a guarantee for preservation of their value, including social, economical, political, scientific, aesthetic, philosophical, spiritual, architectural, structural, archeological and sentimental aspects of this value. Regarding to this, structural preservation presents a priority of the sustainable management of Bulgarian cultural and historical heritage buildings. For that type of buildings, the traditional methods for structural strengthening are not applicable and the development of individual rehabilitation programs is required. They must always reflect the specific conditions and building's importance. The existing technical regulations in Bulgaria are presented and general recommendations for their applications and future development are done. Regarding to the Bulgarian current law and governing regulations, the implementation plan for the conservation and management is presented in this paper. Based on the analysis of the principles of the sustainable management and especially of the structural preservation, some general conclusions are made.
基金This paper was part of a research work sponsored by the National Thirteenth-Five-year Research Program of China(Project No.:2018YFC0705901)The authors would like to thank the anonymous reviewersfor their valuable comments and suggestions to improvethe quality of the paper. They also gratefully acknowledgethe Public Works Office in Yemen for facilitating duringthe data collection stage.
文摘After decades of civil war,Yemen is in a desperate situation,and the construction industry has been suffering from low productivity and poor performance.In order to improve the productivity for the Yemeni construction industry,Construction enterprises must adopt the best and new technologies,new management concepts and philosophies such as Total Quality Management(TQM)and concurrent engineering(CE)owing to achieve improvements in the process of product development.To ensure the successful implementation of CE in the Yemeni construction industry,it is necessary to assess the readiness of those companies to implement CE.In this paper,the BEACON model is used to assess the readiness of the Yemeni companies to implement the concept of CE,that assist in overcoming the construction industry's poor productivity and performance.A study assessing CE implementation readiness will help to promote successful CE implementation in the construction industry and enhance the efficiency of construction companies.The results show that most of the construction companies in the Yemen are not ready to implement CE.The main reason is that the enterprises rely heavily on traditional management methods,and need to improve the organization and management technology.The research results can provide theoretical support for construction companies,especially Yemen companies,to establish basis in implementing an appropriate CE approach for improving performance,and also help international construction companies entering the Yemen construction market to cooperate and implement CE.
文摘RFID technologies have advanced greatly and deployed successfully in many industry sectors in recent years.Construction industry could benefit from the applications of RFID technologies but as yet has not found sufficient application areas.This project gives a comprehensive awareness of the RFID technologies,which focus on the investigation on the UK construction industry.The current status of RFID in construction and its potentials are specified in the analysis of questionnaires and case studies.Finally,basing on the investigations,some further tasks in developing RFID technologies are carried,including some recommendations,for the construction industry.
文摘There is a growing recognition that highway construction and maintenance have major environmental impacts.Despite the lack of a clear protocol for designing and constructing an environmentally-friendly highway,the industry experimented with sustainable alternatives since the 1970s.With an ultimate goal to develop sustainable guidelines for highway construction practices,this paper presents a general framework for the design and construction of sustainable flexible pavement system.This framework follows a similar approach to the Leadership in Energy and Environmental Design(LEED®)methodology by employing a point system to award a rating that quantifies the sustainability of the structure.The proposed framework divides factors related to highway design and construction into six major categories:sustainable sites(eight points),energy efficiency(five points),site air quality(four points),materials(ten points),water efficiency(four points),and innovative and design process(three points).The developed rating framework,referred to as Sustainable Design of Flexible Pavements(SDFlex),may be used to award a certification for sustainable highway design and construction.Different levels of certification may be awarded depending on the total earned credits from the six categories(Platinum,Gold,Silver,and Certified).A maximum score of 34 may be achieved under the aforementioned categories.It is proposed that a highway construction that satisfies the prerequisites and achieves a passing score of 10 be awarded a certified rating.The developed framework takes into consideration available technologies and the nature of the highway industry.
文摘This paper explains various factors that contribute to saltwater intrusion, including overexploitation of freshwater resources and climate change as well as the different techniques essential for effective saltwater intrusion management. The impact of saltwater intrusion along coastal regions and its impact on the environment, hydrogeology and groundwater contamination. It suggests potential solutions to mitigate the impact of saltwater intrusion, including effective water management and techniques for managing SWI. The application of A.I (assessment index) serves as a guideline to correctly identify wells with SWI ranging from no intrusion, slight intrusion and strong intrusion. The challenges of saltwater intrusion in Lagos and the salinization of wells were investigated using the hydro-chemical parameters. The study identifies four wells (“AA”, “CMS”, “OBA” and “VIL”) as having high electric conductivities, indicating saline water intrusion, while other wells (“EBM”, “IKJ, and “IKO”) with lower electric conductivities, indicate little or no salt-water intrusion, and “AJ” well shows slight intrusion. The elevation of the wells also played a vital role in the SWI across coastal regions of Lagos. The study recommends continuous monitoring of coastal wells to help sustain and reduce saline intrusion. The findings of the study are important for policymakers, researchers, and practitioners who are interested in addressing the challenges of saltwater intrusion along coastal regions. We assessed the SWI across the eight (8) wells using the Assessment Index to identify wells with SWI. Wells in “CMS” and “VIL” has strong intrusions. A proposed classification system based on specific ion ratios categorizes water quality from good (+) to highly (-) contaminated (refer to Table 4). These findings underscore the need for attention and effective management strategies to address groundwater unsuitability for various purposes.
基金the National Natural Science Foundation of China (71732001, 51878311, and 51678265)the Research Project of the Chinese Academy of Engineering (2017-XZ-12).
文摘Engineering designs for mountainous highways emphasize compliance checking to ensure safety. However, relying solely on compliance checking may lead designers to minimize costs at the expense of high risk indicators, since the overall risk level of the highway design is unknown to the designers. This paper describes a method for the simultaneous consideration of traffic safety risks and the associated cost burden related to the appropriate planning and design of a mountainous highway. The method can be carried out in four steps: First, the highway design is represented by a new parametric framework to extract the key design variables that affect not only the life-cycle cost but also the operational safety. Second, the relationship between the life-cycle cost and the operational safety risk factors is established in the cost-estimation functions. Third, a fault tree analysis (FTA) is introduced to identify the traffic risk factors from the design variables. The safety performance of the design solutions is also assessed by the generalized linear-regression model. Fourth, a theory of acceptable risk analysis is introduced to the traffic safety assessment, and a computing algorithm is proposed to solve for a cost-efficient optimal solution within the range of acceptable risk, in order to help decision-makers. This approach was applied and examined in the Sichuan–Tibet Highway engineering project, which is located in a complex area with a large elevation gradient and a wide range of mountains. The experimental results show that the proposed approach significantly improved both the safety and cost performance of the project in the study area.
基金supported by the National Natural Science Foundation of China(Grant No.51879185)the Fund of the National Dam Safety Research Center(Grant No.CX2019B02).
文摘A combined dam structure using different concrete materials offers many practical benefits.There are several real-world cases where largevolume heterogeneous concrete materials have been used together.From the engineering design standpoint,it is crucial to understand the deformation coordination characteristics and mechanical properties of large-volume heterogeneous concrete,which affect dam safety and stability.In this study,a large dam facility was selected for a case study,and various design schemes of the combined dam structure were developed by changing the configurations of material zoning and material types for a given dam shape.Elastoplastic analysis of the damfoundation-reservoir system for six schemes was carried out under dynamic conditions,in which the concrete damaged plasticity(CDP)model,the Lagrangian finite element formulation,and a surface-to-surface contact model were utilized.To evaluate the mechanical properties of zoning interfaces and coordination characteristics,the vertical distribution of the first principal stress at the longitudinal joint was used as the critical index of deformation coordination control,and the overall deformation and damage characteristics of the dam were also investigated.Through a comparative study of the design schemes,an optimal scheme of the combined dam structure was identified:large-volume roller-compacted concrete(RCC)is recommended for the dam body upstream of the longitudinal joint,and high-volume fly ash conventional concrete(CC)for the dam body downstream of the longitudinal joint.This study provides engineers with a reference basis for combined dam structure design.
文摘Engineering, procurement and construction (EPC) contracts are becoming the most popular form to undertake construction works on large-scale hydropower projects.?The EPC general contractors in Vietnam have been coped with lots of difficulties during the construction phase of hydropower projects, resulting in significant schedule delays and cost overrun. One of the reasons is poor Subcontractors capacity.?In order to overcome above, the current study attempts?to research on identification and control Subcontractors risks of delay process of EPC hydropower project in Vietnam.?Through summarizing international research achievements of previous researches relating on EPC hydropower projects combining with analysis characteristics of developing construction of EPC hydropower projects in Vietnam, the current study pointed out all kinds of subcontractor risk of delay process of EPC hydropower project in Vietnam;?a questionnaire with 18 risk elements was designed and then delivered to experts in EPC hydropower project management area. Based on the risk model, 11 main risk elements were identified which can be categorized into 3 groups.?Lastly, the current study proposed suggestions to reduce or avoid risks as well as approach to control risks.?Furthermore, the findings of this study can be a good managerial reference for project management teams who are working in other countries that have similar economic and investment environment to Vietnam to get their EPC construction project completed on schedule, thus ensuring the benefits to the government, the investor, the contractor, and the parties involved.
基金Science Council of Chinese Taipei Under Grant No. NSC-94-2211-E-027-011
文摘Although it has been shown that the implementation of the HHT-α method can result in improved error propagation properties in pseudodynamic testing if the equation of motion is used instead of the difference equation to evaluate the next step acceleration, this paper proves that this method might lead to instability when used to solve a nonlinear system. Its unconditional stability is verified only for linear elastic systems, while for nonlinear systems, instability occurs as the step degree of convergence is less than 1. It is worth noting that the step degree of convergence can frequently be less than 1 in pseudodynamic testing, since a convergent solution is achieved only when the step degree of convergence is close to 1 regardless of whether its value is greater or less than 1. Therefore, the application of this scheme to pseudodynamic testing should be prohibited, since the possibility of instability might incorrectly destroy a specimen. Consequently, the implementation of the HHT-α method by using the difference equation to determine the next step acceleration is recommended for use in pseudodynamic testing.
基金Project(CDJZR10210009) supported by Central College General Fund for Natural Science of Chongqing City,China
文摘To quantify the energy consumption in the process of production, transportation and processing of energy carriers, the life cycle of building energy used can be divided into two phases: on-site phase and embodied phase. As for the embodied phase, with the data in existing statistic yearbook, the consumption items of energy production and transportation were investigated. And based on the life cycle theory, an embodied coefficient of energy carriers was proposed to quantify the embodied energy consumption. Moreover, a calculation method for the embodied coefficient of energy carriers was deduced using Leontief inverse matrix based on the existing data sources. With relevant data of 2005-2007 in China, the embodied coefficients in 2005-2007 were obtained, in which the values for natural gas and thermal power are around 1.3 and 3. l, respectively; while they are 1.03-1.08 for other selected energy carriers. In addition, it is also found that the consumption in the production and processing accounts for more than 75%.
基金funded by the Ministry of Education,Culture,Research,and the Technology,Indonesia for Matching Fund (Kedaireka)Scheme in 2022 with Contract No.155/E1/KS.06.02/2022.
文摘Waste Glass(WGs)and Coir Fiber(CF)are not widely utilized,even though their silica and cellulose content can be used to create construction materials.This study aimed to optimize mortar compressive strength using Response Surface Methodology(RSM).The Central Composite Design(CCD)was applied to determine the optimization of WGs and CF addition to the mortar compressive strength.Compressive strength and microstructure testing with Scanning Electron Microscope(SEM),Fourier-transform Infrared Spectroscopy(FT-IR),and X-Ray Diffraction(XRD)were conducted to specify the mechanical ability and bonding between the matrix,CF,and WGs.The results showed that the chemical treatment of CF produced 49.15%cellulose,with an average particle size of 1521μm.The regression of a second-order polynomial model yielded an optimum composition consisting of 12.776%WGs and 2.344%CF with a predicted compressive strength of 19.1023 MPa.C-S-H gels were identified in the mortars due to the dissolving of SiO_(2) in WGs and cement.The silica from WGs increased the C-S-H phase.CF plays a role in preventing,bridging,and branching micro-cracks before reaching maximum stress.WGs aggregates and chemically treated CF are suitable to be composited in mortar to increase compressive strength.
文摘Shopping malls are accessed by people from all walks of life and, therefore, provision of adequate fire safety measures is equally important. In Dares Salaam, Tanzania, at large construction, use of shopping malls is a relatively new experience, and risks associated with use of shopping malls, such as fire outbreak, are not evident to frequent users. The main purpose of the study is to assess awareness of fire safety measures for users and staff of two shopping malls located in Dares Salaam. The research adopted a case study strategy, and 100 respondents were involved in the study. Both random and purposive sampling methods were used to select respondents for the study. Multiple sources of evidence were used in data collection, namely literature review, observations, questionnaires and interviews. Findings indicate that both shopping malls have in place fairly fire prevention measures with varying degrees. Majority of staff and users indicated that they know fire safety measures but their poor knowledge was reflected in assessing them on diferent equipment and installations, such as foam, hose reel, sprinklers and drenchers. The paper concludes that awarenes of fire safety measure of users and staff of the two shopping malls is relatively low. It is, therefore, recommended that provision of fire safety training and instructions, such as posters for users and seminars for staff of shopping malls, shall be a main focus of shopping malls owners and responsible authorities.
文摘The article analysis the external market environment and the situation of requirement and the competitor in market of office building with the same rank and the same type according to market research, the aim is to research the whole processing operation and management, including making the marker orientation, confirming and finding the potential lesse making the rent plan, negotiating and signing the contract.
文摘Systematic approach to the maintenance of rural road network is a very important issue from the viewpoint of public costs. Most countries developed custom PMS (pavement management systems) based on deterministic or probabilistic approach. The main goal is to ensure safety and continuity of road traffic on road network with low intensity and lower technical requirements. Article presents PMS used for Slovakia rural road network based on road construction diagnostics, traffic volume, climate factors and evaluation of maintenance works economics effectives by using of software tools like HDM-4 developed by World Bank. Local road administrators of rural road networks often lack the software equipment, most PMS, however effective, are often cumbersome, demanding in regard to energy, know-how and software equipment. The majority of local road administrators of rural road networks thus resort to non-effective reactive maintenance strategies. This article describes an easy to use method, based on predetermined maintenance repair and rehabilitation standards. A simple method, based on road user cost, is introduced that administrator can use to prepare a list of road section eligible for repair according to their repair priority.
文摘A Geothermal Heat Pump (GHP) system is known to have enormous potential for building energy savings and the reduction of associated greenhouse gas emissions, due to its high Coefficient Of Performance (COP). The use of a GHP system in cold-climate regions is more attractive owing to its higher COP for heating compared to conventional heating devices, such as furnaces or boilers. Many factors, however, determine the operational performance of an existing GHP system, such as control strategy, part/full-load efficiency, the age of the system, defective parts, and whether or not regular maintenance services are provided. The omitting of any of these factors in design and operation stages could have significant impacts on the normal operation of GHP systems. Therefore, the objectives of this paper are to further investigate and study the existing GHP systems currently used in buildings located in cold-climate regions of the US, in terms of system operational performance, potential energy and energy cost savings, system cost information, the reasons for installing geothermal systems, current operating difficulties, and owner satisfaction to date. After the comprehensive investigation and in-depth analysis of 24 buildings, the results indicate that for these buildings, about 75% of the building owners are very satisfied with their GHP systems in terms of noise, cost, and indoor comfort. About 71% of the investigated GHP systems have not had serious operating difficulties, and about 85% of the respondents (building owners) would suggest this type of system to other people. Compared to the national median of energy use and energy cost of typical buildings of the same type nationwide, the overall performance of the actual GHP systems used in the cold-climate regions is slightly better, i.e. about 7.2% energy savings and 6.1% energy cost savings on average.
文摘Bifacial photovoltaic (PV) modules offer potentially enhanced power output over conventional modules due to their reported ability to harvest reflected radiation, increasing output up to an additional 30%. However, this enhancement has yet to be confirmed in the literature. This paper reports on a study comparing the power output of two nominally identical 700 W photovoltaic arrays utilizing equivalent system components and data logging equipment with varying configurations of reflecting geometries and materials. This study was undertaken at the Appalachian State University Solar Research Laboratory in Boone, NC, which houses two Class 1 pyranometers and pyrheliometer. PV power was reported under well-quantified irradiance conditions, including direct beam fraction. Six trials over six months (November-April) with varying reflective materials and geometries revealed that different reflecting materials did not significantly change power output. Mounting an array at 0° did adversely affect power output compared to the array at a 36° angle relative to horizontal using the same reflective material. Additional studies with varied materials, panel locations and geometries different from those tested may improve the power output.
基金The financial support of the Transportation Consortium of SouthCentral States(Tran-SET)is greatly appreciated(Tran-SET Project 20CLSU05 Grant Number 69A3551747106).
文摘Microbial-induced calcium carbonate precipitation is a promising technology for self-healing concrete due to its capability to seal microcracks.The main goal of this study was to evaluate the effects of adding hydrogelencapsulated bacteria on the compressive strength and the self-healing efficiency of concrete.To achieve this objective,12 sets of mortar samples were prepared,including three different mineral precursors(magnesium acetate,calcium lactate,and sodium lactate),at two concentrations(67.76 and 75.00 mM/L),and under two different biological conditions(with and without bacteria).In addition,a set of plain mortar samples was prepared to serve as a control.For each sample set,three mortar cubes and three beams were prepared and subjected to compression and flexural strength tests.From the compression tests,it was found that the sample containing calcium lactate along with yeast extract and bacteria displayed the best results.As for the flexural tests,once cracked,the beams were subjected to 28 d of wet/dry cycles(16 h of water immersion and 8 h of drying),where the bottom crack width was monitored(at 0,3,7,14,28 d of wet/dry cycles).Once the sample with the highest healing efficiency was identified(the one containing calcium lactate and hydrogel-encapsulated bacteria),the study was scaled up to concrete specimens.Two sets of concrete cylinders(consisting of three control samples and three samples with bacteria along with calcium lactate)were tested under compression in order to evaluate the effect of the bacteria-precursor combination on the concrete mechanical properties.The samples that yielded the greatest compressive strength were the ones containing calcium lactate and bacteria,displaying an improvement of 17%as compared to the control specimen.Furthermore,a flexural strength recovery analysis was performed on the concrete specimens revealing that the control showed better flexural strength recovery than the bacteriacontaining variant(41.5%vs.26.1%)after 28 d of wet/dry cycles.A healing efficiency analysis was also performed on the cracked samples,revealing that the control displayed the best results.These results are due to the fact that the control specimen showed a narrower crack width in comparison to the bacteria-containing samples.
文摘Based on real jobs, this study was carried out the railway maintenance works in Taiwan. It hopes to use GIS (geographic information system) and BIM (building information modeling) for changing the maintenance model from "post-damage repair" to "preventive maintenance" accordingly, this research will build a railway repairing database that installs all repair data. This database will also connect to GIS so that can be the source of analysis and statistic for repair paln. The main results of research are as follows: (l) all data stored on cloud space that raises the ability to manage and plan on repair; (2) simplify the file work and increase the quantity of case data to the manager who can get more reliable source; (3) the data offer objective judgment to avoid subjective argument. The GIS information can be added to improve the maintenance because of good analysis.