Building Information Modelling (BIM) is a technology and a process that has brought changes in the construction’s traditional procurement system. Kenya lacks contractual guidelines on implementation of BIM;this makes...Building Information Modelling (BIM) is a technology and a process that has brought changes in the construction’s traditional procurement system. Kenya lacks contractual guidelines on implementation of BIM;this makes the adoption of BIM slow and difficult. Previous research has identified a gap in contractual relationships, roles and resulting risks. The objectives of this study were to investigate BIM adoption in Nairobi and to investigate the influence of BIM on Engineering Contract Management (ECM)</span><span style="font-family:Verdana;"> in Nairobi Kenya</span><span style="font-family:Verdana;">. The survey research was a descriptive study with 175 responsive questionnaires. Respondents comprised of Civil Engineers, Construction Project Managers, Architects, Quantity Surveyors, Contractors and Facility Managers. Data was collected through self-administered questionnaire and in-depth interview. Descriptive analytics, correlation and Exploratory factor analysis methods were used to analyse quantitative data. Qualitative data was analysed thematically. It emerged that adoption level was at 56.6% and shallow understanding of BIM capabilities remains to be a barrier to its adoption and implementation. It also emerged that BIM improves ECM;when time, cost, quality, collaboration and return on investment improve, ECM becomes easier. Latent factors found in BIM and ECM relationship were Legal Implications, awareness and knowledge, efficiency, versatility, mandate and leadership, and competitiveness. Further, the study found out that BIM influence on ECM demands for establishment of standards, guidelines, policy, legal framework, and regulations, which can be achieved by amending the public procurement act which dictates the operation of all the other standard forms of contract. Further research should be conducted to measure whether the understanding of BIM had positively improved.展开更多
This research evaluated the suitability of stone dust in the design and production of High Perfor-mance Concrete (HPC). HPC mix was designed, tested, costed and a comparison of concrete classes used in the market (Cla...This research evaluated the suitability of stone dust in the design and production of High Perfor-mance Concrete (HPC). HPC mix was designed, tested, costed and a comparison of concrete classes used in the market (Class 25, 30 and 35) done using Cost Benefit Analysis (CBA). The cost benefit was analyzed using Internal Rate of Return (IRR) and Net Present Value (NPV). Laboratory tests established the properties concrete obtained from the design mix. Compressive strength, slump, and modulus of elasticity were tested and analyzed. Structural analysis using BS 8110 was done for a 10 storey office building to establish the structural member sizes. Members obtained from concrete Classes 25, 30, 35 and the new compressive strengths from HPC (Class 80) were obtained and compared. Analysis was done for structural members’ sizes and area freed as a result of de-signing with HPC as well as the steel reinforcement used. To justify the initial cost of HPC if ado- pted, the Cost Benefit Analysis (CBA) was used to estimate increased costs versus income resulting from increased let table space created. The minimum class of concrete used in design was limited to Class 25 N/mm2. The research shows that it is possible to manufacture high strength concrete using locally available stone dust. The stone dust sampled from Mlolongo quarries achieved a characteristic strength of 86.7 N/mm2 at a water cement ratio of 0.32. With the results structural analysis of a 10 storey office structures with columns spaced at 8 meters center to center was de-signed using the four classes and results compared. There was a reduction of columns from 1.2 m wide to 0.65 m wide (over 45%) when concrete class changes from Class 25 to Class 80 creating over 3% of the total space area per floor. Cost benefit analysis using Net Present Value (NPV) and Internal Rate of Return (IRR) presented business case for the use of HPC. With Class 80, the IRR was at 3% and NPV being 8% of the total initial investment. The steel reinforcement increased by 8.64% using Class 30, 11.68% using Class 35 and reduced by 8.37% at Class 80. Further analysis needs to be done to understand the trend of steel reinforcement keeping all the member sizes the same. In this study the member sizes were optimized based on the steel reinforcement and serviceability. This paper provides useful information to design Engineers and Architects and inform future design of multi storey structures.展开更多
Increased surface roughness of road due to emergence of cracks makes travelling on the road uncomfortable to road users;reduces road safety;increases wear and tear of vehicles, which push up the operating costs of veh...Increased surface roughness of road due to emergence of cracks makes travelling on the road uncomfortable to road users;reduces road safety;increases wear and tear of vehicles, which push up the operating costs of vehicles, and increases travel time leading to the loss of useful man-hours to the local economy. The main objective of the study was to establish the causes of cracks on recently constructed flexible pavements with focus to Kabati to Mareira Road. To realize the study objectives, a case study was done on Kabati to Mareira road. Primary data comprising traffic count surveys;field and laboratory data for coring for compressive strength tests, tests on bearing capacity of pavement structure, and pavement deflection measurements analysis tests on improved pavement materials were undertaken on the road under study. The Secondary data on traffic axle load survey along the road under study were obtained from Kenya Rural Roads Authority, Ministry of Roads. The traffic loading was found to be 1.1 million equivalent standard axles over a design period of 15 years at a growth rate of 5%, which is on the lower limit of T4 assumed during the design stage. The material characteristics recommended in design are sufficient for the designed traffic loading. The range of UCS values was 1.12 to 5.83 MPa for soaked cores and 4.76 to 6.94 MPa for un-soaked cores. The DCP results showed that subgrade has a mean CBR of 15% and a median of 14% (subgrade class S4);the sub-base has a mean CBR of 53%, a range of 16% to 93% and thickness of 186 mm and;the base has a mean CBR of 145% a range of 20% to 433% and thickness of 137 mm. The ratio of modulus achieved after construction for base to sub-base is 2.7:1 and 10.7:1 for the sub-base and subgrade. It is concluded that design has no aspect in development and propagation of cracks. Cracks were caused by combination of factors, namely: sub-grade does not provide sufficient support to the pavement due to high base and sub-base strengths;and the variation of strength for pavement layers and the collapse of some cores during soaking process point to cases of inadequate/non-uniform mixing and insufficient curing of the pavement layers. Recommendation is made that the stabilizer content for base and sub-base to be varied in accordance with the properties of natural material being used based on frequency set out in standard specifications;and use of fully flexible pavements where the fill material adopted is alluvial or expansive clays. Emphasis should be placed on adequate pavement support. In improved pavement construction, the stabilizer should be uniformly distributed, thoroughly mixed and pavement layers sufficiently cured.展开更多
This paper considers the task of evaluating micro-accelerations arising due to the temperature shock of large elastic elements when a small spacecraft leaves the Earth’s shadow.In this case, a one-dimensional model o...This paper considers the task of evaluating micro-accelerations arising due to the temperature shock of large elastic elements when a small spacecraft leaves the Earth’s shadow.In this case, a one-dimensional model of thermal conductivity is used. Its solution wasobtained by the method of direct approximation with the construction of differenceschemes. It is shown that the accuracy of estimating micro-accelerations is commensurate with the accuracy of solving by a three-dimensional model of thermal conductivity.The proposed model allows reducing the time to obtain estimates and significantly simplifies the task at hand. The results of the work can be used in the formation of thedynamic characteristics of a small spacecraft for technological purposes.展开更多
文摘Building Information Modelling (BIM) is a technology and a process that has brought changes in the construction’s traditional procurement system. Kenya lacks contractual guidelines on implementation of BIM;this makes the adoption of BIM slow and difficult. Previous research has identified a gap in contractual relationships, roles and resulting risks. The objectives of this study were to investigate BIM adoption in Nairobi and to investigate the influence of BIM on Engineering Contract Management (ECM)</span><span style="font-family:Verdana;"> in Nairobi Kenya</span><span style="font-family:Verdana;">. The survey research was a descriptive study with 175 responsive questionnaires. Respondents comprised of Civil Engineers, Construction Project Managers, Architects, Quantity Surveyors, Contractors and Facility Managers. Data was collected through self-administered questionnaire and in-depth interview. Descriptive analytics, correlation and Exploratory factor analysis methods were used to analyse quantitative data. Qualitative data was analysed thematically. It emerged that adoption level was at 56.6% and shallow understanding of BIM capabilities remains to be a barrier to its adoption and implementation. It also emerged that BIM improves ECM;when time, cost, quality, collaboration and return on investment improve, ECM becomes easier. Latent factors found in BIM and ECM relationship were Legal Implications, awareness and knowledge, efficiency, versatility, mandate and leadership, and competitiveness. Further, the study found out that BIM influence on ECM demands for establishment of standards, guidelines, policy, legal framework, and regulations, which can be achieved by amending the public procurement act which dictates the operation of all the other standard forms of contract. Further research should be conducted to measure whether the understanding of BIM had positively improved.
文摘This research evaluated the suitability of stone dust in the design and production of High Perfor-mance Concrete (HPC). HPC mix was designed, tested, costed and a comparison of concrete classes used in the market (Class 25, 30 and 35) done using Cost Benefit Analysis (CBA). The cost benefit was analyzed using Internal Rate of Return (IRR) and Net Present Value (NPV). Laboratory tests established the properties concrete obtained from the design mix. Compressive strength, slump, and modulus of elasticity were tested and analyzed. Structural analysis using BS 8110 was done for a 10 storey office building to establish the structural member sizes. Members obtained from concrete Classes 25, 30, 35 and the new compressive strengths from HPC (Class 80) were obtained and compared. Analysis was done for structural members’ sizes and area freed as a result of de-signing with HPC as well as the steel reinforcement used. To justify the initial cost of HPC if ado- pted, the Cost Benefit Analysis (CBA) was used to estimate increased costs versus income resulting from increased let table space created. The minimum class of concrete used in design was limited to Class 25 N/mm2. The research shows that it is possible to manufacture high strength concrete using locally available stone dust. The stone dust sampled from Mlolongo quarries achieved a characteristic strength of 86.7 N/mm2 at a water cement ratio of 0.32. With the results structural analysis of a 10 storey office structures with columns spaced at 8 meters center to center was de-signed using the four classes and results compared. There was a reduction of columns from 1.2 m wide to 0.65 m wide (over 45%) when concrete class changes from Class 25 to Class 80 creating over 3% of the total space area per floor. Cost benefit analysis using Net Present Value (NPV) and Internal Rate of Return (IRR) presented business case for the use of HPC. With Class 80, the IRR was at 3% and NPV being 8% of the total initial investment. The steel reinforcement increased by 8.64% using Class 30, 11.68% using Class 35 and reduced by 8.37% at Class 80. Further analysis needs to be done to understand the trend of steel reinforcement keeping all the member sizes the same. In this study the member sizes were optimized based on the steel reinforcement and serviceability. This paper provides useful information to design Engineers and Architects and inform future design of multi storey structures.
文摘Increased surface roughness of road due to emergence of cracks makes travelling on the road uncomfortable to road users;reduces road safety;increases wear and tear of vehicles, which push up the operating costs of vehicles, and increases travel time leading to the loss of useful man-hours to the local economy. The main objective of the study was to establish the causes of cracks on recently constructed flexible pavements with focus to Kabati to Mareira Road. To realize the study objectives, a case study was done on Kabati to Mareira road. Primary data comprising traffic count surveys;field and laboratory data for coring for compressive strength tests, tests on bearing capacity of pavement structure, and pavement deflection measurements analysis tests on improved pavement materials were undertaken on the road under study. The Secondary data on traffic axle load survey along the road under study were obtained from Kenya Rural Roads Authority, Ministry of Roads. The traffic loading was found to be 1.1 million equivalent standard axles over a design period of 15 years at a growth rate of 5%, which is on the lower limit of T4 assumed during the design stage. The material characteristics recommended in design are sufficient for the designed traffic loading. The range of UCS values was 1.12 to 5.83 MPa for soaked cores and 4.76 to 6.94 MPa for un-soaked cores. The DCP results showed that subgrade has a mean CBR of 15% and a median of 14% (subgrade class S4);the sub-base has a mean CBR of 53%, a range of 16% to 93% and thickness of 186 mm and;the base has a mean CBR of 145% a range of 20% to 433% and thickness of 137 mm. The ratio of modulus achieved after construction for base to sub-base is 2.7:1 and 10.7:1 for the sub-base and subgrade. It is concluded that design has no aspect in development and propagation of cracks. Cracks were caused by combination of factors, namely: sub-grade does not provide sufficient support to the pavement due to high base and sub-base strengths;and the variation of strength for pavement layers and the collapse of some cores during soaking process point to cases of inadequate/non-uniform mixing and insufficient curing of the pavement layers. Recommendation is made that the stabilizer content for base and sub-base to be varied in accordance with the properties of natural material being used based on frequency set out in standard specifications;and use of fully flexible pavements where the fill material adopted is alluvial or expansive clays. Emphasis should be placed on adequate pavement support. In improved pavement construction, the stabilizer should be uniformly distributed, thoroughly mixed and pavement layers sufficiently cured.
文摘This paper considers the task of evaluating micro-accelerations arising due to the temperature shock of large elastic elements when a small spacecraft leaves the Earth’s shadow.In this case, a one-dimensional model of thermal conductivity is used. Its solution wasobtained by the method of direct approximation with the construction of differenceschemes. It is shown that the accuracy of estimating micro-accelerations is commensurate with the accuracy of solving by a three-dimensional model of thermal conductivity.The proposed model allows reducing the time to obtain estimates and significantly simplifies the task at hand. The results of the work can be used in the formation of thedynamic characteristics of a small spacecraft for technological purposes.
