In order to investigate the flexural behaviors of engineered cementitious composites （ECC）, theoretical and experimental researches are done on flexural doublereinforced ECC beams. Based on the assumption of the pla...In order to investigate the flexural behaviors of engineered cementitious composites （ECC）, theoretical and experimental researches are done on flexural doublereinforced ECC beams. Based on the assumption of the plane section remaining plane in bending and simplified constitutive models of materials, the calculation methods of load carrying capacities for different critical stages are obtained. Then, these calculation methods are demonstrated by comparing the test results with the calculation results. Finally, based on the proposed theoretical formulae, the effects of the compression strength, compression strain and tension strength of ECC, and the reinforcement ratio on the flexural behaviors of double-reinforced ECC beams are analyzed. The calculated and measured results are in good agreement, which indicates that the theoretical model can be used to predict the momentcurvature response of steel reinforced ECC beams. And the results of parametric studies show that the increase in the compression strength of ECC can greatly improve the flexural performance of beams; the increase in the ultimate compression strain can significantly improve the ultimate curvature and ductility, but has little effect on the load bearing capacity of beams. little effect on the flexural The tensile strength of ECC has behaviors of ECC beams. The increase in the steel reinforcement ratio can lead to significant improvement of the load bearing capacity and the stiffness of beams, but a degradation of the ductility of beams. The theoretical model and parameter analysis results in this paper are instructive for the design of steel reinforced ECC beams.展开更多
Sondu-Miriu hydropower （SMHP） project experienced delay for about five years and one of the contributing factors was delayed payment of the contractor, with ripples effect extending down the contractual hierarchy. T...Sondu-Miriu hydropower （SMHP） project experienced delay for about five years and one of the contributing factors was delayed payment of the contractor, with ripples effect extending down the contractual hierarchy. This study assessed the effects of delayed payment of the contractor on the completion of SMHP project in Kisumu County, Kenya. More specifically, the study addressed two research questions： What is the relative importance of delayed payment of the contractor compared to other forms of contractual delays？ What is the perceived effect of delayed payment of the contractor on the project＇s completion？ A causal-comparative design was adopted and primary data sourced in May 2011 from 39 senior management staff of contractual parties. Relative importance index （RII） was used to determine the relative importance of perceived effects of delayed payment of the contractor on the project＇s completion; while Kendell＇s coefficient of concordance was applied to determine the degree of agreement among participants regarding their perceived effects of delayed payment. The study found that delayed payment of the contractor affected the project by causing： loss of productivity and efficiency （71.8%）; increase in time-related costs （71.8%）; re-scheduling and re-sequencing of works （69.2%）; extension of time and acceleration （69.2%）; as well as prevention of early completion （53.8%）. The study concludes that timely payment of contractors is crucial for ensuring the continuity of works and completion of infrastructural projects within time, budget, and quality specifications. The study recommends the need for appropriate mitigative measures against potential risks, such as delayed disbursement of funds by external financiers, delayed approval of contractors＇ payment requests, as well as community participation and involvement of civil society to influence accountability in the management of project funds and expedite disbursement of funds for subsequent project phases.展开更多
基金The National Natural Science Foundation of China(No.51278118)Program for Special Talents in Six Fields of Jiangsu Province(No.2011JZ010)+1 种基金the Natural Science Foundation of Jiangsu(No.BK2012756)the National Undergraduate Innovative Experiment Program(No.111028660)
文摘In order to investigate the flexural behaviors of engineered cementitious composites （ECC）, theoretical and experimental researches are done on flexural doublereinforced ECC beams. Based on the assumption of the plane section remaining plane in bending and simplified constitutive models of materials, the calculation methods of load carrying capacities for different critical stages are obtained. Then, these calculation methods are demonstrated by comparing the test results with the calculation results. Finally, based on the proposed theoretical formulae, the effects of the compression strength, compression strain and tension strength of ECC, and the reinforcement ratio on the flexural behaviors of double-reinforced ECC beams are analyzed. The calculated and measured results are in good agreement, which indicates that the theoretical model can be used to predict the momentcurvature response of steel reinforced ECC beams. And the results of parametric studies show that the increase in the compression strength of ECC can greatly improve the flexural performance of beams; the increase in the ultimate compression strain can significantly improve the ultimate curvature and ductility, but has little effect on the load bearing capacity of beams. little effect on the flexural The tensile strength of ECC has behaviors of ECC beams. The increase in the steel reinforcement ratio can lead to significant improvement of the load bearing capacity and the stiffness of beams, but a degradation of the ductility of beams. The theoretical model and parameter analysis results in this paper are instructive for the design of steel reinforced ECC beams.
文摘Sondu-Miriu hydropower （SMHP） project experienced delay for about five years and one of the contributing factors was delayed payment of the contractor, with ripples effect extending down the contractual hierarchy. This study assessed the effects of delayed payment of the contractor on the completion of SMHP project in Kisumu County, Kenya. More specifically, the study addressed two research questions： What is the relative importance of delayed payment of the contractor compared to other forms of contractual delays？ What is the perceived effect of delayed payment of the contractor on the project＇s completion？ A causal-comparative design was adopted and primary data sourced in May 2011 from 39 senior management staff of contractual parties. Relative importance index （RII） was used to determine the relative importance of perceived effects of delayed payment of the contractor on the project＇s completion; while Kendell＇s coefficient of concordance was applied to determine the degree of agreement among participants regarding their perceived effects of delayed payment. The study found that delayed payment of the contractor affected the project by causing： loss of productivity and efficiency （71.8%）; increase in time-related costs （71.8%）; re-scheduling and re-sequencing of works （69.2%）; extension of time and acceleration （69.2%）; as well as prevention of early completion （53.8%）. The study concludes that timely payment of contractors is crucial for ensuring the continuity of works and completion of infrastructural projects within time, budget, and quality specifications. The study recommends the need for appropriate mitigative measures against potential risks, such as delayed disbursement of funds by external financiers, delayed approval of contractors＇ payment requests, as well as community participation and involvement of civil society to influence accountability in the management of project funds and expedite disbursement of funds for subsequent project phases.
