Increasing traffic volumes and loads as well as public expectation for a long-lasting transportation infrastructure have necessitated designing perpetual pavements. The KDOT （Kansas Department of Transportation） con...Increasing traffic volumes and loads as well as public expectation for a long-lasting transportation infrastructure have necessitated designing perpetual pavements. The KDOT （Kansas Department of Transportation） conducted a field trial to investigate the suitability of perpetual pavement concept for Kansas highway pavements. The experiment involved construction of four thick pavement structures. To verify the approach of designing perpetual pavements on the basis of an endurance strain limit, the pavements were instrumented with gauges for measuring tensile strains at the bottom of asphalt base layers at various speeds. Pavements were also instrumented with pressure cells to measure stress on the top of subgrade. Pavement response measurements under known vehicle load were performed in August 2006. FWD （Falling-weight deflectometer） was also used to collect deflection data at 15 m intervals on the same date. FWD first-sensor （center） deflections were normalized and corrected to 20 ℃ temperature based on measured mid-depth pavement temperature. The result shows that strain and stress measurements show significant amount of variations. Measurements in the thickest section are the most consistent. The higher the traffic speed, the lower the strains and stresses. The difference between strains and stresses at 30 kmhar and 65 km/hr is higher than the difference between 65 km/hr and 95 kin/hr. This shows the effect of speed on stresses and strains decreases as the speed increases. Softer binder in the asphalt base layer results in lower strains, which confirms that softer binder results in higher fatigue life.展开更多
In order to achieve high quality that not only gives acceptable return value to society but also satisfies the needs of all the stakeholders of infrastructure projects, comprehensive understanding of issues pertaining...In order to achieve high quality that not only gives acceptable return value to society but also satisfies the needs of all the stakeholders of infrastructure projects, comprehensive understanding of issues pertaining to the quality of the project is needed. The aim of this study is to provide an overview the most common procurement methods used in constructing infrastructure transport projects and analyze how these methods contribute to the desired quality of the final product in relation to client competence. An on-line survey of construction actors was carried out to ascertain quality level of Swedish infrastructure transport projects and determinant factors of quality problems. An equal number of respondents indicated that the quality of infrastructure projects has either increased or remained same level over the past twenty years. Respondents also pointed out lack of client competence that is vital in realizing the desired quality level through proper procurement, monitoring and evaluation procedures. Public clients heavily rely on traditional design-build procurement that requires considerable client involvement of a project. Thus, the association of quality problems and lack of client competence may not be a mere coincidence but an overlooked outcome of current situation.展开更多
文摘Increasing traffic volumes and loads as well as public expectation for a long-lasting transportation infrastructure have necessitated designing perpetual pavements. The KDOT （Kansas Department of Transportation） conducted a field trial to investigate the suitability of perpetual pavement concept for Kansas highway pavements. The experiment involved construction of four thick pavement structures. To verify the approach of designing perpetual pavements on the basis of an endurance strain limit, the pavements were instrumented with gauges for measuring tensile strains at the bottom of asphalt base layers at various speeds. Pavements were also instrumented with pressure cells to measure stress on the top of subgrade. Pavement response measurements under known vehicle load were performed in August 2006. FWD （Falling-weight deflectometer） was also used to collect deflection data at 15 m intervals on the same date. FWD first-sensor （center） deflections were normalized and corrected to 20 ℃ temperature based on measured mid-depth pavement temperature. The result shows that strain and stress measurements show significant amount of variations. Measurements in the thickest section are the most consistent. The higher the traffic speed, the lower the strains and stresses. The difference between strains and stresses at 30 kmhar and 65 km/hr is higher than the difference between 65 km/hr and 95 kin/hr. This shows the effect of speed on stresses and strains decreases as the speed increases. Softer binder in the asphalt base layer results in lower strains, which confirms that softer binder results in higher fatigue life.
文摘In order to achieve high quality that not only gives acceptable return value to society but also satisfies the needs of all the stakeholders of infrastructure projects, comprehensive understanding of issues pertaining to the quality of the project is needed. The aim of this study is to provide an overview the most common procurement methods used in constructing infrastructure transport projects and analyze how these methods contribute to the desired quality of the final product in relation to client competence. An on-line survey of construction actors was carried out to ascertain quality level of Swedish infrastructure transport projects and determinant factors of quality problems. An equal number of respondents indicated that the quality of infrastructure projects has either increased or remained same level over the past twenty years. Respondents also pointed out lack of client competence that is vital in realizing the desired quality level through proper procurement, monitoring and evaluation procedures. Public clients heavily rely on traditional design-build procurement that requires considerable client involvement of a project. Thus, the association of quality problems and lack of client competence may not be a mere coincidence but an overlooked outcome of current situation.
