College of Engineering

This paper uses a newly developed framework for quantifying current and future greenhouse gas (GHG) emissions from Africa’s road transportation sector. It provides first-order estimates for road infrastructure projects (new road construction and existing road maintenance and rehabilitation) and vehicle-related emissions through 2050. Africa's current road network was estimated from available data, and its future growth (2021-2050) was modeled using three approaches. Road construction makes up the majority of GHG emissions from infrastructure built before 2021, with culverts and bridges contributing smaller but still significant amounts. By 2050, vehicle operation is projected to account for 85% of total transportation emissions, followed by vehicle manufacturing (7%), new road construction (4%), and road maintenance/rehabilitation and road roughness (approximately 2% each). While infrastructure-related emissions are relatively small compared to vehicle-related emissions, their impact remains significant. Reducing GHG emissions from Africa's road transportation infrastructure requires a comprehensive approach incorporating sustainable materials, efficient construction, and proactive maintenance. Low-carbon alternatives, renewable energy integration, and life cycle assessments in planning are key strategies.

Piles are designed to transfer superstructure loads using positive skin friction and tip resistance while undergoing acceptable settlements. However, when liquefaction-induced soil settlement occurs, it can drag the pile downward and result in negative skin friction and drag load. In such cases, estimating the drag load and pile settlement becomes important for pile design. A series of centrifuge model tests were performed to study liquefaction-induced downdrag on piles. The tests included four heavily instrumented piles installed in two different soil layered profiles with their tip embedment zero, three and five times their diameterin the dense sand. Loads on the piles were varied to study their effect on drag load and pile settlement. Results are presented describing the mechanism behind the development of liquefaction-induced downdrag, the magnitude of drag load, and pile settlement. Finally, recommendations are made for the design of piles in liquefiable soils