A COMPARATIVE ANALYSIS OF FOUNDATIONS USING PRESCRIPTIVE DESIGN AND STATIC LOADING TEST METHODS

Most foundations are designed to support mainly compressive loads from the superstructure. However, for some structures such as power transmission lattice towers, ferry berthing structures, and jetty structures subjected to overturning loads imposed by winds and impact, the foundation structures are required to resist uplift, compression and/or lateral forces which are much greater than the weight of the structure itself. In addition to the overturning loads imposed by winds, transmission line towers are hit by line tensions. Since, the transmission lattice tower foundation structure is required to mostly resist uplift, compression and/or lateral forces, the corresponding capacities of the buried foundation bases essentially come from the weight of the soil within the failure zone above the base, the frictional resistance along the failure surface, and the self-weight of the foundation. Thus, the required pull-out resistance is normally achieved by increasing base area of the foundation and the depth of embedment. Since foundation stability is critical to superstructure safety and for avoidance of unacceptable failures, foundation load testing through the static uplift, compression and/or lateral load methods, is necessary to assess the direct measurement of the foundation’s head displacements in response to a physically applied test load until its failure point to replicate the insitu long-term sustained loading conditions. This research therefore, involves carrying out a comparative analysis of foundations using prescriptive design and static loading test methods with a case study of transmission lattice tower foundations at the Karuma Interconnection Project