Conversion from Ultimate Limit State to Serviceability Limit State for Foundation Design: Critique of Current Practice and Codes/Standards
Audu Isa Ibrahim Dakas & Akolo Peter Enjugu
Department of Building, Faculty of Environmental Sciences
University of Jos, Jos
Email: abdullahidakas@gmail.com
Corresponding Author: Audu Isa Ibrahim Dakas
ABSTRACT
The adoption and utilisation of ultimate loads for serviceability limit state conditions in foundation design has become a practice due to the cumbersome and time consuming processes and procedures for load computation and estimation. This practice has resulted in safe but uneconomic foundation designs since large values of loads imply increased base areas of footings or number of piles for such building foundation stability. However, for safe and economic designs of foundations, the need for the conversion of ultimate limit loads to serviceability limit state conditions is important. To address that, this paper reviews the extant literature and body of knowledge to understand the extent of practice and documentation. It is revealed that some available conversion factors have been identified and detailed. Also, previous and recent developments on this fundamental design parameter have been summarised and highlighted, including the extent of application of this parameter. These show gross shortcomings in the conversion of ultimate limit state loads to serviceability limit state loads. Therefore, until appropriate conversion factors that are applicable and acceptable are evolved, to aid speedy conversion of loads aggregated at the ultimate limit state to service loads, the implication is continuous uneconomic foundation designs at the expense of building clients.
Keywords: foundation design, conversion factors, ultimate loads, serviceability loads, codes of practice
