The piles for an integral abutment bridge are subjected to horizontal movements caused by the expansion and contraction of the bridge superstructure. To design the abutment piles properly, a rational design approach was developed to simplify the complex behaviour associated with pile and soil interaction. Fundamental principles for two pile design alternatives that were formulated in a recently completed research study involving experimental and analytical investigations are presented. Alternative 1 was based on elastic behaviour and is recommended for piles with limited ductility, such as timber, concrete, and steel sections having insufficient moment-rotation capacity. Alternative 2 was based on inelastic behaviour involving plastic redistribution of internal forces caused by the lateral displacement of the pile head and is recommended for piles with adequate moment-rotation capacity at plastic hinge locations. Steel piles do not have to be classified as compact sections to meet the moment-rotation requirement. A ductility criterion, expressed in terms of lateral pile head displacement, is given to evaluate whether the moment-rotation capacity of an HP-shaped pile exceeds the moment rotation demand. To illustrate both design alternatives, a design example for a steel, HP-shaped, friction pile is presented. For the specific example, Alternative 2 is shown to permit the safe design of integral abutment bridges that are substantially longer than those designed according to Alternative 1.
Samenvatting