Perforated Plunge Column Piles

Plunge piles are heavy steel column sections plunged into preformed fluid concrete piles. There is uncertainty about the bond between the steel and concrete. Consequently, projecting shear connectors or conservative bond design stresses are used to ensure safety. The research used perforated steel sections with holes cut in the web and/or flanges to increase shear connection rather than conventional shear connectors welded on perpendicular to the shear surface. The local bearing achieved by various perforations was measured using 203x203mm UC46 steel sections, pre-coated with bitumen to prevent the development of bond, placed lm into reinforced concrete pile columns on a soft pocket. Deflections of 4mm+ were necessary to build up bearing resistance at perforations, whereas on uncoated unperforated sections deflections of less than 1mm developed bond resistance which peaked and then fell significantly. The combination of the two effects dependedon therate of loss of conventional bond post peak. The study indicated that (subject to further te sting) the method was economic and efficient where bond was important.