Full Scale Load Test On Moor Ing Platform

Abstract

A full scale test, horizontal load test, and measurement of micro tremors were conducted on a sea berth mooring platform with 4 legs, 15.5 meters high, installed at a water depth of 11.0 meters. In the horizontal load test, the platform was checked for deformation and strain. The micro tremors of the platform were recorded and their frequency analyzed. The platform was designed and statically analyzed by using MARINE JAST, a jacket structure analysis program developed by Kawasaki Steel, and NASTRAN, a general purposes program used for its dynamic analysis. First, the mechanism of stress transmission from the jacket to the piles under the horizontal load was assumed, and analysis model was set up. The calculated stresses of legs, braces, and piles were compared with their observed values. The calculated eigenvalues of the platform were also compared with their observed values. The following conclusions were drawn from these tests. (1) Horizontal displacement of the platform crown largely depends on the axial spring constant of the piles. (2) The legs and piles connected by expansive mortar are assumed to behave nearly as one member. The calculated axial forces of the legs and piles agreed with the observed values except for the decrease of the axial forces of the piles in the stratum due to skin friction. The calculated axial forces of the braces and bending moment of the piles were slightly larger than their observed values, respectively. (3) The low order natural vibration modes of the platform were rocking, torsional, vertical, and sway vibration in this order. The calculated natural frequencies of the rocking and torsion agreed well with their observed values.