ANALYTICAL STUDY OF OFFSHORE COMPLEX STRUCTURES

Abstract

In this research the assessment procedure and mitigation actions are studied in two existing platforms to know how these mitigation procedures and factors can affect the collapse behavior and this will be a guide for the offshore structure engineers. As SAP2000 version 11 has included recently the offshore module so some of verifications has been done on this module to know the possibility of using SAP2000 in design offshore structure as follows: A cantilever (24"x0.5 was analyzed using SACS and SAP2000 , the cantilever is at mud-line elevation (-15 m) and extended 5m above water level and both models was subjected 5.5 m wave height ,wave period 3 seconds , two case were considered in the analysis o Case 1 the member is flooded under water surface o Case 2 the member is non flooded under water surface For both cases the wave velocities and accelerations are approximately the same also the base shear reactions and straining actions on the cantilevers due to wave loading for Case 1 and Case 2, in Case 2  it was found there is a difference 5% between the vertical reaction in SACS and SAP2000 however there is a difference in the criteria as SACS do not account the buoyancy above the sea-level which considered the half of the wave height during the wave loading condition however SAP2000 had consider that portion in the calculation of the buoyancy loads. A jacket of a platform was analyzed using SACS and SAP2000 , the jacket was subjected to wave height 14 m and wave period equals to 3 seconds , all jacket legs are considered flooded, the horizontal and vertical braces are considered non flooded , the jacket was analyzed using three different wave theory Airy wave theory , stoke wave theory for SACS and SAP 2000 and no-linear wave theory ( Stream function) for SACS only ( this theory is not supported in SAP2000).  The results revealed that the wave velocities and wave accelerations are approximately the same for the three wave theories .