Three Dimensional Grillage Analysis of Reactions on Supports of a Pre-Erection Block

There are many PE(Pre-Erection) Blocks in open areas of the shipyard, which are supported by the wooden, concrete, or steel supports. Their position and numbers are decided on a basis of the workers’ experiences. Recently, many shipyards have been making PE blocks with various shape and weight distribution because of the variety of kinds of ships and their building technology. Seriously, they are treating blocks which have not been experienced. In order to evaluate the reliability of all support plans of PE Blocks in such situation, many man hours (MH) are consumed, and the special knowledge and technology about structural analysis are required. We proposed how to conveniently and quickly evaluate the structural safety on PE block supports and developed an application system to implement the evaluation process with three dimensional part models of the PE block and their weight information. The evaluation is based on the simplification to a grillage model of a PE block and its grillage analysis. The load distribution on the grillage model is calculated by two approaches. The first is that the load distribution on the grillage nodes are estimated with the real weight and the center of gravity of each part of a PE block, which can be provided from design databases of the shipyard. The other is that the load distribution is optimally estimated only with the weight and the center of gravity of sub blocks of a PE block. The latter is useful in the case that block information of mother ships can be obtained without the detail design of the PE block. The integrated system has been comprehensively implemented in order to make the grillage model from the three dimensional CAD models of the PE block and their weight information, and to perform the grillage analysis for the reaction forces on the block supports. In the application program, the grillage model can be automatically built from CAD models of PE block. Also the grillage can be modified by inserting, splitting, and deleting a beam element.