THE “NO FRAME” CONCEPT —IT'S IMPACT ON SHIPYARD COST

Abstract

ABSTRACTA proposed cost effective alternative to current U.S. Navy structurally configured hulls is presented in this paper. This proposed design for producibility concept involves the elimination of structural stanchions and transverse web frames. The potential impact of this “no frame” concept on structural design, weight and construction and material costs for naval surface frigates and destroyers is reflected in 1) reduced costs for the installation of distributive systems and 2) a reduced number and complexity of structural details providing a more reliable and less costly structure.This study was performed in three parts: 1) Determine the most feasible length between bulkheads without frames; 2) Using this length perform detail weight studies and construction and material costs analysis comparison on a 72‐foot long hull module, with and without frames, for a FFG‐7, and 3) Estimate the saving in man hours of labor on the installation of distributive systems and shipfitting for an FFG‐7.For the feasible length studies on the “no frame” structural configuration, thirty‐seven strength, weight and vertical center of gravity studies were performed on two ship classes; twenty‐two on the FFG‐7 class and fifteen on the DD‐963 class. The detailed weight studies and construction and material cost analyses were conducted for FFG‐7 “no frame” and “as built” modules. Results indicating the “no frame” concept module was 6.8% heavier and 14.8% less costly than the “as built” module.For the impact of an FFG‐7 “no frame” structurally configured hull on the cost of labor required for the installation of distributive systems and for other functional work such as ship fitting, welding, and electrical, this study indicated a reduction of 169,206 labor hours per ship, representing 7.12% of the total required man hours to fabricate an FFG‐7 class ship.With the employment of the “no frame” concept, certain areas of significant concern and potential risk were addressed. These include: 1) the actual impact on structural weight and cost, 2) the actual impact on the installation of distributive systems and on other functional systems, 3) effects on a typical opening in a “no frame” structurally configured deck, 4) secondary (hydrostatic) load induced bending moments and shear forces at longitudinal beam and transverse bulkhead intersections, and 5) the vibrational response of a “no frame” structurally configured deck.