TEE Beam Manufacturing Analysis for Weight Reduction and Producibility

This report analyzes the manufacturing of tee shapes for stiffening ship structure. Tees produced by the traditional method of deflanging hot-rolled I-beams IT shapes have been compared to fabricated tee-shapes produced from plate for a target group of 1700 tees used in a DDG-51 class vessel. A review of design considerations for several structures has showed that weight savings averaging 18 were possible while still maintaining strength. To produce a DDG, flanges must be stripped from I-beams totaling more than 690 tons of 2240 pounds in weight, producing some 170 tons of scrap, a material loss of 25, easily in excess of 90,000. Given that weight and cost savings are possible by converting UT shapes to fabricated tees, an evaluation of methods to produce tee sections was undertaken. Both fabricating and stripping methods were considered, including newer technologies such as plasma cutting and laser cutting and welding. Mock-up testing was performed using several candidate technologies and the results compared. Plasma-arc cutting reduced distortion on forty-foot test beams by 50 compared to oxyfuel methods. Economic analysis revealed that fabricated tees were less costly to produce than deflanged I-beams, and that handling functions were the greatest cost element of the traditional oxyfuel cutting methodology.