5 Horizontal Stringer Heel

5.1 Design standard I

5.1.1

The horizontal stringer heel location between transverse oil-tight/swash bulkhead plating and inner hull longitudinal bulkhead plating for double hull oil tankers are required to be designed according to design standard I, as shown in Table 9.

Table 9 : Design Standard I – transverse bulkhead horizontal stringer heel

Connections of horizontal stringer on plane oil-tight transverse bulkheads or wash bulkheads to inner hull longitudinal bulkheads
Critical areas	Design standard I

Critical locations

	Note 1: Where a face plate is considered necessary, it is recommended that design features be adopted to reduce the stress concentration at the face plate termination (e.g. taper and soft nose). Adequate fatigue life of the weld on the bracket edge in way of such terminations is to be confirmed. Note 2: ‘Slit type cut-outs are to be adopted in way of the bracket toe as shown. Alternatively, cut-outs with insert type collars will be accepted. Scallops are to be avoided.’
Critical location	Intersections of webs of transverse bulkhead horizontal stringer and double side tank side stringer forming square corners.
Detail design standard	A soft toe backing bracket is to be fitted. The following bracket sizes are recommended: VLCC: 800×800×30, R600 with soft toe as shown in figure above, Other tankers: 800×600×25, R550 with soft toe as shown in figure above, where the longer arm length is in way of the inner skin. The specified minimum yield stress for the bracket is not to be less than 315 N/mm². The free edge is to be ground smooth with corners rounded.
Building tolerances	The nominal distance between the centres of thickness of the two abutting members should not exceed 1/3 of the as-built plate thickness of the inner hull longitudinal bulkhead.
Welding requirements	Vertical weld between the inner hull plating and transverse bulkhead plating, fillet welding having minimum weld factor 0.44. Welding between the backing bracket and the adjoining plates is to be double sided fillet welding having minimum weld factor 0.44 except in way of the bracket toes. Full penetration welding is to be used for the connection of bracket toes to the inner hull and transverse bulkhead plating for a distance of 200 mm from the toes and the weld toes are to be ground smooth in way.