18 – Bulkheads and pillars

Publisher Summary This chapter deals with the internal vertical structure of the ship. Much of this structure, particularly the pillars and to some extent the transverse strength bulkheads, is responsible for carrying the vertical loading experienced by the ship. The chapter discusses the construction and spacing of the bulkheads that subdivide the ship hull into a number of large watertight compartments. Vertical partitions in a ship arranged transversely or fore and aft are referred to as “bulkheads”. The bulkheads that are of greatest importance are the main hull transverse and the longitudinal bulkheads dividing the ship into a number of watertight compartments. Other lighter bulkheads, named “minor bulkheads”, which act as screens further subdividing compartments into small units of accommodation or stores, are of little structural importance. In vertical structure, pillar also performs the important function. The prime function of the pillars is to carry the load of the decks and weights upon the decks vertically down to the ship's bottom structure where these loads are supported by the upward buoyant forces. A secondary function of pillars is to tie together the structure in a vertical direction. Within the main hull of a cargo ship, two different forms of pillars may be found—those in the holds invariably fulfilling the first function, and those in the machinery spaces fulfilling the latter function. Hold pillars primarily in compression are often without bracket connections at their ends, while machinery space pillars are heavily bracketed at their ends to permit tensile loadings. This latter type of pillar may also be found in tank spaces where the crown of tank under pressure can put the pillar in tension.