15 August 2002
Loads on Pumpwell Overhead and Floors. Pumpwell overhead should
be designed for a uniform load of 2929 kg/m2 (600 lb/ft2) and for truck crane wheel
loading when it is at ground level. The critical load for floors supporting main pumps
usually corresponds to the maximum upward pressure. Use a uniform load of 1464
kg/m2 (300 lb/ft2) for floors not subject to upward hydrostatic pressure; also these floors
are to sustain loads from operating machinery placed thereon either in a permanent
operating position or in a temporary overhaul position. Include vibrations induced by
reciprocating and rotating equipment in the design.
Earthquake Forces. In regions of earthquake probability use design
criteria contained in MIL-HDBK 1025/1 Piers and Wharves. A drydocking facility is a
major capital investment and, therefore, the structural system will be subject to a
rigorous dynamic analysis of seismic probability effects in accordance with well-
established principles of mechanics. Design the drydock to resist the forces of two-
thirds of the site adjusted Maximum Considered Earthquake (MCE). The MCE is an
earthquake with an acceleration equivalent to an earthquake having a 2 percent
probability of exceedance in 50 years. Site adjustments are based on the
characteristics of the soil underlying the site. Design lateral acceleration should be at
Bomb and Blast Resistance
. Drydocks are not usually designed
resist bombing or blast effects because of the massive size of the structure involved. In
some locations, consideration should be given to protective construction for the upper
part of the pumpwell and the service tunnels. Additional guidance for Anti-
terrorism/Force Protection is contained in MIL-HDBK 1025/1 Piers and Wharves.
SPECIAL CONDITIONS OF LOADING
Full Hydrostatic Drydocks. Although there are many special loading
conditions to be considered in the design of a graving dock (for example,
nonsymmetrical loads, wave action on exposed walls, earthquake, and unusual water
differentials), the design of full hydrostatic pressure docks generally is concerned with
four especially critical conditions.
Case I. Dock under construction.
Case II. Dock empty. Maximum hydrostatic uplift.
Case III. Maximum ship load. Minimum hydrostatic uplift.
Case IV. Dock full of water.
For application of these loadings, refer to American Civil Engineering
Practice, Volume II.
Partially and Fully Relieved Drydocks. Critical conditions for partially
and fully relieved designs are similar to those for full hydrostatic drydocks, except for