tailieunhanh - Diesel Electric Generator Plants_4

Tham khảo tài liệu 'diesel electric generator plants_4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | MIL-HDBK-1003 11 Simpo PDF Merge and Split Unregistered Version - http machine characteristics which may be considered as approximate rather than precise. In many engineering problems which defy an exact analysis a safe design may be assured by the use of a greater factor of safety. In the field of machinery foundation design this approach may ensure structural adequacy but not necessarily dynamic stability. Normal differences between the predicted and actual characteristics of the soil and machinery may have adverse effect upon the characteristics which might destroy or wipe out expected design margins. The foundation characteristics may be further affected by deviations in actual construction from the details specified by the foundation designer. The designer should include provisions for field testing and adjustment of foundation mass in cases where design studies indicate a possible deficiency in design margins. This may be accomplished by making the bottom base slab extend outside the main foundation block. The dynamic stability may then be checked experimentally by placing bagged sand at various points around the unit upon the base slab extension while the engine-generator is operating. When optimum dynamic equilibrium is thus determined sand may be replaced with equivalent mass concrete anchored to the main foundation block and base slab extension. Minimum Requirements. Soil borings should extend no less than 50 ft 15 m below the bottom of unit foundations unless rock will be encountered at shallower depth. From these boring allowable soil bearing pressures engine-generator the need for piles can be determined. Foundation design should be governed by the following a The entire foundation bearing surface should be at the same elevation. Steps or cascades at support level should be avoided. b The unit foundation support level should be carried at least 30 in 762 mm below any trenches or basement floor levels which are adjacent to the