Structural Requirements For Hydropower Plant Design

Design Stresses

Allowable stresses will depend on the materials involved, the conditions of loading, and severity of exposure.

1. Allowable stresses.

Structural steel and welded joints should be designed in accordance with the allowable stresses outlined in the latest version of the AISC construction manual. Welding details should be as outlined by the latest version of AWS D1.1. Gates, Bulkheads, Trashracks, and associated guides should be designed using the allowable stresses outlined in EM 1110-1-2102.

2. Concrete structures.

 Concrete structures loaded hydraulically should be designed in accordance with the procedures outlined in EM 1110-2-2104 “Strength Design for Reinforced Concrete Hydraulic Structures.” Those portions of a powerhouse that will not have water loading, such as the superstructure, may be designed in accordance with the latest version of ACI 318.

Design Loads

 a. General considerations.

The structures should be designed to sustain the maximum dead, live, hydrostatic, wind, or earthquake loads which may be imposed upon them. Where only partial installation is to be made under the initial construction program, consideration should be given to the temporary loading conditions as well as those anticipated for the completed structures. The stability of all powerhouse monoliths should be investigated for all stages of construction; and loads that may be imposed or absent during the construction period should be accounted for in the design memoranda.

 b. Dead loads.

Dead loads to be considered in the design consist of the weight of the structure itself, including the walls, floors, partitions, roofs, and all other permanent construction and fixed equipment. The approximate unit weights of materials commonly used in construction can be found in the AISC Manual. A check should be made of the actual weights where a variation might affect the adequacy of the design, or in cases where the construction may vary from normal practice.

c. Live loads.

In general, floors are designed for an assumed uniform load per square foot of floor area. However, the floors should be investigated for the effects of any concentrated load, minus the uniform load, over the area occupied. Equipment loads should take into account installation, erection, and maintenance conditions as well as impact and vibration after installation. In most cases, it will be necessary to proceed with the design on the basis of estimated loads and loaded areas until such time as the actual data are available from the manufacturers.

All live loads used in design should be recorded with notations as to whether the loads are actual or assumed. Estimates of the weights of the machines should always be requested from the manufacturers for preliminary use in the design. Assumed loads should be checked later against actual loads, and, where differences are appreciable, the necessary modifications in the design should be made.