3.1

.1

GENERAL

The functional design of buildings housing power plants and pumping plants is discussed in Chapter 1 of Power Systems (Design Supplement No. 4). The structural design of concrete buildings housing power plants and pumping plants, as well as concrete buildings serving other purposes, is discussed in this chapter. Reinforced-concrete design standards applicable to all design. are given in Chapter 2 of General Design Standards (Design Supplement No. 1). .2 Heavily reinforced-concrete structures include power plants and large pumping plants whose principal function is the housing of the large units and auxiliary equipment and sustaining the heavy loads encountered in this type of installation. The equipment, installation, and maintenance loads placed on these structures, particularly the major plants, require massive rigid construction with heavy reinforcement in order to safely transfer the loads to the foundations within the limit of permissible deflection. Structures are classified as major or minor, as follows:

.3

The larger structures are classified as major plants when the length of
the building is so great that transverse expansion joints are required. In
general, this type of plant has an expansion joint between each generating
or pump unit. Typical major plants include Hoover, Shasta, Grand Coulee,
and Hungry Horse power plants, and Grand Coulee and Tracy pumping
plants.

B. If the length of the plant is not more than approximately 150 feet, no
transverse expansion joint is usually required and the structure is termed
a minor plant.

Medium and lightly reinforced-concrete structures constitute the permanent miscellaneous structures required at the site of a large dam such as machine shops, switchyard control buildings, switchyard foundations, sewage treatment plants, cable ducts, office and administration buildings, vista houses, and the smaller pumping plants and relift stations. Nominal loads, simple foundation conditions, and symmetrical framing permit comparatively thin sections and the repetition of design. As a result, the successful behavior of structures of this kind is often primarily dependent on attention to shrinkage and temperature reinforcement and good reinforcement details.

STRUCTURAL ANALYSIS

.4 Practically all reinforced-concrete buildings constructed by the Bureau are designed as elastic-framed structures with consideration of the continuity or monolithic character of this type of construction. This feature of continuity complicates the problem of determination of the amount of bending, shear, and thrust at critical sections of the frame. The basic assumptions, in general, follow those given in the Joint Committee Specifications (see Chapter 1, General Structural Design Procedures and Standards).

A.

B.

For purposes of computing the stiffness of flexural members of a frame,
the moment of inertia is usually assumed as that of the basic rectangular
section, that is, bd3/12. This applies to both beams and columns even
though these members are continuous with slabs or walls. The effect of
reversal of stress due to lateral loads and moving loads, generally makes
it advisable to consider only the rectangular portion of the element,
neglecting the effect of the wall or slab.

In frame analysis, the length of horizontal members should, in general, be
taken as the center-to-center distance between column lines, and the
length of columns should be taken as the center-to-center distance between
beams. Where beams frame into massive concrete supports, the clear-
span length plus the depth of beam should be used as the beam length. A
similar assumption should be made for deep beams and slender columns;

REFERENCES

HEAVILY REINFORCED STRUCTURES

Major Plants

Minor Plants

MEDIUM
&
LIGHTLY
REINFORCED
STRUCTURES

METHODS
&

ASSUMP-
TIONS

Moments of
Inertia

Lengths of
Members