Dead Loads CE 213

Dead Loads. Dead loads consist of the weights of the various

structural members and the weights of any objects that are permanently

attached to the structure. Hence, for a building, the dead loads include

the weights of the columns, beams, and girders, the floor slab, roofing,

walls, windows, plumbing, electrical fixtures, and other miscellaneous

attachments.

In some cases, a structural dead load can be estimated satisfactorily

from simple formulas based on the weights and sizes of similar

structures. Through experience one can also derive a “feeling” for the

magnitude of these loadings. For example, the average weight for timber

buildings is for steel framed buildings it is

and for reinforced concrete buildings it is

Ordinarily, though, once the materials

and sizes of the various components of the structure are determined,

their weights can be found from tables that list their densities.

The densities of typical materials used in construction are listed in

Table 1–2, and a portion of a table listing the weights of typical building

110–130 lb>ft2 15.3–6.2 kN>m22.

60–75 lb>ft2 12.9–3.6 kN>m22,

40–50 lb>ft2 11.9–2.4 kN>m22

TABLE 1–2 Minimum Densities for Design Loads

from Materials*

lbft3 kNm3

Aluminum 170 26.7

Concrete, plain cinder 108 17.0

Concrete, plain stone 144 22.6

Concrete, reinforced cinder 111 17.4

Concrete, reinforced stone 150 23.6

Clay, dry 63 9.9

Clay, damp 110 17.3

Sand and gravel, dry, loose 100 15.7

Sand and gravel, wet 120 18.9

Masonry, lightweight solid concrete 105 16.5

Masonry, normal weight 135 21.2

Plywood 36 5.7

Steel, cold-drawn 492 77.3

Wood, Douglas Fir 34 5.3

Wood, Southern Pine 37 5.8

Wood, spruce 29 4.5

components is given in Table 1–3. Although calculation of dead loads

based on the use of tabulated data is rather straightforward, it should be

realized that in many respects these loads will have to be estimated in

the initial phase of design. These estimates include nonstructural

materials such as prefabricated facade panels, electrical and plumbing

systems, etc. Furthermore, even if the material is specified, the unit

weights of elements reported in codes may vary from those given by

manufacturers, and later use of the building may include some changes

in dead loading. As a result, estimates of dead loadings can be in error by

15% to 20% or more.

Normally, the dead load is not large compared to the design load for

simple structures such as a beam or a single-story frame; however, for

multistory buildings it is important to have an accurate accounting of all

the dead loads in order to properly design the columns, especially for the

lower floors.