Civil Engineering Reference
In-Depth Information
Figure 6.1
Cambering.
Camber
The deflection of reinforced concrete members may also be controlled by cambering. The
members are constructed of such a shape that they will assume their theoretical shape
under some service loading condition (usually dead load and perhaps some part of the live
load). A simple beam would be constructed with a slight convex bend so that under cer-
tain gravity loads it would become straight as assumed in the calculations. (See Figure
6.1.) Some designers take into account both dead and full live loads in figuring the
amount of camber. Camber is generally used only for longer-span members.
6.4
CALCULATION OF DEFLECTIONS
Deflections for reinforced concrete members can be calculated with the usual deflec-
tion expressions, several of which are shown in Figure 6.2. A few comments should be
made about the magnitudes of deflections in concrete members as determined by the
expressions given in this figure. It can be seen that the
C
L
deflection of a uniformly
loaded simple beam [Figure 6.2(a)] is five times as large as the
C
L
deflection of the
same beam if its ends are fixed [Figure 6.2(b)]. Nearly all concrete beams and slabs
are continuous, and their deflections fall somewhere between the two extremes men-
tioned here.
Figure 6.2(a)
Some deflection
expressions.
