F. K. Kong MA, MSc, PhD, CEng, FICE, FIStructE, R. H. Evans CBE, DSc, D ès Sc, DTech, PhD, CEng, FICE, FIMechE, FIStructE (auth.)-Reinforced and Prestressed Concrete-Springer US (1987)

Primary and secondary moments 381
A~-~~---1.
(c} Deflection due to primary moment
p--·-·=?j
A JA; B
RA t Rc Ra
(d) Reactions to restrain support deflections
~
a b
(e} Diagram of secondary moment M2 (abc)
Diagram of resulting moment M3 {as shaded)
.fS?fr=-7--t(·::'j.
Tendon profile e.-ep'"'M:z/P.
(f) Deviation of line of pressure from tendon profile
Fig. 10.1-1
the beam, then the local value of Pc should be used in this equation.) The
line having the eccentricity eP is called the line of pressure or the line of
thrust (Fig. 10.1-l(f) ); it represents the locus of the centre of compression
in the concrete section. In a simple beam, of course, no secondary
moments exist and the tendon profile is the line of pressure.
In applying eqns (9.2-2) and (9.2-3) to continuous beams, the tendon
eccentricity e, must be replaced by the eccentricity eP of the line of
pressure:
(10.1-3)