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)

184 Reinforced concrete beams-the serviceability limit states
MP, the midspan moment due to the permanent load,
= (57·6)(5) = 36 kNm
8
From Table 2.5-6,
Ec (short term) = 28 kN/mm 2
From eqn (5.5-3),
Ec (long term) = 1 ] 8 2.5 = 8 kN/mm 2
The calculations for the deflection are carried out in the following steps.
Step I
From Example 5.2-2(c),
1 1 Mt- Mp
rit - Tip = Eclc
and this was found to be (1.30)(10-6).
Step2
From Example 5.2-2(a),
_!_ = (5.57)(10-6)
TJp
Step3
_!_ + (j_ - _!_) = (5.57)(10-6) + (1.30)(10-6)
TJp Tit rip
= (6.87)(10-6)
Step4
From eqn (5.5-6),
1 EcsaeSs
Yes=-~-
Ecs = 0.0003
(200)(106)
ae = Esl Eeff = (8)(106) = 25
From Example 5.2-2 (a),
Hence
x = 171 mm; Ic = (763)(106) mm 4
Ss = A 5(d- x)
= (628)(340 - 171) = (106.1)(1cP) mm 3
_!_ = (0.0003)(25)(106.1)(1cP) = (1 04)(10-6)
r cs (763)(106) ·