A post-tensioned prestressed concrete roof deck is to be designed using 8-ft width single-T beams spanning 70 ft between simple supports. Service loads include live load of 704 plf, superimposed dead load of 80 plf, and estimated self-weight of 600 plf. Normal weight concrete is used with specified compressive strength of 5000 psi and strength at time of transfer of 3500 psi. The prestressing force will be provided using 1/2-in. diameter Grade 270 low relaxation strands with fpu=270 ksi and fpy=243 ksi and maximum eccentricity at the midspan. The prestress residual ratio can be assumed to be 0.85. If a section is selected as shown below, and the designer provided the beam with sixteen strands, the beam is ) (2 نقطة) 30 1.5 168917 in A570 49.99 26.01 in Sc=6899 S2650 p? 120.9 in e 22.51 Wy594 ply Filememil the n71 Not satisfactory and larger section should be used A constant eccentricity has to be used SA Satisfactory and can be used The maximum eccentricity has to be reduced