Extracted text: PROBLEM. The joist (double tee) is to be used on a simply supported span of 8-m and is pre- tensioned with an initial force of 1,240 kN from low-relaxation strands. The centroid of the strands is located at 220-mm below the neutral axis of the DT throughout the beam span. Loss of prestress of service loads is 20%. Total uniformly distributed loads on the joists are: Dead Load = 4.5 kPa (beam weight included) and Live Load = 3.6 kPa. Compute the resulting stress at bottom fibers at DT at midspan due to service loads and prestress force. Section properties of the double tee joists (DT) shown as follows: . а 3 2.4 m • Yt = 103 mm . Уь %3D 303 mn • A = 2.1 x 105 mm2 | = 2.76 x 109 mm4 Concrete unit weight = 24 kN/m3 %3D a=2.4 m N.A.