- 5 1 A Post Tensioned Bonded Prestressed Beam Has The Cross Section Shown In Figure P5 1 It Has A Span Of 75 Ft 22 9 M 1 (32.42 KiB) Viewed 54 times
- 5 1 A Post Tensioned Bonded Prestressed Beam Has The Cross Section Shown In Figure P5 1 It Has A Span Of 75 Ft 22 9 M 2 (27.03 KiB) Viewed 54 times
A4 PAGES
YOU WILL HAVE TO SOLVE IT BY BOTH METHODS ASKED IN THE
QUESTION THAT IS (A) DETAILED DESIGN METHOD (B) ALTERNATIVE
METHOD
5.1 A post-tensioned bonded prestressed beam has the cross section shown in Figure P5.1. It has a span of 75 ft (22.9 m) and is subjected to a service superimposed dead load Wsp=450 plf (6.6 kN/m) and a superimposed service live load W₁ = 2,300 plf (33.6 kN/m). Design the web reinforcement neces- sary to prevent shear cracking (a) by the detailed design method and (b) by the alternative method at a section 15 ft (4.6 m) from the face of the support. The profile of the prestressing tendon is par- abolic. Use #3 stirrups in your design, and detail the section. The following data are given: A = 876 in.² (5,652 cm²) I = 433,350 in.* (18.03 x 10 cm¹) = 495 in.² (3,194 cm²) 48" (122 cm) Act Go t 18" (46 cm) #7" 3" 39" (99 cm)
c, = 25 in. (63.5 cm) S = 17,300 in.³ (2.83 x 10³ cm³) 38 in. (96.5 cm) сь = S 11,400 in.³ (1.86 x 105 cm³) = Wa = 910 plf (13.3 kN/m) ec = 32 in. (81.3 cm) e = 2 in. (5 cm) f = 5,000 psi (44.5 MPa), normal-weight concrete f = 3,500 psi (24.1 MPa) fy for stirrups = 60,000 psi (41.8 MPa) fp = 270,000 psi (1,862 MPa) low-relaxation strands fps = 243,000 psi (1,675 MPa) fpe = 157,500 psi (1,086 MPa) Aps = twenty-four-in. dia (12.7 mm dia) 7-wire tendons 5.2 Find the shear strengths V, V, and Vw for the beam in Problem 5.1 at 1/10 span intervals along the entire span, and plot the variations in their values along the span in a manner similar to the plot in Figure 5.13.