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A bridge deck consists of 175 mm in cast-in-place acting compositely with precast pretensioned beams. Typical cross-section is shown in Fig. The bridge is 14 m simple span. Consider the following data: Live Load as shown below. Weight of curb parapet etc. = 1.46 kN/m per girder Precast concrete strength = 34.5 MPa ● Cas-in-place concrete strength = 24.8 MPa • Assume loss of prestress = 20% • Use Grade 270 prestressing strands (See Data Sheet Attached); unshored construction; double harp profile. • Use AASHTO girders Type II (See Data Sheet on Next Page) Finalize your design of a typical interior girder and show all relevant calculations. You must show: 1. Maximum (LL+ I) moment and shear envelope 2. Prestressing steel arrangement including profile with double harps 3. Ultimate strength check at the maximum moment location only. 4. Shear reinforcement arrangement and ties for horizontal shear transfer (Use shear friction method) 5. Neat sketches showing details, wherever applicable. You may make any appropriate assumptions. Roadway "asphalt 175 mm 50 mm ( "R/C slab 33.4 KN 133.5 kN 135 KN 4.25 m 4.25 m ne # (LL+1) Loading (moving) 2.45 m 2.45 m + 2.45 m +
II D1 900 Туре II D2 D41 D5 DG B2 Type II AASHTO Girder DIMENSIONS (Millimeters) D4 D6 0 75 150 150 300 450 150 Properties Y bottom (mm) Area (mm²) 230625 Inertia (mm) 1.99 x 10¹0 395.75 D2 D3 150 B1 B3 B4 ** D1 B6 -* B4 B5 75 Weight kN/m 5.6 0 150
Table 2.6 Wire for Prestressed Concrete Min. tensile strength (psi) Nominal diameter (in.) Type BA Type WA Type BA 0.192 250,000 0.196 240,000 250,000 204,000 0.250 240,000 240,000 204,000 0.276 235,000 235,000 199,750 Source: Post-Tensioning Institute Table 2.7 Seven-Wire Standard Strand for Prestressed Concrete Nominal diameter of strand (in.) Breaking strength of strand (min. lb) Nominal steel area of strand (sq in.) Nominal weight of strands (lb per 1000 ft)* GRADE 250 pupy=2 1 = 212 OR 225 (0.250) 9,000 0.036 122 7,650 (0.313) 14,500 0.058 197 12,300 (0.375) 20,000 0.080 272 17,000 (0.438 27,000 0.108 367 23,000 (0.500) 36,000 0.144 490 30,600 (0.600) 54,000 0.216 737 45,900 GRADE 270 Joy = OR 243 (0.375) 23,000 0.085 290 19,550 (0.438) 31,000 0.115 390 26,350 (0.500) 41,300 0.153 520 35,100 (0.600) 58,600 0.217 740 49,800 *100,000 psi = 689.5 MPa 0.1 in. = 2.54 mm; 1 in.² = 645 mm² weight: mult. by 1.49 to obtain weight in kg per 1,000 m. a fpy = 0.85 fpm Stress Releived 1,000 lb= 4,448 Newton Source: Post-Tensioning Institute Spy = 0.90 fou for low Relax. Min. stress at 1% extension (psi) =230 Type WA 212,500 212,500 204,000 199,750 Minimum load at 1% extension (lb) Table 2.8 Seven-Wire Compacted Strand for Prestressed Concrete [ASTM A779] Nominal Nominal Nominal weight of strand Nominal diameter (in.) Breaking strength of strand (min. lb)* steel area (in.²) (per 1,000 ft-lb) 1 47,000 0.174 600 0.6 67,440 0.256 873 0.7 85,430 0.346 *1000 lb-4,448 Newton Grade 270; fp=270,000 psi ult. strength (1,862 MPa) 1 in. = 25.4 mm; 1 in.²= 645 mm² 1176 £₁ =0.85fpm