Design a prestressed concrete, post-tensioned, I girder for a bridge span of 25 metres. The loading...

 

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Design a prestressed concrete, post-tensioned, I girder for a bridge span of 25 metres. The loading per beam on the bridge is 15 kN/m plus an allowance of 30% for impact. (making a live load of 19.5kN/m.) In addition to the live load and self weight, an additional dead-load from the deck and barriers is a loading of 15 kN/m. From the two possible bridge girders as given in Figure 1 (a) or (b), choose a suitable girder. Design the beam and prestressing such that no tension exists under any loading condition, and the maximum compressive stress is limited to 40% of the concrete stength at initial prestressing (stressed at concrete strength 35MPa) and 0.4 f'c at full design loading. Take f'c = 40 MPa. Design for ultimate flexural strength Consider prestress losses in your design. Design the anchorage end block for your choice of prestressing force and end anchorage arrangement. Assume the end block dimensions as illustrated in Fig. 2. 1,100 425 500 150 (a) 100 140 540 L 150 1,400 475 Fig 1 Possible l am sections. 625 (b) 150 150 165 625 240 + 175 Fig 2 End block Illustra Marks will be awarded for accuracy of calculation, and presentation of design diagrams. Make any appropriate assumptions as necessary. For consistency use VSL data in the design. Shear design is not required. Design a prestressed concrete, post-tensioned, I girder for a bridge span of 25 metres. The loading per beam on the bridge is 15 kN/m plus an allowance of 30% for impact. (making a live load of 19.5kN/m.) In addition to the live load and self weight, an additional dead-load from the deck and barriers is a loading of 15 kN/m. From the two possible bridge girders as given in Figure 1 (a) or (b), choose a suitable girder. Design the beam and prestressing such that no tension exists under any loading condition, and the maximum compressive stress is limited to 40% of the concrete stength at initial prestressing (stressed at concrete strength 35MPa) and 0.4 f'c at full design loading. Take f'c = 40 MPa. Design for ultimate flexural strength Consider prestress losses in your design. Design the anchorage end block for your choice of prestressing force and end anchorage arrangement. Assume the end block dimensions as illustrated in Fig. 2. 1,100 425 500 150 (a) 100 140 540 L 150 1,400 475 Fig 1 Possible l am sections. 625 (b) 150 150 165 625 240 + 175 Fig 2 End block Illustra Marks will be awarded for accuracy of calculation, and presentation of design diagrams. Make any appropriate assumptions as necessary. For consistency use VSL data in the design. Shear design is not required.