الفهرس 
Design optimization of prestressed concrete beamsOnly 14 pages are availabe for public view
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Abstract
• The influence of concrete cylinder compressive strength, strand diameter and girder span on the required number of pretension strands and total cost for Standard AASHTO PC-I, Standard AASHTO PC-Bulb Tee, NU I-Girder, Texas U-Beams and California Bath Tub section can be summarized as below:
1- Higher concrete cylinder compressive strength of 55 MPa comparing with concrete cylinder compressive strength of 40 MPa increasing the allowable tension stresses at service stage by 17 % leads to reduction in required number of strands of (8 % to 10 %) while increasing the cost by (4 % to 6 %).
2- Larger strand diameter of 15.2 mm about 20 % more than 12.7 mm strand provide 40 % higher tensile capacity of pretension strands leads to reduction in required number of strands of (25 % to 30 %).
3- Higher concrete compressive strength of 55 MPa and low relaxation strands of 15.2 mm comparing with concrete compressive strength of 40 MPa and low relaxation strands of 12.7 mm leads to reduction in required number of strands of (30 % to 35 %).
4- The total cost increases about (9 % to 12 %) for 3.0 m increase in girder span.
• The relation between girder span, minimum depth and cost for Standard AASHTO PC-I, Standard AASHTO PC-Bulb Tee and NU I-Girders can be summarized as below:
1- The minimum depth and cost for girder span range between (33.0 to 42.0) m is the Standard AASHTO PC-Bulb Tee Type BT63.
2- The minimum depth and cost for girder span range between (42.0 to 45.0) m is the Standard AASHTO PC-Bulb Tee Type BT72.
• The influence of cross-sectional area and moment of inertia on the required number of pretension strands and total cost for Standard AASHTO PC-I, Standard AASHTO PC-Bulb Tee and NU I-Girders can be summarized as below:
1- NU-1800 girder comparing with NU-1600 girder increasing the area and moment of inertia of the section by 5 % and 33 % respectively leads to reduction in the required number of strands of (15 % to 20 %).
2- NU-2000 comparing with NU-1800 increasing the area and moment of inertia of the section by 5 % and 29 % respectively leads to reduction in the required number of strands of (10 % to 15 %).
3- Standard AASHTO PC-I Type V comparing with Standard AASHTO PC-I Type IV increasing the area and moment of inertia of the section by 28 % and 100 % respectively leads to reduction in the required number of strands of (20 % to 25 %) increasing the cost by 5 %.
4- Standard AASHTO PC-I Type VI comparing with Standard AASHTO PC-I Type V increasing the area and moment of inertia of the section by 7 % and 40 % respectively leads to reduction in the required number of strands of (15 % to 20 %) increasing the cost by 5 %.
5- Standard AASHTO PC-Bulb Tee Type BT72 comparing with Standard AASHTO PC-Bulb Tee Type BT63 increasing the area and moment of inertia of the section by 7 % and 39 % respectively leads to reduction in the required number of strands of (15 % to 20 %) increasing the cost by 5 %.
6- Standard AASHTO PC-Bulb Tee Type BT63 and Type BT72 comparing with Standard AASHTO PC-I Type V and Type VI respectively decreasing the beam self-weight by 30 % leads to reduction in the required number of strands of (9 % to 12 %) decreasing the cost by 10 %.
• The influence of girder span and spacing on the minimum depth and cost for Standard AASHTO PC-I, Standard AASHTO PC-Bulb Tee, NU I-Girder, Texas U-Beams and California Bath Tub section can be summarized as below:
1- The minimum depth and cost for girder span range between (27.0 to 36.0) m at spacing of 3000 mm and girder span range between (24.0 to 33.0) m at spacing of 4500 mm is the Texas U-54.
2- The minimum depth and cost for girder span range between (36.0 to 39.0) m at spacing of 3000 mm is the CA TUB55.
3- The minimum depth and cost for girder span range between (39.0 to 45.0) m at spacing of 3000 mm and girder span range between (33.0 to 39.0) m at spacing of 4500 mm is the CA TUB61.
4- The minimum depth and cost for girder span range between (45.0 to 48.0) m at spacing of 3000 mm and girder span range between (42.0 to 45.0) m at spacing of 4500 mm is the CA TUB73.
5- Texas U-beams and California Bath TUB sections at spacing of 4500 mm comparing with spacing of 3000 mm leads to increasing the required number of strands of (35 % to 45 %) per girder and reduction of the total cost per square meter of 30 %.
6- CA TUB61 at spacing of 4500 mm comparing with Standard AASHTO PC-I Type V and NU I-Girder 1600 at spacing of 1820 mm leads to reduction in the total cost per square meter of 12 % and 15 % respectively.
7- CA TUB67 at spacing of 4500 mm comparing with NU I-Girder 1800 at spacing of 1820 mm leads to reduction in the total cost per square meter of 12 %.
8- CA TUB85 at spacing of 4500 mm comparing with NU I-Girder 2000 at spacing of 1820 mm leads to reduction in the total cost per square meter of 5 %.