Externally Prestressed Members: Evaluation of Second-Order Effects
Publication: Journal of Structural Engineering
Volume 125, Issue 10
Abstract
This paper presents the results of analytical investigation of the strength and structural behavior of concrete members prestressed with external tendons. The behavior at both the serviceability and ultimate limit states is evaluated. A nonlinear analysis model, based on the incremental deformation method, is developed to predict the entire response of concrete members originally designed with or strengthened by external prestressing. The proposed analysis reproduced experimental results of deflection and tendon stress responses with remarkable accuracy. A parametric study was undertaken to evaluate the behavior of concrete beams either designed using external prestressing or strengthened by it. The analytical results demonstrated that the second-order effect, associated with the progressive change in eccentricity of the tendons with increasing member deformation, is the main factor that distinguishes the behavior of external tendon from an internal unbonded tendon system. Because of this effect, undeviated external tendons mobilized lower nominal flexural resistance and inelastic deflections than did deviated tendons. When used for strengthening concrete flexural members, providing a moderate amount of external prestressing steel leads to significant deflection recovery, some reduction in the live load deflection, and a substantial increase in the yield load and ultimate flexural capacity of the members.
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References
1.
Alkhairi, F. M. ( 1991). “On the flexural strength of concrete beams prestressed with unbonded internal and external tendons,” PhD dissertation, University of Michigan, Ann Arbor, Mich.
2.
Alkhairi, F. M., and Naaman, A. E. (1993). “Analysis of beams prestressed with unbonded internal or external tendons.”J. Struct. Engrg., ASCE, 119(9), 2680–2700.
3.
“Building code requirements for reinforced concrete.” (1995). ACI 318-95, American Concrete Institute, Detroit.
4.
Harajli, M. H. (1990). “Effect of span-depth ratio on the ultimate steel stress in unbonded prestressed concrete members.” ACI Struct. J., 87(3), 205–312.
5.
Harajli, M. H. (1993). “Strengthening of concrete beams by external prestressing.” PCI J., 38(6), 76–88.
6.
Harajli, M. H., and Hijazi, S. A. (1991). “Evaluation of the ultimate steel stress in partially prestressed concrete members.” PCI J., 36(1), 62–82.
7.
Khairallah, N., and Harajli, M. H. (1997). “Experimental and analytical evaluation of the behavior of concrete T beams with external prestressing.” Res. Rep., Dept. of Civ. and Envir. Engrg., Faculty of Engineering and Architecture, American University of Beirut, Beirut, Lebanon.
8.
Khairallah, N., and Harajli, M. H. (1997). “Experimental evaluation of the behavior of reinforced concrete T beams strengthened using external prestressing.” Proc., Int. Conf. on Rehabilitation and Devel. of Civ. Engrg. Infrastructure Sys., M. Harajli and A. Naaman, eds., American University of Beirut, Beirut, Lebanon, 2, 1282–1293.
9.
Menegotto, M., and Pinto, P. E. (1973). “Method of analysis for cyclically loaded reinforced concrete plane frames.” IABSE preliminary report for symposium on resistance and ultimate deformability of structures acted on well-defined repeated loads, Lisbon, 15–22.
10.
Miyamoto, A., and Nakamura, H. (1997). “Application of prestressing technique with external tendons to existing bridge strengthening.” Proc., Int. Conf. on Rehabilitation and Devel. of Civ. Engrg. Infrastructure Sys., M. Harajli and A. Naaman, eds., American University of Beirut, Beirut, Lebanon, 2, 242–255.
11.
Moon, J. H., and Burns, N. H. (1997). “Flexural behavior of members with unbonded tendons. II: Application.”J. Struct. Engrg., ASCE, 123(8), 1095–1101.
12.
Naaman, A. E., and Breen, J. E., eds. ( 1990). “External prestressing in bridges.” ACI Special Publ. SP-120, American Concrete Institute, Detroit.
13.
Naaman, A. E., and Alkhairi, F. M. (1991b). “Stress at ultimate in unbonded post-tensioned tendons.” ACI Struct. J., 88(6), 683–692.
14.
Nowak, A. S., and Absi, E., eds. (1987). “Structural strengthening by external prestressing.” Proc., US-European Workshop on Bridge Evaluation, Repair and Rehabilitation, University of Michigan, Ann Arbor, Mich.
15.
Rabbat, B. G., and Sowlat, K. (1987). “Testing of segmental concrete girders with external tendons.” PCI J., 32(2), 86–107.
16.
Scott, B. D., Park, R., and Priestly, M. N. (1982). “Stress-strain behavior of concrete confined by overlapping hoops at low and high strain rates.” ACI Struct. J., 79(1), 13–27.
17.
Tan, K.-H., and Ng, C.-K. (1997). “Effects of deviators and tendon configuration on behavior of externally prestressed beams.” ACI Struct. J., 94(1), 13–22.
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Received: Apr 6, 1999
Published online: Oct 1, 1999
Published in print: Oct 1999
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