Safety Factors for Assessment of Existing Structures
Publication: Journal of Structural Engineering
Volume 128, Issue 2
Abstract
Current structural codes have been developed mainly for new design and are not efficient for assessment because of significant differences between these situations. One of the main differences is the possibility to update information about an existing structure. This paper proposes a way in which updating can be taken into account when developing code safety formats (partial factor and load and resistance factor design). Updating information about individual structural properties such as material strengths by carrying out on-site inspections is discussed. Uncertainties associated with on-site testing including “model” uncertainty are considered and a method for treating these uncertainties in the context of the partial factor format is described. Results indicate that “model” uncertainty may have a significant effect on partial factors. Furthermore, we consider updating information about the resistance of the whole structure by proof load testing or by taking into account the previous safe performance of a structure. Results show that to increase the resistance reduction factor, the level of proof load needs to be high, resulting in a rather high risk of failure during the test. Satisfactory past performance does not have any noticeable effect on resistance factor, but it does have a more significant effect on probability of failure.
Get full access to this article
View all available purchase options and get full access to this article.
References
AASHTO. (1994). AASHTO-LRFD bridge design specifications, Association of State Highway and Transportation Officials, Washington, D.C.
ACI318. (1995). Builidng code requirements for structural concrete, ACI, Detroit.
ASCE 7-98. (2000). Minimum design loads for buildings and other structures, ASCE, New York.
Allen, D. E.(1991). “Limit states criteria for structural evaluation of existing buildings.” Can. J. Civ. Eng., 18, 995–1004.
Chalk, P. L., and Corotis, R. B.(1980). “Probability models for design live loads.” J. Struct. Div. ASCE, 106(ST10), 2017–2033.
Ellingwood, B.(1996). “Reliability-based condition assessment and LRFD for existing structures.” Struct. Safety, 8(2–3), 67–80.
Fu, G., and Tang, J.(1995). “Risk-based proof-load requirements for bridge evaluation.” J. Struct. Eng., 121(3), 542–556.
Fujino, Y., and Lind, N. C.(1977). “Proof-load factors and reliability.” J. Struct. Eng., 103(ST4), 853–870.
Hall, W. B.(1988). “Reliability of service-proven structures.” J. Struct. Eng., 114(3), 608–624.
Hong, H. P.(1998). “Reliability of existing structures.” Civil Eng. Environ. Syst., 15, 187–206.
ISE (1980). “Appraisal of existing structures.” The Institution of Structural Engineers, London.
ISO (1998a). “Assessment of existing structures.” ISO/TC98/SC2/WG6, Doc. N24, 8th Draft.
ISO (1998b) “General principles of reliability for structures.” ISO 2394, Geneva, Switzerland.
Laman, J. A., and Nowak, A. S. (1995). “Site-specific and component-specific bridge load models.” Proc., 6th IFIP WG7.5 Working Conf. on Reliability and Optimization of Structural Systems, Chapman and Hall, London, 167–176.
Moses, F., Lebet, J. P., and Bez, R.(1994). “Applications of field testing to bridge evaluation.” J. Struct. Eng., 120(6), 1745–1762.
Nowak, A. S.(1993). “Live load model for highway bridges.” Struct. Safety, 13(1–2), 53–66.
Nowak, A. S., and Tharmabala, T.(1988). “Bridge reliability evaluation using load tests.” J. Struct. Eng., 114(10), 2268–2279.
Pham, L.(1985). “Reliability analysis of reinforced concrete and composite column sections under concentric loads.” Civil Eng. Trans., CE27(1), 68–72.
Philpot, T. A., Rosowsky, D. V., and Fridley, K. J.(1993). “Servicability design in LRFD for wood.” J. Struct. Eng., 119(12), 3649–3667.
Raiffa, H., and Schlaifer, R. (1961). Applied statistical decision theory, Harvard University Press, Cambridge, Mass.
Stewart, M. G., and Rosowsky, D. V.(1998). “Structural safety and serviceability of concrete bridges subject to corrosion.” J. Infrastruct. Syst., 4(4), 146–155.
Stewart, M. G., and Val, D.(1999). “Role of load history in reliability-based decision analysis of aging bridges.” J. Struct. Eng., 125(7), 776–783.
Thoft-Christensen, P., and Baker, M. J. (1982). Structural reliability theory and its applications, Springer-Verlag, Berlin.
Vrouwenvelder, T.(1997). “The JCSS probabilistic model code.” Struct. Safety, 19(3), 245–251.
Information & Authors
Information
Published In
Journal of Structural Engineering
Volume 128 • Issue 2 • February 2002
Pages: 258 - 265
Copyright
Copyright © 2002 American Society of Civil Engineers.
History
Received: Nov 30, 1999
Accepted: Jul 1, 2001
Published online: Feb 1, 2002
Published in print: Feb 2002
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.