Displacement Based Approach for the Seismic Retrofitting of a RC Existing Building Designed for only Gravitational Loads

Abstract:

The present paper deals with the evaluation of the level of seismic vulnerability of a Reinforced Concrete (RC) building by using a Displacement Based Approach (DBA), in the context of a performance methodology, and by adopting the N-2 method, according to Italian seismic code NTC 2008. The RC building is located in Southern Italy in an area classified as high seismicity zone and designed, in the past, only for gravitational loads. During the evaluation phase the effect of masonry infills is considered by modeling with a non linear analysis all the panels considered in effective interaction with the structural frame. It is highlighted that in the examined case the masonry infills determine a worsening of the seismic behavior of the existing structure. So that it is illusory that by neglecting these panels a general beneficial effect would be obtained. Moreover in such case the neglect of these panels would have guided to a retrofitting strategy which is completely different and would have not answered to the real needs of the structure. The correct evaluation of the seismic response is finalized to the seismic retrofitting by using a traditional strategy, designed through a displacement based approach, for reducing the displacement demand on the existing structure. The adopted retrofitting strategy is represented by steel braces with steel reinforcement elements for the columns. In the non linear model for these elements it has been considered their confinement action for the reinforced concrete columns. The vulnerability level of the structure and the Safety Factor (SF), defined as the ratio between the displacement capacity and the displacement demand, is calculated for the building before and after the seismic retrofitting.

• Periodical: Applied Mechanics and Materials (Volumes 166-169)
• Pages: 1718-1729
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.166-169.1718
• Online since: May 2012
• Authors: Donato Cancellara, Fabio de Angelis, Vittorio Pasquino
• Keywords: Assessment and Seismic Retrofitting, Displacement Based Approach, RC Building

References

[1] Oliveto G., Decanini L.D., "Repair and retrofit of a six storey reinforced concrete building damaged by the earthquake in south-east Sicily on the 13th December 1990", Soil Dynamics and Earthquake Engineering, Volume 17, Issue 1, January 1998, pp.57-71(15).

DOI: 10.1016/s0267-7261(97)00014-6

[2] Paulay T., Priestley M.J.N., "Seismic Design of Reinforced Concrete and Masonry Buildings", Wiley Interscience – New York, 1992.

[3] Dolsek M., Fajfar P., "The effect of masonry infills on the seismic response of a four – storey reinforced concrete frame – a deterministic assessment", Engineering Structures, Volume 30, Issue 7, July 2008, pp.1991-2001.

DOI: 10.1016/j.engstruct.2008.01.001

[4] Panagiotakos T.B., Fardis M.N., "Seismic response of infilled rc frames structures", Proceedings of 11th World Conference on Earthquake Engineering; Paper No.225 - Acapulco, 1996.

[5] Panagiotakos T.B., Fardis M.N., "Seismic design and response of bare and masonry-infilled reinforced concrete buildings. Part II: infilled structures", Journal of Earthquake Engineering, 1997; vol.1, n.3: 475-503.

DOI: 10.1080/13632469708962375

[6] Panagiotakos T.B., Fardis M.N., "Deformations of RC members at yielding and ultimate", ACI Structural Journal, Volume 98, Issue 2, 2001-3, pp.135-148.

[7] NTC 2008, Decreto Ministeriale 14/01/2008, "Nuove Norme Tecniche per le Costruzioni" - Gazzetta Ufficiale n. 29 del 4 febbraio 2008 - Suppl. Ordinario n. 30, Roma.

[8] Mainstone R.J., "On the stiffness and strength of infilled frames", Proceedings of the Institution of Civil Engineers, Supplement (IV) - London, 1971; Paper 7360S: 57-89.

[9] Mainstone R.J., "Supplementary note on the stiffness and strength of infilled frames", Current Paper CP13/74, Building Research Establishment - London, 1974.

[10] Fajfar P., "Capacity spectrum method based on inelastic demand spectra", Earthquake Engineering & Structural Dynamics, Volume 28, Issue 9, September 1999, pp.979-993.

DOI: 10.1002/(sici)1096-9845(199909)28:9<979::aid-eqe850>3.0.co;2-1

[11] Fib 2003, "Seismic Assessment and Retrofit of Reinforced Concrete Buildings", Part a, State-of-art report prepared by Task Group 7.1, Bulletin 24, FIB - Féd. Int. du Béton, May 2003.

DOI: 10.35789/fib.bull.0024.ch03