Seismic Vulnerability of Existing RC Buildings and Influence of the Decoupling of the Effective Masonry Panels from the Structural Frames

Abstract:

In the present work we discuss on the seismic vulnerability of reinforced concrete existing buildings. In particular we consider a reinforced concrete building originally designed for only gravitational loads and located in a zone recently defined at seismic risk. According to the Italian seismic code NTC 2008 a displacement based approach is adopted and the N2-method is considered for the nonlinear seismic analysis. In the analysis all the masonry infill panels in effective interaction with the structural frame are considered for the nonlinear modeling of the structure. The influence of the effective masonry infills on the seismic response of the structure is analyzed and it is discussed how the effect of the masonry infills irregularly located within the building can give rise to a worsening of the seismic performance of the structure. It is shown that in the present case a not uniform positioning of the masonry infills within the building can give rise to a fragile structural behavior in the collapse mechanism. Furthermore a comparative analysis is performed by considering both the structure with the effective masonry infills and the bare structural frame. For these two structures a pushover analysis is performed, the relative capacity curves are derived and it is shown that fragile collapse mechanisms can occur depending on the irregular positioning of the effective masonry infills. Accordingly it is discussed how in the present case a decoupling of the effective masonry infills from the structural frame can give rise to a smoother response of the capacity curves. For the examined case of an obsolete building with irregular positioning of the masonry panels, the choice of decoupling the effective masonry panels from the structural frame may facilitate the retrofitting strategies for the achievement of the proper safety factors at the examined limit states.

• Periodical: Applied Mechanics and Materials (Volumes 268-270)
• Pages: 646-655
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.268-270.646
• Online since: December 2012
• Authors: Fabio de Angelis, Donato Cancellara
• Keywords: Displacement Based Approach, RC Building, Seismic Vulnerability

References

[1] 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, (2008).

[2] 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, pp.57-71, (1998).

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

[3] Fajfar, P., Capacity spectrum method based on inelastic demand spectra, Earthquake Engineering & Structural Dynamics, Vol. 28, Issue 9, pp.979-993, (1999).

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

[4] Panagiotakos, T.B., Fardis M.N., Deformations of RC members at yielding and ultimate, ACI Structural Journal, Vol. 98, Issue 2, pp.135-148, (2001).

[5] FIB 2003, Fédération Internationale du Béton: Seismic Assessment and Retrofit of Reinforced Concrete Buildings, State-of-art report prepared by Task Group 7.1, FIB Bulletin n. 24, (2003).

DOI: 10.35789/fib.bull.0024.ch03

[6] Paulay T., Priestley M.J.N., Seismic Design of Reinforced Concrete and Masonry Buildings, Wiley Interscience, New York, (1992).

[7] 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, pp.1991-2001, (2008).

DOI: 10.1016/j.engstruct.2008.01.001

[8] 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).

[9] 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, vol.1, n.3, pp.475-503, (1997).

DOI: 10.1080/13632469708962375

[10] Cancellara, D., De Angelis, F., Pasquino, V., Displacement based approach for the seismic retrofitting of a RC existing building designed for only gravitational loads, Applied Mechanics and Materials, Vol. 166-169, pp.1718-1729, (2012).

DOI: 10.4028/www.scientific.net/amm.166-169.1718

[11] De Angelis, F., An internal variable variational formulation of viscoplasticity, Computer Methods in Applied Mechanics and Engineering, Vol. 190, n. 1-2, pp.35-54, (2000).

DOI: 10.1016/s0045-7825(99)00306-0

[12] De Angelis, F., A variationally consistent formulation of nonlocal plasticity, Int. Journal for Multiscale Computational Engineering, Vol. 5, n. 2, pp.105-116, (2007).

DOI: 10.1615/intjmultcompeng.v5.i2.40

[13] De Angelis, F., Multifield potentials and derivation of extremum principles in rate plasticity, Materials Science Forum, Vol. 539-543, pp.2625-2630, (2007).

DOI: 10.4028/www.scientific.net/msf.539-543.2625

[14] De Angelis, F., On constitutive relations in non-smooth elasto/viscoplasticity, Advanced Materials Research, Vol. 566, pp.691-698, (2012).

DOI: 10.4028/www.scientific.net/amr.566.691

[15] De Angelis, F., Evolutive laws and constitutive relations in nonlocal viscoplasticity, Applied Mechanics and Materials, Vol. 152-154, pp.990-996, (2012).

DOI: 10.4028/www.scientific.net/amm.152-154.990

[16] De Angelis, F., A comparative analysis of linear and nonlinear kinematic hardening rules in computational elastoplasticity, Technische Mechanik, Vol. 32, n. 2-5, pp.164-173, (2012).

[17] De Angelis, F., Computational issues in rate dependent plasticity models, Advanced Materials Research, Vol. 566, pp.70-77, (2012).

DOI: 10.4028/www.scientific.net/amr.566.70

[18] De Angelis, F., Computational aspects in the elasto/viscoplastic material behavior of solids, Advanced Materials Research, Vol. 567, pp.192-199, (2012).

DOI: 10.4028/www.scientific.net/amr.567.192

[19] De Angelis, F., Numerical algorithms for J2 viscoplastic models, Advanced Materials Research, Vol. 567, pp.267-274, (2012).

DOI: 10.4028/www.scientific.net/amr.567.267

[20] De Angelis, F., Cancellara, D., Modano, M., Pasquino, M., The consequence of different loading rates in elasto/viscoplasticity, Procedia Engineering, Vol. 10, pp.2911-2916, (2011).

DOI: 10.1016/j.proeng.2011.04.483

[21] De Angelis, F., Cancellara, D., Implications due to different loading programs in inelastic materials, Advanced Material Research, Vol. 422, pp.726-733, (2012).

DOI: 10.4028/www.scientific.net/amr.422.726

[22] De Angelis, F., Cancellara, D., Results of distinct modes of loading procedures in the nonlinear inelastic behavior of solids, Advanced Material Research, Vol. 482-484, pp.1004-1011, (2012).

DOI: 10.4028/www.scientific.net/amr.482-484.1004

[23] Stafford-Smith B., Behaviour of square infilled frames, Journal of the Structural Division, vol. 92, n.ST1, pp.381-403, (1966).

[24] Bonardi, A., Influenza della modellazione strutturale sulla risposta sismica di edifici in cemento armato, (in italian), Università degli Studi di Brescia, Italy, (2004).

[25] Mainstone R.J., On the stiffness and strength of infilled frames, Proceedings of the Institution of Civil Engineers, Supplement (IV), Paper n. 7360S, pp.57-89, (1971).

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

[27] Cancellara, D., De Angelis, F., Steel braces in series with hysteretic dampers for reducing the seismic vulnerability of RC existing buildings: assessment and retrofitting with a non-linear model, Applied Mechanics and Materials, Vol. 204-208, pp.2677-2689, (2012).

DOI: 10.4028/www.scientific.net/amm.204-208.2677

[28] Cancellara, D., De Angelis, A nonlinear analysis for the retrofitting of a RC existing building by increasing the cross sections of the columns and accounting for the influence of the confined concrete, Applied Mechanics and Materials, Vol. 204-208, pp.3604-3616, (2012).

DOI: 10.4028/www.scientific.net/amm.204-208.3604