The structural role played by masonry infills on RC building performances after the 2011 Lorca, Spain, earthquake

Abstract

On May 11, 2011 an earthquake of magnitude 5.1 ( TeX ) struck Murcia region causing nine casualties and damage to buildings and infrastructures. Even if the main characteristics of the event would classify it as a moderate earthquake, the maximum Peak Ground Acceleration (PGA) registered (equal to 0.37 g) exceeded significantly local code provisions in terms of hazard at the site. This high PGA was a result of directivity effects in the near source region. An overview of earthquake characteristics and damage observed is provided. Notwithstanding the lack of proper structural design characterizing building stock in the area, most of the losses were caused by non-structural damage. According to in field observations, it emerges that masonry infills provided additional, “not designed”, strength to reinforced concrete (RC) buildings. Observed damage data, collected after the earthquake, are shown and compared to the results of a simplified approach for nonstructural damage assessment of RC infilled structures (FAST vulnerability approach). The latter comparison provided a fair accordance between observed data and analytical results

Analytical versus observational fragilities: the case of Pettino (L’Aquila) damage data database

“…This capacity curve can be defined in the acceleration displacement response spectrum (ADRS) format (S a -S d ) through the definition of four parameters (see also De Luca et al 2013a;Manfredi et al 2013):…”

“…C s,design is the design acceleration coefficient of the bare structure at the attainment of the plastic mechanism of the bare RC structure. It can be evaluated made considering obsolete seismic design provisions in terms of design spectral acceleration, amplified by structural redundancy factor (R  ) and overstrength material factor (R  ), see De Luca et al (2013a) for details.…”

“…The observational fragilities obtained are then employed for the calibration of FAST method, a large scale vulnerability approach for infilled RC moment resisting frames (MRF). This methodology has been applied to different earthquake cases (De Luca et al 2013a;Manfredi et al 2013), such as Lorca (2011), Spain, and Emilia (2012), Italy. The approach belongs to the wider family of vulnerability assessment methodologies based on spectral displacements (e.g., Kircher et al 1997;Erdik et al 2004, among others) in which damage states are classified according to the 1998 European Macroseismic Scale (Grünthal et al 1998).…”

“…Even if comparisons of FAST with damage data have been made also for Lorca and Emilia earthquakes (see De Luca et al 2013a;Manfredi et al 2013), this is the first case in which damage data are enough accurate to carry out observational fragility curves to be compared to FAST analytical fragilities. Thus, it was possible to calibrate input variables of FAST method and select the optimal choice to get a satisfactory agreement between observational and analytical data.…”

Seismic performances and behaviour factor of wide-beam and deep-beam RC frames

“…NCSE-02 capacity design rules have been demonstrated to be inefficient and sometimes impossible to be employed because it imposes the strength hierarchy by increasing the safety factor of the brittle element/mechanism (e.g., column with respect to beam) instead of dimensioning them based on the capacity of the ductile element/mechanism [10] [25][41] [42].…”