The aim of this paper is to discuss the seismic improvement of a RC building according to the new Italian Code: the study building was designed in 80's according to the old seismic code (allowable stress method) and it was realized with poor reinforcement details (without capacity-design criteria) and low strength concrete (due to wrong casting in situ); it was placed in a sloping and sliding ground and shows relevant differential vertical displacements too. It appears as a very interesting case study above all in the aim to use the new Italian Code. The study building was built in Offida, about 70 km from the epicenter area of 2009 L'Aquila Earthquake. The site is a sloping and sliding one and some nearby RC buildings of similar design approach collapsed due to foundation movements. Deep pile foundations have varying lengths due to the stratification of the soil. Due to L'Aquila Earthquake (01:32:39 UTC 06/Apr/2009 ML = 5.80) it suffered a relevant non-structural damage in spite of a low estimated ground acceleration (ag/g 0.03, lower of both the design ground acceleration [ag/g = 0.07 - almost equal to actual Damage Limit State] and the actual Collapse Limit State acceleration [ag/g = 0.228]). A comprehensive in situ tests on concrete and steel reinforcement was carried out: poor reinforcing detailing, low strength concrete (about an half of design strength) and relevant differential vertical displacements are detected with different vertical slope gradients of columns due to building phases differential vertical displacements. The design of the seismic improvement of the superstructure, according to the real foundation characteristics, is the paper topic: the improvement of the horizontal stiffness of RC frames has to be attained considering that ultimate failure loads in columns can be assigned in the elastic range of the foundation system. The design of the seismic improvement of the superstructure, according to the actual foundation characteristics, is the topic of this paper.
Seismic Improvement of an Existing RC Building with Pile Foundation on a Sloping and Sliding Ground
BIONDI, Samuele
2011-01-01
Abstract
The aim of this paper is to discuss the seismic improvement of a RC building according to the new Italian Code: the study building was designed in 80's according to the old seismic code (allowable stress method) and it was realized with poor reinforcement details (without capacity-design criteria) and low strength concrete (due to wrong casting in situ); it was placed in a sloping and sliding ground and shows relevant differential vertical displacements too. It appears as a very interesting case study above all in the aim to use the new Italian Code. The study building was built in Offida, about 70 km from the epicenter area of 2009 L'Aquila Earthquake. The site is a sloping and sliding one and some nearby RC buildings of similar design approach collapsed due to foundation movements. Deep pile foundations have varying lengths due to the stratification of the soil. Due to L'Aquila Earthquake (01:32:39 UTC 06/Apr/2009 ML = 5.80) it suffered a relevant non-structural damage in spite of a low estimated ground acceleration (ag/g 0.03, lower of both the design ground acceleration [ag/g = 0.07 - almost equal to actual Damage Limit State] and the actual Collapse Limit State acceleration [ag/g = 0.228]). A comprehensive in situ tests on concrete and steel reinforcement was carried out: poor reinforcing detailing, low strength concrete (about an half of design strength) and relevant differential vertical displacements are detected with different vertical slope gradients of columns due to building phases differential vertical displacements. The design of the seismic improvement of the superstructure, according to the real foundation characteristics, is the paper topic: the improvement of the horizontal stiffness of RC frames has to be attained considering that ultimate failure loads in columns can be assigned in the elastic range of the foundation system. The design of the seismic improvement of the superstructure, according to the actual foundation characteristics, is the topic of this paper.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
