Response of Mid-Rise Reinforced Concrete Frame Buildings to the 2017 Puebla Earthquake

Abstract

The response of mid-rise reinforced concrete (RC) buildings in Mexico City after the 2017 Puebla Earthquake is assessed through combined field and computational investigation. The Mw 7.1 earthquake damaged more than 500 buildings where most of them are classified as mid-rise RC frames with infill walls. A multinational team from Colombia, Mexico, and the United States was rapidly deployed within a week of the occurrence of the event to investigate the structural and nonstructural damage levels of over 60 RC buildings with 2–12 stories. The results of the study confirmed that older mid-rise structures with limited ductility capacity may have been shaken past their capacity. To elucidate the widespread damage in mid-rise RC framed structures, the post-earthquake reconnaissance effort is complemented with inelastic modeling and simulation of several representative RC framing systems with and without masonry infill walls. It was confirmed that the addition of non-isolated masonry infills significantly impacts the ductility capacity and increases the potential for a soft-story mechanism formation in RC frames originally analyzed and designed to be bare systems.

Overview of collapsed buildings in Mexico City after the 19 September 2017 (Mw7.1) earthquake

“…Therefore, it was not surprising to observe severe damage and even collapse in these buildings because of the 2017 Puebla–Morelos earthquake. In addition to the aforementioned field observations, Arteta et al (2019) confirmed with numerical modeling that non-isolated masonry infills in pre-1985 RC buildings significantly reduced the structure’s ductility capacity of these structures and promoted damage localization in the first two stories. Figure 14 depicts a building with a weak first story which suffered severe damage at the columns (i.e.…”

“…Based on the aforementioned, it is evident that an intraslab normal-faulting event with the magnitude and distance of the 2017 Puebla-Morelos earthquake was not surprising. Arteta et al (2019) reached a similar conclusion by comparing recorded ground motions of the Puebla-Morelos earthquake with global and local GMPEs. Moreover, Singh et al (2018) estimated that an intraslab earthquake capable of producing a PGA of 60 cm/s 2 at CU station, located on the hill zone of Mexico City, has a return period of at least 150 years.…”

Response of thin lightly-reinforced concrete walls under cyclic loading

“…The walls in the structural system under discussion have several characteristics that introduce significant differences in terms of geometry and reinforcement distribution when compared to the traditional cast-in-place reinforced concrete (RC) wall buildings considered by the ACI 318 provisions. One of the main differences is the use of walls with significantly reduced thickness (t w ) that can be as low as 70 mm with a typical range between 100 and 150 mm [3]. Such reduced thickness can be specified by designers, as the code does not have an explicit minimum value for this parameter for reinforced concrete walls.…”

Evaluation of different cases of soft story formation for mid-rise RC buildings

“…After the results of this study and the studies of Arteta et al [10] , Bozyigit and Yesilce [14] are accounted, it is seen that the infill walls significantly changed the behavior of the structure. If infill walls are regarded as load carrying elements, the lateral strength of the building increases, and displacement capacity decreases as reported in Harsoor and Shreenath's study [12] and Santhi's study [13].…”

“…Soft story irregularity is one of the main reasons of building damages during recent earthquakes in the world as mentioned in almost all reconnaissance reports and studies [1][2][3][4][5][6]. Previous studies have shown that infill walls have also an important influence on the formation of structural irregularities such as soft floors, weak floors, torsional irregularity and short columns [7][8][9][10]. Soft story may arise not only because of sudden changes in structural system (like height of the stories) but also due to abrupt changes in amount of infill walls between stories.…”