Evaluation of the seismic retrofitting of an unreinforced masonry building using numerical modeling and ambient vibration measurements

Abstract

Ambient vibration measurements and 3-D nonlinear time-history numerical modeling are used to assess the retrofitting measures conducted in a 6-story unreinforced masonry building (URM) built in the end of the 19 th century in Switzerland. Retrofitting measures were taken in order to improve the soundproofing and possibly the seismic performance of the building. Reinforced concrete (RC) footings were added under the walls and horizontal steel beams were added to link the walls together with a RC slab at each floor, though the wooden beams were left in place. Several ambient vibration recordings were performed before, during and after the retrofitting work in order to monitor the evolution of the dynamic behavior of the structure. Moreover, numerical models representing the state of the building before and after the retrofit work have been developed to perform nonlinear dynamic analyses using various ground motion records. The change in the modal vibration frequencies, mode shapes, and failure mechanism are presented and discussed in further details. According to ambient vibration measurements, the performed retrofitting resulted in an increase of about 25% of the fundamental frequency. From the results of both the numerical modeling and the ambient vibration measurements, it is confirmed that the in-plane behavior of the slabs evolved from non-rigid floors with in-plane deformation to rigid floors with diaphragm effects. The ambient vibration measurements show that the new stiff slabs could lead to torsion behavior in the building as the result of the diaphragm effect and to higher seismic demand. However, the numerical models show that the displacement capacity of the building increases as a result of those new stiff slabs. Consequently, higher deformation capacity, indicated by the inter-story drift values, on average, are observed for all the damage grades in the post-retrofit state of the building. Finally, the overall seismic safety was only slightly improved.

A model-based data-interpretation framework for post-earthquake building assessment with scarce measurement data

“…However, shear-compression failure due to high axial loads is not taken into consideration. AEM has been shown by several researchers [53,54,55,56,57,58,59,60] to predict post-yield structural behavior of masonry and reinforced-concrete structures that are defined by a particularly large range of potential failure modes. The applicability of AEM to successfully simulate large 8 deformations has been demonstrated by Tagel-Din and Meguro [61], among others.…”

Seismic Design of Timber Buildings: Highlighted Challenges and Future Trends

“…Seismic retrofit strategies have been developed in the past few decades following the introduction of new seismic provisions and the availability of advanced materials. Different techniques and methods are applied for a seismic retrofitting of different structures (e.g., concrete structures [97][98][99], timber structures [35,100,101], historical and heritage structures [102][103][104] and especially masonry structures [3,[105][106][107]).…”

AMBIENT VIBRATION ANALYSIS of an INDUSTRIAL BUILDING

“…Moreover, it was not possible to calculate the experimentally obtained modal behavior parameters if the fill walls were omitted in the finite element model. Kusunoki et al (2018) and Michel et al (2018) have measured uncertainties in existing masonry buildings behavior with the application of operational (environmental) modal analysis. Martakis et al (2020) have analysed the vibrational recordings during the demolition of an existing masonry building.…”