Before and after Retrofit Behavior and Performance of a 55-Story Tall Building Inferred from Distant Earthquake and Ambient Vibration Data

Abstract

A sparsely instrumented 55-story building in Osaka, Japan, had recorded unprecedented, severe, and long-duration, long-period resonating responses during the 11 March 2011 M9.0 Tohoku earthquake that occurred at 767 km distance. Thereafter, studies of the records resulted in the implementation of a significant retrofit design, comprising dampers and buckling restrained braces (BRBs). The responses of the retrofitted building were also recorded during the 24 April 2016 M7.3 Kumamoto earthquake that occurred at 478 km. The earthquake and on-demand acquired ambient response data are analyzed in this study to assess the impact of this rare, retrofitted and instrumented tall building subjected to long period strong shaking from events originating at far distances. As expected, the fundamental frequency and critical damping ratio of the building increased, albeit small, after the retrofit as compared to before the retrofit. Increase of damping percentage is a positive finding and indicates that even larger percentages may be attained under shaking stronger than the 2016 event. The records indicate that the building still experiences significant resonance, torsion, as well as a beating effect.

Ambient Vibrations of Age-old Masonry Towers: Results of Long-term Dynamic Monitoring in the Historic Centre of Lucca

“…Indeed, changes over time in a building's dynamic properties, such as modal properties (Doebling et al, 1996) or wave velocities (Todorovska, 2009), represent effective damage indicators, provided that the natural changes due to seasonal and daily environmental effects are taken into account. Long-term monitoring plays an important role when a structure is subjected to high vibration levels, such as those induced by traffic or construction sites (Wyjadlowski, 2017), or when the structure is located in high-seismicity areas (Celebi, 2017, Todorovska, 2009, Trifunac, 1970. More recently, the study of the dynamic effects on buildings of the surrounding environment has became a challenging research topic, involving disparate expertise from the fields of physics, geology and engineering, and sometimes referred to as "urban seismology" (Diaz et al, 2017), (Green et al, 2016), (Ritter et al 2005).…”

“…The first attempts to use ambient vibrations to characterize the dynamic properties of buildings date back to the 1970's (Trifunac, 1970). Nowadays, this technique has become standard practice (Celebi, 2017, Gallipoli et al, 2010, Kaya and Safak, 2015, Peeters et al 1999, Prieto et al, 2010 thanks to the availability of sensitive instrumentation for measurement of low-amplitude vibrations, together with powerful algorithms and hardware for large dataset analysis. Ambient vibration monitoring is in fact very convenient, provided that sufficiently long records are available (Brincker, 2015), since it allows avoiding artificial vibration sources such as vibrodynes, thereby facilitating experiment management.…”

Structural health building response induced by earthquakes: Material softening and recovery

“…It is known that structural damage caused by earthquakes produces permanent frequency changes related to a loss of stiffness 13,[16][17][18] ; this is usually linked to the disconnection of structural and nonstructural elements, joint deformation, variations in the friction/border conditions between elements, and the opening of cracks. The recovery process observed after earthquakes would reveal the (partial or total) restoration of these effects.…”

Vibration-based temporary monitoring of a 253 m tall skew-plan building in Istanbul

“…Several time and frequency domain methods, for example, spectral analysis (Peeters and De Roeck, 2001), frequency domain decomposition (Brincker et al, 2001), subspace identification (Van Overschee and De Moor, 1996), wave interferometry (Snieder and Safak, 2006), random decrement technique (Cole, 1973), are available for identifying in situ dynamic properties of structural systems from recorded building responses (e.g. Celebi et al, 2017). Methods based on spectral analysis were successfully applied to buildings with well-separated modes and low damping, such as the test building in this study as illustrated subsequently, for identifying their natural vibration frequencies and mode shapes (Peeters and De Roeck, 2001).…”

“…They serve as baseline properties and can be used in validating the linear elastic structural model for service-level evaluations. Building response records under strong earthquakes (Celebi et al, 2016, 2017, 2020; Celebi and Safak, 1991; Rahmani and Todorovska, 2015, 2021) are needed for validating the evaluations under high-amplitude shaking. For this purpose, real-time monitoring of the structural response of buildings of earthquake design class 1 and 2 in Turkey (i.e.…”