Contents lists available at ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct Determining dynamic characteristics of high rise buildings using interferometric radar system M. Sofi a, ⁎ , E. Lumantarna a , A. Zhong a , P.A. Mendis a , C. Duffield a , R. Barnes b a Department of Infrastructure Engineering, The University of Melbourne, Parkville 3010, Victoria, Australia b Papworths Construction Testing Equipment, Suite 2, Level 1, 949-951 Wellington St, West Perth 60005, Western Australia, Australia ARTICLE INFO Keywords: Tall buildings Field measurement Non-contact sensor Mode shapes Dynamic analysis ABSTRACT Dynamic performance measurement of buildings using conventional contact sensors such as accelerometers, tilt meters and Global Positioning System (GPS) can be difficult due to accessibility restrictions, particularly during construction or retrofitting periods. This is one of the first studies using a non-contact microwave interferometry radar based system for dynamic measurement of high rise buildings. This paper presents results of a combined experimental and analytical approach to investigate modal properties of two high rise buildings in Australia. Dynamic properties of the buildings, namely Soul building and Zen Apartments, were investigated. The choices of the buildings were based on the different physical properties and plan layouts of the buildings. To capture the dynamic characteristics of the buildings, field measurements were carried out using an interferometric radar based equipment and compared with results from more conventional contact-sensors such as accelerometers and GPS. The building vibration test results were then correlated with the buildings’ respective finite element modelling (FEM) simulations to test the capability of the radar in capturing mode shapes of the buildings. Finite elements software ETABS was used for this purpose. Results show that interferometric radar system has the potential as a non-contact instrument to be effectively used to measure the dynamic properties including mode shapes of high rise buildings. 1. Introduction High rise buildings are becoming increasingly important features of most urban centres around the world. They are characterised by their slenderness and sensitivity to external actions such as wind, earthquake and service loadings. Resistance to lateral forces is a requisite for almost all building types and understanding the dynamic behaviour of tall buildings is imperative in order to be able to deliver effective design solutions that satisfy the requirements of stability, strength and servi- ceability. The design of tall buildings is governed by their dynamic performance. Due to the growing concerns of increased extreme weather events, natural events and climate change, condition assessment and mon- itoring of buildings have gained increased interest. Any building failure could cause substantial damage to the property, amenity and even lead to eventual loss of life. It is very important that the building structural performance is monitored during its construction, retrofitting works particularly when the building is stripped for renovation, post-extreme events and at the end of its service life. Various types of dynamic acquisition sensors have been developed over the past decades for the purpose of structural health monitoring. Depending on the method of application, those sensors are generally categorised into two groups: traditional contact sensors and more re- mote sensors. The most regularly used acquisition instrumentations in the dynamic testing of buildings are accelerometers [e.g., 1–4], tilt- meters and inclinometers [e.g., 5–8] which are categorised as contact sensors. They have a relatively low cost and high sensitivity [5,9]. The recent development of wireless communication has eliminated sub- stantial efforts associated with the hardwiring of the sensors when used in a network to capture the global behaviour of structures. Recent ad- vancement in Global Positioning System (GPS) has also allowed the technology to be used in the dynamic monitoring of structures [e.g., 10–15]. However, their mounting process is still considerably difficult and can be prohibitive in some cases. Construction managers and owners’ corporations are often reluctant to provide easy access to the building for the installation of sensors. Other than concerns with safety, it is mostly inconvenient to install contact sensors which will require power input, wiring between sensors and data loggers without inter- fering with construction work. For these reasons alone, innovative re- mote sensing devices, which do not rely on physical contact with https://doi.org/10.1016/j.engstruct.2018.02.084 Received 30 April 2017; Received in revised form 21 January 2018; Accepted 26 February 2018 ⁎ Corresponding author. E-mail address: massoud@unimelb.edu.au (M. Sofi). Engineering Structures 164 (2018) 230–242 0141-0296/ Crown Copyright © 2018 Published by Elsevier Ltd. All rights reserved. T