Dynamics of Civil Structures, Volume 2

River Rapids Conference Proceedings of the Society for Experimental Mechanics Series Dynamics of Civil Structures, Volume 2 Juan Caicedo Shamim Pakzad Proceedings of the 33rd IMAC, A Conference and Exposition on Structural Dynamics, 2015 River Publishers

Conference Proceedings of the Society for Experimental Mechanics Series Series Editor TomProulx Society for Experimental Mechanics, Inc., Bethel, CT, USA

River Publishers Juan Caicedo • Shamim Pakzad Editors Dynamics of Civil Structures, Volume 2 Proceedings of the 33rd IMAC, A Conference and Exposition on Structural Dynamics, 2015

Published, sold and distributed by: River Publishers Broagervej 10 9260 Gistrup Denmark www.riverpublishers.com ISBN 978-87-7004-906-1 (eBook) Conference Proceedings of the Society for Experimental Mechanics An imprint of River Publishers © The Society for Experimental Mechanics, Inc. 2015 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, or reproduction in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Preface Dynamics of Civil Structures represents one of ten volumes of technical papers presented at the 33rd IMAC, A Conference and Exposition on Balancing Simulation and Testing, 2015, organized by the Society for Experimental Mechanics, and held in Orlando, Florida, February 2–5, 2015. The full proceedings also include volumes on Nonlinear Dynamics; Model Validation and Uncertainty Quantification; Sensors and Instrumentation; Special Topics in Structural Dynamics; Structural Health Monitoring & Damage Detection; Experimental Techniques, Rotating Machinery & Acoustics; Shock & Vibration Aircraft/Aerospace, Energy Harvesting; and Topics in Modal Analysis. Each collection presents early findings from experimental and computational investigations on an important area within Structural Dynamics. Dynamics of Civil Structures is one of these areas. The Dynamics of Civil Structures Technical Division serves as a primary focal point within the SEM umbrella for technical activities devoted to civil structures testing, monitoring, and assessment. This volume covers dynamic testing and analysis of all kinds of civil engineering structures such as buildings, bridges, stadiums, dams, etc. Over the last few years, there has been an interest in input and output modal analysis, as well as output only, ambient vibration testing of bridges. In addition to the material in this volume, a number of technical contributions devoted to new methods, non-linear dynamics, wind turbine dynamics, and monitoring related to civil structure dynamics may be found in other volumes of these proceedings. The organizers would like to thank the authors, presenters, session organizers, and session chairs for their participation in this track. Columbia, SC, USA Juan Caicedo Bethlehem, PA, USA Shamim Pakzad v

Contents 1 Determination of Modal Properties of an Irregular 20-Story Concrete Shear Wall Building .................. 1 Ferya Moayedi, Salman Soleimani-Dashtaki, and Carlos E. Ventura 2 Effect of Foundation Rocking on the Dynamic Characteristics of a 30-Story Concrete Shear Wall Building.......................................................................................... 11 Salman Soleimani-Dashtaki, Ferya Moayedi, and Carlos E. Ventura 3 Ambient Vibration Testing of a 4-Storey Parking Garage.......................................................... 31 Ilaria Capraro, Yuxin Pan, Kieran Rollins, Wu Gao, and Carlos E. Ventura 4 Blind Source Separation: A Generalized Modal Identification Tool for Civil Structures ....................... 39 AyanSadhu 5 Developments with Motion Magnification for Structural Modal Identification Through Camera Video ..... 49 Justin G. Chen, Neal Wadhwa, Frédo Durand, William T. Freeman, and Oral Buyukozturk 6 Interactive Platform to Include Human-Structure Interaction Effects in the Analysis of Footbridges........ 59 Daniel Gomez, Christian E. Silva, Shirley J. Dyke, and Peter Thomson 7 Comparing Closed Loop Control Models and Mass-Spring-Damper Models for Human Structure Interaction Problems........................................................................................ 67 Albert R. Ortiz-Lasprilla and Juan M. Caicedo 8 Stochastic Load Models and Footbridge Response .................................................................. 75 Lars Pedersen and Christian Frier 9 Pedestrian Induced Lateral Vibrations with Emphasis on Modal Energy Transfer ............................. 83 Anders Rønnquist 10 Implications of Interaction Between Humans and Structures...................................................... 93 Lars Pedersen 11 A Correlation Analysis Regarding the Temperature Effect for a Suspension Bridge............................ 99 Jin-Woo Jung, Dae-Joong Moon, Ji-Won Jung, Sang-Kon Ro, and Ji-Hyun Park 12 Total Load Effects of Portal Frame Bridges in High-Speed Railway Lines....................................... 107 Daniel Cantero and Raid Karoumi 13 Monitoring Wind Velocities and Dynamic Response of the Hardanger Bridge .................................. 117 Ole Øiseth, Anders Rönnquist, Knut Andreas Kvåle, and Ragnar Sigbjörnsson 14 Modal Analysis of a Floating Bridge Without Side-Mooring....................................................... 127 Knut Andreas Kvåle, Ole Øiseth, Anders Rønnquist, and Ragnar Sigbjörnsson 15 Investigation of a Novel Pseudo Ambient Vibration Testing Approach ........................................... 137 K.A. Grimmelsman and D. Samudio Castillo vii

viii Contents 16 Ambient Vibration Testing of Historic Steel-Composite Bridge, the E. Torroja Bridge, for Structural Identification and Finite Element Model Updating................................................. 147 E. García-Macías, R. Castro-Triguero, R. Gallego, and J. Carretero 17 Tuning of Finite Element Models of Multi-girder Composite Structures ......................................... 157 Elena Mola, Murathan Ahmet Paksoy, Giovanni Rebecchi, Giorgio Busca, Matteo Scaccabarozzi, and Marta Berardengo 18 A Bayesian State-Space Approach for Damage Detection and Classification..................................... 171 Zoran Dzunic, Justin G. Chen, Hossein Mobahi, Oral Buyukozturk, and John W. Fisher III 19 Iterative Spatial Compressive Sensing Strategy for Structural Damage Diagnosis as a BIG DATA Problem................................................................................................ 185 Ruigen Yao, Shamim N. Pakzad, Parvathinathan Venkitasubramaniam, and Jamie M. Hudson 20 Numerical Enhancement of Nonlinear Model Tracking for Health Monitoring ................................. 191 Timothy A. Doughty and Michael J. Hector 21 A Material Basis Frame Approach for Global Deflection Reconstruction of Rod-Like Structures from Strain Measurements ............................................................................................. 201 Michael Todd 22 Influence of Prestressing Strand Damage on Modal Parameters of a Hybrid Composite Bridge Beam....... 209 Timothy P. Kernicky, Matthew J. Whelan, and Cristopher D. Moen 23 Data-Driven Structural Damage Identification Using DIT......................................................... 219 S. Golnaz Shahidi, Ruigen Yao, Michael B.W. Chamberlain, Mallory B. Nigro, Andrew Thorsen, and Shamim N. Pakzad 24 Modal Identification of Superconducting Magnetic Levitating Bogie ............................................. 227 R. Alaggio, F. Benedettini, F. D’Innocenzo, G. D’Ovidio, D. Sebastiani, and D. Zulli 25 Uplift-Monitoring for Dynamic Assessment of Electrical Railway Contact Lines ............................... 237 Petter Nåvik and Anders Rønnquist 26 Finite Element Model Updating Using an Evolutionary Markov Chain Monte Carlo Algorithm............. 245 I. Boulkaibet, L. Mthembu, T. Marwala, M.I. Friswell, and S. Adhikari 27 Formal Analysis of Critical Infrastructures by Structural Identification Using Constraint Programming Paradigm................................................................................................ 255 Usman Rauf, Timothy Kernicky, Matthew J. Whelan, and Ehab Al-Shaer 28 Model Updating of a Nine-Story Concrete Core Wall Building.................................................... 265 Steve McDonald, Lisa Tobber, Adam Gerber, and Carlos E. Ventura 29 Numerical Study and Experimental Validation of a Method for Model Updating of Boundary Conditions in Beams .................................................................................................... 273 Christian E. Silva and Shirley J. Dyke 30 Coordination of Groups Jumping to Popular Music Beats ......................................................... 283 Lefteris Georgiou, Vitomir Racic, James M.W. Brownjohn, and Mark T. Elliot 31 Effects of People Occupancy on the Modal Properties of a Stadium Grandstand ............................... 289 Anna Cappellini, Alessandro Cattaneo, Stefano Manzoni, Matteo Scaccabarozzi, and Marcello Vanali 32 Serviceability Assessment of Two Different Stadium Grandstand During Different Events.................... 299 Anna Cappellini, Ramona Fagiani, and Marcello Vanali 33 SMD Model Parameters of Pedestrians for Vertical Human-Structure Interaction............................. 311 Mengshi Zhang, Christos T. Georgakis, Wenjun Qu, and Jun Chen 34 Identification and Modelling of Vertical Human-Structure Interaction........................................... 319 Katrien Van Nimmen, Kristof Maes, Stana Živanovic´, Geert Lombaert, Guido De Roeck, and Peter Van den Broeck

Contents ix 35 Identification of Stiffness, Damping and Biological Force of SMD Model for Human Walking................ 331 Jiayue Lou, Mengshi Zhang, and Jun Chen 36 Producing Simulated Time Data for Operational Modal Analysis................................................. 339 Esben Orlowitz and Anders Brandt 37 Evaluation of Damping Using Frequency Domain Operational Modal Analysis Techniques................... 351 Anela Bajric´, Christos T. Georgakis, and Rune Brincker 38 An Example of Correlation Matrix Based Mode Shape Expansion in OMA..................................... 357 Rune Brincker, Edilson Alexandre Camargo, and Anders Skafte 39 Experimental vs Operational Modal Analysis: A Flyover Test Case .............................................. 365 Giorgio Busca, Alessio Datteo, Murathan Paksoy, Chiara Pozzuoli, Carlo Segato, and Marcello Vanali 40 Operational Modal Analysis in the Presence of Harmonic Excitations: A Review............................... 379 Kenny Motte, Wout Weijtjens, Christof Devriendt, and Patrick Guillaume 41 Operational Modal Analysis of a Nine-Story Concrete Core Wall Building...................................... 397 Steve McDonald, Adam Gerber, Lisa Tobber, and Carlos E. Ventura 42 Numerical Study of Reduction in Vibrations Induced by Water-Pipe System.................................... 407 Peter Persson, Kent Persson, and Göran Sandberg 43 Seismic Performance Assessment of Steel Frames Upgraded with Self-Centering Viscous Dampers ......... 421 Osman E. Ozbulut, Robert J. Michael, and Baikuntha Silwal 44 Performance Analysis of Cables with Attached Tuned-Inerter-Dampers......................................... 433 Irina F. Lazar, Simon A. Neild, and David J. Wagg 45 Numerical Investigation of Vibration Reduction in Multi-storey Lightweight Buildings ....................... 443 Ola Flodén, Kent Persson, and Göran Sandberg 46 Dynamic Compensators for Floor Vibration Control ............................................................... 455 Donald Nyawako, Paul Reynolds, and Emma Hudson 47 Active Tuned Liquid Column Gas Damper in Structural Control ................................................. 467 Markus J. Hochrainer 48 Semiactive Vibration Control in a Three-Story Building-Like Structure Using a Magnetorheological Damper ......................................................................................... 475 J. Enríquez-Zárate, G. Silva-Navarro, and A. Cabrera-Amado 49 Balancing Testing and Simulation for Design of a Research Facility .............................................. 485 Brad Pridham, Stephen Price, and Brian Roeder 50 Certain Uncertainties: Modelling Unusual Structures to Control Vibrations in Sensitive Areas .............. 497 Michael J. Wesolowsky, Mihkel Toome, Buddy Ledger, Ramin Behboudi, and John C. Swallow 51 Predicting and Mitigating Ground-Borne Vibration Transmission to Elevated Floor Structures ............. 505 Julia M. Graham 52 Mitigation of Wind-Induced Vibration of the Pool-Deck Fence of a Condominium............................. 515 S.A. Smith, W.D. Zhu, and C.M. Hou 53 Isolating a Scanning Electron Microscope from Chiller Unit Vibrations ......................................... 531 B.R. Barben and L.M. Hanagan 54 Dynamic Characteristics of Double Layer Beam with Respect to Different Boundary Conditions ............ 541 Jongsuh Lee, Semyung Wang, Jongnam Kim, and Jaehu Ryu 55 Evaluation of an Automatic Selection Methodology of Model Parameters from Stability Diagrams on a Damage Building ...................................................................................... 545 Boroschek K. Rubén and Bilbao N. Joaquín 56 Original Expression of Tension of a Cable............................................................................ 553 Mathieu Babaz, Louis Jezequel, and Patrick Perrard

Chapter 1 Determination of Modal Properties of an Irregular 20-Story Concrete Shear Wall Building Ferya Moayedi, Salman Soleimani-Dashtaki, and Carlos E. Ventura Abstract This paper presents the results obtained from the ambient vibration measurements done on a 20 story tall building, with reinforced concrete core, located in Vancouver, British Columbia, Canada. The experiment reveals the dynamic characteristics of the investigated building by advanced system identification methods using enhanced signal processing techniques and the fundamentals of frequency domain decomposition. The results include the natural frequencies and the mode shapes of the building obtained from the ambient vibration measurements. The dynamic characteristics of interest in this study are the lateral and torsional natural frequencies and the corresponding mode shapes. A total of 11 modes of vibration, up to the fourth translational and torsional modes, were successfully identified. This paper uses the Enhanced Frequency Domain Decomposition (EFDD) and the Curve-fit Frequency Domain Decomposition (CFDD) methods to identify the modes and utilizes the Frequency Domain Operating Deflection Shapes (FDODS) technique for modal validation. The experimental results were then compared to the analytical estimations from the ETABS models of the building created at the time of the structural design phase and model validation and calibration is performed. Keywords System identification • Experimental techniques • Ambient vibration measurement • Modal estimation • Model validation 1.1 Introduction Ambient vibration measurements have been made on a 20 story tall building located in downtown Vancouver. The tests performed on the building provide information on the dynamic characteristics of the structure including the mode shapes and natural frequencies. Those dynamic characteristics of interest in this study are the lateral and torsional natural frequencies and the corresponding mode shapes. In order to investigate the dynamics of the building, transducers have been used to record vibrations in terms of velocity and acceleration at each floor level. The data were then analyzed and the building was modeled in order to extract the modal properties of the structure. These properties include the natural frequencies of the building and their modes of vibration in the translational and torsional modes, as well as their respective modal damping ratios. The investigated structure has two reinforced concrete cores, each one with a set of stairs from the basement all the way up to the roof. Of the two concrete cores, one also contains an elevator shaft which continues throughout the height of the building. The shape of the building in plan-view is mainly a rectangle with some minor extrusions at some levels. The size of the building in the three lower floors is approximately 36 m by 30 m and in the upper floors it reduces to 30 m by 20 m. Typical storey height is approximately 3.7 m. Figure 1.1 below demonstrates an overview of the building, by presenting an overall photo of the building as well as a typical floor plan for this structure. The building was in the final stages of construction at the time ambient vibration measurements were made, tests were done while the floor tiles were being placed and the cabinets being installed. F. Moayedi ( ) University of British Columbia, 6250 Applied Science Lane, Vancouver, BC V6T 1Z4, Canada e-mail: ferya@civil.ubc.ca S. Soleimani-Dashtaki University of British Columbia, Room 1012 D – 6250 Applied Science Lane, Vancouver, BC V6T 1Z4, Canada C.E. Ventura University of British Columbia, Room 2018 – 6250 Applied Science Lane, Vancouver, BC V6T 1Z4, Canada © The Society for Experimental Mechanics, Inc. 2015 J. Caicedo, S. Pakzad (eds.), Dynamics of Civil Structures, Volume 2, Conference Proceedings of the Society for Experimental Mechanics Series, DOI 10.1007/978-3-319-15248-6_1 1

2 F. Moayedi et al. Fig. 1.1 Photo of the investigated building (a) and typical floor plan (b) 1.2 Experimental Phase The natural modes of vibration of the building are captured by performing ambient vibration measurements on the building structure. Ambient vibration test is preferable to forced vibration measurement for different reasons. In order to obtain the modal parameters of large structures, there is adequate excitation from wind, traffic, and human activity forces. Hence, there would be no need for exciting devices to be used and the risk of damaging the structure can be avoided [1]. In order to perform the ambient vibration measurements on the structure and capture the natural modes of vibration, the velocity and acceleration of the structure, TROMINO® (Micromed) accelerometers were utilized to capture the characteristics of the building. In order to capture the behavior of the structure, measurements were made in different setups. In each setup one transducer was always kept at the highest floor of the building as a reference sensor, recording motions for the entire duration of the test, and a number of transducers were moved around to different floors; having two sensors placed at every single floor at a time, usually at opposing corners. All floors of the building were measured using five transducers, and in total, ten setups were needed to complete the building measurements. Illustrative diagram of the test setups for the building is shown below in Fig. 1.2. Each setup was recorded for a period of 32 min with a sampling rate of 128 Hz. The duration of the measurements and the location of the data recordings were predetermined by looking at the structural drawings and the ETABS model of the building prior to the test. In this study, transducers in each setup recorded data for a minimum duration of 30 min with a minimum sampling rate of 128 Hz. It is recommended to have longer recording time in order to capture the lower frequency content including the lowest modes of vibration. What this paper would like to suggest, to be used as a rule of thumb, is that the measurement duration of 1,000 times the fundamental period of the building, in units of seconds, would result in sufficient data to capture the frequency content of interest with a decent resolution.

1 Determination of Modal Properties of an Irregular 20-Story Concrete Shear Wall Building 3 Fig. 1.2 Typical sensor locations inside building Ref. Transducer Transducer Transducer 1.3 System Identification and Test Results After testing, the recorded data need to be extracted from the TROMINO®s onto a computer using the Grilla® Software. The same software is then used in order to convert the data to ASCII format and a series of basic and preliminary signal processing is performed on the data in order to check the validity of the recorded signals. It is recommended that the time history plots for all the recorded signals are developed and investigated for any possible spikes and outliers, prior to any type of analysis. Data validation and pre-processing of the data was done using MATLAB at the preliminary stages. MATLAB codes were generated in order to view the time history plots, take them into the frequency domain, and verify the data. Signal processing was performed in order to identify as many modes of vibration as possible. The data was decimated in different ways and data filtering with different orders was done to zoom into specific frequency bands in order to minimize the noise and identify the structural modes of vibration at each frequency range. Further processing, filtering, and modeling were done using ARTeMIS Modal Pro (SVIBS). As further explained in detail throughout the paper, the software ARTeMIS Modal Pro was utilized in order to perform the main signal processing, modal identification, and mode shape validation for the structure studied. Other software used in conjunction with the mentioned programs, would be MATCAD, EXCEL, and ConTEXT which were used for data handling, cleanup, and preliminary processing of the raw data. The Frequency Domain Decomposition (FDD) technique which decomposes the spectral density matrix at every frequency line using Singular Value Decomposition (SVD) was utilized in order to estimate the mode shapes and the natural frequencies based on the set of single degree of freedom (SDOF) systems for each mode. It is evident that the estimated modes can be grouped into the following types: structural modes, harmonics, and noise modes [2]. Investigation was done on the Singular Value Decomposition (SVD) graphs in order to identify the modes of the mentioned types and peak-picking method was performed in order to distinguish and select only the structural modes of vibration from the rest of the plotted frequency content. It was realized that the noise to signal ratio is much higher at higher frequencies such that distinguishing between the structural and noise modes becomes extremely difficult at frequencies higher than 16 Hz. Thus, the decimation and filtering algorithms were optimized to give the highest resolution possible up to 16 Hz and frequencies higher than 16 Hz were eliminated from the modal estimation.

4 F. Moayedi et al. Initially, Frequency Domain Operational Deflection Shapes (ODS) technique was used in order to scan the frequency domain for possible mode shapes. Then FDD, EFDD, and CFDD techniques were utilized in order to identify the specific natural frequencies by the peak-picking method. Finally, the same ODS method was performed in order to validate the deflected mode shapes. The following sections would present the results obtained using each mentioned technique. 1.4 Frequency Domain Decomposition (FDD) This technique approximately decomposes the response into a set of independent single degrees of freedom systems and performs singular value decomposition of the spectral density matrices. Table 1.1 summarizes the identified modal frequencies using this technique. The peak-picking process which resulted in the presented graph of the FDD technique is illustrated in Fig. 1.3. Table 1.1 Identified frequencies using the FDD technique Frequency (FDD) Mode complexity Mode no. Mode descriptions Hz % 1 First translational mode in the Y-direction 1.08 2.16 2 First translational mode in the X-direction 1.27 6.33 3 First torsional mode 1.83 10.14 4 Second translational mode in the X-direction 4.46 9.71 5 Second translational mode in the Y-direction 4.97 2.07 6 Second torsional 6.72 27.08 7 Third translational mode in the X-direction 9.68 74.47 8 Third torsional mode 11.45 21.23 9 Third translational mode in the Y-direction 12.03 30.95 10 Fourth translational mode in the Y-direction 15.01 56.68 11 Fourth translational mode in the X-direction 15.57 61.33 Fig. 1.3 Singular values of spectral density matrices of all test setups (FDD technique)

1 Determination of Modal Properties of an Irregular 20-Story Concrete Shear Wall Building 5 As it can be interpreted from the plot some of the peaks are not very well distinct. Thus, it might be almost impossible to identify them in one shot signal processing from the scratch. Therefore, some of the picked frequencies had been preidentified by zooming into smaller frequency ranges through filtering and decimation. Moreover, Frequency Domain ODS plots are developed and the “Toggle Cursor Mode” of ARTeMIS was activated in order to scan all the possible peaks in the frequency domain to identify building deformations representing any of the familiar mode shapes; frequencies of the specific peaks are recorded for further investigations through FDD techniques. The authors would like to suggest targeted investigations in each frequency band in order to pre-determine some of the possible natural frequencies, and then peak-picking becomes much easier when finalizing the results. 1.5 Enhanced Frequency Domain Decomposition (EFDD) The enhanced FDD adds a modal estimation layer which is divided into two steps. The first step is to perform the FDD Peak Picking, and the second step is to use the FDD identified mode shapes to identify the Single-Degree-Of-Freedom (SDOF) Spectral Bell functions and from these SDOF Spectral Bells estimate both the frequency and damping ratio. Table 1.2 contains the calculated frequencies and damping percentages for the identified modes of vibration from peakpicking done using the EFDD plot presented in Fig. 1.4 followed. Table 1.2 Identified frequencies using the EFDD technique Frequency (EFDD) Mode complexity Damping ratio Mode no. Mode descriptions Hz % % 1 First translational mode in the Y-direction 1.08 1.91 1.49 2 First translational mode in the X-direction 1.27 6.21 1.43 3 First torsional mode 1.83 9.73 1.07 4 Second translational mode in the X-direction 4.46 9.64 1.28 5 Second translational mode in the Y-direction 4.96 2.68 1.34 6 Second torsional 6.73 23.12 1.28 7 Third translational mode in the X-direction 9.63 64.85 0.00 8 Third torsional mode 10.90 36.11 0.00 9 Third translational mode in the Y-direction 12.04 36.29 0.00 10 Fourth translational mode in the Y-direction 15.01 56.68 0.00 11 Fourth translational mode in the X-direction 15.56 68.12 0.06 Fig. 1.4 Singular values of spectral density matrices of all test setups (EFDD technique)

6 F. Moayedi et al. Fig. 1.5 Singular values of spectral density matrices of all test setups (CFDD technique) Table 1.3 Identified frequencies using the CFDD technique Frequency (CFDD) Mode complexity Damping ratio Mode no. Mode descriptions Hz % % 1 First translational mode in the Y-direction 1.082 1.909 1.708 2 First translational mode in the X-direction 1.274 6.212 1.295 3 First torsional mode 1.825 9.729 0.912 4 Second translational mode in the X-direction 4.454 9.635 0.733 5 Second translational mode in the Y-direction 4.960 2.677 0.814 6 Second torsional 6.724 23.117 0.837 7 Third translational mode in the X-direction 9.625 64.847 0.000 8 Third torsional mode 11.635 50.371 0.347 9 Third translational mode in the Y-direction 11.958 26.685 0.000 10 Fourth translational mode in the Y-direction 15.000 60.562 0.000 11 Fourth translational mode in the X-direction 15.563 61.428 0.000 1.6 Curve-Fit Frequency Domain Decomposition (CFDD) The curve-fit FDD is similar to the EFDD estimation. The natural frequency and the damping ratio of the modes are estimated by curve fitting the SDOF Spectral Bell using frequency domain least-squares estimation, shown graphically in Fig. 1.5. Since the SDOF spectral bell is free of influence of other modes there is only a single eigenvalue and residue to fit. The natural frequency as well as the damping ratios are then extracted from the eigenvalues and are presented in Table 1.3. 1.7 Frequency Domain Operating Deflection Shapes (ODS) An Operating Deflection Shape or ODS is the deflection of a structure at a particular frequency relative to a specific point, also known as the driving point, on the structure. ODS analysis is used for determination of the vibration pattern of a structure under given operating conditions.

1 Determination of Modal Properties of an Irregular 20-Story Concrete Shear Wall Building 7 Fig. 1.6 Singular values of spectral density matrices of all test setups (FDODS technique) Table 1.4 Identified frequencies using the frequency ODS shape technique Frequency (FDODS) Mode complexity Mode no. Mode descriptions Hz % 1 First translational mode in the Y-direction 1.08 2.16 2 First translational mode in the X-direction 1.27 6.40 3 First torsional mode 1.83 9.78 4 Second translational mode in the X-direction 4.46 8.51 5 Second translational mode in the Y-direction 4.98 1.90 6 Second torsional 6.75 28.10 7 Third translational mode in the X-direction 9.67 47.72 8 Third torsional mode 11.46 23.07 9 Third translational mode in the Y-direction 12.08 28.63 10 Fourth translational mode in the Y-direction 13.17 39.70 11 Fourth translational mode in the X-direction 15.56 49.23 Before any modal estimation and after each modal identification, the ODS was done to confirm the validity of the deflected shape at the identified frequency. The final plot is shown in Fig. 1.6 and a summary of the frequencies identified by the FDODS technique is presented in Table 1.4. 1.8 Summary of Results The frequencies identified using the above techniques are all summarized in Table 1.5. As evident, the three methods are fairly similar in all of the identified modes of vibration. The frequencies, and their corresponding periods, of the structural modes of vibration identified using the FDD technique are compared against the values obtained from the ETABS model of the building. Table 1.6 summarizes the first ten modes from the ambient vibration measurements to the modes extracted from the ETABS model. 1.9 Mode Shapes The following mode shapes have been exported from ARTeMIS after the analysis of the data (Figs. 1.7, 1.8, 1.9 and 1.10).

8 F. Moayedi et al. Table 1.5 Summary of the natural frequencies from different FDD techniques Frequency (FDD) Frequency (EFDD) Frequency (CFDD) Mode no. Mode descriptions Hz Hz Hz 1 First translational mode in the Y-direction 1.08 1.08 1.08 2 First translational mode in the X-direction 1.27 1.27 1.27 3 First torsional mode 1.83 1.83 1.83 4 Second translational mode in the X-direction 4.46 4.46 4.46 5 Second translational mode in the Y-direction 4.97 4.96 4.98 6 Second torsional 6.72 6.73 6.75 7 Third translational mode in the X-direction 9.68 9.63 9.67 8 Third torsional mode 11.45 10.90 11.46 9 Third translational mode in the Y-direction 12.03 12.04 12.08 10 Fourth translational mode in the Y-direction 15.01 15.01 13.17 11 Fourth translational mode in the X-direction 15.57 15.56 15.56 Table 1.6 Modal periods and frequencies FEM period Measured period FEM frequency Measured frequency Mode no. s s Hz Hz 1 1.956 0.93 0.511 1.08 2 1.396 0.79 0.716 1.27 3 0.873 0.55 1.145 1.83 4 0.334 0.22 2.996 4.46 5 0.284 0.20 3.519 4.97 6 0.193 0.15 5.174 6.72 7 0.134 0.10 7.446 9.68 8 0.124 0.09 8.085 11.45 9 0.118 0.08 8.440 12.03 10 0.091 0.07 10.950 15.01 Fig. 1.7 Mode 1 – X direction (a) and Y direction (b)

1 Determination of Modal Properties of an Irregular 20-Story Concrete Shear Wall Building 9 Fig. 1.8 Mode 2 – X direction (a) and Y direction (b) Fig. 1.9 Mode 3 – X direction (a) and Y direction (b) 1.10 Discussion of Results System identification and modal characteristics of the reinforced concrete core building is determined by performing ambient vibration measurement tests using TROMINO® tri-axial transducers. As expected, the frequencies identified using the above techniques which are all summarized in the previous sections indicate that the measured natural periods of the building are approximately half the calculated natural periods derived from the ETABS model. This difference between the measured and the calculated results is due to the assumptions made in creating the FEM model such as not considering the effects of non-structural components on building stiffness. The modal properties of the building obtained from this experiment can be potentially used in FEM model updating. The authors of this paper would like to conclude that the utilized testing strategy would work very well for the building tested. The number of modes identified was beyond the expectation.

10 F. Moayedi et al. Fig. 1.10 Torsional modes – 1 (a), 2 (b), 3 (c) and4 (d) References 1. Ventura C, Schuster N (1996) Structural dynamic properties of a reinforced concrete high-rise building during construction. CJCE 23 pp. 950–972 2. Brincker R, Anderson P, Moller N (2006) An indicator for separation of structural and harmonic modes in output-only modal testing. IMAC XXIV 3. Brüel & Kjær (2013) Operating deflection shapes analysis. Struct Dyn

Chapter 2 Effect of Foundation Rocking on the Dynamic Characteristics of a 30-Story Concrete Shear Wall Building Salman Soleimani-Dashtaki, Ferya Moayedi, and Carlos E. Ventura Abstract The dynamic characteristics of a structure after the completion of its construction phase can be determined using ambient vibration measurement techniques. A newly constructed 30 stories tall reinforced concrete building in Burnaby, British Columbia, Canada, is tested using this technique. The experimental results reveal the dynamic characteristics of the investigated building including the building rocking and sliding at the foundation level. The method used is the advanced system identification using enhanced signal processing techniques based on the fundamentals of frequency domain decomposition. The paper expands on the technique, from the basics of the test setups to the details of the analysis. A total of 15 natural periods of vibration are successfully identified including the translational and torsional modes (up to mode 5). The modal estimation is performed using the techniques such as the Enhanced Frequency Domain Decomposition (EFDD), the Curve-fit Frequency Domain Decomposition (CFDD), and the Frequency Domain Operating Deflection Shapes (FDODS); and the outcomes are compared against each other. The modes found from the analytical ETABS models of the building at the structural design phase are then compared and calibrated against the obtained experimental results. Keywords Experimental techniques • Ambient vibration measurement • Modal estimation • System identification • Foundation rocking modes 2.1 Introduction The selected building for this experiment is a 30-storey concrete tower structure which sits on top of four levels of reinforced concrete underground parking. The building has a huge central core with four elevator shafts and staircases all the way from the parkade level up to the roof. There are concrete reinforced columns of 60 in. in diameter extending from the foundations all the way up to level 29. Columns get narrower with the height of the building, and at level 25 they reach a diameter of 30 in. The building in plan has a complex geometry with one round corner and straight edges at all other corners. This geometry is introducing some torsional irregularity to the tower, so the instrumentation is optimized to also capture the torsional modes to a good extent. The height of the parking levels are 2.9 m each, the height of the lobby is 4.9 m, and the height of all the other levels is approximately 3.7 m. The building is under the final stages of construction at the time when measurements are made; therefore construction noises are evident throughout the recorded signals. Figure 2.1 below shows an overview of the building and its typical floor plan. The dynamic characteristics of the building including its lateral and torsional mode shapes and natural periods of vibration are determined through ambient vibration measurements. S. Soleimani-Dashtaki ( ) University of British Columbia, Room 1012 D – 6250 Applied Science Lane, Vancouver, BC V6T 1Z4, Canada e-mail: salman@civil.ubc.ca F. Moayedi • C.E. Ventura University of British Columbia, Room 2018 – 6250 Applied Science Lane, Vancouver, BC V6T 1Z4, Canada © The Society for Experimental Mechanics, Inc. 2015 J. Caicedo, S. Pakzad (eds.), Dynamics of Civil Structures, Volume 2, Conference Proceedings of the Society for Experimental Mechanics Series, DOI 10.1007/978-3-319-15248-6_2 11

12 S. Soleimani-Dashtaki et al. Fig. 2.1 Photo of the investigated building (a) and one of its typical floor plans (b) 2.2 Experimental Phase By having a minimum of two transducers at each floor, most of the natural modes of vibration of the building are captured. In fact, having two sensors is required for identification of the torsional modes. In order to capture the dynamic characteristics of the building, a reference transducer is placed on the roof, located closely to the core of the building, and kept recording for the duration of the test, while the other transducers are moved around and relocated to different floors of the building. To monitor the velocity and acceleration of the structure, TROMINO®(Micromed) accelerometers were utilized to capture the characteristics of the building. The building is measured using 9 transducers, and in total, 10 setups were required to complete the measurements on all the floors. Each setup records for a duration of 40 min with the sampling rate of 128 Hz. It is worth mentioning that all transducers were set to record at 10 channels while connected to minimum 3 GPS satellites at a time during the measurements in all of the setups. Having the transducers acquire date, time, and location stamps from the GPS satellites allows for precise time synchronization between the devices, with accuracy of ˙0.001ms. Transducers are generally placed at opposing corners of the floor and record the movements in the X, Y, and Z directions. In this study, the translational modes in the NS and EW directions as well as the torsional modes of the building are of interest. Also, the building was instrumented all the way down to the foundation level, in order to detect the natural modes associated with the foundation rocking and sliding. The sketch shown in Fig. 2.2 illustrates the typical location of the transducers. 2.3 System Identification and Test Results The extraction of the data from the TROMINO®s is through the software Grilla®. The software converts the binary data recorded by the transducers to ASCII format which is preferable for data analysis. Prior to any extensive analysis, the time history plots are developed in order to check the validity of the recorded data and point out any outliers or spikes which may later manipulate the results. In general, data validation is done through a series of developed MATLAB codes.

2 Effect of Foundation Rocking on the Dynamic Characteristics of a 30-Story Concrete Shear Wall Building 13 Fig. 2.2 Sensor locations in a typical test setup Ref. Transducer Transducer Transducer The ARTeMIS Modal Pro (SVIBS) software is used in order to perform the main signal processing, modal identification, and the mode shape validation for the structure studied. Data is filtered and decimated to decrease the noise to signal ratio and increase resolution. Additionally, the Band Pass type Butterwort filters are used to zoom into specific frequency bands in order to investigate the peaks one by one and distinguish the structural modes of vibration at each frequency range. The results are finally combined into one optimized SVD plot containing the outstanding structural natural frequencies. The noise to signal ratio is greater in higher frequencies such that distinguishing between the structural and noise modes becomes extremely difficult at frequencies higher than 12 Hz. Thus, the decimation and filtering algorithms are optimized to give the highest resolution possible up to 12 Hz and frequencies higher than 12 Hz are eliminated from the modal estimation. Initially, Frequency Domain Operating Deflection Shapes (ODS) technique is used in order to scan the frequency domain for possible mode shapes. Then FDD, EFDD, and CFDD techniques are utilized to identify the specific natural frequencies by the peak-picking method. Finally, the ODS method is again performed in order to validate the deflected mode shapes. In addition to the mentioned techniques used in the system identification process, the modes considering rocking and sliding of the building foundation have been investigated using only the FDD method. The results obtained using each mentioned technique are compared and discussed in this paper, followed by a more extensive analysis presentation for the foundation rocking and sliding for the building. Also, the appendix of the paper includes a series of photos and diagrams illustrating the test setups as well as the identified mode shapes for the buildings. 2.4 Frequency Domain Decomposition (FDD) This technique approximately decomposes the response into a set of independent single degrees of freedom systems and performs singular value decomposition of the spectral density matrices [1]. The results of the processed data using the FDD technique are provided in Table 2.1.

14 S. Soleimani-Dashtaki et al. Table 2.1 Identified frequencies using the FDD technique Frequency (FDD) Mode complexity Mode no. Mode descriptions Hz % 1 First translational mode in the Y-direction 0.50 0.30 2 First translational mode in the X-direction 0.53 1.87 3 First torsional mode 0.94 4.26 4 Second translational mode in the X-direction 1.95 5.97 5 Second translational mode in the Y-direction 2.28 31.80 6 Second torsional 2.58 14.99 7 Third translational mode in the X-direction 3.73 28.23 8 Third torsional mode 4.61 14.35 9 Third translational mode in the Y-direction 5.19 42.21 10 Fourth translational mode in the Y-direction 5.61 27.35 11 Fourth torsional mode 6.63 50.98 12 Fifth translational mode in the X-direction 7.29 36.66 13 Fourth translational mode in the Y-direction 8.20 46.67 14 Sixth translational mode in the X-direction 8.41 60.90 15 Fifth torsional mode 10.04 78.28 Fig. 2.3 Singular values of spectral density matrices of all test setups (FDD technique) The singular values of the spectral density matrices of all test setups using the Frequency Domain Decomposition (FDD) technique are shown in the plot represented in Fig. 2.3. 2.5 Enhanced Frequency Domain Decomposition (EFDD) The Enhanced FDD adds a modal estimation layer which is divided into two steps. The first step is to perform the FDD Peak Picking, and the second step is to use the FDD identified mode shapes to identify the Single-Degree-Of-Freedom (SDOF) Spectral Bell functions and from these SDOF Spectral Bells estimate both the frequency and damping ratio. The following

2 Effect of Foundation Rocking on the Dynamic Characteristics of a 30-Story Concrete Shear Wall Building 15 Table 2.2 Identified frequencies using the EFDD technique Frequency (EFDD) Mode complexity Damping ratio Mode no. Mode descriptions Hz % % 1 First translational mode in the Y-direction 0:50 1:03 1:84 2 First translational mode in the X-direction 0:53 1:87 0:00 3 First torsional mode 0:94 2:26 1:08 4 Second translational mode in the X-direction 1:95 6:33 1:37 5 Second translational mode in the Y-direction 2:28 21:96 1:13 6 Second torsional 2:57 11:59 0:74 7 Third translational mode in the X-direction 3:74 25:43 1:27 8 Third torsional mode 4:61 8:81 1:32 9 Third translational mode in the Y-direction 5:18 30:11 1:15 10 Fourth translational mode in the Y-direction 5:60 23:28 1:13 11 Fourth torsional mode 6:61 48:69 0:00 12 Fifth translational mode in the X-direction 7:28 37:13 0:82 13 Fifth translational mode in the Y-direction 8:31 6:64 0:00 14 Sixth translational mode in the X-direction 8:44 53:22 0:00 15 Fifth torsional mode 10:14 76:44 0:00 Fig. 2.4 Singular values of spectral density matrices of all test setups (EFDD technique) table contains the calculated frequencies and damping percentages for the identified modes. The results of the processed data using the EFDD technique are provided in Table 2.2. The singular values of the spectral density matrices of all test setups using the Enhanced Frequency Domain Decomposition (EFDD) technique are shown in the plot represented in Fig. 2.4. 2.6 Curve-Fit Frequency Domain Decomposition (CFDD) The Curve-fit FDD is similar to the EFDD estimation. The natural frequencies and the damping ratios of the modes are estimated by curve fitting the SDOF Spectral Bell using frequency domain least-squares estimation.

16 S. Soleimani-Dashtaki et al. Table 2.3 Identified frequencies using the CFDD technique Frequency (CFDD) Mode complexity Damping ratio Mode no. Mode descriptions Hz % % 1 First translational mode in the Y-direction 0:50 0:30 0:00 2 First translational mode in the X-direction 0:53 1:87 0:00 3 First torsional mode 0:94 2:26 1:74 4 Second translational mode in the X-direction 1:95 6:33 0:96 5 Second translational mode in the Y-direction 2:28 21:96 0:85 6 Second torsional 2:57 11:59 0:46 7 Third translational mode in the X-direction 3:74 25:43 0:84 8 Third torsional mode 4:61 8:81 0:69 9 Third translational mode in the Y-direction 5:16 47:55 0:00 10 Fourth translational mode in the Y-direction 5:60 23:28 0:65 11 Fourth torsional mode 6:61 48:69 0:00 12 Fifth translational mode in the X-direction 7:28 37:13 0:44 13 Fourth translational mode in the Y-direction 8:31 6:64 0:00 14 Sixth translational mode in the X-direction 8:44 53:22 0:00 15 Fifth torsional mode 10:14 76:44 0:00 Fig. 2.5 Singular values of spectral density matrices of all test setups (CFDD technique) Since the SDOF spectral bell is free of influence of other modes, there is only a single eigenvalue and residue to fit. The natural frequencies as well as the damping ratios are then extracted from the eigenvalues and are presented in Table 2.3. The singular values of the spectral density matrices of all test setups using the Curve-fit Frequency Domain Decomposition (CFDD) technique are shown in the plot represented in Fig. 2.5 above.

2 Effect of Foundation Rocking on the Dynamic Characteristics of a 30-Story Concrete Shear Wall Building 17 2.7 Frequency Domain Operating Deflection Shapes (ODS) An Operating Deflection Shape or ODS is the deflection of a structure at a particular frequency relative to a specific point, also known as the driving point, on the structure. The results of the processed data using the ODS technique are provided here in Table 2.4 below. The singular values of the spectral density matrices of all test setups using the Frequency Domain Operating Deflection Shapes (ODS) technique are shown in the plot represented in Fig. 2.6 below. Table 2.4 Identified frequencies using the frequency ODS shape technique Frequency (ODS) Mode complexity Mode no. Mode descriptions Hz % 1 First translational mode in the Y-direction 0:50 10:52 2 First translational mode in the X-direction 0:53 1:87 3 First torsional mode 0:94 2:54 4 Second translational mode in the X-direction 1:95 6:32 5 Second translational mode in the Y-direction 2:28 26:47 6 Second torsional 2:58 12:03 7 Third translational mode in the X-direction 3:72 27:58 8 Third torsional mode 4:61 9:88 9 Third translational mode in the Y-direction 5:17 50:11 10 Fourth translational mode in the Y-direction 5:63 32:13 11 Fourth torsional mode 6:61 31:02 12 Fifth translational mode in the X-direction 7:30 41:94 13 Fourth translational mode in the Y-direction 8:31 84:50 14 Sixth translational mode in the X-direction 8:44 64:68 15 Fifth torsional mode 10:14 58:32 Fig. 2.6 Singular values of spectral density matrices of all test setups (FDODS technique)

18 S. Soleimani-Dashtaki et al. 2.8 Detecting the Foundation Rocking Components of the Modes An enhanced modal estimation was performed using the frequency domain decomposition technique in order to identify the frequencies at which the vibration modes represent foundation rocking. Since considerable rocking components are expected to be detected in the very first fundamental modes at lower frequency ranges, a different filtering and decimation approach is utilized in order to identify these specific mode shapes. For this purpose, only one of the measured test setups for this tall building is considered. Indeed, the only setup considered in this part of the study is a modified version of the test “Setup 8” which was recorded by 8 transducers all sitting on top of different foundations at the lowest parking level of the building. The locations of the main foundations are determined prior to the test, from the structural drawing sets. The FDD plot shown in the Fig. 2.7 below is obtained after passing a series of Band Pass type Butterworth filters, in increasing orders, over the data, with no decimations. Then the peak-picking method was performed again in order to identify the modal frequencies for the rocking and sliding of the foundation. In order to identify the proper mode shapes, the equations driving the building model in the ARTeMIS had to be modified such that a rigid body motion can be assumed throughout the height of the building. The data was filtered in different orders to minimize the noise content at the high frequency range. Table 2.5 below presents the modal frequencies obtained. Fig. 2.7 Singular values of spectral density matrices of the rocking test setup Table 2.5 Foundation rocking and sliding modes Frequency (FDD) Rocking Component Mode no. Rocking Component Hz Y/N 1 Foundation rocking in the Y direction 0.51 Yes (strong) 2 Foundation rocking in the X direction 0.53 Yes (strong) 3 Foundation rocking in the X-Y direction 0.93 Yes 4 Foundation rocking in the Y direction 1.94 Yes 5 Foundation rocking in the X direction 2.26 Yes 6 Foundation rocking in the X-Y direction 2.60 No 7 Foundation rocking in the X direction 3.72 Yes (weak) 8 Foundation rocking in the X-Y direction 4.60 No

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