Sushil Ghimire Candidate Civil Engineering Department This thesis is approved, and it is acceptable in quality and form for publication: Approved by the Thesis Committee: Dr. Walter Gerstle , Chairperson Dr. Fernando Moreu Dr. Majeed Hayat STUDY OF VIBRATION FOR DETECTION AND RECOGNITION OF CONCEALED MACHINERY WITHIN BUILDINGS by SUSHIL GHIMIRE BACHELOR’S DEGREE IN CIVIL ENGINEERING TRIBHUVAN UNIVERSITY, NEPAL THESIS Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science Civil Engineering The University of New Mexico Albuquerque, New Mexico March, 2017 Dedication To my father and mother Ambika Prasad Ghimire and Durga Kumari Koirala Ghimire, my brother, Ashish Ghimire, my advisor Dr. Walter Gerstle, and my beloved friend, Bidyah Dahal, for their encouragement and support. iii Acknowledgements I am heartily thankful to Dr. Walter Gerstle, my advisor and committee chair, for giving me opportunity to work with him. This research is possible because of his continuous support, guidance, and encouragement. I am thankful to the funding agency. This work is supported by the United States Department of Energy, Award No. DE-NA0002484. I am extremely thankful to my parents for their encouragement and undoubted confidence in me. I would like to thank Dr. Majeed Hayat and Dr. Fernando Moreu for being in my thesis committee member and Dr. Thomas Paez for reviewing my thesis. I would also like to thank my colleagues, Francisco Pérez, Krishna Chaitanya Jagadeesh, and Jose Alberto Gomez for their help and support. iv STUDY OF VIBRATION FOR DETECTION AND RECOGNITION OF CONCEALED MACHINERY WITHIN BUILDINGS by Sushil Ghimire B.S., CIVIL ENGINEERING, TRIBHUVAN UNIVERSITY, NEPAL, 2014 M.S., CIVIL ENGINEERING, UNIVERSITY OF NEW MEXICO, USA, 2017 ABSTRACT Recently international concern about nuclear proliferation has rapidly increased. Some governmental agencies have an interest in remotely detecting and recognizing concealed machinery within buildings to detect any anomalous activity occurring inside the building. The vibration studies of the roof and the exhaust structures of an existing utility building, the Ford Utility Center at the University of New Mexico and a simplified laboratory structure representing an industrial building, called the doghouse are presented in this thesis. The vibration studies presented allow the reader to understand to what extent it is possible to identify machines concealed within a building. To identify machines concealed within a complex building like the Ford Utility Center, we preferred first to better understand the vibration of a simplified structure due to concealed machinery. Thus, in this thesis, we first study the vibration of the doghouse, and then study the vibration of the Ford Utility Center. v Table of Contents List of Figures ....................................................................................................... ix List of Tables ...................................................................................................... xiv Chapter 1 Introduction ...................................................................................... 1 1.1. Motivation ............................................................................................... 1 1.2. Scope of thesis ........................................................................................ 2 1.3. Outline of thesis ...................................................................................... 3 Chapter 2 Literature Review ............................................................................ 5 2.1. Introduction ............................................................................................. 5 2.2. Vibration measurement and analysis ...................................................... 6 2.3. Identification of concealed machinery by vibrations .............................. 6 2.4. Nonlinearity in structural vibration ......................................................... 8 2.5. Displacement time history of vibration ................................................... 9 2.6. Summary ............................................................................................... 10 Chapter 3 Data Acquisition Process and Sensitivity of Accelerometer....... 12 3.1. Introduction to the data acquisition process .......................................... 12 3.2. Components of data acquisition process ............................................... 13 3.3. Sensitivity of the accelerometer ............................................................ 15 3.4. Summary ............................................................................................... 20 Chapter 4 Displacement Reconstruction from Measured Acceleration ..... 22 4.1. Introduction ........................................................................................... 22 vi 4.2. Time domain method of displacement reconstruction .......................... 23 4.3. Error using the time domain method .................................................... 25 4.4. Frequency domain method of displacement reconstruction ................. 28 4.5. Introduction of high pass filter .............................................................. 31 4.6. Summary ............................................................................................... 33 Chapter 5 Free Vibration Study of the Doghouse ......................................... 34 5.1. Introduction ........................................................................................... 34 5.2. Description of the laboratory structure ................................................. 36 5.3. Finite element analysis .......................................................................... 41 5.4. Experimental analysis ........................................................................... 44 5.5. Summary ............................................................................................... 47 Chapter 6 Refined Vibrational Models of the Doghouse .............................. 49 6.1. Introduction ........................................................................................... 49 6.2. Nonlinearity .......................................................................................... 50 6.3. Nonlinearity based on the deformations of an elastic plate .................. 52 6.4. Laboratory tests of the doghouse .......................................................... 53 6.5. Finite element analysis of the doghouse ............................................... 59 6.6. Summary ............................................................................................... 64 Chapter 7 Identification of Motors Concealed within the Doghouse .......... 66 7.1. Introduction ........................................................................................... 66 7.2. Linear dynamics .................................................................................... 67 7.3. Linear forced vibration analysis............................................................ 69 7.4. Laboratory tests of the doghouse .......................................................... 74 vii 7.5. Summary ............................................................................................... 77 Chapter 8 Vibration Study of the Ford Utility Center ................................. 78 8.1. Introduction ........................................................................................... 78 8.2. Ford Utility Center ................................................................................ 79 8.3. Vibration signatures of the roof ............................................................ 82 8.4. Summary ............................................................................................... 87 Chapter 9 Conclusions ..................................................................................... 88 9.1. Summary ............................................................................................... 88 9.2. Major findings ....................................................................................... 89 9.3. Future research ...................................................................................... 90 References ............................................................................................................ 92 viii List of Figures Fig. 2.1. a) Top hat chimney reflector. b) Top view of the chimney, with C 4x6.25 channel weights and a motor with off balance mass shown (Pérez, Campbell et al. 2016). .......................................................................................................................... 7 Fig. 3.1. Schematic of our data acquisition process using national instruments hardware NI- DAQ) and Software (LabVIEW)........................................................................ 12 Fig. 3.2. Functional diagram of piezo-electric accelerometer .......................................... 13 Fig. 3.3. Experimental setup with two accelerometers and a hydraulic actuator. ............. 16 Fig. 3.4. Time history and magnitude spectrum of the hydraulic actuator measured by accelerometer1 .......................................................................................................... 17 Fig. 3.5. Magnified picture of Fig. 3.4. ............................................................................. 18 Fig. 3.6. Time history and magnitude spectrum of the hydraulic actuator measured by accelerometer2. ......................................................................................................... 19 Fig. 3.7. Magnified picture of Fig. 3.6. ............................................................................. 20 Fig. 4.1. Time history of reconstructed velocity and displacement from acceleration measured on the hydraulic actuator using time domain method of reconstruction. . 24 Fig. 4.2. Time history of reconstructed velocity and displacement from acceleration measured on the chimney using time domain method of reconstruction. ................. 24 Fig. 4.3. Time history of sinusoidal waveform of unit amplitude and frequency of 2 Hz and its integrated waveform. ..................................................................................... 26 Fig. 4.4. Time history of sinusoidal waveform of unit magnitude and frequency of 20 Hz and its integrated waveform. ..................................................................................... 26 ix Fig. 4.5. Time history of multi frequency sinusoid and its integrated waveform. ............ 27 Fig. 4.6. Time history of reconstructed displacement from acceleration measured on the hydraulic actuator using frequency domain method. ................................................ 30 Fig. 4.7. Time history of reconstructed displacement from acceleration measured on the chimney actuator using frequency domain method. ................................................. 30 Fig. 4.8. Fourier transform of acceleration time history of the chimney. ......................... 31 Fig. 4.9. Reconstructed displacement of chimney using high pass filter on frequency domain method. ......................................................................................................... 32 Fig. 5.1. Damped spring-mass-system. ............................................................................. 34 Fig. 5.2. Construction drawings of the doghouse. ............................................................ 37 Fig. 5.3. Construction drawings of the doghouse. ............................................................ 38 Fig. 5.4 Construction drawings of the doghouse. ............................................................. 39 Fig. 5.5. Doghouse. ........................................................................................................... 40 Fig. 5.6. Connection of chimney with roof and walls. Front wall removed. .................... 40 Fig. 5.7 Finite element model of the doghouse using SAP2000. ...................................... 41 Fig. 5.8. First mode of vibration of the doghouse using SAP2000. .................................. 43 Fig. 5.9. Second mode of vibration of the doghouse using SAP 2000. ............................ 43 Fig. 5.10. Experimental setup to measure free vibration of the chimney. ........................ 44 Fig. 5.11. Damped free vibration time history, and magnitude spectrum of chimney of the doghouse, measured by the accelerometer. ............................................................... 45 Fig. 5.12. Experimental setup to measure the free vibration of the roof. ......................... 46 Fig. 5.13. Damped free vibration time history and magnitude spectrum of roof of the doghouse, measured by accelerometer...................................................................... 47 x