IOMAC'13iomac.eu/iomac/2013/IOMAC_Guimaraes/files/papers/Structural... · 2012 the effect of the buildings supporting the Skywalk on its dynamic ... the Earthquake Engineering Research

IOMAC'13

5th International Operational Modal Analysis Conference

2013 May 13-15 Guimarães - Portugal

EVALUATION OF DYNAMIC CHARACTERISTICS OF

A PEDESTRIAN BRIDGE OVER A 15-YEAR PERIOD

USING OMA TECHNIQUES

Ilaria Capraro 1, Carlos Ventura,

2 Seku Catacoli

3

ABSTRACT

In the study reported in this paper OMA techniques have been used to determine how the dynamic

properties of a pedestrian bridge change over a 15-year period. The pedestrian bridge investigated is

located at the University of British Columbia, in Vancouver, Canada, and it is used to interconnect the

engineering building offices with the engineering laboratories. A number of tests have been conducted

at this bridge and the results from tests conducted in 1996, 2001 and 2011 are reported in this paper.

The Frequency Domain Decomposition (FDD) and the Stochastic Subspace Identification (SSI)

techniques have been used to analyze the recorded data. The modal frequencies, modal damping and

mode shapes from each test were compared and the variability of these values over the time period has

been investigated. At least twelve modes of vibration have been identified in each test. The results of

this study show that for this type of bridge the FDD method is much easier to use and provide more

reliable results than the SSI method. It was also found that the bridge structure is highly sensitive to

temperature effects, which makes the identification process rather challenging. In addition to the

ambient vibration tests, human-induced vibration tests have been conducted and the dynamic

properties obtained from these tests have been compared with those from the ambient vibration tests.

The speed of wave propagation has also been determined from these tests. Another aspect that has

been investigated is the effect of the dynamic properties of the two buildings that support the bridge on

the actual dynamic properties of the bridge.

Keywords: Pedestrian Bridge, Operational, Modal, Analysis, Human Vibrations

1. INTRODUCTION

In the present paper the comparative study over a 15-year period of the dynamic parameters of a

pedestrian bridge is presented. The experimental studies have been carried out on the footbridge at the

Civil and Mechanical Engineering Department at the University of British Columbia campus in

1 Ilaria Capraro, Graduate Student, University of Bologna, Bologna, Italy ([email protected])

2 Carlos E. Ventura, Department of Civil Engineering, The University of British Columbia, Vancouver, BC

Canada ([email protected]) 3 Seku Catacoli, Graduate student, Department of Civil Engineering, The University of British Columbia,

Vancouver, BC Canada ([email protected])

mailto:[email protected]



I. Capraro, C. E. Ventura, S. Catacoli

2

Vancouver. In order to obtain such dynamic characteristics, several ambient vibration tests have been

conducted by graduate students and different analysis techniques have been implemented. Ambient

vibration tests have allowed to identify natural frequencies, mode shapes and damping ratios. In this

paper are presented the results of analyses that refer to a period extending from 1996 to 2011. The first

tests have been conducted in April 1994 and April 2001 with the aid of the Hybrid Bridge Evaluation

System (HBES) developed at the University of British Columbia (Felber, 1993) (Ventura, Kharrazi,

Turek, & Horyna, 2002). The most recent ambient vibration test has been carried out in October 2011

and the analysis has been performed with the ARTeMIS software (A/S, n.d.). The modal analysis has

been done both with frequency domain (Frequency Domain Decomposition and Enhanced Frequency

Domain Decomposition) and time domain techniques (Stochastic Subspace Identification). In April

2012 the effect of the buildings supporting the Skywalk on its dynamic behaviour has been

investigated with a further ambient vibration measurement. A series of human-induced vibration

measurements has been performed in April 2012 in order to compare the natural frequencies with

those obtained through the traditional ambient measurements.

2. DESCRIPTION OF THE PEDESTRIAN BRIDGE

The CEME Skywalk is a welded steel pedestrian bridge located in Applied Science Lane at the

University of British Columbia campus in Vancouver, Canada. The footbridge connects the Civil and

Mechanical Engineering Building to the Rusty Hut, the Earthquake Engineering Research Facility

laboratory. The Skywalk can be schematized as a two-spans footbridge with uneven length of about

21.2 m and 35.8 m. The overall dimensions of this 3D beam are 2.44x2.75 m and It is built with square

hollow structural sections: HSS 127x127x5 mm for the two vertical trusses and HSS 76x76x5 mm is

used for the top and the bottom horizontal trusses (Kharrazi & Turek, 2001). The floor is composed by

a steel finished with concrete of variable depth, from 5 to 10 cm. As far as the boundary conditions are

concerned, the pedestrian bridge is supported in three locations along its length. In correspondence to

the Rusty Hut end, the Skywalk is restrained in the bottom part with a plate anchored to the stairwell

and the top chord is bolted to an anchorage device at the reinforced concrete stairwell through

oversized holes. The intermediate support consists of two HSS columns 7.6 meters high. The support

in correspondence of the CEME building is composed by a bearing pad on the bottom chord that

enables the longitudinal motion while plates guides allow some longitudinal and vertical motion and

the transversal one is restrained by the top chord.

Figure 1 Internal view of the Skywalk

3. AMBIENT VIBRATION TESTS

As the Operational Modal Analysis philosophy prescribes, the excitation forces acting on the structure

remain unknown during the ambient vibration tests and only the response of the walkway is measured.

Therefore the structure has been assumed to be excited by random and variable loads, such as wind,

5th International Operational Modal Analysis Conference, Guimarães 13-15 May 2013

3

traffic passing under the bridge and pedestrian passing through the Skywalk. In this case scenario, the

load can be defined as a multiple-input load and is really important when identifying mode shapes,

especially if closely-spaced ones (Brincker, Ventura, & Andersen, 2003).

The latest ambient vibration tests has been performed in October 2011. The test has been completed

using a total of five GeoSIG GSM-18 sensors. The GSM-18 is a wireless high sensitivity vibration

sensor. It uses a Real Time Clock (RTC) with self temperature compensation. The RTC is then

synchronized with GPS to provide high timing accuracy. The five sensors have been arranged in six

different configuration setups to get the data collected (Figure 2). Four out of five sensors were the so

called ‘roving’ sensors and have been shifted all along the span of the footbridge within the different

configurations, while the fifth sensor, that was the ‘reference’ one, has been placed in correspondence

to the point of maximum deflection, so close to the middle of the larger span. The sensors have been

all located at the bracing crossings and for sake of consistency the orientation has been kept constant

for all the configurations. The response measurements, accelerations in this case, have been recorded

for a long duration (20 minutes) so that the modes were excited enough to be all captured. The

sampling frequency was equal to 200 hertz.

Figure 2 Accelerometers locations and setups configuration

The structure has then been simplified to a strip and the collected data have been processed with

ARTeMIS software for the identification of the natural frequencies and mode shapes.

In order to obtain the natural frequencies of the structure, the average of the normalized values of the

spectral density matrices has been evaluated thanks to ARTeMIS (A/S, n.d.). The analysis has been

carried out with different techniques: the Frequency Domain Decomposition (FDD) has been applied

to have a first estimate of the natural frequencies and then the Enhanced Frequency Domain

Decomposition (EFDD) has been considered to get the estimation of the modal damping. To get a

further comparison parameter and for sake of completeness, the time domain technique, Stochastic

Subspace Identification (SSI), has been performed.

In (Figure 3) the Spectral Densities Matrices are represented in their normalized averaged singular

values and the selected peaks are highlighted. The analysis has been performed setting the number of

frequency lines to 1024.

Figure 3 Peak Picking: Average of the Normalized Values of the Spectral Density Matrices

In the 2011 analysis a total of fourteen modes have been identified up to a frequency of 30 hertz. In

order to have the confirmation that the peaks in the Average of the Normalized Values of the Spectral

Rusty

Hut

CEME

Bldg.


4

Density Matrices correspond to actual natural modes, the transfer function, coherence and phase angles

between all the sensors, roving and reference ones, have been computed. In (Table 1) a summary of

the natural frequencies and periods obtained during the 2011 analysis is presented (Capraro, 2012).

Table 1 FDD: results obtained from the 2011 analysis

MODE

SHAPE

FREQUENCY PERIOD

[Hz] [sec]

1 6.02 0.166

2 8.56 0.117

3 8.76 0.114

4 10.58 0.095

5 10.71 0.093

6 11.46 0.087

7 11.72 0.085

8 11.78 0.085

9 12.14 0.082

10 12.27 0.081

11 13.74 0.073

12 14.23 0.070

13 15.76 0.063

14 21.39 0.047

To give an example of what the final output look like, the representation of a couple of modes given

by ARTeMIS is presented in (Figure 4, 5 and 6). The modes are sketched in four different ways: the

3D view, the elevation, lateral and transverse view give us a full understanding of the behaviour of the

structure. For the majority of the modes, a sensible coupling with some torsional motion is present; in

some cases, especially at higher frequencies, the horizontal modes are fully coupled with the torsional

ones.

Figure 4 First Vertical Transverse Mode (1V) at 6.02 Hz


5

Figure 5 First Horizontal Mode (1H) at 8.56 Hz

Figure 6 Second Horizontal Mode (2H) at 8.76

The damping estimation for each mode has been evaluated thanks to the other frequency domain

technique: the Enhanced Frequency Domain Decomposition. The principle of the mode estimation is

basically the same of the FDD method and it is based on the peak picking technique. In (Table 2) the

comparison between the natural frequencies obtained with the FDD versus the EFDD as well as the

summary of the modal damping values is provided.

Table 2 2011 Analysis, results from the EFDD

MODE

SHAPE

FDD EFDD

FREQUENCY

[Hz]

FREQUENCY

[Hz]

DAMPING

[%]

1 6.02 6.01 1.30

2 8.56 8.57 0.47

3 8.76 8.66 0.57

4 10.58 10.57 0.17

5 10.71 10.70 0.18

6 11.46 11.46 0.16

7 11.72 11.72 0.22

8 11.78 11.78 0.14

9 12.14 12.13 0.16

10 12.27 12.27 0.23

11 13.74 13.73 0.13

12 14.23 14.13 0.11


6

13 15.76 15.75 0.11

14 21.39 21.39 0.08

In addition to the frequency domain techniques, the modal analysis has been performed also in the

time domain with the Stochastic Subspace Identification (SSI). In (Table 3) the final comparison of the

results is shown. The modal analysis has been carried out through the Unweighted Principal

Component (UPC) and the Principal Component (PC) methods.

Table 3 2011 Analysis: comparison of the frequencies with the different methods

MODE

SHAPE

FREQUENCY [Hz]

FDD EFDD SSI-UPC SSI-PC

1 6.02 6.01 6.02 6.05

2 8.56 8.57 - -

3 8.76 8.66 8.74 8.86

4 10.58 10.57 10.53 9.32

5 10.71 10.70 - -

6 11.46 11.46 11.33 10.67

7 11.72 11.72 - -

8 11.78 11.78 - -

9 12.14 12.13 - -

10 12.27 12.27 - -

11 13.74 13.73 13.85 14.01

12 14.23 14.13 - -

13 15.76 15.75 - -

14 21.39 21.39 21.27 21.27

This study confirmed how the time domain SSI techniques are not as user-friendly as the traditional

frequency domain techniques. The identification process with the SSI is more time-consuming and

complicated. Moreover, what catches the eye the most is that it hasn’t been possible to give an

estimation of all the modes, but less than half of them. In addition, it can be recognized that with the

two frequency domain techniques similar values of frequencies have been obtained, while there are

discrepancies, sometimes quite pronounced (as in mode 6 and 11), between frequencies computed with

the SSI and the FDD/EFDD. This inconsistency is found even between values of natural frequency

obtained with the same techniques operating in the time domain (mode 6, SSI-UPC and SSI-PC). This

particular structure has been proved to be very sensitive to temperature change (Ventura, Kharrazi,

Turek, & Horyna, 2002). This temperature effect may affect the values of the frequency obtained

through the SSI because the time domain techniques works directly with row data and so none

averaging process is applied to the recorded accelerations. Is therefore implied that, in this special

case, the frequency domain techniques are much more reliable and convenient to apply to perform the

modal analysis.


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4. COMPARISON OVER THE 15-YEAR PERIOD ANALYSES

The CEME Skywalk has been tested several times to obtain its dynamic characteristics. Experiments

have been carried out with different equipments. In April 1994 and April 2001 full ambient vibration

tests have been conducted with the aid of the Hybrid Bridge Evaluation System (HBES) that has been

developed at the University of British Columbia and the Vibration Analysis software program utilized

was DasyLab Version 5.01.10 (Felber, 1993). In 2001 two different ambient vibration tests have been

conducted: the first one to get the estimation of the natural frequencies and the mode shape, the second

one to investigate the frequency change with a temperature variation. The first test involved a total of

42 points along the Skywalk, while the second one just 10 points were measured. In the ambient

vibration test in 2011, only 22 points have been measured. An accurate description of the sensors

location and the vibration data acquisition system used in 2001 can be found in (Kharrazi & Turek,

2001) while information on the study conducted in 1994 are presented in (Horyna, 1994). It is

important to mention that, unlike tests in 2011, the sensors used in the previous tests were not wireless.

The comparison between the results of the different analyses can be shown in (Table 4). It is evident

how the 2011 analysis has been able to identify more modes than the previous ones. In particular, it

has been possible to have a better estimation of what the horizontal modes are. In addition to that, it

can be recognized that the pattern in which the modes appear is somehow repetitive as the frequency

increases.

Comparing the analyses made in 1996, 2001 and 2011, the maximum difference between frequency

values for a given mode is observed to be 1.33 Hz in correspondence of the first torsional mode

between the 1996 and 2011 analysis and 1.33 Hz for the second torsional mode between the 1996 and

2001 study. The minimum difference has been computed for the third torsional mode. An average of

0.39 hertz in the natural frequency values can be observed accounting for the entire 15-year period

analyses.

Table 4 Comparison of Natural Frequencies along the 15-year period analyses

Mode

Frequency [Hz]

Description obtained

1996

obtained

2001

obtained

2011

1 6.05 5.76 6.02 First Vertical Transverse (1V)

2 - 8.01 - First Vertical Transverse coupled with Torsion (1V+1T)

3 - - 8.56 First Horizontal coupled with Torsion (1H)

4 8.50 8.89 8.76 Second Horizontal coupled with Torsion (2H)

5 - - 10.58 First Torsional coupled with Longitudinal Motion (1T)

6 9.38 10.62 10.71 First Torsional (1T)

7 11.96 12.08 11.46 Second Vertical Transverse (2V)

8 - - 11.72 First Horizontal fully coupled with First Torsional (1H + 1T)

9 10.45 11.78 - Second Torsional (2T)

10 - - 11.78 First Horizontal fully coupled with Second Torsional (1H + 2T)

11 - - 12.14 Second Horizontal fully coupled with First Torsional (2H + 1T)

12 - - 12.27 Second Horizontal fully coupled with Second Torsional (2H + 2T)

13 13.77 13.79 13.74 Third Torsional (3T)

14 13.96 14.34 14.23 Third Horizontal fully coupled with Third Torsional (3H + 3T)


8

15 14.94 14.71 - Third Vertical Transverse (3V)

16 - - 15.76 Third Horizontal fully coupled with Fourth Torsional (3H + 4T)

17 - 16.37 - Fourth Vertical Transverse (4V)

18 20.46 20.51 21.39 Fourth Horizontal fully coupled with Fourth in Torsion (4H + 4T)

19 - 28.44 - Fifth Horizontal fully coupled with Torsional (5H + 4T)

5. THE SUPPORTING BUILDINGS EFFECT ON THE DYNAMIC BEHAVIOUR

OF THE SKYWALK

In order to find some correlations between the presence of some peaks at low frequencies (Figure 7) in

the average of the normalized values of the spectral densities matrices and a probable presence of

natural frequencies in the two supporting buildings, ambient vibration tests have been carried out by

recording data through two sensors placed in the CEME building and in the Rusty Hut. Through an

ARTeMIS model and setting the spectral densities to 512 it has been possible to analyze data collected

by to two sensors. A very strong peak around 6 Hz has been recognized in both building in

confirmation of the presence of the fundamental frequency of the Skywalk. Other two peaks around

3.71 Hz (Figure 9) at the CEME building and 2.54 Hz (Figure 8) at the Rusty Hut reflect the presence

of non fundamental peaks in the Skywalk analysis. It is possible that those values correspond to

fundamental modes of the two supporting buildings and that they influence the diagram of the Spectral

Density Matrices of the Skywalk.

Figure 7 2011 Analysis: Suspicious peaks in the FDD

Figure 8 Channel 5, possible peak at 2.54 Hz frequency


9

Figure 9 Channel 2, possible peak at 3.71 Hz frequency

6. HUMAN-INDUCED VIBRATIONS TESTS

Human-induced loads are known to be fundamental in the design of a pedestrian bridge: in this case

the serviceability issue can assume a more important role than those levels of vibration sufficient to

cause damage to the structure. There are several guidelines and design requirements that have been

established to avoid the problem of vibrating footbridges. For example, the Ontario Highway Bridge

Design Code (OHBDC) sets a threshold on the lowest natural frequency to be not less than 4 Hz (J.H.

Ranier, August 12-21, 1986). In 2009, the ASSHTO LRFD Guide Specifications for the Design of

Pedestrian Bridges (AASHTO, 2009) state that to avoid the first harmonic the fundamental frequency

in a vertical mode of a pedestrian bridge shall be greater than 3 Hz, while in the lateral direction, the

first natural frequency should be greater than 1.3 Hz. According to the results obtained from the

ambient vibration test, the CEME Skywalk respects these limits in both directions.

A series of human-induced vibration tests has been carried out in April 12th in order to see how the

CEME Skywalk responds to different sources of human excitation. Four sensors were available and

have been located all along the span of the footbridge with a equally-spaced pattern of about 19 m.

The details about the type of test and its recording duration is summarized in (Table 5).

Table 5 Summary of the Human-Induced Vibration Tests

Test Excitation Source Recording Duration [sec]

2 Jump impulse at CEME end 120

3 Jump impulse at middle length 120

4 Jump at both ends 120

5 Walking at normal speed 60

6 Walking fast 60

7 Marching 120

8 Running 60

The sampling frequency for each test was equal to 200 Hz. Moreover, for each test, an ARTeMIS

model has been built to perform the different analyses.

The wave propagation velocity has been calculated for Test 2 and 3, where the jumping excitation was

involved. Accounting for the longitudinal channels only, the velocity of the compression wave has

been estimated to be 396 and 276 m/sec respectively. Of course the value of the propagation velocity

depends on the intensity of the applied load, that is the jumping load in this case.

For each human-induced vibration test a Frequency Domain Decomposition has been performed in

order to see if the significant peaks of the Spectral Densities share similar values. For these analyses,

the number of frequency lines has been set to 512 and the Nyquist frequency to 100 Hz. A summary of


10

the significant frequencies values is provided in (Table 6). It is evident that some peaks below the

fundamental frequency are present in almost all the tests. Common values are at about 3.5 and 8.2 Hz

and very often, a peak around 13.6 Hz. In particular, it can be recognized that the exact same peak

appears at 0.98 Hz in Test 5 and Test 6. The reason behind this equivalence could be because the two

tests are related to a similar excitation source: walking and walking fast.

Table 6 Summary of the significant frequencies obtained with the human-induced vibration tests

TEST ID. SIGNIFICANT FREQUENCIES [Hz]

Ambient

Vibration 6.02 8.56 8.76 10.58 10.71 11.46 11.72 11.78 12.14 12.27 13.74 14.23 15.76 21.39

Test 2 3.52 6.06 8.20 10.74 13.67 14.26 15.82 18.95

Test 3 3.52 6.25 9.77 14.06 15.23 16.80 24.22

Test 4 5.86 8.20

Test 5 0.98 1.95 2.83 3.81 5.66 7.62 8.30 10.64 12.30 13.67 14.16 15.53 16.50

Test 6 0.98 2.34 3.52 4.49 5.66 8.40 13.67 15.63 16.60

Test 7 1.95 3.71 5.66 7.42 8.20 9.38 11.33 13.09 15.04 16.60

Test 8 3.52 5.86 8.20 9.96 15.63 16.99 25.20

As it can be proved plotting all these frequency values in (Figure 10), it is clear how the ambient

vibration test are much better than the performed human-induced vibration tests in capturing the

closely-spaced modes. Anyway, there is a common pattern regarding the fundamental mode: all the

test present a peak very close to the fundamental frequency. To have a clear understanding of the

distribution of the frequencies around the first mode a diagram of these values is presented in (Figure

11) where the first natural frequency is sketched as a baseline and the natural frequencies of the other

tests corresponding to the first mode are represented by single dots. The error estimation on the

evaluation of the fundamental frequency can be easily computed as the its variation respect to the first

mode. A relatively small error can be accounted with Test 1 (0.55%). The estimation turns out to be

pretty rough in the other tests, with errors that reach values of 5.94% in the estimation of the

fundamental frequency.


11

Figure 10 Summary of the significant frequencies obtained in the different human-induced vibration tests

Figure 11 Comparison between fundamental frequencies obtained with the different tests

7. CONCLUSIONS

The ambient vibration test conducted in 2011 on the CEME Skywalk have highlighted fourteen modes

up to a frequency of 30 hertz. The fundamental mode correspond to a first vertical mode in the

transverse direction in correspondence to a frequency of 6.02 Hz, while the first horizontal mode is at

8.51 Hz and the first torsional mode appears uncoupled at 10.71 Hz. A strong coupling with the

torsional motion is present in most of the modes, especially at higher frequencies and above all when

the horizontal modes are concerned.

Among all the possible techniques, the FDD has been proved to be the best choice to perform the

Operational Modal Analysis, because it reveals to be faster and user-friendly than the time domain

0 5 10 15 20 25

Tes

t

Frequency [Hz]

Significant Frequencies Summary

Ambient Vibration Test Test_2 Test_3 Test_4 Test_5 Test_6 Test_7 Test_8

6,02 6,25 5,86 5,66 5,66 5,66 5,86

0

1

2

3

4

5

6

7

2 3 4 5 6 7 8

Fre

qu

ency

[H

z]

Test I.D.

Significant Frequencies vs. Fundamental Frequency

Ambient Vibration Test_2 Test_3 Test_4 Test_5 Test_6 Test_7 Test_8


12

techniques (SSI). In addition, the SSI method has not been able to capture all the modes. In fact only

six out of the fourteen modes have been identified.

Through another ambient vibration test, it has been possible to investigate the influence of the two

buildings supporting the CEME Skywalk on the Spectral Density Matrices plots. It has been shown

that there is some correspondence between peaks on the Skywalk and on the CEME building and

Rusty Hut results. To have the confirmation of this analogy, a further investigation of the whole

dynamic behavior of these buildings supporting the footbridge.

The wave velocity propagation has been calculated for a couple of tests and its order of magnitude

range between 350 and 400 m/sec, the specific intensity will depend on how strong is the source force

applied. The FDD performed on the data collected with the human-induced vibration tests shows that

it is possible to have a rough estimate of the first natural frequency, even if with a certain error.

Moreover, It can be recognized that closely-spaced modes are not captured as well as during the

Ambient vibration testing. The study confirmed also how the Skywalk meets the conditions set by

guidelines on the first natural frequency in the vertical and in the horizontal direction to avoid

serviceability problems of vibrating bridges.

ACKNOWLEDGEMENTS

The authors wish to acknowledge the Earthquake Engineering Research Facility of the University of

British Columbia in Vancouver, the Natural Sciences and Engineering Research Council of Canada

(NSERC) and the Department of Civil, Chemical, Environmental and Materials Engineering (DICAM)

of University of Bologna.

REFERENCES

[1] A/S, S. V. (n.d.). www.svibs.com. Retrieved August 8, 2012, from Software for Operational

Modal Analysis

[2] AASHTO (2009) LRFD Guide Specifications for the Design of Pedestrian Bridges

[3] Brincker, R., Ventura, C. E., & Andersen, P. (2003) Why Output-Only Modal Testing is a

Desirable Tool for a Wide Range of Practical Applications. Proceedings of IMAC XXI

Kissimmee, Florida

[4] Capraro, I. (2012) Operational Modal Analysis: the CEME Skywalk at UBC, Vancouver.

Bologna: University of Bologna.

[5] Felber, A. (1993) Development of a Hybrid Evaluation System. Vancouver: University of British

Columbia, Department of Civil Engineering.

[6] Horyna, T. (1994) Experimental Model Analysis of the Skywalk Between CEME and the Rusty

Hut of UBC. Civil 508 Term Project, University of British Columbia, Canada.

[7] J.H. Ranier, G. P. (August 12-21, 1986). Dynamic Loading and Response of Footbridges.

Proceedings of the II International Conference on Short and Medium Span Bridges. 2, p. 335-

347. Ottawa, ON: National Research Council Canada.

[8] Kharrazi, M. H., & Turek, M. (2001). Ambient Vibration Measurements of Skywalk Between

CEME and the Rusty Hut at UBC. Vancouver, Canada: U.B.C. Earthquake Engineering Research.

[9] Ventura, C. E., Kharrazi, M. H., Turek, M., & Horyna, T. (2002). Dynamic Analysis of A

Pedestrian Walkway, University of British Columbia, Canada. Proceedings of XX IMAC, (p. 114-

119). Los Angeles, California.

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IOMAC'13iomac.eu/iomac/2013/IOMAC_Guimaraes/files/papers/Structural... · 2012 the effect of the buildings supporting the Skywalk on its dynamic ... the Earthquake Engineering Research