The Dynaseis experiment ELSA, JRC Ispra Italy 2003 Monitoring of the dynamic behaviour of a building...

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ELSA, JRC Ispra Italy

2003

Monitoring of the dynamic behaviour of a building at

Parque das Nações Lisboa

Instituto Superior de Engenharia de Lisboa

Maria Ana Baptista

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Project funded by the Portuguese Science Foundation (FCT)

DYNASEIS - DYNAMIC BEHAVIOUR OF A RE–INFORCED CONCRETE STRUCTURE UNDER SEIMIC LOAD

MAIN OBJECTIVES

• Study of dynamic response of a re-inforced concrete structure using ambient vibrations (“output only”)

•Experimental study of natural frequencies

•Implementation of numerical modelling of the structure

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The Building ofPortugal Telecom Offices

Located at the newly residential and office area of Lisboa, calledParque das Nações (Expo98)

Built in 1998Area 11 000 m2

TARGET

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The Tower has 12 floors above ground and four basement levels, and is responsible for the entire telecommunications network in the “Parque das Nações” complex (Expo ’98).

Two floors are entirely occupied by the telecom central, being the remaining floors used by Marconi (PT subsidiary) as their head-office.

TARGET

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TARGET

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1. Forced-vibration tests are more difficult to perform and require heavy equipment and logistics;

2. State-of-the-art vibration generators do not have the capability to excite to resonance all significant modes of all structures (Çelebi,2000);

3. Different vibrational modes can be detected from a single measurement;

4. Forced vibrations can damage the structure.

However,

1. Modal characteristics corresponding to low amplitude vibrations may be different from large higher levels of shaking (Ventura & Schuster, 1996).

WHY AMBIENT VIBRATION TEST ?

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The Telecom Tower is located close to the Gare do Oriente railway station (designed by Santiago Calatrava) and is one source of ambient noise).

AMBIENT VIBRATION TEST

Others are urban traffic, wind, etc...

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DYNAMIC MODELLING

Dynamic analysis was performed by the designers of the structure but the information available is scarce.

The building is a reinforced concrete structure consisting of “boat shape” flat plate slabs.

•floor slabs are 0.25 m thick (floors 5 to 11), 0.30 m (floors 1 to 4) and 0.40 m (ground floor);

• floor slabs are directly support by columns;

• analysis were conducted up to 8 modes but only the first 6 were considered relevant;

• fundamental frequency: 0.55 Hz;

Exterior Support beam

For lifts and windows

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INSTRUMENTS - SENSORS

Dynamic Range 155 dB

Frequency Band DC to 200 Hz

Scale Amplitude 0,25g a 4,00g

Dynamic Range 140 dB

Frequency Band DC to 200 Hz

Scale Amplitude 0,25g a 4,00g

Uniaxial Acelerometer Episensor FBA ES-U:

Triaxial Acelerometer Episensor FBA ES-T:

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6

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INSTRUMENTS - ACQUISITION

Dynamic Range > 114 dB

Sampling Rate 20 a 200 Hz

Output 24 bit

Acquisition Mode Contínuous/Trigger

Clock GPS (accuracy 0,5 ms)

Acquisition System: Kinemetrics Altus K2 Digital Recorder:

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FIRST TEST

Field Operations: 30 December 2002

Triaxial: Top Floor (fixed)

Continuous 10 min observations in all even floors with the following geometry:

Reference Sensors

Roving Sensors

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Sampling Rate – 250 Hz

Channels

• 1,2,3 – (x,y,z) triaxial reference acelerometer

• 4 – y direction south tower

• 5 – x direction south tower

• 7 – x direction north tower

Time base – TU (sinal GPS)

Scale 2,5 V/1g

FIRST TEST

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FIRST TEST

Cables were deployed along the floors ...

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Successive setups (30.12.2002):•Floor_10•Floor_08•Floor_06•Floor_04•Floor_02

FIRST TEST

To maintain a good quality control the sensor layout was kept the same when moving from setup to setup.

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FIRST TEST

Example of event record from setup 6.

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ESD obtained by FFT

Triaxial record on the top floor

y direction

x direction z direction (vertical)

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Event recorded at the 6th floor:

A – transversalB – longitudinalC – longitudinal

ESD obtained by FFT A

B

C

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Successive setups 24.012003:•Floor_11•Floor_07•Floor_05•Floor_03•Floor_01 - closed

FIRST TEST

Field Operations: 24 January 2003

Triaxial: Top Floor (fixed)

Continuous 10 min observations in all uneven floors with the following geometry:

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• free-field station: it is impossible to locate a free-field station at a distance greater than 1.5 - 2 times the height of the nearest/tallest building (Çelebi, 2000);

6 HOUR CONTINUOUS ACQUISITION10 February 2003 and 11 February 2003

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• continuous observation can be achieved only in the following places: 11th, 6th, 0th floors

• triaxial accelerometer at floor – 4 (foundation level)


Data Acquisition – 6 hours Sampling rate 100Hz

Data is stored in a PCMCIA 64 MB

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Data acquisition system K2 was installed at 6th floor

Connection of the transverse and logintudinal sensors to the junction box that is connected to k2 and after that

The sensors were oriented parallel to the tranverse (x) and longitudinal (y) axes of the building


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• Conclusion of the Finite Element Modeling (FEM) of the building – SAP2000 in order to avoid definitive installation at nodal points of the structure;

• Experimental data analysis: Modal analysis – ArteMis;

• Validation of dynamical analysis

• Improvement of the methodology: - in earthquake prone areas - different building typology

NEXT ACTIVITIES

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ACKNOWLEDGMENTS

The author wish to thank the Portuguese Telecom Board of Administration and LNEC (Laboratório Nacional de Engenharia Civil) for all support.

DYNASEIS TEAM: M. A. Baptista, A. Campos Costa, A. Afilhado, C. S. Oliveira, P. Mendes, M. Vasques

This project was funded by Portuguese Science Foundation (FCT) project POCTI-36071-ECM

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REFERENCES

Çelebi M., 2000 Seismic Instrumentation of bulidings, USGS OF report 00157

Ventura & Schuster, 1996 d Structural dynamic properties of a re inforced high rise building during construction. Can. J. Civil Eng 23,950-970.

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STRUCTURAL RESPONSE

VibrationExcitation

Frequency range

Hz

Displ.range

µm

VelocityRangemm/s

Accel.Range

µg

Traffic: road, rail 1 - 80 1 - 200 0.2 - 50 2 - 100

Wind 0.1 - 10 10 - 105

Earthquakes 0.1 - 30 10 -105 0.2 - 400 2 - 200

Acoustic: traffic and machinery outside

10 - 250 1 - 100 0.2 - 30 2 - 100

Machinery inside 1 - 1000 1 - 100 0.2 - 30 2 - 100

Adapted from ANSI: S247 - 1990

The Dynaseis experiment ELSA, JRC Ispra Italy 2003 Monitoring of the dynamic behaviour of a building...

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