MEMSCON Workshop

1. MEMSCON Workshop Structural Monitoring and Status-Dependent Maintenance and Repair of Constructed Facilities 7 October 2010, Bucharest, Romania Integrated Structural Health Monitoring Systems for BuildingsDaniele Inaudi, CTO Roctest GroupRoberto Walder, Sales Manager SMARTEC SA

2. An Overview • SHM Benefits • 7 STEPS SHM Methodology • SHM of Buildings • Case Study • Conclusions

3. SHM Benefits • Monitoring reduces uncertainty and unknowns • real state of materials, real loads, structure ageing → right decisions and reduce insurance costs • Monitoring discovers hidden structural reserves • an increase in the safety margins and extend the lifetime without intervention • Monitoring discovers deficiencies in time and increases safety • preventive actions for deficiencies that cannot be identified by visual inspection have to be taken before it’s too late → repairs are cheaper if done at the right time • Monitoring insures long-term quality • assess quality during construction, operation, maintenance and repair • Monitoring allows structural management • Maintenance/inspection on-demand • optimize operation, maintenance, repair based on objective data • Monitoring increases knowledge • learning how structures perfom in real conditions • design better structures for the future.

4. 7 STEPS SHM Methodology • Identify structures needing monitoring • Acquire information on probable risks and opportunities from design engineers or owners • Establish expected responses • Design SHM system to detect such responses and select appropriate sensors • Install and calibrate system • Acquire and manage data • Asses field data.

5. STEP 1: Indentify Structures • New structures including innovative aspects • New structures with unusual associated risks or uncertainties, including geological conditions, seismic risk, meteorological risk, aggressive environment, vulnerability during construction, quality of materials and workmanship • Structures that are critical at a network level • New or existing structure which is representative of a larger population of identical or very similar structures • Existing structures with known deficiencies or very low rating • Candidates for replacement or major refurbishment works • List of structures that need a SHM system.

6. STEP 2: Risk Analysis • The SHM system designer, the design engineers or the engineers in charge of the structural assessment and the owner, must jointly identify the risks associated with the specific structure and their probability • The analysis will lead to a list of possible events and degradations that can possibly affect the structure, their impact and probability • i.e. corrosion, creep, foundations subsidence, earthquake strike, impact, inaccuracy of FEM, poor material and execution. • List of risks and degradations that must be addressed by the SHM system.

7. STEP 3: Responses to degradations • For each risk and opportunity, associate one or several responses that can be observed directly or indirectly • i.e. corrosion→chemical change, section loss • subsidence→settlement, change of pore pressure • Roughly quantify the expected responses • i.e. order of magnitude • Define locations • List of expected responses to be detected, estimated amplitudes and location.

8. STEP 4: Design SHM System • Select appropriate sensors and technologies • Consider the required lifetime of the SHM system • Consider the available budget • Consider reliability and redundancy • Consider installation and construction schedule • Monitoring design proposal.

9. STEP 5: Installation and Calibration • Installation and testing of all components • Verify correct installation in accordance to the specifications • Site Acceptance Test (SAT) • As-built plan of the SHM system, system manual and calibration report.

10. 3DeMoN 3rd Parties SOFO MuSt Sensoptic DiTeSt/DiTemp SDB Database Other SW SOFO SDB SDB View SDB SPADS SDB Pro SDB Stat STEP 6: Data Acquisition/ Mng • Database system • Documentation of interventions and structure lifetime • Measurements database and a log of events.

11. STEP 7: Data Assessment • By analyzing the responses of the structure, the engineer will be able to identify if any of the foreseen risks and degradations have materialized and if any of the opportunities are confirmed • The owner will establish procedures to respond to the detection of any degradation • i.e. for immediate action or usual maintenance schedule • The analysis of the data might prompt for further investigation, including inspection, testing or installation of additional sensors • Alerts, warnings and periodic reports.

12. SHM of Buildings • High-rise buildings (150–300 m) • Steel • Concrete • Large/tall (70–150 m) buildings in seismic areas • Critical buildings (hospitals, schools, power plants,...) • Sports arenas • Large commercial buildings • Historical buildings and monuments.

13. Case Study – Tall Buildings in Singapore • HDB (Housing and Development Board) – Singapore’s Public Housing Authority • Quality assurance • Increase safety during the service • Increase knowledge of structural behavior • Verify construction process • Optimize maintenance costs • Verify condition after earthquake, strong wind, impact or terrorist attack • Up today >300 buildings equipped with >3000 sensors

14. Sensor Cable (Passive Zone) Sensor Connection Box 2nd floor 0.75m Column 2m 0.75m 1st (ground) floor Foundations Monitoring strategy • Local structural monitoring  monitoring of critical members, i.e. 10 columns at ground level • Global structural monitoring  correlation between measurements performed on different columns Before After Shortening Shortening Elongation Sensor Settlement

15. Sensors positions C9 UNIT F C3 C2 UNIT E C1 UNIT A C10 MULTI - STOREY VOID UNIT D C4 C7 UNIT B UNIT C C5 C6 C8 1ST STOREY FLOOR PLAN Position of the columns in ground floor equipped with sensors. Monitoring of columns with different cross-section and on a global level, the monitoring of the structural behaviour of four units and estimation of the global building behaviour.

16. Embedding in plant Embedding on-site Passive zone Junction box SOFO sensor After pouring Measurement Photos of Installation

17. End of constr. of 19 storeys End of constr. of 19 storeys Measured vs. design strain Designed total strain in column C3 is practically equal to measured total strain indicating that the performance of the column follows numerical calculus. Contrary measured total strain of column C9 is significantely lower than the disigned total strain indicating over-dimensioning of the column.

18. Punggol results – seven+-years record 48-h ‘04 Tremor 48-h ‘05 48-h ‘06 48-h ‘07 End of construction of 19 storeys Time-dependent evolution of the avarage strain in columns monitored during more than seven years with particular important periods. 48-hours sessions allow better assessment of building performance (rehological effects) in long-term.

19. Roof deflection monitoring,Halifax Metro Centre, Canada Construction: late 1970s multi-entertainment, sports facility and exhibition centre seating capacity: 10,595 (ice hockey)

20. Monitoring goals • Evaluate roof load and induced stresses due to • Snow load • Suspended loads for special events • Evaluate need to strengthening due to changed snow-load codes

21. Sensor layout: Strain + Laser Warning!

22. Installation

23. Results: snowfall event Dec 16-17, 2007 Recorded loads well below strain limits: no retrofitting is needed Strain levels in bottom chord of Truss C during snow and rain events

24. Results: Snow + Ozzy !!! Data plot from 2 strain sensors on Truss A measured between Jan 19 and Feb 6, 2008. The threshold level is set at 75% of the max. allowable strain level.

25. Conclusions • ISHMS Integrated Structural Health Monitoring Systems are based on a design methodology leading to an optimal system configuration for a specific structure and budget • They supply actionable and useful information to the owner • Use and integrate the most suitable sensing technology for each sensing need.

26. Thank you! Any question? MEMSCON Workshop Structural Monitoring and Status-Dependent Maintenance and Repair of Constructed Facilities 7 October 2010, Bucharest, Romania