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Fatigue Problems in Civil and Aerospace Structures

Fatigue Problems in Civil and Aerospace Structures. Dr. Ribelito F. Torregosa , CIT-U BSCE ‘91. Research Scientist - Aerospace Division Defence Science and Technology Group. Cebu Institute of Technology – University Alumni Association (CIT-UAA) Lecture Series Program. UNCLASSIFIED.

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Fatigue Problems in Civil and Aerospace Structures

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  1. Fatigue Problems in Civil and Aerospace Structures Dr. Ribelito F. Torregosa, CIT-U BSCE ‘91 Research Scientist - Aerospace Division Defence Science and Technology Group Cebu Institute of Technology – University Alumni Association (CIT-UAA) Lecture Series Program

  2. UNCLASSIFIED About me Japan (Gifu University) • Ph. D. (Earthquake Eng’g.) - 2002 Thailand (Asian Instiute of Technology) • Master of Eng’g (Structural) - 1998 Philippines ( CIT-91) • BS Civil Eng’g. Australia • Defence Science and Technology Group (Research Scientist)

  3. UNCLASSIFIED What is Fatigue Failure? Fatigue failure - is a phenomenon where structures fail when subjected to a cyclic load Which loading will cause fatigue failure? P P time P time

  4. UNCLASSIFIED Dynamic loads - cause of fatigue failures Civil engineering structures Aircraft structures Air pressure - variable Ground shaking due to earthquakes

  5. UNCLASSIFIED Deficiency in Earthquake Static load design of structures Load case 2 Load case 1 Does not consider accumulated damage

  6. UNCLASSIFIED Crack propagation due to fatigue loads Tension Compression Crack size increase with each load cycle

  7. UNCLASSIFIED Fatigue Failures in Civil Engineering EARTHQUAKE

  8. UNCLASSIFIED Earthquake occurrences worldwide Number of occurrences every year = 10,000+ Philippines Australia Source: Wikipedia

  9. Ring of Fire - high volcanic and seismic activity (earthquakes). Most of the active volcanoes on Earth are located on this circumference. Alaska (USA) California (USA) Japan Philippines Mexico Peru Indonesia Chile New Zealand

  10. UNCLASSIFIED Locating the epicenter of an earthquake Seismograph station Earthquake epicentre Earth’s surface P-wave S-wave Earthquake hypocentre P-wave (pressure) – travels faster, low amplitude S-wave (shear) – travels slower, high amplitude

  11. UNCLASSIFIED Locating the epicenter of an earthquake Seismograph station Earthquake epicentre Earth’s surface S-wave Earthquake hypocentre P-wave P-wave (pressure) – travels faster, low amplitude S-wave (shear) – travels slower, high amplitude

  12. UNCLASSIFIED Locating the epicenter of an earthquake S wave arrival time P wave arrival time Seismogram • Time of arrival of P and S waves known • Distance of earthquake starting point (i.e., epicenter) from seismograph station known

  13. UNCLASSIFIED Distance travelled given Time of arrival and Speed Given: one car from unknown starting point Distance (D) Speed (V1) =100 kph Arrival time (t1)=10:00am ?? ?? 100 • Information not enough to solve Distance (D)

  14. UNCLASSIFIED Distance travelled given Time of arrival and Speed Given: two cars from unknown starting point Distance (D) Arrival times =10:00am Speed (V1) =100 kph Speed (V2) =50 kph =12:00am Distance travelled by car 1 = Distrancetravelled by car 2 +2 hours) 2 hours

  15. UNCLASSIFIED Two main factors causing fatigue failure to structures Ground acceleration Ground Motion duration Low acceleration Long duration High acceleration Short duration Earthquake source near far

  16. UNCLASSIFIED Earthquake ground motion duration P-wave S-wave duration duration Low acceleration Long duration High acceleration Short duration Earthquake source near far

  17. UNCLASSIFIED Locating the epicenter of an earthquake Legend : Earthquake epicenter somewhere along the circle Seismograph Station D1

  18. UNCLASSIFIED Locating the epicenter of an earthquake Legend : Seismograph Station Epicenter here D2 D3 D1

  19. Minimizing fatigue failures in civil engineering structures Seismic Hazard Mapping

  20. Minimizing fatigue failures in civil engineering structures Tuned mass damper Base isolation

  21. UNCLASSIFIED Fatigue Problems in Aircraft Structures

  22. UNCLASSIFIED Cost of ownership of military aircraft Cost to purchase: $330 million Cost to fly per hour: $206,337 Manufacturer: Boeing Model: VC – 25 e.g., “ Air Force One”

  23. UNCLASSIFIED Cost of ownership of military aircraft Cost to purchase: $210 million Cost to fly per hour: $173,253 Manufacturer: Lockheed Martin Model: AC – 130H Mission : “Special Operation”

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