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Forensic Engineering June 1, 2009.

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Presentation on theme: "Forensic Engineering June 1, 2009."— Presentation transcript:

1 Forensic Engineering June 1, 2009

2 SPEAKERS Tim Banta Raleigh Office Lead Engineer BS Civil Engineering
MS Structural Engineering Roanoke Co-op (May 1999) Raleigh Full Time (July 2004) Professional Engineer (NC, TX)

3 What is Forensic Engineering?
Analysis of Failures Types of Forensics Automotive Accidents Aviation Accidents Crime Scene Investigation Mechanical Failures Structural Failures “The determination of the cause of a performance deficiency in a building, pipeline, structure or other engineering facility.”

4 Structural Forensic Engineering
World Trade Center

5 Structural Forensic Engineering
Pentagon

6 Structural Forensic Engineering
Alfred P. Murrah Federal Building

7 Structural Forensic Engineering
I-35W Mississippi River Bridge

8 Structural Forensic Engineering
More Than Just Collapses Types of Structural Failures Cladding/Envelope Failures Excessive Vibration Excessive Deflection Installation/Workmanship Issues Mold and Moisture Issues Excessive or Differential Settlements Partial and Catastrophic Collapse

9 Wind Induced Vibrations
Tacoma Narrows Bridge Collapse Washington, near Puget Sound Opened To Traffic in July 1940 2,800 Foot Main Span Main Span 190 Foot Elevation Long and Slender Bridge Pushed Limits of Design Knowledge

10 Wind Induced Vibrations
Tacoma Narrows Bridge July 1940

11 Wind Induced Vibrations
November 7, 1940 35 mph Winds Winds Perpendicular to Bridge Deflections up to 1.5 Feet Winds Increased to 42 mph Mid-span Cable Failure Deflections up to 28 Feet

12 Wind Induced Vibrations
November 7, 1940

13 Wind Induced Vibrations
November 7, 1940

14 Wind Induced Vibrations
November 7, 1940

15 Wind Induced Vibrations
Cause Still Debated Vortex Shedding Whirlpool Effect Unlikely Cause (Frequency Too High) Aerodynamic Instability Aerodynamic Instability – Like a guitar string. The beams (string) are rotated one way, and bounce back past the starting position. Then in the down position the force pushed on the beams even more.

16 Wind Induced Vibrations
Future Study of Wind Related Effects Wind Tunnel Testing Small Forces Can Have a Profound Impact on a Structure Pushing the Limits Can Have Disastrous Effects

17 Wind Induced Vibrations
Cable Stayed Bridge Vibrations

18 Wind Induced Vibrations
Cable-Stayed Bridges Becoming More Common Unforeseen Cable Vibration Frequently Occurring Rain-Wind Induced Vibration Light to Moderate Rain and Wind Cause Large Vibrations Rain Rivulets Form Diametrically Opposed to Each Other Smooth Polyvinyl Tape Protecting Cables Typically Present Aerodynamic Instability Can Occur Cable Deflections of Up to 2 Meters Can Occur

19 Wind Induced Vibrations
Cause of Vibration and Deflections

20 Wind Induced Vibrations
Need to Reduce Scruton Number Nondimensional Number Important in Aerodynamic Oscillations New Cable-Stayed Bridges Reduction of Cable Diameters Greatly Reduces Scruton Number Existing Cable-Stayed Bridges Install Dampers Helical Fillets Along Length of Cable Increasing Roughness of the Cable

21 Wind Induced Vibrations
Cable Dampers

22 Wind Induced Vibrations
Helical Fillets

23 Structural Forensic Engineering and MBP
How Does Forensics Tie Into MBP’s Current Services? Typically Retained By Attorneys Expert Witness Already Performing Forensic Delay Analysis Forensic Engineering Service Can Lead Into CM Services Estimating Repairs/Damages Scheduling Inspection Services Constructibility Reviews Delay Claims

24 Certifications and Qualifications
Educational Background BS in Engineering Graduate Studies With an MS and/or PHD In Structural Engineering Licensing PE and/or SE SE I – 8 Hour National Exam SE II – 8 Hour National Exam SE III – 8 Hour State Specific Exam Seismic, Wind, Snow, Bridge, Steel, Concrete, Timber Design, Pre-Stressed and Post-Tensioned Design Pass Rates Typically Below 40% or Lower

25 Certifications and Qualifications
Professional Experience 10 Plus Years Typical Extensive Knowledge of Structural Design/Analysis Previous Testifying Experience as Expert Witness Certified Structural Engineer Relatively New Process Pass 16 Hours of Exams 8 Hour SE II Exam Advanced Knowledge in Structural Engineering Educational Background Professional Experience Specifically in Structural Engineering

26 Structural Forensics Projects at MBP
Residential Home Construction MBP Retained as Expert Witness Testify on Inspection Standard of Care for Structural Engineer Identifying Installation Nonconformance’s with Respect to the Design Documents

27 Structural Forensics Projects at MBP
Front of Residence

28 Structural Forensics Projects at MBP
Rear of Residence

29 Structural Forensics Projects at MBP
Roof Members

30 Structural Forensics Projects at MBP
Column Bearing on OSB Flooring

31 Structural Forensics Projects at MBP
Hip Beam In Attic

32 Structural Forensics Projects at MBP
Built-up Wood Girder

33 Structural Forensics Projects at MBP
Steel Beam Under Terrace

34 Structural Forensics Projects at MBP
Door Frame on First Floor

35 Structural Forensics Projects at MBP
Courthouse Renovation MBP Retained as Expert Witness Testify on Design Standard of Care for Structural Engineer High Seismic Area Reviewed Design Documents for Conformance with Design Codes Structural Models Structural Design Calculations Historical Code Research

36 Structural Forensics Projects at MBP
Courthouse Renovation

37 Structural Forensics Projects at MBP
Courthouse Renovation

38 Structural Forensics Projects at MBP
Courthouse Renovation

39 Structural Forensics Exploratory Team
New Service Report

40 Structural Forensics Exploratory Team
New Service Report Background Information on Forensic Engineering Educational Requirements Certifications Professional Liability Implications Marketability Infrastructure Implications at MBP Computers Software Testing Equipment Inspection Equipment

41 Structural Forensics Exploratory Team
New Service Report (cont.) Potential Development Methods at MBP Slow Development/In House Training Fast Development/Outside Recruiting Similar to Commissioning Development Training Courses Seminars Conferences Recruiting Profitability

42 Structural Forensics Exploratory Team
Joining Exploratory Team Contact Tim Banta in Raleigh Always Looking for New Members Don’t Need a Technical or Structural Background to Join the Team

43 Questions

44 References S.M. Palmquist (2006). “Vibrations of Cable-Stayed Bridges,” Forensic Engineering Proceedings of the Fourth Congress, Cleveland, OH, October.


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