1. Engineering Case Study: Cypress Street Viaducts
Group 12:
Chris Springer, Andrew Duncan, and Adam Kassar

2. Outline Circumstances of the disaster Ethical Principles Involved
Suggestions for aversion of the disaster
Hypothetical Situations
Potential Actions of our group if associated with Cypress Street Viaducts project
Ethical Principles Involved with TTE Communication Project
Steps taken to ensure no disaster policy throughout completion of the project

3. Cypress Street Viaduct Background
1949: Commencement of design of new highway for Oakland, California
1957: Construction of the Nimitz Freeway completed (I-880)
Cypress Street Viaduct
Portion of freeway that linked I-880 to I-80
2 km two tier highway, 5 lanes per deck, traffic flowed at ground level
Bridge constructed on soft mud throughout portions of the 2 km span
Soft bay mud increased the vibration amplitude 5 times the vibration amplitude of sections with rock base
Cast in place concrete with multi-celled reinforced box girder used for bridge construction

4. More Cypress Street Viaduct Background
At time of Construction
California State Seismic Criteria: Design for a lateral force of .06 times the dead (permanent) load
All construction specifications and guidelines were followed
1971: Earthquake in San Fernando Valley
Initiation of two-phase highway improvement program
1977 Phase1: involved strengthening connections between elevated roadways and their support columns
Phase 2: to strengthen the support columns ; never carried out

5. Cypress Street Viaducts Circumstances
Description of the Disaster
When: October 17, 1989
Loma Prieta earthquake hit the San Francisco Bay area
Impact of the Disaster
$12 billion in damages
64 casualties
More than half of the 64 casualties occurred on the Cypress Street Viaduct during the quake
Main source of claiming victims = Cypress Street Viaduct

6. Source of the Disaster: Loma Prieta Earthquake
Date of Occurrence: October 17, 1989 at 5:04 p.m.
Strength of the Quake
7.1 on the Richter Scale
Cypress Viaduct Collapse
1.4 km section of the structure collapsed from the upper level and trapped many travelers and motorists
Amount of Death Minimized
Approximately 80 vehicles were on the affected section of the structure during quake
Attributed to the San Francisco Giants playing in the World Series, a saving grace
Captured 35 lives total (more than 50 % of the 64 lives taken)
Minimized because people were watching the Giants game (not as many motorists on the highway).

7. Effects of the Loma Prieta Earthquake
Cypress Street Viaduct collapse was the most devastating effect of the earthquake
Demanded the efforts of emergency crews
Efforts thwarted at freeing people/victims from the rubble caused by the quake
Region containing the Cypress Street Viaduct
Declared a disaster area by State of California
Eligible for $300 million in relief money
Impact on Transportation Infrastructure

8. Contributing Factors Leading to Collapse of Cypress Street Viaducts
Geotechnical Aspect of the central San Francisco Bay area
Soft Bay Mud base for construction
Frequency of seismic waves matched natural frequency of the individual horizontal section of structure
Sediment resonant frequencies
Design of the concrete Viaduct and tolerance of vibration and shock via strong ground shaking
Two tier multi-lane highway constructed of reinforced concrete
Upper and lower levels joined together by two column bents
Connections secured by cast concrete and four pin shear key connections

9. Contributing Factors Continued…
Design of the Viaduct
Lack of secure fastening between the two levels throughout some sections of upper level
Contributed to vulnerability to vibrations
Earthquake tremors/vibrations caused the concrete around pins to deteriorate
Presence of concrete reinforcing the support columns now absent leading to lack of strength
Effect: Upper deck collapsed as columns slid sideways under the weight force of the upper deck

10. Picture captures a few different aspects associated with the Cypress Street Viaduct collapse.
The first aspect is the time domain plots of sound waves (vibrations) with relation to the base a structure is constructed upon. As one can see, soft mud has the highest sound wave amplitude in the time domain graph. The second aspect is the locality of the structure itself which is represented by the map. The final aspect is the collapse of the bridge itself in which one can see how the support columns slid and gaveway to the upper level collapsing.

11. Ethical Principles Involved
Moral Obligation/Integrity
City of Oakland neglecting to upgrade the Cypress Street Viaduct despite repeated recommendation
Earthquake engineers provided suggestions on several occasions for upgrading the structure
Retrofitting of the viaduct with new technologies
The strengthening of the support columns was overlooked

12. Aversion of the Disaster
The following list contains suggestions for how the disaster could have been avoided.
Installation of steel reinforcing plates around the existing columns (retrofitting)
Retrofitting of the viaduct with new technologies
Steel Reinforcing plates to the existing columns
Lead/Rubber isolators to reduce vibration and shock

13. Group Assignment: Project Cypress Street Viaduct
Carry out Phase 2 of the two-phase program in order to increase the resistance of the viaduct to earthquakes
Strengthen the support columns (reinforcement with some concrete material)
No detail can be overlooked with engineering design
During initial construction, look into finding different areas to construct the bridge where soft mud is not present
Minimize the amount of sections of the viaduct constructed upon soft mud
Test different sections of the bridge to measure tolerance to different seismic waves of various amplitudes
Implement more stability to the support columns based on these characterizations

14. Ethical Issues Involved with TTE Communication Project
TTE Communication Project is in the very early stages of preliminary design and prototyping
For our intents and purposes of the design, our product will be a lab bench prototype
Our goal for the project is a proof of concept, but as the project progresses MSHA (Mine Safety and Health Administration) Standards will have to be followed and adhered to strictly
Failure to adhere to MSHA guidelines will result in violation of moral integrity ethical issue

15. Steps Taken by Group to Ensure No Disaster
In the preliminary design, damage to equipment and personal injury may occur
Implement overcurrent/overvoltage protection
Electrically isolate components where applicable
When the project is completed, adherence to strict MSHA guidelines (CFR30) is both required and desired

16. References
Doyle, Kevin, (Ed.), Oct. 30, 1989, "The Day The Earthed Roared", Maclean's Magazine, pp Halliday, David; Resnick, Robert; Walker, Jearl, 1993, Fundamentals of Physics, Extended, 4th ed., John Wiley & Sons Inc., 1306 pp., ISBN X.
Monteiro, Paulo; Asselanis, Jon; MacCracken, William, May-June 1991, "Investigation of the Microstructure and Mechanical Properties of the Structural Materials of the I-880 Double-Deck Viaduct", ACI Materials Journal, Vol. 88, No. 3, pp , ISSN X.

17. References
Moehle, J.P., updated Dec. 9, 1997, accessed Oct. 19, 1999, "Preliminary Observations on the Performance of Concrete Freeway Structures", National Information Service for Earthquake Engineering, University of California, Berkeley, Internet address:
Peterson, Alan, (Ed.), Mar. 1990, "Excuses on Shaky Ground", International Construction, Vol. 29, No. 3, pp , ISSN
Stewart, Jonathan, updated Dec. 8, 1997, accessed Oct. 24, 1999, "Key Geotechnical Aspects of the 1989 Loma Prieta Earthquake", National Information Service for Earthquake Engineering, University of California, Berkeley, Internet address
Yashinsky, Mark, 1998, "Cypress Street Viaduct", US Geological Survey Professional Paper, No , pp , Library of Congress catalog-card No