Engineering Case Study:Cypress Street Viaducts

Group 12:Chris Springer, Andrew Duncan, and Adam Kassar

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

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

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

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

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)

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

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

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

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

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

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

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

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

References

http://www.engineering.com/Library/ArticlesPage/tabid/85/ArticleID/73/categoryId/7/Cypress-Street-Viaducts.aspx

Doyle, Kevin, (Ed.), Oct. 30, 1989, "The Day The Earthed Roared", Maclean's Magazine, pp. 54-62. Halliday, David; Resnick, Robert; Walker, Jearl, 1993, Fundamentals of Physics, Extended, 4th ed., John Wiley & Sons Inc., 1306 pp., ISBN 0-471-57578-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. 288-293, ISSN 0889-325X.

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: http://www.eerc.berkeley.edu/loma_prieta/moehle.html.

Peterson, Alan, (Ed.), Mar. 1990, "Excuses on Shaky Ground", International Construction, Vol. 29, No. 3, pp. 40-41, ISSN 0020-6415.

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 http://www.eerc.berkeley.edu/loma_prieta/stewart.html.

Yashinsky, Mark, 1998, "Cypress Street Viaduct", US Geological Survey Professional Paper, No. 1552-8, pp. 19-26, Library of Congress catalog-card No. 92-32287.