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 1977 Phase1: involved strengthening connections between elevated roadways and their support columns Phase 2: to strengthen the support columns ; never carried out

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) Minimized because people were watching the Giants game (not as many motorists on the highway).

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

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.

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.