Research

 

Smart Materials Improve Earthquake-Resistant Bridge Design

Misha Rafiee, California Institute of Technology   17 August 2012    Author Misha Raffiee is a sophomore undergraduate at the California Institute of Technology. She began work on the NSF/NEES 4-Span Bridge Project following her graduation from high school at age 15, and was one of the project presenters at the NSF Hazards Research Showcase at the United States Senate.  (CREDIT: Dr. M. Saiid Saiidi, NEES@University of Nevada, Reno )

(This Behind the Scenes article was provided to LiveScience in partnership with the National Science Foundation.)

Bridges are a main component of the transportation infrastructure as we know it today. There are no less than 575,000 highway bridges nationwide, and over $5 billion are allocated yearly from the federal budget for bridge repairs.Over the past couple decades, increasing seismic activity around the world has been identified as an impending threat to the strength and well-being of our bridges. Earthquakes have caused numerous bridge collapses including in the U.S., Japan, Taiwan, China, Chile and Turkey. Therefore, we need to find ways to minimize seismic effects on bridges, both by improving existing bridges and refining specifications and construction materials for future bridges.A large majority of bridges are made of steel and concrete. While this combination is convenient and economical, steel-concrete bridges don’t hold up as well in strong earthquakes (7.0 magnitude or higher). Conventional reinforced columns rely on the steel and concrete to dissipate energy during strong earthquakes, potentially creating permanent deformation and damage in the column and making the column unusable.Under earthquake loading, engineers allow for damage in column hinges to dissipate energy and prevent total bridge collapse. While that practice is widely accepted, the effects of hinge damage can interfere with disaster recovery operations and have a major economic impact on the community.With funding from the National Science Foundation and using NSF’s George E. Brown, Jr. Network for Earthquake Engineering Simulation, civil engineer M. Saiid Saiidi of the University of Nevada, Reno, and his colleagues have discovered a solution. They’ve identified several smart materials as alternatives to steel and concrete in bridges.Shape memory alloys are unique in their ability to endure heavy strain and still return to their original state, either through heating or superelasticity. SMAs demonstrate an ability to re-center bridge columns, which minimizes the permanent tilt columns can experience after an earthquake.

 

 

earthquake safety, earthquake-resistant bridge designs
Traditional bridge columns are constructed from concrete and reinforced steel, which are seldom effective against earthquakes. But new research suggests that replacing concrete and steel with smart materials is a good alternative. From left: cement-polyvinyl fiber mixture; fiberglass column; carbon fiber column; nickel titanium shape memory alloy.
CREDIT: Dr. M. Saiid Saiidi, NEES@University of Nevada, Reno

 

 

Nickel titanium, or nitinol, the shape memory alloy tested in the UNR project, has a unique ability even amongst SMAs. While the majority of SMAs are only temperature-sensitive, meaning that they require a heat source to return to their original shape, Nitinol is also superelastic. This means that it can absorb the stress imposed by an earthquake and return to its original shape, which makes nitinol a particularly advantageous alternative to steel. In fact, the superelasticity of nickel titanium is between 10 to 30 times the elasticity of normal metals like steel.

To assess the performance of nickel-titanium reinforced concrete bridges, the researchers analyzed three types of bridge columns: traditional steel and concrete, nickel titanium and concrete, and nickel titanium and engineered cementitious composites, which include cement, sand, water, fiber and chemicals. First, they modeled and tested the columns in OpenSEES, an earthquake simulation program developed at the University of California, Berkeley. Finally, they assembled and tested the columns on the UNR NEES shake table.

To strengthen the concrete and prevent immediate failure in an earthquake, the researchers used the shake tables to test glass and carbon fiber-reinforced polymer composites. Both composites substantially enhanced the reinforcing properties of concrete and the columns resisted strong earthquake forces with minor damage.

The results of both the modeling and shake table tests were extremely promising. The nickel titanium/ECC bridge columns outperformed the traditional steel and concrete bridge columns on all levels, limiting the amount of damage that the bridge would sustain under strong earthquakes.

While the initial cost of a typical bridge made of nickel titanium and ECC would be about 3 percent higher than the cost of a conventional bridge, the bridge’s lifetime cost would decrease. Not only would the bridge require less repair, it would also be serviceable in the event of moderate and strong earthquakes. As a result, following a strong earthquake, the bridge would remain open to emergency vehicles and other traffic.

 

 

 

Seismic Response of Precast Bridge Columns with Energy Dissipating Joints

ProQuest Dissertations and Theses, 2011
Dissertation
Author: Sarira Motaref

Abstract:

     The purpose of this study was to develop precast column details that are able to dissipate energy under seismic loads.  Several innovative precast concrete columns were designed, and studied experimentally on a shake table and analyzed. Two types of precast bridge columns were studied, including segmental columns and monolithic columns.
     The first part of the project included studying four segmental concrete cantilever column models with plastic hinges incorporating different advanced materials to reduce damage under earthquake loads. All the models were of one-third scale with longitudinal steel dowels connecting the base segment to the footing. Unbonded post-tensioning was used to connect the segments and to minimize residual displacements. Energy dissipation took place mostly through the yielding of the longitudinal bars in the base segment.
     One of the four column models constituted the benchmark case (SC-2). In this column conventional reinforced concrete detail was used in the base segment. The performance of other specimens having innovative materials in plastic hinges was compared with SC-2 to evaluate their merit relative to SC-2. The second specimen was a segmental concrete column incorporating an elastomeric bearing pad in the plastic hinge (SBR-1). The other two columns incorporated ECC (engineered cementitious composite) and unidirectional CFRP (carbon fiber reinforced polymer) fabrics in the lower two segments (SE-2 and SF-2), respectively. The purpose of using the elastomeric pad was to minimize damage while dissipating energy through yielding of the longitudinal bars and deformation of the rubber.
     Ductile behavior of the ECC resulted in less damage at the interface of the base and second segments in SE-2, and the column was able to sustain its lateral capacity under large drifts. The FRP wrapping provided confinement for the concrete and increased the displacement ductility capacity. The concrete damage in SF-2 was minimal and yielding of the longitudinal bars in the plastic hinge was more extensive. Compared to standard precast concrete segmental columns (those with no monolithic connection between the base segment and the footing), all specimens showed superior performance with minimal residual displacement and larger energy dissipation.
     The effectiveness of repair with CFRP wraps was also studied by repairing and retesting SC-2. The results showed that the strength and ductility capacity of the repaired model were improved compared to the original column, although the initial stiffness was lower. The relatively simple and effective repair procedure demonstrated that it is possible to quickly repair and restore the bridge.
     The second part of the project was testing and analysis of a 0.3-scale two-column bent incorporating two precast columns, precast footing, and a precast cap beam. Two openings were formed in the footing during the construction to allow for placement of precast columns. The embedment length was designed in such a way as to transfer the full plastic moment of the column to the footing. One column was built with conventional reinforced concrete, but incorporated ECC in the plastic hinge zone instead of concrete (RC-ECC column). The other column consisted of a GFRP (glass fiber reinforced polymer) tube with +/- 55-degree fibers filled with concrete (FRP column). The column-pier cap connection was a telescopic steel pipe-pin to facilitate construction.
     The bent was tested to failure, which was due to fracture of longitudinal bars in the RC-ECC column, and rupture of GFRP fibers in the FRP column. Test results showed that the embedment length was sufficient to develop the plastic moment completely in both columns. It was further found that the seismic performance of both columns was satisfactory and that the pipe-pin connections performed well in that they remained damage free, as intended.
     Comprehensive analytical models were developed using program OpenSees for all the test models and acceptable correlation was achieved between the measured and calculated data. The test results showed that the proposed models are suitable for accelerated bridge construction in high seismic zones (where large drifts are expected during earthquakes) because of their superior performance, such as fast construction, large energy dissipation, minimal damage in the plastic hinge zone and minimal residual displacement. (Abstract shortened by UMI.)

PUBLICATIONS AND PRESENTATIONS

 

(Note: All ECC materials for articles cited below were formulated and cast by FiberMatrix, Inc. and Surface Systems)

Saiidi, M., and H. Wang, ―An Exploratory Study of Seismic Response of Concrete Columns with Shape Memory Alloys Reinforcement,‖ American Concrete Institute, ACI Structural Journal, Vol. 103, No. 3, May-June 2006, pp. 436-443.

Saiidi, M., M. Zadeh, and M. O‘Brien, ―Control of Earthquake Damage in Concrete Bridge Columns Using Innovative Materials,‖ Proceedings, 2006 Concrete Bridge Conference, National Meeting, Reno, Nevada, Paper No. 81, May 2006.

Saiidi, M., M. O‘Brien, and M. Zadeh, ―Cyclic Response of Concrete Bridge Columns Using Superelastic Nitinol and Bendable Concrete,‖ American Concrete Institute, ACI Structural Journal, Vol. 106, No. 1, January-February 2009, pp. 69-77.

Saiidi, M., E. Reinhardt, F. Gordaninejad, ―A New Earthquake-Resistant Concrete Pier w/ FRP Fabrics and Shifted Plastic Hinges,‖ (Invited Paper), Journal of Mechanics of Materials and Structures, Vol. 4, No. 5, 2009, pp. 927-940.

Saiidi, M., C. Cruz, and D. Hillis, ―Multi Shake Table Seismic Studies of a 33-Meter Concrete Bridge with High-Performance Materials,‖ Invited, International Journal of Civil Engineering, Vol. 8, No. 1, March 2010, pp. 13-19.

Cruz, C., and M. Saiidi, ―Shake Table Studies of a 4-Span Bridge Model with Advanced Materials,‖ Journal of Structural Engineering, ASCE, Vol. 138, No. 2, February 2012, pp. 183-192.

Vosooghi, A., and M. Saiidi, ―Shake Table Studies of Repaired RC Bridge Columns Using CFRP Fabrics,‖ Accepted 5/2012, American Concrete Institute, ACI Structural Journal.

Cruz, C., and M. Saiidi, ―Performance of Advanced Materials during Shake Table Tests of a 4-Span Bridge Model,‖ Accepted, Journal of Structural Engineering, ASCE.

Saiidi, M., A. Vosooghi, C. Cruz, S. Motaref, C. Ayoub, F. Kavianipour, and M. O‘Brien, ―Earthquake-Resistant Bridges of the Future with Advanced Materials,‖ Accepted, Performance-Based Seismic Engineering- Vision for an Earthquake Resilient Society, Bled 4, Lake Bled, Slovenia, June 2011.

Saiidi, M., M. Zadeh, and M. O‘Brien, ―Analysis of Reinforced Concrete Bridge Columns with Shape Memory Alloy and Engineered Cementitious Composites under Cyclic Loads,‖ Proceedings, 3rd International Conference on Bridge Maintenance, Safety, and Management, Porto, Portugal, July 2006, 8p.

Saiidi, M., ―Superelastic Shape Memory Alloy Reinforced Concrete,‖ CANSMART 2007, Proceedings, 10th Canadian Conference on Smart Materials, Montreal, Canada, October 2007, pp. 57-66.

Gutierrez, J., S. Arnold, A. Vosooghi, and M. Saiidi, ―Emergency Repair of Damaged Bridge Columns using Fiber Reinforced Polymer (FRP) Materials,‖ Proceedings, Structural Engineers Association of California Convention, Kohala Coast, Hawaii, September 2008, pp. 163-169.

Cruz, C., M. Saiidi, and D. Hillis, ―Pretest Seismic Analysis of a 4-Span Bridge Model with Advanced Materials,‖ Proceedings, First International Conference on Computational Technologies in Concrete Structures (CTCS ‘09), Session W4A, Jeju, S. Korea, May 200

Saiidi, M., C. Cruz, and D. Hillis, ―High-Performance Materials in Earthquake-Resistant Concrete Bridges,‖ Proceedings, Fifth International Structural engineering and Construction Conference (ISEC-5), Invited keynote paper, Las Vegas, Nevada, September 2009, pp. 3-6.

Saiidi, M., C. Cruz, and D. Hillis, ―Multi-Shake Table Seismic Studies of a 33-Meter Concrete Bridge with High-Performance Materials,‖ Proceedings, Second International Conference on Recent Advances in Railroad Engineering, Invited keynote paper, Tehran, Iran, October 2009.

Motaref, S., M. Saiidi, and D. Sanders, ―Segmental Bridge Columns w/ Damage-Free Plastic Hinges,‖ Proceedings, Special International Workshop on Seismic Connection Details for Segmental Bridge Construction, Seattle, Washington, July 2009,‖ MCEER Technical Report 09-0012, University of Buffalo, Buffalo, New York, December 2009, pp. 75-82.

Cruz, C., M. Saiidi, and D. Hillis, ―Analytical Study of a 4-Span Bridge with Advanced Materials,‖ Proceedings, 4th International Workshop on Reliable Engineering Computing, Singapore, March 2010, pp. 197-210.

Cruz-Noguez, C, and M. Saiidi, ―Simulated Response of Bridges with Advanced Materials under Near-Fault Earthquakes,‖ Proceedings, 3rd World Science and Engineering Academy and Society International Conference on Engineering Mechanics, Structures, and Engineering Geology, Korfu, Greece, July 2010, pp. 429-434.

Cruz-Noguez, C, and M. Saiidi, ―Performance of Advanced Materials and Details during Shake Table Tests of a 4-Span Bridge Model,‖ Proceedings, 1st Middle Eastern Conference on Smart Materials Monitoring, Assessment and Rehabilitation of Civil Structures, Dubai, UAE, Paper No. 102, February 2011.

Saiidi, M., A. Vosooghi, A. Zaghi, S. Motaref, and C. Cruz, ―Innovative Earthquake-Resistant Bridges- Repair, Connections, and Materials,‖ Keynote Paper, Proceedings, International Conference IBSBI 2011, Innovations on Bridges and Soil-Bridge Interaction, Athens, Greece, October 2011, pp. 107-123.

Saiidi, M., A. Vosooghi, Z. Haber, S. Motaref, and C. Cruz, and D. Sanders, ―Next Generation of Earthquake-Resistant Bridges,‖ Keynote Paper, International Conference EQADS 2011, Earthquake Analysis and Design of Structures, Coimbatore, India, December 2011, pp. 125-134.

Saiidi, M., A. Vosooghi, C. Cruz, S. Motaref, C. Ayoub, F. Kavianipour, Z. Haber, M. O‘Brien, and D. Sanders, ―Earthquake-Resistant Bridges of the Future with Advanced Materials,‖ Keynote Paper, Proceedings, Ninth International Congress on Civil Engineering, 9ICCE, Isfahan, Iran, May 2012, 12pp.

Kavianipour, F., and M. Saiidi, ―Shake Table Testing of A Quarter-Scale 4-Span Bridge With Composite Piers,‖ Proceedings, International Conference on Bridge Maintenance, Safety, and Management, Stresa, Italy, July 2012, pp. 1966-1973.

O‘Brien, M., M. Saiidi, and M. Sadrossadat-Zadeh, ―A Study of Concrete Bridge Columns Using Innovative Materials Subjected to Cyclic Loading,‖ Center for Civil Engineering Earthquake Research, Department of Civil Engineering, University of Nevada, Reno, Nevada, Report No. CCEER-07-1, January 2007.

Cruz-Noguez, C., and M. Saiidi, ―Experimental and Analytical Seismic Studies of a Four-Span Bridge System with Innovative Materials,‖ Center for Civil Engineering Earthquake Research, Department of Civil and Environmental Engineering, University of Nevada, Reno, Nevada, Report No. CCEER-10-4, September 2010.

Vosooghi, A., and Saiidi, M., ―Post-Earthquake Evaluation and Emergency Repair of Damaged RC Bridge Columns Using CFRP Materials,‖ Center for Civil Engineering Earthquake Research, Department of Civil and Environmental Engineering, University of Nevada, Reno, Nevada, Report No. CCEER-10-5, September 2010, 636 pp.

Motaref, S., M. Saiidi, and D. Sanders, ―Seismic Response of Precast Bridge Columns with Energy Dissipating Joints,‖ Center for Civil Engineering Earthquake Research, Department of Civil and Environmental Engineering, University of Nevada, Reno, Nevada, Report No. CCEER-11-1, May 2011, 760 pp.

Saiidi, M., ―Bridges of the Future- Widespread Implementation of Innovation, Proceedings of NSF International Workshop,‖ Center for Civil Engineering Earthquake Research, Department of Civil and Environmental Engineering, University of Nevada, Reno, Nevada, Report No. CCEER-12-1, January 2012, 304 pp.

*Saiidi, M., ―Resilient Concrete Bridges with Advanced Materials,‖ Beyer Distinguished Lecture Series, Department of Civil and Environmental Engineering, University of Houston, Houston, Texas, November 2009.

*Motaref, S., M. Saiidi, and D. Sanders, ―Shake Table Response of Precast Bridge Columns with Advanced Materials,‖ Seismic ABC Collaboration, Session Sponsored by TRB Committee AFF50, Transportation Research Board 89th Annual Meeting, Washington, DC, January 2010.

Saiidi, M., ―Advanced Materials, Rapid Repair, and Precast Bridge Piers- Examples of Recent Research on Earthquake Response of Bridges,‖ Extended Seminar (90-minute long) Japan Society of Civil Engineers, Tokyo, Japan, February 2010.

Saiidi, M., ―Sustainable Earthquake-Resistant Bridges Incorporating Innovations and ABC,‖ Session No. 19, Seismic/Substructures, 2010 FHWA Bridge Engineering Conference: Highway for Life and Accelerated Bridge Construction, Orlando, Florida, April 2010.

*Saiidi, M., ―Earthquake-Resistant Concrete Bridges with Advanced Materials and Rapid Construction,‖ Seminar, Swiss Federal Laboratories for Materials Science and Technology, EMPA, Zurich, Switzerland, September 2010.

*Saiidi, M., F. Kavianipour, C. Cruz, D. Hillis, and R. Nelson, ―Shake Table Response of Four-Span Bridges with Advanced Materials,‖ Quake Summit 2010, NEES and PEER Annual Meeting, San Francisco, California, October 2010.

*Saiidi, M., S. Motaref, C. Cruz, M. O‘Brien, and H. Wang, ―Seismic Response of Bridge Columns with Engineered Cementitious Composites,‖ ACI Fall 2010 Convention, Session Titled: ―High-Performance Concrete for Seismic Design of Bridges‖ Pittsburgh, Pennsylvania, October 2010.

Saiidi, M., ―Seismic Performance of Bridges with Advanced Materials,‖ NSF Workshop on Bridges of the Future- Widespread Implementation of Innovation An International Workshop to Develop Action Plans, Las Vegas, Nevada, June 2011.

*Saiidi, M., ―Earthquake-Resistant Bridges of the Future with Advanced Materials,‖ Bled 4 Workshop: Performance-Based Seismic Engineering- Vision for an Earthquake Resilient Society, Lake Bled, Slovenia, June 2011.

*Saiidi, M., R. Nelson, C. Cruz, F. Kavianipour, and M. Raffiee, ―Seismic Performance of Bridge Systems with Conventional and Innovative Design,‖ Poster presented at the NSF Hazards Research Showcase, United States Senate, Washington, DC, September 2011.

*Saiidi, M., R. Nelson, C. Cruz, F. Kavianipour, and M. Raffiee, ―Seismic Performance of Bridge Systems with Conventional and Innovative Design,‖ Poster presented at the NSF Hazards Research Showcase, United States Senate, Washington, DC, September 2011.

*Saiidi, M., A. Vosooghi, C. Cruz, S. Motaref, C. Ayoub, F. Kavianipour, Z. Haber, M. O‘Brien, and D. Sanders, ―Earthquake-Resistant Bridges of the Future with Advanced Materials,‖ Keynote Speech, Ninth International Congress on Civil Engineering, 9ICCE, Isfahan, Iran, May 2012.

*Saiidi, M., ―Shape Memory Alloy and High-Performance Grout in Earthquake-ResistantBridges-from Research to Implementation,” The Fifth Kwang-Hua Forum on Innovations and Implementations in Earthquake Engineering Research,‖ Shanghai, China, December 2012.