Seismic base isolation

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The base isolators under the Utah State Capitol building Base isolators under the Utah State Capitol.jpg
The base isolators under the Utah State Capitol building
Concurrent shake-table testing of two building models. The right one is equipped with a seismic base isolation Base-isolation.gif
Concurrent shake-table testing of two building models. The right one is equipped with a seismic base isolation
LA City Hall, to be retrofitted with base isolation Los Angeles City Hall (color) edit1.jpg
LA City Hall, to be retrofitted with base isolation

Seismic base isolation, also known as base isolation, [3] or base isolation system, [4] is one of the most popular means of protecting a structure against earthquake forces. [5] It is a collection of structural elements which should substantially decouple a superstructure from its substructure that is in turn resting on the shaking ground, thus protecting a building or non-building structure's integrity. [6]

Contents

Base isolation is one of the most powerful tools of earthquake engineering pertaining to the passive structural vibration control technologies. The isolation can be obtained by the use of various techniques like rubber bearings, friction bearings, ball bearings, spring systems and other means. It is meant to enable a building or non-building structure to survive a potentially devastating seismic impact through a proper initial design or subsequent modifications. In some cases, application of base isolation can raise both a structure's seismic performance and its seismic sustainability considerably. Contrary to popular belief, base isolation does not make a building earthquake proof.

Base isolation system consists of isolation units with or without isolation components, where:

  1. Isolation units are the basic elements of a base isolation system which are intended to provide the aforementioned decoupling effect to a building or non-building structure.
  2. Isolation components are the connections between isolation units and their parts having no decoupling effect of their own.

Isolation units could consist of shear or sliding units. [7] [ unreliable source? ] [8] [ unreliable source? ]

This technology can be used for both new structural design [9] and seismic retrofit. In process of seismic retrofit, some of the most prominent U.S. monuments, e.g. Pasadena City Hall, San Francisco City Hall, Salt Lake City and County Building or LA City Hall were mounted on base isolation systems. It required creating rigidity diaphragms and moats around the buildings, as well as making provisions against overturning and P-Delta Effect.

Base isolation is also used on a smaller scale—sometimes down to a single room in a building. Isolated raised-floor systems are used to safeguard essential equipment against earthquakes. The technique has been incorporated to protect statues and other works of art—see, for instance, Rodin's Gates of Hell at the National Museum of Western Art in Tokyo's Ueno Park. [10]

Base isolation demonstration at The Field Museum in Chicago Earthquake Protector at The Field Museum.jpg
Base isolation demonstration at The Field Museum in Chicago

Base isolation units consist of Linear-motion bearings, that allow the building to move, oil dampers that absorb the forces generated by the movement of the building, and laminated rubber bearings that allow the building to return to its original position when the earthquake has ended. [11]

History

Base isolator bearings were pioneered in New Zealand by Dr Bill Robinson during the 1970s. [12] The bearing, which consists of layers of rubber and steel with a lead core, was invented by Dr Robinson in 1974. [13] The earliest uses of base isolation systems date back all the way to 550 B.C. in the construction of the Tomb of Cyrus the Great in Pasargadae, Iran. [14] More than 90% of Iran’s territory, including this historic site, is located in the Alpine-Himalaya belt, which is one of the Earth’s most active seismic zones. Historians discovered that this structure, predominantly composed of limestone, was designed to have two foundations. The first and lower foundation, composed of stones that were bonded together with a lime plaster and sand mortar, known as Saroj mortar, was designed to move in the case of an earthquake. The top foundation layer, which formed a large plate that was in no way attached to the structure’s base, was composed of polished stones. The reason this second foundation was not tied down to the base was that in the case of an earthquake, this plate-like layer would be able to slide freely over the structure’s first foundation. As historians discovered thousands of years later, this system worked exactly as its designers had predicted, and as a result, the Tomb of Cyrus the Great still stands today. The development of the idea of base isolation can be divided into two eras. In ancient times the isolation was performed through the construction of multilayered cut stones (or by laying sand or gravel under the foundation) while in recent history, beside layers of gravel or sand as an isolation interface wooden logs between the ground and the foundation are used. [15]

Research

Through the George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES), researchers are studying the performance of base isolation systems. [16] The project, a collaboration among researchers at University of Nevada, Reno; University of California, Berkeley; University of Wisconsin, Green Bay; and the University at Buffalo is conducting a strategic assessment of the economic, technical, and procedural barriers to the widespread adoption of seismic isolation in the United States. NEES resources have been used for experimental and numerical simulation, data mining, networking and collaboration to understand the complex interrelationship among the factors controlling the overall performance of an isolated structural system. This project involves earthquake shaking table and hybrid tests at the NEES experimental facilities at the University of California, Berkeley, and the University at Buffalo, aimed at understanding ultimate performance limits to examine the propagation of local isolation failures (e.g., bumping against stops, bearing failures, uplift) to the system level response. These tests will include a full-scale, three-dimensional test of an isolated 5-story steel building on the E-Defense shake table in Miki, Hyogo, Japan. [17] Seismic isolation research in the middle and late 1970s was largely predicated on the observation that most strong-motion records recorded up to that time had very low spectral acceleration values (2 sec) in the long-period range. Records obtained from lakebed sites in the 1985 Mexico City earthquake raised concerns of the possibility of resonance, but such examples were considered exceptional and predictable. One of the early examples of the earthquake design strategy is the one given by Dr. J.A. Calantariens in 1909. It was proposed that the building can be built on a layer of fine sand, mica or talc that would allow the building to slide in an earthquake, thereby reducing the forces transmitted to building. A detailed literature review of semi-active control systems Michael D. Symans et al. (1999) provides references to both theoretical and experimental research but concentrates on describing the results of experimental work. Specifically, the review focuses on descriptions of the dynamic behavior and distinguishing features of various systems which have been experimentally tested both at the component level and within small scale structural models.

Adaptive base isolation

An adaptive base isolation system includes a tunable isolator that can adjust its properties based on the input to minimize the transferred vibration. Magnetorheological fluid dampers [18] and isolators with Magnetorheological elastomer [19] have been suggested as adaptive base isolators.

Notable buildings and structures on base isolation systems

See also

Related Research Articles

<span class="mw-page-title-main">Seismic retrofit</span> Modification of existing structures to make them more resistant to seismic activity

Seismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. With better understanding of seismic demand on structures and with recent experiences with large earthquakes near urban centers, the need of seismic retrofitting is well acknowledged. Prior to the introduction of modern seismic codes in the late 1960s for developed countries and late 1970s for many other parts of the world, many structures were designed without adequate detailing and reinforcement for seismic protection. In view of the imminent problem, various research work has been carried out. State-of-the-art technical guidelines for seismic assessment, retrofit and rehabilitation have been published around the world – such as the ASCE-SEI 41 and the New Zealand Society for Earthquake Engineering (NZSEE)'s guidelines. These codes must be regularly updated; the 1994 Northridge earthquake brought to light the brittleness of welded steel frames, for example.

<span class="mw-page-title-main">Seismic analysis</span> Study of the response of buildings and structures to earthquakes

Seismic analysis is a subset of structural analysis and is the calculation of the response of a building structure to earthquakes. It is part of the process of structural design, earthquake engineering or structural assessment and retrofit in regions where earthquakes are prevalent.

Earthquake engineering is an interdisciplinary branch of engineering that designs and analyzes structures, such as buildings and bridges, with earthquakes in mind. Its overall goal is to make such structures more resistant to earthquakes. An earthquake engineer aims to construct structures that will not be damaged in minor shaking and will avoid serious damage or collapse in a major earthquake. A properly engineered structure does not necessarily have to be extremely strong or expensive. It has to be properly designed to withstand the seismic effects while sustaining an acceptable level of damage.

Vibration isolation is the prevention of transmission of vibration from one component of a system to others parts of the same system, as in buildings or mechanical systems. Vibration is undesirable in many domains, primarily engineered systems and habitable spaces, and methods have been developed to prevent the transfer of vibration to such systems. Vibrations propagate via mechanical waves and certain mechanical linkages conduct vibrations more efficiently than others. Passive vibration isolation makes use of materials and mechanical linkages that absorb and damp these mechanical waves. Active vibration isolation involves sensors and actuators that produce disruptive interference that cancels-out incoming vibration.

This is an alphabetical list of articles pertaining specifically to structural engineering. For a broad overview of engineering, please see List of engineering topics. For biographies please see List of engineers.

<span class="mw-page-title-main">Pasadena City Hall</span> Historic city hall of Pasadena, California, U.S.

Pasadena City Hall is the historic city hall of Pasadena, California, United States. Completed in 1927, it combines elements of both Mediterranean Revival and Spanish Colonial Revival style architecture, and is a significant architectural example of the City Beautiful movement of the 1920s.

A magnetorheological damper or magnetorheological shock absorber is a damper filled with magnetorheological fluid, which is controlled by a magnetic field, usually using an electromagnet. This allows the damping characteristics of the shock absorber to be continuously controlled by varying the power of the electromagnet. Fluid viscosity increases within the damper as electromagnet intensity increases. This type of shock absorber has several applications, most notably in semi-active vehicle suspensions which may adapt to road conditions, as they are monitored through sensors in the vehicle, and in prosthetic limbs.

<span class="mw-page-title-main">National Center for Research on Earthquake Engineering</span> Research center in Daan, Taipei, Taiwan

National Center for Research on Earthquake Engineering is an organisation in Da'an District, Taipei, Taiwan.

<span class="mw-page-title-main">Seismic vibration control</span>

In earthquake engineering, vibration control is a set of technical means aimed to mitigate seismic impacts in building and non-building structures.

Ground–structure interaction (SSI) consists of the interaction between soil (ground) and a structure built upon it. It is primarily an exchange of mutual stress, whereby the movement of the ground-structure system is influenced by both the type of ground and the type of structure. This is especially applicable to areas of seismic activity. Various combinations of soil and structure can either amplify or diminish movement and subsequent damage. A building on stiff ground rather than deformable ground will tend to suffer greater damage. A second interaction effect, tied to mechanical properties of soil, is the sinking of foundations, worsened by a seismic event. This phenomenon is called soil liquefaction.

An unreinforced masonry building is a type of building where load bearing walls, non-load bearing walls or other structures, such as chimneys, are made of brick, cinderblock, tiles, adobe or other masonry material that is not braced by reinforcing material, such as rebar in a concrete or cinderblock. The term is used in earthquake engineering as a classification of certain structures for earthquake safety purposes, and is subject to minor variation from place to place.

<span class="mw-page-title-main">Earthquake-resistant structures</span> Structures designed to protect buildings from earthquakes

Earthquake-resistant or aseismic structures are designed to protect buildings to some or greater extent from earthquakes. While no structure can be entirely impervious to earthquake damage, the goal of earthquake engineering is to erect structures that fare better during seismic activity than their conventional counterparts. According to building codes, earthquake-resistant structures are intended to withstand the largest earthquake of a certain probability that is likely to occur at their location. This means the loss of life should be minimized by preventing collapse of the buildings for rare earthquakes while the loss of the functionality should be limited for more frequent ones.

A metallic roller bearing is a base isolation device which is intended for protection of various building and non-building structures against potentially damaging lateral impacts of strong earthquakes.

<span class="mw-page-title-main">Oakland City Hall</span> Government offices in Oakland, California

Oakland City Hall is the seat of government for the city of Oakland, California. The current building was completed in 1914, and replaced a prior building that stood on what is now Frank H. Ogawa Plaza. Standing at the height of 320 feet (98 m), it was the first high-rise government building in the United States. At the time it was built, it was also the tallest building west of the Mississippi River. The City Hall is depicted on the city seal of Oakland.

William Henry Robinson was a New Zealand scientist and seismic engineer who invented the lead rubber bearing seismic isolation device. He grew up in West Auckland, New Zealand. He earned a master's degree at the Ardmore School of Engineering, then a PhD in physical metallurgy at the University of Illinois. Robinson was director of the DSIR's Physics and Engineering Laboratory between 1985 and 1991. He continued to invent and develop seismic isolation devices, travel and lecture until his early 70s.

A buckling-restrained brace (BRB) is a structural brace in a building, designed to allow the building to withstand cyclical lateral loadings, typically earthquake-induced loading. It consists of a slender steel core, a concrete casing designed to continuously support the core and prevent buckling under axial compression, and an interface region that prevents undesired interactions between the two. Braced frames that use BRBs – known as buckling-restrained braced frames, or BRBFs – have significant advantages over typical braced frames.

<span class="mw-page-title-main">Medhat Haroun</span> Egyptian-American expert on earthquake engineering

Medhat Haroun was an Egyptian-American expert on earthquake engineering. He wrote more than 300 technical papers and received the Charles Martin Duke Lifeline Earthquake Engineering Award (2006) and the Walter Huber Civil Engineering Research Prize (1992) from the American Society of Civil Engineers.

<span class="mw-page-title-main">Michael Constantinou</span> American structural engineer

Michael C. Constantinou is an American structural engineer who is a Samuel P. Capen Professor and State University of New York Distinguished Professor in the Department of Civil, Structural and Environmental Engineering at the University at Buffalo. He also serves an editor of the Journal of Earthquake Engineering and Structural Dynamics

Andrew Stuart Whittaker is an American structural engineer who is currently a SUNY Distinguished Professor in the Department of Civil, Structural and Environmental Engineering at the University at Buffalo, State University of New York.

<span class="mw-page-title-main">Kit Miyamoto</span> Japanese American structural engineer (born 1963)

Dr. Hideki "Kit" Miyamoto is a Japanese American structural engineer known for being the founder-CEO of Miyamoto International, a global structural engineering and disaster risk reduction organization. He is also the chairman of California's Alfred E. Alquist Seismic Safety Commission, which investigates earthquakes and recommends policies for risk reduction.

References

  1. ↑ "Los Angeles City Hall Seismic Rehabilitation Project – Base Isolation Technology". Archived from the original on 27 July 2011.
  2. ↑ "Nabih Youssef Associates | Structural Engineers". www.nyase.com. Retrieved 2017-06-11.
  3. ↑ Pressman, Andy (2007). Architectural Graphic Standards. John Wiley and Sons. p. 30. ISBN   978-0-471-70091-3.
  4. ↑ Webster, Anthony C. (1994). Technological Advance in Japanese Building Design and Construction. American Society of Civil Engineers. p. 70. ISBN   978-0-87262-932-5.
  5. ↑ Datta, T. K. (2010). Seismic Analysis of Structures. John Wiley and Sons. p. 369. ISBN   978-0-470-82462-7.
  6. ↑ "Base isolation: video demonstration". Archived from the original on 2021-12-12 – via www.youtube.com.
  7. ↑ Lead Rubber Bearing being tested at the UCSD Caltrans-SRMD facility, YouTube
  8. ↑ Hybrid Simulation of Base Isolated Structures, YouTube
  9. ↑ "Projects". www.siecorp.com.
  10. ↑ Reitherman, Robert (2012). Earthquakes and Engineers: An International History. Reston, VA: ASCE Press. ISBN   9780784410622.
  11. ↑ "Seismic Isolation |[ THK || Global English ]". www.thk.com.
  12. ↑ Base Isolation selected resources, https://www.ccanz.org.nz/page/Base-Isolation.aspx
  13. ↑ Robinson Research Institute, https://www.victoria.ac.nz/robinson/about/bill-robinson
  14. ↑ Masoumi, Mohammad Mehdi (2016-03-31). "Ancient Base Isolation System in Mausoleum of Cyrus the Great". International Journal of Earthquake Engineering and Hazard Mitigation (IREHM). 4 (1). ISSN   2282-6912. Archived from the original on 2018-03-29. Retrieved 2017-06-11.
  15. ↑ Llunji, Mentor (2016). Seismic Architecture - The architecture of earthquake resistant structures. Msproject. ISBN   9789940979409.
  16. ↑ nees@berkeley project highlight: NEES TIPS Seismic Isolation Hybrid Simulation, https://www.youtube.com/watch?v=Uh6l5Jqtp0c
  17. ↑ Giovannardi, Fausto; Guisasola, Adriana (2013). "Base isolation: dalle origini ai giorni nostri" . Retrieved October 7, 2013.
  18. ↑ Yang, G.; Spencer, B.F.; Carlson, J.D.; Sain, M.K. (March 2002). "Large-scale MR fluid dampers: modeling and dynamic performance considerations" (PDF). Engineering Structures. 24 (3): 309–323. CiteSeerX   10.1.1.486.9615 . doi:10.1016/S0141-0296(01)00097-9.
  19. ↑ Behrooz, Majid; Wang, Xiaojie; Gordaninejad, Faramarz (1 April 2014). "Performance of a new magnetorheological elastomer isolation system". Smart Materials and Structures. 23 (4): 045014. Bibcode:2014SMaS...23d5014B. doi:10.1088/0964-1726/23/4/045014.
  20. ↑ "San Francisco International Airport: International Terminal – Enclos". enclos.com. Retrieved 2021-01-18.
  21. ↑ "Fact Sheet – International Terminal" (PDF). flySFO.com. San Francisco International Airport. January 30, 2007. Archived from the original (PDF) on May 21, 2009. Retrieved August 3, 2009.
  22. ↑ Doxey, Jessica. "Salt Lake Temple Renovation – What to Expect". Temple Square. Temple Square Hospitality Corporation. Retrieved 18 October 2020.
  23. ↑ "Temples: California's First Quake-Ready Stone Temple - Magazine Web Edition July/August/September 2013 - Publications - Hinduism Today Magazine". www.hinduismtoday.com. July 2013. Retrieved 2021-04-15.
  24. ↑ "Dynamic Isolation Systems - Applications". www.dis-inc.com. Retrieved 2021-04-15.
  25. ↑ "New BAPS mandir combines best of architecture & technology | India Post News Paper". 2013-01-02. Retrieved 2021-04-15.
  26. ↑ Fuller, Thomas (4 June 2019). "Inside Apple's Earthquake-Ready Headquarters". The New York Times.
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