NISEE – the national information service for earthquake engineering

The ability of available, performance-based, analytical methods to predict reliably the performance of building structural systems in a major earthquake (mainshocks) and subsequent triggered aftershocks, (or other cascading hazard events) concerns earthquake engineering research. The possible damage to structures from cascading, shallow-focused, seismic events was provoked by the collapse of the CTV Building in the 22 February 2011, the Canterbury (Christchurch) region of New Zealand earthquake (Mw=6.3). That earthquake had followed the 4 September, 2010 Darfield earthquake (Mw=7.1) in the same region and a series of fairly strong aftershocks. (See: Forsyth Barr/CTV Building hearing:
Expert Panel Report: Structural Performance of Christchurch CBD Buildings in 22 February 2011 Aftershock.)

CTV Building, Christchurch, NZ before February 2011 earthquake

CTV Building, Christchurch, NZ after February 2011 earthquake

Analytically derived performance predictions (including “blind prediction competitions”) have achieved only mixed success with full scale experimental seismic testing results, — for example in Japan’s E-defense full-scale shaking table testing of steel moment frames –

Lignos, D.G., Hikino, T., Matsuoka, Y., and Nakashima, M., “Collapse assessment of steel moment frames based on E-Defense full-scale shake table collapse tests”, Journal of Structural Engineering, ASCE, 139:120-132; (2013)

Maison, B., Kasai, K., and Deierlein, G. “Study of building collapse for performance-based design validation.” Structures Congress 2008: Crossing Borders. pp. 1-10 (ASCE : 2008);

Lignos, D.G. (2012). “Modeling and experimental validation of a full scale 5-story steel building equipped with triple friction pendulum bearings: E-Defense blind analysis competition,” Proceedings 9th, International Conference on Urban Earthquake Engineering (9CUEE) & 4th Asia Conference on Earthquake Engineering, Tokyo, Japan; March 6-8, 2012.

Using reduced-scale models in shaking table testing at the University at Buffalo for validation, analytical performance predictions for four-story steel moment frames provided guarded success —

Lignos, D.G., Krawinkler, H., Whittaker, A.S. “Contributions to collapse prediction of steel moment frames through recent earthquake simulator collapse tests.” 3rd International Conference on Advances in Experimental Structural Engineering, October 15-16, 2009. San Francisco. (October, 2009).

A recent blind prediction competition using shake table testing of a full-scale, reinforced concrete bridge column subjected to six consecutive unidirectional ground motions at U.C. San Diego test facilities produced a wide variance in validity of performance predictions. —

Terzic, V., Schoettler, M., and Mahin, S.A. “Uncertainty in modeling seismic response of reinforced concrete bridge columns.” 9th International Conference on Urban Earthquake Engineering/ 4th Asia Conference on Earthquake Engineering, Tokyo Institute of Technology, Tokyo, Japan (2012).

For taller buildings (at least 160 feet in height), too large for reasonable laboratory shake table testing, the PEER/ATC-72-1 report : (Malley, J. et al) “Modeling and acceptance criteria … “ (2010), provides a near, ‘state-of-the-art’ compendium of recent available research, information, and recommendations on analytical modeling and acceptance criteria for the design and analysis of tall structural systems. Some methodologies for damage assessment of mid-rise building structural systems under cascading seismic events have also been elaborated in a variety of research studies — See for example:

Luco, N., Gerstenberger, M.C., Uma, S., Ryu, H., Liel, A.B., and Raghunandan, M. “A methodology for post-mainshock probabilistic assessment of building collapse risk.” Pacific Conference on Earthquake Engineering, Auckland, New Zealand (April, 2011).

Lee, K. and Foutch, D. “Performance evaluation of damaged steel frame buildings subjected to seismic loads.” Journal of Structural Engineering (ASCE), 130(4), 588–599. (April, 2004);

Li, Q. and Ellingwood, B.R. “Performance evaluation and damage assessment of steel frame buildings under main shock-aftershock earthquake sequences.” Earthquake Engineering & Structural Dynamics, 36(3), 405–427. (March, 2007).

M. Raghunandan, Liel, A.B.,Ryu, H., Luco, N., Uma, S.R. “Aftershock fragility curves and tagging assessments for a mainshock-damaged building.” Proceedings of the 15th World Conference in Earthquake Engineering (15WCEE), September 24-28, Lisbon, Portugal, 2012.

Eads, L., Miranda, E., Krawinkler, H., Lignos, D.G., (2012). “Improved estimation of collapse risk for structures in seismic regions,” Proceedings of the 15th World Conference of Earthquake Engineering (15WCEE), September 24-28, Lisbon, Portugal, 2012.

The complex challenges in accurately modeling the expected mainshock and aftershock seismic sequences for use in structural and non-structural damage analytical assessment prediction are recognized in recent work including –

Baker, J.W. “Probabilistic structural response assessment using vector-valued intensity measures.” Earthquake Engineering & Structural Dynamics, 36(13), 1861–1883; (9 May, 2007).

Ruiz-García, J. “Mainshock-aftershock ground motion features and their influence in building’s seismic response.” Journal of Earthquake Engineering, 16(5), 719-737; (26 June, 2012).

Work on improved analytical methods for reliable prediction of structural systems performance under realistic, cascading seismic events continues widely.

Most famous in earthquake mythology is the enormous subterranean catfish of ancient Japan whose sudden movements were reflected in surface ground movement until the fish could be subdued by superior force. (See images– NM0468, KZA63, KZA65, KZA66, etc.) Unveiling a modern earthquake view where great, unseen, natural forces of convection, gravity and friction act on large subterranean tectonic blocks in measureable and probabilistic ways may not have proved such a great phenomenological leap from the restrained catfish explanation for Japanese earthquake engineering. This opinion seems supported by the juxtaposition of the assembled contemporary warriors in business suits with the mythical catfish image offered in the printed version of the program at the March 2013, 10th International Conference of Urban Earthquake Engineering (CUEE – Tokyo Institute of Technology). Engineering technique now subdues natural forces.

Unrelated, recently the NISEE e-library received a request for a 1991 paper [International Workshop on Concrete Shear in Earthquake (University of Houston, TX) -- a solid workshop mysteriously absent of any California representation] in which Professor Michael P. Collins of the University of Toronto illustrated the engineering quest for a “rational model for shear [that] should make it possible to predict not only the shear strength but also the complete load-deformation response of elements subjected to shear… such a theory should be capable of being extended to the seismic situation of reversed, cyclic loading,” with a graphical representation of the number of technical papers dedicated to the shear design of concrete in one journal since the first paper on this topic in 1899.

Despite very considerable research accomplishment between 1899 and 1991 and subsequently (for example — M.P. Collins in 1996 (ACI) which re-uses this graphic), a cursory review of contemporary ACI Journals may suggest the quest and support for concrete shear design theory and practice continues apace.

Hospital reconstruction and seismic strengthening provided continuous demand for construction design and engineering services in recent years. (See NISEE, Dec 9, 2011) In California, compliance with mandatory seismic performance objectives for critical health care facilities is largely supervised through the California Office of Statewide Planning and Development (OSPD). A hospital’s ability to function adequately after a large earthquake is dependent on the building’s structural components (a building’s primary load carrying system of foundation, columns, beams, floors, walls and roof), non-structural components (building elements such as ceilings, partitions, pipes, mechanical and electrical, that are not part of the structural load-bearing system), occupants (staff and patients) and contents (equipment, supplies, furnishings, etc.) remaining largely undamaged. Hospital serviceability after natural disaster relies on robust interconnectedness of lifeline systems (water, power, transportation, etc.) that support hospital services. The constitution of structural, non-structural and contents may provide unique seismic strengthening challenges for hospitals.

For seismic strengthening of modern hospital buildings, reliable site-specific loss estimation techniques (e.g.: Blume-157) can account for structural and non-structural damage. Engineering building codes (e.g.: ICBO, FEMA, California Building Codes), applied research programs (e.g.: ATC-58, MCEER, Japan E-Defense) and sophisticated testing methodologies to analyze and strengthen structural and many non-structural systems to resist moderate to strong earthquake shaking or geotechnical damage are reasonably advanced. Video of recent shake-table testing at the University of California, San Diego (‘Building it Better: Earthquake-Resilient Hospitals for the Future’) confirms some ability to achieve both structural and non-structural hospital resilience after credible earthquakes in California.

More precise seismic fragility functions for hospital building contents and medical equipment (Zolfaghari, Porter, Furukawa) exist but experimental testing and verification of equipment fragility curves are confounded by prohibitive costs of testing very expensive medical equipment to a complete damage state (from high floor accelerations or from building displacements).

Similarly, analytical assessments of regional medical systems interconnectedness after natural disaster have been proposed (Lupoi, G. , Lupoi, A.) but can be fully tested only after a strong regional earthquake.

Damaged Olive View Medical Facility, Sylmar, CA, 1971

Veterans Administration Hospital, Sylmar, CA, 1971

Since at least the 1971 San Fernando, California Earthquake (M=6.6), engineering investigation has understood that multi-unit, wood frame, residential buildings with weak first stories that lack adequate lateral strength or stiffness (usually because of ground level parking space openings or commercial space store front openings) can pose significant risk of catastrophic leaning and collapse during strong earthquake ground shaking. In California, this knowledge has been reinforced by the 1989 Loma Prieta earthquake (M= 7.09) and the 1994 Northridge earthquake. (M=6.69)

Soft-story, multi-residential building, Los Angeles, 1971

Collapsed soft-story buildings, San Francisco, 1989

Collapsed soft-story building, Northridge, 1994 (from SEAONC)

In 2008, the Association of Bay Area Governments (ABAG) identified 24,273 at-risk units in 1,479 residential buildings with 5 or more units, 2 to 7 stories, built before 1991, and containing parking or commercial uses on the ground floor in the City of Oakland, California. A related ABAG statistical sample inferred the existence of more than 1,400 additional ‘potential soft story buildings’ with less than 5 residential units in Oakland. An NBC report in Los Angeles observed that according to Caltech engineers, there are “more than 20,000 soft-structure apartment buildings in the City of Los Angeles alone and only 800 of those have been seismically retrofitted, according to the LA Department of Building and Safety.”

Engineering research into the complexities and remediation methods for multi-unit, wood frame residential buildings with soft stories is extensive and has provided a variety of technical retrofit possibilities. Many municipalities have investigated the scope and jurisdiction of the soft-story problem. Regional non-profit organizations actively address awareness of multi-residential, soft-story building exposure to earthquake damage.

In May, 2012, FEMA released “Seismic Evaluation and Retrofit of Multi-Unit Wood-Frame Buildings With Weak First Stories” (FEMA P-807). These guidelines address seismic retrofit requirements for weak-story wood-frame buildings in seismically active regions of the United States, but with a particular focus on Northern and Southern California and the Pacific Northwest. These retrofitting guidelines are designed to focus on the weak first story in a building and to provide just enough additional strength to protect the first floor from collapse but not so much as to drive earthquake forces into the upper stories, placing them at risk of collapse. When well-implemented, the guidelines can take into account the building strength provided by existing non-structural walls. FEMA has subsidized technical training through the Applied Technology Council (ATC), the FEMA P-807 report authors, to expedite implementation of the guidelines.

Growing awareness of the vulnerability of multi-residential, soft-story buildings; the possibility of capable and comparatively-affordable retrofit technical solutions; the promulgation of standardized evaluation and implementation guidelines with training materials that address the specific problem; significant probable exposure of mostly non-property owning residents to seismic risk; and, political efforts by municipal authorities and agencies cannot accelerate addressing residential soft-story problems successfully without devising more efficient and equitable financial support strategies beyond traditional mechanisms.

[Since writing, a "Mandatory Soft Story Retrofit Ordinance" was unanimously approved by the Board of Supervisors of the City of San Francisco and will be signed into law by Mayor Ed Lee on April 17, 2013, the 107th Anniversary of the 1906 Great San Francisco Earthquake.]

Damaged Bridge, Costa Rica, 1991

Collapsed Bridge, Japan 1964

Collapsed Bridge, Chile, 1985

For modern bridge design, soil liquefaction (and related lateral spreading of soils) is an intensively-studied earthquake damage phenomenon. Current U.S. national design guides (NCHRP Report 472 | AASHTO Guide Specifications), highway bridge retrofit guides (Part 1- Bridges, | Part 2 – abutments, etc.) and many state bridge design guides (California | New York) include geotechnical seismic requirements for site specific soil profiles, site liquefaction potential, and liquefaction remediation. These engineering design requirements are typically supported by an array of complex research studies. For example A.Faris “Probabilistic Models… “ — MCEER-ATC “Liquefaction Study” — J.Bray and C.Ledezma “Performance based design…” — R.Seed et al. “Recent Advances…” — R.Boulanger and I.M.Idriss “Evaluating potential…” and many others. In a March, 2013 international bridge symposium paper, K.Tamura clearly outlines the recent history of Japanese bridge design codes responding to soil liquefaction problems following powerful earthquakes. The table below is adapted from Professor Tamura’s paper.

— History of Japanese Design Requirements of Highway Bridges for Soil Liquefaction —


With far fewer strong earthquakes than Japan on which to draw, U.S. seismic design guides for bridges rely heavily on shared international liquefaction data, on site specific empirical procedures, and on field and laboratory testing to achieve soil liquefaction prediction and remediation goals for a national road and highway bridge inventory of more than 600,000 (>20 ft. span) bridges.

Architectural View of Kamikuzawa-Condominium Project

Schematic Layout of Kamikuzawa-Condominium Seismic Isolation Bearings

Two of the Three Types of Bearings Used in Kamikuzawa-Condominium Construction

In earthquake engineering, seismic (or base) isolation includes the development of bearings whose primary purpose is to isolate the ground motion of earthquakes from the larger supported structure or superstructure in order to reduce inertia loads and internal stresses. To protect against damaging vibration effects of earthquake shaking, modern base isolation technologies are used in some buildings (including the San Francisco International Airport), more widely in highway bridges where research has pushed development (e.g.: HITEC Summary Report or AASHTO Guidelines) and will soon be applied to much mission-critical infrastructure (such as nuclear power plants). Seismic isolation is used in the USA and worldwide. (For further reading see: JM Kelly, ‘History of Base Isolation’ chapters in Wiley e-book or similar in CRCnetbase).

In seismic isolation applications, the horizontal flexibility of the isolation system increases the fundamental period of the supported structure and reduces inertial forces, often enabling the secondary systems to be designed for smaller forces and displacements. (See: NZ Science Learning media). Seismic isolation systems typically use either spring or elastomeric bearings from various manufacturers around the globe. Elastomeric bearings are engineered principally of laminated natural rubber, high damping rubber similar to the type of bearing used in this UC Berkeley building for example, neoprene as seen in this bridge bearing, lead core with laminated rubber layers or in similar metal core designs. In addition to elastomeric and spring-based bearings, steel sliding bearings (sometimes with Teflon coatings) are increasingly common.

An ambitious application of base isolation technology for the protection of multi-family residences is the design and construction of the Kamikuzawa-Juhtaku near Tokyo (often referred to as the
Kamikuzawa Condominiums, design completed by March, 2000 and pictured here courtesy of UCB Professor J. M. Kelly). This design features seismically isolated ‘artificial ground’ (effectively large and very stiff slabs of reinforced concrete resting on 242 bearings – three types of isolation bearings are used; 148 very large lead-rubber bearings, 109 sliding bearings, 48 smaller, ball bearing devices) supporting 21 apartment buildings in a community project. The site dimensions are about 125 m wide and 250 m in length. The project provides, 53,297 m2 of floor space and weighs approximately 111,600 tons above the seismic isolators. The condominiums are in use today.

View of Completed Kamikuzawa-Condominium Project

Completed Kamikuzawa-Condominium Site

View of Completed Kamikuzawa-Condominium Buildings

A new seismic source characterization model for the Central and Eastern United States (CEUS) is publicly available in a form suitable for use in Probabilistic Seismic Hazard Analysis (PSHA – for a PSHA example see NUREG/CR-6607) evaluations for regulatory activities (including Early Site Permit and Combined Operating License Applications for nuclear facilities). Input to a probabilistic seismic hazard analysis for nuclear facilities usually consists of both seismic source characterization and ground motion characterization [an objective of PEER NGA-East is to develop new ground motion characterization model for Central and Eastern North-America]. These characterizations are used to calculate probable hazard results (seismic hazard curves) at a particular site. The new CEUS seismic source model is based on improvements in available data and methods (USGS : Open-File Report 2011-1101).

CEUS Earthquake Catalog

The new CEUS source model replaces the Seismic Hazard Methodology for the Central and Eastern United States (NP-4726-1986 – paper volumes) and Seismic Hazard Characterization of 69 Nuclear Plant Sites East of Rocky Mountains (Bernreuter, 1989). The new seismic source model can be used in a Senior Seismic Hazard Analysis Committee (SSHAC, Budnitz, 1997) Level 3 assessment process as implemented by NUREG (Kammerer and Ake) in evaluating the seismic safety of nuclear facilities.

Two important American Society of Civil Engineers (ASCE) standards are also relevant for the structural engineering design and analysis of nuclear power plants: ASCE 4-98, “Seismic Analysis of Safety-Related Nuclear Structures and Commentary” and ASCE 43-05, “Seismic Design Criteria for Structures, Systems and Components in Nuclear Facilities” as well as a NUREG sponsored evaluation (NUREG/CR-6926 – 2007) of the latter ASCE standard.

The Oregon Seismic Safety Policy Advisory Commission (OSSPAC) has completed a comprehensive review of Oregon’s buildings, lifelines and community priorities to assess how to protect lives and commerce and facilitate recovery from a possible, M=9.0, Cascadia earthquake and tsunami. The “Oregon Resilience Plan” (Executive Summary) maps an ambitious, fifty-year program of policy and investment priorities for the state to offset a predicted $32 billion loss and potentially high mortality rates in coastal Oregon from a large, subduction-zone earthquake and tsunami.
The last megathrust earthquake in the Pacific northwest was in January, 1700, just over 300 years ago. Geological evidence indicates that such great earthquakes have occurred at least seven times in the last 3,500 years, a return interval of 400 to 600 years (Pacific Northwest Seismic Network- PNSN). John J. Clague, “Evidence for large earthquakes at the Cascadia Subduction Zone” (AGU – Review of Geophysics, January 1997) observed that very large, historically unprecedented earthquakes at the Cascadia subduction zone in western North America have left signs of sudden land level change, tsunamis, and strong shaking in coastal sediments. The last earthquake or series of earthquakes is believed to have ruptured the entire 1000-km length of the subduction zone; if this was a single earthquake, it probably exceeded M=9.0. The Cascadia zone earthquake and tsunami recurrence intervals are uncertain because of difficulties in identifying and dating ancient earthquakes. In southwestern Washington state, intervals for the seven most recent earthquakes average about 500 years, but range from less than 200 years to 700–1300 years. It is believed that part of the plate boundary in the subduction border is locked and accumulating elastic strain that will be released during a future large earthquake. Oregon has been assessing its seismic vulnerabilities, especially to a Cascadia subduction event, since at least the 1980s. Assessments provided simulated strong ground motions for two likely Cascadia mega-earthquake scenarios, detailed highway bridge retrofit and strengthening planning and reviews of multi-jurisdictional tsunami warning systems. However, after the 2011 Tohoku (Japan) great earthquake and tsunami provided dramatic lessons for the Pacific Northwest in North America, this OSSPC initiative integrates seismic resilience planning for the State of Oregon under one updated report and starkly lays out the large investment decisions required to achieve greater resiliency. In addition to local and state planning efforts, in the U.S.A., the federal agency, NOAA, is charged with tsunami coastal hazard mitigation, inundation mapping and tsunami forecast. See for example NOAA Technical Memorandum OAR PMEL-135.

This example of popular, light concrete, gravity framed housing in Colombia is very vulnerable to earthquake shaking or hillslides -- (photo and linked report from image: Luis G. Mejia)

The World Housing Encyclopedia (WHE – multi-criteria search form), a collection of resources related to different housing construction practices in many seismically active areas of the world, attempts to encourage the use of earthquake-resistant housing technologies. Recently, the encyclopedia managers, the Earthquake Engineering Research Institute (EERI) and the Global Earthquake Model (GEM) published this request for assistance from knowledgeable builders, architects and engineers- The Global Earthquake Model and the World Housing Encyclopedia need your expertise to improve our understanding of the global building stock. You can do this by describing a building or building type in your country using a tool GEM has developed, called TaxT. Your participation will assist GEM in generating a comprehensive, global building taxonomy and further the science of seismic risk reduction. EERI intends to publish, after review, many of these short reports on the WHE website and GEM will also share outcomes. To read about and download the TaxT report form or visit – “http://www.world-housing.net/related-projects/share-your-knowledge-of-buildings”.

BuildChange, an international, non-profit social enterprise that designs earthquake-resistant houses in developing countries and trains local builders, homeowners, engineers, and government officials to build them may offer at least part of a solution to the recurring problem of seismically, unresistant housing located in seismically vulnerable countries of limited resources.

The 1999 – 2004 years of the PEER Center Research at UC Berkeley reflected the original research focus on hazardous concrete buildings (frequently termed ‘non-ductile concrete’ as in this 2008 Los Angeles inventory of hazardous buildings) through a strong series of researcher workshops that alternated between Japan and the U.S. annually. Reports from these workshops provide access to the advance of performance based earthquake engineering research in reinforced concrete building design and rehabilitation.

First U.S.-Japan Workshop on Performance-Based Earthquake Engineering Methodology for Reinforced Concrete Building Structures 1999 Second U.S.-Japan Workshop on Performance-Based Earthquake Engineering Methodology for Reinforced Concrete Building Structures 2000 Third U.S.-Japan Workshop on Performance-Based Earthquake Engineering Methodology for Reinforced Concrete Building Structures 2001 Fourth U.S.-Japan Workshop on Performance-Based Earthquake Engineering Methodology for Reinforced Concrete Building Structures 2002 Fifth U.S.-Japan Workshop on Performance-Based Earthquake Engineering Methodology for Reinforced Concrete Building Structures 2003

PEER 2000/10 Report

In 2004, an international performance based seismic design workshop was held in Bled, Slovenia reflecting the evolution of PEER’s research focus to broader, performance based earthquake engineering techniques and procedures for different structures and geotechnical environments –

Performance-Based Seismic Design: Concepts and Implementation, Proceedings of the International Workshop, Bled, Slovenia, 28 June-1 July 2004

The performance based approach to seismic engineering of structures was first outlined (in the U.S. at least) in the 1995 SEAOC – “Performance based seismic engineering of buildings – Vision 2000″ document.