Seismic Design and Regulations: Historical Evolution and Effectiveness Factors
Seismic Design and Regulations: Historical Evolution and Effectiveness Factors
Seismic events have devastated human life and property historically, inspiring people to seek ways of reducing their impact. Many populous regions in the world lie on seismically active sites, endangering people and property. Earthquakes the rolling, shaking and sudden shock of the surface of the earth, devastate and destroy through violent shaking of structures, ground failure such as faulting, subsidence and landslides, and tsunamis (Lorant, 2016). Indeed, some of the most devastating earthquakes in the world have occurred in highly populated areas, often located in coastal areas, necessitating the redesigning of building and other infrastructure to make then earthquake proof. In addition, regulations have been developed to help guide, enforce and entrench prudent design and construction codes in built spaces (Ishiyama, 2011). The ensuing discussion traces the historical evolution of seismic regulations and the landmark events in Greece, Japan and the United States that have inspired their development. After that, the effectiveness of these regulations globally alongside the socioeconomic factors the influence their effectiveness and the impact of earthquakes are discussed.
Catastrophic earthquakes and their impacts
Some devastating earthquakes have influenced the development of seismic design and regulation based on the sociopolitical environment at the location and period of occurrence (Reitherman, 2012). Notably, Greece, Japan and the United States have experienced significant historical seismic events that inspired the development of seismic designs and regulation to prevent future calamities, or at least, reduce the devastation from earthquakes to a minimum.
Greece lies at the boundary of the Anatolian plate and the Adria and Aegean microplates, which makes it experience small earthquakes every 2 to 3 days alongside occasional big magnitude ones (Kouskouna & Makropoulos, 2004). The 1953 earthquake at Cephalonia is significant because it instigated the development of the first Greek Seismic Code back in 1959 (Nikolaou, 2015). This law has been the backbone of the seismic regulatory framework at the country.
The Kalamata earthquake of 1986 caused the reexamination of the building codes on high-risk zones, with higher seismic coefficients being proposed. In addition, the earth highlighted the need for anti-seismic urban planning and land-use laws, and an institutional framework for reconstruction (Theofili & Arellano, 2001). imilarly, the Grevena-Kozani earthquake of 1995 caused some minor reforms to the 1992 anti-seismic regulation. The earthquake also instigated the urgent modification to the National Earthquake Building Code Map and the updating of neotectonic mapping and microzonation studies (Theofili & Arellano, 2001). The Egio earthquake of 1995 reinforced the recommendation made after the Grevena-Kozani earthquake. In addition, the earthquake instigated the need periodic maintenance and safety checks for all buildings, and the systematic enforcement of building codes in the country. Also, a national inventory and database of resources, and the communication of accesses and escape routes were created after the event (Theofili & Arellano, 2001).
The Mt Parnitha earthquake in Attica in 1999 caused the New Greek Seismic Design Code of 1995, the Reinforced Concrete Code and the Concrete Technology Code to be revised. The resultant codes included the Greek Earthquake Design Code of 2000 and the revised Reinforced Concrete Code of 2001. As such, structure constructed using the seismic design code of 1959 and the New Greek Seismic Design Code had to be retested. Moreover, the event highlighted the importance of geological, geotechnical studies and seismic microzoning studies as a mandatory accompaniment of urban land-use and planning. Moreover, seismic safety considerations were to be included in the Code for the Design of Non-Structural Elements and the General Building Code because of their influence on building design (Theofili & Arellano, 2001). The two earthquakes that ravaged the Cephalonia Island in Greece in 2014 provided an opportunity to evaluate the effectiveness of the Greek building codes. Two to three story reinforced concrete buildings constructed under the local seismic code withstood the onslaught. However, the collaboration between the Greeks and the Americans ushered an era of collaborative reconnaissance in which resilience observation drove studies rather than failure of structures (Nikolaou, 2015).
However, Greece has to conform to the European Union codes and regulations, also known as the Eurocode. According to the European code, Greece lies on the highest seismic zone in Europe and therefore construction must adhere to the codes. Nonetheless, the local code is more stringent than the Eurocode 8 (Nikolaou, 2015).
Japan lies on the seismically active part of the eastern side of the ring of fire that surrounds the Pacific Ocean. However, despite its vulnerable location, the country has created one of the most disaster-resilient and safest built environments in the world, through continuous improvement from the lessons learnt from earthquakes (World Bank).
The Mino-Owari earthquake of 1891 in Nobi demonstrated that earthquakes can be caused by faulting in just the same way earthquakes cause faulting (Reitherman, 2008). The magnitude 8 earthquake occurred on the Midori fault of the Nobi fault system, causing over 7,000 deaths
The 7.9-magnitude Kanto earthquake of 1923 informed the modification of the 1963 Building Standard Law, by requiring that the designs and construction of all high-rise buildings be approved by the Minister of Construction (Otani, 2004). In addition, the design seismic coefficient of 0.1 was introduced in the revised urban building law enforcement regulations of 1924. This limited the height of reinforced concrete structures to 20 meters even after the Second World War and was included in the Building Standard Law Enforcement Order of 1950. Notably, the Building Standard Law became a national level in this year. The height limitation remained in force until 1963.
The Tokachi-Oki earthquake of 1968 exposed the weakness of reinforced concrete structures, instigating research frenzy. The studies helped improve the shear design of reinforced concrete pillars and members, and saw the development of steel-encased reinforced concrete (SRC) and concrete-filled tube (CFT) column systems thereafter (Otani, 2004).
The Hanshin-Awaji earthquake of 1995 in Kobe served as a test for the seismic design and building codes in Japan. The event revealed that 76 % of the buildings that collapsed were constructed before 1971, while only 3 % of the collapsed buildings were built after 1981. Likewise, the Hyogoken-Nanby earthquake of 1995 in Kobe evidenced the shear failure of concrete from the collapse of bridges. The seismic designs developed hereafter focused on improving the shear strength of members to prevent failure.
The western end of United States sits on the eastern part of the ring of fire, although the country has an active intraplate region to the east of the Rocky Mountains as well. The San Francisco earthquake of 1906 led to the development of the elastic rebound law, which enables geologists to estimate the magnitude of the earthquake from the fault length (Reitherman, 2008). The magnitude 7.9 quake destroyed 80 % of the city and caused about 3,000 fatalities destroying property worth 350 million dollars at the time. However, the event did not instigate any changes in building regulations immediately.
The Long Beach Earthquake of 1933 instigated the formulation of the Field Act, which required schools adhere to the seismic building code provisions that were managed by the state (Ishiyama, 2011). This seismic event also advanced earthquake engineering by generating data on reinforced concrete structures, a technology that had been in existence for more than four decades (Laghi et al., 2017). Also, the Riley Act was enacted, setting forth the development of seismic code in the United States (Reitherman, 2012). The San Fernando earthquake of 1977 devastated unexpectedly, many structures designed and built according to the current codes at the time. The National Earthquake Hazards Reduction Program was set up to champion the improvement of building codes and the construction environment to forestall a recurrence of the devastation. The program facilitated the enactment of National Earthquake Hazards Reduction Act in the same year (Anderson & Naeim, 2012).
Designs for earthquake resilience have also developed over time as new building material emerged. For instance, stone and bricks limited the height of buildings because they lacked the ability to withstand shear forces. Steel rigid frames appeared in construction towards the end of the 19th century, when steel was abundant and the urge to go higher was overpowering (Laghi et al., 2017). These structures allowed the tall buildings, which experienced internal action because of lateral loads, to have flexural and shear strength. Notably, the cantilever system characterized the structural skeleton of the buildings. However, to construct building higher than 10 stories, which was the limit for the frames structure, tubular, core-supported, bundled tubes and modular structures proved to be more efficient (Ishiyama, 2011). Notably, the tube structure, when incorporated with steel and concrete presented one of the most earthquake-resilient buildings. The shear wall structure in the form of reinforced concrete walls has superior earthquake because of the ductile behavior. Its rigidity and large lateral strength reduce the sophistication and detailing complexity required in the designs.
The traditional reinforced concrete was improved in the 1940s to ferrocement by using meshed metallic grid rather than iron bars. The meshed structure embedded in cement provided food compression and tension behavior, which enhance earthquake resilience. Insulating Concrete Forms (ICF) are the more recent earthquake resistant building materials that have been developed for earthquake prone regions. Their low cost and design flexibility due to the use of expanded polystyrene synthetized (EPS) has made the appropriate and popular in developing countries (Laghi et al. 2017).
The Creation and Development of Seismic Regulations
Japan developed its first building code in 1919, which required that all building be designed for a seismic coefficient of 0.1. Seismic coefficient is determined dividing the estimated maximum ground acceleration by the safety factor of allowable stress. This code was incorporated into the building standard law in Japan in 1950 and contributed to the development of seismic codes globally (Pitilakis, 2018).
The earthquake engineering research institute (EERI) was established in 1948 in the United States, and introduced earthquake engineering in place of engineering seismology (Reitherman, 2008). This recognized the nexus between seismology and engineering, and its importance in addressing the effects of earthquakes on human environments. The royal decree of the seismic code for building structures is the first seismic code in Greece, enacted in 1959 to assess the seismic response of built structures (Maraveas, 2019). Likewise, the National Earthquake Hazards Reduction Act of 1977 called for the establishment of seismological studies, early prediction systems, hazard reduction programs in recognition of the need to go beyond seismic engineering (Anderson & Naeim, 2012).
The number of seismic building codes regulations have increased over time as seismic knowledge expands, as illustrated in figure 1. As such, codes are increasingly weightier as they include standards and professional practice guidelines (Reitherman, 2008). The upsurge in the 1960s is attributed to the availability of computers and software for seismic analysis (Pitilakis, 2018).
Figure 1. Number of seismic codes developed globally since 1960
Source: Reitherman (2008)
In the United States, seismic codes developed at the local level before being adopted nationally. The first codes were developed Palo Alto and Santa Barbara in California in 1925, while seismic design provisions were not written until 1927. These were consolidated into the three main regional building codes in the country in the 1900s, namely the building code congress international (SBCCI), the National Building Code, also known as the BOCA Code by the building officials and code administrators (BOCA), and the Uniform Building Code (UBC) by the international conference of building officials (Anderson & Naeim, 2012).
Two regulatory framework approaches have evolved over time; one where the building standards are embedded in law and the other where building standards are developed by nongovernmental organizations outside law. Japan embeds its building standards in law while the United States and Greece prefer separating the building codes and standards from the building laws (World Bank). The advantage of embedded standards is the guaranteeing of minimum safety standards and the facilitation of compliance and control in low-capacity environments. However, revisions of the frameworks are difficult, complex, and time consuming, and thus not responsive to rapid changes in built circumstances or seismic knowledge. In turn, the separated regulatory structure facilitates revision and design flexibility, although they require authorities to be conversant with the technical details therein (World Bank).
Effectiveness of Earthquake Regulation
Earthquake design and regulation are aimed at not only informing the development of structures in a country to ensure that they are earthquake resistant but also guaranteeing the safety of people and their property. Indeed, earthquake-related designs and regulations were motivated by devastating earthquakes that occurred when earthquake engineering could benefit from the added knowledge and when the political environment was least resistant to earth-quake proof construction laws (Reitherman, 2012). Therefore, at the onset, earthquake engineering advancements is sensitive to the sociopolitical environment in a country at the time of a significant seismic event. Interestingly, many earthquake designs and regulations from the advancement of earthquake engineering have been inspired by other sociopolitical aspects other than the momentous earthquakes themselves. For instance, increased research, education and implementation of earthquake engineering knowledge in China occurred after the demise of Mao Zedong in 1976, despite the occurrence of the Tangshan Earthquake in the same year (Reitherman, 2012). This is because during Mao’s regime, the political ideology favored populism over science and engineering, hindering the advancement of earthquake engineering in the country at the time. Moreover, the reforms undertaken by Deng Xiaopin, who succeeded Mao, led to a construction boom, which necessitated the application of earthquake engineering knowledge (Reitherman, 2012).
The effectiveness of the seismic designs and regulations are influenced by the country in which they are implemented. The transferability of the designs and laws across countries is hindered by the differences in building materials, construction details, construction sites, local standards and codes and socioeconomic factors such as budgets and culture. Moreover, the data collected from buildings and other structures in one country during an earthquake cannot be transferred to another structure in a different country because the structures differ. Furthermore, differences in methodologies among earthquake engineers challenge the replication of findings from one country to another, despite the existence of global organizations such as the International Association for Earthquake Engineers.
The socioeconomic status of a country can determine the effectiveness of the seismic regulations. There is no doubt that poor countries suffer more from earthquakes than wealthy ones, as was demonstrated by the Haiti earthquake of 2010. Booth (2018) observed that Haiti was terribly devastated compared to Chile in 2010, although Chile experienced a stronger earthquake. The Haiti event had at least 100,000 fatalities while in the Chile one, 525 people died. The engineering properties of the physical infrastructure in Haiti were poor reflecting a resource-scarce country. Moreover, earthquakes are often accompanied by fires, tsunamis, mudslides and flooding, which add another dimension to structural resilience other than that focused on the violent shaking of ground (Booth, 2018). This indicates that erecting earthquake-proof buildings requires capital and political commitment despite the presence of enabling technologies and standards (Booth, 2018). Moreover, the diversity and inclusivity in the earthquake engineering teams and among politicians fan influence the effectiveness of the building codes for earthquake resilience. Booth (2018) argues that earthquakes affect people and therefore seismic engineers should learn to deal with people, an area women perform better than men despite being underrepresented in the profession. The unpredictability of earthquakes require effective communication about the benefits and limits of seismic engineering, and a diverse engineering team comprising is people of different gender, race, ethnicity, social standing and such like strata could be more effective communicators. Moreover, residential building may be expanded according to increasing family size over time. Unfortunately, these modifications may be undertaken under different building codes and regulations, making the structures lack uniform resilience (Nikolaou, 2015).
Seismic engineering has facilitated the development of designs and regulation facilitating the construction of earthquake-resilient buildings. Earthquakes and the great devastations they cause have been valuable in advancing seismic engineering as an autonomous field alongside facilitating the development of earthquake-proof designs and supporting regulations. Greece, Japan and the United States have faced many different seismic events that have contributed to the evolution of building standards in the countries and globally as well. Moreover, the earthquakes have afforded the engineers opportunities to test the resilience of new building materials and designs to improve the structural stability and longevity of buildings. However, earthquake-proof construction is expensive, which may render earthquake-resilience regulations ineffective in poorly-resourced countries. Moreover, the diminishing quality land for construction upon population increase pressures makes some seismic designs untenable. Indeed, countries like Japan has succeeded in creating habitable environments in seismically active areas because of the integration of building codes and regulation alongside the political commitment to direct resources to enhancing earthquake resilience in the country. Unfortunately, developing countries with limited resources may continue to be devastated by earthquakes because of their low socioeconomic status, which hinders their ability to domesticate and enforce the new building technologies and standards available in the construction industry globally.
Anderson, J. C., & Naeim, F. (2012). Basic structural dynamics. John Wiley & Sons.
Beavers, J. E. (2002). A review of seismic hazard description in US design codes and procedures. Progress in Structural Engineering and Materials, 4(1), 46-63.
Booth, E. (2018). Dealing with earthquakes: the practice of seismic engineering ‘as if people mattered’. Bulletin of earthquake engineering, 16(4), 1661-1724.
Ishiyama, Y. (2011). Introduction to earthquake engineering and seismic codes in the world. Hokkaido University, Hokkaido, Japan.
Kouskouna, V. & Makropoulos, K. (2004). Historical earthquake investigations in Greece. Annuls of Geophysics, 47(2.3), 723-731.
Laghi, V., Palermo, M., Trombetti, T., & Schildkamp, M. (2017). Seismic-proof buildings in developing countries. Frontiers in Built Environment, 3(49), 1-12.
Lorant, G. (2016). Seismic design principles. National Institute of Building Sciences. Retrieved from https://www.wbdg.org/resources/seismic-design-principles.
Maraveas, C. (2019). Assessment and Restoration of an Earthquake-Damaged Historical Masonry Building. Frontiers in Built Environment, 5, 112.
Nikolaou, S. (2015). Learning from structural success rather than failures. Structure. Retrieved from https://www.structuremag.org/?p=8211.
Otani, S. (2004). Japanese seismic design of high-rise reinforced concrete buildings: an example of performance based design code and state of practices. In Proceedings, 13th World Conference on Earthquake Engineering.
Pitilakis, K. (2018). Recent advancements in earthquake engineering in Europe. Geotechnical, Geological and Earthquake Engineering 46,
Reitherman, R. (2008). International aspects of the history of earthquake engineering. Earthquake Engineering Research Institute. California.
The World Bank (n.d.). Building regulation for resilience: Converting disaster experience into a safer built environment – the case of Japan. Global Facility for Disaster Reduction and Recovery.
Theofili, C. & Arellano, L. V. (2001). Lessons learnt from earthquake disasters that occurred in Greece-Nedies project. European Commission. Retrieved from https://www.preventionweb.net/files/1497_Earthquakes20Report20with20logo.pdf.