Design regulations#
Australia#
Seismic design regulations were first introduced in 1979, therefore buildings constructed prior to 1980 are considered “low” code and buildings constructed after 1980 are considered “moderate” code. Even though not all regions implemented the seismic regulations, wind resistance was mandated and likely offers some improvement in the seismic performance of buildings constructed after 1980. In 1993 and 2008, further improvements were made to the seismic design regulations in Australia.
New Zealand#
The development of earthquake engineering in New Zealand started after major earthquakes that occurred in the late 20s and early 30s, in particular the 1931 Hawke’s Bay earthquake (Davenport, 2004). According to the “Draft General Earthquake Building By-Law”, buildings were required to have a “Strength against Horizontal Force”, meaning all buildings were required to withstand a continuously applied horizontal force in any direction of not less than 0.08 of the weight above the level considered. No limits were set for seismic displacements or inter-storey drifts. Masonry was not permitted for the construction of large buildings for public meetings. (MacRae et al. 2011)
Loading requirements remained similar until 1965, when the NZSS 1900 was introduced as the New Zealand Standard Model Building By law. The primary method for simulating seismic response at this point was the inverted triangle static method, although the code allowed more advanced dynamic analysis for special structures. (Beattie et al. 2008). The lateral force coefficient varied with the structure period and according to the seismic zones, which were introduced in this code.
Revision of the loading requirements was given in “NZS 4203:1976 Code of practice for General Structural Design and Design Loadings for Buildings”. Whereas the previous code (1965) was based on working stress design, the 1976 code emphasised the ultimate strength design method. (Davenport, 2004) Both the elastic static procedure and elastic modal response spectra analysis methods were permitted. Design forces were based on a displacement ductility capacity, but the distinction between member and system ductility capacity was not clearly made. (MacRae et al. 2011) The revision of NZS 4203 in 1984 introduced the design return period of 150 years for buildings of normal importance. The inter-storey drift demands were calculated by equivalent static analysis and limited to control possible adverse P-delta actions. (MacRae et al. 2011)
The recommendations and provisions in place until 1992 did not apply automatically, as the building by-laws issued needed to be adopted by local authorities. For this reason, until 1992 there was no national building standard, although by-laws were adopted by most but not all local authorities. (Davenport, 2004)
The 1992 code (NZS 4203: “Code of Practice for General Structural Design and Design Loadings for Buildings”) represented a major revision of the earthquake loadings, introducing limit state design. The ultimate limit state had requirements to protect life and ensure the building would not collapse in a major earthquake, while the serviceability limit state requirements were to protect the building from structural damage and limit the damage sustained by non-structural components in moderate earthquakes. (Davenport, 2004) The design return period was set to 500 years for buildings of normal importance under ultimate seismic actions. Three different structural ductility types were considered, as well as different soil foundation conditions. The seismic zone contour map was revised, and P-delta actions were required to be considered explicitly. The inter-storey drift was calculated using inelastic time history analysis or elastic analysis methods. (MacRae et al. 2011)
In the 2004 code, the method of calculating lateral displacements, allowing for inelastic deformation, remains the same as in the 1992 code, but allows integration of P-delta effects into the standard. The structural performance factor is redefined, and design forces are reduced in proportion to the design ductility. The code also sets requirements for capacity design.
US territories (American Samoa, Guam and Northern Mariana Islands)#
Adoption of the International Building Codes by the unincorporated territories of the US often lags, mainly because smaller communities have difficulties in finding the resources to keep up with frequent building codes updates. In Guam, the transition from the 1994 edition of the Uniform Building Code (UBC) to the 2009 edition of the International Building Code (IBC) was initiated in 2010 (Baldridge et al, 2021). In American Samoa, the building code in effect is the Uniform Building Code (UBC) from 1964, as reported by the FEMA Fact Sheet Seismic Building Code Provisions for New Buildings to Create Safer Communities. According to the Mitigation Assessment Team Summary Report and Recommendations, following Super Typhoon Yutu, from FEMA, the Commonwealth of the Northern Mariana Islands, “does not regularly adopt the most recent edition of the I-Codes, which leaves the infrastructure of the CNMI lagging behind national standards. (…) Beginning in 2019, (…) the CNMI government, with the support of FEMA, updated from the 2009 editions to the adoption of the 2018 editions of the IBC and IRC as the official building codes.”
Other countries#
Design regulations in most of the remaining countries in Oceania are practically non-existent. The Regional Diagnostic Study on the Application of Building Codes in the Pacific developed by the “Pacific Region Infrastructure Facility” in 2021, presents a comprehensive review of the national building codes of 13 Pacific island countries, and concludes that: “Many Pacific countries do not have building codes or have unlegislated building codes which cannot be enforced or have outdated building codes. Further, a strong perception remains among construction practitioners in the region that both the old codes and the updated codes and standards are not being administered, managed, or enforced adequately, leading to poor quality and non-resilient infrastructure. Apart from limited funds, problems range from expensive construction materials to the lack of skilled human resources needed for quality control and compliance enforcement.”
As described in the table and image below, extracted from Gwilliams and Gartner (2023), “Pacific building codes have generally evolved, been developed, and influenced through political relations and development cooperation initiatives between Pacific Island governments, foreign governments, and/or multi-lateral development banks. The trade flow of construction materials and education of technical specialists overseas has also had an influence on which codes and standards are implemented in PICs. In general, PICs can be partitioned into three zones of practice for building codes and standards (see Figure below), noting that there can be exceptions to certain building projects where no building legislation or building code exists (but where there is a practice), where donor projects are permitted to use a different standard, or where the availability of construction materials may limit full compliance with the practiced codes and standards.”
“In recent years, various Pacific Island governments have updated their legislation and building codes and/or developed new building codes” (Gwilliams and Gartner (2023)) through different country-specific initiatives, as described in the latest PRIF report.
Australian and New Zealand-Based Codes and Standards |
Cook Islands, Fiji, Kiribati, Nauru, Niue, Samoa, Solomon Islands, Tonga, Tokelau, Tuvalu, and Vanuatu |
France-Based Regulations and Norms |
French Polynesia, New Caledonia, Wallis and Futuna |
US-Based Codes and Standards (North Pacific) |
FSM, Palau, RMI; US Insular areas (Guam, Northern Mariana Islands, American Samoa); US States (Hawaii); Philippines |
|
|---|
Geographical Distribution of the Practice US-Based and Australian/New Zealand-Based, and France-Based Codes/Standards. Source: Gwilliams and Gartner (2023) |
References#
MacRae G, Clifton C, Megget L (2011) “Review of NZ Building Codes of Practice”, Report to the Royal Commission of Inquiry into the Building Failure Caused by the Christchurch Earthquakes
Beattie G, Megget L, Andrews A (2008) “The historic development of earthquake engineering in New Zealand”, The 14th World Conference on Earthquake Engineering, Beijing, China
Fenwick R and MacRae G (2009) “Comparison of the New Zealand standards used for seismic design of concrete structures”, Bulletin of the New Zealand Society for Earthquake Engineering, Vol. 42, No. 3
Davenport P (2004) “Review of seismic provisions of historic New Zealand loading codes”, 2004 NZSEE Conference
Baldridge S, Hirschi M, and Mikhaylov Y (2021) “The Tsubaki Tower”, In Feature