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Earthquake loadings standard NZS 1170.5:2004 has introduced new provisions for the design of building parts and non-structural components. The provisions include factors to define peak floor acceleration up the height of a building, and acceleration response amplifications for components that are quite different from overseas counterparts. In this study, acceleration demands on non-structural components located in ductile frame buildings are analysed under earthquake records from crustal and slab events, for design levels representing ultimate limit state and serviceability limit state.
A floor response spectra approach is used to study the demands on non-structural components. It is noted that the peak floor acceleration demands with respect to that of the ground are not amplified up the height of the building to the extent suggested in NZS provisions. The floor response spectra show peaks near the modal periods of the building indicating higher demands on the components with periods closer to the building period. However, NZS provisions fail to include this effect, since the spectral response amplification is defined independent of building period. Spectral demands exceed the NZS provisions at the fundamental periods of the buildings, more significantly at serviceability conditions, indicating potential failure of non-structural components with periods close to the building periods.
Following the analytical observations from the buildings considered in this study it is clear that the design provisions for non-structural components should be linked to the structural response for specific performance levels rather than the ‘life-safety’ performance level only that is currently adopted in the New Zealand design standard.
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This paper presents a new approach to modelling the spatial distribution of intensities in crustal earthquakes, using a distributed source. The source is represented by one or two rectangular fault rupture planes of chosen dip, discretised into small rectangles each with its own share of the total seismic moment, and modelling chosen distributions of asperities. The Modified Mercalli (MM) intensity of shaking is represented by isoseismals. Comparisons are made with the actual isoseismals (particularly of intensities MM9 and MM10) of selected large historical crustal New Zealand earthquakes and those predicted by the simpler models of Dowrick & Rhoades (2005). Important differences and insights are found regarding near-source spatial distributions of ground shaking of shallow earthquakes with rupture length greater than about 28 km (Mw > 6.8) with any dip, and for Mw > c. 5.5 with dip < 60º. The influence of asperities relative to that of non-asperities is seen as modest near-fault increases in intensity. The new model can be applied to planar or biplanar fault ruptures of any length, width and dip. In the absence of isoseismal data on large earthquakes with normal focal mechanisms the current model is only verified for use on strike-slip and reverse events. A new concept, seismic-source intensity, is introduced and utilized.
The new model can also be applied to earthquakes in other regions of the world with adjustments for local attenuation rates as necessary.
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A new friction moment joint for steel framed structures is described. It has a similar cost to conventional construction and is designed such that there is negligible damage to the frame or slabs. Experimental testing shows that steel, brass or aluminium shims can provide satisfactory friction resistance and that there is almost no damage to the frame during design level displacements. A method for establishing the dependable friction force is developed considering construction tolerances and bolt moment-axial-force-shear interaction. A design methodology for the joint and a design example are provided.
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Unreinforced masonry (URM) buildings remain New Zealand's most earthquake prone class of building. New Zealand URM buildings are classified into typologies, based on their general structural configuration. Seven typologies are presented, and their relative prevalence, age and locations are identified.
There are estimated to be 3,750 URM buildings in existence in New Zealand, with 1,300 (35%) being estimated to be potentially earthquake prone and 2010 (52%) to be potentially earthquake risk, using the NZSEE Initial Evaluation Procedure. Trends in the age of these buildings show that construction activity increased from the early days of European settlement and reached a peak at about 1930, before subsequently declining sharply. The preponderance of the existing URM building stock was constructed prior to 1940, and as such, almost all URM buildings in New Zealand are between 80 and 130 years old (in 2010). Overall the URM building stock has a 2010 market value of approximately $NZ1.5 billion, and constitutes approximately 8% of the total building stock in terms of floor area.
Details are also provided regarding the development of New Zealand building codes and the associated provisions for assessing existing earthquake risk buildings, and provides some background to the history of the URM building stock in New Zealand.
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A ten-member team of engineers was deployed by NZAID and the New Zealand Society for Earthquake Engineering to assist Indonesian local and provincial agencies with rapid structural assessments of earthquake-affected buildings in and around Padang. This was the first time that a team of New Zealand engineers had been operationally deployed outside the Pacific region following a major earthquake.
An accompanying paper describes the earthquake and its impacts, and the general observations of the team. This paper outlines the experiences of a team of 10 New Zealand structural engineers deployed on a volunteer basis for two weeks to undertake the deployment process, the arrangements that the team operated under in Padang, the tasks undertaken and the outputs and outcomes achieved. The lessons for building safety evaluation processes in New Zealand are also presented, along with the resulting enhancements to arrangements.
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The Mw 7.5 Padang earthquake struck at 17:16 local time on 30th September 2009 with an epicentre offshore about 60 km west-northwest of Padang, capital of West Sumatra Province. More than 1,100 people were killed, and over 2,900 injured. The earthquake caused significant damage to public buildings and offices as well as to about 140,000 houses. It affected 250,000 families through the total or partial loss of their homes and livelihoods. More than half the earthquake fatalities occurred when several villages inland from Pariaman were buried by landslides. However, the damage and destruction of building structures was a major cause behind human and property losses. In addition to landslides, the earthquake triggered extensive liquefaction and lateral spreading in the region. A ten-member team from New Zealand visited the area under the auspices of NZAid and New Zealand Society for Earthquake Engineering to undertake building safety evaluations. The team spent most of their time in Padang city and other nearby earthquake-affected areas. This paper presents their observations and explores causes behind the damage and destruction of buildings by the moderate to strong earthquake shaking.
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This paper describes the nature of earthquake damage and rehabilitation of rural land affected by fault rupture and liquefaction following the 4 September 2010 Darfield (Canterbury) Earthquake. Remediation of land damaged by fault rupture and liquefaction was a significant concern for affected farmers and land-owners. A multidisciplinary team of researchers linked to the Rural Recovery Group (responsible for recovery of rural areas following the Canterbury earthquake) used a variety of techniques to assess land damage and evaluate the effectiveness of various rehabilitation techniques.
It was found that land damage caused by strike slip fault rupture could generally be repaired by heavy roller. In areas of severe surface deformation and fracturing, deep cultivation followed by rolling was necessary to close surface fractures and flatten fault micro-topography to restore the land to a useable condition for agricultural use. Liquefaction damage to land consisted of blistered topography (by liquefied sediment injecting between topsoil and sub-soil) and liquefied sediment ejection at the surface. Both surfaces were often unsuitable for continuing agricultural operations. Several passes by a rotary-hoe and power-harrow effectively smoothed blisters and returned paddocks to a suitable state. Land severely affected by sediment ejection required scraping or grading of the sediment to < 50 mm and cultivation of the material into the topsoil. Both treatments resulted in destruction of current pasture or crop. Land less severely affected could be treated by spreading only, which conserved the existing pasture. Future work will track the on-going recovery of remediated and un-remediated land.
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The Mw 7.1 earthquake that struck 40 km west of Christchurch on 4 September 2010 provided a good test of the robustness of the water storage and distribution system of one of our major cities to provide a secure supply of water.
In this paper we present damage data from inspections of 54 reservoirs that were undertaken on behalf of Christchurch City Council and other owners. These included concrete, steel and timber tanks, five of which collapsed and four severely damaged.
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On September 8, a team investigated damage to industrial structures in Christchurch due to the Darfield Earthquake. While there was very little damage to structures regardless of age and framing system, damage to steel storage racks varied from no damage to complete collapse. This paper reports on the observations about the damage to steel racks, reviews pertinent design standards, and makes some preliminary conclusions about the performance of steel storage racks in the Darfield earthquake.
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This paper gives a brief summary of the performance of the electrical infrastructure in the earthquake that struck Christchurch and surrounding regions on 4th September 2010.
