Bulletin of the New Zealand National Society for Earthquake Engineering 

About: Bulletin of the New Zealand National Society for Earthquake Engineering is an academic journal. The journal publishes majorly in the area(s): Earthquake engineering & Seismic analysis. It has an ISSN identifier of 0110-0718. Over the lifetime, 959 publications have been published receiving 13764 citations.

Evaluation of ductility of structures and structural assemblages from laboratory testing

Abstract: Definitions for the required and available ductility used in seismic design are discussed. Methods for estimating the yield deformation and the maximum available deformation are described and suggestions are made for appropriate definitions. Examples are given of different imposed histories of inelastic displacement which have been used in the experimental testing of structures and structural assemblages in which cycles of quasi-static loading are applied. A quasi-static procedure for establishing the available ductility factor of a subassemblage by laboratory testing is recommended.

Performance based seismic design

Abstract: One of the major developments in seismic design over the past 10 years has been increased emphasis on limit states design, now generally termed Performance Based Engineering. Three techniques - the capacity spectrum approach, the N2 method and direct displacement-based design have now matured to the stage where seismic assessment of existing structures, or design of new structures can he carried out to ensure that particular deformation-based criteria are met The paper will outline and compare the three methods, and discuss them in the context of traditional force-based seismic design and earlier design approaches which contained some elements of performance based design. Factors defining different performance states will be discussed, including the need, not yet achieved, to include residual displacement as a key performance limit. Some emphasis will be placed on soil-related problems, and the incorporation of soil/structure interaction into performance-based design. It will be shown that this is relatively straightforward and results in consistent design solutions not readily available with force-based designs using force-reduction factors.

Mechanisms of energy absorption in special devices for use in earthquake resistant structures

Abstract: A structure designed to resist earthquake attack must have a capacity to dissipate kinetic energy induced by the ground motion. In most structures this energy absorption is developed in the vicinity of beam to column connections. Recent research has shown that connections are not reliable when subject to cyclic loading, such as results from earthquake attack. Connections in steel frames deteriorate due to local instabilities in adjacent flanges, and in reinforced concrete frames alternating shear loads produce diagonal tension and bond failures which progressively reduce the strength of the connection. Much work in building research and earthquake engineering in laboratories throughout the world is directed toward increasing the reliability and energy absorption capacity of structural connections. In this paper an alternative approach to this problem is described. This approach is to separate the load carrying function of the structure from the energy absorbing function and to ask if special devices could be incorporated into the structure with the sole purpose of absorbing the kinetic energy generated in the structure by earthquake attack. To determine whether such devices are feasible a study has been undertaken of three essentially different mechanisms of energy absorption. These mechanisms all utilized the plastic deformation of mild steel. They included the rolling of strips, torsion of square and rectangular bars, and the flexure of short thick beams. These mechanisms were selected for intensive study since they were basic to three different types of device each of which was designed for a separate mode of operation in a structural system. The characteristics of these mechanisms which were of primary importance in this study were the load displacement relations, the energy absorption capacity and the fatigue resistance. This information was obtained with a view to the development of devices for specific structural applications. This report describes the tests used to explore the basic mechanisms and the data obtained. It also include s a brief description of tests on scale models of a device which was designed to be located in the piers of a reinforced concrete railway bridge. It has been shown by the tests that the plastic torsion of mild steel is an extremely efficient mechanism for the absorption of energy. It was found that at plastic strains in the range 3% to 12% it was possible to develop energy dissipation of the order of 2000-7500 lb in/in3 per cycle (14-50 x 106 N/M2 per cycle) with lifetimes within the range of 1000 to 100 cycles. It was also shown that the mode of failure in torsion is an extremely favourable one for use in an energy absorbing device in that it took the form of a gradual decay. The other two mechanisms studied were both less efficient and less reliable than torsion and had capacities of 500-2000 lb in/in3 per cycle (3.5 - 14 x 106 N/M2 per cycle) and life times of around 200 to 20 cycles. Nevertheless they lend themselves to more compact devices than does the torsional mechanism and furthermore the devices may be located in regions in a structure where they are readily accessible for replacement after attack.

Seismic performance of reinforced concrete buildings in the 22 February Christchurch (Lyttelton) earthquake

Abstract: Six months after the 4 September 2010 Mw 7.1 Darfield (Canterbury) earthquake, a Mw 6.2 Christchurch (Lyttelton) aftershock struck Christchurch on the 22 February 2011. This earthquake was centred approximately 10km south-east of the Christchurch CBD at a shallow depth of 5km, resulting in intense seismic shaking within the Christchurch central business district (CBD). Unlike the 4 Sept earthquake when limited-to-moderate damage was observed in engineered reinforced concrete (RC) buildings [35], in the 22 February event a high number of RC Buildings in the Christchurch CBD (16.2 % out of 833) were severely damaged. There were 182 fatalities, 135 of which were the unfortunate consequences of the complete collapse of two mid-rise RC buildings. This paper describes immediate observations of damage to RC buildings in the 22 February 2011 Christchurch earthquake. Some preliminary lessons are highlighted and discussed in light of the observed performance of the RC building stock. Damage statistics and typical damage patterns are presented for various configurations and lateral resisting systems. Data was collated predominantly from first-hand post-earthquake reconnaissance observations by the authors, complemented with detailed assessment of the structural drawings of critical buildings and the observed behaviour. Overall, the 22 February 2011 Mw 6.2 Christchurch earthquake was a particularly severe test for both modern seismically-designed and existing non-ductile RC buildings. The sequence of earthquakes since the 4 Sept 2010, particularly the 22 Feb event has confirmed old lessons and brought to life new critical ones, highlighting some urgent action required to remedy structural deficiencies in both existing and “modern” buildings. Given the major social and economic impact of the earthquakes to a country with strong seismic engineering tradition, no doubt some aspects of the seismic design will be improved based on the lessons from Christchurch. The bar needs to and can be raised, starting with a strong endorsement of new damage-resisting, whilst cost-efficient, technologies as well as the strict enforcement, including financial incentives, of active policies for the seismic retrofit of existing buildings at a national scale.

Motions of rigid bodies and criteria for overturning by earthquake excitations

Abstract: This investigation deals with motions of rigid bodies on a rigid floor subjected to sinusoidal and earthquake excitations, and overturning of the bodies. Experiments and simulations of frequency sweep tests were conducted, and it is concluded that the horizontal velocity as well as the acceleration must be taken into account as criteria for overturning. Simulations by earthquake excitations show that the criteria are also applicable to the earthquake excitations. Therefore it is possible to estimate the lower limits of the maximum horizontal acceleration and velocity of the input excitations, from the overturning of bodies.