2007 NZSEE
Conference
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2007 NZSEE Conference |
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Contents |
Keynote Address 1 Defining Acceptable Performance Criteria Planning for Expected Performance / Improving Existing Performance I Improving Existing Performance II Keynote Address 2 Developments Within Design I Developments Within Design II Developments Within Design III / Understanding the Inputs Assessing Existing Performance Poster Papers Liquefaction Hazards for Seismic Risk AnalysisSonia Giovinazzi and Misko Cubrinovski Seismic risk analysis is a helpful tool that supports decision making for planning and prioritizing seismic risk management strategies. This paper focuses on the importance of an appropriate geotechnical hazard representation within a seismic risk analysis process, focusing on the earthquake-induced geotechnical hazards due to liquefaction. After an overview of alternative methods for the representation of the liquefaction hazards available in the literature, more refined approaches are proposed for implementation in the seismic risk analysis. As a matter of fact, conventional seismic risk and damage scenario analyses use generalized parameters for estimating the consequences of liquefaction that provide a qualitative description of the effects of liquefaction instead of quantitative engineering parameters for the ground deformation. This paper suggests a simple remedy to this practice through the use of some existing methods for estimating the ground distortion caused by liquefaction. Paper P06: [Read] Earthquake Design and Construction of the Wellington Inner City Bypass, WellingtonBrabha Brabhaharan The Wellington Inner City Bypass is a key lifeline arterial route providing access on the route to the regional hospital and airport. The project includes a 450 m long trench section south of the Terrace Tunnel. The up to 8 m high walls supporting this trench were designed to maintain serviceability after large earthquakes. Two wall systems, a propped concrete trough structure and soil nailed walls, were adopted, with the choice being highly influenced by complex ground and groundwater conditions and high seismicity – design peak ground accelerations of 0.6g to 0.7g, and magnitude 7.5 earthquakes on the Wellington Fault. Efficiency in the trough structure design was achieved by transferring the large earthquake earth pressure loads from one side of the trench through the struts and the floor slab to the opposite side, where it is resisted through passive soil resistance, and allowing limited displacement of the whole structure in large earthquakes. A performance based design approach, allowing limited displacements in large earthquakes was also adopted for the soil nailed walls. Test soil nails during construction helped refine post-grouting techniques to provide greater soil nail capacities and lower deformations, to meet earthquake performance expectations. These innovative concepts led to substantial savings in trench construction costs.
Paper P08: [Read] Exercise Capital Quake ’06: Outcomes from New Zealand’s National Disaster Preparedness ExerciseDavid Brunsdon and Mike O'Leary In November 2006, a national disaster preparedness earthquake exercise was held over two days. Based on the Magnitude 7.6 Wellington Fault rupture earthquake scenario, Exercise Capital Quake ’06 involved more than 1,000 participants from more than 50 organisations. This paper summarises the exercise planning processes and delivery arrangements, and the key outcomes and future actions arising. One of the outcomes of particular interest to earthquake engineering researchers and practitioners alike is the acknowledgement of the need to update and maintain the modelling of this event. The associated issue is the presentation of the impacts of earthquakes of this scale in a form that enables non-earthquake engineers to appreciate the implications. Paper P09: [Read] Improving Seismic Performance : Add Stiffness or Damping?Trevor Kelly Structural engineers typically improve the seismic performance of deficient structures by adding strengthening elements to the structural system, which also add stiffness to the structure. However, as performance based design becomes more common practice, the focus is on the total performance of not only the structural system but the building components and contents. A stiffer and stronger building will generally be subjected to lower drifts but higher floor accelerations than a weaker and/or more flexible building. Reduced drift related damage may be accompanied by increased damage to components and contents which are sensitive to accelerations. This paper examines two common forms of hardware used to strengthen existing buildings, buckling restrained braces (BRB) and viscous damping devices (VDD). Both types of device augment the existing structural system, rather than replace it. A series of nonlinear analyses is used to quantify the performance of two prototype frame buildings strengthened with each type of device. It is shown that equivalent structural performance, in terms of overall deformations, can be achieved with both types of device, and generally for lower cost by BRBs if only moderate levels of drift reduction are required. However, when the total building performance is examined the VDDs provide additional benefits in the form of reduced floor accelerations. The benefits of this may be sufficient to warrant the higher cost solution.
Paper P11: [Read] Semi-active Resetable Actuators Incorporating a High Pressure SourceKerry Mulligan, Geoffrey Chase, John Mander and R.B. Elliot Semi-active resetable actuators, with air as the working fluid, have been shown to be capable in improving the performance of structures under earthquake excitation. In addition, a wide variety of control laws have been implemented allowing the response of the devices to be tailored to the application, however the limiting factor for some applications is the maximum forces produced by the devices. This investigation examines the possibility of incorporating a high pressure air source to compliment and enhance the capabilities of the resetable devices. Initial modelling shows a 100% increase in the peak force produced when the initial pressure is doubled. In addition, the high pressure source allows greater manipulation of the device hysteretic response. Paper P49: [Read] Seismic Response of Hybrid-LVL Coupled Walls under Quasi-static and Pseudo-dynamic TestingTobias Snith, F Ludwig, Stefano Pampanin, M Fragiacomo, Andy Buchanan, Bruce Deam and Alessandro Palermo Innovative seismic resisting connections for laminated veneer lumber (LVL) timber multi-storey buildings have been recently presented by the authors, based on the combination of unbonded post-tensioning techniques and additional sources of dissipation. As part of an extensive research campaign underway at the University of Canterbury, alternatives solutions for beam-column subassemblies, wall-to-foundation and column-to-foundation connections have been developed, implemented and successfully tested under either quasi-static cyclic and pseudo-dynamic testing regimes. In this paper, the implementation and experimental validation, under both quasi-static cyclic and pseudo-dynamic testing protocols, of post-tensioned/dissipating coupled solid wall systems with different coupling configurations and dissipation devices (i.e. mild steel dissipaters and multi-nailed plywood sheets) is presented. The research investigations confirmed the high seismic performance of these connections and systems, as well as the low-costs and the easy practicality of their implementation on site. Paper P60: [Read] Keynote Address 1 Defining Acceptable Performance Criteria Planning for Expected Performance / Improving Existing Performance I Improving Existing Performance II Keynote Address 2 Developments Within Design I Developments Within Design II Developments Within Design III / Understanding the Inputs Assessing Existing Performance Poster Papers |