Detailing rules to achieve these levels of ductility can be highly complex. For the lowest values i. Process of designing for earthquake actions Earthquake actions are determined by considering the site hazard and the type and configuration of the structure. Also, as a result of the lower earthquake loads expected, the detailing required is minimal compared to that for such countries as New Zealand. Once the horizontal design action is calculated from the above information and the seismic weight of the structure, analysis can be carried out. Period of vibration of the structure The construction material, type of structure, and the period of the first mode of vibration all have an influence on the forces experienced by the structure. The Table below shows how for many structures, there are points at which no further work is required.
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Influence of site sub-soil conditions The site sub-soil conditions are grouped into 5 categories Class Ae, Be, Ce, De or Ee ranging from hard rock to very soft materials.
General principles provides as 1170.4 link between the limit states actions imposed on the structure and the design of materials for resistance. Once the horizontal design action is aa from the above information and the seismic weight of the structure, analysis can be carried out. Inter-storey drifts should be checked to ensure that parts such as stiff walls do not interfere with the seismic force resisting system.
If they do, the structure will not exhibit the ductility required of it and will therefore attract a much higher load than that for which it is designed. As 1170.4 approach arises from the small knowledge we have of earthquake risk in Australia coupled with the very low levels of earthquake risk we do currently expect.
Australian Standards AS Seismic Performance of Engineering Systems
Mu the Greek letter represents the structural ductility while Sp, the structural performance factor, is an adjustment made to calibrate the known performance of structure types to the calculated ductility. Wind actions Part 3: The base as 1170.4 may be understood to be the percentage of the weight of the building to be applied laterally eg. The Australian Standard provides for simplified analysis methods based on the low level of hazard.
The Table below shows how for many structures, there are points at which no further work is required. Earthquake actions in Australia AS The site hazard is determined from Section 3 of the As 1170.4.
The load is then defined for any annual probability of exceedance so that the design event is independent of the technical definition of the loads.
ax Many structures do not require this level of design effort as there are conditions for which no further work is required by as 1170.4 Standard. The loads on the structure are then calculated based on this value.
The use of as 1170.4 probabilities in the examples is based on recommendations to be proposed for adoption in the BCA at as 1170.4 time of adoption of the new Standard: Quick paths to an exit If you are designing one of the following structures, you can exit quickly to a simplified solution or even out of the Earthquake Standard altogether: For the lowest values i. The material in which the structure is laterally coupled to the ground provides the site class.
The soil type is determined by a geotechnical investigation for taller longer period structures. The standard also sets out minimum detailing requirements that aim to provide buildings with a reasonable level of ductility. The Standard also provides the means for reducing earthquake loads on a structure by achieving set levels of ductility. Also, as a result of the lower earthquake loads expected, the as 1170.4 required is minimal compared to that for such countries as New Zealand.
One of the fundamental principles of this approach is the removal of hidden factors through the provision of an umbrella document that defines the loading and resistance levels for design using the design event approach.
The key to understanding AS General principles Part 1: Finally, the parts of the structure must be tied together and individually designed to perform. In order to achieve the ductility assumed in design of the structure, it is essential that stiff elements should not impose themselves on the behavior of the seismic force resisting system. Hazard at the site Once the appropriate annual probability of exceedance has been determined, AS The examples assume that at least a static analysis has as 1170.4 selected, and therefore, sets out the data required to calculate the base shear.
Earlier this year CSIR The aim is to avoid collapse.
AS 1170.4_Earthquake Actions in Australia_2007.pdf
The value of Z can be read from a Table or, for locations away from major centres of population, determined from the maps. Earthquake as 1170.4 in Australia. This value is then multiplied by the probability factor kp to determine the site hazard value kpZ for the appropriate annual probability of exceedance. Therefore, the materials design Standards are much simpler than those required in high hazard areas.