Australian Standard – Commentary. AEES member and past president John Wilson has produced a publication titled “AS Summary This paper provides a short guide and worked examples illustrating the use of AS Structural design actions Part 4. Download AS _Earthquake Actions in Australia_pdf.
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As with all the parts of the series, Part 0 provides the annual probabilities of exceedance or, for buildings covered by the BCA, refers the user to those provided in the BCA. The site hazard is determined from Section 3 of the Standard.
The ductility is achieved by 170.4 the detailing provided in the materials design Standards currently in use. General principles Part 1: Therefore, it is not expected that a structure subject to the design earthquake would be undamaged, but rather that the damage had not progressed to collapse. This will result in more effort in detailing to achieve the higher Mu assumed.
For the lowest values i. A simple method for distributing zs earthquake actions to the levels of the structure is provided. This paper assumes that at least a static analysis has been selected, and therefore, the remaining data required to calculate the base shear has to be determined.
Calculating the base shear For the vast majority of structures low height, normal importance on firm or shallow soils the next step is to estimate if the load is likely to be less than the wind load.
This 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. In cases where a static or dynamic analysis is required, the first mode natural period of vibration of the structure is calculated T1. The Standard assumes that structures are irregular as the vast majority of structures in Australia fail to achieve regularity. The Standard also provides the means for reducing earthquake loads on a structure by achieving set levels of ductility.
Many structures do not require this level of design effort as there are conditions for which no further work is required by the Standard. The equation is based essentially on the height of the structure, but includes an adjustment for material type. Process of designing for earthquake actions Earthquake actions are determined by considering the site hazard and the type and configuration of the structure.
Hazard at the site Once the appropriate annual probability of exceedance has been determined, AS Section 6 sets out the method including the spectral shape factor, the structural ductility and performance factors, the natural period of vibration of the structure, etc.
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.
The use of annual probabilities in the examples is based on recommendations to be proposed for adoption in the BCA at the time of adoption of the new Standard: Generally, for short structures that are not of high importance, simply knowing whether the structure sits on rock or in soils of some depth eg. Walls will usually require a check of the resistance to face loading.
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: General principles provides the link between the limit states actions imposed on the structure and the design of materials for resistance. Permanent, imposed and other actions Part 2: The standard also sets out minimum detailing requirements that aim to provide buildings with a reasonable level of ductility.
A similar approach to reducing loads assuming a higher Mu value could be used where Z is high.
AS 1170.4_Earthquake Actions in Australia_2007.pdf
Therefore, the materials design Standards are much simpler than those required in high hazard areas. Earlier this year CSIR One of the fundamental principles of this approach is the removal of hidden factors through the ss of an umbrella document that defines the loading and resistance levels for design using the design event approach.
The Australian Standard provides for simplified analysis methods based on the low level of hazard. Wind actions Part 3: Summary This paper provides a short guide and worked examples illustrating the use of AS 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. The load is then defined for 1107.4 annual probability of exceedance so that the design event is independent of the technical definition of the loads.
It is calculated by a simple equation given in Section 6 of the Standard.
The key to understanding AS This is required for the highest hazard levels and tallest structures. For Australian conditions, where we have scant knowledge of the earthquake activity, we design for a lateral equivalent static load, unless the structure is particularly vulnerable to dynamic effects.
AS – Australian Earthquake Engineering Society
Spectral shape factor site hazard spectrum The period is then used to determine the spectral shape factor Ch T1 for the building on the site. The loads on the structure are then calculated based on this value. Once the value of Mu is selected the structure must then be detailed to achieve that selected ductility. Earthquake actions in Australia. Materials design Standards then provide detailing to enable the selected structural ductility to be achieved.
The value of Z can be read from a Table or, for locations away from major centres of population, determined from the maps. If they do, the structure will not 11700.4 the ductility required of it and will therefore attract a much higher load than that for which it is designed. The Table 11700.4 shows how for many structures, there are points at which no further work is required. This requires the structure and indeed the whole building to be able to deform with the earthquake and absorb energy without vertical supports giving way.
For dynamic analysis, the effects of a number of periods of vibration may be summed to determine the action effects in the members and, therefore, a number 11704. spectral shape factors may be used in the analysis. Worked examples To illustrate the use of the Standard, following are some examples of the design required for various site conditions. 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 material in which the structure is laterally coupled to the ground provides the site class. Finally, the parts of the structure must be tied together and individually designed to perform.