Earthquake Loads & Earthquake Resistant Design of Buildings

Topics: Earthquake engineering, Structural engineering, Shear wall Pages: 24 (8227 words) Published: April 28, 2005
Earthquake Loads & Earthquake Resistant Design of Buildings

3.Earthquake Design - A Conceptual Review2
4.Earthquake Resisting Performance Expectations3
5.Key Material Parameters for Effective Earthquake Resistant Design3 6.Earthquake Design Level Ground Motion4
6.1.Elastic Response Spectra4
6.2.Relative Seismicity5
6.3.Soil amplification6
7.Derivation of Ductile Design Response Spectra7
8.Analysis and Earthquake Resistant Design Principles8
8.1.The Basic Principles of Earthquake Resistant Design8
8.2.Controls of the Analysis Procedure8
8.3.The ‘Conventional' Earthquake Design Procedure11
9.The Capacity Design Philosophy for Earthquake Resistance11 9.1.General Approach11
9.2.The Implications of Capacity Design12
10.Earthquake Resistant Structural Systems12
10.1.Moment Resisting Frames:12
10.2.Shear Walls13
10.3.Braced Frames13
11.The Importance & Implications of Structural Regularity13 11.1.General13
11.2.Vertical Regularity14
11.3.Horizontal Regularity.14
11.4.Floor Diaphragms14
12.Methods of Analysis15
12.1.Integrated Time History Analysis15
12.2.Multi-modal Analysis15
12.3.Equivalent Static Analysis15
13.Trends and Future Directions16
The primary objective of earthquake resistant design is to prevent building collapse during earthquakes thus minimising the risk of death or injury to people in or around those buildings. Because damaging earthquakes are rare, economics dictate that damage to buildings is expected and acceptable provided collapse is avoided. Earthquake forces are generated by the inertia of buildings as they dynamically respond to ground motion. The dynamic nature of the response makes earthquake loadings markedly different from other building loads. Designer temptation to consider earthquakes as ‘a very strong wind' is a trap that must be avoided since the dynamic characteristics of the building are fundamental to the structural response and thus the earthquake induced actions are able to be mitigated by design. The concept of dynamic considerations of buildings is one which sometimes generates unease and uncertainty within the designer. Although this is understandable, and a common characteristic of any new challenge, it is usually misplaced. Effective earthquake design methodologies can be, and usually are, easily simplified without detracting from the effectiveness of the design. Indeed the high level of uncertainty relating to the ground motion generated by earthquakes seldom justifies the often used complex analysis techniques nor the high level of design sophistication often employed. A good earthquake engineering design is one where the designer takes control of the building by dictating how the building is to respond. This can be achieved by selection of the preferred response mode, selecting zones where inelastic deformations are acceptable and suppressing the development of undesirable response modes which could lead to building collapse. 2.Earthquake Design - A Conceptual Review

Modern earthquake design has its genesis in the 1920's and 1930's. At that time earthquake design typically involved the application of 10% of the building weight as a lateral force on the structure, applied uniformly up the height of the building. Indeed it was not until the 1960's that strong ground motion accelerographs became more generally available. These instruments record the ground motion generated by earthquakes. When used in conjunction with strong motion recording devices which were able to be installed at different levels within buildings themselves, it became possible to measure and understand the dynamic response of buildings when they were subjected to real earthquake induced ground motion. By using actual earthquake motion records as input to the, then, recently developed inelastic integrated time history analysis packages, it became apparent...

References: 1 New Zealand Government Print, 1992. Regulations to the Building Act, Wellington.
2 Australian Building Codes Board. 1996. Building Code of Australia. CCH Australia for the ABCB. Canberra.
3 Standards New Zealand. 1992. Loading Standard. NZS 4203. Wellington.
4 Standards Australia. 1988. Dead and live loads and load combinations. AS 1170.1. Homebush, Sydney.
5 Standards Australia
6 Standards Australia. 1992. Snow loads. AS 1170.3. Homebush, Sydney.
7 Standards Australia
11 Paulay T. and Preistley M.J.N. 1992. Seismic Design of Reinforced Concrete and Masonry Buildings. John Wiley & Son Inc. New York.
12 Canadian Concrete Association. 1994. Design of Concrete Structures for Buildings. CAN-A23.3-M84. Rexdale, Ontario.
13 Paulay T. 1997. A Review of Code Provisions for Torsional Seismic Effects in Buildings. New Zealand National Society for Earthquake Engineering Bulletin. Wellington Vol 30 (3) pp 252-264.
14 Priestley, M.J.N
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