Earthquake engineering
 | It has been suggested that Seismic performance, Vibration control, Earthquake Protector, Earthquake Performance Evaluation Tool, Earthquake simulation and Earthquake construction be merged into this article. (Discuss) Proposed since June 2008. |
Earthquake engineering is the analysis of structures to understand their behaviour in earthquakes, and the design and construction of structures to withstand earthquakes.
Seismic performance
Earthquake or seismic performance is an execution of a building's or structure's ability to sustain their due functions, such as its safety and serviceability, at and after a particular earthquake exposure. A structure is, normally, considered safe if it does not endanger the lives and wellbeing of those in or around it by partially or completely collapsing. A structure is considered serviceable if it is able to fulfil the operational functions for which it was designed.
Basic concepts of the earthquake engineering, implemented in the major building codes, assume that a building should survive The Big One (the most powerful anticipated earthquake) though with partial destruction. Drawing an analogy with a human body, it will have dislocated joints, fractured ribs, traumatized spine and knocked out teeth but be alive and, therefore, quite O.K. according to the presciptive building codes [1]. This situation is a major barrier to implementation of any structural innovations in the earthquake engineering technologies employing the seismic vibration control and, particularly, the most effective brands of base isolation.
However, alternative seismic performance-based design approaches already exist. Some of them, for assessment or comparison of the anticipated seismic performance, use the Story Performance Rating R as a major criterion [2] while the Seismic Performance Ratio (SPR) is used for a rather accurate prediction of seismic performance of a building up to the point of its state of “severe damage” [3].
Now, there is a publicly accessible computerized procedure for prediction of the quantified level of seismic performance associated with direct damage to an individual building subject to a specified ground shaking. The name of software is Earthquake Performance Evaluation Tool or EPET.
Analysis
Seismic analysis is the calculation or modelling of the response of a building (or nonbuilding) structure to earthquakes, in order to establish a structure's seismic performance.
The analysis of a structure's response can be done analytically, using direct calcuations or finite element analysis, or using physical tests, such as shaking table testing. (see Destructive testing).
The analysis of a structure's seismic performance can test and inform the design of a new structure, or allow understanding of how an existing structure will perform when struck by an earthquake. With such understanding of existing structures it can be decided whether seismic retrofitting is required.
Design
Structures are designed to withstand the largest earthquake that is likely to occur at the location at which they are built. The main criteria in earthquake design is limiting loss of life, by preventing collapse of the building. A design is carried out by understanding the possible failure modes of a structure and providing the structure with sufficient strength and stiffness to ensure they cannot occur.
Failure modes
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Failure modes include:
- Soft storey collapse (a single storey with insufficient shear strength, often the ground floor, collapses)
- Reinforced concrete column burst (insufficient shear reinforcement allows main reinforcement to buckly outwards)
- Sliding off foundations (relatively rigid structures may slide off their foundations)
- Shear failure of floor structure (beams with insufficient lateral restraint may fall over and fail)
- Failure of retaining structures due to ground movement
- Shear failure of column heads (the lateral movement of a floor shears the floor from the supporting column)
- Soil failure due to slope failure or soil liquefaction
Design solutions
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See Also
Notes
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