Earthquakes, design specifications

In addition to withstanding some minimum load or loads (sections titled Load Capacities and Design Specifications ), derricks and masts that satisfy API standards must also satisfy certain requirements regarding materials, allowable stresses, wind, dynamic loading, earthquakes and extremes of temperature. 

Limit state design specifications define the load factors and combinations of loads to be used for conventional loading conditions such as dead, live, wind and earthquake. However, no current limit state design specifications cover blast loading conditions. Blast loads are combined with only those loads which are expected to be present at the time of the explosion. Therefore, blast loads are not combined with earthquake and wind loads,... 

The study of earthquakes is a practice that dates back hundreds of years. Earthquake engineering specifically, however, represents an evolution toward a practical application of the study of seismic activity to the design and construction of large buildings, power plants, and other structures. 

Several sources and projects define the earthquake magnitude in different ways. Day (2002) and Youd et al. (2001) differentiate between the local magnitude (Ml), the surface wave magnitude (Mg) and the moment magnitude (My, ). The latter (M ) is defined as Mg in Eurocode, and best represents the energy associated with the earthquake. However it is concluded that below a value of 7 the magnitude are reasonably close to one another and there is no need to identify which scale is meant in design specifications. 

In accordance to PDVSA-JA-221 specification. Horizontal Earthquake Force (design Base Shear) is given by ... 

Specific sites have to be excluded where in case of earthquake the following occurrences may happen maximum ground acceleration incompatible with proven features of the design unacceptable karstic phenomena surface faulting hquefaction beyond the design capabilities. (It is observed that this criterion excludes particular sites having the possibility of movement of surface faults.)... 

External hazards must not constitute a large part of the residual risk so specific design measures were taken to consider a more appropriate approach on earthquakes, explosion pressure waves and military aeroplane crashes. This requirement had a significant impact on layout requirements. ... 

The criteria applied in the design of the Reactor Coolant System supports are that the specific function of the supported equipment be achieved during all normal, earthquake, safety valve actuation and Branch Line Pipe Break (BLPB) conditions. (BLPB includes feedwater line breaks and all loss-of-coolant-accident conditions resulting from breaks not eliminated by leak-before-break analysis in piping to branch nozzles of the reactor coolant system.) Specifically, the supports are designed to support and restrain the Reactor Coolant System components under the combined Safe Shutdown Earthquake and Branch Line Pipe Break loadings in accordance with the stress and deflection limits of Section III, ASME Code. 

The experimental program consists of two tests on RC full scale T-shaped joints as-built specimen, T C and FRP strengthened specimen, T FRP. The tests were specifically designed in order to validate the FRP strengthening technique recommended in the post-L Aquila earthquake guideline for repair and strengthening of damaged structures. 

Various safety related systems and safety support systems are designed to appropriate safety class specifications depending on the functional importance. In addition, systems are seismically designed for two different intensities of earthquake. The operating basis earthquake (ODE) represents the intensity of earthquake for which the systems are designed to remain functional during and after the event. The safe shutdown earthquake (SSE) considers the maximum earthquake potential of the site and only those systems which are required to ... 

Specifically, these SRP Sections respectively cover review of the site characteristics and earthquake potential, the parameters to be used in seismic design, methods to be used in seismic analysis of the overall plant, and methods to be used in seismic analysis of individual systems or components. 

Other Safety Guides present recommendations relating to the earthquake scenario, but in the framework of the design of specific plant systems Ref. [5] deals with the reactor coolant system. Ref. [6] with the containment system. Ref. [7] with the emergency power system, and Ref. [8] with instrumentation and control systems. 

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