Earthquake load

Earthquake effects on these concrete structures shall be determined by using the appropriate structural response prepared by the Civil Engineering Branch of the TVA or any other organisations. 

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Part AD This part contains requirements for the design of vessels. The rules of Division 2 are based on the maximum-shear theoiy of failure for stress failure and yielding. Higher stresses are permitted when wind or earthquake loads are considered. Any rules for determining the need for fatigue analysis are given here. 

There will be no significant loading from piping and external equipment. Earthquake loading need not be considered. 

The structural frame of the tower also shall be designed to withstand the wind pressure in any horizontal direction or earthquake loading, as specified in the section of the requisition entitled Requirements— Size, Capacity and Operation. 

Certain simplifications that allow the dynamic response to be reconciled with equivalent static loadings are examined. In earthquake loading the dominant effects are found to occur in the lowest mode for which no cross sectional distortion takes place. In wind loading the dynamic response is spread over several modes. The maximum dynamic tensile stresses at the windward base of the tower can be estimated using simple gust effect factors. 20 refs, cited. 

Seismic (earthquake) loads on tall vessels (Section 13.8.3) ... 

Rigid structures have short periods of vibration and are more susceptible to seismic destruction than flexible structures. For this reason, it is recommended that a seismic coefficient related to the vibration period of the tower be used in designing tall towers for earthquake loads. A tall, flexible structure capable of absorbing seismic shifts should not be penalized with the same seismic coefficient used for rigid structures such as masonry buildings that are more susceptible to failure from earthquakes. 

Designs for structures subjected to earthquake loads are empirical and are based on the analyses of structures that withstood earthquakes in the past. Earthquakes have periods of vibration, but the periods are complex. They are not simple harmonic vibrations in tall steel towers. Data on some past serious earthquakes are given in Table 4-5. The horizontal acceleration, a, produced by the shift of the earth crust divided by gravitational constant, gy gives the seismic coefficient, C or... 

Values in table due to force F are based on Stress Analysis of the Balcony Girder of Elevated Water Tanks Under Earthquake Loads by W.E. Black Chicago Bridge... 

Over the past decade, there has been an increasing awareness of the significance of the behavior of soils under cyclic stress induced by wave or earthquake loading, on the design and performance of offshore structures seafloor foundation systems, and seafloor slopes. 

Determination of these soil properties are well established with recent advances in the formulation of nonlinear hysteretic constitutive relations for soils and the characterization of stiffness degradation of saturated sands and clays with cycles of loading. The increasing interest in seafloor slope stability problems imder wave and earthquake loadings has also emphasized the need for data from cyclic tests simulating stress conditions on slopes. The application of cyclic test techniques in relation to the latter developments are discussed with reference to both test results and associated analytical approaches. 

Typical types of cyclic loadings in the marine environment, (a) Jackup platform leg (1-way) (b) earthquake loading (2-way) (c) ocean wave loading (2-way). (From Chaney, R.C., and Fang, H.Y., Liquefaction in the coastal environment An analysis of case histories, Marine Geotechnology, Vol. 10,343-370,1991. Reprinted with permission. Copyright ASTM.)... 

The storm waves have periods considerably longer than earthquake loadings. 

Two categories of numerical models have been developed to assess the initial stability and movement of sediments. The majority of these models were initially developed for terrestrial applications (i.e., design of earth dams) but have the potential to be employed to advantage in the marine environment. These models are (1) limit equilibrium and (2) finite elemen and are discussed in Sections 11.4.2 and 11.4.3. Solutions involving earthquake loading are included for completeness. 

Undrained condition This may be relevant to cases of wave loading, earthquake loading, rapid deposition, or erosion. 

The excess pore water pressure can be the result of underconsolidation (i.e., rapid sedimentation rates) or earthquake loading as examples. The ultimate shear stress under these circumstances can be the following ... 

Firm and Lee (1979) presented results from a more general effective stress method based on Sarma s (1973) model, which in addition to wave loading also included earthquake loading and excess pore pressures. An example of such an analysis is shown in Figure 11.16. 

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