It is well-known that the application of the Square-Root-of-Sum-of-Squares ( SRSS) method in seismic analysis for combining modal maxima can cause. A replacement for the SRSS method in seismic analysis [Edward L Wilson] on *FREE* shipping on qualifying offers. A Replacement for the SRSS Method in Seismic Analysis. Front Cover. Edward L. Wilson. Wiley, – Structural analysis (Engineering).
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Periodic responses are dominant in the region of amplified spectral displacement, amplified spectral velocity and amplified spectral acceleration. In seismic response analysis two types of combinations are to be considered: SRSS3 method would have z rather anaoysis error if the natural periods of the structure are close to each other, namely modal correlation coefficients of structure are large.
In general, this alternative method is slightly conservative for most cases and is quite adequate since its degree of ih is relatively small. Figure 1 shows the typical conceptual shape of a response spectrum in terms of velocity as a function of frequency ref. Recently, there is a growing interest in seismic qualification of ridges, buildings and mechanical equipment worldwide due to increase of accidents caused by earthquake.
The percentage rule is also proposed in paragraph 4.
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This paper offers also page 49 a short discussion of the directional combination procedure: The percentage rule was put forward by Newmark and Rosenblueth first. Also, the structural design optimizations were conducted for the four different initial design variable sets to confirm robustness of the optimization algorithm used. This subject is dealt with in several standards or regulatory guides among which the following are examined herein below: The rigid responses and rigid components of responses are combined algebraically.
This statement is supported referring to a detailed discussion on this issue developed by Menun and Der Kiureghian in and Figure 2 shows the typical response spectrum in terms of acceleration as a function of frequency ref. The combination rule to be used for individual modal responses depends upon whether the responses are periodic, rigid or both see R. The percentage method teh never explicitly cited, but the theoretical bases for it are provided in Chapter 4, where the superposition of the i-modes is provided as linear combination with coefficients C i that have different values for mefhod modes but can be approximated by the value 0.
There is no specific provisions regarding combination of spatial components, except that in letter f of Section 2. Then, the seismic analysis for each direction can be performed separately and then combined replaecment the square root of the sum of the squares SRSS. Equipment Inspection Method and Weibull Analysis. This condition is equivalent to the one adopted by R.
The effects due to the different directions of the seismic action shall be combined with the percentage rule see para. When modes are to be considered closely spaced is matter of discussion and any standards provides a slightly different rule.
For what regard the mode combination, paragraph As an alternative the SRSS rule can be used. The dotted lines refer to the case of multiple narrow-banded response spectrum with two or more peaks of acceleration. For response spectrum RS analysis, the R. Severe earthquake can bring serious problems in the wind turbines and eventually lead to an interruption to their electric power supply. To overcome and prevent these undesirable problems, structural design optimization of a small vertical axis wind turbine has performed, in this study, for seismic qualification and lightweight by using a Genetic Algorithm GA subject to some design constraints such as the maximum stress limit, maximum deformation limit, and seismic acceleration gain limit.
No other rules are specified for non-building structures dealt with in Chapter The effects of each modes for a given direction of the seismic action shall be combined with the CQC rule see para. In general, if the frequencies of the modes are sufficiently separated, the SRSS method may be applied.
Simply shifting the starting time of a given accelerogram inn not constitute the establishment of a different accelerogram. Foor Omnia Vicit Improbus. He provides the following recommendations page Sviluppato con Drupal da Gmg Net Srl.
The rigid response corresponds to the steady-state phase in theory of vibrations. Sseismic a result, all the optimization results for the 4 different initial designs showed good agreement with each other properly.
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The directional effects of an earthquake are combined with the following rules: The maximum value is 1. According to ECparagraph 4. The equations are written as follows: Scientific Research An Academic Publisher. The periodic response corresponds to the transient phase in theory of vibrations. According to this book, this approach introduces a maximum error of 4. The wnalysis rule is therefore adopted. If uncoupled response of the structure is expected, then only one time history is required.
Regarding the number of modes, in para.