Modal Combination in Response Spectrum Analysis of Piping Systems

1986 ◽  
Vol 108 (1) ◽  
pp. 73-77 ◽  
Author(s):  
A. K. Gupta ◽  
J.-W. Jaw
Keyword(s):  
Spectrum Analysis ◽  
Response Spectrum ◽  
Direct Integration ◽  
Response Spectrum Analysis ◽  
Combination Rules ◽  
Combination Methods ◽  
Modal Response ◽  
Piping Systems ◽  
Higher Modes Effect ◽  
Integration Analysis

Modal combination methods in the response spectrum analysis of piping systems have been investiaged. Two particular effects are identified, viz, (i) the residual rigid response, also known as the higher modes effect (HME); (ii) the correlation between the modal response and the rigid response. Gupta’s method accounts for both these effects. It is shown that Gupta’s method gives results which are much closer to the direct integration analysis results than are the results obtained from any other modal combination rules which ignore either one or both of the foregoing effects.

A Comparative Study of Combination Methods Used in Response Spectrum Analysis of Nuclear Piping Systems

1984 ◽  
Vol 106 (1) ◽  
pp. 25-31 ◽  
Author(s):  
S. Gupta ◽  
D. P. Jhaveri ◽  
O. Kustu ◽  
J. A. Blume
Keyword(s):  
Spectrum Analysis ◽  
Response Spectrum ◽  
Nuclear Regulatory Commission ◽  
Dynamic Responses ◽  
Combination Method ◽  
Response Spectrum Analysis ◽  
Combination Methods ◽  
Piping Systems ◽  
Regulatory Commission ◽  
The U.S

The different methods of combining responses for individual modes and directions for response spectrum analysis of nuclear piping systems are evaluated. For the purpose of the study, dynamic responses of 20 typical piping systems using nine different combination methods are systematically compared. The study established the relative conservatism in design achieved by each method and the probability that a particular combination method will produce a more conservative estimate of seismic response than obtained using one of the methods accepted by the U.S. Nuclear Regulatory Commission.

Torsional Displacements in Base-Isolated Buildings

2000 ◽  
Vol 16 (2) ◽  
pp. 443-454 ◽  
Author(s):  
R. S. Jangid ◽  
J. M. Kelly
Keyword(s):  
Spectrum Analysis ◽  
Analytical Study ◽  
Response Spectrum ◽  
Equations Of Motion ◽  
Governing Equations ◽  
Response Spectrum Analysis ◽  
Combination Rules ◽  
Torsional Response ◽  
Torsional Coupling ◽  
Torsional Frequency

An analytical study of the effects of torsional coupling on the seismic response of a base-isolated building is presented. The isolated structure is modeled as a rigid deck supported on axially inextensible bearings. The governing equations of motion for the coupled lateral-torsional response of the system are derived. The eccentricity in the system is that specified by the Uniform Building Code (UBC). The displacement response of the isolated system with different combinations of building configuration, isolation damping, and the ratio of uncoupled torsional to lateral frequency of the system is investigated. The response of the isolated structure under a variety of near-fault and other earthquake ground motions is compared to that obtained by use of response spectrum analysis. In the response spectrum analysis the accuracy of several modal combination rules is evaluated. It is shown that torsional coupling can influence the response of the isolated structure, but if the layout of the isolation bearings is such that the torsional frequency is larger than the lateral frequency, the effect is reduced and the usual modal combination rules work well. It is also shown that in this case, the UBC static formula for the additional isolator displacements due to torsion is conservative.

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