Effect of a Sunken Mat Foundation on the Horizontal Design Spectrum of a Structure

2021 ◽  
Vol 25 (4) ◽  
pp. 169-177
Keyword(s):  
Design Spectrum ◽  
Mat Foundation

A NEURAL NETWORK-WAVELET MODEL FOR GENERATING ARTIFICIAL ACCELEROGRAMS

2004 ◽  
Vol 02 (03) ◽  
pp. 217-235 ◽  
Author(s):  
GENE F. SIRCA ◽  
HOJJAT ADELI
Keyword(s):  
Neural Network ◽  
Geographic Location ◽  
Training Data ◽  
Wavelet Network ◽  
Design Spectrum ◽  
Earthquake Resistant Design ◽  
Earthquake Resistant ◽  
Structural Configurations ◽  
Earthquake Accelerograms ◽  
Artificial Accelerograms

In earthquake-resistant design of structures, for certain structural configurations and conditions, it is necessary to use accelerograms for dynamic analysis. Accelerograms are also needed to simulate the effects of earthquakes on a building structure in the laboratory. A new method of generating artificial earthquake accelerograms is presented through adroit integration of neural networks and wavelets. A counterpropagation (CPN) neural network model is developed for generating artificial accelerograms from any given design spectrum such as the International Building Code (IBC) design spectrum. Using the IBC design spectrum as network input means an accelerogram may be generated for any geographic location regardless of whether earthquake records exist for that particular location or not. In order to improve the efficiency of the model, the CPN network is modified with the addition of the wavelet transform as a data compression tool to create a new CPN-wavelet network. The proposed CPN-wavelet model is trained using 20 sets of accelerograms and tested with additional five sets of accelerograms available from the U.S. Geological Survey. Given the limited set of training data, the result is quite remarkable.

Time-Domain Nonlinear SSI Analysis of Foundation Sliding Using Frequency-Dependent Foundation Impedance Derived From SASSI

2008 ◽  
Author(s):  
Mansour Tabatabaie ◽  
Thomas Ballard
Keyword(s):  
Frequency Domain ◽  
Linear Systems ◽  
Time Domain ◽  
Soil Structure ◽  
Wave Radiation ◽  
Far Field ◽  
Frequency Dependent ◽  
Nonlinear Springs ◽  
Mat Foundation ◽  
The Time Domain

Dynamic soil-structure interaction (SSI) analysis of nuclear power plants is often performed in frequency domain using programs such as SASSI [1]. This enables the analyst to properly a) address the effects of wave radiation in an unbounded soil media, b) incorporate strain-compatible soil shear modulus and damping properties and c) specify input motion in the free field using the de-convolution method and/or spatially variable ground motions. For structures that exhibit nonlinearities such as potential base sliding and/or uplift, the frequency-domain procedure is not applicable as it is limited to linear systems. For such problems, it is necessary to solve the problem in the time domain using the direct integration method in programs such as ADINA [2]. The authors recently introduced a sub-structuring technique called distributed parameter foundation impedance (DPFI) model that allows the structure to be partitioned from the total SSI system and analyzed in the time domain while the foundation soil is modeled using the frequency-domain procedure [3]. This procedure has been validated for linear systems. In this paper we have expanded the DPFI model to incorporate nonlinearities at the soil/structure interface by introducing nonlinear shear and normal springs arranged in series between the DPFI and structure model. This combination of the linear far-field impedance (DPFI) plus nonlinear near-field soil springs allows the foundation sliding and/or uplift behavior be analyzed in time domain while maintaining the frequency-dependent stiffness and radiation damping nature of the far-field foundation impedance. To check the accuracy of this procedure, a typical NPP foundation mat supported at the surface of a layered soil system and subjected to harmonic forced vibration was first analyzed in the frequency domain using SASSI to calculate the target linear response and derive a linear, far-field DPFI model. The target linear solution was then used to validate two linear time-domain ADINA models: Model 1 consisting of the mat foundation+DPFI derived from the linear SASSI model and Model 2 consisting of the total SSI system (mat foundation plus a soil block). After linear alignment, the nonlinear springs were added to both ADINA models and re-analyzed in time domain. Model 2 provided the target nonlinear solution while Model 1 provided the results using the DPFI+nonlinear springs. By increasing the amplitude of the vibration load, different levels of foundation sliding were simulated. Good agreement between the results of two models in terms of the displacement response of the mat and cyclic force-displacement behavior of the springs validates the accuracy of the procedure presented herein.

Sloshing Response of Floating Roofed Liquid Storage Tanks Subjected to Earthquakes of Different Types

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
F. G. Golzar ◽  
R. Shabani ◽  
S. Tariverdilo ◽  
G. Rezazadeh
Keyword(s):  
Ground Motions ◽  
Far Field ◽  
Storage Tanks ◽  
Natural Period ◽  
Design Spectrum ◽  
Long Period ◽  
Lateral Forces ◽  
Different Types ◽  
Hamiltonian Variational Principle ◽  
Stress Patterns

Using extended Hamiltonian variational principle, the governing equations for sloshing response of floating roofed storage tanks are derived. The response of the floating roofed storage tanks is evaluated for different types of ground motions, including near-source and long-period far-field records. Besides comparing the response of the roofed and unroofed tanks, the effect of different ground motions on the wave elevation, lateral forces, and overturning moments induced on the tank is investigated. It is concluded that the dimensionless sloshing heights for the roofed tanks are solely a function of their first natural period. Also it is shown that while long-period far-field ground motions control the free board height, near-source records give higher values for lateral forces and overturning moments induced on the tank. This means that same design spectrum could not be used to evaluate the free board and lateral forces in the seismic design of storage tanks. Finally, two cases are studied to reveal the stress patterns caused by different earthquakes.

A Critical Look at the Use of Design Spectrum Shape for Seismic Risk Assessment

2012 ◽  
Vol 28 (4) ◽  
pp. 1711-1721
Author(s):  
Emrah Erduran ◽  
Conrad Lindholm
Keyword(s):  
Numerical Simulations ◽  
Response Spectra ◽  
Ground Motion Prediction Equations ◽  
Ground Motion Prediction ◽  
Design Spectrum ◽  
Spectrum Shape ◽  
Actual Spectrum ◽  
Building Typology ◽  
Actual Response ◽  
Damage Estimates

The effects of using design spectrum shape over actual response spectra on earthquake damage estimates has been investigated. A series of numerical simulations were conducted to estimate the expected damage. The simulations were conducted with four different spectral shapes, two different ground-motion prediction equations (GMPEs) and three different soil classes. As a result of the numerical simulations, it was observed that the use of design spectrum shape leads to over- or underestimation of damage estimates relative to those obtained from the actual spectrum computed using GMPE. The damage estimates were observed to be sensitive to the selected design spectrum shape, the GMPE used to compute the spectral values, the soil type, and the fundamental period of the building typology. It was also observed that Eurocode- and IBC-type design spectrum shapes led to significantly different damage estimates compared to one another.

A Study on the Damping Correction Factors for the Korean Standard Design Spectrum

2018 ◽  
Vol 22 (1) ◽  
pp. 1-14
Author(s):  
Tae Min Heo ◽  
◽  
Jung Han Kim ◽  
Jin Ho Lee ◽  
Jae Kwan Kim
Keyword(s):  
Correction Factors ◽  
Design Spectrum ◽  
Standard Design

Methodology for seismic risk assessment for tubular steel wind turbine towers: application to Canadian seismic environment

2011 ◽  
Vol 38 (3) ◽  
pp. 293-304 ◽  
Author(s):  
Elena Nuta ◽  
Constantin Christopoulos ◽  
Jeffrey A. Packer
Keyword(s):  
Seismic Hazard ◽  
Wind Turbine ◽  
Seismic Loading ◽  
Element Analysis ◽  
Design Spectrum ◽  
Wind Turbine Tower ◽  
Damage States ◽  
Wind Turbine Towers ◽  
Hazard Level ◽  
Hazard Levels

The seismic response of tubular steel wind turbine towers is of significant concern as they are increasingly being installed in seismic areas and design codes do not clearly address this aspect of design. The seismic hazard is hence assessed for the Canadian seismic environment using implicit finite element analysis and incremental dynamic analysis of a 1.65 MW wind turbine tower. Its behaviour under seismic excitation is evaluated, damage states are defined, and a framework is developed for determining the probability of damage of the tower at varying seismic hazard levels. Results of the implementation of this framework in two Canadian locations are presented herein, where the risk was found to be low for the seismic hazard level prescribed for buildings. However, the design of wind turbine towers is subject to change, and the design spectrum is highly uncertain. Thus, a methodology is outlined to thoroughly investigate the probability of reaching predetermined damage states under any seismic loading conditions for future considerations.

Vector-Valued Uniform Hazard Spectra

2012 ◽  
Vol 28 (4) ◽  
pp. 1549-1568 ◽  
Author(s):  
Shun-Hao Ni ◽  
De-Yi Zhang ◽  
Wei-Chau Xie ◽  
Mahesh D. Pandey
Keyword(s):  
Seismic Hazard ◽  
Seismic Design ◽  
Hazard Analysis ◽  
Occurrence Rate ◽  
Simultaneous Occurrence ◽  
Uniform Hazard Spectra ◽  
Design Spectrum ◽  
Performance Based Seismic Design ◽  
Design Earthquake ◽  
Vector Valued

Uniform hazard spectra (UHS) have been used as design earthquakes in several design codes. However, as the results from scalar probabilistic seismic hazard analysis (PSHA), UHS do not provide knowledge about the simultaneous occurrence of spectral accelerations at multiple vibration periods. The concept of a single “design earthquake” is then lost on a UHS. In this study, a vector-valued PSHA combined with scalar PSHA is applied to establish an alternative design spectrum, named vector-valued UHS (VUHS). Vector-valued seismic hazard deaggregation (SHD) is also performed to determine the design earthquake in terms of magnitude, distance, and occurrence rate for the VUHS. The proposed VUHS preserves the essence of the UHS and can also be interpreted as a single design earthquake. To simplify the procedure for generating the VUHS, so that they can be easily incorporated into performance-based seismic design, an approximate method is also developed.

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