Help Page for the Java-Powered Simulation for Experimental Structural Dynamics


Table of Contents

 

Page created by Sung-Han Sim
Last updated on 6/27/2006


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Introduction

Welcome to the help page of the Java-Powered Simulation for Experimental Structural Dynamics.

Many principles in structural dynamics are best illustrated in the laboratory, collecting and processing data to extract the basic features of the structure. The purpose of this tool is to simulate the laboratory environment providing a Virtual Laboratory (VL). This VL utilizes a multi-story shear building model as the test bed and provides essential features of the experiment such as sensors, noise, anti-aliasing filter, finite time windows, etc. With the user-defined parameters for the virtual experiment, the VL calculates the structures responses through the linear/nonlinear dynamics analysis. Results from these analyses give users unique insight into the dynamic behavior of the structure from the response measurement point of view.

The VL supports two types of parameters which are allowed for users to set up. The parameters for structure includes story number, mass, stiffness, damping, yield displacement, and post-yield stiffness. These parameters are located at the top of the control panel as shown in Figure 1. The other parameters for the experiment are found in the middle of the control panel. A total 8 kinds of excitation is provided and noise level of the excitation is adjustable from 0% to 5%. The sensor location and type can be determined by the user. There are 6 types of sensors available which are displacement, velocity, acceleration, spring force, shear force and damping force sensors. The anti-aliasing (AA) filter is also available and the cutoff frequency of the AA filter is changeable by the user. There are other parameters related to the FFT calculation such as the number off FFT and average, overlap and windowing.

The VL provides useful buttons which can be found at the bottom of the control panel. The VL displays an animation based on the building response, which gives users a better understanding of dynamic analysis. In addition, the user can save all data by clicking the Save Data button.

To portray the structure, four models are used, which include (a) linear stiffness and linear viscous damping; (b) linear stiffness and nonlinear power-law damping; (c) hysteretic stiffness using the Bouc-Wen model and linear viscous damping; and (d) hysteretic bilinear stiffness and linear viscous damping.

This document offers a description of how to operate and use the Java-Powered Simulation for Experimental Structural Dynamics as well some technical background. A number of "homework" problems (or exercises) are also suggested and references are provided.

Response plot panel
Animation panel
Control panel
Response plot panel
 

 

Figure 1. Java-Powered Simulation Applet


How to Use the Virtual Laboratory

The user interface of the VL is shown in Figure 1. The program interface consists of (1) control panel, (2) animation panel, and (3) four response plot panels. Note that users can toggle between two response plot panels and the animation panel by clicking “Hide Virtual Building” or “Show Virtual Building” button of the control panel.

Control Panel

Figure 2. Control Panel
Located on the right of the simulator, this panel is used to specify various parameters for the structure, ground excitations and data processing. This panel also contains buttons to conduct computation and animation.

Structural Parameters

Structure Models

Excitation and Sensors

Data Processing

Action Buttons


Animation Panel

Located in the middle of the simulator, the animation panel shows a simulation of the structural system undergoing the excitation. One of the 4 models, linear model, nonlinear damping model, Bouc-Wen model, and bilinear model, may be selected by users to define the property of the building, thus its dynamic behavior. Users are also able to choose to animate absolute or relative motion of the structure:

Response Plot Panel

There are four response plot panels, two of which are located on the right of the simulator and the other two are hidden under the animation panel. These two hidden panels and the animation panel are interchangeable by clicking Hide Virtual Building” or “Show Virtual Building” button of the control panel.

(a) Model selection

(b) Multiple models

(c) A selected model

Figure 3. Response Selection Window

Measured responses and various functions related to spectral analysis are shown on these panels. Users can choose what they want to see by using the drop-down menu under each response plot panel, which will open “response selection window”. Functions which users can choose on the drop-down menu are as follows.

  • y(t): time history of the ground excitation and the corresponding measured responses

  • x-y: response vs. response plot

  • FFT: fast Fourier transform of the ground excitation or the measured responses

  • PSD: power spectrum density function of the ground excitation or the measured responses

  • CSD: cross spectral density function between the ground excitation and one measured response or between two measured responses

  • Xfer: transfer function between the ground excitation and one of the measured responses or between any two of the measured responses

  • ACorr: auto correlation function of the ground excitation or the measured responses

  • Ccorr: cross correlation function between the ground excitation and one measured response or between two measured responses

  • Cohere: coherence function between the ground excitation and the measured responses

  • Impulse: impulse response of the structure at sensor locations

Response Selection Window

Response selection window allows users to select responses to be shown on the response plot panel. It is straightforward to plot y(t), x-y, correlation functions and impulse response functions. When users select FFT, PSD, CSD, Xfer, or Cohere, a window as shown in Figure 3-(a) will pop up and change to Figure 3-(b) or (c) according to selected model.

As shown Figure 3-(b), only one response is allowed to be selected. However, users can compare responses from 4 different models by checking model selection check boxes on the control panel. If one of 4 models is selected, the response selection window will look like Figure 3-(c). Multiple responses can be chosen and compared all together.


Save Figures and Data

The VL supports two saving options, one for figures and the other for data. Figures shown on the response plot panels can be saved by clicking any figure except the virtual building. Figures are saved as PNG format. Users are also able to save all data by clicking the "Save Data" button on the bottom of the control panel.

Technical Backgrounds

Mathematical Model

The mathematical models used in this simulator are the same as those of Java-Powered Simulation for Nonlinear Multi-Story Buildings by Yong Gao. Click here to see the technical background for mathematical models.

Definition of parameters

Spectral Analysis

	   
	   
	   
	   
	   
	   
	   
	   
	   

Other Definitions


Homework



References


Acknowledgements

The support of the National Science Foundation through the Multidisciplinary Center for Earthquake Engineering Research (MCEER) is gratefully acknowledged.


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