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Basic Concepts

Boundary Conditions

Impedance Mismatch

Damping Effects

Natural Mode of Vibration

Transfer Function

Frequency Response

Time Stepping

Material Behavior

Dr. Layer 1.0

Introduction

Introduction

### Background

An understanding of the various loading types both ideal and practical is necessary for understanding the effects that will manifest in wave propagation mechanics of the travel media.

### Objective

This exercise will show how Dr. Layer attempts to visually display the different effects of varying load types. The objective is to appreciate the numerous effects that can be generated in practice when certain parameters are changed and the possible effects on structures.

### Things to Do

1. Open the Dr. Layer program. By default we get twelve layers. The top six layers are hardwired into the system with a very fast velocity. The bottom six layers are hardwired with a very slow velocity. The input loading is such that we can see its motion on the plot attached to the base node on the lowest layer.

2. For our purposes we can select the top layers and apply the select all option in the edit menu. Next go to the wave speed option and choose say, very slow.

3. There are four different loading types hardwired into the program. Default option comes up as sinusoidal. Observe the type of wave motion obtained.

4. Try changing the loading type to a ramp or a pulse type loading. Note what you observe.

5. The option for an earthquake load has a hardwired real earthquake loading type input. You are however encouraged to try obtaining an earthquake record (e.g. from the internet) save it as a .txt file extension. You can upload this file and note what you observe.

6. Change the default values for the amplitude and frequency. What do you observe?

7. Using only the pulse loading go to the options menu and make the base unreleased. Do you notice any difference in the input loading plots?

8. Repeat the process above for the ramp load.

Observation

### On Your Own

1. Observe Documented Earthquake motions on video. Relate this to what you have seen today.

2. Can you think of any other type of loading that exists not implemented in the program?
OnYourOwn