Home Basic Concepts Loading Boundary Conditions Impedance Mismatch Damping Effects Natural Mode of Vibration Transfer Function Frequency Response Time Stepping Material Behavior Dr. Layer 1.0 DrLayer Lessons on Wave Propagation in Layer Media Introduction Welcome to Dr. Layer Exercises. This page is designed to provide a simple overview of the concepts of wave propagation in layer media through the use of DrLayer. Each exercise or lesson introduces a variety of concepts related to wave propagation using simple visual experiments performed in real time. Simple step by step procedures are described for each problem followed by some recommendations or questions to expand the knowledge. Virtually all the functionality of the program DrLayer is presented in the accompanying exercises, and since the exercises present the program features in the context of the underlying concepts and principles, they provide the recommended way to be introduced to the program. Basic Concepts An introduction to basic concepts of 1-D wave propagation in layer media. The concepts of wave speed and wave length are visually introduced and possible analytical formulations are analyzed (.pdf). Loading Emphasizes different loading conditions used in the application. Exercises that display graphical representations of the layer structure with each load type are carried out. Boundary Conditions This exercise emphasizes the effect of various boundary conditions on the propagation of waves in layered media. Fixed supports at the base and a free support at the ends and vice versa could suffice. A practical understanding of these concepts is he focus of this exercise. (.pdf). Impedance Mismatch Describes specific impedance as a measure of density and wave velocity of a material. Impedance ratio is introduced as a relationship that quantifies the relative differences in material properties at boundaries. The attached exercise relates boundary conditions to impedance ratios. (.pdf). Damping Effects Damping is shown to be a process of steadily diminishing the amplitude of free vibration. The exercises attached to this section attempts to ascribe a visual representation to the different damping types we have. (.pdf). Natural Modes of Vibration Describes the period of vibration of a system as the time required to complete one cycle of free vibration (.pdf). Transfer Function Transfer functions are introduced as filters that are applied to an incoming signal to produce an output signal. The amplification function is also explained. The exercises attached to this section describe how both functions can be obtained using DrLayer(.pdf). Frequency Response Describes natural period of vibration of a system as the time required to complete one cycle of free vibration. The effects of varying the input frequency of the loading on the output earthquake loading are complicated with motions that span a broad range of frequencies. The exercises in this section accomplish the different effects obtained by varying frequency characteristics. The idea of resonance is further investigated. (.pdf). Time Stepping This exercise describes a variation on the computational side. It involves varying time step, i.e. the time it takes the numerical tool to repeat each iteration process. The exercises also displays the limiting value of time step above which analysis becomes unstable(.pdf). Material Behavior Yielding of materials is the focus of discussion in this section. The type of models employed for the analyses are explained. The differences between different models are highlighted. (.pdf). BACK TO TOP  Last Updated: 11/21/00 Contact us at: parduino@u.washington.edu