Home > wafo > damage > roadspec.m

## PURPOSE

Spectral density (frequency) for a road

## DESCRIPTION

``` ROADSPEC Spectral density (frequency) for a road

Output:
S = the spectral density (structure array)
Input:
sdata = the data vector [wl wu n], where

wl = lower truncation frequency  (default 4/257)
wu = upper truncation frequency  (default 4)
n  = number of evaluation points (default 257)
a,C  = constants in the spectral density

The model is given by

S(w) = C/(w^a),  wl < w < wu

Usually 2 < a < 3, see the literature. For the value of  c,
Kamash and Robson (1978) give the values

Motorway:  3e-8 < C < 50e-8
Highway:   3e-8 < C < 800e-8
Minor highway: 50e-8 < C < 3000e-8```

## CROSS-REFERENCE INFORMATION

This function calls:
 createspec Spectrum structure constructor linspace Linearly spaced vector.
This function is called by:

## SOURCE CODE

```001 function S = roadspec(sdata,a,C)
003 %
004 % CALL:  S = roadspec(data,a,C);
005 %
006 %  Output:
007 %        S = the spectral density (structure array)
008 %  Input:
009 %    sdata = the data vector [wl wu n], where
010 %
011 %    wl = lower truncation frequency  (default 4/257)
012 %    wu = upper truncation frequency  (default 4)
013 %    n  = number of evaluation points (default 257)
014 %     a,C  = constants in the spectral density
015 %
016 % The model is given by
017 %
018 %                    S(w) = C/(w^a),  wl < w < wu
019 %
020 % Usually 2 < a < 3, see the literature. For the value of  c,
021 % Kamash and Robson (1978) give the values
022 %
023 % Motorway:  3e-8 < C < 50e-8
024 % Highway:   3e-8 < C < 800e-8
025 % Minor highway: 50e-8 < C < 3000e-8
026 %
027
028 % References:
029 % Lindgren, G. (1981).
030 % Jumps and Bumps on Random Roads.
031 % Journal of Sound and Vibration, Vol 78, pp 383-395
032 %
033 % Kamash, K.M.A., and Robson, J.D. (1978).
034 % The Application of Isotropy in Road Surface Modelling
035 % Journal of Sound and Vibration, Vol 57, pp 89-100
036 %
037 % Jogréus, C. (1983).
038 % Fordonsrörelser och stokastiska vägmodeller.
039 % Master's thesis, Mathematical Statistics, Lund University
040
041 % Tested on Matlab 6.0
042 % History:
043 % Modified by jr 01-April-2001
044 % - structure array introduced
045 % - help text modified
046 % By Mats Frendahl, 1993
047
048
049 if nargin<1 | isempty(sdata), sdata = [4/257 4 357]; end
050 if nargin<2 | isempty(a), a = 2.1; end
051 if nargin<3 | isempty(C), C = 50e-8; end
052 if (a<2)|(a>3)
053   disp(' The parameter  a  must be in (2,3). Program will terminate.')
054   break
055 end
056
057 wl = sdata(1); wu = sdata(2); n = sdata(3);
058 wv = linspace(0,wu,n);
059 % wv = linspace(w0:(l1-l0)/(n-1):l1;  % OLD freq vector
060 spv = C*(wv.^a).^(-1);
061
062 S=createspec;
063 S.S=spv;
064 S.w=wv;
065 S.type='freq';