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roadspec

PURPOSE ^

Spectral density (frequency) for a road

SYNOPSIS ^

S = roadspec(sdata,a,C)

DESCRIPTION ^

 ROADSPEC Spectral density (frequency) for a road 
 
  CALL:  S = roadspec(data,a,C);
 
   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: This function is called by:

SOURCE CODE ^

001 function S = roadspec(sdata,a,C)
002 %ROADSPEC Spectral density (frequency) for a road 
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';
066 S.note='Spectrum: road spectrum';
067 S.S(wv<wl)=0;
068 S.S(1)=0; % must be zero at zero freq since discrete spectrum
069 
070

Mathematical Statistics
Centre for Mathematical Sciences
Lund University with Lund Institute of Technology

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