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
Spectrum structure constructor | |
Linearly spaced vector. |
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
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