Hi Jason,
thank you for your fast answer,
Yes, I'm using CompSub=2.
Sorry if I were not that much clear at first, but I would like to check the effect of the foundation on the tower loads by giving foundation's mass, inertia and stiffness. To start a simulation with OpenFAST I need to give different shape modes of the tower based on the natural frequencies, which are calculated with the help of Bmodes v1.03.01 (Elastodyn_tower.dat). So far I simulated wind turbines with a rigid foundation, therefore I didn't need to consider foundation effects on the tower natural frequency, which I need to do now! My first question is how can I consider this effect of the foundation on the tower's natural frequency?
The other point is I would like to compare the calculated loads based on a rigid foundation (CompSub=0) with a modelled foundation (CompSub=2). I don't need to calculate the loads on the foundation and as I know the platform degrees of freedom ( in Elastodyn.dat) only support the offshore foundations.
The question is, shall I turn on the degrees of freedom of the platform by setting them "True" or not? and does OpenFAST consider the given foundation parameters by the external file (External Platform MCKF) to calculate the tower's loads when these degree of freedoms are "false" or not?
False PtfmSgDOF  Platform horizontal surge translation DOF (flag)
False PtfmSwDOF  Platform horizontal sway translation DOF (flag)
False PtfmHvDOF  Platform vertical heave translation DOF (flag)
False PtfmRDOF  Platform roll tilt rotation DOF (flag)
False PtfmPDOF  Platform pitch tilt rotation DOF (flag)
False PtfmYDOF  Platform yaw rotation DOF (flag)
Kind regards,
Meriem Mbarek
Modeling of linear foundation for onshore turbine
Moderator: Bonnie.Jonkman

 Posts: 7
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 Organization: ENSTAB
 Location: TUNISIA

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 Contact:
Re: Modeling of linear foundation for onshore turbine
Dear Meriem,
Just a few comments:
Just a few comments:
 To model a flexible foundation, you can use CompSub = 2 or wait until the new SoilDyn/SubDyn capabilities are available. Regardless, if you intend to use CompSub = 2 and model the tower in ElastoDyn, then you should specify the mass/stiffness/damping of the foundation in ExtPtfm and modify the tower mode shapes in ElastoDyn based on the mass/stiffness of the foundation (towerbase boundary condition); BModes_JJ can be used to calculate the tower mode shapes. Any change to the mass/stiffness of the foundation in ExtPtfm or to the tower mode shapes in ElastoDyn will impact the tower natural frequency.
 CompSub = 2 and the ElastoDyn platform DOFs work for either onshore or offshore wind turbines.
 If all of the ElastoDyn platform DOFs are disabled, then ExtPtfm will not have any effect; ExtPtfm will only have an effect on the solution if at least one ElastoDyn platform DOF is enabled.
Jason Jonkman, Ph.D.
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

 Posts: 7
 Joined: Thu Jun 04, 2020 3:09 pm
 Organization: ENSTAB
 Location: TUNISIA
Re: Modeling of linear foundation for onshore turbine
Dear Jason,
Thank you for your help.
best regards,
Thank you for your help.
best regards,

 Posts: 7
 Joined: Thu Jun 04, 2020 3:09 pm
 Organization: ENSTAB
 Location: TUNISIA
Re: Modeling of linear foundation for onshore turbine
Dear Jason ,
Sorry, i would like ask about BModes_jj:
i tried first time without considering the foundation(hub_conn=1), and i have as a result for the natural frequency:
eigenvalue( 1) = 0.493762D+11 mode 1 frequency = 0.370346
When i consider the foundation i have as a resulat(hub_conn=3) :
eigenvalue( 1) = 0.436656D+05 mode 1 frequency = 0.000348
i would expect to find the natural frequency few percent lower than this value with the consideration of the interaction between foundation and the soil with the consideration of the rotation about horizontal axes wind turbine.
====================== BModes v3.00 Main Input File ==================
NREL 5MW Tower
 General parameters 
true Echo Echo input file contents to *.echo file if true.
2 beam_type 1: blade, 2: tower ()
0. romg: rotor speed, automatically set to zero for tower modal analysis (rpm)
1. romg_mult: rotor speed muliplicative factor ()
87.6 radius: rotor tip radius measured along coned blade axis, OR tower height above ground level [onshore] or MSL [offshore](m)
0. hub_rad: hub radius measured along coned blade axis OR tower rigidbase height (m)
0. precone: builtin precone angle, automatically set to zero for a tower (deg)
0. bl_thp: blade pitch setting, automatically set to zero for a tower (deg)
3 hub_conn: hubtoblade or towerbase boundary condition [1: cantilevered; 2: freefree; 3: only axial and torsion constraints] ()
20 modepr: number of modes to be printed ()
t TabDelim (true: tabdelimited output tables; false: spacedelimited tables)
f mid_node_tw (true: output twist at midnode of elements; false: no midnode outputs)
 Bladetip or towertop mass properties 
3.500003109E+005 tip_mass bladetip or towertop mass (kg)
0.4137754432 cm_loc tipmass c.m. offset from the tower axis measured along xtower axis (m)
1.9669893542 cm_axial tipmass c.m. offset tower tip measures axially along the z axis (m)
4.370E7 ixx_tip blade lag mass moment of inertia about the tipsection x reference axis (kgm^2)
2.353E7 iyy_tip blade flap mass moment of inertia about the tipsection y reference axis (kgm^2)
2.542E7 izz_tip torsion mass moment of inertia about the tipsection z reference axis (kgm^2)
0. ixy_tip cross product of inertia about x and y reference axes(kgm^2)
1.169E6 izx_tip cross product of inertia about z and x reference axes(kgm^2)
0. iyz_tip cross product of inertia about y and z reference axes(kgm^2)
 Distributedproperty identifiers 
1 id_mat: material_type [1: isotropic; nonisotropic composites option not yet available]
'CS_monopile_tower_secs.dat' : sec_props_file name of beam section properties file ()
Property scaling factors..............................
1.0 sec_mass_mult: mass density multiplier ()
1.0 flp_iner_mult: blade flap or tower fa inertia multiplier ()
1.0 lag_iner_mult: blade lag or tower ss inertia multiplier ()
1.0 flp_stff_mult: blade flap or tower fa bending stiffness multiplier ()
1.0 edge_stff_mult: blade lag or tower ss bending stiffness multiplier ()
1.0 tor_stff_mult: torsion stiffness multiplier ()
1.0 axial_stff_mult: axial stiffness multiplier ()
1.0 cg_offst_mult: cg offset multiplier ()
1.0 sc_offst_mult: shear center multiplier ()
1.0 tc_offst_mult: tension center multiplier ()
 Finite element discretization 
61 nselt: no of blade or tower elements ()
Distance of element boundary nodes from blade or flexibletower root (normalized wrt blade or tower length), el_loc()
0 0.003481894 0.010445682 0.017409471 0.024373259 0.031337047 0.038300836 0.045264624 0.052228412 0.059192201 0.066155989 0.073119777 0.080083565 0.087047354 0.094011142 0.10097493 0.107938719 0.114902507 0.121866295 0.128830084 0.135793872 0.13990 0.149721448 0.156685237 0.163649025 0.170612813 0.177576602 0.18454039 0.191504178 0.198467967 0.205431755 0.212395543 0.219359331 0.22632312 0.233286908 0.240250696 0.247214485 0.250696379 0.320334262 0.37971 0.424791072 0.45961 0.486635 0.51366 0.54068 0.5677 0.594715 0.62173 0.64875 0.67577 0.70279 0.72981 0.75683 0.78385 0.81087 0.83789 0.864905 0.89192 0.91894 0.94596 0.97298 1.0
 Properties of tower support subsystem (read only if beam_type is 2) 
0 tow_support: : aditional tower support [0: no additional support; 1: floatingplatform or monopile with or without tension wires] ()
0.0 draft : depth of tower base from the ground or the MSL (mean sea level) (m)
0.0 cm_pform : distance of platform c.m. below the MSL (m)
0 mass_pform : platform mass (kg)
Platform mass inertia 3X3 matrix (i_matrix_pform):
0. 0. 0.
0. 0. 0.
0. 0. 0.
0.0 ref_msl : distance of platform reference point below the MSL (m)
Platformreferencepointreferred hydrodynamic 6X6 matrix (hydro_M):
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 5.650000E+7 0. 0.
0. 0. 0. 0. 5.650000E+07 0.
0. 0. 0. 0. 0. 0.
Platformreferencepointreferred hydrodynamic 6X6 stiffness matrix (hydro_K):
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 4.356000E+10 0. 0.
0. 0. 0. 0. 4.356000E+10 0.
0. 0. 0. 0. 0. 0.
Mooringsystem 6X6 stiffness matrix (mooring_K):
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
Distributed (hydrodynamic) addedmass per unit length along a flexible portion of the tower length:
0 n_secs_m_distr: number of sections at which added mass per unit length is specified ()
0. 0. : z_distr_m [row array of size n_added_m_pts; section locations wrt the flexible tower base over which distributed mass is specified] (m)
0. 0. : distr_m [row array of size n_added_m_pts; added distributed masses per unit length] (kg/m)
Distributed elastic stiffness per unit length along a flexible portion of the tower length:
0 n_secs_k_distr: number of points at which distributed stiffness per unit length is specified ()
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 : z_distr_k [row array of size n_added_m_pts; section locations wrt the flexible tower base over which distributed stiffness is specified] (m)
595318000.0 1165208000 1129400000 1095553000 1059931000 1024493000 989209000 953643000 918718000 883287000 847803000 812541000 777187000 741870000 706616000 671440000 636229000 600957000 565919000 530470000 495081000 459574000 385327000 305479000 280059000 254125000 227500000 200112000 171927000 143115000 114173000 80184000 52237000 35561000 20912000 9000000 1156000 : distr_k [row array of size n_added_m_pts; distributed stiffness per unit length] (N/m^2)
Tension wires data
0 n_attachments: no of wireattachment locations on tower [0: no tension wires] ()
3 3 n_wires: no of wires attached at each location (must be 3 or higher) ()
6 9 node_attach: node numbers of attacments location (node number must be more than 1 and less than nselt+2) ()
0.e0 0.e0 wire_stfness: wire spring constant in each set (see users' manual) (N/m)
0. 0. th_wire: angle of tension wires (wrt the horizontal ground plane) at each attachment point (deg)
END of Main Input File Data *********************************************************************
*************************************************************************************************
Best regards
Sorry, i would like ask about BModes_jj:
i tried first time without considering the foundation(hub_conn=1), and i have as a result for the natural frequency:
eigenvalue( 1) = 0.493762D+11 mode 1 frequency = 0.370346
When i consider the foundation i have as a resulat(hub_conn=3) :
eigenvalue( 1) = 0.436656D+05 mode 1 frequency = 0.000348
i would expect to find the natural frequency few percent lower than this value with the consideration of the interaction between foundation and the soil with the consideration of the rotation about horizontal axes wind turbine.
====================== BModes v3.00 Main Input File ==================
NREL 5MW Tower
 General parameters 
true Echo Echo input file contents to *.echo file if true.
2 beam_type 1: blade, 2: tower ()
0. romg: rotor speed, automatically set to zero for tower modal analysis (rpm)
1. romg_mult: rotor speed muliplicative factor ()
87.6 radius: rotor tip radius measured along coned blade axis, OR tower height above ground level [onshore] or MSL [offshore](m)
0. hub_rad: hub radius measured along coned blade axis OR tower rigidbase height (m)
0. precone: builtin precone angle, automatically set to zero for a tower (deg)
0. bl_thp: blade pitch setting, automatically set to zero for a tower (deg)
3 hub_conn: hubtoblade or towerbase boundary condition [1: cantilevered; 2: freefree; 3: only axial and torsion constraints] ()
20 modepr: number of modes to be printed ()
t TabDelim (true: tabdelimited output tables; false: spacedelimited tables)
f mid_node_tw (true: output twist at midnode of elements; false: no midnode outputs)
 Bladetip or towertop mass properties 
3.500003109E+005 tip_mass bladetip or towertop mass (kg)
0.4137754432 cm_loc tipmass c.m. offset from the tower axis measured along xtower axis (m)
1.9669893542 cm_axial tipmass c.m. offset tower tip measures axially along the z axis (m)
4.370E7 ixx_tip blade lag mass moment of inertia about the tipsection x reference axis (kgm^2)
2.353E7 iyy_tip blade flap mass moment of inertia about the tipsection y reference axis (kgm^2)
2.542E7 izz_tip torsion mass moment of inertia about the tipsection z reference axis (kgm^2)
0. ixy_tip cross product of inertia about x and y reference axes(kgm^2)
1.169E6 izx_tip cross product of inertia about z and x reference axes(kgm^2)
0. iyz_tip cross product of inertia about y and z reference axes(kgm^2)
 Distributedproperty identifiers 
1 id_mat: material_type [1: isotropic; nonisotropic composites option not yet available]
'CS_monopile_tower_secs.dat' : sec_props_file name of beam section properties file ()
Property scaling factors..............................
1.0 sec_mass_mult: mass density multiplier ()
1.0 flp_iner_mult: blade flap or tower fa inertia multiplier ()
1.0 lag_iner_mult: blade lag or tower ss inertia multiplier ()
1.0 flp_stff_mult: blade flap or tower fa bending stiffness multiplier ()
1.0 edge_stff_mult: blade lag or tower ss bending stiffness multiplier ()
1.0 tor_stff_mult: torsion stiffness multiplier ()
1.0 axial_stff_mult: axial stiffness multiplier ()
1.0 cg_offst_mult: cg offset multiplier ()
1.0 sc_offst_mult: shear center multiplier ()
1.0 tc_offst_mult: tension center multiplier ()
 Finite element discretization 
61 nselt: no of blade or tower elements ()
Distance of element boundary nodes from blade or flexibletower root (normalized wrt blade or tower length), el_loc()
0 0.003481894 0.010445682 0.017409471 0.024373259 0.031337047 0.038300836 0.045264624 0.052228412 0.059192201 0.066155989 0.073119777 0.080083565 0.087047354 0.094011142 0.10097493 0.107938719 0.114902507 0.121866295 0.128830084 0.135793872 0.13990 0.149721448 0.156685237 0.163649025 0.170612813 0.177576602 0.18454039 0.191504178 0.198467967 0.205431755 0.212395543 0.219359331 0.22632312 0.233286908 0.240250696 0.247214485 0.250696379 0.320334262 0.37971 0.424791072 0.45961 0.486635 0.51366 0.54068 0.5677 0.594715 0.62173 0.64875 0.67577 0.70279 0.72981 0.75683 0.78385 0.81087 0.83789 0.864905 0.89192 0.91894 0.94596 0.97298 1.0
 Properties of tower support subsystem (read only if beam_type is 2) 
0 tow_support: : aditional tower support [0: no additional support; 1: floatingplatform or monopile with or without tension wires] ()
0.0 draft : depth of tower base from the ground or the MSL (mean sea level) (m)
0.0 cm_pform : distance of platform c.m. below the MSL (m)
0 mass_pform : platform mass (kg)
Platform mass inertia 3X3 matrix (i_matrix_pform):
0. 0. 0.
0. 0. 0.
0. 0. 0.
0.0 ref_msl : distance of platform reference point below the MSL (m)
Platformreferencepointreferred hydrodynamic 6X6 matrix (hydro_M):
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 5.650000E+7 0. 0.
0. 0. 0. 0. 5.650000E+07 0.
0. 0. 0. 0. 0. 0.
Platformreferencepointreferred hydrodynamic 6X6 stiffness matrix (hydro_K):
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 4.356000E+10 0. 0.
0. 0. 0. 0. 4.356000E+10 0.
0. 0. 0. 0. 0. 0.
Mooringsystem 6X6 stiffness matrix (mooring_K):
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
Distributed (hydrodynamic) addedmass per unit length along a flexible portion of the tower length:
0 n_secs_m_distr: number of sections at which added mass per unit length is specified ()
0. 0. : z_distr_m [row array of size n_added_m_pts; section locations wrt the flexible tower base over which distributed mass is specified] (m)
0. 0. : distr_m [row array of size n_added_m_pts; added distributed masses per unit length] (kg/m)
Distributed elastic stiffness per unit length along a flexible portion of the tower length:
0 n_secs_k_distr: number of points at which distributed stiffness per unit length is specified ()
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 : z_distr_k [row array of size n_added_m_pts; section locations wrt the flexible tower base over which distributed stiffness is specified] (m)
595318000.0 1165208000 1129400000 1095553000 1059931000 1024493000 989209000 953643000 918718000 883287000 847803000 812541000 777187000 741870000 706616000 671440000 636229000 600957000 565919000 530470000 495081000 459574000 385327000 305479000 280059000 254125000 227500000 200112000 171927000 143115000 114173000 80184000 52237000 35561000 20912000 9000000 1156000 : distr_k [row array of size n_added_m_pts; distributed stiffness per unit length] (N/m^2)
Tension wires data
0 n_attachments: no of wireattachment locations on tower [0: no tension wires] ()
3 3 n_wires: no of wires attached at each location (must be 3 or higher) ()
6 9 node_attach: node numbers of attacments location (node number must be more than 1 and less than nselt+2) ()
0.e0 0.e0 wire_stfness: wire spring constant in each set (see users' manual) (N/m)
0. 0. th_wire: angle of tension wires (wrt the horizontal ground plane) at each attachment point (deg)
END of Main Input File Data *********************************************************************
*************************************************************************************************
Best regards

 Posts: 5882
 Joined: Thu Nov 03, 2005 4:38 pm
 Location: Boulder, CO
 Contact:
Re: Modeling of linear foundation for onshore turbine
Dear Meriem,
With hub_conn = 3, the towerbase (platform) point has 4 DOFssurge, sway, roll, and pitch. It looks like you've specified the lumped inertia and stiffness in roll/pitch, but you have not specified any stiffness in surge and sway. This will result in two rigidbody modes (in surge and sway), each with zero frequency (or nearzero frequency due to numerical round off in the solution).
Best regards,
With hub_conn = 3, the towerbase (platform) point has 4 DOFssurge, sway, roll, and pitch. It looks like you've specified the lumped inertia and stiffness in roll/pitch, but you have not specified any stiffness in surge and sway. This will result in two rigidbody modes (in surge and sway), each with zero frequency (or nearzero frequency due to numerical round off in the solution).
Best regards,
Jason Jonkman, Ph.D.
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

 Posts: 7
 Joined: Thu Jun 04, 2020 3:09 pm
 Organization: ENSTAB
 Location: TUNISIA
Re: Modeling of linear foundation for onshore turbine
Dear Jason,
thank you for your fast reply , i would like to tell you although I have changed the values of the matrix but the result of the natural frequency it is the same :
eigenvalue( 1) = 0.436656D+05 mode 1 frequency = 0.000348
====================== BModes v3.00 Main Input File ==================
NREL 5MW Tower
 General parameters 
true Echo Echo input file contents to *.echo file if true.
2 beam_type 1: blade, 2: tower ()
0. romg: rotor speed, automatically set to zero for tower modal analysis (rpm)
1. romg_mult: rotor speed muliplicative factor ()
87.6 radius: rotor tip radius measured along coned blade axis, OR tower height above ground level [onshore] or MSL [offshore](m)
0. hub_rad: hub radius measured along coned blade axis OR tower rigidbase height (m)
0. precone: builtin precone angle, automatically set to zero for a tower (deg)
0. bl_thp: blade pitch setting, automatically set to zero for a tower (deg)
3 hub_conn: hubtoblade or towerbase boundary condition [1: cantilevered; 2: freefree; 3: only axial and torsion constraints] ()
20 modepr: number of modes to be printed ()
t TabDelim (true: tabdelimited output tables; false: spacedelimited tables)
f mid_node_tw (true: output twist at midnode of elements; false: no midnode outputs)
 Bladetip or towertop mass properties 
3.500003109E+005 tip_mass bladetip or towertop mass (kg)
0.4137754432 cm_loc tipmass c.m. offset from the tower axis measured along xtower axis (m)
1.9669893542 cm_axial tipmass c.m. offset tower tip measures axially along the z axis (m)
4.370E7 ixx_tip blade lag mass moment of inertia about the tipsection x reference axis (kgm^2)
2.353E7 iyy_tip blade flap mass moment of inertia about the tipsection y reference axis (kgm^2)
2.542E7 izz_tip torsion mass moment of inertia about the tipsection z reference axis (kgm^2)
0. ixy_tip cross product of inertia about x and y reference axes(kgm^2)
1.169E6 izx_tip cross product of inertia about z and x reference axes(kgm^2)
0. iyz_tip cross product of inertia about y and z reference axes(kgm^2)
 Distributedproperty identifiers 
1 id_mat: material_type [1: isotropic; nonisotropic composites option not yet available]
'CS_monopile_tower_secs.dat' : sec_props_file name of beam section properties file ()
Property scaling factors..............................
1.0 sec_mass_mult: mass density multiplier ()
1.0 flp_iner_mult: blade flap or tower fa inertia multiplier ()
1.0 lag_iner_mult: blade lag or tower ss inertia multiplier ()
1.0 flp_stff_mult: blade flap or tower fa bending stiffness multiplier ()
1.0 edge_stff_mult: blade lag or tower ss bending stiffness multiplier ()
1.0 tor_stff_mult: torsion stiffness multiplier ()
1.0 axial_stff_mult: axial stiffness multiplier ()
1.0 cg_offst_mult: cg offset multiplier ()
1.0 sc_offst_mult: shear center multiplier ()
1.0 tc_offst_mult: tension center multiplier ()
 Finite element discretization 
61 nselt: no of blade or tower elements ()
Distance of element boundary nodes from blade or flexibletower root (normalized wrt blade or tower length), el_loc()
0 0.003481894 0.010445682 0.017409471 0.024373259 0.031337047 0.038300836 0.045264624 0.052228412 0.059192201 0.066155989 0.073119777 0.080083565 0.087047354 0.094011142 0.10097493 0.107938719 0.114902507 0.121866295 0.128830084 0.135793872 0.13990 0.149721448 0.156685237 0.163649025 0.170612813 0.177576602 0.18454039 0.191504178 0.198467967 0.205431755 0.212395543 0.219359331 0.22632312 0.233286908 0.240250696 0.247214485 0.250696379 0.320334262 0.37971 0.424791072 0.45961 0.486635 0.51366 0.54068 0.5677 0.594715 0.62173 0.64875 0.67577 0.70279 0.72981 0.75683 0.78385 0.81087 0.83789 0.864905 0.89192 0.91894 0.94596 0.97298 1.0
 Properties of tower support subsystem (read only if beam_type is 2) 
0 tow_support: : aditional tower support [0: no additional support; 1: floatingplatform or monopile with or without tension wires] ()
0.0 draft : depth of tower base from the ground or the MSL (mean sea level) (m)
0.0 cm_pform : distance of platform c.m. below the MSL (m)
8.119E+10 mass_pform : platform mass (kg)
Platform mass inertia 3X3 matrix (i_matrix_pform):
0. 0. 0.
0. 0. 0.
0. 0. 0.
0.0 ref_msl : distance of platform reference point below the MSL (m)
Platformreferencepointreferred hydrodynamic 6X6 matrix (hydro_M):
8.119000E+10 0. 0. 0. 0. 0.
0. 8.119000E+10 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 5.650000E+7 0. 0.
0. 0. 0. 0. 5.650000E+07 0.
0. 0. 0. 0. 0. 0.
Platformreferencepointreferred hydrodynamic 6X6 stiffness matrix (hydro_K):
6.036395E+08 0. 0. 0. 0. 0.
0. 6.036395E+08 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 1.074849E+10 0. 0.
0. 0. 0. 0. 1.074849E+10 0.
0. 0. 0. 0. 0. 0.
Mooringsystem 6X6 stiffness matrix (mooring_K):
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
Distributed (hydrodynamic) addedmass per unit length along a flexible portion of the tower length:
0. n_secs_m_distr: number of sections at which added mass per unit length is specified ()
0. 0. : z_distr_m [row array of size n_added_m_pts; section locations wrt the flexible tower base over which distributed mass is specified] (m)
0. 0. : distr_m [row array of size n_added_m_pts; added distributed masses per unit length] (kg/m)
Distributed elastic stiffness per unit length along a flexible portion of the tower length:
0 n_secs_k_distr: number of points at which distributed stiffness per unit length is specified ()
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 : z_distr_k [row array of size n_added_m_pts; section locations wrt the flexible tower base over which distributed stiffness is specified] (m)
595318000.0 1165208000 1129400000 1095553000 1059931000 1024493000 989209000 953643000 918718000 883287000 847803000 812541000 777187000 741870000 706616000 671440000 636229000 600957000 565919000 530470000 495081000 459574000 385327000 305479000 280059000 254125000 227500000 200112000 171927000 143115000 114173000 80184000 52237000 35561000 20912000 9000000 1156000 : distr_k [row array of size n_added_m_pts; distributed stiffness per unit length] (N/m^2)
Tension wires data
0 n_attachments: no of wireattachment locations on tower [0: no tension wires] ()
3 3 n_wires: no of wires attached at each location (must be 3 or higher) ()
6 9 node_attach: node numbers of attacments location (node number must be more than 1 and less than nselt+2) ()
0.e0 0.e0 wire_stfness: wire spring constant in each set (see users' manual) (N/m)
0. 0. th_wire: angle of tension wires (wrt the horizontal ground plane) at each attachment point (deg)
END of Main Input File Data *********************************************************************
*************************************************************************************************
Best regards,
thank you for your fast reply , i would like to tell you although I have changed the values of the matrix but the result of the natural frequency it is the same :
eigenvalue( 1) = 0.436656D+05 mode 1 frequency = 0.000348
====================== BModes v3.00 Main Input File ==================
NREL 5MW Tower
 General parameters 
true Echo Echo input file contents to *.echo file if true.
2 beam_type 1: blade, 2: tower ()
0. romg: rotor speed, automatically set to zero for tower modal analysis (rpm)
1. romg_mult: rotor speed muliplicative factor ()
87.6 radius: rotor tip radius measured along coned blade axis, OR tower height above ground level [onshore] or MSL [offshore](m)
0. hub_rad: hub radius measured along coned blade axis OR tower rigidbase height (m)
0. precone: builtin precone angle, automatically set to zero for a tower (deg)
0. bl_thp: blade pitch setting, automatically set to zero for a tower (deg)
3 hub_conn: hubtoblade or towerbase boundary condition [1: cantilevered; 2: freefree; 3: only axial and torsion constraints] ()
20 modepr: number of modes to be printed ()
t TabDelim (true: tabdelimited output tables; false: spacedelimited tables)
f mid_node_tw (true: output twist at midnode of elements; false: no midnode outputs)
 Bladetip or towertop mass properties 
3.500003109E+005 tip_mass bladetip or towertop mass (kg)
0.4137754432 cm_loc tipmass c.m. offset from the tower axis measured along xtower axis (m)
1.9669893542 cm_axial tipmass c.m. offset tower tip measures axially along the z axis (m)
4.370E7 ixx_tip blade lag mass moment of inertia about the tipsection x reference axis (kgm^2)
2.353E7 iyy_tip blade flap mass moment of inertia about the tipsection y reference axis (kgm^2)
2.542E7 izz_tip torsion mass moment of inertia about the tipsection z reference axis (kgm^2)
0. ixy_tip cross product of inertia about x and y reference axes(kgm^2)
1.169E6 izx_tip cross product of inertia about z and x reference axes(kgm^2)
0. iyz_tip cross product of inertia about y and z reference axes(kgm^2)
 Distributedproperty identifiers 
1 id_mat: material_type [1: isotropic; nonisotropic composites option not yet available]
'CS_monopile_tower_secs.dat' : sec_props_file name of beam section properties file ()
Property scaling factors..............................
1.0 sec_mass_mult: mass density multiplier ()
1.0 flp_iner_mult: blade flap or tower fa inertia multiplier ()
1.0 lag_iner_mult: blade lag or tower ss inertia multiplier ()
1.0 flp_stff_mult: blade flap or tower fa bending stiffness multiplier ()
1.0 edge_stff_mult: blade lag or tower ss bending stiffness multiplier ()
1.0 tor_stff_mult: torsion stiffness multiplier ()
1.0 axial_stff_mult: axial stiffness multiplier ()
1.0 cg_offst_mult: cg offset multiplier ()
1.0 sc_offst_mult: shear center multiplier ()
1.0 tc_offst_mult: tension center multiplier ()
 Finite element discretization 
61 nselt: no of blade or tower elements ()
Distance of element boundary nodes from blade or flexibletower root (normalized wrt blade or tower length), el_loc()
0 0.003481894 0.010445682 0.017409471 0.024373259 0.031337047 0.038300836 0.045264624 0.052228412 0.059192201 0.066155989 0.073119777 0.080083565 0.087047354 0.094011142 0.10097493 0.107938719 0.114902507 0.121866295 0.128830084 0.135793872 0.13990 0.149721448 0.156685237 0.163649025 0.170612813 0.177576602 0.18454039 0.191504178 0.198467967 0.205431755 0.212395543 0.219359331 0.22632312 0.233286908 0.240250696 0.247214485 0.250696379 0.320334262 0.37971 0.424791072 0.45961 0.486635 0.51366 0.54068 0.5677 0.594715 0.62173 0.64875 0.67577 0.70279 0.72981 0.75683 0.78385 0.81087 0.83789 0.864905 0.89192 0.91894 0.94596 0.97298 1.0
 Properties of tower support subsystem (read only if beam_type is 2) 
0 tow_support: : aditional tower support [0: no additional support; 1: floatingplatform or monopile with or without tension wires] ()
0.0 draft : depth of tower base from the ground or the MSL (mean sea level) (m)
0.0 cm_pform : distance of platform c.m. below the MSL (m)
8.119E+10 mass_pform : platform mass (kg)
Platform mass inertia 3X3 matrix (i_matrix_pform):
0. 0. 0.
0. 0. 0.
0. 0. 0.
0.0 ref_msl : distance of platform reference point below the MSL (m)
Platformreferencepointreferred hydrodynamic 6X6 matrix (hydro_M):
8.119000E+10 0. 0. 0. 0. 0.
0. 8.119000E+10 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 5.650000E+7 0. 0.
0. 0. 0. 0. 5.650000E+07 0.
0. 0. 0. 0. 0. 0.
Platformreferencepointreferred hydrodynamic 6X6 stiffness matrix (hydro_K):
6.036395E+08 0. 0. 0. 0. 0.
0. 6.036395E+08 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 1.074849E+10 0. 0.
0. 0. 0. 0. 1.074849E+10 0.
0. 0. 0. 0. 0. 0.
Mooringsystem 6X6 stiffness matrix (mooring_K):
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
0. 0. 0. 0. 0. 0.
Distributed (hydrodynamic) addedmass per unit length along a flexible portion of the tower length:
0. n_secs_m_distr: number of sections at which added mass per unit length is specified ()
0. 0. : z_distr_m [row array of size n_added_m_pts; section locations wrt the flexible tower base over which distributed mass is specified] (m)
0. 0. : distr_m [row array of size n_added_m_pts; added distributed masses per unit length] (kg/m)
Distributed elastic stiffness per unit length along a flexible portion of the tower length:
0 n_secs_k_distr: number of points at which distributed stiffness per unit length is specified ()
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 : z_distr_k [row array of size n_added_m_pts; section locations wrt the flexible tower base over which distributed stiffness is specified] (m)
595318000.0 1165208000 1129400000 1095553000 1059931000 1024493000 989209000 953643000 918718000 883287000 847803000 812541000 777187000 741870000 706616000 671440000 636229000 600957000 565919000 530470000 495081000 459574000 385327000 305479000 280059000 254125000 227500000 200112000 171927000 143115000 114173000 80184000 52237000 35561000 20912000 9000000 1156000 : distr_k [row array of size n_added_m_pts; distributed stiffness per unit length] (N/m^2)
Tension wires data
0 n_attachments: no of wireattachment locations on tower [0: no tension wires] ()
3 3 n_wires: no of wires attached at each location (must be 3 or higher) ()
6 9 node_attach: node numbers of attacments location (node number must be more than 1 and less than nselt+2) ()
0.e0 0.e0 wire_stfness: wire spring constant in each set (see users' manual) (N/m)
0. 0. th_wire: angle of tension wires (wrt the horizontal ground plane) at each attachment point (deg)
END of Main Input File Data *********************************************************************
*************************************************************************************************
Best regards,

 Posts: 5882
 Joined: Thu Nov 03, 2005 4:38 pm
 Location: Boulder, CO
 Contact:
Re: Modeling of linear foundation for onshore turbine
Hi Meriem,
I see that you've also set tow_support = 0, which means nothing in the section "properties of the tower support subsystem" will be used. This means that actually you'll have 4 rigid body modes. Set tow_support = 1.
Best regards,
I see that you've also set tow_support = 0, which means nothing in the section "properties of the tower support subsystem" will be used. This means that actually you'll have 4 rigid body modes. Set tow_support = 1.
Best regards,
Jason Jonkman, Ph.D.
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

 Posts: 7
 Joined: Thu Jun 04, 2020 3:09 pm
 Organization: ENSTAB
 Location: TUNISIA
Re: Modeling of linear foundation for onshore turbine
Dear Jason,
Thank you for your helpful response! We appreciate.
Kind regards,
Thank you for your helpful response! We appreciate.
Kind regards,
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