1.11.9 Nonstructural mass verification

Products: ABAQUS/Standard  ABAQUS/Explicit  

Various methods for including a nonstructural mass in a model are tested. Most of the analyses consist of a set of reference elements that do not include a nonstructural mass and another set of test elements whose material density and nonstructural mass contribution are adjusted to make the total mass equal those of the reference elements. The response of the test elements should be identical to that of the reference elements.

I. Nonstructural mass specified in the form of a total mass over a region of uniform material density

Elements tested

B21    B22    B31    B32   

C3D4    C3D6    C3D8R    SC6R    SC8R   

CAX3    CAX4R   

CPE3    CPE4R    CPS3    CPS4R   

M3D3    M3D4R   

S3R    S4R    SAX1   

T2D2    T3D2   

Problem description

The nonstructural mass contribution is specified in the form of a total mass to be applied over an element set. Several element types are tested in each input file, with two elements in the model for each element type. Each element pair is subjected to equivalent displacements (and rotations in the case of beams and shells) such that their response is dynamic. Tests of membranes and shells are performed with and without the *NODAL THICKNESS option. The reaction forces for the constrained nodes of each pair of elements are output for comparison purposes.

Results and discussion

Reaction force histories for nodes on each pair of test and reference elements are nearly identical.

Input files

std_nsm_tot_continuum.inp

ABAQUS/Standard analysis of two-dimensional and three-dimensional continuum elements.

std_nsm_tot_beamshell.inp

ABAQUS/Standard analysis of two-dimensional and three-dimensional beams and shells.

xpl_nsm_tot_continuum.inp

ABAQUS/Explicit analysis of two-dimensional and three-dimensional continuum elements.

xpl_nsm_tot_beamshell.inp

ABAQUS/Explicit analysis of two-dimensional and three-dimensional beams and shells.

II. Nonstructural mass specified in the form of a total mass over a region of nonuniform material density

Elements tested

B21    B22    B31    B32   

C3D4    C3D6    C3D8R    SC6R    SC8R   

CAX3    CAX4R   

CPE3    CPE4R    CPS3    CPS4R   

M3D3    M3D4R   

S3R    S4R    SAX1   

T2D2    T3D2   

Problem description

The nonstructural mass contribution is specified in the form of a total mass to be applied over the entire model. Several element types are tested in each input file with two elements (test and reference) in the model for each element type. The material density of a “reference” element is chosen to be eight times that of a “test” element. A total mass equal to a third of all “reference” elements is distributed over the entire model. In the case of a mass proportional distribution of the nonstructural mass, the effective element densities of a “reference” element and a “test” element remain at the 8:1 ratio; with the volume proportional distribution, the ratio changes to 4:1. In either distribution any “test” and “reference” element pair would have different mass; hence, the reaction forces are not expected to match.

In ABAQUS/Explicit each element pair is subjected to equivalent displacements (and rotations in the case of beams and shells) such that their response is dynamic. In ABAQUS/Standard a single- step static analysis is carried out with gravity loads. Rebar defined using the *REBAR LAYER option are included where applicable. Under mass proportional distribution of a total nonstructural mass, the elements with rebar defined using the *REBAR LAYER option attract a higher nonstructural mass compared to those elements without the rebar. However, the same is not true when the rebar are defined using the *REBAR option. Tests of membranes and shells are performed with and without the *NODAL THICKNESS option. The reaction forces for the constrained nodes of each pair of elements are output. In ABAQUS/Explicit the element stable time increment values are also output for comparison. These values for a “reference” element and a “test” element are not expected to be identical but should correspond to the modified spatial distribution of the mass in the model.

Results and discussion

The masses of each “reference” and “test” element pair are output to the printed output (.dat) file using the *PREPRINT, MODEL=YES option. The results match the expected values.

Input files

std_nsm_tot_continuum_m.inp

ABAQUS/Standard analysis of two-dimensional and three-dimensional continuum elements with mass proportional distribution of the nonstructural mass.

std_nsm_tot_beamshell_m.inp

ABAQUS/Standard analysis of two-dimensional and three-dimensional beams and shells with mass proportional distribution of the nonstructural mass.

std_nsm_tot_continuum_v.inp

ABAQUS/Standard analysis of two-dimensional and three-dimensional continuum elements with volume proportional distribution of the nonstructural mass.

std_nsm_tot_beamshell_v.inp

ABAQUS/Standard analysis of two-dimensional and three-dimensional beams and shells with volume proportional distribution of the nonstructural mass.

xpl_nsm_tot_continuum_m.inp

ABAQUS/Explicit analysis of two-dimensional and three-dimensional continuum elements with mass proportional distribution of the nonstructural mass.

xpl_nsm_tot_beamshell_m.inp

ABAQUS/Explicit analysis of two-dimensional and three-dimensional beams and shells with mass proportional distribution of the nonstructural mass.

xpl_nsm_tot_continuum_v.inp

ABAQUS/Explicit analysis of two-dimensional and three-dimensional continuum elements with volume proportional distribution of the nonstructural mass.

xpl_nsm_tot_beamshell_v.inp

ABAQUS/Explicit analysis of two-dimensional and three-dimensional beams and shells with volume proportional distribution of the nonstructural mass.

III. Nonstructural mass specified in the form of a mass per unit volume

Elements tested

B21    B22    B31    B32   

C3D4    C3D6    C3D8R    SC6R    SC8R   

CAX3    CAX4R   

CPE3    CPE4R    CPS3    CPS4R   

M3D3    M3D4R   

S3R    S4R    SAX1   

T2D2    T3D2   

Problem description

The nonstructural mass contribution is specified in the form of a mass per unit volume to be applied over an element set. Several element types are tested in each input file, with two elements in the model for each element type. Each element pair is subjected to equivalent displacements (and rotations in the case of beams and shells) such that their response is dynamic. Tests of membranes and shells are performed with and without the *NODAL THICKNESS option. The reaction forces for the constrained nodes of each pair of elements are output for comparison purposes.

Results and discussion

Reaction force histories for nodes on each pair of test and reference elements are nearly identical.

Input files

std_nsm_mpv_continuum.inp

ABAQUS/Standard analysis of two-dimensional and three-dimensional continuum elements.

std_nsm_mpv_beamshell.inp

ABAQUS/Standard analysis of two-dimensional and three-dimensional beams and shells.

xpl_nsm_mpv_continuum.inp

ABAQUS/Explicit analysis of two-dimensional and three-dimensional continuum elements.

xpl_nsm_mpv_beamshell.inp

ABAQUS/Explicit analysis of two-dimensional and three-dimensional beams and shells.

IV. Nonstructural mass specified in the form of a mass per unit area

Elements tested

M3D3    M3D4R   

S3R    S4R    SAX1   

Problem description

The nonstructural mass contribution is specified in the form of a mass per unit area to be applied over an element set. Several element types are tested in each input file, with two elements in the model for each element type. Each element pair is subjected to equivalent displacements (and rotations in the case of beams and shells) such that their response is dynamic. Tests of membranes and shells are performed with and without the *NODAL THICKNESS option. The reaction forces for the constrained nodes of each pair of elements are output for comparison purposes.

Results and discussion

Reaction force histories for nodes on each pair of test and reference elements are nearly identical.

Input files

std_nsm_mpa_continuum.inp

ABAQUS/Standard analysis of two-dimensional and three-dimensional continuum elements.

std_nsm_mpa_beamshell.inp

ABAQUS/Standard analysis of two-dimensional and three-dimensional beams and shells.

xpl_nsm_mpa_continuum.inp

ABAQUS/Explicit analysis of two-dimensional and three-dimensional continuum elements.

xpl_nsm_mpa_beamshell.inp

ABAQUS/Explicit analysis of two-dimensional and three-dimensional beams and shells.

V. Nonstructural mass specified in the form of a mass per unit length

Elements tested

B21    B22    B31    B32   

T2D2    T3D2   

Problem description

The nonstructural mass contribution is specified in the form of a mass per unit length to be applied over an element set. Several element types are tested in each input file, with two elements in the model for each element type. Each element pair is subjected to equivalent displacements (and rotations in the case of beams and shells) such that their response is dynamic. The reaction forces for the constrained nodes of each pair of elements are output for comparison purposes.

Results and discussion

Reaction force histories for nodes on each pair of test and reference elements are nearly identical.

Input files

std_nsm_mpl_continuum.inp

ABAQUS/Standard analysis of two-dimensional and three-dimensional continuum elements.

std_nsm_mpl_beamshell.inp

ABAQUS/Standard analysis of two-dimensional and three-dimensional beams and shells.

xpl_nsm_mpl_continuum.inp

ABAQUS/Explicit analysis of two-dimensional and three-dimensional continuum elements.

xpl_nsm_mpl_beamshell.inp

ABAQUS/Explicit analysis of two-dimensional and three-dimensional beams and shells.