Calculated for each mode in global translation and rotation directions high value in a direction indicates that the mode will be excited by forces in that direction values are relative based on a unit displacement spectrum the final participation factor. Mass includes all dead weight of structure may include some live load has units of forceacceleration internal force acceleration 1. After an eigenfrequency step has been used to find the eigenvalues of a model, abaqus standard automatically calculates the participation factor, the effective mass, and the composite modal damping for each mode so that these variables are available for use in. The rotational participation factors arent much use unless youre inputting rotational spectra. When the responsespectrum curve is defined, acceleration is typically entered as a fraction of gravitational acceleration 9. Heat transfer and thermalstress analysis to support the. Five typical structures have been demonstrated to check the validity.
The ams eigensolver does not compute composite modal damping factors when. In a previous post understanding the mass participation factor i have talked about the modal analysis in solidworks and how to make the most of it. Sep 06, 2012 till now we are not considering the mass participation factor for targeting the modes. Adams is a registered united states trademark of mechanical dynamics, inc.
Apr 28, 2006 the participation factors are tabulated in the output results or you can write off the current participation factors a load step at a time and access them via apdl. Henceforth, and in other abaqusstandard documentation, the term eigenvalue is used. For point mass and rotary inertia elements in abaqus standard mass proportional or composite modal damping are defined as part of the point mass or rotary inertia definitions point masses, section 24. Weisser2 1daimlerchrysler d71059 sindelfingen, 2ballard power systems ag d 73230 kirchheimteck. If the crosssection of the beam is very slightly nonsymmetric, the effective mass for mode 1 acts entirely along the y axis and the effective mass for mode 2 acts entirely. The modal mass participation ratio is widely used as the metric to determine the relative significance of modes in a modal response spectrum analysis. How can i view modal participation factor after carrying out. Responsespectrum analysis faq technical knowledge base. Coupled transverse vibration modeling of drillstrings.
Abaquscae is the preprocessor and abaqusviewer in the post processor. Certifies that this is the approved version of the following thesis. Cosmosm advanced modules 11 1 introduction introduction the advanced dynamic module, astar or post dynamic, has three principal functions. See faq5691083 for details on how to make best use of. This factor is not available for rotary inertia elements in abaqus explicit. How can i speed up the running time of my model with abaqus. Hence, an artificial low frequency mode is introduced for every degree of freedom in a secondary base. Abaqus standard chooses each big mass equal to 10 6 times the total. This page is devoted to frequently asked questions faq related to responsespectrum analysis. After an eigenfrequency step has been used to find the eigenvalues of a model, abaqusstandard automatically calculates the participation factor, the effective mass, and the composite modal damping for each mode so that these variables are available for use in. Fema 451b topic 3 notes slide 7 instructional material complementing fema 451, design examples sdof dynamics 3 7 observed response of linear sdof development of equilibrium equation30. If you square this value it will give you the effective mass for that mode, directionindependent.
How can i speed up the running time of my model with. Modes with relatively high effective masses can be readily excited by base excitation. The minimum number of modes to satisfy ubc code has been obtained. Understanding the mass participation factor engineer jau. Mass participation factor and its role in modal anlysis. The effective modal mass provides a method for judging the significance of a vibration mode. Example of how to use the mass participation factor in. Modal analysis with altair optistruct hypermesh some hints all components in the model must have material and properties assigneddefined.
Hi indeed the mass participation factors for linear displacements along u,v,w only, no rotation yet are awailable in 4. The first is to perform linear dynamic analysis of systems subject to dif. A new method for determining the modal participation factor. Abaqus implementation of extended finite element method. Analysis users manual keywords manual getting started manual. Abaqus users mass scaling is keie mass scaling and quasistatic analysis. The participation factor for mode in direction i, is a variable that indicates how strongly motion in the global, or direction or rigid body rotation about one of these axes is represented in the eigenvector of that mode. Abaqusstandard provides three eigenvalue extraction methods. The participation factors are tabulated in the output results or you can write off the current participation factors a load step at a time and access them via apdl. Priestley et al 1996, among other authors, confirm that a sum of all empf known as cumulative effective mass participation factor, cempf of 80% to 90% in any given response direction can be considered sufficient to capture the dominant dynamic response of the structure. Transient modal dynamic analysis gives the response of the model as a function of. Seismic vulnerability assessment of a historical church. Investigate the effects of applying an impulse to the.
Filling out the simple form below will allow you to talk with other members, save your favorite forums, and receive notification of forum posts, in addition to other membersonly benefits. We can also define a rigid body mass m r in a similar way to a generalized mass as but so md tm. Youve just decided to join thousands of other professionals in the free, noncommercial engtips technical forums. What are the importance of modal participation factor in. The seismic vulnerability of a historical basilica church located in italy is studied by means of limit analysis and nonlinear finite element fe analysis.
The results are verified by the nonlinear finite element method. Topic 6 structural dynamics iii analysis of elastic mdof systems. After an eigenfrequency step has been used to find the eigenvalues of a model, abaqus standard automatically calculates the participation factor, the effective mass, and the composite modal damping for each mode so that these variables are available for use in subsequent linear dynamic analysis. Abaqus implementation of extended finite element method using a level set representation for threedimensional fatigue crack growth and life predictions jianxu shi1, david chopp2, jim lua1, n. The modal participation factor matrix i for mode i is m. Applications of finite element stress analysis of heavy truck chassis. I presented the results that you can obtain using that software. And modeling techniques import restart recover automated mass scaling nonstructural mass adaptive remeshing tracer particles steadystate detection. Scale factor should be specified such that its product with responsespectrum values.
Jan, 2017 i presume that you have basic understanding of a modal analysis. Hi all, i am trying to perform frequency analysis in 2d for a beam with rectangle cross section. Topic 6 structural dynamics iii analysis of elastic mdof. Ghazaly 1, 1 mechanical engineering department, faculty of engineering, south valley university, qena83523, egypt. Export and reexport of the abaqus software and this documentation is subject to united. In abaqus manual it has been mentioned that the ratio of kinetic to internal energy should be less than 10% for an acceptable solution. Abaqus and this documentation may be used or reproduced only in accordance. A real structure of golden gate bridge have been considered. Make sure units are consistent and density is defined. But if the first six modes only contribute 60% mass participation, and above 12 th mode also if for mode the mass participation factor is higher should we check with compressor harmonics upto that or not. Till now we are not considering the mass participation factor for targeting the modes. Modes having a higher mass participation would be the most significant modes to be focused u.
The six possible rigid body motions are indicated by. Wong department of harbor and river engineering, taiwan ocean university presentation for msc taiwan users conference taipei, taiwan, dec. May 11, 20 priestley et al 1996, among other authors, confirm that a sum of all empf known as cumulative effective mass participation factor, cempf of 80% to 90% in any given response direction can be considered sufficient to capture the dominant dynamic response of the structure. Definition of modal participation factor typical modal equation. A new method for determining mpf has been proposed. Sukumar3, and ted belytschko4 1global engineering and. Xansys view topic xansys struct participation factors. Of civil engineering cbit, hyderabad, telangana, india abstract reinforced concrete rc has become one of the most important building materials and is widely used in. How can i view modal participation factor after carrying. Abaqus implementation of extended finite element method using. Mass diffusion transient and steadystate acoustics multiphysics thermoelectrical. Modal mass participation factor, which represents how strongly a specific mode contributes to the motion in a certain direction, is used to determine the appropriate number of modes to retain so that computational efficiency can be maximized.
Im doing an impact analysis in abaqus using dynamic explicit. Since the response spectrum procedure uses modal methods to define a models. Cantilever beam represented by a wire with a box section. Abaqus users mass scaling is keie hypermesh some hints all components in the model must have material and properties assigneddefined.
This should give you consistent modal participation factors. The paper focused on stress analysis of the heavy truck chassis using four finite element packages namely. In particular, the limit analysis and the nonlinear fe analysis provide an estimate of the load collapse. Eigenvalue extraction engineering school class web sites. How to calculate the relative contribution of each mode in. The participation factors are used to calculate the equivalent forcing function, and the equation of motion is solved for the relative quantities such as relative displacements, relative velocities, and relative accelerationsoutput variables u, v, and a, respectively.
I carried out modal analysis in ansys apdl for mode shape upto 100 modes since i wasnot able to obtain modal participation factor more than 90 % with lesser mode. Patran is an established pre and postprocessor for abaqus. A new method for determining the modal participation. Mass proportional damping in nonlinear timehistory. For enforced vibrations that originate from an abaqus or ansys file, only translational degrees. See faq5691083 for details on how to make best use of engtips. It has even been codified in many of the codes of record. Mode 1 20 frequency, participation factor and ratio 39. Some times when the velocity of impact is high, the job aborts and i reduce the time scaling factor 0. Structural dynamics of linear elastic singledegreeof.
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