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. How can i view modal participation factor after carrying. 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. 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. This factor is not available for rotary inertia elements in abaqus explicit. The modal mass participation ratio is widely used as the metric to determine the relative significance of modes in a modal response spectrum analysis. And modeling techniques import restart recover automated mass scaling nonstructural mass adaptive remeshing tracer particles steadystate detection. Youve just decided to join thousands of other professionals in the free, noncommercial engtips technical forums. Investigate the effects of applying an impulse to the. The first is to perform linear dynamic analysis of systems subject to dif. 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. 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. I presume that you have basic understanding of a modal analysis.
Mass participation factor and its role in modal anlysis. Jan, 2017 i presume that you have basic understanding of a modal analysis. Mode 1 20 frequency, participation factor and ratio 39. Modes with relatively high effective masses can be readily excited by base excitation. A new method for determining the modal participation factor. Export and reexport of the abaqus software and this documentation is subject to united. 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. 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. 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. Wong department of harbor and river engineering, taiwan ocean university presentation for msc taiwan users conference taipei, taiwan, dec. Sukumar3, and ted belytschko4 1global engineering and. Ghazaly 1, 1 mechanical engineering department, faculty of engineering, south valley university, qena83523, egypt. To provide six digits of numerical accuracy, abaqus standard sets each big mass equal to 10 6 times the total mass of the structure and each big rotary inertia equal to 10 6 times the total moment of inertia of the structure.
This page is devoted to frequently asked questions faq related to responsespectrum analysis. Abaqus users mass scaling is keie mass scaling and quasistatic analysis. Abaqus implementation of extended finite element method using. Certifies that this is the approved version of the following thesis. Coupled transverse vibration modeling of drillstrings. Xansys view topic xansys struct participation factors. The minimum number of modes to satisfy ubc code has been obtained. The ams eigensolver does not compute composite modal damping factors when. Applications of finite element stress analysis of heavy truck chassis. The paper focused on stress analysis of the heavy truck chassis using four finite element packages namely. Some times when the velocity of impact is high, the job aborts and i reduce the time scaling factor 0. Understanding the mass participation factor engineer jau. For example, asce 705 710 is at home, sorry, section 12.
I presented the results that you can obtain using that software. 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. 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. Topic 6 structural dynamics iii analysis of elastic mdof systems.
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. In particular, the limit analysis and the nonlinear fe analysis provide an estimate of the load collapse. Sukumar3, and ted belytschko4 1global engineering and materials, inc. We can also define a rigid body mass m r in a similar way to a generalized mass as but so md tm. When the responsespectrum curve is defined, acceleration is typically entered as a fraction of gravitational acceleration 9. Hi indeed the mass participation factors for linear displacements along u,v,w only, no rotation yet are awailable in 4. Hence, an artificial low frequency mode is introduced for every degree of freedom in a secondary base. A real structure of golden gate bridge have been considered. The six possible rigid body motions are indicated by. Variables associated with the natural modes of a model.
Analysis users manual keywords manual getting started manual. A new method for determining the modal participation. The ams eigensolver computes the generalized mass and the participation factor. Hi all, i am trying to perform frequency analysis in 2d for a beam with rectangle cross section. Cosmosm advanced modules 11 1 introduction introduction the advanced dynamic module, astar or post dynamic, has three principal functions. 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. Abaqusstandard provides three eigenvalue extraction methods. Topic 6 structural dynamics iii analysis of elastic mdof. Im doing an impact analysis in abaqus using dynamic explicit. 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. See faq5691083 for details on how to make best use of engtips.
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. How to calculate the relative contribution of each mode in. Eigenvalue extraction engineering school class web sites. Patran is an established pre and postprocessor for abaqus. Example of how to use the mass participation factor in. Make sure units are consistent and density is defined. How can i view modal participation factor after carrying out. The seismic vulnerability of a historical basilica church located in italy is studied by means of limit analysis and nonlinear finite element fe analysis.
Abaquscae is the preprocessor and abaqusviewer in the post processor. In abaqus manual it has been mentioned that the ratio of kinetic to internal energy should be less than 10% for an acceptable solution. Since the response spectrum procedure uses modal methods to define a models. Modes having a higher mass participation would be the most significant modes to be focused u. 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. The results are verified by the nonlinear finite element method. Five typical structures have been demonstrated to check the validity. The modal participation factor matrix i for mode i is m. This should give you consistent modal participation factors. If you square this value it will give you the effective mass for that mode, directionindependent. Definition of modal participation factor typical modal equation.
Abaqus and this documentation may be used or reproduced only in accordance. For enforced vibrations that originate from an abaqus or ansys file, only translational degrees. What are the importance of modal participation factor in. Seismic vulnerability assessment of a historical church. 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. Cantilever beam represented by a wire with a box section. Sep 06, 2012 till now we are not considering the mass participation factor for targeting the modes. 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.
Scale factor should be specified such that its product with responsespectrum values. Mass proportional damping in nonlinear timehistory. The rotational participation factors arent much use unless youre inputting rotational spectra. A new method for determining the modal participation factor in support motion problems using mscnastran msc95. 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. A new method for determining mpf has been proposed. How can i speed up the running time of my model with. Heat transfer and thermalstress analysis to support the. Weisser2 1daimlerchrysler d71059 sindelfingen, 2ballard power systems ag d 73230 kirchheimteck. 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.
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. Abaqus users mass scaling is keie hypermesh some hints all components in the model must have material and properties assigneddefined. Abaqus implementation of extended finite element method. Mass diffusion transient and steadystate acoustics multiphysics thermoelectrical. Modal analysis with altair optistruct hypermesh some hints all components in the model must have material and properties assigneddefined. It has even been codified in many of the codes of record. Abaqus standard chooses each big mass equal to 10 6 times the total. How can i speed up the running time of my model with abaqus. Mass includes all dead weight of structure may include some live load has units of forceacceleration internal force acceleration 1. Transient modal dynamic analysis gives the response of the model as a function of.
The effective modal mass provides a method for judging the significance of a vibration mode. See faq5691083 for details on how to make best use of. Henceforth, and in other abaqusstandard documentation, the term eigenvalue is used. 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. Responsespectrum analysis faq technical knowledge base. Structural dynamics of linear elastic singledegreeof.
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