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Loads toolbar

Loads toolbar
1

Load group button

1. Load group button
Create a load group
 
A load group is composed of structural simple loads applied over a structural element and these loads are independent of the finite element mesh. That is, the element mesh can be modified without affecting the applied simple loads. This allows user to make mesh modifications and conduct mesh sensitivity studies without having to reapply loads each time. Simple loads are automatically transferred to the finite element model.
 
The structural element usually involves fewer entities than its associated finite element model. Therefore, selecting structural element entities and applying loads on them is much easier, especially with graphical picking.
 
2

Acceleration button

2. Acceleration button
Create an acceleration load
 
Specifies the linear acceleration of the structure in each of the global Cartesian (X,Y, and Z) axis directions. It is important to know that accelerations are always referred to the global Cartesian coordinates.
 
Applying a gravity load is equivalent to creating an acceleration in that direction. For example, an acceleration on negative Z direction simulates gravity acting in the negative Z direction.
 
 
 
Units are [L/S2].
 
3

Spectral button

3. Spectral button
Create a spectral load
 
The spectrum response capability allows the user to obtain the maximum response of a structure subjected to a known spectral base excitation. This is of particular importance in seismic analysis and random vibration studies.
 
A response spectrum input represents the maximum response of single-DOF systems subjected to a time-history loading function. It is a graph of response versus frequency, where the response can be displacement, velocity, acceleration, or force. Two types of response spectrum analysis are possible: single-point response spectrum and multi-point response spectrum.
 
The output of a response spectrum analysis is the maximum response of  the model against the input spectrum. While the maximum response of each mode is known, the relative phase of each mode is not. In order to account for this, various mode combination methods are used (rather than simply summing these maximum modal responses).
 
Entering a spectral load can be done by means of: user response spectrum, Eurocode 8, NCSE-02.
 
It is not only possible to choose  a percentage for damping in the properties bar but also picking a material type is available. In case of selecting a material, CivilFEM will apply the corresponding damping.
 
If the user activates the prestressed option, CivilFEM will consider the load case in the modal analysis. Prestressed option is very useful if structural loads or self weight are big enough to consider their effects.
 
 
Spectrum´s properties bars.
 
 
User response spectrum
 
Horizontal and vertical table provides the spectrum definition by point, representing time and acceleration.
The damping of the system is not only available to be chosen manually but also regarding the material damping.
Vertical direction determines the spectrum direction according to the coordinate system.
The mode extraction option lets the user choose among Number of modes or Frequency range:
 
Combination method options include CQC and SRSS with direction calculated using SRSS3 or Newmark. Besides, Newmark method needs to make use of both a primary direction combination factor and a secondary directions combination factor.
Prestressed option is advisable for the user to active when the weight of the structure may take part in the tensional state. Therefore, this would affect to the vibration frequency.
 
Eurocode 8 EN 1998-1:2004
 
Horizontal and vertical table provides the spectrum definition by point, representing time and acceleration.
The damping of the system is not only available to be chosen manually but also regarding the material damping.
CivilFEM allows to choose both the type of spectrum and soil according to the specified classes in Eurocode 8.
% ground acceleration is available to be modeled depending on situations.
Vertical direction determines the spectrum direction according to the coordinate system.
The mode extraction option lets the user choose among Number of modes or Frequency range:
 
Combination method options include CQC and SRSS with direction calculated using SRSS3 or Newmark. Besides, Newmark method needs to make use of both a primary direction combination factor and a secondary directions combination factor.
Prestressed option is advisable for the user to active when the weight of the structure may take part in the tensional state. Therefore, this would affect to the vibration frequency.
 
NCSE 2002
 
Horizontal and vertical table provides the spectrum definition by point, representing time and acceleration.
The damping of the system is not only available to be chosen manually but also regarding the material damping.
CivilFEM allows to choose the type of spectrum depending on situations.
Importance option let choose between normal or special in regard to evaluate the risk of exceeding the base acceleration during the life period of the structure.
NCSE norm coefficients: ab, ac, K and C; are modeled according to the structure.
Vertical direction determines the spectrum direction according to the coordinate system.
The mode extraction option lets the user choose among Number of modes or Frequency range:
 
Combination method options include CQC and SRSS with direction calculated using SRSS3 or Newmark. Besides, Newmark method needs to make use of both a primary direction combination factor and a secondary directions combination factor.
Prestressed option is advisable for the user to active when the weight of the structure may take part in the tensional state. Therefore, this would affect to the vibration frequency.
 
4

Prestress load button

4. Prestress load button
Create a prestressing load group.
 
This type of load group allows the user to define a set of tendons on: beams, shells or solid elements. The user has to define the finite elements on which tendons are going to be applied, so, for that purpose, at first it will be necessary to define the group of geometries that would define the tendons profile, besides the values of the prestressing forces and values in order to calculate the prestress losses.
 
Tendons may be Pre-tensioned or Post-tensioned. Prestress technique affects to the calculation of tendon losses.
 
Coordinate system of the prestressing load, defines the tendons.
 
In case of prestress load whether on shell or solid elements, both a path and a number of division must be defined so as to indicate to CivilFEM the location in which the tendon cuts as a result of being evaluated. On beam elements these tendons cutting are automatically defined with the nodes.
 
 
Tendons do not belong to a particular entity (nodes or elements) in the model. It is therefore needed to transfer loads of prestressing tendons to the model. The transfer of prestressing loads depends on the type of the model:
 
- For beam elements, CivilFEM will set nodal and tangential equivalent pressures, of the prestressing actions, in the nodes of each beam element. The anchorage forces will be added to nodes where the prestressing cable is fixed.
 
-Both for solid and shell elements the node algorithm will be applied. This node algorithm will take the 8 closest nodes to each cable calculation point and will set equivalent forces to the prestressing actions. The calculation points are chosen automatically according to the tendon cutting and the tendon geometry.
 
5

Boundary cond. group button

5. Boundary cond. group button
Create a boundary conditions group
 
The degrees of freedom (DOFs) that can be constrained in a structural analysis are translations (X, Y, Z) and rotations (X, Y, Z).
 
Boundary conditions groups are similar to load groups in the sense that they are applied over any structural element and not necessarily to an already existing point or node. If there is no attached node, the constraint is interpolated between the nearest group of nodes.
 
A Boundary condition group is formed by simple boundary conditions applied over a structural element. These constraints are independent of the finite element mesh. That is, the element mesh can be modified without affecting the applied boundary conditions. This allows the user to make mesh modifications and conduct mesh sensitivity studies without having to reapply boundary conditions each time. Simple boundary conditions are automatically transferred to the finite element model.
 
Boundary conditions are referred to the active coordinate system.
 
Some particularities may take place if we talk about BC in both transient and harmonic analysis.
 
On the one hand, for transient analysis tabular boundary conditions are defined (constrain vs time tables).
 
 
On the other hand, assigning BCs follows a different process in a harmonic analysis due to the fact that either harmonic or prestressing boundary conditions are available for selection.
 
 
Choosing harmonic or prestressing BCs depends on the results the user wants to obtain. That is, if a harmonic BC is considered in a certain location, the frequency parameter will be taken into account due to the variations in time.
 
Boundary conditions types will be both explained and specified in the "Boundary condition group toolbar" chapter.
 
 
6

Initial cond. seepage group button

6. Initial cond. seepage group button
Creates a initial seepage conditions group
 
This type of load group allows establishing a new initial seepage conditions, submitting the structural element, or any of them, to a specific initial condition. Due to be a seepage condition, this value will depend on seepage units.  Initial seepage conditions groups are similar to the seepage boundary conditions groups in the sense that they are applied over any structural element.
 
Seepage initial condition button will be available as long as a static structural or a seepage analysis are being carried out.
 
The properties bar menu is visualized ahead:
 
 
This condition will be significant, especially, in coupled analysis. This will be  more explained in the seepage initial condition contextual menu.
 
This condition is very useful in case the user would like to establish an initial condition of water level. Nevertheless seepage initial conditions would be only functional in case of taking place a Mohr coulomb, Cam clay or even a nonlinear elastic behavior.
 
7

Thermal boundary condition group

7. Thermal boundary condition group
Creates a thermal boundary conditions group.
 
Thermal boundary condition group button will be only available if a thermal analysis is being carried out.
 
 
There are two types of Boundary Conditions both in transient and static/steady state analysis: nodal temperatures and nodal/element heat fluxes. In this last mentioned ,nodal/element group, the temperature flux, the convective BCs and the radiation, may be included.
 
CivilFEM includes in the Boundary Conditions list, these which are defined ahead:
 
Nodal temperatures
 
  • Punctual temperature.
  • Temperature on curve.
  • Temperature on surface.
  • Temperature on volume.
 
Nodal/Element temperatures
 
  • Point flux.
  • Flux on curve (2D).
  • Flux on surface.
  • Flux on volume.
  • Film coefficient on surface.
     
This list of boundary conditions will be widely detailed in the Simple boundary condition group toolbar, inside the Thermal boundary condition chapter.
 
Prescribed nodal temperatures are constant with time unless a time dependent table is referenced. The same situation happens if the user requires to introduce a flux, this one would be constant with time unless a a time dependent table is referenced.
 
That is, table would have the appearance ahead for the heat transfer:
 
 
This dependent table is configured in the defined material (only if the analysis is a thermal one). For further information, consult the material toolbar menu.
 
Thermal analysis only needs the existence of thermal boundary conditions, that is, structural boundary conditions are no required, unless a structural analysis has to be carried out as well.
 
8

Initial cond. thermal group button

8. Initial cond. thermal group button
Creates a initial thermal conditions group
 
This type of load group allows establishing a new initial thermal conditions, submitting the structural element, or any of them, to a specific initial condition. Due to be a thermal condition, this value will depend on temperature units.  Initial thermal conditions groups are similar to the thermal boundary conditions groups in the sense that they are applied over any structural element.
 
Thermal initial condition button will be only available if a thermal analysis is being carried out.
 
The properties bar menu is visualized ahead:
 
 
This condition will be significant, especially, in coupled analysis. This will be  more explained in the thermal initial condition contextual menu.
 
9

Seepage boundary condition group

9. Seepage boundary condition group
Creates a seepage boundary conditions group.
 
Seepage boundary condition group button will be only available if a seepage analysis is being carried out.
 
 
There are two types of Boundary Conditions both in transient and static/steady state analysis: nodal total heads and nodal/element hydraulic fluxes.
 
CivilFEM includes in the Boundary Conditions list, these which are defined ahead:
 
Nodal temperatures
 
  • Punctual total head.
  • Total head on curve.
  • Total head on surface.
  • Total head on volume.
 
Nodal/Element temperatures
 
  • Punctual hydraulic flux.
  • Hydraulic flux on curve (2D).
  • Hydraulic flux on surface.
  • Hydraulic flux on volume.
     
This list of boundary conditions will be widely detailed in the Simple boundary condition group toolbar, inside the Seepage boundary condition chapter.
 
Prescribed nodal total heads are constant with time unless a time dependent table is referenced. The same situation happens if the user requires to introduce a hydraulic flux, this one would be constant with respect time unless a a time dependent table is referenced.
 
This dependent table is configured in the defined material (only if the analysis is a seepage one). For further information, consult the material toolbar menu.
 
Porous material is shape by the conditions ahead:
 
Being the Kh and the mv coefficients, the hydraulic conductivity and the coefficient of volume compressibility, respectively.
 
Seepage analysis only needs the existence of seepage boundary conditions, that is, structural boundary conditions are no required, unless a structural analysis has to be carried out as well.
 
10

Initial cond. group button

10. Initial cond. group button
Creates a initial conditions group
 
This type of load group allows establishing a group of initial conditions, submitting the structural element, or any of them, to a specific initial condition. This time, the condition or conditions to apply will be dependent on the velocity units.  Initial conditions groups are similar to load groups in the sense that they are applied over any structural element.
 
Initial condition button will be only available if a transient analysis is being carried out.
 
The properties bar menu is visualized ahead:
 
 

The contents of Loads toolbar

Load group contextual menu
Acceleration contextual menu
Spectral contextual menu
Prestress load contextual menu
Boundary condition group toolbar
Initial conditions group tools toolbar
Thermal initial conditions group tools toolbar
Seepage initial conditions group tools toolbar
Multiple selection contextual menu
Thermal boundary condition group toolbar
Seepage boundary conditions group tools toolbar