Loading

 

Loads are applied to an FE surface through the FE Editor under the Loading Tab. The FE surfaces do not interact with the MasterFrame area loads and so loads cannot be applied to an FE surface using the Area Loads.

 

The FE loads can be applied in a range of load types and also directions. The FE loading also includes Thermal loads, to allow for temperature changes to a structure to be defined. Loads are normally defined using the Global Coordinate system, but it is also possible to specify loads in the direction normal to the FE surface being considered. There are also options to easily specify perimeter loads.

 

Within the loading area, it is also possible to specify varying loads. Varying loads can be specified for area, line and patch loads. Varying Loads must be linearly varying.

 

Loads can be applied to an FE surface using nodal loadings. The nodes will be incorporated into the FE surface and thus will be included in the analysis. However, nodes which are not connected will be removed as part of the model clean up prior to the analysis. Therefore, to use nodal loads, the node must be connected by a member to another masterframe member or node, even if the member is a dummy member. However, for large points loads, where the stress concentration is important, applying nodal loads to the FE surface by using nodal loads has the advantage that the load is applied at a point. This differs for the use of nodal point loads, where the point load need not occur at a nodal position, in which case the nodal load is distributed to the area of the finite element to which it is applied, thus leading to a small distribution of the point stresses.

 

It is also possible to use the MasterFrame member loads to apply loading to an FE surface where the member will be an attached beam and so will act with the FE surface. In the case where the beam is not to be attached to the FE surface, then the member will act in a similar fashion as a MasterFrame Dummy member, with the reactions at the ends of the beams being transferred to the nodes at the ends of the beams. This means the bending in the beam will be ignored by the analysis. Therefore, if the loads are to be applied directly to the FE surface, it is best to not use the member loadings for beams which are not to be attached to the FE surface.

 

The FE loading can be applied as a full surface area load, patch loads over part of an FE surface, line loads, point loads and perimeter loads. For loads which do not occur over the full surface, the extent of the loads are defined using points on the FE surface. These points are called Load Points (LP). These loads points can be created in a number of ways. Load points can be displayed from within the FE Surfaces area of the software.

 

It is possible to create loadings which will be applied to other FE surfaces from within another FE surface. For example, if a slab is made up of several FE surfaces, it is possible to define loads for all these surfaces from within one of the FE surfaces. This, for example, it is possible to define a line load in one FE surface which extends beyond the boundary of that surface and onto one or more other surfaces. This feature can simplify the process of creating loads. However. care needs to be taken if surfaces are to be modified or deleted - deleting one surface will delete all loads defined in that FE surface, even if they occur outside that surface.

 

 

FE surface Loading

 

The FE surface loading editor can be accessed from MasterFrame by selecting Loads>FE Surface Loading. This will open the FE Surface pane on the right hand side of the screen on the Loading Tab. On first entering the Loading area, no loads are defined. The screen layout is shown below.

 

 

 

To add a load to an FE surface, first click on the  icon. The Load List will now indicate a load has been added to the Load List and the load type icons

 will now appear. The load types icons are:

 

 - area loads. Area loads are applied to the full FE surface.

- FE point loads. Point loads are positioned using Load Points

- FE line loads. Line loads can be arbitrary shapes and are positioned using Load Points.

- FE patch loads. Patch loads can be arbitrary shapes and are defined using Load Points. The first and last load point must be the same LP to form a close boundary.

 - FE perimeter loads. Perimeter loads can be applied to the outer boundary of an FE surface, or around an opening in an FE surface. Perimeter loads are defined using nodes rather than Load Points.

 

 

Area Loading

 

Area Loading is a load which is applied over the full extent of an FE surface. Area loads are input in the units kN/mē. Having selected to add an Area Load to the FE surface, the input area is as shown below.

 

 

 

Area loading can be assigned to a range of Load Groups and Load Numbers. The load groups match those found in Masterframe, with the exception of the Alternate load group, which is used to create alternating load patterns within the FE surfaces.

 

The Load Direction controls the axis the loading is applied in. For gravity loads, this will be the Global y-axis, but since the loads act downwards which the Global y-axis is positive upwards, then the load needs to be input as a negative value. The load is input as a kN/mē value. Area loads can also be specified to act normal to an FE surface, by selecting the N(Normal) direction. The normal direction is controlled by the local z-axis of the FE surface under consideration.

 

To input a varying area load, check the Varying Load checkbox. This will now add an additional input to the area loads. Varying loads are specified by inputting three values of load and the three nodes on the FE surface to which each value of load is to be assigned. The three load values are separated by commas, as are the three nodes. In the example below, the load is set to vary from 0 to 5 kN/mē, with the load taking the value zero at nodes N2 and N100, and value -5 at node 98.

 

 

 

Varying area loads must vary linearly.

 

 

Point Loads

 

Point Loads are specified in kN and are applied to an FE surface using Load Points. A single load value is input with the sign used to control the direction of the load in the selected axis. A point load can be applied at multiple points by inputting multiple Load Points, separated by commas. An example is shown below. Here a load of 10kN has been defined to act vertically downwards as a Dead Load, and has been added at Load Points 69, 70, 74 an 75. For details on creating Load Points, see the relevant section of this Chapter.

 

When inputting load points, the LP's can be input manually by typing the required values into the Load Point input, with the LP number separated by commas. Load Points can also be selected graphically. On selecting the Load Points input, then clicking on the  icons, this will open a small "Pick Points" pop-up window. Now, using the mouse pointer and left clicking with the mouse, the individual load points can be picked - each selected Load Point No. will appear in the small window. To finish, click on the  icon.

 

 

 

 

 

Line Loads

 

Line loads are specified in kN/m and are positioned using Load Points. The Load groups and Load number are set using the Load Group drop down options and the load direction is controls by specifying the Load Direction drop down. Line load can also be used to apply loads normal to the line itself, which represent a line load acting in the plane of the FE surface, using the M(In Plane Normal to line) option. The W (Y Global Full Length) option allows vertical loads to be applied even if the FE surface is itself oriented vertically. Finally, line loads can be used to define a moment acting over a line, where the rotation is about the line axis. This is achieved using the R(Moment about line axis) load direction.

 

Line load intensity can be linearly varied by inputting a start and finish value, separated by commas.

 

The position, shape and extent of the line load is controlled by the input load points. The first Load point in the list is the start point, while the last input load point is the end of the line load. The order load points are put in will control the intensity of the load where the line load is varying.

 

When inputting load points, the LP's can be input manually by typing the required values into the Load Point input, with the LP number separated by commas. Load Points can also be selected graphically. On selecting the Load Points input, then clicking on the  icons, this will open a small "Pick Points" pop-up window. Now, using the mouse pointer and left clicking with the mouse, the individual load points can be picked - each selected Load Point No. will appear in the small window. To finish, click on the  icon.

 

An example line load has been set up in the following screen capture. Line loads can be used to form closed or open boundaries. Line loads can also cross over each other. It is also possible to assign multiple line loads to coexist between common Load Points. Fro example, Dead and Live loads can be defined on the same lines using multiple line loads, each assigned as a separate line loads.

 

 

 

Patch Loads

 

Patch loads area area defined loads which are applied over part of the FE surface area. Patch loads are input using the units kN/mē. The area loads are then decomposed by the software into FE nodal loads on the finite elements to which the patch load is applied. Patch loads are defined positionally using Load Points. Hence patch loads can be arbitrary shapes, but their boundary must be a closed simple polygon. That is the boundary of the shape must be closed, planar and with non-intersecting edges.

 

The Load Direction controls the axis the patch loading is applied in. For gravity loads, this will be the Global y-axis, but since the loads act downwards which the Global y-axis is positive upwards, then the load needs to be input as a negative value. The load is input as a kN/mē value. Patch loads can also be specified to act normal to an FE surface, by selecting the N(Normal) direction. The normal direction is controlled by the local z-axis of the FE surface under consideration. The W (Y Global Full Length) option allows vertical loads to be applied even if the FE surface is itself oriented vertically.

 

An example of an live loading patch load is shown in the screen below. The Load Points are also displayed.

 

 

 

Patch loads can also be set to be variable by checking the Variable Load checkbox. Patch loads are defined by entering three load values and the three load points to which these input values apply. The load values and varying load points are input separated by commas. Variable loads will vary linearly between the input load points. The load intensity at each load point can be viewed graphically on screen by clicking on the  icon located at the bottom of the right hand pane.

 

An example of a varying patch load is shown below. The load varies from 0 kN/mē at Load Points 4 and 6, to -3.5kN/mē at load point 1. The load intensity at the other load points is indicated graphically.

 

 

 

Perimeter Loads

 

Perimeter loads are similar to line loads but are only applied at the edges of an FE surface. The edge can be internal, around an opening, or the external edge of the FE surface. Perimeter loads are entered in units of kN/m. The load group and direction are controlled by using the Load Group and Load Direction drop downs. Perimeter load values are given by a single input - it is not possible to define varying perimeter loads. Where a varying perimeter load is required, this is input as a line load.

 

The placement or position and extent of perimeter load is controlled by inputting node numbers. If no node numbers are input, then the perimeter load is taken to apply to the full FE surface external boundary. To apply the perimeter load to the perimeter of an opening, enter a single node on the opening boundary. To add a perimeter load over part of an edge, input the start and finish nodes. The perimeter load is applied in an anticlockwise direction.

 

 

Defining Load Points

 

Load Points are defined relative to the local surface coordinate system. Load Points act as a set of reference points for the positioning of Point Loads, Patch Loads and Line Loads. Selecting the Load Points Local Co-ords tab gives the following on screen layout.

 

 

 

 

Load Points can be input manually, by typing in the local x and y coordinates for each load point. Alternatively, Load Points can be automatically defined at the node positions by clicking on the  icon - clicking on    will automatically fill in the x and y coordinates for all the nodes which lie within the currently selected FE surface.

 

To assist in manually adding Load Points, the  icon will display the local surface coordinates of all nodes that line within the currently selected FE surface. Where Load Points have already been added, the  icon will display the local surface coordinates of the currently defined Load Points.

 

Load points can be be added and removed graphically to an FE surface. To activate the graphical input mode, click on the

 icon. This will add three additional options to the Load Points area, which is shown below.

 

 

 

 

To create a load point graphically, move the mouse pointer to the required location and then left click to select. The coordinates of the selected point will now appear in the Load Points table. Using the Add Only option will only add Load Points to the table. Using the Add/Delete option allows Load Points to be Added but also allows Load Points to be selected graphically to be removed from the list. The Add to Selected Row allows a line to be selected in the table and then coordinates to be selected graphically. This option can be used to overwrite previously defined Load Point coordinates.

 

It is possible to define load points outside of the boundary of the currently selected FE surface. This can be useful for defining load points to be used for different FE surfaces using the same local coordinate system, rather than having to convert to a new local system for each FE surface. However, Load Points can only be added in the plane of the current surface. For example, it is not possible to set up Load Points using an FE surface at one level for a surface at another level.

 

It is also possible to create Load Points graphically from within the load input area. Before adding any load points, select the Load Points input area and select the  icon. This will activate the snap tools and snap grid in the graphics window. Each required Load Point location can now be select graphically by positioning the mouse cursor and selecting the point by left clicking with the mouse. This will add a Load Point in the graphics window and add a Load Point number in the Pick Points pop-up window. Once the required Load Points have been created, clicking on the  icon will create the load at the input Load Points.

 

 

Editing Load Points

 

Load Points can be edited manually by selecting the Load Point entry in the table of coordinates and selecting which coordinate you wish to modify, and then over-typing the coordinate value. This allows individual load points to be modified.

 

The software also contains functionality which allows multiple load points to be edited. This can be done by selecting the  icon. This changes the options displayed on screen, as shown below.

 

 

 

 

The Load Points to be modified are selected graphically, using the mouse pointer. To display the current Load Points, select the  from the bottom of the right hand pane, then place the mouse pointer adjacent to a Load Point to be included in the Editing and select using the left mouse button. The Load Point number will appear in the list of Load Points to be edited.

 

Within the editing mode, groups of Load points can be rotated relative to the origin point of the FE surface, or translated in the x and/or y local axes by a specified distance. It is also possible to map particular nodes in the group onto particular nodes. The mapping option does not rescale the nodes, so where the distance between the Load Points does not match that of the  nodes, the first Load Point is mapped to the specified Node and the second is placed at the same distance from the first Load Point along a line from node N1 to node N2.

 

To save the changes, click on the  icon. To abandon the changes made, and revert back to the previous set-up, simply click on the  icon.

 

To exit the Editing Mode, click on the  icon.

 

 

Deleting Load Points

 

There are three options to delete Load Points.

 

 - Delete the currently selected Load Point

 - Delete All Load Points

 - Delete unused Load Points.

 

 

Where Load Points have been deleted, the  icon will cause the Load Points to be renumbered such that the numbering of the Load Points no longer has any gaps in the numbering.