MEMBER GROUPS

This option allows the user to apply loading to Member group(s), see Section 9.3

9.5 PRESSURE

The Pressure loading options allow the user to define area loading by specifying the area of a plane to which the loading applies. Precede creates either member distributed loads or plate joint loads based on tributary area.

9.5.1 Simple

The Simple pressure load feature calculates member uniform distributed loading based on a uniform pressure and tributary areas. The rectangular area to be loaded is defined by selecting the four corner joints of the area. The plane formed by the four joints define the load plane such that the load plane X axis begins at the first joint and passes through the second joint selected. The load plane Y axis is perpendicular to the load plane X axis and passes through the third joint selected. The right hand rule is used to determine the load plane Z axis. The load area must be defined such that all members parallel to the line formed by joints A and B (load plane X axis) are continuous along the entire width of the load area.

After defining the load area, the load condition, load ID and pressure are specified on the Data line. Uniform distributed member loads are generated normal to the load plane for members within the load area that are parallel to the load plane X axis, provided that the member's joints are within the plane tolerance of 0.25.

9.5.2 Complex

The Complex pressure feature calculates member distributed loading based on a constant or varying pressure and tributary areas. The load plane is defined the first three joints selected such that the load plane X axis begins at the first joint and passes through the second joint selected. The load plane Y axis is perpendicular to the load plane X axis and passes through the third joint selected. The right hand rule is used to determine the load plane Z axis. Load areas may be rectangular, trapezoidal or triangular and are initially defined by the coordinates of the selected joints. Triangular areas are defined by selecting the same joint as joint three and four.

After selecting the joints to define the load plane and the initial load area, the Pressure Load on Members dialog appears.

The load condition, load ID label and out-of-plane tolerance are entered in the appropriate fields.

Note: Any member lying in the load plane within the tolerance specified may be loaded. The actual elevation of the member including the effects of offsets is considered.

The Members to Load frame options designate whether members parallel to the load plane X axis (Along Local X) or members parallel to either the load plane X or Y axes (Along Local X and Y) are to be loaded. The Constant pressure, pressure Varying along the load plane Y axis or Total load option may be selected in the Load Input type frame. For constant pressure, the pressure is specified in the Pressure at Y min. If members in both the load plane local X and Y axes are to be loaded, the percent load applied to members parallel to the load plane local X axis is specified in the Percent along local X field. The Total force option generates member distributed loads based on a constant pressure calculated from the total load input in the Total load field and the area. For pressure varying along the local Y axis, the pressure at the bottom of the area or

minimum local Y coordinate and the pressure at the top of the area or maximum local Y coordinate are specified. If members along both the local X and Y axes are to be loaded, the percent of the load applied to members parallel to the local X axis must be specified. The load direction, normal to the plane, along the global X axis, along the global Y axis or along the global Z axis is specified by selecting Normal, X, Y or Z, respectively, in the Load Direction combo box.

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Upon selecting the OK button, the load area coordinates based on the joints selected are displayed. The coordinates of the load area may be modified appropriately.

Members parallel to the load plane local X, and optionally members parallel to the local Y axis, that are located within the defined area and the defined plane and tolerance are loaded.

9.5.3 Plate Area

This option generates loads at corner joints of plates within the defined load area based on pressure load and the plate area. The rectangular load area is defined by selecting three joints that define the perimeter of the rectangle.

The load condition, load ID label and out-of-plane tolerance are entered in the appropriate fields.

Note: Any plate lying in the load plane within the tolerance specified is loaded. The actual elevation of the plate including the effects of offsets is considered.

The pressure may be input as constant or varying pressure. The load direction may be specified as normal to the plate, or in the direction of either the global X, Y or Z axes. Note: Normal plate pressure is applied normal to the plate itself not

normal to the load plane. Therefore, the orientation of the plate local coordinate system determines the direction of the applied load.

Pressure varying along one of the global coordinate systems may be applied by selecting the appropriate axis and specifying the pressure and the coordinate at which to apply the pressure.

Each plate is subdivided into triangular areas defined by two adjacent joints and the plate centroid. The load for each triangular area is calculated with each of the two joints getting half the load. Plates may be triangular or quadrilateral . Any area within the rectangular area defined by the 3 joints not covered by a plate, i.e. holes in the area, will not be considered for loading purposes.

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9.5.4 Plates

This option allows the user to select individual plates or plate ranges that a pressure load is to be applied. The pressure load is applied as joint loads at the corner joint defining the plate element. If specific plates are to loaded, the plates should be selected with the mouse.

The load condition, load ID label and the constant pressure are specified. The pressure may be designated as normal to the plate or in the direction of the global X, Y or Z axis. Note: Normal plate pressure is applied normal the plate. Therefore, the

orientation of the plate local coordinate system determines the direction of the applied load.

To include a range of plates without manually selecting each one, select a plate with the mouse and enter the additional plates in the Plate range field.

9.6 SKID

This feature generates member concentrated loads resulting from skid or beam mounted structures whose support beams are parallel to either the global X or Y axes. A

concentrated load is generated where a defined skid beam crosses a modeled beam element.

The load condition, load ID must be specified. Skid data including the direction of the skid beams, the global coordinates of the geometric center, length, height and number of skid beams are input. If the center of force is not located at the geometric center of the skid, the global coordinates of the center of force should be entered. The skid forces and moments in the global X, Y and Z directions are specified in the Force and Moments fields respectively.

Concentrated member loads are applied to members lying in the XY plane defined by the skid center Z coordinate and the out of plane tolerance, at the point intersected by a skid beam. Both ends of the member must lie within the specified tolerance of the defined XY plane including the effects of offsets.