Fiber Division of Section |
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In order to carry out a nonlinear analysis using fiber elements, beam cross-sections are appropriately divided into fiber cells. Such fiber cells are assigned various nonlinear material properties representing stress-strain hysteresis models for concrete, steel, etc. For a reinforced concrete structure, cover concrete, core concrete, reinforcing steel, etc. can be assigned to the sections. |
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From the Main Menu select Properties > Inelastic Properties > Fiber Division of Section |
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Define the properties of section division to which a fiber model is applied.Name: Fiber model name Section: (Conventional) Section name to which fiber elements are applied
Fiber model name
Select a (conventional) section name to which fiber elements will be applied.
A maximum of 6 nonlinear concrete and steel material properties, which were previously defined for fiber elements, can be assigned to fiber cells.
Divide the section into cells, and assign nonlinear materials to the cells. Concrete cover and confined core can be separately defined. (Place and modify rebar on the Create Rebar tab.) On the Create Fiber tab, divide a new section and assign nonlinear fiber material properties or edit the previously divided fiber section using Editing Fibers. The general procedure for dividing a new section and assigning nonlinear fiber material properties is as follows:
In case the section has two division regions or more, repeat steps b ~ d. When it is necessary to modify the previously divided fiber section, use Editing Fibers. More details on this function will appear later on this page Draw the boundary line delineating the cover and core parts of concrete. Import Cover Thickness: Import the Cover Thickness of the section defined in the Design function. Offset Distance from Boundary: After selecting the section, if additional boundary needs to be defined, select a reference polygon, and enter a distance from the boundary. Click Add to create an offset polygon. The concrete inside the main rebar and the concrete outside the main rebar are characterized differently. This function is usually used to enter the boundary of the outside concrete. Besides that, it is used to create a number of additional boundaries. + values will create a boundary inside the section, and - values will create a boundary outside the section. Select the reference boundary on the diagram and the selected boundary turns red. Enter the offset distance and click Add to create a boundary. Use Undo and Redo to cancel or revive the action.
After selecting a shape, click Enter to define an object, which defines a region. Enter: A general shape is a polygon consisted of a number of points and boundaries. Among these, we select a boundary zone, which will be divided into fiber cells. Any other defined boundaries are also recognized as individual objects. Clear: Selected boundary is cancelled. A completely closed area is selected on preferential basis with reference to the selected boundary. Set the fiber model regions, which will be applicable to the cover concrete and core concrete. First, select the shape of the core or cover region, and click Enter to determine the region. Enter: The face of the region, which will be divided into fiber cells, will be selected. At this point, only the polygon regions composed of the selected boundaries in Selecting Object will be activated. The activated region for division is shaded. Clear: Cancel the selected region. Enter the number of section divisions for the defined region. Each divided cell becomes a fiber. The properties of the cover and core can be reflected into each fiber. Note Fiber cell division has direct relation to the analysis time, so it is cautioned. The number of divisions is not always directly proportional to the accuracy of analysis. A common rule of thumb is to use 100~200 cells, which guarantees sufficient accuracy. In midas Civil, a section can be divided into a maximum of 1000 cells. It is common to densely divide the outer part of the section in which maximum strain occurs and to sparsely divide the inner part of the section in order to satisfy the analysis speed as well as the accuracy. Division Type: The region selected in Setting Region can be divided in a rectangular or radial pattern. Rectangular: Division by rectangular pattern Number of Divisions: Number of divided cells Ny: Number of divided cells in the y-axis direction (Enter 2 or more.) Nz:Number of divided cells in the z-axis direction (Enter 2 or more.) Once the Number of Divisions is entered, fiber division status is previewed on the diagram. Radial: Division by circular or elliptical pattern Number of Divisions: Center Point (y,z):Enter the coordinates of the center.
Nt: Number of divisions in the circular direction Nr: Number of divisions in the radius direction Once the Number of Divisions is entered, fiber division status is previewed on the diagram. Material ID: Select a Fiber Material Property ID, which will be assigned to the divided cells. After the above inputs, click Divide and confirm that the cells that were assigned fiber material properties are divided as intended. Use Undo and Redo to cancel or revive the action. Edit the fiber cells already divided. First, select the cells to be modified. The selected cells turn red.
Specific rebars can be defined in the section. Rebars can be defined in three ways, Point, Liner and Circular. All the placed rebars are classified and tabulated by rebar designation, Number and total area. Type: Point Material ID: Select a steel material defined in Fiber Material Property. Center Point(y,z): Enter the location of the rebar. The coordinates can be directly entered, or the center point can be selected on the section diagram after clicking on the entry field. Area: Cross-sectional area of a single rebar, which can be selected from the rebar DB. Or the user may directly enter the area. Type: Linear Material ID: Select a steel material defined in Fiber Material Property. Starting Point(y,z): First rebar location on a line - the coordinates can be directly entered, or the point can be selected on the section diagram after clicking on the entry field. End Point(y,z): Last rebar location on the line - the coordinates can be directly entered, or the point can be selected on the section diagram after clicking on the entry field. Number of Rebars: Specify the number of rebars to be placed on the line. Area: Cross-sectional area of a single rebar, which can be selected from the rebar DB. Or the user may directly enter the area.
Type: Circular Material ID: Select a steel material defined in Fiber Material Property. Starting Point(y,z): First rebar location on a circle - the coordinates can be directly entered, or the point can be selected on the section diagram after clicking on the entry field. In order to place rebars accurately, Starting Point and Center of Arc must be lined up horizontally. For placement of rebars in an elliptical or arc pattern, line up Starting Point and Center of Arc horizontally and adjust Angle.. Center of Arc(y,z): Center of the circle on which rebars are placed - the coordinates can be directly entered, or the point can be selected on the section diagram after clicking on the entry field. In order to place rebars accurately, Center of Arc must be located horizontally to the left of Starting Point. Central Angle of Arc: Angle of circular placement of rebars. The default of 360o places rebars in a full circle. Use Angle less than 360o to place rebars in an arc pattern. Number of Rebars: Number of rebars in a circular placement Area: Cross-sectional area of a single rebar, which can be selected from the rebar DB. Or the user may directly enter the area. |
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