Composite Behavior
- jcallahan
- Tony Sun
Eriksson Wall allows two methods to analysis composite wall panels. These methods are the percent composite method and using a beam spring model.
Percent Composite
Inputs exist to set the percent composite value for stripping, transportation, erection, and in-place. The construction stage uses the same percent composite values are in-place. For each of these stages, the user can give a percent composite for deflections, stress calculations, and all strength checks.
For service checks, deflections and stresses, the percent composite is used by interpolating the section properties between fully composite and non-composite. The non-composite section used for all interpolation contains only the structural wythe and the non-structural wythe is not considered.
For strength checks the percent composite is used by interpolating between capacities by the defined percent composite. For example, for an 80% composite panel, the flexure capacity would be 80% of the way between the non-composite and fully composite flexure capacity. Because of this accurate parameters used in computing capacities are not known (such as neutral axis depth). The PM Diagram is also interpolated between the non-composite and fully composite case.
The following options are also selected by the user:
Header | Description |
|---|---|
Deflections | Percent composite value used for the structural analysis. |
Stresses | Percent composite value used for all stress computations. |
Strength | Percent compute used for ultimate strength. |
Options
Header | Description |
|---|---|
Solid zone behavior | This controls how solid zones are to be handled in the analysis. If set to partially composite, all the concrete in the solid zone is considered top-in-form as it is considered part of the secondary pour. If set to fully composite the section will not use any interpolation for section properties or strength checks. |
Structural wythe | Sets which wythe to use as the non-composite wythe when interpolating. The options are Top-in-Form, Bottom-in-Form, and Stiffer Wythe. If Stiffer Wythe is selected, whichever wythe has the larger EI value will be used. |
Loading datum | Sets which section should be used when determining the eccentricity of a given point load. Since the loads are input relative to a given face, the input eccentricity is only part of the total eccentricity. The section options are: Deflection Section, Stress Section, Ultimate Section, Composite Section, Non-Composite Section. |
Horizontal Shear Calculation
Header | Description |
|---|---|
Method | Partial Composite: Will treat all sections where the wythes are connected by concrete as partially composite. Fully Composite: Will treat all sections where the wythes are connected by concrete as fully composite. |
Limit zones to maximum length | Sets which wythe to use as the non-composite wythe when interpolating. The options are Top-in-Form, Bottom-in-Form, and Stiffer Wythe. If Stiffer Wythe is selected, whichever wythe has the larger EI value will be used. |
Beam Spring Model
For more information on the beam spring model theory see Beam Spring.
These inputs are only available when the Analysis Method input is set to Beam Spring. When beam spring is being used, up to two connector types can be defined. Each of these connectors must define a set of material properties and layout information.
Beam Spring Options
Header | Description |
|---|---|
Reaction Locations | This option controls which wythe the reactions are placed on. By default, they are placed on the interior wythe only. The user can also instruct the program to put the reactions on each wythe. Note that if both wythes are selected, and vertical restraint (such as the foundation connection) will form a couple and act as a moment restraint. Because of this it is important to design for the tension being put in at the bottom of the wall panel. |
Top / Bottom End Blocks | Gives an option to include the stiffness for top and bottom end blocks in the model or to ignore the stiffness. Including the stiffness of an end block typically restrains all slip in the panel and will introduce moments into the ends of the panel. |
Connector Properties
Header | Description |
|---|---|
Name | Name of the connector used only for identification purposes. |
Reduction Factor | Limit on the allowable limit at the defined limit state. This factor is applied to both the force and the slip to maintain the stiffness. For ultimate, the reduction factor is only applied to the portion of the curve after the yield point. |
Force | The allowable shear force for the given limit state. |
Slip | The allowable shear slip for the given yield point. |
Slip Limit | Defines whether at which point (defined by total effective slip) the program should flag an analysis error. A limit slip may be defined for both service and ultimate combinations. |
Import | Allows the ability to import material property data from disk. |
Export | Allows the ability to export material property data from disk. |
Applicability Check
Optional checks can be performed to ensure the connector being used is within the range of applicability based on the test data. These limits include setting hard and soft upper and lower limits for the following parameters. If a soft limit is exceeded, the program will give a warning. If a hard limit is exceeded, the program will give an error.
Header | Description |
|---|---|
Concrete Strength | Concrete strength of the top and bottom wythe |
Concrete Weight | Concrete weight of the top and bottom wythe |
Wythe Thickness | Thickness of the top and bottom wythe |
Insulation Thickness | Thickness of the insulation for the given section |
Phi Factors | Reduction factor for both yield and ultimate |
Connector Spacing | Maximum and minimum spacing of connector |
Connector Locations
The position of connectors plays an important role in the performance of the connector. Connectors placed in regions of little slip will not generate any shear force and thus, will not be effective in resisting slip. To facilitate the input of connector locations, two methods are available:
Simple Method
The simple method provides a simple input requiring the first-row location and spacings. The inputs are summarized below. The inputs using this method are assumed to be symmetric and will lay out from each end towards the center.
Header | Description |
|---|---|
First row location | The location, from each end, where the first row of connectors are placed. |
Typical quantity per row | The quantity of connectors in each row will be used as a multiplier on the total stiffness in the row. |
Row spacing | The spacing between each row. These will be placed from the first row at a uniform spacing until the entire panel is filled with connectors. |
Row quantity | An option to fill the entire member with shear connectors or add only a specific number of rows from each end. |
Additional connectors in 1st – 3rd row
| Options to include additional connectors in the rows near the end of the member. Since this is often the location of maximum slip, increased stiffness near the ends will assist in achieving composite members. |
Detailed Method
The detailed method provides a general input where each individual row may be positioned. Layout’s can be imported and exported to and from disk. Each row of connector locations has the following options.
Header | Description |
|---|---|
Rows | The number of rows in the input region. |
Columns | The number of columns in the input region. |
Transverse Method | Sets which two of the three available options you want to set: Left Distance, Width, or Right Distance. |
Left Distance | The distance from the left edge of the panel to the first column. |
Width | The distance from the first column to the last column. |
Right Distance | The distance from the right edge of the panel to the last column. |
Longitudinal Method | Sets which two of the three available options you want to set: Bottom Distance, Length, or Top Distance. |
Bottom Distance | The distance from the bottom of the panel to the first row. |
Length | The distance from the first row to the last row of connectors. |
Top Distance | The distance from the top edge of the panel to the last row. |
Stiffness Multipliers | A multiplier applied directly to the stiffness values of the connectors. These multipliers do not change limit slips, just scales the stiffness. Can be used to model solid zones in the concrete. |
Solid Zones
The beam spring model will always splint forces between the two wythes, even when a solid zone (such as an end block) is connecting them. The two wythes are connected by rigid links connecting the centroid of each wythe. Options exist to connect all of the solid zones, none of the solid zones, or only the end blocks. Typically by just having end blocks, the slip in the panel goes near zero rendering other connectors meaningless for shear transfer.