Form: Define Frame/Wall Hinge Properties
Hinge properties are used to define nonlinear force-displacement or moment-rotation behavior that can be assigned to discrete locations along the length of frame (line) objects or to the mid-height of wall objects. These nonlinear hinges are used during static nonlinear analysis, fast nonlinear analysis (FNA) modal time history analysis, and nonlinear direct integration time history analysis. For all other types of analysis, the hinges are rigid and have no effect on the behavior of the member.
Note: It is important that frame and wall objects be designed, e.g. reinforcement should be defined for concrete frames and walls, prior to running a nonlinear analysis utilizing hinges.
Three kinds of hinge properties are available in ETABS:
Auto Hinge Properties.
Auto hinge properties are defined by the program. The program cannot fully define the auto properties until the section to which they apply has been identified. Thus, the auto property is assigned to a frame or wall object, and the resulting hinge property can then be reviewed.
User-Defined Hinge Properties.
User-defined hinge properties can be based on auto properties or they can be fully user defined.
Program Generated Hinge Properties.
The generated hinge properties are used in the analysis. They can be viewed, but they cannot be modified. Generated hinge properties have an automatic naming convention of LabelH#, where Label is the frame or wall object label, H stands for hinge, and # represents the hinge number. The program starts with hinge number 1 and increments the hinge number by one for each consecutive hinge applied to the frame or wall object. For example, if a frame object label is F23, the generated hinge property name for the second hinge applied to the frame object is F23H2.
The main reason for the differentiation between defined properties (in this context, defined means both auto and user-defined) and generated properties is that typically the hinge properties are section dependent. Thus it is necessary to define a different set of hinge properties for each frame or wall section type in the model. This could potentially mean that you would need to define a very large number of hinge properties. To simplify this process, the concept of generated properties is used in ETABS. When generated properties are used, the program combines its built-in criteria with the defined section properties for each object to generate the final hinge properties. The net effect of this is that you do significantly less work defining the hinge properties because you do not need to define every hinge.
The user assigns auto hinge properties and user-defined hinge properties to a frame or wall object. The program then automatically creates a new generated hinge property for every assigned hinge.
Define user-defined hinge properties as follows:
Click the Define menu > Section Properties > Frame/Wall Nonlinear Hinge command to access the Define Frame/Wall Hinge Properties form.
Choose or input parameters for the following areas.
Defined Hinge Props area. A list of hinge properties, including any previously defined auto or user-defined hinge properties, is displayed in this area. Check the Show Generated Props check box to include the generated hinge properties in this display list. Check the Show Hinge Details check box to display additional information about the hinges in the list (see Show Hinge Details check box write-up below).
Add New Property button. Click this button and the Default For Added Hinges form will display. Use that form to specify the type of default hinge definitions to be used as the basis of adding a new hinge definition. After selecting Steel, Concrete or User Defined, the Hinge Property Data form will display. Use that form to complete the definition of a new hinge property.
Add Copy of Property button.
Highlight a hinge property name in the Defined Hinge Props list box. Note that generated properties cannot be copied.
Click the Add Copy of Property button to display the Hinge Property Data form pre-loaded with the definition options of the selected hinge property.
Use that form to add a new definition based on the selected definition.
Modify/Show Property button.
Highlight the hinge property name to be modified in the Defined Hinge Props list box.
Click the Modify/Show Property button to display the Hinge Property Data form.
Use that form to make the necessary changes to the definition.
Note: Generated hinge properties can be viewed, but can not be modified.
Delete Property button.
Highlight the name of the hinge property to be deleted in the Defined Hinge Props list box.
Click the Delete Property button.
Note: If the highlighted hinge property is being used anywhere in the model, the Delete Property button will be grayed out and inactive. A hinge property can not be deleted until it has been removed from all objects. Remove a hinge by selecting the object(s) and deleting the assignment.
Show Hinge Details check box. When this check box is checked, the Defined Hinge Props area expands to a spreadsheet type area that has the following columns:
Name. The ID assigned to the hinge is displayed in this column.
Type. The type of hinge (e.g., Axial P, Shear V, Moment M and so on) is displayed in this column.
Behavior. This column identifies if the hinge is deformation or force controlled.
Generated. If Yes is displayed, the hinge is a generated hinge. If No is displayed, the hinge is user defined or auto.
From. If the hinge is a generated hinge (i.e., Yes appears in the Generated column), this column displays the ID of the hinge upon which the generated hinge is based. If the hinge definition is program defined, Auto displays in this column. If N.A. appears in this column, the hinge is a user-defined hinge that is based solely on the user's input.
Note: Make changes to any of these items by first highlighting the row of data to be changed. Then click the Modify/Show Property button to display the Hinge Property Data form and make the necessary adjustments. Note that generated properties cannot be modified.
Show Generated Props check box. By default, hinge properties that the program automatically generates at each hinge location are not listed in the Defined Hinge Prop area of the Define Frame/Wall Hinge Properties form. Check the Show Generated Props check box, and ETABS will display those properties in the {Defined, All} Hinge Props area along with any Auto hinge properties that have been assigned to the model.
Convert Auto to User Prop button. This button appears on the form when an Auto hinge property has been assigned to a frame or wall object(s) in the model and the Show Generated Props check box is checked. When this button is clicked, the program converts the Auto property hinge to a user-defined hinge property. After an Auto hinge property has been converted to a user-defined property, the resulting hinge property definition can be modified by clicking on it and then clicking the Modify/Show Property button to display the Hinge Property Data form.
References
ATC, 1996. Seismic Evaluation and Retrofit of Concrete Buildings, Volume 1, ATC-40 Report, Applied Technology Council, Redwood City, California.
FEMA, 1997. NEHRP Guidelines for the Seismic Rehabilitation of Buildings, Developed by the Building Seismic Safety Council for the Federal Emergency Management Agency (Report No. FEMA 273), Washington, D.C.
See Also