Define Load Patterns

Form: Define Load Patterns

Use the Loads >  Load Patterns command, or on the Bridge Wizard select the Load Pattern Definitions item and click the Define/Show Load Pattern button to access the Define Load Patterns form and add, modify, or delete load patterns. Click there for more information about load patterns.  

The Define Load Patterns form also display when the Load Pattern Definitions item is selected and the Define/Show Load Patterns button is clicked on the Bridge Wizard. It also displays when the + (plus symbol) is clicked on any of the forms used to assign loads; see the topics in the Assign -  Area Loads, Frame Loads, Cable Loads, Tendon Loads, Joint Loads, Link/Support Loads and Solids Loads books of this Help.

Note: To calculate any response of the structure resulting from the load patterns, you must define and run load cases that specify how the load patterns are to be applied (e.g., statically, dynamically) and how the structure is to be analyzed (e.g., linearly, nonlinearly). The same load pattern can be applied differently in different load cases.

Tip: Every time a new load pattern is defined, the program automatically creates a corresponding linear static analysis case of the same name that applies the load. For a new model, the program creates a default load case called DEAD that applies the self weight of the structure. The corresponding linear static analysis case is also called DEAD.

  1. Click the Loads > Load Patterns command, or on the Bridge Wizard highlight the Load Cases item and click the Define/Show Loads button, to access the Define Load Patterns form. The form has the following edit boxes and drop-down lists.

Use the buttons in the Click To area of the form to complete the actions described below:

    1. Highlight the existing load pattern in the Load Patterns area. Note that the data associated with that load pattern appears in the edit boxes and drop-down lists at the top of the Load Patterns area.

    2. Modify any of the data in the Load Patterns area for the load pattern.

    3. Click the Modify Load Pattern button.

Note:  If nothing happens when the  Modify Load Pattern button is clicked, the load pattern is an automatic load pattern. As described in the Note below, highlight the load pattern and the click the Modify Lateral Load Pattern button.

If a new pattern is being defined with a load Type of Quake, Wave  or Wind and a code (i.e., automatic pattern) has been selected in the Auto Lateral Load Pattern drop-down list, first click the Add New Load Pattern button, then click the Modify Lateral Load Pattern button to access a form specific to wave,  wind or seismic loading. Use the form to specify parameters consistent with the code selected  in the Auto Lateral Load Pattern drop-down list. For example, if the load type is Quake and NEHRP 97 is selected in the Auto Lateral Load Pattern drop-down list, the form that appears is the NEHRP 97 Seismic Loading form. The options available on that form relate to code requirements. Thus, fill in parameters on the form as appropriate. Then click the OK button to complete the operation and return to the Define Load Patterns form.

Note: After a code specific pattern has been defined as described here, highlight it in the list of patterns and click the Modify Lateral Load Pattern button to redisplay the form if any additional changes are needed.

If a new pattern is being defined with a Type of Bridge Live, first click the Add New Load Pattern button to specify the load pattern, then highlight that pattern and click the Modify Bridge Live Load button to access the Multi Step Bridge Live Load Pattern Generation form. Use that form to refine the lane loading for a moving load analysis. Note that a bridge layout line, a lane(s) and a vehicle(s) must be defined before the bridge live load can be defined.

Note that when a static load pattern is deleted, all of the loads that have been assigned to the model as a part of that static load pattern also are deleted.

After a load pattern has been defined, assign loads to the objects as part of that load pattern by selecting the objects to be loaded and using the appropriate command from the Assign menu.