In this issue's Technical Corner we will discuss some of the new features available with the release of FB-MultiPier v4.09. In our Discussions article, Michael Dividson talks about how FB-MultiPier transfers loading from the the columns to the pile cap.

The articles "Technical Corner" and "Discussions" are open for input from all readers. If you have a topic that you think should be discussed, let us know. Did you create a great model with features that you want to share? Everyone is welcome to submit articles for possible inclusion in subsequent issues. Please contact BSI at BSI@ce.ufl.edu with your ideas.

Graph Printing for Pile and Pier Results
Based on user feedback we have added new printing options for the Pile and Pier Plot Displays, which we hope will make this process easier and eliminate some of the problems reported in the past.

To use the new options, right click a plot window that you want to print and select the option 'Printable Graph'. The Printable Forces dialog (see below) will come up and show the graph selected and a table of the values used to generate it.

At the bottom of the dialog there are two buttons, 'Close' and 'Print'. As expected, the 'Close' button closes the dialog and returns the user back to the Plot Display. The 'Print' button will print the full dialog, including both the graph and table data, using the computer's print dialog to allow access to multiple print methods.

The table on the right of the dialog shows the force values and elevations for each point on the graph as well as the load case. Each column in the table lists an item (pile, column, cap) from the graph, showing the member name, number and the color used to display the item.

The two buttons above the table are options specific to the table. The 'Print' button will open the computer's print dialog and will send just the table to the select printer. The 'Save Data' button will convert the table data to a text (.txt) file that can be saved and reused as needed.

The graph to the left displays the graph as shown when this dialog was opened. The user can customize the graph, print or save the graph as a bitmap. The three buttons above the graph provide graph specific print and customization options.

Like the table button, the graph button 'Print' will open the computer's print dialog and will send just the table to the select printer. The 'Save As Bitmap' button will convert the graph as a bitmap and send to the computer default editor so that it can be saved and reused as needed.

The 'Customize' button lets the user change colors, fonts, and other display settings for the graph. These changes only affect the display in this dialog (changes not shown in FB-MultiPier window) and are meant to allow customized printouts. Note: Any changes to the plotted line colors do not change the color shown for that plot in the table.

If more than one curve is shown, the graph title will include the curve that contains the maximum force. If only one curve is shown, the graph title will simply include the number of the plotted member. To add more items to the graph, close the dialog and return to the Plot Display, select the new items desired and right click and select the 'Printable Graph' option again.

Pier and Pile Max and Min Forces Highlighting in the 3D Results View
New changes to the 3D results window include the ability to highlight elements where maximum and minimum results occur. Minimum and Maximum results for Displacements, Rotations, Shear, Moment, Axial, Soil (piles only) and Demand/Capacity Ratios can all be displayed using color-coded highlights.

Selecting the new radio button for 'Pier Max and Min Forces' or 'Pile Max and Min Forces' option under the 3D Results > Display Controls will open a sub-menu listing the available forces that can be displayed. Selecting any option will cause the elements where that force maximum and minimum results occur for the current load case to be highlighted in a specific color.

Included in the options is 'Allow Multiple Forces' which will open a new dialog that displays checkboxes for all available forces and the color codes that the highlighting will use. The 3D view will update with every selection and will remain even if you close the multiple selection dialog window. To revert back to a single highlighted force the 'Allow Multiple Forces' option should be unchecked.

Note: When selecting multiple forces the results sometimes occur in the same location. In this case the first highlight will hide other results under itself and all results may not be seen. Try turning off other options to see if a highlight is hidden if any selection does not seem to appear.

The issue of the load transfer path from the pier structure to the underlying columns and the way that it is handled by FB-MultiPier is very interesting and maybe not so obvious. FB-MultiPier is using the "CONNECTOR" elements which are rigid and generated internally by the program to address this issue. In fact, there is no direct node-to-node connection between the pier columns and the underlying pile cap.

Four beam elements, known as "connector (quad-pod)" elements, extend from each FB-MultiPier pier column bottom node to four adjacent nodes within the pile cap. The connector elements form the sole structural connection that links the pier column to the underlying pile cap. More specifically, the bottom node of a given pier column in FB-MultiPier is not structurally tied to the immediately underlying pile cap node.

The purpose of the connector elements is to more evenly distribute pier column loads to the pile cap, or alternatively stated, prevent unrealistic stress concentrations in the pile cap. It also effectively stiffens the base of the pier columns. More specifically, the use of the connector elements more accurately reflects the stiffness associated with the relatively large cross-sectional dimensions commonly found in pier columns of real-world bridge piers.

FB-MultiPier is the successor to FB-Pier. In addition to all the capabilities of FB-Pier the FB-MultiPier program allows for the modeling of a whole bridge that consists of multiple piers that are connected with bridge spans. In addition to the multiple load cases and the AASHTO coefficients that are available in FB-Pier, the new program is capable of performing dynamic analysis for the whole bridge. For more information about FB-MultiPier, click here.

The FB-Deep computer program is a Windows based program used to estimate the static axial capacity of drilled shafts and driven piles. The methodology is based upon Federal Highway Administration (FHWA) reports. FB-Deep guides the user through pile and shaft materials data, shape and dimensional inputs, soil properties, and boring log info. FB-Deep presents the data analysis in both clear graphical and text form. For more information about FB-Deep, click here.

This program has been replaced by FB-MultiPier and all sales or renewals will be directed to the FB-MultiPier program. FB-Pier is still available for download by valid licensed holders.

FB-Pier was designed for the analysis of bridge pier structures composed of nonlinear pier columns and cap supported on a linear pile cap and nonlinear piles/shafts with nonlinear soil. FB-Pier couples nonlinear structural finite element analysis with nonlinear static soil models for axial, lateral and torsional soil behavior to provide a robust system of analysis for coupled bridge pier structures and foundation systems. The program performs the generation of the finite element model internally given the geometric definition of the structure and foundation system as input graphically by the designer. For more information about FB-Pier, click here.

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