BSI Newsletter - Issue #2, Fall 2004

Welcome to the Fall issue of the BSI Newsletter!

We regret to announce that the scheduled December release of FB-MultiPier will be postponed until next month due to the feedback from our pre-release users. We have decided that some of the issues mentioned were important and needed to be addressed. We take this opportuniity to thank all the people who have provided us with feedback about the program. Your comments and suggestions are always welcome and appreciated.

The articles "Tech Corner" and "Discussions with.." are open for input from all readers. Do you have a topic that you think should be discussed? Did you create a model that you feel contains notable information 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.

BSI will be closed from December 24-31 for the Christmas holidays. We are sorry for any inconvenience this may cause but we will be checking in periodically so please continue to call or email with any questions and we will respond as soon as possible.

The FB-MultiPier analysis program is a nonlinear finite element analysis program capable of analyzing multiple bridge pier structures interconnected by bridge spans. The soil behavior is modeled with a series of uncoupled springs along the depth of the pile. The full structure can be subjected to a full array of AASHTO load types in a static analysis, or time varying load functions in a dynamic analysis. Combined with the full bridge option, dynamic analysis modes have been added that will allow the user to have a more complete picture of the overall structure.

FB-MultiPier Screenshot The most notable features include:

Updated Graphical Interface
Multiple (99) Pier Modeling
- Unique Piers
- Pier Rotation
- Bridge Span Superstructure
- Two Rows of Bearing Pads
Dynamics Analysis
- Modal Analysis
- Time Step Integration
- Animated Results

The FB-MultiPier program will be an upgrade option for all current FB-Pier v3 license holders to update to the equivalent license of FB-MultiPier. FB-MultiPier will have several levels of licensing that will allow for different levels of use and pricing. License levels will include Single Pier (FB-Pier v3 equivalent), Single Pier with dynamic analysis, 3 Pier bridge with dynamics and a Full bridge (up to 99 Piers) with dynamics.

Find out more about the FB-MultiPier features and pricing here.

Pile foundations supporting bridge piers, offshore platforms, and marine structures are often required to resist static and/or dynamic loading. The static loading is mainly from the self weight of the structure whereas the dynamic loading can be applied from a variety of sources including wind, earthquakes, waves and ship impacts. The response of the pile foundations to live and dead loading is tied to geometry, stiffness and connectivity of overlying superstructure. For the analysis of the substructure, the piles are usually modeled as three-dimensional beam elements and the soil as a series of uncoupled "Winkler" springs at evenly spaced points along the pile as shown in Figure 1. The springs are characterized by nonlinear curves that simulate the soil response.

FB-MultiPier Screenshot The Py curves relate the lateral response of the soil (P) to the lateral displacement of the pile (y). Similarly the Tz curves relate the vertical response of the soil (T) to the vertical displacement of the pile (z) and the τθ curves relate the torsional response of the soil (τ) to the torsion in the pile (θ). These curves are derived from either theoretical or experimental tests and they depend on the soil properties, the pile geometry and also the nature of the applied loading. The curves can be found in published literature in either the static or the dynamic (cyclic) form depending on the nature of the applied loading. For instance, if the applied loading is static the curves will have a monotonically increasing magnitude with deformation. In the case of dynamic or cyclic loading, the static curves are degraded to account for the loss of the soil stiffness and strength under repetitive load application. In addition, the soil may exhibit liquefaction as well as potential loading on the substructure, i.e. flow liquefaction. This is a subject of discussion among engineers since there is no one way of defining the actual degradation of the curves.

Another issue of great importance is the behavior of each single pile within a group. When a pile is installed within a group then the soil response acting on the pile is affected by its position in comparison with the rest of the piles in the group. In order to address this problem and account for the "modified" response, a set of factors is utilized called P factors for the lateral response and Q factors for the axial response. These factors essentially scale (modify) the soil response of the individual pile depending on its position within the group.

FB-Pier and the successor program FB-Multipier models the lateral soil response with Py curves, the vertical response with Tz curves and the torsional response with τθ curves. It also models the bearing effects of the pile (tip) with a nonlinear spring called Qz which relates the vertical displacement (z) of the pile to the reaction of the soil (Q) at the pile tip.

The user needs only to input the soil profile and has the choice of selecting from a set of soil-structure models (PY, Tz, τθ, Qz - See User's Manual for details). FB-Pier (or FB-Multipier) creates these graphs based on the type of deep foundation (i.e. driven pile or cast insitu shaft, i.e. drilled shaft) information input by the user. The program also allows the user to specify his/her own Py, Tz, τθ, or Qz curves to describe soil-structure interaction . For the pile/shaft/piers, the user can choose from a library of sections (different shapes and material types, prestressed, composite etc) which are modeled with discrete elements. The discrete elements are capable of allowing material nonlinear behavior as well as PΔ effects. The group effects in FB-Pier (or FB-Multipier) are handled through the utilization of the PY multipliers (P factors described above) or the pile axial efficiency (Q factors). These factors are defined in the "GROUP" dialogue box in the SOIL menu.

The Holiday season is here once again!

BSI has had an exciting year with many new changes. Mark Williams, our friend and long time developer, moved on with his career after seven years of hard and productive work. We wish him the best in his new position. We were lucky enough to find a replacement in Petros Christou. Petros joined the Institute this year and worked closely with Mark to learn the details of the FB-Pier code.

We have been working on some interesting projects this year. In addition to the newly released FB-Deep program we have been working on the newest upgrade for the FB-Pier which is called FB-MultiPier. This includes work in modeling multiple pier structures and dynamic analysis. We hope that the dynamic analysis results will aid new innovative designs of bridge structures. BSI is fortunate to be able to interact and work closely with other people that are involved in the field. The latest example is an exciting full scale barge impact test on the St. George island bridge which was performed by faculty and students of the Civil & Coastal Engineering department at the University of FLorida in collaboration with the Florida DOT.

The Institute also weathered a turbulent hurricane season and were in the direct path of two hurricanes and were narrowly misssed by two more. We escaped with no real damages or losses but were forced to evacuate our building several times.

The challenges of each new year are what keep things interesting and we look forward to the new year as a another chance to continue to improve our products and serve our customers and the public by creating effective tools to create better and safer enstructures.

Happy Holidays and Best Wishes for a New Year from everyone at BSI!

Released: October 15, 2004 - Final Release - Technical Support Available

FB-Pier is 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. FB Pier 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.