Bridge Design PS Design Tool Upgrades and Testing

June 06, 2022

The latest version of the PS Design Tool (PSDT) released with Version 7.2 of BrDR contains many new features that will be of interest to the user. The software was also tested in a unique way that exercised the strand pattern algorithm in a more vigorous fashion.

Some significant new features and capabilities of the PSDT were added for this release that make the tool more robust.

Some of the features/updates include:

• Girder system entry and girder line entry with additional design parameters and a diaphragm wizard
• Structure framing plan, typical section, and beam profile schematics Ū Prestress tee beam design and additional strand configurations
• The capability to save beam designs
• A feature to export from BrDR/BrD/BrR to the Design Tool
• Debonding of harped strand patterns
• Cut top strands
• Compute the area of steel required in the negative moment region for bridges made continuous for live load
• Iterate on the concrete strength
• User control for Continuous/Continuous-Simple modeling
• Revisions to the strand pattern algorithm including moving strands to the web so they can be harped
• Additional reporting capabilities including stability checks for transport, camber tables, and hold down force calculations
• Capability to run the PSDT from a command line interface

In addition to the new features, a new method of verifying and later regression testing the PS Design Tool was developed. This included automatically generating and running thousands of PS Design input files in a batch mode and plotting the results in a way that can detect relative anomalies in the design tool algorithm. Using a spreadsheet, more than 8,000 PSDT input files for PS I-girders and PS spread box beams were generated and subsequently run in a batch mode using the newly added command line interface feature (see Table 1).

The output data was gathered and the results for the prestressing force vs beam spacing were plotted for different span lengths (see Figure 1) to try to determine if there are any breaks in the algorithm. For the figure showing the harped strands, expected patterns were observed as the PS force increases as the beam spacing increases for each specific span length. Eventually, the beam spacing becomes too large and a design is not found (as expected). Gaps in the curves and spikes in the curves would indicate an anomaly that would need to be investigated.

This type of testing allows us to fully exercise the algorithm by providing “snapshot” views of hundreds of testing cases at once which allows for the quick identification of potential problems. For this version, input files were developed for I-beams and Box beams which will continue to be used for future regression testing of the PSDT. Additional input files for different beam types (T-beams, U-Beams) can be added for future testing as well.