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PGSuper™ Frequently Asked Questions
Q32 PGSuper is warning that "Screed Camber is greater than the camber at time of deck casting. The girder may end up with a sag". What does this mean?

PGSuper performs many design checks beyond a basic evaluation of stress and capacity for the LRFD Service and Strength limit states. One of these checks is an evaluation of the potential for a girder to end up with a net downward deflection, or sag.

This warning is issued when the lower bound camber for the minimum timing construction scenario is less than the expected deflection due to the wet deck and superimposed dead loads.

Please refer to the Girder Sag Warning in PGSuper (pdf, 185KB) white paper for additional information.

Q31 Why is the D40 value in the WSDOT Girder Schedule Report half the D40 value in the Details Report?

PGSuper predicts an upper bound value for camber. The details of this calculation are shown in the Details Report. Nearly all measured cambers fall below the predicted upper bound value. The upper bound value is the maximum camber that can be expected. The lower bound of camber has been shown to be 50% of the upper bound value.

WSDOT puts upper bound and lower bound camber values in its girder schedules. The upper bound value is based on slab casting at 120 days (D120). The lower bound value is based on slab casting at 40 days (D40). However, D40 is an upper bound for camber at 40 days. 50% of D40 is reported on the girder schedule to represent the lower bound of camber at 40 days. See WSDOT BDM 5.2.4C for additional information.

Q30 Why is the rating factor for OL1 and OL2 loading the same?
A30 This happens when the permit load rating is governed by the optional yield stress limit defined in MBE 6A. and the live load moment is not sufficient to crack the section. When the section does not crack, the moment in excess of the cracking moment is taken to be zero. Therefore the stress in the reinforcement nearest tension face due to cracking is also zero. The stress ratio is the ratio of the effective prestress and 90% of the yield stress of the reinforcement. This ratio is independent of the magnitude of the live load. Review the Load Rating Report, Load Rating Details, Rating Permit - Special/Limited Crossing Permit section for details of the calculation.

Q29 For the Slab Offset ("A" Dimension) check, I get a note that reads

There is a large variation in the slab haunch thickness. Check stirrup lengths to ensure they engage the deck at all locations.

What does this mean?

This note is given when the slab haunch thickness is greater in the mid-span of the girder than at the ends. When the slab haunch thickness varies significantly, stirrup lengths need to be adjusted. In the case of a crown vertical curve, the stirrups near the mid-span of the girder will be too short to engage the top mat of deck reinforcing unless they are lengthened.

When stirrups need to be adjusted, lengthen them by "Slab Offset" - "Profile Effect" - "Excess Camber" (note that "Profile Effect" is less than zero for sag curves)

Q28 Why is the live load stress omitted from the Bridge Site 3, Service I compression check for bottom of girder stresses?
A28 Moving loads have minimum and maxmum responses. These are generally seen in live load moment, shear, and stress envelopes. For simple span bridges, the minimum flexural response for live load is zero which occurs when the live load is just about to go onto, or has just come off of the structure.
The Service I compression stress check at the bottom of the girder compares the greatest compressive stress to an allowable value. Since live load causes tension in the bottom of the girder, the greatest compressive stress occurs when the live load response is minimized. That is, the greatest compression occurs when the live load is not on the structure.

Q27 I can input any value for concrete unit weight. Does PGSuper handle ligthweight concrete?

Prior to version 2.4, PGSuper did not have support for lightweight concrete. All concrete was treated as normal weight regardless of the unit weight.

PGSuper Version 2.4 added support for lightweight concrete. Girder and deck concrete can be defined as normal weight, sand lightweight, or all lightweight.

Q26 PGSuper lists three moments for the Strength limit states; Max, Min, and Deck. What are they?

The moments are the maximum limit state envelope used for positive moment and shear, the minimum limit state envelope used for shear, and the limit state moments used for negative moment analysis of the deck. These moments are designated Max, Min, and Deck respectively.

There are minimum and maximum moments because of the moving live load.

When analyzing the girder for positive moment and shear the demand on the girder is from all dead loads and live load. However, when analyzing the girder for negative moment, the loads that cause tension in the deck reinforcement are superimposed dead loads and live load.

The Min and Max moments include all dead loads and live load. The Deck moment includes only superimposed dead loads and live load.

Q25 I''m designing a long span girder and I just can''t get the Spacing Between Truck Supports for Hauling, Girder Support Configuration, and Maximum Girder Weight specification checks to pass. What can I do?

At design time it is difficult to know what actual equipment will be used to transport a girder. The Fail status simply means the design fails to satisfy the design criteria. In this case, the maximum allowable distance between supports, the maximum allowable leading overhang, and the maximum girder weight are highly dependent on the actual hauling equipment. The design criteria are based on rules of thumb.

If you find yourself in this situation, call your local fabricators and haulers and let them help you decide if it is practical to transport your girders

Q24 What is the difference between the Slab Offset ("A" Dimension) and Slab Haunch?

The slab offset and slab haunch are geometric parameters relating to the bridge deck. "A" dimension is a WSDOT term that is equivalent to Slab Offset.

The slab offset is the vertical distance from the top of slab to the top of girder measured at the intersection of the girder and bearing centerlines. The slab offset is measured at the beginning and ending of each girder. The actual slab offset is input by the user. PGSuper computes the required slab offset during analysis and the values are compared in the specification check.

Slab haunch dimension is the vertical distance from the bottom of the slab to the top of the girder anywhere along the girder. The slab haunch, also known as the slab pad, is the build up of concrete between the girder and the slab that accomodates geometric effects of the girder, roadway, and excess camber. The slab haunch depth is computed by PGSuper.

Q23 What is the difference between the analysis results for "Design LL+IM" and "LL+IM Design"?

The short answer is "Design LL+IM" is per lane and "LL+IM Design" is per girder.

The Design - LL+IM load case is the envelope of the individual design live loads. That is, it is the envelope of LRFD Design Truck + Lane, LRFD Design Tandem + Lane, etc. These are per lane results.

The LL+IM Design is the per girder live load results used in the design limit states. This is the Design - LL+IM envelope multiplied by the live load distribution factors.

The "Design" keyword means that these live load results are for the design limit states. That is, Service and Strength I limit states. If you select Loads | Live Loads... and select loading into the Permit (or Strength II) limit state, the results are prefixed with "Permit".

Because you can specify different dynamic load allowance factors for the design and permit live loads, there needs to be a way to distinguish the results. This is why you see "Design - LL+IM" and "Permit - LL+IM".

Q22 What is the difference between the user defined live load in the Vehicular Live Load Library and the static live load defined in the Girder View?

PGSuper has two methods of defining live load. The first method is to define a static concentrated or linearly varying load in the Girder View and designate it as LL+IM. The analysis results of this load are added to the LL+IM results for the moving vehicular loads (typically the HL-93 live load). The static live load is not a moving load and it is not adjusted for the shape of the influence line (pattern loading).

The loads defined in the Vehicular Live Load library are moving loads. The truck positions are varied along the structure to find the extreme force responses. The lane loads are patterned loaded based on the shape of the influence lines.

Q21 PGSuper doesn''t support my kind of traffic barrier. What do I do?

You can create your own traffic barrier shapes in the Traffic Barriers library. Even if the generic traffic barrier shape does not match your barrier, you can still create a shape that will work for your project.

PGSuper uses two key pieces of information from the traffic barrier definition; the weight of the barrier and the face of barrier location. The weight of the barrier is either computed based on the cross sectional area and the unit weight of the slab concrete, or it can be defined explicitly. The face of barrier location equates to the largest X value in the coordinate pairs. The face of barrier location is used in the determination of the roadway width and the de parameter for the live load distribution factor computations.

Q20 The bursting zone stirrup check for LRFD fails. What can I do about this?

This is a very difficult code requirement to satisfy, especially for larger girders. This problem can be remedied by either increasing capacity by adding more reinforcement or reducing demand by removing prestressing (not a very practical solution).

If you are designing to WSDOT BDM standards, you have some repreive. WSDOT allows the bursting zone check to fail so long as you provide sufficient reinforcement to resist the bursing force. The reinforcement cannot be larger than #5 bars and cannot be spaced closer than 2-1/4". See Design Memorandum 11-2006 for details.

Remember that "Fail" means that design fails to satisfy the project criteria and not structural failure. Engineering judgement can be used to dismiss the Fail status. Also note that AASHTO and NCHRP have an ongoing research project that will specificially address this issue.

Q19 How do I customize the logo on the cover of a PGSuper report?

You can replace the WSDOT and TxDOT logos on the cover of a PGSuper report by following these steps:

  1. Create an image file that is compatible with Internet Explorer
  2. Open the Registery Editor and go to HKEY_CURRENT_USER\Software\Washington State Department of Transportation\PGSuper\Settings
  3. Create a String value called ReportCoverImage and set the data to the fully qualified path for your image file.

Q18 I have an Internet connection but in the Configure PGSuper dialog, it says "The Internet is not currently available". What is going on? How do I get the published templates and libraries?

PGSuper is being blocked from accessing the Internet. You can work with your IT support team enable PGSuper to read and download files from FTP servers.

You can download the templates and library file from WSDOT''s FTP server using any ftp software. For simplicity, the procedure will be explained assuming you are using Internet Explorer.

  1. Start Internet Explorer and type ftp://ftp.wsdot.wa.gov/public/Bridge/Software/PGSuper in the address bar.
  2. Enter the subdirectory for the version of PGSuper that you are using. For example, if you are using Version 1.12, enter the Version_1.12 subdirectory
  3. Download the library file (.lbr) file you want. For example, download the AASHTO.lbr file for AASHTO standards.
  4. Download the contents of the templates folder that you want. For example, download the AASHTO_Templates folder.

To configure PGSuper to use the templates and library you just downloaded,

  1. Start PGSuper and select File | Program Settings
  2. Select the "Use and synchronize with libraries and templates on your local network..." option (This is the third option)
  3. Press the [...] button for the Master Library File input and select the library file you downloaded (AASHTO.lbr for this example)
  4. Press the [...] button for Workgroup Templates and select the templates folder you downloaded (AASHTO_Templates for this example).
  5. Press the OK button and PGSuper will be configured to use these templates and library file.

Q17 How do I define my own live load truck?
A17 Beginning with Version 2.1, you can define your own live load models in the Vehicular Live Load Library. Live load models can consist of a combination of lane load and a truck defined by axle spacing and axle weight.
Once the live load is defined in the library select Live Load from the Loads menu. In the Live Load dialog, select the loading to be used in the Design Limit States (Strength I, Service I, Service III, etc) and the Permit Limit States (Strength II). You can also specify the truck and lane impact factors for these limit state categories.

Q16 How does PGSuper compute the horizontal interface shear force?

The horizontal shear at the girder/slab interface is computed using the classical shear flow formula. Vui = (Vu * Q) / (I * b).

Starting with Version 2.0, you can select the method for computing shear flow. PGSuper will compute shear flow using the classical formula or the simplified formula given in the AASHTO LRFD Specifications.

Q15 The network in my office is locked down pretty tight and PGSuper is having difficulty checking for updates. Is there a way to disable this feature?
A15 There are two options that will prevent PGSuper from checking the Internet for updates. One option is to set the Update Frequency to Never. The other option is to put the templates and libraries on your local hard drive or network and use the local network option.

Q14 Does PGSuper support AASHTO girders?
A14 Yes, PGSuper supports any girder that are in the following family of shapes
  • I-Beam
  • Deck Bulb Tees
  • U-Beam
  • Voided Slab
  • Box Beam
  • Double-Tee (multi-web tees)

WSDOT publishes libraries and templates that are based on the AASHTO girders defined in the PCI Bridge Design Manual. To configure PGSuper to use these girder types:
  1. Close any open PGSuper projects
  2. Select File | Program Settings
  3. In the configuration dialog select the AASHTO Standard Girder option

PGSuper will download these templates and libraries.
Libraries, templates, and girder shapes for many DOT's can be found at PGSuper.com

Q13 PGSuper updated the templates and libraries from the Internet, but I''m sure that I didn''t get everything. How do I force PGSuper to do the update again?
A13 Start PGSuper, on the File Menu, select Program Settings. Press the OK button. PGSuper will download the library and template files again.

Q12 How do I save my PGSuper output?

A PGSuper report is nothing more than an HTML file. However, the report file links to many other files thus making it difficult to "save" a report.

The best way to save a report is to print it to a PDF printer. Free PDF printers are available from pdf995.com and PDF Creator

Q11 PGSuper tells me the Live Load Distribution Factors could not be calculated and a refined analysis is needed. What are my options for getting PGSuper to analyze my bridge?

You have three options as discussed below.

One option is modify the bridge''s configuration so that it satisfies the range of applicability requirements for simplified analysis per LRFD 4.6.2. Generally this is not a practical solution.

A more practical option is to perform a refined analysis to determine the live load distribution factors for your bridge and input them into the program. After performing a refined analysis in accordance with LRFD 4.6.3 select Loads | Live Load Distribution Factors... and input the appropriate values.

PGSuper offers you two other solutions. You may ignore the range of applicability requirements and have PGSuper compute the live load distribution factors using the equations from LRFD 4.6.2. Alternatively, PGSuper can use the lever rule method to compute the distribution factors. To accomplish this,

  1. Select Loads | Live Load Distribution Factors. This will bring up the Live Load Distribution Factors dialog.
  2. To have PGSuper ignore the range of applicability, select the first option in the dialog and then select either the "Ignore" option or "Use Lever Rule" from the drop down. The "Use Lever Rule" option will cause PGSuper to use the lever rule for any equation that is out of the range of applicability while using the equations for all that are within the range of applicability.
  3. Alternatively you can select the second option in the dialog, (Compute all Live Load Distribution Factors using the Lever Rule) in which case the Lever Rule will be used for all computations.

Q10 When I print a report some of the information is cut off the right side of the page. How do I make the report fit onto the paper?

PGSuper uses Internet Explorer to display and print reports. To make the report fit onto the paper, reduce the margins in Internet Explorer. To do this, start Internet Explorer, go to the file menu and select Page Setup. Set the left and right margins to 0.5" (you will have to experiment a bit to get margins that work well for your environment).

The next time you print a report from PGSuper, the new margins should be used.

Reporting formats have been greatly improved in PGSuper Version 2.1. It is recommended that the Bridge Geometry Report be printed with Landscape orientation. Also, Internet Explorer 7 and later have the ability to condense printed output so that it fits on a page. Upgrading to IE 7 will help with printing difficulties.

Q9 I just upgraded PGSuper from a previous version. When I open a PGSuper project I created with an earlier version of the software I get a message saying that I need to overwrite some library entries. What is going on here?
A9 PGSuper saves a copy of all the library entries a project is using in your PGSuper Project file. This makes the project file self-contained. This enables you to share your project files with people who do not have the same libraries as you. However, this presents a problem. User A can have a library entry called X and user B can also have a library entry called X, but with totally different data. When User B opens User A''s file, which library entry is PGSuper supposed to use? To address this problem, PGSuper first detects this situation and then gives you a choice for resolving it. You can either, update the library entry in your project file so it matches the library entry in the current master library or you can rename the library entry contained in the project file.

For more information on PGSuper libraries, see Chapter 8 of the User''s Guide and Chapter 2 of the Administrator''s Guide.

Q8 How do I model WSDOT End Type D connections with PGSuper?
A8 End Type D is used when the girder is integral with the bent. The geometry of this type of connection is unique to the geometry of the pier and thus cannot be captured in a re-usable library entry. To properly model End Type D connections you have to create a custom library entry.

To create a custom Connection library entry follow these steps:

  1. Select Library | Edit Entries to bring up the Library Editor window
  2. Expand the tree on the left hand side of the Library Editor window and select the Connections folder.
  3. Select Library | Add New Entry to create a new entry. When the entry is created it is in re-name mode. Simply type the name of the entry. For this example let''s use "My End Type D".
  4. Double click on the newly created library entry to activate its editing window.
  5. Enter the geometrical and loading data for your connection. Press the OK button when you are finished.
  6. Now you have to select this library entry. To do this, select Project | Edit Bridge from the main menu. Then select the Piers tab.
  7. On the Piers tab, select your connection (look for "My End Type D").

Q7 I am a WSDOT Bridge Engineer, how do I know if my installation of PGSuper is using the latest library and project templates?
A7 Start PGSuper, but don''t open a project. Select File | Program Settings. The Configure PGSuper dialog will be displayed.
  • Click on the Download and synchronize option for Libraries and Templates and select WSDOT as the publisher.
  • Select an update frequency
  • Press the OK button and the lastest templates and libraries will be downloaded to your computer.

Q6 The details report contains too much information, does PGSuper have a summary report with just the essential information?
A6 Yes, PGSuper does have a summary report. To create the summary report, select View | Reports. Using the drop down list on the Reporting Options dialog, select the Summary Report. Press the OK button to generate the report.

Q5 How do I model the intermediate spans of a continuous bridge?

Create a single span bridge that represents the intermediate span.  Use the centerline pier station when defining the locations of the piers.  If the connection types in the library don''t adequately represent your structure,  create you own in the connections library.

Version 2.0 supports multiple span bridges.

Q4 How do I create a connection entry in the Connections Library?
A4 The steps that follow can be applied to any library.
  1. Open the library view and select the Connections folder.
  2. Select Library | Add New Entry to create a new entry.
  3. Select the new entry and rename it using Library | Rename Entry
  4. Double click on the entry to edit its data.

If you are creating a connection for an intermediate pier,  and the girder does not carry the weight of the diaphragm,  enter very small dimensions for the End Diaphragm Dimensions

Q3 Which version of PGSuper do I have?
A3 Start PGSuper and select Help | About PGSuper.   In the About dialog you will find the version number and the build date for your copy of PGSuper

Q2 Why do you release PGSuper so often? Why don''t you just wait until it is completely done?
A2 The need for LRFD design tools is very high right now.  If you need to design prestress girders and don''t have an automated tool, you''ve got a lot of work to do.  Even though PGSuper isn''t completely finished, it has enough functionality that it can make life easier for you.  It is better to have a tool now that can do most of the work instead of waiting for a tool that can do all of the work.  We "Release Early - Release Often" so we can bring you the most up to date version of the program as it becomes available.

Q1 What are the different bridge site stages?
A1 PGSuper models the "life" of a precast girder in 4 distinct stages.  The first stage is in the casting yard.   This is called the Casting Yard Stage.  The next stage is Bridge Site Stage 1.   In this stage, the non-composite girder is at the bridge site, sitting on its bearing points, and it is carrying its selfweight plus the weight of the wet bridge deck.   The next stage is Bridge Site Stage 2. In this stage superimposed dead loads are applied to the composite girder.  The final stage is Bridge Site Stage 3. In this stage, live load is applied to the structure.

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