PGSuper Tutorials. What s new in PGSuper Version 2.7

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1 PGSuper Tutorials from BridgeSight Software What s new in PGSuper Version 2.7 BridgeSight Inc. P.O. Box Venice Drive South Lake Tahoe, CA

2 Title PGSuper Tutorial What s new in PGSuper Version 2.7 Publication No. BS Abstract This document provides an overview of the new features in PGSuper Version 2.7. Notes Author Staff BridgeSight Software Sponsor BridgeSight Inc P.O. Box South Lake Tahoe, CA Specification AASHTO LRFD Bridge Design Specifications PGSuper Version 2.7 Original Publication Date 09/05/2012 Date of Latest Revision Version 1.0 Notice of Copyright Copyright 2012 BridgeSight Inc. All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means (electronic, mechanical, photocopied, recorded, or otherwise), without prior written permission from BridgeSight Inc.

3 Disclaimer This BridgeSight PGSuper Tutorial is provided complements of BridgeSight Inc.. BridgeSight Inc. asserts a copyright in this work. BridgeSight Inc. retains the exclusive ownership of this copy of the PGSuper Tutorial. This document is provided AS IS without any warranty, express or implied by anyone using, distributing, copying or otherwise possessing this document. The entire risk as to the use, results and performance of this document is assumed by you. BridgeSight Inc. does not warrant, guarantee, or make any representations regarding the use of, merchantability or fitness for a particular use of the product. Should this document prove defective, you assume the entire cost of all necessary servicing, repair or correction. Further, BridgeSight Inc. does not warrant, guarantee, or make any representations regarding the use of, or the results of the use of this document in terms of correctness, accuracy, reliability, currentness, or otherwise and has no obligation to correct errors, make changes, support or distribute updates; and you rely on this document solely at your own risk. BridgeSight Inc. will not be liable for any damages, service, repair, correction, loss of profit, lost savings, or any other incidental, consequential, or special damages of any nature whatsoever resulting from the use or inability to use this product including any claims, suits or causes of action involving claims of infringement of copyrights, patents, trademarks, trade secrets, or unfair competition. The Licensee indemnifies and holds harmless BridgeSight Inc., its officials, employees, and contributors for any injury to the person or property of third parties arising out of the use of or any defect in this document. BridgeSight Software retains all rights not expressly granted. Nothing in this agreement constitutes a waiver of BridgeSight Inc. s rights under United States copyright laws or any other Federal or State law.

4 Introduction The Washington, Texas and Kansas Departments of Transportation released PGSuper Version 2.7 in September This software has several new features and enhancements including: Direct Selection Strand Input Bridge View Span Selector Improved Girder Design New Prestress Loss Options Improved modeling of sidewalks and barriers Accounting for crack spacing in shear capacity calculations Improved Reporting of Reactions The most significant change to the PGSuper project is the addition of the Kansas Department of Transportation (KDOT) as a development partner. After evaluation of other offerings, KDOT decided the most economical and feasible approach was to join the PGSuper collaboration with WSDOT and TxDOT. BridgeSight Inc. entered into a software development contract with KDOT in November The result will be new capabilities that benefit all PGSuper users and KDOT will have a precastprestressed girder design solution that will seamlessly integrated into their design process at a fraction of the cost of developing software from scratch. Direct Selection Strand Input Contractor-submitted design alternatives are common with precast-prestressed girders. KDOT needed a method to directly specifying the strand grid positions containing strands to evaluate alternative design submittals. Under contract with BridgeSight, KDOT funded a new Direct Selection Strand Input feature. With this new feature, engineers are presented with a graphical representation of the girder cross section showing all the possible locations for prestressing strands as defined in the girder library. This removes the requirements that strands must be added or removed using the strand sequence defined in the Girder Library. Now you can fill strand locations in any order you want! 1

5 Figure 1 Strand Selection Window Strands are added or removed by clicking on the strand positions in the Strand Selection window. A grid is also provided for selecting individual strands and defining debonded and extended strands. To enable Direct Selection Strand Input: 1) Select a girder to edit and open the Girder Details window. (This is most easily done by double clicking on the girder in the Bridge View). 2

6 2) On the Strands tab, select the Direct Selection of Strand Locations option 3) Press the Select Strands button to open the Strand Selection window 4) In the Strand Selection window, select the strand positions that will contain strands. This can be done by clicking on the graphic with your mouse or editing data in the grid. Bridge View Span Selector PGSuper has a highly interactive user interface. But in previous versions, when long bridges are modeled, the bridge plan view became difficult to read and interact with. Developers at WSDOT addressed this issue by adding a span selector to the Bridge View. This selector is used to select a range of spans to display. 3

7 Figure 2 Span Selector The new span selector allows you to view and interact with a portion of your bridge. Spans of a 15 span bridge are displayed for the bridge shown in Figure 2. Improved Girder Design PGSuper s Girder Designer has always had an automated shear design feature, but previous versions lacked in capability. TxDOT contracted with BridgeSight to make improvements to the shear design capabilities. Now, when designing for shear, the Girder Designer will determine the reinforcing requirements for: Primary transverse reinforcement (stirrups) Longitudinal reinforcement for shear Bursting and confinement reinforcement and, Horizontal interface shear. The Girder Designer supports two approaches to shear design. The Girder Designer can start with a predefined reinforcement layout and adjust the zone lengths, bar sizes, and bar spacing or it can start with a clean slate. There are trade-offs to both approaches. Several transportation agencies have standard stirrup configuration. There is an economy of scale and repetition by using the same stirrup configuration every time. The stirrups are detailed on standard plans and rarely need to be modified. When the Girder Designer is instructed to start with the current stirrup layout it first checks to see if the current shear reinforcement is adequate. If the Girder Designer finds that the stirrups do not satisfy the requirements defined in the Project Criteria they are adjusted, otherwise no changes are made. 4

8 When starting with a clean slate, the Girder Designer determines the reinforcement necessary to satisfy the requirements of the Project Criteria. The consequence is that the shear reinforcement is unique for each bridge and it must be detailed in the bridge plans. Non-symmetrical stirrup layouts are also supported. To design your girders for flexure and shear: 1) Select Project Design Girder to begin the automated design process. Select the flexure and shear design options in the Girder Designer window. 2) At the successful completion of the design process you will be presented with a proposed design. For the example shown, the standard stirrup configuration was adequate so nothing was changed.. 5

9 3) Press the Accept the Design button to replace the current input with the parameters determined by the Girder Designer. Stirrup design and detailing is very complex. Different agencies typically have their own stirrup layout and detailing rules. The new stirrup design algorithm solves this problem by putting the decision-making power into your hands. Associated with each girder are shear design preferences which control the outcome of the design process. These preferences guide the Girder Designer which stirrup size and spacing to use and how often to create new stirrup zones. These preferences are defined on the Shear Design tab of a Girder Library entry as shown below. Figure 3 Shear Design Preferences New Prestress Loss Options The PGSuper development team strives to make our software as complete and thorough as possible. Feedback from the PGSuper user community told us that small modifications could be made to the prestress loss calculations. The engineers at WSDOT took the lead and added new options for 6

10 Copyright 2012, BridgeSight Inc. All Rights Reserved computing prestress losses due to strand relaxation as well as controlling the computation of elastic gains and losses. Loss due to Strand Relaxation LRFD c provides three methods of computing prestress loss due to strand relaxation. All of these methods have been incorporated into PGSuper. The relaxat relaxation ion loss method is selected on the Losses tab of the Project Criteria library entry as shown below. Figure 4 Relaxation Loss Methods Elastic Gain When the LRFD Bridge Design Specifications updated the method of computing prestress losses in 2005, the concept of elastic gain was introduced. The original equations for predicting time dependent prestress losses due to concrete creep and shrinkage were based onn a stress analysis using transformed section properties. In an attempt to keep the specifications easy to understand, the AASHTO T committee modified the equations to use gross section properties. Elastic gains and losses were added to compensate for the he difference between transformed med and gross section property analysis. Many transportation agencies have policies that limit the magnitude of the elastic gains and losses that can be used in design. Th These policies can now be modeled in PGSuper. A new section titled Elastic Gains can be found on the Losses tab of the Project Criteria library entry. For the various loading components you can define the amount of load to be considered when computing ing elastic gains and losses. The values range between 0% (no elastic gain/loss due to this load) and 100%. Figure 5 Elastic Gain/Loss data 7

11 Elastic gains and losses are the change in stress in the prestressing strands due to an externally applied load and are computed as: = Where, = The change in stress in the prestressing strand (the elastic gain/loss) = A coefficient between 0.0 and 1.0 that controls the amount of elastic gain/loss that should be taken into account = Modulus of elasticity of prestressing strand = Modulus of elasticity of concrete = Moment due to externally applied load = Location of the prestressing strand relative to the centroid of the girder section = Moment of inertia The coefficient is derived from the data in the Project Criteria library as mentioned above. The application of elastic gains to the effective prestress is fairly straight forward for all the loads except for slab shrinkage. The elastic gain due to slab shrinkage must be accompanied by a corresponding change in girder stresses (there is no free lunch). The elastic gain due to slab shrinkage is computed as defined in LRFD d with a modification to LRFD Equation d-2. The modified equation is = 1+0.7, 1 The stress at the top and bottom of the girder due to slab shrinkage is computed using this modified equation with! and " substituted for # $% & %. The stress due to slab shrinkage is included in the Service I, Service III, and Fatigue I limit state stresses. The PCI Bridge Design Manual provides an excellent discussion on this topic if you would like more information. 8

12 Copyright 2012, BridgeSight Inc. All Rights Reserved Improved Modeling of Sidewalks and Barriers Previous versions of PGSuper hadd a very simple model for distributing barrier and sidewalk dead loads to girders that works well for narrow sidewalks and tightly spaced girders. TxDOT recognized this deficiency and funded a complete re-working re of the load distribution model. The distribution of barriers and sidewalks is now more rational and applicable to a wide variety of bridge configuration. Distribution of Barrier and Sidewalk Dead Loads In previous versions of PGSuper, the dead load of barriers and sidewalks were distributed to N exterior girders, mating surfaces, or webs.. This doesn t make sense in situations where an interior barrier is used to separate a wide sidewalk from the travelling lanes, lanes, or when the sidewalk is directly supported by more than N girders, mating surfaces or webs. The dead ead load of exterior and interior barriers is distributed as follows: Distribute the weight of the barrier evenly to the N nearest girders, mating surfaces, or webs (GMSW s). Nearest distance is measured from the C.G. of the barrier in a bridge cross section sect taken at mid-span. span. For cases when the weight of a barrier can be distributed to either of two GMSW s that are equal distance left and right of the barrier C.G., and these GMSW s are furthest from the barrier, the load will be distributed to the exterio exterior-most most GMSW. If the span contains 2N or fewer GMSW s, the railing load will be distributed evenly to all GMSW s. Sidewalk and pedestrian edestrian loads are distributed using a similar method and use the same N value as barriers. However, if the sidewalk is wider than th N GMSW s; the load will be distributed to all GMSW s lying directly beneath the sidewalk. Hence, the definition is a follows: Distribute the sidewalk weight and pedestrian live load evenly to the greater of: all girders, mating surfaces, or webs (GMSW s) (GMSW s) lying directly under the sidewalk; or the N nearest GMSW s measured from centerline sidewalk using a bridge cross section taken at mid-span. mid For cases when the sidewalk weight can be distributed to either of two GMSW s that are equal distance left and right ght of C.L. sidewalk, and these GMSW s are furthest from the C.L. sidewalk, the load will be distributed to the exterior exterior-most most GMSW. If the span contains 2N or fewer GMSW s, the load will be distributed evenly to all GMSW s. A new section has been added to the Loading Details chapter of the Details Report that lists the fraction of the total barrier and sidewalk dead load that is applied to a girder. Figure 6 Load Distribution Data 9

13 Pedestrian Live Load Version 2.7 of PGSuper gives you more control of how the pedestrian live load is modeled. The pedestrian live load can now be independently controlled for the limit states relating to Design, Fatigue, and Permit loading situations. The pedestrian live load can be omitted, applied concurrently with the vehicular live load, or enveloped with the vehicular live load. The pedestrian live load is distributed to the same girders, webs, or mating surfaces as the sidewalk dead load. To specify how pedestrian live load is to be modeled: 1) Select Loads Live Loads to open the Design Live Loads window. 2) When sidewalks are modeled in the structure, pedestrian live loads are activated using these options. For the Design, Fatigue, and Permit limit states, select the method of applying pedestrian live load. Accounting for Crack Spacing in Shear Capacity Calculations Previous versions of PGSuper assumed that the minimum amount transverse reinforcement requirement specified in LRFD was always satisfied. It was recognized that this assumption was not always valid, so PGSuper now determines if the minimum amount of transverse reinforcement is provided and performs the shear capacity calculations accordingly. When shear reinforcement is not required, but it is provided, and the amount provided is less than the minimum amount specified in LRFD , the β factor is computed with LRFD Equation when the general method is used and with LRFD Equation B5.2-2 when the Appendix B General Procedure with Tables method is used. These equations take crack spacing into account. 10

14 Copyright 2012, BridgeSight Inc. All Rights Reserved Improved Reporting of Reactions Previous ous versions of PGSuper report reported only the total reaction at piers and abutments. This was fine for pier/foundation design, but inadequate for designing bearings at intermediate piers. When a bridge has simple span girders framing into both sides of an intermediate intermediate pier, as is typically done in Texas, the girder reactions on each side of the pier are needed to design the bearing pads. BridgeSight, working under contract with TxDOT, improved the reporting of reactions. PGSuper now reports girder bearing reactions and total girder line reactions reactions. A girder bearing reaction is the reaction for loads applied directly to a simply supported girder. For structures that are made continuous for superimposed dead and live loads, girder bearing reactions include loads loads applied to the girder up to the time of continuity. A total girder line reaction is simply the sum of the girder bearing reactions on both sides of a pier. Figure 7 Total Girder Line Reaction Figure 8 Girder Bearing Reaction 11

15 Customizing PGSuper PGSuper has an advanced software architecture that allows third parties to extend and enhance its capabilities. At BridgeSight Software, we can add new analysis capabilities to meet your needs. For details, contact us at BridgeSight Inc P.O. Box South Lake Tahoe, CA PGSuper Professional BridgeSight Software is offering an enhanced version of PGSuper called PGSuper Professional. In addition to all the great features in the free version of PGSuper you get: BridgeSight s one-of-a-kind Girder Design Dashboard PGSuper to AASHTOWare Bridge Exporter 3D Visualization Export Analysis Results to Excel Enhanced Library Management LandXML Data Exchange Enhanced Reporting Toll-free telephone support Direct support High priority treatment in the PGSuper.com Support Forums Exceptional customer service from a reputable and proven company If you like PGSuper, step up to PGSuper Professional! Visit our web site at for more information and a free trial offer. 12

16 References 1. American Association of State Highway and Transportation Officials (AASHTO), 2010, AASHTO LRFD Bridge Design Specifications. 5 th Edition, Washington DC. 2. American Association of State Highway and Transportation Officials (AASHTO), 2012, AASHTO LRFD Bridge Design Specifications. 6 th Edition, Washington DC. 3. AASHTO T-10 Concrete Design Committee, Agenda Book for PCI Committee Days, Chicago, IL, March 29, PCI Bridge Design Manual, 3rd Edition, First Release, Precast/Prestressed Concrete Institute, Chicago, IL, November Washington State Department of Transportation, Bridge Design Manual, Olympia, WA 6. Washington State Department of Transportation (WSDOT), PGSuper User Guide Olympia, WA 13