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LARS | LEAP | OpenBridge | RM Wiki Live Load Forces and Moment Calculation- Service I Limit State
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    Live Load Forces and Moment Calculation- Service I Limit State

      

    Document Information

    Document Type: FAQ

    Product(s): LEAP CONBOX/CIP RC/PT Girder

    Version(s): All

    Original Author: Bentley Leap Bridge Technical Support Group – VM

    QUESTION:  How the program is internally calculating the Live Load Forces and Moment for Service I Limit State ?

    ANSWER:

    1) A 1 span Box girder bridge was created in Leap Conbox. In the Load/Analysis TAB  I assigned HL-93 -Simple Span Truck..

    2) The trucks Included Design Tandem ,Design Truck and Design lane then Ran the analysis and clicked on View Analysis Button.

    3) In the Analysis Results window I selected these options Final --> Truck/Lane --> Design Tandem --> Min/Max Forces. The same procedure was followed for Design Truck as well.

    4) At Mid span location of 30 ft I noted down the Max Moment of 700 K-ft and & 800 K-ft for Design Tandem and Design Truck respectively.

    5) I followed the same procedure and for Design Lane I noted down the Max Moment as 288 k-ft.

    6) In the Analysis Results window I selected these options Final --> Truck/Lane --> Design Truck --> Min/Max Forces.

    7) After scrolling down halfway the user can see the Distribution Factors and Impact Factors for Service I, III and Strength I limit states at different POI.

    8) Then in the Analysis Results window I selected Final --> Live Load  --> HL 93-Simple Span --> Min/Max Forces option.

    9) At Mid Span Location of 30.00 ft I noted down the Total Max Moment as 6262 k-ft

    10) Please follow the following procedure to calculate the Final Maximum Moment.

    11)  Design  Truck + Design Lane = (800 x 4.63 x 1.33 ) + ( 288 x 4.63 x 1 ) = 4926.32 +  1333.44

    12) The LRFD Live Load combination Factor is = 1 for Service I limit State.

    13) Total Maximum Moment = 6260 k-ft

    There is a minor difference between hand calculation and Conbox output results which can be ignored.

    Please see the attached screen shot for more information.

    • CIP RC/PT Girder
    • LEAP Bridge Concrete
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    • Vinay mysore Created by Bentley Colleague Vinay mysore
    • When: Wed, Nov 4 2015 2:12 AM
    • Dilip Matange [Bentley] Last revision by Bentley Colleague Dilip Matange [Bentley]
    • When: Wed, Feb 24 2021 5:03 PM
    • Revisions: 6
    • Comments: 0
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