Load Combinations Using Moving Loads

I have run into this problem several times now and have not found a good solution for it yet.  I am modling a large structure in which I need to consider several loaded lanes of traffic traveling accross it.  To generate the moving truck loads I am using STAAD's vehicle definition and load generation features.  The structure I am analysing is approximately 96 feet long and i need to consider all possible load patterns for 4 lanes.  From what I have found there is no way to include load generations within a load combination.  To get around this I have taken load generated for each lane and put them into their own envelopes (i.e. all loads that get generated for the moving load in lane one get enveloped).  In order to make the necessary AASHTO Load combinations I then have to export all results out of the prgram into Microsoft Excel where i can take the enveloped results and combine them with the results from any of the other static loads that have been applied.  This is a very tedious and time consuming process in which there is great potential for human error.  Is there any other way that these load generations can be combined with other load cases within the STAAD.pro program so that I do not have to export the data out and do it manually?  Also, I am not able to use the STAAD.pro BEVA package for this as it is not approved for use by the DOT we are working for.  Any input or suggestions on this would be much appreciated.  Thanks.

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  • Here is a model that will combine the moving loads into the load combinations. It is rather impractical on a large scale due to the number of load cases the moving loads generate and the associated analysis time, but it seems this is the only way to do it...

    You need to create your "load combinations" as REPEAT LOADS. You then need to ADD LOAD these repeat loads to the generates moving load. You would also need to create multiple VEHICLE DEFINITIONS in order to get the correct load factor on the generated moving load.


    STAAD SPACE
    START JOB INFORMATION
    ENGINEER DATE 14-Jan-16
    END JOB INFORMATION
    INPUT WIDTH 79
    UNIT FEET KIP
    JOINT COORDINATES
    1 0 0 0; 2 0 0 20;
    MEMBER INCIDENCES
    1 1 2;
    DEFINE MATERIAL START
    ISOTROPIC STEEL
    E 4.176e+006
    POISSON 0.3
    DENSITY 0.489024
    ALPHA 6e-006
    DAMP 0.03
    TYPE STEEL
    STRENGTH FY 5184 FU 8352 RY 1.5 RT 1.2
    END DEFINE MATERIAL
    MEMBER PROPERTY AMERICAN
    1 TABLE ST W14X22
    CONSTANTS
    MATERIAL STEEL ALL
    SUPPORTS
    1 2 PINNED
    DEFINE MOVING LOAD
    TYPE 1 LOAD 1
    DIST 0
    TYPE 2 LOAD 0.75
    DIST 0
    LOAD 1 LOADTYPE Dead TITLE DEAD
    SELFWEIGHT Y -1
    LOAD 2 LOADTYPE Live REDUCIBLE TITLE LIVE
    MEMBER LOAD
    1 UNI GY -0.5
    1 CON GY -10 10
    LOAD 3 LOADTYPE Wind TITLE WIND +X
    MEMBER LOAD
    1 UNI GX 0.05
    LOAD 4 LOADTYPE Wind TITLE WIND -X
    MEMBER LOAD
    1 UNI GX -0.05
    LOAD 101 D+L
    REPEAT LOAD
    1 1.0 2 1.0
    LOAD 102 D+.75(L+WX)
    REPEAT LOAD
    1 1.0 2 0.75 3 0.75
    LOAD 103 D+.75(L-WX)
    REPEAT LOAD
    1 1.0 2 0.75 4 0.75
    LOAD 104 0.6D+WX
    REPEAT LOAD
    1 0.6 3 1.0
    LOAD 105 0.6D-WX
    REPEAT LOAD
    1 0.6 4 1.0
    LOAD GENERATION 30 ADD LOAD 101
    TYPE 1 0 0 0 ZINC 1
    LOAD GENERATION 20 ADD LOAD 102
    TYPE 2 0 0 0 ZINC 1
    LOAD GENERATION 20 ADD LOAD 103
    TYPE 1 0 0 0 ZINC 1
    PERFORM ANALYSIS
    PARAMETER 1
    CODE AISC UNIFIED 2010
    CHECK CODE ALL
    FINISH

    Answer Verified By: Carl Oberg