Steel Structures: Analysis/Design Course using MIDAS GEN - SIMPLE STEEL TRUSS SHED (Part 2)

[@allmondalmond9969]

Bottom Chord why used Lz 1000mm. , Vertical Member Brace Along Z axis About Ly (Ly could be use 1000mm. Lz could be use 10,000mm.)

[@analysisdesignstudio3363]

Thanks brother for comment.. Acutally these lengths (Ly and Lz) are buckling lengths used in calculation of KL/r.. First thing is that Since the bottom chord should design as a beam not as a column sowe can ignore this. I will make a video on this concept. But lets say if we consider this to check its axial strength as well.. So thats why i have explained it here.. You can pause the video @ 22.15 and 22.51 and see the buckled shape.. In buckled shape for y local axis , observe that zero deflection occur @ 0m and 10m.. But for z local axis, zero deflection occur after each 1m thats why Ly is 10m and Lz is 1m. Hope I can make you clear about this ...

[@matteoponzano3318]

@@analysisdesignstudio3363 the bottom chord is not compressed, why define Lx and Ly ? I don t undestand Well... thanks

[@matteoponzano3318]

* why define Ly and Lz if the bottom chord is in tension?

[@analysisdesignstudio3363]

@@matteoponzano3318 thanks brother for comments. Since truss is a member in which axial forces as well as bending shear (due to continue member) are induced,, as the code prescribed to find interaction ratio, and the programs calculate axial tension as well as axial compression for each member,. Thats why we have to give Ly Lz..

[@matteoponzano3318]

@@analysisdesignstudio3363 thanks a lot. Compression stresses that derives from bending, in general, can generate lateral torsional buckling (Lb).... Ly and Lz should only account for axial stresses or not? Where i wrong? Thanks very much for your's tutorials

[@muhammadnaumanjawad1512]

sir, Bottom chord lb = half of total length while lb is for compression flange but the mid beam connecting the bottom chord is connected with the web of bottm chord member? correct me if am wrog plzz.

[@analysisdesignstudio3363]

Yes you are absolutely right. I will make video related to Lb in which i will explain all the concept. Thanks for notifying me ❤️

[@torsiendebobhie9119]

hi Brother, kindly have a comments on this concern,re bottom chord braced length along local y axis may be its 5m because it has a brace/strut located at the center of the bottom chord...for clarification only..thanks

[@navinchandak8372]

something wrong in putting the unbraced length of bottom chord members. Since vertical members of truss braces will restrain the moment in y direction I feel Ly should be 1.0m (as you did for the top chord members), and Lz should be 5.0m, because of the presence of a central runner and Lb will also be 5.0m. Pls check.

[@analysisdesignstudio3363]

Thanks brother for comment. vertical members of the truss will not restrain deflection due to bending of bottom or top chord in local y direction as they will move with downwards (as the bottom chord deflects) thats why Ly should be 10m. But in local z direction, these verticals will restrain the deflection. so Lz = 1m. Lb = 5m for bottom chord as central girder is running midway in trusses. for Top chord, Ly = 1.0284m beacuse of presence of purlin as they provide restrain and Lz = 1.0284m beacuse its of vertical braces (as top chord is inclined so its inclined length is used) and Lb = 1.0284m also because of presence of purlin as they provide restrain against lateral torsional buckling. Please check the deflected shape shown in video carefully. Another important point, Ly and Lz are effective length for slenderness check.(KL/r) while Lb is unbraced length used for account of lateral torsional buckling.

[@muawiyahasham7300]

very well explain

[@torsiendebobhie9119]

Correct me if im wrong...rx should be constrained(fix/check) and rz,ry should be released(pin/uncheck)...

[@analysisdesignstudio3363]

Thanks for comment. Brother.. FEM software considers Moments ABOUT any axis. Pause this video @ 1:21 and observe the Truss elevation. Two axes are also shown there (X and Z axes). so to make these columns fix at base for X-Z Plane, Perpendicular Axis Moment (Y-Axis) must be Restrained (Means Lock). Similarly for the other Frame Elevation (@2:32). Hope I can make you clear about this.. Thanks

[@miffra5480]

Can you give online tutotial on zoom live

[@nisarahmadwani5362]

Are u providing course

[@analysisdesignstudio3363]

I cant get ur point.

[@zabuxman]

Amazing

[@analysisdesignstudio3363]

Thanks Jose...

[@muhammadshahroz250]

Great

[@farooqkhanafridivlogs8490]

mashaallah