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Learn Wind Load Calculation & Design in STAAD.Pro as per IS 800:2007.
This video covers step-by-step wind load application and structural design using STAAD.Pro. Perfect for civil engineering students and professionals.
This video covers step-by-step wind load application and structural design using STAAD.Pro. Perfect for civil engineering students and professionals.
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00:00now we have already calculated dead loads and live loads so after that we
00:04shall calculate the wind load now the wind load basically depends on the
00:07structure in which you are you know basically constructing this particular
00:11truss so for that we have to refer to the we can say either AS 875 part 3 or
00:17we can refer to the National Building Code 2016 also so in that we do need to
00:22refer to the area where they are guiding us regarding the wind coefficient for
00:28the wind roofing
00:34so if we refer to the this NBC National Building Code 2016 we can refer to the
00:40parts structural design and in this basically we do have this load section
00:44and this we can go to the wind load section and from here first of all we can
00:49select the area where we have to you know apply the wind load let us say the
00:56area in which we are in line somewhere here let us say it is in Jaipur area so
01:00for Jaipur it is green killer so the wind speed that we have to consider is 47
01:04meter per second and the life of the building that we have to consider is let
01:10us say we have to consider as a 50 years so for that 47 K1 value is
01:17basically one only and if you're talking about the K2 let us say the height is
01:21less than 10 meters and it is 10 in category 2 so K2 is also one K3 is
01:26basically the topography factor that we can take it as one because let us assume
01:29that it is on the plane land and K4 is the we can say as the cyclonic factor so K4
01:37factor we can take it as one for all of the structure considering it is not an
01:40industrial structure or it is not a structure of post cyclonic importance so
01:46after that KD, KA and KC also we can you know consider so KD is basically the
01:51directionality factor so directionality factor that is usually taken as 0.9 for
01:57this kind of we can say triangular or trust structures or buildings and KA is the
02:02area averaging factor so larger the area we can say the lesser shall be the area
02:06averaging factor so tributary area let us assume that in our case it is less than
02:1110 meters here so we can assume it as the KA conservatively as one only and KC is
02:16also combination factor so KC for the value of the case we do have to refer to
02:21the we can say 4.5.3.3.13 so KC also as of now you know we can take it as 0.9
02:30only so multiplication of KD, KA and KC cannot be less than 0.7 as per this
02:37particular statement here so what we can do is that we can go to the excel file
02:48so in here we can enter the length width obviously yeah so on that we can enter
02:55but it won't be that much of importance of the values that are important is first
02:58of all this Perlence spacing here so Perlence spacing 1.5 meter we can select
03:03base spacing for we can say center that we can select it as 6 meters base spacing
03:08Gable and also we can select it as 6 meters and the EVE height we can assume it
03:13as 5 and maximum EVE height the slope that we have taken was 1 is to 5 for the
03:20span of 20 meters so
03:24the height here this was basically this is 2 meters and this is 0 meters so the height
03:34was basically 2 meters so 5 and 7 that is also fine and roof slope here basically
03:44that is dependent on this particular number so the width of the truss that was
03:48basically 20 so slope that can be calculated as 5 degree so after that if we are talking
03:57about the this weight and this we already calculated we don't need to you know again
04:06enter these values here the main cause of concern was this value that is 47 and all
04:10of these remaining factors even factor we can take it as one probability factor all of these
04:17k2 k3 k4 that already we have discussed here as one and after that the value comes out to
04:22be 1.325 gain per meter square so that is basically 0.6 into 47 into 47 and after that
04:30kd additional factor we can take it as 0.9 ka that we can assume it as 1 kc also we can take
04:37it as 0.9 so the value that we do need to consider 0.81 so the wind pressure comes out to be 1.074
04:47so assuming the uh the shed that we are working on is partially enclosed let us assume that
04:55so with that and additionally we have to you know consider the h by w and l by w values also
05:01so h by w is the height divided by width and length divided by width so this also we can
05:07assume it as let us say considering the we have the 6 base so we can assume it as 36 meters and the
05:13other direction we can assume it as 20 meters so with that our h by w value comes out to be 0.25 and
05:20l by w comes out to be 1.8 so uh here this is the basically table that is given in is 875 part 3 so if
05:32our h by w is 0.25 so that is less than 0.5 and the l by w is 1.8 so l by w is 1.8 it means that it is in
05:44between this and this value that is 1.5 to 1 so for the wind angle of we can say 0 degree the
05:52coefficient that we do need to reference are these coefficients that is plus 0.7 minus 0.25
05:58and minus 0.6 and minus 0.6 so for 90 degree uh these shall be minus 0.5 and minus 0.5
06:06and these values shall be the coefficient for the wall it shall be minus 0.6 minus 0.6 plus 0.7 and
06:15minus 0.1 now but the thing is that we only have to refer to this particular table this is for your
06:20understanding that you know we do know how to calculate coefficient for the wall also
06:24but for the roofing arrangement because ultimately we are only modeling the truss here so for the
06:29roofing arrangement we have to refer to table number 5 so for that if h by w is 0 point less
06:34than 0.5 our h by w is less than 0.5 and the angle of the degrees of the we can say uh roof here so for
06:46that basically the height of the roofing was basically 2 and that we can divide it by the
06:53considering it as a triangle that we can divide it by 10 that is the span divided by 2 so the number
06:59comes out to be 0.2 so we do need to you know find out the tan inverse of 0.2 so tan inverse of 0.2
07:11means that we do have to just click on here and 0.2 so the value or the slope of the roofing comes out
07:22to be 11.3 here so uh this basically the one that we do need to refer is 10 and 20 so the values are
07:31minus 1.2 and minus 0.4 here and these values and minus 0.8 and minus 0.6 obviously there shall be some you
07:40know uh reduction here because by uh going from 10 to 11 there shall be a little bit of interpolation
07:47but considerably we can assume these values here so on the uh wind load diagrams the wind comes out
07:54to be minus 4.5 that is if it is negative it acts away from the roof and if it is positive it acts
08:02towards the roof so considering that and right now we have to deal with four kind of wind loads here
08:08so we can just uh divide this here into two parts here so first of all you know we just need to add
08:19the wind load here so we can uh rename this wlxs wl1 and we can uh add further wl2 wl3 and wl4 cases also
08:33so this we can add it as wl2 the third we can uh rename it to wl3 and fourth we can add here as wl4
08:47so this we can add wind load values here so we can go to the member load and the thing here is that we
09:04do have to apply in the local direction wind load does not that is independent of the gravity but it
09:11is dependent on the member local axis so this we have to apply it in the local only wind load is
09:18never applied in the global direction or global y direction especially if we're talking about the
09:22wind loading on the roofing management so here it is like a suction that is happening so we can enter
09:304.51 here and if it is positive it means that it is acting upwards and the second value that we
09:40do need to enter here is the 0.64 here and that is pressure so it shall be negative
09:52so 4.51 that we can like apply it on all of these members here
10:00so we can select all of these members here and then just simply apply 4.51
10:05kn meter that shall be the we can say suction here and here you can see that how it is acting away from
10:12the structure because it is negative and because it is suction and this pressure that shall be acting
10:19towards the structure or towards the building that is pressure
10:26so we can press shift v again to remove these values so this is how
10:31wind load is acting with negative cpi and that is across the ridge
10:35the second one is basically we can say wl2 that is wind across the ridge with positive cpi so this
10:43also again here we can add and here we can go to the member load and here again we can enter
10:51minus 10.95 that is again the suction that we are referring to and on the right side also that
10:58shall be suction that shall be happening and as per my experience these shall be the governing values
11:03for the design of this particular structure because this value is quite high 10.95 and if
11:10we are talking about the wl3 here so this also we can enter that is again the member loading
11:20here we can enter 8.37 that is suction that is happening
11:26and on the right hand side it is again suction that is happening that is 7.09 here we have done the
11:34mistake it should be local y and if we are talking about a wl4 most of the times you know as per my
11:46experience also wind parallel to ridge with negative cpi really governs the design because usually this
11:52is a very low value and here also you can see that it is hardly 1.93 in comparison to the 10.95 that
12:00we are referring to in wl2 and here also it is negative so the section is happening so it is also
12:080.64 so we can select or what we can do is that we can just simply go to the edit list and then just
12:17simply copy paste these members here ctrl c and ctrl v and assign and here also for wl3
12:25assign similarly we can select these 4 to 10 members here ctrl c and ctrl v assigned ctrl c and ctrl v assigned
12:44and ctrl c and ctrl v assigned so uh you know we have applied the wind loading for all of the parameters
12:51here and we can just simply save this excel file and we can just go to our what we can say typical
13:00start file here so after that we can add the load combinations here so we can go to the auto load
13:05combination that is a very helpful command by start so we can just simply refer to the country code for
13:11which you are designing in our case it is indian standard here we can select is800 2007 and table 4
13:19that is basically the code for the steel structures so we can add the combination here as 101
13:27and left click on generate loads now the thing here is that we can just simply skip this plus 0.6 and
13:33minus 0.6 because ultimately 1.2 factor shall be governing the design here so we can simply move
13:40that and again 1.5 1.5 1.2 and 1.2 101 shall be governing the design
13:45and we do need to you know remove these 3 5 6 and 7 but the thing here is that these are not
13:54chronologically numbered correctly so we can go to the editor file here
13:59and we can go to the editor file and here 1 2 3 we can rename it to 4 that shall be very helpful
14:09so if you know if you are checking the results after the designing so 1 2 3 4 5 and 6 here now that is fine
14:19we can just simply
14:28yeah run the analysis here and here we can see that now they are numbered in the correct chronology
14:34so we can left click on auto load combination is 456 is 800 is in 2007 and table 4
14:43combination number 101 generate loads here we can just simply remove this load combination we can
14:51simply remove this negative load combination because ultimately the direction is important
14:55that is also the mistake that you know many engineers do they add the negative wind pressure
15:00irrespective of because or they have ultimately calculate all the combinations here so this we
15:06do need to take care and here also we can just simply remove these negative combinations
15:12and here also we can remove the negative combinations this also we can remove
15:18here also it is okay and here also we can remove the negative here also we can remove the negative
15:25so these are all the you know correct load combination but one more thing that i always do
15:35in my file is that i do make a separate you know numbering for the serviceability load combinations
15:42so these are all the strength design load combination we can left click on add
15:47here again we can click on 201 click on generate loads option just remove these
15:53factored load combinations here here also remove these factored load combinations
16:03this also we can remove and these also we can remove the negative combinations here
16:10these also we can remove the negative combinations here so now we have a different series
16:14to tell us the difference between the strength load combination serviceability load combinations
16:19so strength load combinations start with 101 series our serviceability load combination to
16:24check the deflection and the serviceability limit state that start with the 201 series so
16:30we can left click on add here and what we can do additionally here is that we can just go to the
16:36editor file and correct the numbering because that shall help a lot and you know when we are
16:41checking the results so this exercise you can do it here and i just want to save your time
16:48so you can rename it to like 101 102 103 104 like this and i won't be doing that that you can do at
16:59your end similarly for this part also here you can just simply you know remember the ms201 202 like this
17:09so this is how you know you can save your time and like correct the modeling that is just a part of
17:16the good practice so one more thing that you know many structural x queen structure engineers do is
17:24that they add the envelope here so first we can say strength design load combinations we can enter
17:31these 101 series this also is a very you know major advantage that also i shall teach you shortly but
17:39before that we can just add strength design load combination and here we can select the serviceability
17:44also and we can select 201 series so that is also very you know major advantage of selecting the
17:50different series because ultimately you can just simply you know select the strength design and service
17:58ability load combinations and make them as a different envelopes so this command is also now
18:04fully done and corrected after the analysis we can go to the define commands here we have different
18:11kinds of analysis option so we don't need to do p delta analysis for trusses we don't need to do the
18:17non-linear analysis also or direct analysis that is an approach by the american standards
18:23and we can just left click on perform analysis here and left click on add and close and after that we
18:31can go to the design command under design we can go to the steel in here we can select is 800 2007
18:37and a limit state design so we can go to the is 800 2007 and lsd here so we can go to the define
18:47parameters here so these are the various commands that you know you do need to understand if you
18:52are designing the steel structures so we shall start from the top and here we can start by adding the
19:03f y ld so f ld we can you know assign 250 newton parameters here or we can say 250 000 kn per meter
19:13here k by kz we can take it as 0.85 let me just tell you oh you know this also i shall explain shortly
19:23what exactly is this particular concept and we can add the l y parameter also now l y parameter let
19:32me just write a random number here i shall tell you what exactly should be the number for l y here
19:37and the mean for this kind of structure it should be 180 for all the members here and
19:51yeah seismic provision you know we don't need to check assume that we don't need to check for this
19:57kind of structure this is a hot roll section we can left click on you know hot roll and
20:03yeah so the thing here is that you know in many of the structures we do provide the tie we can say
20:10tie rods sorry or the tie cords at the bottom of the truss also so assuming that we are providing the
20:18bottom chord members at the bottom chord members at this interval here
20:27yeah
20:30sorry 4.286 and
20:33this is 4.286 and this again here is 4.286 yeah so l y we can enter here as 4.286
20:53so basically the thing here is that l y is basically the we can say length and local y
20:59for slenderness so this we are assuming here that the truss from this point to this point
21:06that is free to see along the other axis that is the one that is going away from the screen or
21:12coming towards your face and along the major axis obviously we do are providing the tie so that is why
21:19we have not entered the l z value l z is always the major axis and l y is always the minor axis
21:26so we can assign to view n s now k y and k z is basically for these members here
21:32now these members are fixed from this point to this point but usually you know the curve
21:36that happens when the compression force comes that does not happen from this point to this point
21:42there is a small straight length and then after that this particular curve happens
21:46so that is a theoretical concept and that can be you know applied for to all of these secondary
21:54members here so we can select all of these secondary members and then apply k y and k z to all of these
22:02members here yeah so now k y and k z can be applied to all of these members here
22:16this is used to check the k l by r value and ultimately that shall also go on the design
22:35if we are talking about the compression forces so main vanity we can apply to the complete view and
22:41http one that also we can assign it to complete view and under the command option we can left click on
22:46add and take off also that also we can left click on add here so check code has been assigned to check
22:52the truss as per the is it in a 2007 lst now one more thing that we are missing here is that we have
23:00not added the load list here so this is the load list command and under this particular option we can
23:06enter the strength design envelope here so we can left click on ok but the thing here is that load
23:11list envelope has been entered after the design commands so to correct that we do need to go to the
23:17editor file here we can just select load list envelope one ctrl x and after that
23:26end define envelope and then here we can enter the load list envelope one because it should be above the
23:31design commands so envelope one is basically the strength design parameters so we can close this
23:39window editor now we can just go to the analysis and now we can just click on the run analysis
23:53so we have you know done everything uh the good thing is that you know this workflow is very correct
23:59first of all geometry then properties then materials and specifications support loading
24:04analysis and design and after that only you know it is better to go to the this particular run
24:09analysis option so now the analysis has been done so we can go to the workflow and post processing
24:14to see the results now here comes the work of the envelope here this is envelope one that is
24:20strength design and this is the envelope two that is the serviceability design so we can left click
24:24on apply here and we can study the displacements that are happening so displacement that is happening
24:30here is very very high that is minus 101 mm and that is i must say a very high deflection here so if you
24:37want to see the bending diagram so we can go to the envelope or we can sorry go to the combination and here
24:46we can select the 240 so this is basically the bending behavior here so here you can see that how it is
24:55you know uh completely failing over here we must say um along the x it is happening 19 mm and upward wind
25:04force it is happening in load combination 250 so we can go to the combination and 250 so here we can see that
25:11it is going up uh you can see the shape like this by pressing ctrl key and moving the scroll wheel on
25:19your keyboard so by pressing ctrl key and scroll wheel up and down you can see this kind of behavior you
25:25know animation diagram or the deflection diagram so now that is resolved but the bad thing here is that
25:33it is failing in the serviceability and it is must be failing in the strength design also so we can go to
25:37the select property name and failed beam so here we can see that the completely outer periphery is completely
25:43failing in the design and the ratio is also quite high here although this member is passing in the design
25:50but this member is completely failing and
25:56yeah so after that what we shall do here is that we shall first of all change this particular you know
26:04uh we have selected two as this member here so we can strengthen this by instead of 75 by 75 by 8
26:12we can proceed with the 100 by 100 by 8. so we can select isa 100
26:21by 100 by 8 here and after that for the fourth section this is isa 75 by 75 by 8
26:29instead of this as the loading is very high so we can proceed with let us say 120 by 120 by 10 long
26:37leg back to back double angle and the spacing of the member here is 10 mm so we can press ctrl and
26:432 option on a keyboard to see how the trust looks in real and we can go to the view and 3d rendering also
26:50so this is how you know the trust shall be looking in real that is a double member on all the external
26:56periphery and these are the members that we have selected as the time members so again we can you
27:02know run the analysis option to see that whether the members that we have selected
27:08are safe in the strength design or not
27:13so we can go to the select property name and failed wings so now here we can see that none of the members
27:21are failing in the design we can go to the labels and design results we can click on the actual ratio
27:28we can click on show values here and apply so here we can see that middle uh this members here is ratio
27:350.866 and here the ratio is like very very high 0.996 it is never recommended to have a ratio greater than
27:45than we can say 95 or 9 0.95 or 0.96 so we can go to the property section here again and instead of 120 by 120 by 10
27:57we can select uh let us say 120 by 120 by 12 long like back to back double angle and spacing here is 10 mm
28:07so we can again run the analysis here
28:15so again we can check the ratios and now instead of 0.996 and now it is coming 0.849 now that is safe
28:26now the thing that i was referring to here if you remember we have selected the status
28:31so now if we are you know clicking on any of the members here let us say for this particular member
28:37here you will see that my and mz is perfectly zero it is not even 0.1 and 0.2
28:43it is completely zero and here we can see it is 535 here we can see that that is c it means the compression force
28:50so in all of the members here you can see that only and only axial forces are traveling
28:56in none of the members you can see that any kind of bending moment is there
29:00the bottom member is basically in tension so here you can see that it is t here so that is in tension of
29:06minus 769 kilo newton so same here also here also it is minus that is it is in tension and on the top it
29:14is basically in compression and we can go to the workflow and post processing here we can select uh
29:23envelope one here apply and okay here we can switch on this fx and we can switch off the displacement
29:32diagram and here we can select the combination here as uh 1.5 dead plus live and press ctrl key
29:41and then scroll on down so basically the blue uh diagram that is basically for the tension
29:51and the red that is basically for the compression and if you want to see these values we can click on
29:57we can say annotate value here here we can select beam results and under the axial ends and annotate
30:06and here we can switch on this so now here we can see the values also the actual forces that are happening
30:11so let us if you want talking about this particular member we can click on view selected objects so on
30:16the end it is having a we can say tension of 259.95 kilo newton so this is how you know we can just uh
30:24see the results second thing that you do need to understand uh these are the reactions on the ends
30:34so here we can click on the summary so here we can see that the maximum reaction that is happening
30:40is minus 99 under this particular case and maximum 198 for 103 load combination here we are talking about
30:48the serviceability but obviously we have to uh check the reactions for the strength design yeah now
30:56sorry the that is correct one zero one is the strength design only so 198 and 99 and this is the
31:03horizontal force that is coming that is 15.45 now that is one aspect of checking the reactions
31:11and after that we can click on the displacement but displacement we do need to check for the
31:15serviceability load combination so we can click on envelope to and apply and okay and here we can
31:21click on summary so instead of the uh 100 mm exceeding 100 mm that we were getting uh earlier now we are
31:29getting only 44 mm so 44 mm uh we can say uh assuming that our span is approximately 20 meters and the level
31:38deflection is l by 250 so
31:45what we can do here is that we can just simply divide 20 000 that is an mm that we can divide it
31:54by 250 so allowable deflection comes on the range of 80 mm and in our case the deflection is only 44 mm so
32:03that is also like safe for us so the trust that we have designed is safe in the we can say deflection
32:10reaction reaction reaction also we can check so whatever you know supporting structure or column
32:13or rcc column or steel column whatever you're having that you can design for these particular forces
32:20and displacement also we have checked beam results also we have checked that all the members are
32:25passing in the design by this particular option and now this member is failing is a 65 by 65 by 8.
32:34uh what we can do here is that we can just simply add isa 100 by 100 by 8. this was isa 65 so this we can
32:46assign it to these members also isa 100 by 100 by 8.
32:49so we can again run the analysis there might be a little bit change in the results but overall you
32:57know we are looking forward for a structure which is safe and here again i repeat this is basically the
33:04uh truss analysis select property name and field you know so no beams are failing in the design now we
33:12shall save as this model and instead of the truss we shall add a space here so now we have switched
33:20from the truss analysis to the space analysis
33:29so again we can run the analysis here
33:32so here we can see that if we see the failed beams here now here we can see that this beam
33:47is failing in the design earlier this beam was passing in the design but now it is failing why
33:52here you can see the bending moment value so that is the difference between the
33:56truss analysis and space analysis in the truss analysis we are just simply ignoring any kind
34:03of bending moment but in the space analysis we do have to consider the bending moment here also
34:10and you must be getting the warnings also for the stability so for stability in many of the cases
34:16what might we have to do here is that we have to provide the restraint along the x-axis also
34:23so let us just again run the analysis here
34:37so again you know it is failing in the design so many you know and uh we can go to the select property
34:43name and field we now it is passing in the design because we have provided a restraint here but
34:53if we open the output file here you can see that uh there is there are these instabilities and
35:01excessive loss of digits and value of ky or kz factor is also like coming quite high
35:07so this instability that is because of we can say the space analysis that we are doing
35:13so to avoid that in many of the cases what might we have to do here is that
35:17we have to provide the rotation restraint and also along the perpendicular direction so that i
35:24do not recommend so that is why you know it is always recommended that as per my opinion you can
35:29proceed with the start truss analysis there is nothing wrong in doing that because ultimately
35:35we are designing a pure truss rest you know it is up to ingenious perception some of them are
35:42comfortable in space analysis some of them are comfortable in the truss analysis so that is now
35:46you know your call now the thing here is that in additionally now we have selected the this
35:53particular arrangement that is with the angle section so instead of that if you want we can you know
36:02proceed with the box sections also so here we can click on the standard sections database
36:07and this exercise you can do it at your end that is instead of the what we can say as the
36:19angle sections you can replace them by these square hollow sections and rectangular hollow sections
36:26that is quite simple and like in this particular arrangement if we want to select the square hollow
36:33section we can select 150 by 150 by 6. let us check that whether it is passing or failing in the design
36:40and the thing here is that uh if we want to go for the higher section sizes let us say this isa
36:46sorry the scale hollow section of 150 by 150 by 6 is not passing in the design
36:51for that what we can do here is that we can click on the tata structure or apollo or general sections also
37:03so here we can select tata structural or apollo apollo tubes so if example for apollo apollo tubes
37:11you will see that sizes are going as high as 600 mm but they are not also not like not quite easily
37:18available in the market if you want to proceed to the higher sizes we can proceed for 250 by
37:23100 by 4 or 250 by 150 by 6 if the loading is quite high or for the square hollow sections also
37:31that is there was going up to 150 only but here you can see a size as high as 500 by 500 also
37:38and here also you can see let us say 200 by 200 up by 10 or 12. so as per the you know uh requirements
37:45this you can do the exercise at your end that is quite simple that is the outer periphery sections has
37:51to be the heavier this section shall be on the top these line these members shall be taking the
37:57compression these members shall be taking the tension and again these members shall be taking the
38:03compression or tension depending on the loading uh direction and these sections shall be a little bit
38:10of we can say heavier that is the center members and these members shall be a little bit on the lighter
38:16side so you can try design redesigning this particular trust with square hollow sections or rectangular hollow
38:23sections or circular hollow section and check the difference in the weight also weight of the truss also
38:31so i hope the concept of truss design is clear to you if there are any questions
38:34then you can simply ask that in the question answer section
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