nice explanation, but where code did you get EQXR, EQXL , EQYL, EQYR? I think no need of use L and R , instead use +EQx, -EQx ,+EQy and -EQy. The seismic load is assumed to be acting at center of mass and creates accidental eccentricity which will be accounted during P delta analysis. Eight seismic design actions combinations are enough however their results will be converged in to two different values of one for x directions and the other for y direction ( EQX+0.3EQY, EQX-0.3EQY, EQY-0.3EQX, EQY+0.3EQX , -EQX+0.3EQY, -EQX-0.3EQY, -EQY-0.3EQX, -EQY+0.3EQX ). -EQx and +EQX will have the same magnitude output values of internal forces (moments and reactions) similarly for +EQY and -EQY too. Extra seismic action combinations are redundancy. no value change on output. To be sure you can check it on simple model. I have already checked it. live load reduction factor for modal and response analysis (used only for mass source calculation) should not be used during load combination as a reduction coefficient. For the ultimate limit state under seismic action, the load combination must be : Gk+ψ2Qk+AE where Gk is the characteristic value of permanent actions, Qk is the characteristic value of variable actions, ψ2 is quasi permanent factor for variable actions, and AE is the design seismic action (8 combinations are enough). hence please correct it. you are reducing variable loads by 20 % for static analysis. This is the major input for base shear or reactions calculations. for more visit the load combination lists used for seismic case at the code.Thanks for more, visit my UA-cam channels
Thanks for the comment so, First question was where did you get the EQXR, EQXL, EQYR & EQYL and why use L & R ? good question so L & R are simply a variables added to distinguish b/n the 5% accidental eccentricity to the right and left of the center of the mass in both X & Y directions, if you watch the full video you will understand that and also P-delta effect will be considered when the teta (interstorey drift sensitivity coefficient) is above 0.1 but if teta is less than 0.1 P-delta effect can be ignored but it doesn't mean you shouldn't account for accidental eccentricity which will give you the torsional stability of the structure so when you use 8 combinations you are ignoring the accidental eccentricity and you are saying the EQ will be exactly placed on the center of the mass without any uncertainties that may affect the building's safety. And for your second question ψEi is used to estimate a likely value of service loads and to take into account that some masses do not follow perfectly the moves of the structure, because they are not rigidly connected to the structure. The thing is even if you take ψ2Qk in the combination you again are reducing the live load amount.
How we identify upto G+4, are low rise , G+4 upto G+11,are medium and above that are high rise is this information written on our building code. Second is our bulding code says that for medium building use 35 combination
Good question. So there is no a clear distinction on low medium and high rise building but generally its taken a building without elevator taken as low rise and a building around G+5/6 upto around G+10/11 which obviously with elevator considered a medium rise and above that high rise and on the ESEN code the 34 load combination will occur if you use the uncertainities i.e. accidental eccentricities on seismic action which may occur 5% to the left and right of Center of mass so when ever the building height increases the effect of uncertainities becomes significant so it depends upon the building height and the designer is the one that should choose how many load combinations to use some people use 8,9,10 by ignoring the accidental eccentricities the building maybe stable but if an unexpected high intensity seismic effect occurs those building safety maybe in question b/c they ignored the accidental eccentricities which decreases the building torsional stability and again it depends on the building height anyways,so the conclusion is you are the one to decide how many combinations to use.
I now it you can show us thanks bro a lot ❤❤❤❤
nice explanation, but where code did you get EQXR, EQXL , EQYL, EQYR? I think no need of use L and R , instead use +EQx, -EQx ,+EQy and -EQy. The seismic load is assumed to be acting at center of mass and creates accidental eccentricity which will be accounted during P delta analysis. Eight seismic design actions combinations are enough however their results will be converged in to two different values of one for x directions and the other for y direction ( EQX+0.3EQY, EQX-0.3EQY, EQY-0.3EQX, EQY+0.3EQX , -EQX+0.3EQY, -EQX-0.3EQY, -EQY-0.3EQX, -EQY+0.3EQX ). -EQx and +EQX will have the same magnitude output values of internal forces (moments and reactions) similarly for +EQY and -EQY too. Extra seismic action combinations are redundancy. no value change on output. To be sure you can check it on simple model. I have already checked it.
live load reduction factor for modal and response analysis (used only for mass source calculation) should not be used during load combination as a reduction coefficient. For the ultimate limit state under seismic action, the load combination must be :
Gk+ψ2Qk+AE
where Gk is the characteristic value of permanent actions, Qk is the characteristic value of variable actions, ψ2 is quasi permanent factor for variable actions, and AE is the design seismic action (8 combinations are enough). hence please correct it. you are reducing variable loads by 20 % for static analysis. This is the major input for base shear or reactions calculations. for more visit the load combination lists used for seismic case at the code.Thanks for more, visit my UA-cam channels
Thanks for the comment so, First question was where did you get the EQXR, EQXL, EQYR & EQYL and why use L & R ? good question so L & R are simply a variables added to distinguish b/n the 5% accidental eccentricity to the right and left of the center of the mass in both X & Y directions, if you watch the full video you will understand that and also P-delta effect will be considered when the teta (interstorey drift sensitivity coefficient) is above 0.1 but if teta is less than 0.1 P-delta effect can be ignored but it doesn't mean you shouldn't account for accidental eccentricity which will give you the torsional stability of the structure so when you use 8 combinations you are ignoring the accidental eccentricity and you are saying the EQ will be exactly placed on the center of the mass without any uncertainties that may affect the building's safety. And for your second question ψEi is used to estimate a likely value of service loads and to take into account that some masses do not follow perfectly the moves of the structure, because they are not rigidly connected to the
structure. The thing is even if you take ψ2Qk in the combination you again are reducing the live load amount.
How to define load combination if we use response spectrum analysis
thanks
How we identify upto G+4, are low rise , G+4 upto G+11,are medium and above that are high rise is this information written on our building code. Second is our bulding code says that for medium building use 35 combination
Good question.
So there is no a clear distinction on low medium and high rise building but generally its taken a building without elevator taken as low rise and a building around G+5/6 upto around G+10/11 which obviously with elevator considered a medium rise and above that high rise and on the ESEN code the 34 load combination will occur if you use the uncertainities i.e. accidental eccentricities on seismic action which may occur 5% to the left and right of Center of mass so when ever the building height increases the effect of uncertainities becomes significant so it depends upon the building height and the designer is the one that should choose how many load combinations to use some people use 8,9,10 by ignoring the accidental eccentricities the building maybe stable but if an unexpected high intensity seismic effect occurs those building safety maybe in question b/c they ignored the accidental eccentricities which decreases the building torsional stability and again it depends on the building height anyways,so the conclusion is you are the one to decide how many combinations to use.