실제지진의 응답 스펙트럼 사용방법 17분 요약 transcript

okay now this is a response Spectra that I made for a central earthquake East waste component at 1940. she said acceleration response Spectrum okay so you will get all the information so now you understand okay this is response Spectra means we plot maximum values only for design and especially this is for accelerations among acceleration velocities and displacement this is for accelerations okay and you see x-axis represented by the period and only access represented by a acceleration a spectral accelerations we say spectral right spectral means maximum value Perfect Design first cake design and or else as a function of period And as a function of damping ratio of course the if you don't have any damping which is a zero here your response is very huge right and also the building will not stop easily all right and he you you increase your temping ratio from zero to twenty percent twenty percent is the lowest one why because you're building Behavior building performance or accelerations gets very small when you're damping ratio gets very big like 20 percent right okay look at that your response Spectra is expressed as a functional damping ratio as a function of periods don't forget that's two functional two things right damping ratio and period And this is maximum value when your period is zero what that means your building is very stiff as I told you many times right so this is 0.4 G is PGA Peak ground acceleration this is what you see on the building is what you get from your earthquake because your building is very steep right here and you go to the right side that makes your building is very flexible all the fluoresion goes to zero because your building is flexible you don't you don't move right you're not vibrillating because you're building moves at the bottom right so now you have a peak ground acceleration and you have a zero okay so this is you're gonna see probably many many times before you retire in your in your area if you're working on building business and this is very important and and all the engineers United States England Japan Korea they use same response Spectra okay so you don't want to forget that if you want or for high-rise building and this and this design seismic design and these seismic designs are pretty much easy to understand but um you you probably don't want to forget this okay okay and it's your you're having a peak resonance resonance area is 0.5 so you're on very stiff soil I told you a resonance Plateau resonance area or zero for 10 for 20 whatever as a 0.5 when you have a stiff soil a rock something like that okay it depends on what kind of soil what kind of soil that you want to put the building on right okay now let's take a look at different earthquake from New Mexico occurred in 1985. look at this response Spectrum shows you a little different um shapes right what do you see as a different characteristics of this response Spectra compare with one we saw from El Centro can you tell me what's the different thing here I'll give you a few seconds think about it okay your Originals plateau or a longer period it's just two seconds right you have a resonance Plateau at 0.5 SEC and for a central if you remember but this one has a resonance condition it two seconds why why did this happen because of soil conditions underneath of the building in New Mexico New Mexico is very thick filled in soils so that your um earthquake propagates through the thick soils and create a 2 second dominant period so that it's going to cause a big resonance response for building over 20 story building right here 2 right why 20 story building that images if you remember the formula that I gave you is that the formula was 1.1 n 5.1 nnej number of stories so n is 20 which is 20 story building what period you get you get two seconds right so 0.1 and formula get you building period of two seconds for 20 story buildings in other words your toys story building has exactly is a resonance conditions here at two seconds of the response pattern right here so you get a damage for 20 story building you know actually we have a lot of damage around 20 store building in New Mexico in 1985 okay so what why don't you and take a look at the damages and all that through the internet for 1985 and make some memo on this note okay and again the even though the earthquake different earthquake we are looking at the definition of response Vector are same right the response spectral what is the definition of response special again looking at New Mexico earthquake is that this represents a maximum response and then we we chose a acceleration for this case right the y-axis accelerations and we say spectral accelerations we are denoting S A spectral acceleration as a spectral means maximum value for seismic design okay so this is a maximum acceleration or maximum velocity or maximum displacement this case maximum or accelerations as a function of right period and is a function of damping right for a single degree of Freedom system that's perfect definition okay so you don't even have to memorize the definition of response background but is a essential informations that you want to put them in the computer code like Midas e Caps or whatever 3D manager computer analysis to design buildings including raw rice building high-rise building it doesn't really matter okay and this is the way you're looking at the response Vector okay okay uh we're gonna summarize today's lecture today's lecture is most important lecture in rtk engineering because a building is designed basically based on mostly response Spectra Okay so we're gonna summarize and I'm gonna introduce how to use response Spectra how to read response Spectra okay we start calculating period of the building okay we have two ways to calculate period of building okay and we have to know the area of the building to understand and to use response Spectra we'll get two ways here the first way you can use Midas okay second way we use a approximate equations okay then I gave you one approximate equations for this point one and okay we anyway we'll use one of these two method to come up with a period of the building okay so this is very easy process and second once you get period of the building you go and determine the damping ratios so I told you I gave a brief numbers for roll-rise building and high-rise buildings and you know depending on the materials Stills and Company building and you want to take a look at this video clips again to see how you determine dipping Rich if you need and you have to have a artificial damping okay so let's just for example my damping ratio is five percent or one percent for high-rise buildings so you you have to determine damping ratio in second step in third step you have to go enter x axis excess is represent what x axis represents right building period right so you go and get started with the access is using a period of the building which is calculated in step one okay now you're gonna go and hit the response curve okay let's say for example if you go into the let's say put second here right then you go all the way up you hit response curve right but you hit multiple response curve a lot of response curve so which one is yours you don't know yet yes you know how because you have determined the camping ratio in second step right yes you know so say you are having a five percent or ten percent okay then this this curve is yours right because you know that your company is five percent right this is your code right here so now what's next what's next after you hit response curve with a your damping then he you go to the left right you go left to read a spectral value so you go to left and to go to get the spectral net here okay let's forget you this spectral value is the value that you're going to use in diffraction calculation of the building and seismic Force shuffle your your um Newton's law ethical m a isn't it so you know the MAA A A A Part which is from here right so this is how why you calculate accelerations okay so a if you you picked up from y-axis in sa axis you go and use that value right here and multiplied your building Mass so you get a earthquake lateral load easy me okay this is the probably summary of a lecture today after all right okay let me just repeat um the last and position one more time before we um finish this clip right okay uh we get period we calculate period using one of these two ways and remind us or using a approximate equations okay we have a lot of approximate equations here but I gave you one of them right which is 0.1 n okay for still building and you determine amping ratio okay Champion ratio something that you need to talk to somebody who knows them because damping ratio is not really calculated it's just picked select okay as appropriate to your building right and the buildings the damping for buildings different depending on how many floors you have right you have a raw rice building what's the damping ratio around five to ten percent all right what about the high-rise building what's the damping ratio for high-rise building point one percent to 1.5 percent right okay so they're very different be careful right now this is a damping now you get calculate period you get determine damping ratio all right you go start looking at and entering access with period you calculate instead one okay and you're gonna meet a lot of curve right okay like this and you're gonna meet a lot of curve but one curve is yours where you see your damping region right so your damping ratio you select it like 10 percent then this is your if you if you select your damping as a two percent and this is your value right so D and you it's like two percent damping then your this balance is a little bit higher than thereof on this curve right because your damping is small right and you go here and it what s a value in y axis what sa stands for spectral accelerations right okay and we're after you get this value now you're ready to use calculate earthquake Force F no now you know how you calculate earthquake letter forms very easy right the earthquake better Faults Are eventually calculated mass times acceleration the acceleration is coming from y-axis of your response vector so you are completing to understand whole steps for response Spectra all right okay um today's lecture is very important please all of you go and take a look at Cliff carefully and make a um necessary memo and be ready for next clip next clip I will be explaining this second way of getting earthquake force in Midas so there we have if you have to understand and calculate a lot of seismic parameters based on seismic map we have seismic map okay so before we get into further Theory please be read thank you very much for your attention today