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Turkish In my city, Bolu, 80%-90% of the soils consist of Z3 or Z4 soils. The zoning floor heights vary between 3 and 6 floors. The first periods of buildings at these heights are generally between 0.2s-0.7s. These periods coincide with the Spectrum characteristic periods of the soils. So there is a kind of resonance effect. According to the regulation, the Spectrum coefficient is taken as 2.5 in this range and the effective ground acceleration coefficient is increased. However, in some studies I have read, it has been shown that this value rises to 3.5. (Yalçınkaya, 2002) I would like to get your opinions here. It is more useful to try to keep the building period at what values. What should be the differences between the periods? Should they be as close together as possible? Waiting for your valuable feedback. Thanks....
About Building and Ground Period
- Thread starter proisa
- Start date
During my doctoral education, I had studies on this subject. Resonance and the most important solution method for us engineers to avoid its consequences is to design according to the ground condition. Two methods can be followed in this design: 1) By reducing the natural period of the building 2) By increasing the natural period of the building, the design is changed by moving the structure away from the natural vibration period of the ground. Changing the building form to reduce the building natural period: - reducing the height - reducing the slenderness ratio - widening the base of the building Increasing the rigidity: - using shear walls - increasing the number of shear walls - strengthening the outer edges of the building Reducing the mass: - using light load-bearing system - using light non-bearing elements methods can be used. In order to increase the natural period of the building; Changing the building form - increasing the height - increasing the slenderness ratio Reducing the rigidity - rigid framed structure - increasing the frame openings Methods such as applying seismic insulation can be preferred.
Unfortunately, I do not agree with our friend named Siromar. You can't explain to the owners, contractors or construction companies the reasons for making the building too rigid to get away from the ground dominant period, what the f..k ? They say get lost you poor bastard. Secondly, if you try to make the structure less rigid than necessary to get away from the ground dominance period, you start to compromise on structural safety, so no one will award you a medal for this approach. Here, it is possible to measure the rigidity or less rigidity of the structure, as an example, as the number of 0.1xKat. It's an approach that has been going on for years, but it's a really healthy parameter (according to the system, of course). On the other hand, in case of resonance, there is no such thing as the building will collapse to the ground. The structure is damaged in the earthquake and the ground, more precisely, moves away from the dominant period of the earthquake. Of course, no one wants the building to be damaged in an earthquake, but this is what will happen. On the other hand, for a perfect resonance condition, the earthquake should have a constant frequency for at least 10-15 cycles and in the 1st period of the structure with the highest effective modal mass, I am neither such a source nor such a continuous medium (the waves originate from the source). I know (in matlab, you can test it with sine waves of various frequencies at first with single degrees of freedom and then with mathematical models of multi-degree-of-freedom systems by performing dynamic analyzes in the time domain, I know because I did it when I write my master's thesis). At least 10-15 cycles at a fixed frequency, for example, if the 1st period of the building were 0.7 seconds, it would take 7 to 10.5 seconds. There is no such seismic wave (by the way, just because I haven't seen it doesn't mean it doesn't exist"siromar":1iscyokj" said:
). So far, I have studied the fourier spectrum of many earthquake waves, and such waves come only from long-period but very distant sources with various frequencies attenuated, and their amplitudes are naturally low. In this respect they should be harmless (theoretically ???). So what? keep going.Since the spectrum characteristic periods of the floors are normalized along a long curve, if you examine our projects, we cannot get rid of Sta=2.5 in the first 5-6 periods of the building. Of course, the effective modal masses are decreasing, but I think 5-6 periods are enough for the building to be damaged. Since we cannot design buildings within linear elastic limits under the influence of earthquakes, we design them to be damaged in severe earthquakes. A normal citizen, of course, does not want his building to be damaged. But we know that we can't say that it will not be damaged 100%. The important thing is that even if it is damaged, it should be seen the way we want and ensure life safety. By the way, I know that in 1985, 10-15-storey buildings 400 km away from the earthquake epicenter were destroyed due to the resonance event. I will write detailed information about this here... Have a nice forum everyone..."Godfrey":109svxtw" said:"siromar":109svxtw" said:I had some studies on this subject during my doctoral studies. Unfortunately, I do not agree with our friend named Siromar. You can't explain to the owners, contractors or construction companies the reasons for making the building too rigid to get away from the ground dominant period, what the f..k ? They say get lost you poor bastard. Secondly, if you try to make the structure less rigid than necessary to get away from the ground dominance period, you start to compromise on structural safety, so no one will award you a medal for this approach. Here, it is possible to measure the rigidity or less rigidity of the structure, as an example, as the number of 0.1xKat. It's an approach that has been going on for years, but it's a really healthy parameter (according to the system, of course). On the other hand, in case of resonance, there is no such thing as the building will collapse to the ground. The structure is damaged in the earthquake and the ground, more precisely, moves away from the dominant period of the earthquake. Of course, no one wants the building to be damaged in an earthquake, but this is what will happen. On the other hand, for a perfect resonance condition, the earthquake should have a constant frequency for at least 10-15 cycles and in the 1st period of the structure with the highest effective modal mass, I am neither such a source nor such a continuous medium (the waves originate from the source). I know (in matlab, you can test it with sine waves of various frequencies at first with single degrees of freedom and then with mathematical models of multi-degree-of-freedom systems by performing dynamic analyzes in the time domain, I know because I did it when I write my master's thesis). At least 10-15 cycles at a fixed frequency, for example, if the 1st period of the building were 0.7 seconds, it would take 7 to 10.5 seconds. There is no such seismic wave (by the way, just because I haven't seen it doesn't mean it doesn't exist
"Godfrey":35cozvwr" said:What I wrote was about what can be done to prevent the building from being exposed to resonance, and this is not a matter of whether you can agree or not. It is the information accepted by the entire academic community that every engineer should know. What you are talking about should not be taken into account if the earthquake wave creates resonance or not. You wrote an article like I don't agree with you on this issue... What is the logic of the spectrum curve in Tdy? that's exactly what I'm talking about. If the period of the structure is within a certain range according to the floor class, it will be exposed to the maximum load, the period will increase, the effective load will decrease, etc. You said 10-15 repetitions are needed for perfect resonance. is exposure. How many buildings can reach the 2nd Mode without collapsing anyway? You can read many articles about resonance, and I can share my work here. You can also see industrial sites on the internet that have been made easier to demolish due to many resonance effects. I did not see anything wrong with what you wrote, I just disagree with the comments. Resonance may not be a cause of destruction per se, it may just be a part of it"siromar":35cozvwr" said:During my doctoral education, I had studies on this subject. In order to avoid resonance and its consequences, the most important solution for us engineers is to design according to the ground condition. Two methods can be followed in this design: 1) By reducing the natural period of the building 2) By increasing the natural period of the building, the design is changed by moving the structure away from the natural vibration period of the ground. Changing the building form to reduce the building natural period: - reducing the height - reducing the slenderness ratio - widening the base of the building Increasing the rigidity: - using shear walls - increasing the number of shear walls - strengthening the outer edges of the building Reducing the mass: - using light load-bearing system - using light non-bearing elements methods can be used. In order to increase the natural period of the building; Methods such as changing the building form - increasing the height - increasing the slenderness ratio Reducing the rigidity - rigid framed structure - increasing the frame openings can be preferred. You can't explain to the owners, contractors or construction companies the reasons for making the building too rigid to get away from the ground dominant period, what the f..k ? They say get lost you poor bastard. Secondly, if you try to make the structure less rigid than necessary to get away from the ground dominance period, you start to compromise on structural safety, so no one will award you a medal for this approach. Here, it is possible to measure the rigidity or less rigidity of the structure, as an example, as the number of 0.1xKat. It's an approach that has been going on for years, but it's a really healthy parameter (according to the system, of course). On the other hand, in case of resonance, there is no such thing as the building will collapse to the ground. The structure is damaged in the earthquake and the ground, more precisely, moves away from the dominant period of the earthquake. Of course, no one wants the building to be damaged in an earthquake, but this is what will happen. On the other hand, for a perfect resonance condition, the earthquake should have a constant frequency for at least 10-15 cycles and in the 1st period of the structure with the highest effective modal mass, I am neither such a source nor such a continuous medium (the waves originate from the source). I know (in matlab, you can test it with sine waves of various frequencies at first with single degrees of freedom and then with mathematical models of multi-degree-of-freedom systems by performing dynamic analyzes in the time domain, I know because I did it when I write my master's thesis). At least 10-15 cycles at a fixed frequency, for example, if the 1st period of the building were 0.7 seconds, it would take 7 to 10.5 seconds. There is no such seismic wave (by the way, just because I haven't seen it doesn't mean it doesn't exist
There is a market view that the X and Y direction periods of the building should be close to each other. (I haven't come across anything scientific.) What do you say about this? If we minimize the A1 torsional irregularity, would it be a problem if the periods are not close? Assuming that the earthquake does not always affect the X and Y directions perpendicular to each other, is this a reasonable approach? Or does it mean nothing?