ブックタイトル「煉瓦造建造物の保存と修復」英語版

概要

「煉瓦造建造物の保存と修復」英語版

change the structure, in other words when you don’t addnew floors or new portions.In Italy, the words“retrofit”and“improvement”areused with the meaning of“reinforcement to meet seismicstandards”and“reinforcement to improve seismicresistance, how little it may be”respectively. Therefore,these expressions can be used as is, or can be rewordedwith“standard-satisfying reinforcement”and“performanceimprovingreinforcement.”The planned revision can beunderstood as altering the figure to be aimed at in seismicresistance of retrofitted structures to 0.8 of that for newconstruction, from what used to be the equivalent of thevalue required for new construction.Revisions make our code safe and improved structuresbecome safer than it was before intervention. The effects ofimprovement are clear and thus it will not be necessary togive specifics of to what extent improvement needs to bemade. And the decision as to how much the improvementwill be required depends on the building use and theproperty owner’s opinions on the architectural design.If the safety level reached through intervention does notmeet the standards for the building use, it is recommendedto change the use. This is typically seen in schools whereverifications are made for improving the building. If itinvolves a historic building that does not allow retrofitting,it becomes necessary to decide whether to maintain thebuilding use as a school or take measures to move thestudents to another building and change the use of thestructure.This is the rule, but as I have been touching upon thesubject of qualitative judgment, it is intended for qualitativevalues to be used for determining the seismic capacity.Capacity is normally derived from calculations, and indealing with existing structures, qualitative judgments needto be adopted for determining the capacity, not only fromcalculations. Even so, I make calculations as well knowinghow rough the calculations are, so in any case, they aresubjected to assumptions.For example, what is the seismic resistance of the masonrybuildings I have shown you photos of? Our codes give rangesor values for masonry typologies, but there are many otherpossibilities to choose from. These values do represent theircharacteristics, but are subjected to uncertainties. Therefore,the level of uncertainty that is connected with interventionof existing buildings, especially historic buildings, is very,very high. So it is an illusion that precise calculations can bemade using determined parameters. So, in conclusion, I’d liketo urge you to use qualitative judgment for determining theactual capacity of a building, in which there is a possibilityfor design.Yohei EndoThe figures of 0.25 and 0.35 are the velocity on base rock.The ground is positioned above the base rock, and therefore,difference in conditions will make the value range from 0.25to 0.8. By different grounds (categorized into A, B, and C),it can range from 0.25 to 0.8. 0.25 is based on the value onthe ground and when actual calculations are made, groundconditions affect these figures. This is what ProfessorModena has just explained.Claudio ModenaThe administration has set guideline principles for each ofthe four classes of seismic hazards.I’d like to introduce to you a different point of view. Asitems that need to be confirmed, there are the four limitstates: 1) Limit states of operativity (the reference periodis very short and thus, the return period is very short aswell), 2) limit state of damage, 3) limit state of safety ofthe human life, and 4) limit state of collapse. I wantedto mention that if all of these limit states can be studied,very accurate results could be obtained. These studiesare undertaken on very large earthquakes, which mayoccur during the lifetime of a building. Therefore, this is adifferent problem altogether.This is the three response spectra for the threecomponents of the actions. Generally, the horizontalcomponent is the most important. Under the code, forany scale, the expected limit state value of peak groundacceleration is a figure, for example 0.6, which is notactually a figure given in the code.In this map, you enter the coordinates, and at that point,the code determines that the peak ground acceleration,which corresponds to the limit state of safety of human life,is 0.33. This is the maximum.In all areas of Italy, the return period of 30 to 2,000 yearswas assumed and the possibility of earthquakes occurringwithin a given period of time has been determined for eachof the return periods.Mikio KoshiharaI have a question regarding the coefficients that areapplied for historic structures and traditional structures.For historic structures, are different coefficients from thoseused for new construction applied for the estimated scale ofearthquakes?Claudio ModenaExisting historic building are not designed to endure thesame forces as are required in new construction. It is not76Chapter 5 Discussions among all participants