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

Discussions among all participantsDaijiro KitagawaYou mentioned that problems began to be seen inreinforcement with reinforced concrete undertaken in the1970s. Could you please give specific examples of the issuesthat have emerged?Claudio ModenaI have drawn some examples of some, not all, of the typicalfailures. For example, after Friuli Earthquake in 1976, the boxtheory was established. Here, they replaced the timber floorstructure and the roof structure with reinforced concreteelements. But there were several issues connected with it.There is a great difference between the rigidity of reinforcedconcrete and masonry, and the connections between thesedifferent materials were not appropriate. Therefore, theseismic response was not of a favorable condition. In manycases, homogeneity in seismic response was not achieved.There are problems regarding construction as well. Forexample, in order to introduce a reinforced concrete floorslab into a masonry structure, it is necessary to cut into apart of the wall. Without this, the load of the floor will notbe transferred well to the walls. As seen in the photos, thereinforced concrete floor structure remained unharmed andcaused out-of-plane damage to the brick walls. Particularly inL’Aquilla, such effects were highly prominent. These buildingshad obeyed the codes at the time, but the reinforced concretestructures then were not adequately designed that theycollapsed. Here almost all churches that had their timber roofstructures altered to heavy reinforced concrete collapsed.Because the design of details and condition of reinforcementbars were not appropriate, the very heavy structures clashedwith one another to destruct the buildings.There are two interesting cases related to this topic.white board writing 1(white board writing 1) One is of a cathedral of whicha portion of the reinforced concrete beam became loosefrom the structure and flew off, like a jet plane or a missile,clashing into a building nearby. While on the other hand,damage by the earthquake to the wooden church on the otherside was little. What was made clear by this incident is thatthere was a basic problem in the reinforcement method; itwas prevention of out-of-plane collapse that was necessaryinstead of increasing rigidity of the floor structure to changethe structural response. Under the present laws, it is regardedeffective to increase rigidity of the timber floor structure andconnect the floor to the walls employing a highly reliablemethod.The second example is a large building in the same city inwhich the central part of the roof structure was replaced withreinforced concrete while the original wood frame structureon both sides were retained. Here, the wood frame structurecollapsed and the rest remained in place. From these cases, Ifelt that the significance of leaving the entire structure as awhole was made clear.white board writing 2(white board writing 2) It is not as clear, but from the cases ofwood structures which I introduced for explaining the collapsemechanism, how loads are transferred through the structurecan be accurately confirmed. As long as the walls are kept inplace, that is enough.In L’Aquilla, there is a very simple traditional technique,where wood members protruding slightly from the structuralbody act as anchors. They function to maintain the equilibriumamong the walls and wood members. Such simple measureswere effective for preventing collapse.(white board writing 3) Atanother church, there wascollapse due to the structuralbody being pushed out, inducingclashing which resulted incollapse. At this church, a partof the walls was removed forcreating a room in the 19thwhite board writing 3 century. On top of this wallwas placed a heavy reinforcedconcrete beam. The bell tower and the structural body collidedwith one another, making the bell tower destruct the church.74Chapter 5 Discussions among all participants