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

them together with dowels or installing braces onto thefloor beams and roof beams. These methods are requiredto reinforce the above-mentioned connection between thewalls and floor or roof structures. The method in which thewood floor structure is reinforced with or replaced with areinforced concrete floor slab also is noted to be aware ofexcessive increase in rigidity or weight.Vaulted ceilings are also areas prone to earthquake damageand they have traditionally been reinforced by installing tiebeams or buttresses where the upper surface of the ceilingand walls meet. There are now other methods of preventingdamage in brittle areas by attaching carbon fiber or fiberreinforcedplastic with epoxy resin (photo 7).In Italy, as has been earlier explained, from havingexperienced failure of modern reinforcement methods in pastearthquakes, focus is placed not only on modern methodsbut also on traditional technique including installation of tiebeams and buttresses.On the other hand in Japan, there is a tendency to notemploy traditional methods such as addition of penetratingbeams or earthen walls that would be difficult to distinguishfrom the original structure; this would conflict with theleading preservation principle aimed at protecting buildingsin the original appearance. Thus, modern reinforcementtechniques are the mainstream in that they are highlyeffective and small-scaled, while being easily recognizable.From this point of view, it can be said that the selectionof reinforcement materials is possibly influenced by thepreservation policies of each of the two countries.4．Present Anti-Seismic Measures4.１. Reggio Emilia CathedralReggio Emilia is a city located in northern Italy. Thecentral portion of its cathedral was constructed in the 9thcentury, to which countless additions and alterations havebeen undertaken resulting in the complex structure we seetoday. It is mostly made of brick masonry (photo 8). In thisarea, numerous earthquakes have occurred in the past, mostrecently in 1996 and 2000, and the cathedral has beenrepeatedly damaged.Firstly, from damage surveys, it was discovered thatcountless cracks were concentrated in the vaulted ceiling ofthe nave upon which the central dome sits and the facade onwhich the bell tower stands. Cracks were found on columnsof the turret above the dome as well (figure 2).Historical surveys on the transition of the structure sinceconstruction revealed the areas built in different periodsand how they were connected to one another (figure 3). Thepresent facade was added in the 13th century together withthe bell tower and in the 15th century, the upper portionof the bell tower was built. The present central dome wasrebuilt in the 17th century, replacing a dome constructed inthe early years.Additionally, so as to clarify the material characteristics ofareas constructed in each age, ultrasonic wave propagationrate was measured in each area. The results indicated thatmaterial properties of the structure was overall sound,although some variances were found in areas that hadbeen repaired in the past. Also, in some walls, differentpropagation rates were seen on the wall surface and onthe inside which suggested that the wall was made up ofmultiple layers. Propagation rates also provided standardsfor making decisions in the application of limit analysis,whether the partial modeling can be assumed to be a rigidbody.For determining oscillation characteristics, micro-tremorswere observed, concentrating on areas such as the facadeand the central dome. From observation results, naturalfrequency and oscillation mode were obtained to verifyrigidity and weight as well as the condition of connectionsin each of the areas. Additionally, characteristics of thephoto 7 Reinforcement with contemporary material（reinforcingthe upper side of vaulted ceiling by attaching carbon fiber etc.（anexperimental case））photo 8Reggio Emilia Cathedral40Chapter 4 Earthquake-Proofing Measures for Masonry Structures in Italy