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

state and deformation state when an earthquake occurs.Although elastic analysis has been conventionally employed,advancements in computer data processing capability nowenable the application of the elasto-plastic analysis.LV1 is generally applied for evaluation of seismicrisks of entire historic districts and is not employedfor reinforcement designing. LV2 is used for seismicanalysis and reinforcement designs in partial repairs andreinforcement, with LV3 applied for supplementary studies.In large-scale repairs and reinforcement, studies with bothLV2 and LV3 are made, or seismic performance of the entirestructure is confirmed by studying all possible collapsemechanisms that may affect the structure to be analyzed.Also, in densely built groups of buildings or complexbuildings that have undergone multiple alterations andadditions, there are cases where first, an elastic analysis LV3of the entire area or building is undertaken to understandhow each part of the complex affect one another and then,certain parts are individually studied in detail throughelasto-plastic analysis LV2 or LV3.In Italy, limit analysis employing partial modeling basedon the collapse mechanism is often used. This appears tobe due to the fact that partial collapse has often occurredin past earthquakes and as a result, survey and researchfocusing on collapse mechanisms have been advanced. Onthe other hand in Japan, analysis of the entire structure,which corresponds to LV3 as explained above, is themainstream approach. The reason for this is because in thecase of wood-frame cultural property structures, the mostdangerous form of building damage in past earthquakesis that of the entire structure collapsing, as in cases wherethe whole roof falls to the ground. In both countries, themajor form of structural damage that can be seen in themasonry or wood-frame cultural property buildings owingto the structural properties of each form of construction canbe said to have influenced methods for analysis as well aspreventive methods.3.4. Anti-Seismic ReinforcementIn this section, representative reinforcement methods thatare employed today for extant buildings will be dealt with.First, there is the traditional reinforcement method of usingtie beams for reinforcing connections in walls intersecting atright angles or places where the floor or roof structures areattached to the walls. By installing them onto walls that faceone other, walls can be prevented from leaning outwardswhich would disrupt the balance among the above-mentionedconnections. Tie beams are often employed today as aminimum and highly effective reinforcement method. Othermethods include installation of stainless steel bands andother materials onto the outer or inner perimeter of buildingsfor the same purpose or binding the ends of floor beamsonto perimeter walls with metal fittings. For preventing outof-planefailure of walls, a traditional technique of installingbuttresses was also seen (photo 6).In walls, for recovery of the original performance orincreasing performance, as a method other than thetraditional way of reconstructing brickwork in cracked ordamaged areas or joint repointing, the injection method isoften employed. Consideration is given to select an injectionmaterial with similar physical and chemical properties asthe material characteristics of the extant wall. There arealso methds which involve horizontal pinning to solidifywalls composed of multiple layers, insertion of bars madeof stainless steel or fiber-reinforced plastic into brick jointsfor crack prevention, or the jacketing system in which thebrick wall is sandwiched between reinforced concrete layersfrom the outside and inside. The jacketing method requiresattention regarding durability or excessive increase in rigidityor weight.For solidifying buildings by reinforcing horizontalelements such as floor or roof structures, there is a methodof layering thick boards on the wood frame floor attachingfigure 1Typical collapse mechanism for church construction（partially cited from the Cultural Property Guidelines）photo 6Traditional reinforcing method（installing buttresses behind the facade )39