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

actual structure were reflected in the model to be used forfinite element analysis, by adjusting the parameter of themodel through comparison of oscillation characteristics andobservation results.Numerical analysis was executed concentrating onthe facade and the central dome, in both the span andlongitudinal directions, as areas that were highly vulnerableto collapse in times of earthquakes based on results ofdamage surveys and typical collapse mechanism seen inchurch structures. Each area was considered to be a rigidbodyand limit analysis was applied; also, each area wasverified by static load analysis, replacing each area byan elasto-plastic model under the finite element analysismethod. Finally, the results were compared and seismicperformance was studied (figures 4, 5).For example, in the longitudinal direction of the facadearea, several patterns of the mechanism of this area tocollapse forward from the building were presumed anda seismic factor (the ratio of the velocities at the start ofcollapse mechanism and ground acceleration) for each ofthe patterns was calculated and compared. Also, the samearea was modeled following the finite element methodand a nonlinear analysis was executed. The relationshipbetween load and deformation was sought, locations ofcracks appearing on deformations were checked, and theactual locations of cracks and results obtained from analysissurveys were found to match well. Also, a comparison ofthe results of numerical analysis revealed that among thecollapse mechanisms presumed through limit analysis, therewere those that roughly matched the results of finite elementanalysis, verifying the accuracy of the different analyticalmethods.From these studies, it became clear that on the facade,seismic force became exceedingly large due to the belltower on top and at places where additions have been madeand cracks tended to appear on the connective elements;also on the central dome, the vaulted ceiling of the navewas structurally brittle due to its large span as well as thebending deformation caused by the dome on top. Based onthis result, in order to strengthen the connection betweenthe bell tower on the facade and the main structure, stainlesssteel tie bars in addition to the extant tie bars were newlyinstalled in several bands in the span and longitudinaldirection. In the upper areas of the vaulted ceiling, archbeams (buttresses) were installed to increase structuralperformance of the ceiling as well as to strengthen theconnections between the walls. Furthermore, so as toprevent partial collapse of the apse, in the upper areas ofthe wall of the apse along the circumference, stainless steelrods were placed in polygonal forms. The effects of thesereinforcements have been quantitatively confirmed throughlimit analysis of the collapse mechanism before and afterreinforcement.figure 2Map of cracks on the vaulted ceiling of the nave(a) 9 - 13th century (b) 13 - 15th century (c) 15 - 16th century (d) 17 - 19th centuryfigure 3Structural transition of Reggio Emilia Cathedral41