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

Earthquake Damage to Brick Masonry Structures(slides 6-7) Mortar used in brick masonry structures israther weak, but here, the building has completely collapsed.Poor maintenance and weak connections between the wallsand floors, together with other factors induced this severedamage. There was response as a structure and a clearstructural behavior was observed. Cracks appeared, insteadof collapse of the masonry itself.(slide 8) But even with brick masonry, if it is structurallyweak, collapse similar to that of rubble stone masonry canbe seen.(slide 9) In Italy, there are many masonry bridges. Thephoto shows a typical collapse of a bridge of arches andvaults. Generally, bridges are structurally well-made, butsimilar damage can be seen in the masonry bridges of therailroad system and this is now a major concern. From theseexamples, it can be seen that there are three ways in whichmasonry structures collapse. First, when the structure itselfis weak and the structural response is low, it will resultin collapse or crumbling of masonry. Secondly, if there issufficient strength in the masonry, the loss of equilibriumamong the different portions of the structure will lead toan intermediate way of collapsing, in which not the entirestructure, but only a portion of the masonry will collapse dueto lack of horizontal confinement. The third way of collapseoccurs when there is sufficient strength in the connectionsbetween the walls and floors, and structural response as amasonry structure can be seen with cracks appearing. Ofcourse, it is best for cracks to not form, but if they shouldappear, for the building to not collapse is the best type ofdamage.Ensuring Structural Safety:Conflicts and ComplementaritiesBased on the above, it is necessary as a countermeasure tocarefully observe first masonry structures and improve theirquality, then the effectiveness of connective elements - suchas those between walls or walls and areas that maintain therigidity of horizontal plane. Lastly, their strength as masonrystructures needs to be confirmed, particularly tensilestrength for determining the level of durability that wouldallow the best type of collapse.(slide 10-12) As has been explained early on, in the past,there were conflicts in assuring safety and preservation.When masonry structures were starting to be dealt with,their characteristics had not yet been well understood. Upto 20 to 30 years ago, engineers in Italy were not educatedin designing masonry structures and they did not considerProf. Eng. Claudio ModenaDepartment of Civil, Environmental and Architectural EngineeringUniversity of Padova, ItalyProf. Eng. Claudio ModenaCriteria of interventionSM IngegneriaVAULTTRANSVERSE CRACKING: ANTIMETRICAL COLLAPSE KINEMATISM WITH 4 HINGESLOCALIZATION AND CAUSESAlternating cracking of the arch at intrados and extrados in four pointslocated generating a four-hinges mechanism that affects the single span.This is a type of damage that can occur in any kind of bridge, in particularit is frequently observed in the thin arches and segmental vaults. Loss ofbalance derived from strong traffic loads or horizontal / asymmetricseismic activities not compatible with the arc dimensioning. The presenceof deteriorated masonry facilitates the formation of this mechanism.FPPOSSIBLE ASSOCIATED DAMAGESDiagonal cracking along the abutment and the spandrel,Material failure for reaching the limit compression stress.STRUCTURALCONSEQUENCESIndex of the imminentcollapse of the structureConnected to point 1, the following critical issues became graduallyclear :? the inadequacy of the tools have been adopted to“interpret”the“structural performances”of masonry constructions;? the inappropriate use of technologies well adapted for newstructures but not for repairing/strengthening historic masonrystructuresslide 9slide 11Prof. Eng. Claudio ModenaCriteria of interventionSM IngegneriaThe main reasons why conflicts soon arose were:1. the lack of knowledge on masonry structures, ignored by theengineering schools and code makers (studies started only after the1976 Friuli earthquake, and the first specific national code was issuedin 1987) ;2. the“ambiguities”of the definition itself of“structural safety”andof the way how its normally quantified, acceptable for the design ofnew structures , unacceptable when designing intervention on“existing”structures.slide 10Prof. Eng. Claudio ModenaCriteria of interventionSM IngegneriaConnected to point 2, more and more contradictory and sometimesmisleading appear such issues as:? the reference made to the“service life”, typically 50 years, to definethe intensity of the actions, when considering structures that alreadysurvived for centuries ;? the“conservative”approach of the conventional procedures used todesign new structuresslide 1249