The Dome of Santa Maria del Fiore in Florence:

Transcription

1 The Dome of Santa Maria del Fiore in Florence: Historical, geotechnical and structural studies for its conservation

2 A MULTIDISCIPLINARY TEAM: M. Coli Geo-Engineer, University of Florence M. Ripepe & E. Marchetti Geophysicians, University of Florence C. Blasi & F. Ottoni Architects, University of Parma G. Bartoli & M. Betti Structural Engineers, University of Florence The researches were developed with: the cooperation of the Management and Technical Staff of the Opera del Duomo of the Santa Maria del Fiore Cathedral the supervision of the Soprintendenza per i Beni Architettonici, Paesaggistici, Storici, Artistici ed Etnoantropologici per le Provincie di Firenze, Pistoia e Prato

3 MAIN POINTS: 1. BRUNELLESCHI S DOME GEOMETRY, STRUCTURE AND MATERIALS OF THE DOME MAIN CRACKS AND DAMAGES MAIN HYPOTHESES MADE MONITORING SYSTEMS (HISTORICAL, ANALITICAL AND DIGITAL) SEISMIC CHARACTERISATION S ANALYSIS MADE SO FAR

4 BRUNELLESCHI S DOME 1. THE DOME BRUNELLESCHI ( ) CONCEIVED AND VAULTED THE CUPOLA IN THE YEARS IN THE SHAPE APPROVED IN THE YEAR 1367 BRUNELLESCHI WAS ABLE TO VAULT THE CUPOLA SELF-SUSTAINING, WITHOUT SCAFFOLDING FROM THE GROUND THE CUPOLA WAS BUILT UP BY 48 SKILLED WORKERS WITH AN AVERAGE INCREASE OF 2.5 m/y AND ABOUT 20 BRICKS DAILY PUT ON PLACE FOR WORKER

5 WORKSHOP ATC19 BRUNELLESCHI S DOME I. GEOMETRY AND STRUCTURE 1. THE DOME TWO DOMES (INNER AND OUTER) STRUCTURALLY LINKED BY 24 RIBS (1 AT EACH CORNER 2 IN EACH SAIL) AND TRANSVERSAL ARCHES AT THE CORNERS OCTAEDRAL DOME BASED ON FOUR PILLARS AND FOUR LARGE ARCHES

6 BRUNELLESCHI S DOME I. GEOMETRY AND STRUCTURE A CIRCONFERENCE IS INSCRIBED IN THE OCTAEDRON 1. THE DOME A CATENARY IS INSCRIBED IN THE DOME Giovanni di Gherardo da Prato, 1424 THE CUPOLA HAS DIFFERENT CURVATURES FOR INTRADOS AND EXTRADOS INTRADOS: POINTED FIFTH ARCH EXTRADOS: POINTED FOURTH ARCH THE SAIL SURFACES ARE CILINDERS WITH ELLIPTIC SECTION

7 BRUNELLESCHI S DOME I. GEOMETRY AND STRUCTURE 1. THE DOME THE CORDA BLANDA (SLACK CABLE) DISPOSITION OF THE BRICKS PERMITS THEIR CONICAL AND CONTINUOUS ORIENTATION, WITHOUT ANY DISCONTINUITIES IN THE CORNERS THE STRUCTURE OF ROTATIONAL DOMES IS RECALLED THE RECURRENT COURSES OF VERTICAL BRICKS DEFINE A SPINAPESCE (HERRING BONE) PATTERN CONVERGING AT THE CENTRE OF THE DOME AT EACH BRICK LAYERS AT SPINAPESCE RESEMBLES A PLATBAND SETTING

8 BRUNELLESCHI S DOME I. GEOMETRY AND STRUCTURE 1. THE DOME IN ORDER TO CONTRAST THE THRUST FORCES OF THE CUPOLA BRUNELLESCHI PUT IN PLACE ONE WOOD CHAIN AND THREE STONE CHAINS OF STRONG MACIGNO CLAMPED WITH IRON (THEIR EXACT EMPLACING PATTERN IS NOT KNOWN)

9 BRUNELLESCHI S DOME II. FOUNDATIONS AND MATERIALS 1. THE DOME water table Bedrock sands Vs 120 m/s debris gravels Vs 400 m/s Vs > 1,200 m/s GEOLOGICAL SETTING OF SANTA MARIA DEL FIORE CATHEDRAL COMPLEX THE BLACK LINE RESEMBLE THE ENCUMBRANCE OF THE FOUNDATIONS

10 BRUNELLESCHI S DOME II. FOUNDATIONS AND MATERIALS PIETRAFORTE: THIS STONE WAS USED FOR THE MANSORY OF THE TAMBOUR, ITS OVER-STRUCTURE AND THE BASE OF THE CUPOLA MARBLE: WHITE MARBLE WAS USED IN ORDER TO GIVE WEIGHT TO THE RIBS AND THE LANTERNA BRICKS: BRICKS EXPRESSLY MADE IN SPECIAL SIZES WERE USED FOR THE MASONRY OF THE EIGHT SAILS MACIGNO: THIS STONE WAS USED TO BUILD THE THREE STONE-CHAINS AND THE TOP CLOSING RING ( SERRAGLIO ) BRUNELLESCHI SUPERVISED THE MATERIAL TO BE USED, THEIR QUALITY, QUANTITY AND SIZES AND WHERE THEY HAD TO COME FROM 1. THE DOME

11 THE DAMAGE CRACK PATTERN OF THE DOME 1. THE DME A SEVERE CRACK PATTERN - MAINLY CONCENTRATED ON THE DOME -STARTEDINTHE LATEST STAGE OF THE CONSTRUCTION, BEFORE THE LANTERN WAS FINISHED, AFTER A STRONG EARTHQUAKE, AND HAS BEEN INCREASING OVER THE TIME, AROUSING ALARM

12 CRACK PATTERN SURVEY AND SCHEME 1. THE DME A: MAJOR VERTICAL PASSING CRACKS (ON BOTH THE DOMES) AT THE CENTER OF EVEN SAILS ( ), 6.5 cm (n.4 6) and 2-3 cm (n.2-8) B: MAJOR CRACKS ON THE TAMBOUR, IN ODD SAILS ( ) AT 60 TO THE HORIZONTAL, FROM THE CENTRAL OCULI C: VERTICAL NON PASSING CRACKS ON THE CORNERS, AT THE INTRADOS OF THE INNER DOME B D C D C B A D: SOME MINOR CRACKS, (1-2 mm) AT THE CENTER OF THE ODD SAILS, ON THE INTRADOS OF THE INNER DOME MINOR CRACKS ON THE SEMI-DOMES, THE TRIBUNE AND THE NAVE OF THE BASILICA

13 CRACK PATTERN SURVEY AND SCHEME A: MAJOR VERTICAL PASSING CRACKS (ON BOTH THE DOMES) AT THE CENTER OF EVEN SAILS ( ) 1. THE DME A DIMENSION OF MAIN CRACKS: SAILS 4 6: 6.5 cm - PRESENT SINCE XVI Century SAILS 2 8: 2-3 cm - AFTER 1785

14 CRACK PATTERN SURVEY AND SCHEME C: VERTICAL NON PASSING CRACKS ON THE CORNERS, AT THE INTRADOSX OF THE INNER DOME 1. THE DME C C

15 CRACK PATTERN SURVEY AND SCHEME B: MAJOR CRACKS ON THE TAMBOUR, IN ODD SAILS ( ) AT 60 TO THE HORIZONTAL, FROM THE CENTRAL OCULI D: SOME MINOR CRACKS, (1-2 mm) AT THE CENTER OF THE ODD SAILS, AT INTRADOS OF THE INNER DOME D 1. THE DME MINOR CRACKS ARE ON THE SEMI-DOMES (E), THE TRIBUNE (F) AND THE CENTRAL NAVE (G) B

16 POSSIBLE CAUSES OF DAMAGE THREE DIFFERENT HYPOTHESES 1. THE DME I. DOME THRUST - DEAD WEIGHT V. Viviani (1694) A. Chiarugi, M. Fanelli(1985) II. DIFFERENTIAL SETTLEMENT A.Cecchini (1694) L. Ximenes (1735) III. THERMAL VARIATIONS P.L. Nervi ( )

17 HISTORICAL MONITORING DIRECT AND INDIRECT INDICATIONS TEH DOME OVER CENTURIES, DIFFERENT INSTRUMENTS HAVE BEEN INSTALLED ON THE DOME: MARBLE SPIES, STONE ALLOYS, IRON WEDGES, UP TO THE MODERN MONITORING SYSTEMS AVERAGE INCREASE OF ABOUT 5.5 mm/100y 1935

18 THE MILITARY GEOGRAPHICAL SURVEY MONITORING HIGH PRECISION GROUND LEVELLING PERIODICAL SURVEY (IGM) 1. TEH DOME

19 THE MECHANICAL SYSTEM 22 INSTRUMENTS (1955 to date) nave sail 1. TEH DOME 22 DEFORMOMETERS (Dn) REGISTER CRACK WIDTH VARIATIONS FOUR TIMES A YEAR (214 instrument at present time)

20 THE DIGITAL MONITORING SYSTEM (ISMES) 166 INSTRUMENTS (January 8 th 1988 to date) 1. TEH DOME 72 DEFORMOMETERS Dfn-mm - prec. +/ mm (every 6 hours) 60 THERMOMETERS TMn-mm-TAn-mm - prec. +/ INCLINOMETERS at the centre of each sail 8 LEVELLOMETERS 2 PIEZOMETERS under sail n.4 and the nave

21 THE DEFORMOMETERS 72 DISPLACEMENT TRANSISTORS (DFn-mm) 1. TEH DOME PLACED AT FIVE DIFFERENT LEVELS ON: - INTRADOS INNER DOME - EXTRADOS INNER DOME - INTRADOS OUTER DOME e.g. SAIL n.4 (n.14) SAIL n.6 (n.10)

22 THE PLUMB-LINES CLOSE TO EACH CORNER 1. TEH DOME 8 PLUMB-LINES ON THE 8 CORNERS OF THE DOME EACH PLUMB LINE IS INTERCEPTED AT THREE DIFFERENT LEVELS (FIRST PLATFORM, LOWER TAMBOUR, GROUND) BY THREE TELECOORDINOMETERS (xy coordinates)

23 HYDRAULIC LEVELING SYSTEM 8 LEVEL MEASUREMENT VESSELS 1. TEH DOME - 8 LEVELLOMETERS - BELOW EACH OCULI, CONNECTED BY A HYDRAULIC CIRCUIT ISOLATED FROM THE INTERNAL AMBIENT - 2 PIEZOMETERS - ONE UNDER THE SAIL N. 4 AND ONE BELOW THE NAVE, IN ORDER TO MONITOR THE VARIATION OF THE WATER TABLE ( STABLE SINCE THE XV CENTURY!)

24 THE THERMOMETERS 56 INSTRUMENTS 1. TEH DOME THEY MEASURE MASONRY AND AIR TEMPERATURE (TMn-nn AND TAn-nn) IN THE TWO DOMES (INNER AND OUTER) ON EACH SAIL, AT THE SECOND PLATFORM LEVEL (+/ C PRECISION)

25 SOME RESULTS FROM MONITORING HYPOTHESIS I. THE DOME THRUST HYPOTHESIS I. DOME THRUST - DEAD WEIGHT V. Viviani (1694) A. Chiarugi, M. Fanelli(1985) 5 mm/100y 1mm/100y ENCIRCLING SCAFFOLDING FOR RESTORATION ( ) 1. TEH DOME

26 SOME RESULTS FROM MONITORING HYPOTHESIS II. DIFFERENTIAL SETTLEMENTS HYPOTHESIS II. DIFFERENTIAL SETTLEMENTS A.Cecchini (1694) L. Ximenes (1735) 1. TEH DOME DATA RECORDED BY THE 8 LEVEL METERS INSTALLED NO SIGNIFICANT VARIATIONS AS CONFIRMED BY THE IGM TOPOGRAPHIC LEVELING THE HORIZONTAL DISPLACEMENTS (X AXIS DIRECTION) RECORDED BY THE THREE TELECOORDINOMETERS INSTALLED, AT DIFFERENT LEVELS, ON SAIL 4 (SAIL 3 SIDE)

27 SOME RESULTS FROM MONITORING HYPOTHESIS III. THE DOME BREATH EXPERIMENTAL DATA OF DF4-06 ( ) SHOWS A YEAR-PERIODICITY DUE TO THE TEMPERATURE EFFECT HYPOTHESIS III. THE DOME S BREATHING P.L. Nervi( ) 1. TEH DOME CRACK OPENINGS CHANGE ACCORDING TO THE TEMPERATURE, BUT THERE IS NOT A TREND TO ENLARGEMENT OF THE CRACKS DUE TO TEMPERATURE

28 CAUSES OF DAMAGE 1. TEH DOME I. DOME THRUST - DEAD WEIGHT V. Viviani (1694) A. Chiarugi, M. Fanelli(1985) II. DIFFERENTIAL SETTLEMENT A.Cecchini (1694) L. Ximenes (1735) III. THERMAL VARIATIONS P.L. Nervi ( )

29 SEISMIC CHARACTERISATION DOME SEISMIC RESPONSE SPECTRAL RESPONSE: THE CUPOLA AMPLIFIES FREQUENCIES HIGHER THAN 0.5 Hz THE PEAK AT Hz IS GENERATED BY THE OCEAN MICROSEISMS THE CUPOLA RESONANCE PERIOD IS AT 1.75 Hz 1. TEH DOME spectral density Power Spectral Density Amplification Period

30 SEISMIC CHARACTERISATION DOME SEISMIC RESPONSE SEISMIC SEQUENCE OF MARCH 1 ST, 2008 IN MUGELLO AT A DISTANCE OF 35 km 1. TEH DOME THE RECORDINGS OF THE ML4.2 EARTHQUAKE REVEAL THAT THE CUPOLA ITSELF SEEMS TO SLIGHTLY REDUCE THE SEISMIC AMPLITUDE COMPARED TO THE REST OF THE CATHEDRAL

31 DOME S NUMERICAL MODELS THE FIRST MODEL (Chiarugi, Giuseppetti, Fanelli, 1980) 1. THE DOME

32 THE CURRENT NUMERICAL MODEL (Bartoli & Betti, ) PRELIMINARY ANALYSIS WORK IN PROGRESS IMPROVED GEOMETRY (REFINEMENTS HAD TO CONSIDER THE FUNDATIONS AND THE INTERACTION WITH THE GROUND, AND THE RIGHT PHYSICAL MECHANICA DATA OF THE DIFFERENT MATERIALS) SOLID MODEL: 3D ELEMENTS (SOLID45) AND GAP ELEMENTS (CONTACT52 & LINK10) TO MODEL CRACKS 1. THE DOME STATIC AND DYNAMIC IDENTIFICATION (CALIBRATION TO FIT THE EXPERIMENTAL RESULTS) GEOMETRIC NON-LINEAR ANALYSES (CONSTRUCTION HISTORY AND ITS STRUCTURAL EVOLUTION) NON-LINEAR ANALYSES PERFORMED TO ASSESS POTENTIAL SEISMIC VULNERABILITY TO BE IMPROVED ON THE BASE OF THE SEISMIC CHARACTERISATION THE ROLE PLAYED BY THE LANTERN HAD BEEN SIMULATED AS AN EXTERNAL WEIGHT

33 AN ITERATIVE PROCEDURE WHICH IS THE MOST SUITABLE HYPOTHESIS? HYPOTHESIS I. DOME THRUST - DEAD WEIGHT V. Viviani (1694) - A. Chiarugi, M. Fanelli(1985) 1. THE DOME A C THE ANALYSIS SHOWS THAT DUE TO THE SELF-WEIGHT AND THE GEOMETRY OF THE CUPOLA THE FIRST CRACKS TO APPEAR ARE THE TYPE A CRACKS (FIGURE ON THE LEFT) THE ARISING OF THESE CRACKS MODIFIES THE CUPOLA AND FACILITATES THE DEVELOPMENT OF TYPE C CRACKS

34 THE DYNAMIC IDENTIFICATION THE EFFECTS OF CRACKS 1. THE DOME THE COMPARISON OF THE RESULTS OF THE UNDAMAGED MODEL WITH THE DAMAGED ONE OUTLINES THAT THE EFFECTS OF THE CRACKING ARE FUNDAMENTAL FROM A DYNAMICAL POINT OF VIEW

35 THE DYNAMIC IDENTIFICATION THE EFFECTS OF CRACKS LOAD DIRECTION 1. THE DOME TENSILE STRESSES COMPRESSIVE STRESSES THE EFFECTS OF THE SEISMIC LOADS HAVE BEEN EVALUATED THROUGH THE APPLICATION OF TWO SYSTEMS OF ORTHOGONAL FORCES LYING IN HORIZONTAL PLANE (PUSHOVER ANALYSES)

36 SIMULATION OF COLLAPSE THROUGH NUMERICAL MODEL DISPLACEMENT STEP=8 SUB =53 TIME=7.53 DMX = JUL :42:28 DISPLACEMENT STEP=8 SUB =53 TIME=7.53 DMX = JUL :59:32 1. THE DOME Z Y X MODELLO S.M.F. DISPLACEMENT STEP=8 SUB =53 TIME=7.53 DMX = JUL :59:18 MODELLO S.M.F. A LARGE INCREASE IN THE OPENING OF CRACKS A STRONG EARTHQUAKE (ML VIII) COLLAPSE CONFIGURATION ENVISAGE THE ROLE OF AN ENCIRCLING AT THE BASE OF THE DOME MODELLO S.M.F.

37 REMARKS: 1. THE CAUSE OF THE CRACKS IN BRUNELLESCHI S CUPOLA SEEMS TO BE RELATED TO ITS THRUST 2. THE ENCIRCLING SCAFFOLDING PUT IN PLACE FOR RESTORATION PURPOSES IN THE YEARS SUGGEST THE POSITIVE ROLE PLAYED BY AN ENCIRCLING OF THE DOME THIS POINT IS UNDER CONSIDERATION FOR AN EXPERIMENTAL RUN IN THE NEAR FUTURE 3. A STEEPER DOME WITH THE WOOD AND THREE MACIGNO STONE ENCIRCLING CHAINS CONCEIVED BY BRUNELLESCHI CONTRIBUTED TO THE CONTAINMENT OF THE THRUSTING FORCES BRUNELLESCHI WAS GREAT! 4. FOR BRUNELLESCHI A KEY ROLE FOR THE DOME STABILITY WAS PLAYED BY THE LANTERNA THE 1453 EARTHQUAKES OCCURRED BEFORE THE COMPLETATION OF THE LANTERNA AND THE FIRST CRACKS APPEARED THIS POINT MUST BE INVESTIGATED IN DETAIL BY FURTHER NUMERICAL ANALYSIS

38 Massimo Coli, Marcello Brugioni & Giovanni Montini Thanks for your kind attention and see you in Florence UNESCO Cultural Heritage site