University of Naples "Federico II" RETROFIT OF HISTORICAL MONUMENTS AND PRINCIPLES OF BASE ISOLATION (B.I.S.)

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1 University of Naples "Federico II" Department of Structural Analysis and Design RETROFIT OF HISTORICAL MONUMENTS AND PRINCIPLES OF BASE ISOLATION (B.I.S.) Prof. Antonello De Luca Professor of Structural Engineering Lessons: 14_ May 15, Flat arches retrofit and Architraves 2. Foundations retrofit

2 FLAT ARCHES AND ARCHITRAVES INTERVENTIONS

3 LIMIT ANALYSIS APPLIED TO THE MASONRY PORTAL Kinematic approach: all mechanisms HYPOTHESES (Heyman-1966): - NULL TENSILE STRENGTH; - INFINITE COMPRESSION STRENGTH; - SLIDING CANNOT OCCUR; governing mechanical parameters: Mechanism 1 Mechanism 2 Beam mechanism: WHEN? Storey mechanism: Mechanism 3 Mechanism 4 WHEN? A lot of algebra:.. boring but necessary

4 COURSE EXAMPLE Traditional retrofit: ties and substitution sostruzione

5 COURSE EXAMPLE Traditional retrofit: ties and substitution sostruzione

6 TIES AND INJECTIONS BEFORE SUBSTITUTION

7 TIES THROUGH CONNECTION TO SLABS

8 Substitution at lower levels: importance of shoring

9 Plan of substitutions: each wall in four periods

10 EXAMPLE MILL B MASONRY STRUCTURE PERDIFUMO (ITALY)

11 THE REINFORCEMENT WITH ARCHITRAVES

12 DOUBLE FRAMES SLAB DOUBLE CROSSED TIMBER SLAB Architrave

13 DOUBLE FRAMES SLAB DOUBLE CROSSED TIMBER SLAB Architrave

14 SINGLE FRAME SLAB DOUBLE CROSSED TIMBER SLAB Architrave

15 SINGLE FRAME SLAB DOUBLE CROSSED TIMBER SLAB Architrave

16 DOUBLE FRAMES SLAB SINGLE TIMBER SLAB Architrave

17 DOUBLE FRAMES SLAB SINGLE TIMBER SLAB Architrave

18 INTERVENTION 1 THE TIMBER SLAB REINFORCEMENT

19 FOUNDATIONS DAMAGE AND RETROFIT

20 THE CRACKS Ing. Cristoforo Russo Le lesioni dei fabbricati Classification of cracks (six classes): Foundations 1. Lesioni di rassetto (after building) 2. Lesioni di cedimento (cracks due to settlement) 3. Lesioni di rotazione (cracks due to rotation) 4. Lesioni di scorrimento (cracks due to sliding) 5. Lesioni per fenomeni endogeni (i.e. seismic cracks) 6. Lesioni di schiacciamento (Compression cracks)

21 TENSION CRACKS Tension stresses due to: Compression 2. Shear stresses due to settlement 2. Pure shear stress causes principal compression and tension stresses

22 TENSION CRACKS THE CRACK POINTING THE SETTLEMENT After the settlement After putting under stress

23 TENSION CRACKS The tension cracks due to the bending moment and to the rotational settlement have a varying width The principal compression and tension stresses having a direction rotating of 45 respect the shear stress

24 Damages in the masonry walls - Settlement damages Vertical settlement Cracks pointing the settlement high shear and bending stresses in the masonry beams

25 Damages in the masonry walls Cracks due to settlement i.e. settlement for the foundation rotation of the building wall on the right

26 Damages in the masonry walls Crack in the wall perpendicular at the wall with rotation It is influenced from transversal walls, openings, slabs and roofs. The openings assumes the rhombus shape: it is difficult to close the doors

27 MOTIVATIONS OF THE INTERVENTION IN FOUNDATION 1. Inadequacy of the foundation system in relationship to transmitted loads and soil resistance - insufficiency of the support surface - inside transformations - change of the slabs abutments - raisings - remarkable change of the use destination [in presence of superficial foundations] 2. Soil settlements

28 TECHNICAL PROVISIONS IN FOUNDATION Generally consists in: amplifications / integration of the existing foundation consolidation of the foundation grounds sub-foundation realization: Seismic improvement -superficial - deep (micro-piles) the interventions on the construction not to be behaved variations of the stresses on the soils and in general of the interaction building-soil Retrofit after the interventions it is necessary to respect the codes prescriptions Verifications: in Italy it is necessary to respect the prescriptions of the DM for foundations [i.e. for the safety factors]

29 TECHNICAL PROVISIONS IN FOUNDATION Superficial sub-foundation Applicable if: - modest depth - low loads - they require modest amplifications Amplifications with r.c. Preferable if: - the thickness of the existing foundation is remarkable - it is necessary great amplifications - necessary great deeps - the scarce quality grounds Obtained trough: Beams in adherence to the existing foundation - with connections Deep sub-foundations - generally with micro-piles

30 SUPERFICIAL SUB-FOUNDATION Approximate values of α Foundation in - Block masonry: α 3 -r.c.: α 5 - rubblework: α 10 h new /α h new Observations In correspondence of the intersections among the building walls a further widening should be foreseen, if the intervention is due to the vertical loads To appraise the necessity of the masonry consolidation in the existing foundation

31 SUPERFICIAL SUB-FOUNDATION Under the existing foundation it is important the use of the wood wedges to replace after the lowering of the new masonry It is important to take care the temporary supports of the masonry [vertical frames and horizontal frames]

32 SUPERFICIAL SUB-FOUNDATION With reference to the portion of length equal to 1 m, a first sizing can be effected through the two relationships: h t new new = α 2 ( t t) σ 10 [N e mm ] new 3 N γ h new t N h new N = axial force [existing foundation] σ = new stress on the soil t new = inferior thickness of the sub-foundation h new = sub-foundation height γ = weight per unit volume of the sub-foundation t t new N new

33 AMPLIFICATION OF THE FOUNDATION BASE

34 AMPLIFICATION OF THE FOUNDATION BASE The connections distance depends from the masonry quality If necessary, is important to restore the masonry of the existing foundation.

35 TECHNICAL PROVISIONS IN FOUNDATION Amplification of the foundation base

36 AMPLIFICATION OF THE FOUNDATION BASE The employment of concretes with additive expansive is preferable The connection are reinforced to absorb the bending and shear action transmitted by the masonry.

37 DEEP SUB-FOUNDATION REALIZATION OF SMALL DIAMETER PILES

38 DEEP SUB-FOUNDATION REALIZATION OF SMALL DIAMETER PILES Vertical section Horizontal section

39 DEEP SUB-FOUNDATION Realization of small diameter piles Connection at the masonry

40 Provvedimenti tecnici in fondazione: interventi sui terreni

41 Provvedimenti tecnici in fondazione: interventi sui terreni