Some ideas about the assessment of the stability and fire resistance of existing structures. Need for demolition or renovation ?

2. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN

3. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
< 10%
> 50%
40% of buildings in Walloon region (BE) are older than 1918
Source : Le Soir – 31/07/2014

4. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Why assess an existing structure ?
 Change in use or extension of the design working life
 Check actual (future) reliability
 Repair after slow deterioration
 Severe damages due to an accident

5. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Σ Damages Σ ∆ (new) Requirements+
 Environnemental impact ?
 Net volume reduction ?
 Demolition risks (neighborhood) ?
Results of the study
Intervention(s) ?
Renovation Demolition

6. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Results of the study
 Σ Damages (corrosion, cracks,…)
 Σ ∆Requirements (stability, fire, energy, acoustics, etc.)

7. INTRO FOUNDATIONS FIRE STRUCTURE DESIGNFoundations
Superstructure
Fire

8. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Fire
Foundations
Superstructure

9. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Foundations
Type of foundation
 Shallow
 Deep
I. Demolition => new foundations
II. Re-use
III. Re-use and reinforce
Costs ?
Impact in urban zone ?
Demolition risks (neighborhood) ?

10. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN

11. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Foundations
Points of attention (deep foundations)
 Information on foundation type :
I. Pile type
II. Diameter
III. Length
IV. Loadbearing capacity
 Quality of the foundation
Concrete quality / Pile integrity (vs. depth)
 Assessment of the loadbearing capacity
 Compatibility of piles distribution vs. new building
 If demolition : do not damage old foundations

12. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Foundations
Informations on foundation type :
 As-built plans ?

13. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
You’re so funny…

14. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Foundations
Informations on foundation type :
 As-built plans (rare for old buildings) ?
 Assessment techniques
I. General investigation
II. Ultrasonic tests (in the concrete)
III. Integrity tests (impact echo, mechanical admittance, seismic parallel)
IV. Loading tests

15. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Foundations
Quality of the foundation :
 Cores drillig and tests
 Integrity tests (mechanical admittance method)
Loadbearing capacity :
 Calculations based on CPT (cfr. Report BBRI n°12)
 If pile type unknown : increased safety coeff. / loading tests

16. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Foundations – Reparation…
Masonry
Underpinning
(p≤1,5m)
Timbered Trenches
(depth ≤6m
of more if no water)
Micro-piles Jet-grouting

17. INTRO FOUNDATIONS FIRE STRUCTURE DESIGNFoundations
Superstructure
Fire

18. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Fire (legal rules in Belgium)
Construction > 1994 ?
Change in use ? (ex. : brewery => lofts)
 Adivice SRI and/or conformity with reglementation
Renovation
 New reglementaiton not applicable (but advice SRI needed)
REI30 + REI30 ≠ REI60
OK

19. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Fire safety – passive protection
Splitting in compartments
Evacuation

20. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Fire safety – passive protection
∆ Requirements :
 Compartments :
Walls : OK (Fire resisting panels)
Floors: old= 0 => protection at bottom + tightening
Concrete: + cover. If insufficient rebars : KO.
Timber : panels + insulation at bottom or between joists.
Facades : resisting element needed on 1m developing
length at the floor|facade connection (if KO,
replacement or addition)

21. INTRO FOUNDATIONS FIRE STRUCTURE DESIGNFoundations
Superstructure
Fire

22. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Checklist Structure Inspection
Attention points :
 Plans ?

23. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Checklist Structure Inspection
Attention points :
 Plans ?
 Materials ? / Resistances ?
 Geometry of the structural elements ?
 Connections ?
 Bearings ?
 Static system ?
 Types of damages ?

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 Corrosion
 Alkali-silica reaction (ASR)
 Freeze-thawn
 Sulphates attack
 Cracking
 Overload
 Impact
 Fire
Damaging mechanism (e.g. : concrete)
Cl- < 1 % cement weight

25. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Inspection : how many cores to drill ?
fRk = fRm – k.s
Réf. : EN 1990 Table D1
Standard deviation
average
Characteristic
value which will
be used in
calculations

26. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Reparation : Technico-Economical concept
State
of the
structure
Age

27. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Reparation : some techniques
Concrete :
 Cathodic protection, corrosion inhibitors, etc.
 Cemend-based products
 Use of Fibre Reinforced Polymers (FRP, see also our NIT n°248)
 (External) Post-tensioning (see hereunder)
Palais expositions Charleroi
© Bureau GAMACO

28. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Reparation : some techniques
Concrete :
 Cathodic protection, corrosion inhibitors, etc.
 Cemend-based products
 Use of Fibre Reinforced Polymers (FRP, see also our NIT n°248)
 (External) Post-tensioning (see hereunder)
Steel :
 Replacement of elements
 Special paintings (intumescent, …)
 …
Timber :
 Sticked (carbon/…) plates
 Exoxy resins + rebars
 Double girders, reinforcement… – Engineering beams
Faidherbe Bridge after refurbishment
(Senegal)

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Technical problems
Impact on available volume
Bains Sauvenière Liège
© Bureau CERFONTAINE
Reduction of
available volume

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(re)Calculation : stability - reliability

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Normative framework vs. engineer responsibility
From assessment of existing towards implementing in
(re)construction

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Eurocodes and renovation : how to deal with ?
Basis of design (Eurocode 0) :

33. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Eurocodes and renovation : how to deal with ?
EC0 can be used

34. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Assessment of existing structures
Deterministic => semi-probabilistic approach and reduction of safety factors
 In-situ geometry measurements
 Resistance measurements
γM,red (Eurocode 2)
Concrete 1,30 (-13%)
Rebars 1,05 (-9%)

35. INTRO FOUNDATIONS FIRE STRUCTURE DESIGN
Will demolition actually be
possible/economical ?
Building having demolition in mind ?

36. INTRO FOUNDATIONS FIRE STRUCTURE CALCULS
Lab. Structures
bp@bbri.be