Knowledge acquisition of existing buildings by means of diagnostic surveying. Case studies.

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Giovanna Concu, Nicoletta Trulli, Monica Valdès Department

1 Knowledge acquisition of existing buildings by means of diagnostic surveying. Case studies. Giovanna Concu, Nicoletta Trulli, Monica Valdès Department of Civil and Environmental Engineering and Architecture University of Cagliari - Italy

2 KNOWLEDGE ACQUISITION PROCESS Øresearch and collection of existing data and information STEPS Øgeometric an structural survey Øassessment of materials properties LEVEL OF KNOWLEDGE CONFIDENCE FACTOR Øgeometry PARAMETERS FOR THE STRUCTURAL MODEL Østructural details Øproperties of the material 2

3 KNOWLEDGE ACQUISITION PROCESS Geometry Structural details Properties of the material Tests Inspections Diagnostic campaign PLANNING 3

4 PLANNING THE DIAGNOSTIC CAMPAIGN GOAL to achieve the highest possible level of knowledge REQUIREMENTS o o statistical representativeness (single element entire structure) reliability CONSTRAINS o o o o accuracy required accessibility admissible damage invasiveness costs (time money) 4

5 CASE STUDIES CONCRETE STRUCTURES Hotel Council Housing Building Examples of some points concerning tests planning and implementation 5

6 CASE STUDY: HOTEL Ground floor Basement Typical floor 6

7 CASE STUDY: HOTEL LEVEL OF KNOWLEDGE = LC2 The number of concrete specimens depends on the floor area Recurring geometric and structural layouts + Homogeneous areas + Non Destructive Testing (NDT) Decrease of the number of specimens Ultrasonic Testing (UT) Rebound Hammer Test (R) Pull-out Test (PO) Floor Concrete samples expected Cores extracted UT (V) R (Ir) PO (F) Basement Ground Second Third Fourth Total

8 CASE STUDY: HOTEL RESULTS parameter mean standard deviation coeff. of variation fc (N/mm 2 ) V (m/s) Ir F (kn)

9 CASE STUDY: HOTEL NDT CALIBRATION NDT parameters have been correlated to cores compressive strength NDT parameter Correlation Formula suggested by Italian Standards V f est = a + e bv 0.60 Ir f est = a + Ir b 0.57 F f est = a + bf 0.44 V, Ir f est = a + bir + cv 0.60 V, F f est = a + bv + cf 0.67 Ir, F f est = a + bir + cf 0.59 V, Ir, F f est = a + bv + cir + df 0.68 r 2 9

10 CASE STUDY: HOTEL Compressive strength estimated by correlation formulas Element f c f est,v f est,ir f est,po f est,comb Basement Pillar 1 Pillar 2 Pillar 3 Pillar 4 Pillar 5 Pillar 6 Pillar 7 Pillar 8 Pillar 9 Pillar 10 Pillar 11 Pillar 12 Pillar 13 (N/mm 2 ) (N/mm 2 ) (N/mm 2 ) (N/mm 2 ) (N/mm 2 )

11 CASE STUDY: COUNCIL HOUSING BUILDING typical floor 11

12 CASE STUDY: COUNCIL HOUSING BUILDING LEVEL OF KNOWLEDGE = LC2 The number of concrete specimens depends on the floor area Visual inspection High level of damage High number of samples + NDT Ultrasonic Testing (UT) Rebound Hammer Test (R) Pull-out Test (PO) Floor Concrete samples expected Cores extracted Ground First Second Third Total UT (V) R (Ir) PO (F) 12

13 CASE STUDY: HOTEL BUILDING RESULTS parameter mean standard deviation coeff. of variation fc (N/mm 2 ) V (m/s) Ir F (kn)

14 CASE STUDY: COUNCIL HOUSING BUILDING NDT CALIBRATION NDT parameters have been correlated to cores compressive strength NDT parameter Correlation Formula suggested by Italian Standards V f est = a + e bv 0.66 Ir f est = a + Ir b 0.12 F f est = a + bf 0.43 V, Ir f est = a + bir + cv 0.77 V, F f est = a + bv + cf 0.76 Ir, F f est = a + bir + cf 0.41 V, Ir, F f est = a + bv + cir + df 0.72 r 2 14

15 CASE STUDY: COUNCIL HOUSING BUILDING Compressive strengthestimated by correlation formulas Element f c f est,v f est,ir f est,po f est,comb (N/mm 2 ) (N/mm 2 ) (N/mm 2 ) (N/mm 2 ) (N/mm 2 ) Pillar Pillar Pillar Ground floor Pillar Pillar Pillar Pillar Pillar Pillar

16 CONCLUDING REMARKS The planning of the diagnostic surveying should follow the acquisition of some preliminary data Ø General and specific information already available Ø Geometric survey Ø Visual inspection Ø Identification of homogeneous areas The selection ofthediagnostic testingmethod shouldfollowtheanalysis ofsome aspects Ø Information available Ø Required accuracy Ø Admissible level of invasiveness Ø Costs NDT methods are powerful tools Ø QUALITATIVE purpose (comparison, preliminary tests for identifying homogeneousareas) Ø QUANTITATIVE purpose (mechanical properties of the material) CALIBRATION is mandatory NDT calibration is an essential step necessary for extending testing results to broader samples and estimating mechanical and physical properties 16

17 CONCLUDING REMARKS The diagnostic campaign is an essential part of the knowledge acquisition process concerning existing buildings Ø it has to be accurately planned Ø it has to be considered, in effect, a design process Ø it claims experiencedspecialistsandsometimesmultidisciplinary staff (historical buildings, protectedbuildings,..) Ø it needs a budget proportional to the type and the amount of work 17

18 THANK YOU FOR YOUR KIND ATTENTION FURHER INFO: 18

Chapter 1 INTRODUCTION

17 Chapter 1 INTRODUCTION 1.1 Background of the problem Concrete structures as many other engineering structures are subjected to deterioration that affect their integrity, stability and safety. Faced