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A reliable Inspection procedure of existing Timber structures: the case of Guarini's Towers roofs - Racconigi Castle (Italy)

Marco LAURIOLA, Massimo MANNUCCI, Mario OSCHI
LegnoDOC snc - Via M. De Bernardi, 64 - 50145 Firenze (Italy).
Nicola MACCHIONI
Istituto per la Ricerca sul Legno/CNR - Via A. Barazzuoli, 23 - 50136 Firenze (Italy)
Contact

ABSTRACT

1 - INTRODUCTION

2 - DESCRIPTION OF THE METHOD

3 - EXAMPLE

4 - CONCLUSIONS

Acknowledgements


GRADE

1st 2nd 3rd
DEFECT/FEATURE:

Frost cracks
Insect holes
Ring shakes
Rot (fungal decay)
Wounds

Not admitted in the resistant cross-section (i.e.: some insect holes in the sapwood are accepted if sapwood is not considered part of the resistant cross-section)

Single knots (ratio of knot diameter to face width) Max. 1/5, but Max. 50 mm Max. 1/3, but Max. 70 mm Max. 1/2
Knot cluster (ratio of knot cluster's diameter to face width) Max. 2/5 Max. 2/3 Max. 3/4
Slope of grain in radial section Max. 7% Max. 12% Max. 20%
in tangential section Max. 10% Max. 20% Max. 33%
Ring width Softwoods Max. 2 mm Max. 3,3 mm any (no requirement)
Oak Min. 7 mm Min. 4 mm
Chestnut Min. 8 mm Min. 3,3 mm
Table 1: Visual grading of timber in old structures. Grading rules applicable for field inspections, only to the resisting cross-section.

WOOD SPECIES GRADE Compr. strength Bending strength Tensile strength Shear strength MOE
FIR 1st 11 11.5 11 0.9 13000
2nd 9 10 9 0.5 12000
3rd 7 7.5 6 0.7 11000
SPRUCE 1st 10 11 11 1.0 12500
2nd 8 9 9 0.9 11500
3rd 6 7 6 0.8 10500
LARCH 1st 12 13 12 1.1 15500
2nd 10 11 9.5 1.0 14500
3rd 7.5 8.5 7 0.9 13500
PINES 1st 11 12 11 1.0 13000
2nd 9 10 9 0.9 12000
3rd 7 8 6 0.8 11000
CHESTNUT ELM ASH 1st 11 12 11 0.8 10000
2nd 9 10 9 0.7 9000
3rd 7 8 6 0.6 8000
POPLAR
(not hybrid)
1st 10 10.5 9 0.6 9000
2nd 8 8.5 7 0.5 8000
3rd 6 6.5 4.5 0.4 7000
OAKS 1st 12 13 12 1.2 13500
2nd 10 11 10 1.0 12500
3rd 7.5 8.5 7 0.9 11500
BLACK LOCUST 1st 12 13.5 13 1.2 14000
2nd 10 11.5 11 1.0 13000
3rd 7.5 9 7 0.9 12000
Table 2: Admissible strength values and mean values of the MOE (N/mm²), parallel to the grain (MC = 12%). Grades according to Table 1.

Bibliographic References

  1. Macchioni N., Mannucci M. - Inspection techniques for ancient wooden structures: state of the art and research needs. 6th International Conference on "Non Destructive Testing and Mycroanalysis for the Diagnostics and Conservation of Cultural and Environmental Heritage" (ART'99), Rome 17-19 May 1999, 2155-2165.
  2. Macchioni N., Mannucci M., Zanuttini R. - Non-destructive evaluation of ancient wooden structures. 2nd International Congress on "Science and technology for the safeguard of cultural heritage in the mediterranean basin", Paris 5-9 July 1999, 161.

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