رسائل ماجيستير
English
2017
Derivation of Design Stresses for Boswellia papyrifera Gafal Wood grown in Blue Nile State Sudan
Tageldin Hussein Nasroun, يوسف عيسى أحمد محمد
كلية الدراسات العليا-جامعة السودان للعلوم والتكنولوجيا · السودان
This study aimed at explaining the procedure for deriving design stresses for timberand providing engineers with some of the information which will help them indesigning timber structure. Timber is a very variable material affected by manyfactors, this makes it important to determine mechanical properties by standardmethods using small clear specimens. As clear wood is not available for use, it isimportant to apply all the necessary reduction factors to reach design stresses. Bothstatic bending and compression parallel to the grain tests were carried out accordingto standard procedures. Static bending test was carried out according toSudanese standard no. 5175/20/2012 adopted form ISO 3133/1975 whilecompression parallel to the grain was carried out according to ISOstandard procedure no. 3787/1979. The basic stresses for the two propertieswere derived first by using two reduction factors to the mean ultimate stresses fromtest results to cater for wood variability, safety and duration of load. The Factorsinfluencing strength were studied for grading the timber and assigning strength ratioto each grade. Grade (or design) stresses were then calculated by multiplying basicstress by the strength ratio for each grade. These Results revealed that the basic stressfor bending for gafal wood was 10.8 MPa and 13.6 MPa for compression parallel tothe grain. Grade (design) stresses in MPa were as follows: Grade 1 Grade 2 Grade 3 Grade 4 For Bending 8.64 7.02 5.40 4.32For compression 10.53 8.55 6.58 5.26These results indicate that gafal wood with its low density and low strength values canonly be used for light constructions as columns and non-load bearing members inwood frame buildings. It can also be used as raw material for many wood industries.