A COMPARATIVE STUDY OF STRENGTH BETWEEN GLUE-LAMINATED CYPRESS TIMBER AND SOLID SAWN CYPRESS TIMBER.

Abstract

Cypress tree (Cupressus Iusitanica) is an exotic tree known for its timber and it is the most common species in Kenya. Glue-laminated timber is a structural engineered wood product comprising a number of layers of dimensioned lumber bonded together with adhesives. Practice of laminating timber in Kenya is not very common. This is true especially for structural timber which is at a minimal. In Kenya, laminated timber is mostly used in manufacture of furniture.

The study was conducted to find out which of the two, glulam and solid-sawn cypress timber, has greater structural strength. This was to be determined through bending and shear testing of both samples of glulam and solid-sawn timber. The study also sought to find out about the state of timber lamination in Nairobi County. This was established by doing a field study and collecting data from various timber workshops around Nairobi.

A field study was conducted by visiting twenty timber workshops visited in Nairobi. The aim of the field study was to find out the most common species of timber available, the type of adhesive used in lamination, method of lamination used, laminated products manufactured and standard codes that are observed. For the lab tests, cypress timber with an average moisture content of 18% was prepared and cut to precision. The tests done were two, bending and shear tests.

Field study results show that the most common species of timber in Nairobi is Cypress while the most common adhesive is Ponal Professional White Glue. The lab test results showed very significant gain in strength due to lamination, there was a 45.92% increase in bending strength and 23.45% increase in shear strength of glulam timber. Test on the glue line showed that the glue could withstand high shear stresses and failure occurred in the wood rather than along the glue line. The workshops use a basic method of lamination and it doesn’t guarantee quality in the final products. The lamination product that is commonly manufactured is furniture and also no standard codes are known and observed by these workshops.

Laminated timber has better strength and performance as compared to solid-sawn timber. Lamination enabled efficient use of timber without wastage and improved the aesthetic value of plain timber. Lamination of timber solves various challenges and uncertainties posed by solid-sawn timber. The limited timber resources can be utilized maximally for better performance with lesser wastage and more quality assurance.

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