BRI Research Paper


Strength Properties and Testing Method of Finger Joints.

K.Imaizumi and J.Moe; July, 1965. 19p.


Several types of finger joints for glued laminated beams were tested to investigate the static strength properties and the possibility of developing a method of quality control of finger joints based on the testing of small specimens.

Twenty-eight beams with jointed limanation and ten control beams were produced in all. Each beam was 13 X 20 X 450 cm and joints were placed in the tension side of the beams.

One of the tested types of finger joint behaved satisfactorily yielding a strength ratio of approximately 0. 8, while the other type only 0. 49 when the load corresponding to failure in the joint of the outer lamination in the tension side is considered to be critical.

The distance between joints in neighbouring lamination of 24 times the lamination thickness was not sufficient to prevent the cracks from traveling along the beams from joint to joint.

A special type of small bending test specimen which was developed proved quite promising for the purpose of determining the strength ratios of finger joints.

* Manuscript received on June 3, 1965.
** Research Member of B.R.I , Ministry of Construction
*** Research Staff of Norwegian Building Research Institute

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