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Glued-in rods for timber structures


Glued-in rods are now being used in several European countries, but the performance requirements and the design rules differ, which is a serious obstacle to trade. A standard on the design of timber (Eurocode 5 - Design of timber structures - Part 2: Bridges) has been drafted by CEN.TC250/SC5. The intention is now to include glued-in rods. Due to the uncertainty about the behaviour of such connections and the lack of reliable calculation methods, glued-in rods have not yet been introduced into the main part of the draft standard and have instead been placed in an informative annex. CEN.TC250/SC5 has decided to include glued-in rods also in Eurocode 5 - Part 1: General rules and rules for buildings. In 1992, it was agreed to include glued-in rods in the work programme of CEN.TC124 and a working group (WG6) was set up. The group confirmed the need for the standards in the field and a work programme including product, production and test standards was drafted. The group came to the conclusion that existing knowledge was insufficient to draft standards that would be acceptable to all European countries. To develop suitable test methods, the mechanical behaviour of glued-in rod connections had to be known to a greater extent. It was also identified that factors such as durability, creep and creep-rupture behaviour of the adhesive bond had to be studied in more detail. In addition to the structural wood adhesives, which are rather brittle, ductile adhesives such as two component polyurethane have been used in glued-in rods. For the latter adhesive types, no standardised test procedures and requirements with respect to applications in timber structures and in metal to wood bonds exists. Therefore, in 1992, CEN.TC193/SC1 (Adhesives for wood) was asked by CEN.TC124 to include adhesive for glued-in rods on the list of work items. In the spring of 1996, CEN.TC193/SC1 formed a working group (WG6) for this task. The group has, however, concluded that the existing knowledge was insufficient to draft standards.

Perform theoretical and experimental work leading to a calculation model for axially loaded glued-in rods based on the adhesive bond properties as well as the wood and rod material properties. This must take into account the effect of varying climatic and loading conditions as well as fatigue. This step will give information required by CEN.TC250/SC5 in the preparation of Eurocode 5 - Design of Timber Structures.
Develop test methods for the evaluation of adhesives for glued-in rods with respect to strength, durability, creep and creep rupture behaviour under different climatic conditions. This will support the work of CEN.TC193/SC1 (Wood adhesives).
Derive test methods for the production control of structural glued-in rod connections. This will support the work of CEN.TC124/WG6 (Glue-in rods in timber structures).
The project commenced on 1 February 1998 and the kick-off meeting was held in Stuttgart from 5 to 6 February 1998.
SP-NL-1 17/02/98
WP 1 Development of a calculation model;
WP 2 Test methods for adhesives;
WP 3 Effect on the axial strength of distance between rods, and between rods and
timber edge;
WP 4 Effect of moisture conditions on the axial strength;
WP 5 Duration of load test on full sized glued-in rod specimens;
WP 6 Effect of fatigue;
WP 7 Test methods for production control;
WP 8 Drafting design rules for Eurocode 5;
WP 9 Management.

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Swedish National Testing and ResearchInstitute SP
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SP - BTt
501 15 Boräs

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Participants (10)