Adhesively grouted timber joints under long-term outdoor climate exposure

Investigación experimental de uniones hormigonadas de madera bajo diferentes condiciones climáticas y cambios en el contenido de humedad

Grouted joints are a new way connecting timber members in large-scale or spatial structures to overcome the well-known disadvantages of conventional timber joints. One solution of grouted joints in inlay technology has been developed over the past years and adapted to complex timber truss structures, where mechanical fasteners are glued-in or otherwise connected to the timber members and the gap between the single members (the grouting chamber) is filled with a concrete-type adhesive. For climate exposed structures, the influence of the moisture content on the structural performance is very important. Adhesives for structural purposes shall produce joints of such strength and durability that the integrity of the bond is maintained in the assigned service class throughout the expected life of the structure. Therefore, experimental investigations of this subject have been carried out on grouted timber joints in all service classes after a long-term climate exposure of three years.

Las uniones hormigonadas son una nueva forma de conectar miembros de madera en estructuras a gran escala o espaciales, para evitar los conocidos inconvenientes de las uniones convencionales de madera. En los últimos años se ha desarrollado una solución basada en uniones hormigonadas con tecnología de empaste para celosías complejas de madera, en las que miembros de madera están adheridos a fijaciones mecánicas, y el hueco entre la madera y la fijación (la cámara de hormigonado) se rellena con un adhesivo tipo hormigón. Para estructuras expuestas a la intemperie, el contenido de humedad es muy influyente en el comportamiento estructural. Los adhesivos con fines estructurales deben producir uniones con una resistencia y una durabilidad tal que su integridad se mantenga durante la vida útil de la estructura en la clase de servicio asignada. Para esto, se han realizado investigaciones experimentales en uniones hormigonadas de madera expuesta a largo plazo a todas las clases de servicio durante de tres años.


Objectives

  • Determining the shear-slip relationship between timber and concrete-type adhesive for further numerical investigations,
  • Investigation of the influence of outdoor exposure and changing MC to the compound for service classes 2 and 3,
  • Describing the fracture and crack propagation in CTA and wood due to moisture induced stresses and material degradation.

Methods

  • Investigations on the structural performance and embedding stiffness,
  • Push-out and pull-out tests analyzing large drill holes (the grouting chamber) in comparison to conventional dimensions,
  • Measuring the load-slip behavior between timber and CTA, GIR and CTA in loading direction and the strain between timber and CTA and GIR and CTA perpendicular to the loading direction (radial to the glued-in rod),
  • Measurement of the tangential expansion of the grout and the compound perpendicular to the grain around the drill hole,
  • Analytical and numerical description of material softening in comparison to the  load-carrying capacity in SC 1 according to Eurocode 5 values.


Stats

Research team:

Dr.-Ing. Michael Drass, M. Sc. Leonhard Lieyanto, M. Sc. Tarick Chahade, Prof. Dr. Kay-Uwe Schober (1)
Ass. Prof. Dr. Leandro Romero Morillas (2)

(1)  Hochschule Mainz, Forschungsgruppe Holz und Kunststoffe
(2)  Universidad de Valladolid; Universidad de Granada, España


Duration:     August 2015 – July 2017
Budget:        165,000 €
Contact:       Prof. Dr. Kay-Uwe Schober

Parts of the research were funded by the Rineland-Palatinate Ministry of Science, Further Education and Culture. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the funding agency.