research project KoSEV

Bringing decayed beams back to life

On-site renovation and rehabilitation of damaged timber floors and rafters with fine-grain resin composite inlays

The restoration of historic timber floors in cultural heritage buildings is complex, especially when dealing with decayed beam-ends caused by fungal or insect defects. Common interventions, such as leaf joints with a wooden or steel leaf in a force-fit manner often encounter challenges related to quality assurance and limited workspace. Traditional methods addressing damaged beam-ends encompass a range of approaches. Carpentry methods, such as leaf joints, lap joints, and bracing, involve the skilled use of woodworking techniques. Prefabricated steel components, including the Weimar basket suspension and Zwickau joist hanger, offer solutions tailored to varying pruning lengths. Other methods employ fiberglass rods and synthetic resin grouting to address structural issues. The mayor drawback of these techniques are limiting  requirements on workspace and quality control on site. The new development are fine-grain composite inlays, connecting pre-damaged timber floor beams with wooden prostheses by minimal intrusion and labor work.


Objectives

  • Restoration with a strong focus on usability, simplicity, sustainability, durability and full composite action under different climate conditions,
  • Time and cost efficiency, even on sites with confined workspaces
  • Restoration of the original joint capacity by replacing damaged parts with minimized interventions,
  • Rehabilitation technique for a broad range of historic ceiling types.

Methods

  • Composite material composition on basis of former R&D projects and experiences and description of material models,
  • Investigations on the adhesive bond-line behavior,
  • Investigations on the influence of hybrid fiber reinforcement, the composite action and the inlay joint capacity under different service conditions,
  • Experimental verification on naturally dried sawn wood and formerly built-in matured wood samples and prosthesis (Picea abies and Abies alba),
  • Experimental investigations of the bondline quality and composite action under bending, shear and tension,
  • Consideration of the annual ring angle and grain direction.


Stats

Research team:

M. Eng. Robin Ihle, M. Eng. Tom Bender, Prof. Dr. Kay-Uwe Schober (1)
Sebastian Obfolter, Christoph Gruß (2)
Andreas Täuber (3)

(1)  Hochschule Mainz, Forschungsgruppe Holz und Kunststoffe
(2)  Dächer von Gruß GmbH
(3)  muro Bauprodukte GmbH


Duration:     March 2019 – November 2021
Budget:        910,000 €
Contact:       M. Eng. Tom Bender

Parts of the research were funded by the German Federal Ministry for Economic Affairs and Energy according to a decision of the German Federal Parliament. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the funding agency.