Gradient Density – A novel method for column-to-slab joints in point-supported cross-laminated timber slabs
The research project investigates a novel design-fabrication system utilizing localized timber densification. The proposed method leverages the enhanced mechanical properties achieved through timber densification and applies it in a targeted and differentiated manner, tailored to meet structural demands. This is synergized with the strategy of pressing and gluing hardwood plugs into the cross-section, which can preserve the original cross-sectional height and further strengthen the area. This method is highlighted for the smooth shaping of fiber direction – maintaining the full capacity of the original material while simultaneously reinforcing a small area.
The key design application is identified at the column-to-slab joints in point-supported CLT slabs. Instead of conventional solutions involving holes and a stiff bypassing material, the slab is reinforced only around the most structurally critical area to allow existing timber to perform in all three directions without compromising structural capacity by puncturing. The design is evaluated to be effective in a context where the slab’s self-weight is not the defining factor for the slab thickness, but the performance of the joint is. The resulting high-performance joint enables ultra-thin, high-performance point-supported CLT slab systems with a simple fabrication intervention.
The study comprehensively explores the process of localized densification, encompassing design, fabrication, and evaluation strategies. These concepts are substantiated through mechanical testing, fabrication testing, and physical prototyping.
ITECH M.Sc. Thesis Project 2024: Gradient Density – A novel method for column-to-slab joints in point-supported cross-laminated timber slabs
Donghwi Kang, Otto Lindstam
Thesis Advisers: Gregor Neubauer, Hans Jakob Wagner
Thesis Supervisor: Prof. Jan Knippers
Second Supervisor: Prof. Achim Menges
This project was developed in part at the TallWood Design Institute in Oregon with external mentoring from Prof. Dylan Wood.
The research exchange was supported through an Outgoing Grant by Cluster of Excellence Integrative Computational Design and Construction for Architecture (IntCDC) and the digitize wood platform.
The project received further assistance from Michael Schneider and Philip Duncan at the Wood Workshop of Faculty 1, University of Stuttgart.
Support for Outstanding Master's Theses
digitize wood supports the creation of prototypes as part of ITECH master's theses. We are delighted to be able to support the next generation of timber construction professionals and congratulate Donghwi Kang and Otto Lindstam on successfully completing their studies!
German Timber Construction Award – Deutscher Holzbaupreis 2025
The project wins the „Deutscher Holzbaupreis“ 2025: Verena Hubertz (Federal Minister for Housing, Urban Development and Building) presented the prize to the two ITECH Alumni, Chris Donghwi Kang and Otto Lindstam on May 27, 2025 during the world's leading trade fair for the international woodworking and wood processing industry, LIGNA, in Hanover. The method for metal-free point-supported flat slabs made of wood, was honored with a special award in the main category.
