The technology is called the ALP GSA method (alternative load path method) and was developed together with Professor Ernst Gehri and neue Holzbau AG Lungern. In this process, the stresses and resulting cutting forces on the breakthrough are absorbed directly by the GSA reinforcement. The process can be copied from nature. A tree, for example, produces "reinforced" zones around the branch area (denser wood).

Breakthroughs can significantly reduce the load-bearing resistance of glulam beams. The failure is brittle and occurs suddenly, without prior major deformations or visible notice. In practice, however, breakthroughs in solid timber beams can hardly be avoided. Building services are playing an increasingly important role in modern timber construction, especially in multi-storey residential and office buildings. In order not to lose room height unnecessarily, it is desirable to achieve the lowest possible construction heights despite larger spans and loads. This results in proportionally larger openings for the beam. The opening sizes are (according to the standard) also quite restricted (internal opening heights no more than 30 percent; for external reinforcements no more than 40 percent of the beam height). Also, the verification according to the standard must always be carried out on the net cross-section (residual cross-section).

Glued-in threaded rods
Together with Professor Ernst Gehri, neue Holzbau AG has been researching and developing glued-in threaded rods for 15 years. Under the brand name "GSA technology", a wide variety of connecting parts have been developed that are successfully used in various timber structures. Connections with glued-in threaded rods are among the most efficient means of connection in modern timber construction.

Large forces can be transferred over a small area. Over the years, neue Holzbau AG has succeeded in developing various fasteners for a wide range of applications. These are parts that are inexpensive to produce in series and are easily connected on the construction site with just a few bolts. GSA technology is also suitable for complex components. From truss construction and tension-reinforced components (timber reinforcement) to timber-concrete composites and transverse tension, transverse compression and shear reinforcements, high-performance solutions can be found everywhere.

As the tests in Lungern have shown, GSA technology is also suitable for reinforcing openings. In contrast to previous practice, where the reinforcements are only used for transverse tensile reinforcement, the GSA anchors are arranged in a truss-like manner in the ALP method.

The GSA bars are designed for the forces to be redirected ΔM breakthrough and ΔS shear flow. To determine the resultant loads from the shear force, it is necessary to switch from the traditional shear design (section perpendicular to the beam axis) to an analysis of the shear model parallel to the fiber. The arrangement is carried out in such a way that the forces to be transmitted are transferred around the breakthrough as optimally as possible.

In order to perfect the new technology, we decided to create an extensive series of tests. Test specimens up to a height of 1000 mm with round and rectangular openings up to 50% of the beam height were produced and tested. Many beams broke in the unperforated field in shear. If the fracture occurred in the breakthrough area, this happened at sufficiently high values (at shear values that are usually to be expected in relation to the full cross-section!).

The aim of the investigations is to provide the executing engineers with geometric arrangements for breakthroughs in the near future. If these simple rules are adhered to, the design can be carried out without reducing the cross-section despite openings. The engineering of the new Holzbau AG takes over the dimensioning and the arrangement of the anchors.