The fastening of french balconies of an apartment building in Berlin was planned with concrete screws, which did not have a European Technical Assessment for use in solid lime sandstone. Therefore, tests were required to obtain a Project-related approval (ZiE) from the Deutsches Institut für Bautechnik.

The used test setups were designed to correspond to the conditions on site. The load-bearing capacity of the anchorage as well as the connection between the anchorage ground and the brackets was investigated experimentally. The brackets and the concrete screws were loaded at 0°, 30° and 90°. Furthermore, load cycling tests were performed to evaluate the repeated loading of the mentioned elements.

In industrial floorings, anchors are often used to fix machines and racks. As a rule, metal anchors are used for anchoring, as they are easy to install and have a sufficiently high load-bearing capacity.

If the building is vacated or repurposed, part of the anchoring usually remains in the area of the floor, since they cannot be dismantled. This creates potential corrosion points, even if the floor is rehabilitated. Therefore, it is important to have a concept for demountable anchoring already before installation or to design the removal in such a way that the risk of corrosion is minimized and floor rehabilitation is possible.

Anchoring in special concretes is always a challenge, especially in lightweight concretes, since only limited experience is available here with regard to anchor load-bearing capacity.

Therefore, the assessment is based on tests on specimens or directly on site. In this project, the evaluation was carried out for infra-lightweight concrete (ILC 620), which has a strength of only 4.5 N/mm².

This project showed that, with sufficient good cleaning and proper installation, the requirements for anchorages for anti-fall components (e.g. window anchorages) are also met for this low concrete strength.

The tests and the measured breaking cones (see figure) were also used to derive the necessary arrangement, edge distance and spacing, as well as the design of the window anchorages.

If bonded anchors are used at -70° C, several questions must first be answered. On the one hand, embrittlement of the steel may occur, on the other hand, the bond of the mortar could be damaged by alternating freeze-thaw conditions. It is also possible that the mortar could become brittle, resulting in a considerable reduction in load-bearing capacity under alternating shear and tension loads.

In the present project, the issues were resolved for a specific mortar by carrying out tests at the MPA University of Stuttgart, which were evaluated by us. It was shown for the tested mortar that the above-mentioned effects are negligible and that no material embrittlement occurs.

Galvanised concrete screws were to be used for the fastening of aluminium square pipes for a roof covering in a building project. Due to the direct contact of the galvanised concrete screws with the aluminium square pipes, the site test engineer had concerns that the service life of 50 years specified in the European Technical Assessment (ETA) of the concrete screw could no longer be maintained or would be adversely affected by contact corrosion. Therefore, we were commissioned for our expertise in the field of corrosion and to prepare an expert report.

In our evaluation, the process of contact corrosion was described and the various Hazards that can cause contact corrosion were explained. For the intended application, the dangers of contact corrosion were compared and evaluated with the existing installation conditions. Finally, various methods were proposed to avoid contact corrosion or to reduce the risk of contact corrosion. Based on our expert opinion, the concerns of the structural engineer were eliminated.