High performance concrete hinges made from low-modulus polymer concrete for large hinge rotations in sustainable, low-maintenance timber bridges

• Applicant: Professor Dr.-Ing. Volker Schmid
• Subject Area: Structural Engineering, Building Informatics and Construction Operation
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 553813430

Monolithic joints made of polymer concrete are being researched in detail for the first time in this research project. In addition, the first technical fundamentals on the positive influence of carbon fiber reinforcement on polymer concrete joints are to be researched. Concrete joints have numerous advantages, such as their high load-bearing capacity and deformation capacity, their durability and their low maintenance requirements - properties that can be significantly improved through the use of polymer concrete. Polymer concrete joints are easy and inexpensive to produce, but there are no scientifically proven rules for their design. In the course of the research project, concrete joints made of polymer concrete are to be investigated for the first time and a scientifically validated design concept is to be developed. For the very first time concrete joints will be manufactured from high-strength polymer concrete. This will significantly expand the field of application for monolithic joints. Polymer concretes achieve compressive strengths in the order of magnitude of high-strength and even ultra-high-strength concretes, with a tensile strength five times that of cement concrete. As a result the axial load-bearing capacity of a concrete joint can be significantly increased by using polymer concrete. At the same time, the low modulus of elasticity of polymer concrete and its high ductility in compression allow even greater joint rotations. In addition, the chemical resistance and impermeability significantly increase the durability of polymer concrete joints. This is important as concrete joints are particularly exposed to the weather due to their location. Thanks to its excellent adhesive properties, polymer concrete can be easily connected to a wide variety of materials. This makes polymer concrete joints particularly suitable for timber engineering and timber bridge construction, where suitable, robust and durable connections and efficient and economical support details are still lacking. The polymer concrete hinges are cold cast directly onto the ends of the timber beams using reinforced finger joints. The polymer concrete connection especially protects the end grain from penetrating moistur The research project is also investigating for the first time whether and how the polymer concrete joints can be reinforced with reinforcement made of carbon fiber. Conventional reinforcing steel reinforcement would rust in non-alkaline polymer concrete. Reinforcement made of carbon fiber reinforced plastic (CFRP) is characterized not only by its corrosion resistance, but above all by its low self-weight and high tensile strength. For the production of the reinforcement cages, the carbon fiber rovings are soaked in epoxy resin and subsequently wrapped around a support structure. This gives the reinforcement its desired stiffness and shape after the resin has hardened.

• DFG Programme: Research Grants