Many possibilities exist in bridge construction for the application of structural or semi-structural adhesive connections, such as the connection of bridge decks to the main girders, the application of strengthening elements, the fixation of crash barriers, parapets or expansion joints. The connection of different materials is simplified and complicated anchoring of new elements in existing concrete can be prevented.
Structural adhesive connections in bridge construction are used for more than 50 years. Examples are butt joints of segmental bridges, connections between concrete bridge decks and steel girders, prestressed connections for steel truss bridges as well as for the application of strengthening elements (steel or carbon strips) to existing bridges.
Despite the positive experiences with structural adhesive joints made to this day, a considerable need of research exists with regard to the characterisation and durability of adhesive materials. Concerning material characterisation, still no rules exist regarding the determination of minimum values of the nonlinear mechanical properties or material safety factors in bridge construction. Concerning the durability of adhesives, systematic investigations are still missing with regard to bridge specific environmental exposures.
The objectives of the research project are:
1) Investigation of structural adhesives regarding the application in bridge construction, consideration of brittle epoxy and ductile polyurethane and acrylic adhesives
2) Characterisation of the mechanical properties of adhesives:
- viscoelastic and plastic material behavior,
- effects of loading rate and temperature,
- comparison of test protocols (ISO, ASTM, EN, etc.),
- determination of characteristic values and material safety factors.
3) Investigation of the durability of adhesives:
- effects of humidity, temperature, UV on material properties
- fatigue behavior
- determination of reduction factors for characteristic values
4) Design model for adhesives in Eurocode format and recommendations for application.
The following methods are used:
- Literature review,
- Laboratory testing, modeling of constitutive equations,
- Theoretical studies.
Within this project, the short and long term material behavior of several adhesive types is investigated using experimental and analytical methods.
The following results were expected:
1) Knowledge about the short and long term behavior of brittle and ductile structural adhesives in bridge construction,
2) basic information for the design of adhesive connections: determination of the characteristic values, specification of material safety factors and reduction factors according to classes of exposure,
3) recommendations regarding possible applications of adhesive connections, choice of adhesive types, constructive detailing, required protection measures and application.