Frederik Teworte

Structural Assessment of Concrete Bridges in Germany : Shear Resistance under Static and Fatigue Loading

Abstract The demands on the load-carrying capacity of bridges have increased over the last few decades because of the higher traffic volumes and weights. In the future, an even greater increase is expected. Since a large part of the existing bridges in Germany was built in the 1960s and 1970s, the assessment of these structures is deemed crucial. Therefore, the German Ministry of Transport introduced guidelines in 2011 allowing for a more accurate determination of the bearing capacity compared to the current German bridge design code. Nevertheless, many concrete bridges show deficits in shear and fatigue resistance. Consequently, a supplement to the guideline was published in 2015 to incorporate new research results. This paper describes the approaches for static and fatigue shear verification that consider the provided shear reinforcement. These methods refer to a truss model with variable compression strut inclination. Further, an application to a typical box-girder bridge in the road network is presented, demonstrating the potential for increasing the design value of the bearing capacity.

Shear Strengthening with Textile Reinforced Concrete

Summary A large part of existing bridges in Germany exhibits deficits in the shear capacity under static and cyclic loading according to the current design rules. More structures are expected to demand refurbishment and strengthening within the next years especially due to the current conditions of many older road bridges. Since a reconstruction of the respective bridges is not feasible in many cases, the assessment and development of effective strengthening methods becomes more important. The use of textile reinforced concrete (TRC) offers an innovative alternative to existing strengthening measures by combining the advantages of lightweight glued CFRP-stripes (Carbon Fiber Reinforced Polymer) and additional concrete layers. For the above reasons, full scale tests on strengthened and non-strengthened I-shaped prestressed concrete beams (h = 0,7 m, l = 6,5 m) under cyclic shear loading as well as single span reinforced concrete slab strips (b = 0,5 m, h = 0,28 m) under static shear loading were carried out at the Institute of Structural Concrete at RWTH Aachen University. The paper presents the test results with regard to the effectiveness, advantages and possible fields of application of this innovative strengthening method. Keywords: shear; strengthening; bridges; testing; slabs; reinforced concrete; prestressed concrete; textile reinforced concrete; cyclic loading.