In order to simulate the specific load-carrying behavior of masonry arch bridges, nonlinear finite element analyses may be carried out. To that end, an associated analysis concept is proposed in this paper. The applied smeared crack model allows one to realistically reproduce characteristic damage patterns observed at existing bridge structures of this type. By using the proposed analysis concept, load-bearing reserves may be revealed and possible causes for existing damage may be identified. The concept includes appropriate failure criteria and corresponding safety margins. The latter approximately conform to valid design codes, but also account for the specifics of nonlinear analyses. In parametric studies, the objectivity of the analysis results and influences of different material parameters on the load-bearing behavior were investigated. Furthermore, two examples of the safety evaluation of existing masonry arch bridges are presented. In both cases, observed damage patterns could be reproduced in the numerical simulations. Destructive load tests at a disused bridge provided an additional opportunity to validate the proposed analysis concept.

Background: Bending tests offer technical advantages when material testing is performed to determine the modulus of elasticity. In biomechanical studies, beam-like cortical bone specimens subjected to flexural loading are usually characterized by nonuniform cross-sectional properties along the beam axis and a comparatively large spatial variation of the local material properties. Objective: A suitable evaluation method for determining the average modulus of elasticity within the volume of beam-like specimens with nonuniform cross section was to be identified. Methods: A total of 138 samples of human pelvic cortical bone were extracted and tested under flexural loading. Different methods, all based on the linear-elastic flexural theory of beams, were applied to determine the average modulus of elasticity on the basis of measured deformations, and the results were compared. Some of these methods utilized the measured midspan deflection, and others used the elastic curve obtained by digital image correlation. Results: The results showed that it was not appropriate to determine the average modulus of elasticity from only the measured midspan deflection. The consideration of deflections at multiple points along the beam axis is recommended. Conclusions: An evaluation method based on the fitting of the analytically determined elastic curve of the beam with its nonuniform cross-sectional properties to the measured deflections is considered the most appropriate method for determining the average modulus of elasticity of the specimen.

Shrinkage of concrete in the plastic stage, i.e., within the first few hours after casting, is mainly caused by the build up of capillary pressure in the pore system of the material due to the loss of water. Early age cracks resulting from this so-called capillary shrinkage may have an unfavorable effect on the durability of concrete pavements. To avoid this type of early age damage, measuring the capillary pressure in situ during the first hours immediately after casting is proposed. On the basis of the measured capillary pressure, it is possible to make decisions concerning the timing of curing measures and to evaluate the effect of such measures. If the capillary pressure is kept below a critical value, shrinkage cracking in the plastic stage may reliably be prevented. The critical capillary pressure depends on the concrete composition and may be determined in laboratory experiments. Wireless capillary pressure sensors have been developed for this particular application. They were successfully tested under site conditions and do not influence the construction process.