Thomas Lambert  Prof. Dr.-Ing. Michél Bender  Prof. Dr. techn. Wieland Becker 《Beton- und Stahlbetonbau》2021,116(7):528-538

Experimental investigations on the material behaviour of polymer concrete – Application and potential of polymer concrete in construction Polymer concrete is a high-performance material that already has a wide range of applications in structural and mechanical engineering. However, in structural engineering the potential of the material cannot be fully exploited due to a lack of standardization of the material and the design, as well as an insufficient classification of the material behaviour according to the relevant civil engineering standards. On the other hand, the potential of polymer concrete with its high compressive and tensile strength is particularly in the application area of load-bearing components, such as highly stressed node and connection geometries of truss and engineering structures. In order to expand the application possibilities in the construction industry, the relevant material parameters of a commercially available polymer concrete, such as compressive strength, bending strength, tensile strength, modulus of elasticity and bond strength to reinforcing steel, are tested according to civil engineering standards. Characteristic values of material properties are derived. The tests vary in specimen geometries, concrete age and temperature. To classify the results, a comparison was made with normal-strength, high-strength and ultra-high-performance concrete.  相似文献   

    

Prof. Dr.-Ing. Balthasar Novák  Franziska Stein  Jochen Reinhard Dipl.-Ing.  Andrian Dudonu Ing. 《Beton- und Stahlbetonbau》2021,116(10):718-726

Surface application of distributed fiber optic sensors for bridge monitoring Concerning the ageing infrastructure and the lack of capacities for repairs and new constructions, it is necessary at present and in the future to develop methods to extend the service life of infrastructure structures with design and structural deficits. One approach is to use monitoring systems for condition monitoring of the structure and early damage detection. Further developments in distributed fiber optics show the possibility of monitoring bridge structures up to the entire span. For this purpose, surface applications for the use of distributed fiber optics as permanent monitoring for crack detection and monitoring on existing bridges in solid construction were investigated at the University of Stuttgart in cooperation with the engineering office Schömig-Plan, Kleinostheim/Stuttgart. The application was installed and examined in field tests under practical boundary conditions.  相似文献   

    

Andreas Stollwitzer Dipl.-Ing.  Univ.-Prof. Dipl.-Ing. Dr. techn. Josef Fink 《Bautechnik》2021,98(7):465-474

Damping parameters of ballasted track on railway bridges – part I: vertical relative displacements in the ballast The effects of the ballasted track on the dynamic properties of railway bridges have been the focus of pertinent scientific discourse up to the present. The discrepancies between dynamic calculations and measurements have thus constituted core challenges in railway bridge engineering to this very day. A wide range of mechanical models allows for dynamic calculation of bridge vibrations. However, pertinent parameters vary considerably and thus call for targeted research of ballasted track. Such focused and isolated analysis of the dynamic behaviour on railway bridges is conducted at a special large-scale test facility at TU Wien. This paper focuses on the energy dissipation as a result of vertical displacements in the ballasted track with special consideration of damping parameters gained from combined theoretical and empirical calculations. The core parameters thus obtained show a significant dependency on the acceleration level. They are subsequently integrated into a comprehensive, detailed model.  相似文献   

    

Andreas Stollwitzer Dipl.-Ing.  Univ.-Prof. Dipl.-Ing. Dr. techn. Josef Fink 《Bautechnik》2021,98(8):552-562

Damping parameters of ballasted track on railway bridges – part II: energy dissipation in the ballasted track and related calculation model Calculations of the dynamics of railway bridges rely on a broad range of pertinent models which analyse the dynamic properties of the ballasted track. However, the substantial variations of related stiffness and damping parameters complicate appropriate implementation into vibration prognoses. Relying on dynamic calculations gained from a special test facility, which allows to analyse the ballasted track (isolated from the bridge structure), it is possible to determine related damping parameters. Those core parameters correspond to a mechanical model which is tuned to the energy dissipation and damping mechanisms arising in the ballasted track. Within the scope of this test the damping parameters show significant dependencies as regards frequency, acceleration and displacement, but at the same time cause minimal variances within these dependencies. This facilitates the set-up of a sufficiently precise and realistic calculation model for the ballasted track, plus related core parameters.  相似文献   

    

David Schaarschmidt Dipl.-Ing.  Prof. Dr.-Ing. Holger Flederer 《Beton- und Stahlbetonbau》2021,116(5):378-386

Prestressed dry joints for modular bridge structures under cyclic loading Modular construction with precast concrete elements has been becoming increasingly important for years. Current developments in construction industry and research investigate the joining of the modules without any in-situ concrete, mortar, gluing or shear keys. One possibility is to activate surface friction by pre-tensioning. While shear strength depends largely on the roughness coefficient, bending strength is related to decompression of dry joints. In order to prove structural strength a realistic assessment of the surface topography is essential. DIN EN 1992-1-1 distinguishes four levels ranging from very smooth joints to keyed joints, which means that the large number of different surface qualities is not represented adequately. Furthermore the transferability of Coulomb's law of friction to concrete surfaces at higher compression stresses in joints should be investigated. Bridge structures and wind turbines are two primary fields of application. Both types of structures are predominantly claimed by non-static loads. This stress causes fatigue in the interface region of the precast components. Due to errection of fatigue-resistant and safe structures the relevant load characteristics and their effects on contact surface and concrete matrix must be identified.  相似文献   

    

Prof. Dr.-Ing. Christoph Dauberschmidt  Prof. Dr.-Ing. Wolfgang Breit  Felix Becker  Ayhan Celebi Dipl.-Ing. 《Beton- und Stahlbetonbau》2021,116(4):248-261

Repair of chloride-contaminated RC-components by application of a coating – Investigations on the application limits of methods 7.7 and 8.3 The technical rule of the German Institute for Building Technology (Deutsches Institut für Bautechnik – DIBt) “Maintenance of concrete structures” (TR-IH) introduced in January 2021 enables two methods for the repair of chloride-contaminated structures by applying a surface protection system with chlorides remaining in the concrete (to a large extend). The repair method 7.7 “Coating of chloride-containing concrete” may be applied if the reinforced steel is still passive and the chloride load in the concrete cover ensures a distance of the critical chloride content from the reinforced steel of 10 mm. By developing a closed solution of the diffusion-controlled chloride redistribution after applying the coating even with partially water-saturated concretes and a parameter study, it could be shown that the maximum remaining chloride content in the concrete cover may be 2.0 wt.-%/cem. The repair method 8.3 “Increase of electrical resistance by coating”, on the other hand, may also be applied with active reinforcement corrosion. Extensive investigations have widely confirmed the application limits mentioned in the TR-IH and further sharpened them with regard to concrete quality and the type of surface protection system. Finally, the method is only applicable to chloride levels below 1.0 wt.-%/cem (considering a chloride redistribution) with a low risk.  相似文献   

    

Dipl.-Ing. Dr. techn. Michael Reiterer  Assoc. Prof. Dipl.-Ing. Dr. techn. Alfred Strauss  Dipl.-Ing. Dr. nat. techn. Hannes Kari 《Beton- und Stahlbetonbau》2021,116(3):170-182

Approaches for the performance-based condition assessment and lifetime prognosis of engineering structures The contribution discusses approaches for the performance-based condition assessment including consequence class concepts and service life prediction procedures of complex high loaded structural components as used in railway engineering. These approaches are based on hybrid monitoring and modelling based reliability index concepts and includes the merging of the results from purely visual status checks of engineering constructions with existing expert knowledge from tests and calculations. Using artificial intelligence (AI) methods, the condition classes from the heuristic visual inspection and the existing expert knowledge for refined determination of the condition-dependent reliability index under consideration of the corresponding damage consequence classes (CCn) at a certain age are used. Four different models for the prognosis of the future state development / degradation and the expected lifespan of the considered engineering construction are presented. These methodical approaches are outlined using the example of a dynamically stressed noise barrier construction due to train passing for condition assessment and (remaining) service life forecast.  相似文献   

    

Stefan Rappl  Dr.-Ing. Kai Osterminski  Shima Ansary  Florian Hiemer 《Beton- und Stahlbetonbau》2021,116(3):232-239

Fatigue behaviour of reinforcing steel in the very-high-cycle-fatigue regime N ≥ 10 millions The fatigue behaviour of reinforcing steels in the very-high-cycle-fatigue regime is almost unexplored. Especially wind turbines (on- and offshore) are exposed to these high numbers of cycles caused by wind and tide. 80 reinforcing steels with two different diameters (10 and 16 mm) were tested on three different stress ranges for investigating into this topic. All experiments ran in a high frequency pulsator with a frequency of about 100 Hz, some of them reached up to 100 million numbers of cycles. The surface quality of the specimen with a larger diameter had a great influence on the fatigue behaviour. These specimen failed early at areas with surface damages caused by the rolling or straightening process. The thinner specimen reached the given number of cycles without any failure. A great increase of the failure type «breakage» could be detected with increasing stress range. This was independent of the specimen diameter. A greater decrease of the survival probability was detected for specimen with a larger diameter. The surface of run-out specimen was examined by a scanning electron microscope. Many cracks have been detected especially at areas with high notch stresses like rib feet or notches caused by the straightening process.  相似文献   

    

Michael Vospernig Dipl.-Ing.  Bernhard Glatz Dipl.-Ing.  Dipl.-Ing. Dr. techn. Michael Reiterer  Univ.-Prof. Dipl.-Ing. Dr. techn. Josef Fink 《Stahlbau》2021,90(4):271-283

Truss-girder bridges – evaluation of dynamic responses of the deck due to train transit – comparison between computational results and measurement During route expansion projects between 2013 and 2019 by the Austrian Federal Railways (ÖBB), three steel truss bridges with a similar design were built as single-span structures with spans of 42 to 68 m. According to the ÖBB regulations dynamic analyses must be carried out. In the first investigation step, the computation of the train transit uses the normative loads for the moving load model. With all three examined structures it can be shown that the harmonics of the bridge deck lead to vertical accelerations exceeding serviceability limit states. In the next investigation step, system identifications are performed to determine the actual Lehr's damping ratios as well as eigenfrequencies and mode shapes of the structures. Further calculations with a detailed interaction model are investigated to prove the moving load model and the application of vibration absorbers at the computational model to dampen the harmonics of the bridge deck is investigated. In the final step, measurements of deck accelerations caused by train transit on the real structures are carried out. A comparison of the calculated and measured vertical accelerations due to train transits demonstrates that the harmonics of the bridge deck at the real structure are not as sensitive as in the numerical model.  相似文献   

    

Martin Geiger  Thorsten Twiehaus  Sven Klingschat  Christoph Geffers 《Stahlbau》2021,90(7):517-527

Comparison of the static strength of arc and laser welded joints – applications of unalloyed steel at butt joints and fillet weld joints in thin sheet metal applications Within the the scope of these investigations, a comparison of arc welded and laser beam welded joints will be carried out with focus on their achievable static strengths. To receive a comparison relevant to practical applications, the two welding processes and their influence on the joint design of the joint will be considered. This can be explained by using the example of the fillet weld. While in arc welding a fillet weld is usually characterized by their (design throat thickness) a-measurement, in laser beam welding without filler material a full connection between web and base plate is usually aimed. The aim of this investigation is to examine the welded joints, which are designed differently depending on the welding process, about the respective achievable static strengths and to compare the results. For sheet thicknesses < 6 mm, all samples achieve comparable strength. In the case of the 6 mm fillet welds, laser welded on one side, failure has occurred in the weld due to the lack of a full bond connection.  相似文献