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Calibration method for constant strands of material with robot‐assisted concrete extrusion Robot‐assisted concrete extrusion is a complex, new type of additive manufacturing process in which strategy, material and conveyor system must be specifically coordinated with one another. In particular, the real shape of the extruded material strand is subject to significant fluctuations along the starting point, via the main extrusion phase, until the switch‐off process due to local over‐ and under‐extrusions, which usually do not meet the quality requirements. In this work, an efficient calibration process is used to develop the calibration method for the extrusion process according to the algorithm developed, to adjust and test it on the software side, and to examine the effects of the feed rate on the component quality. In this article, the efficient calibration of the extrusion process according to the developed method is compensated on the software side and the effects of the feed rate on the component quality are investigated. For this purpose, different calibration methods of current additive manufacturing processes were considered and evaluated with regard to their usability for the extrusion of mineral suspensions. Building on this, a general procedure for calibration and its practical implementation was theoretically developed. In the function tests carried out the method reduced the process preparation, increased process reliability through the stabilized extrusion and shortened the cycle time. This increase in productivity in additive manufacturing allows the use of high‐strength lightweight structures in construction and enables the serial implementation of free‐form modular designs. [ABSTRACT FROM AUTHOR]

Structural monitoring for safeguarding the remaining life time of a bridge building endangered by stress corrosion cracking Initial point of the structural monitoring of the bridge over the railway in Waren (Müritz) were the results of recalculation and the investigations of the prestressed wires. In this regard it was documented, that the bridge is in fact endangered by stress corrosion cracking, but ductility provides a sufficient prior notice of failure. Thus the further use of the bridge is possible, provided of a shortened inspection interval. Due to ongoing use the inspection of the building is possible to a limited extend only, the necessary frequent visual assessment was replaced by a structural monitoring. So the focus was not on the complete measurement based observation of the building. The main aim of the structural monitoring rather was the purposeful and economical registration of possibly developing bending cracks. During the monitoring period of two years the development of a bending crack under service load was detected and thereby the real arise of the crack-before-failure-criterion was confirmed. The paper shows the principle procedure of collecting information as basis for a safe decision making as well as on planning, execution and evaluation of structural measurements and their integration into the assessment process of the structure. [ABSTRACT FROM AUTHOR]

Im konstruktiven Brückenbau sind die Instandhaltungsstrategien und die damit verbundenen Investitionskosten von der Bauart, der Qualität und vom Entwurfskonzept abhängig. Heutzutage neigen Brückenbetreiber und Planer beim Bau von Brücken dazu, Lebenszyklusanalysen in ihren Entscheidungsprozess aufzunehmen, um die Gesamtwirkung, die strukturelle Zuverlässigkeit und Langlebigkeit sowie den finanziellen Aufwand zu optimieren. Dennoch führen Bemühungen, die zu erwartenden Lebenserhaltungskosten mittels bewährten Konstruktionsprinzipien zu reduzieren, zu unbekannten Risiken. Permanente als auch kurzfristige Monitoring-Konzepte können die Unsicherheiten neuer Konzepte durch Beobachtung der Leistung der Bauteile während einer vorgeschriebenen Zeitdauer reduzieren. Die Ziele dieser Arbeit sind die Diskussion der wirksamen Einbeziehung von Monitoring-Daten im Modell durch Einflusslinien- und Modellkorrekturfaktoren-Konzepte, die Untersuchung der Funktionalität der Monitoring-Systeme einschließlich Fehlerbehebung und die inverse Ermittlung und Bewertung der Sensor-Eigenschaften und Überwachung der Daten. Die vorgeschlagene Methodik wird an einem bestehenden fugenlosen Dreifeldbrückensystem als integratives Überwachungssystem angewendet. Novel monitoring techniques for abutment free bridge structures In structural bridge engineering, maintenance strategies and thus budgetary demands are highly influenced by construction type and quality of design. Nowadays bridge owners and planners tend to include life-cycle cost analyses in their decision processes regarding the overall design trying to optimize structural reliability and durability within financial constraints. However, efforts to reduce maintenance costs over the expected lifetime by adopting well established design principles lead to unknown risks concerning for instance boundary conditions. Smart permanent and short term monitoring concepts can reduce the associated risk of new design concepts by observing the performance of structural components during prescribed time periods. The objectives of this article are the discussion of concepts for (a) the effective incorporation of monitoring data in model updating procedures by means of the influence line and the model correct factor concept, (b) the investigation of the functionality of monitoring systems including error tracking, and (c) the inverse identification and evaluation of sensor properties and monitoring values. The proposed methodology will be applied to an integrative monitoring system applied on an existing three-span joint less bridge structure. [ABSTRACT FROM AUTHOR]