Papers by Keyword: Resilience

Abstract: The flood caused by the heavy rainfall during July and August 2022 in Balochistan led to massive and widespread damage to the infrastructure and lifelines. A total of 6953.83 km of roads and 435 bridges were damaged in Pakistan. To prevent such losses and create a climate-resilient transport infrastructure system by creating bridges strong enough to endure various natural challenges with minimal harm and swiftly recover their functionality, this study used the data from 35 flood-affected bridges in Balochistan as a case study to create patterns and relationships between flood disaster and bridge failure mechanisms. Using qualitative data from field visits, the bridges were statistically analyzed for failure modes such as geological and structural failure, and for damage states including slight, moderate, extensive, and completely washed out. Then all possible failures in each component of the substructure and superstructure were observed. After data interpretation, it was disclosed that most bridges were moderately damaged, accounting for 37.14% of the total, with 62.86% experiencing a combination of geological and structural failures. The abutments, wing walls, and approaches were identified as the most affected components. Based on these findings, practical recommendations are proposed to mitigate the possible failures due to floods.

Abstract: The aim of this study was to investigate the influence of thermo-cyclic treatments on the mechanical characteristics (Hardness and Resilience) of low-alloy 42CD4 steel. Thermocyclic treatment on 42CD4 steel was operated for four cycles at 850 °C for 30 min. After each cycle, the steel sample was cooled in different medium (open air and water) in order to check the effect of the cooling rate on the microstructure characteristics. It was found that the cooling rate can affect the mechanical characteristics of the steel. The hardness values of steel cooled in water were higher than those of steel cooled in air. Additionally, there was an increase in the resilience of steel sample with the increase of thermocyclic number.

Abstract: This study investigated the effects of the reinforcement positions and the number of shape memory alloys (SMAs) on the structural characteristics of highly intelligent hybrid fiber reinforced concrete (hereinafter, HIHFR) beams. First, tests were conducted under monotonic loading conditions. To examine such structural characteristics, the load-deflection curve relationship and crack patterns, temperature and energy absorption, temperature and displacement ductility, displacement ductility and energy absorption, and the relationship between the displacement ductility and resilience were compared and analyzed. The reinforced concrete beam (RCB) exhibited somewhat excellent values in terms of displacement ductility, but showed the lowest values in terms of strength, resilience, and energy absorption capacity. HIHFR1 exhibited the most excellent results among the test samples in terms of resilience and energy absorption capacity. Therefore, SMAs were partially substituted for the compressive, tension, and shear reinforcement of the existing RCBs. As a result, the substitution for the compressive and tension reinforcement exhibited the best results, confirming the possibility of using SMAs as a substitute for steel reinforcement.

Abstract: Narrow tolerances are commonly used to control uncertainty in the production of technicalcomponents. However, narrow tolerances lead to financial expense and limit flexibility. In this paperthe concept of a resilient process chain is presented. This concept covers the product life cycle phases ofproduction and usage. It is enabled by the digitalization in mechanical engineering and offers access tovariable process windows instead of rigid tolerances. First steps of this concept are then applied to the TU Darmstadt active air spring. The active air spring can be used to increase the driving comfort in avehicle or, for instance, to minimize kinetosis during autonomous driving. The focus hereby is toidentify possible production influences on the behaviour of the components usage. For this purpose, theactuator of the active air spring is specifically manufactured with typical uncertainty of high precisionmachining of the bore and characterized experimentally in a test rig. The results show an influenceof the production on the efficiency of the actuator. The measurements are fundamental to establish aresilient process chain on the active air spring.

Abstract: Given industrial applications, the costs for the operation and maintenance of a pump system typically far exceed its purchase price. For finding an optimal pump configuration which minimizes not only investment, but life-cycle costs, methods like Technical Operations Research which is based on Mixed-Integer Programming can be applied. However, during the planning phase, the designer is often faced with uncertain input data, e.g. future load demands can only be estimated. In this work, we deal with this uncertainty by developing a chance-constrained two-stage (CCTS) stochastic program. The design and operation of a booster station working under uncertain load demand are optimized to minimize total cost including purchase price, operation cost incurred by energy consumption and penalty cost resulting from water shortage. We find optimized system layouts using a sample average approximation (SAA) algorithm, and analyze the results for different risk levels of water shortage. By adjusting the risk level, the costs and performance range of the system can be balanced, and thus the system's resilience can be engineered.

Abstract: Load-carrying systems often suffer from unexpected disruptions which can cause damages or system breakdowns if they were neglected during product development. In this context, unexpected disruptions summarize unpredictable load conditions, external disturbances or failures of system components and can be comprehended as uncertainties caused by nescience. While robust systems can cope with stochastic uncertainties, uncertainties caused by nescience can be controlled only by resilient load-carrying systems. This paper gives an overview of the characteristics of resilience as well as the time-dependent resilient behaviour of subsystems. Based on this, the adaptivity of subsystems is classified and can be distinguished between autonomous and externally induced adaption and the temporal horizon of adaption. The classification of adaptivity is explained using a simple example of a joint brake application.

Abstract: Resilience as a concept has found its way into different disciplines to describe the ability of an individual or system to withstand and adapt to changes in its environment. In this paper, we provide an overview of the concept in different communities and extend it to the area of mechanical engineering. Furthermore, we present metrics to measure resilience in technical systems and illustrate them by applying them to load-carrying structures. By giving application examples from the Collaborative Research Centre (CRC) 805, we show how the concept of resilience can be used to control uncertainty during different stages of product life.

Abstract: Advanced computational methods are needed both for the design of large systems and to compute high accuracy solutions. Such methods are efficient in computation, but the validation of results is very complex, and highly skilled auditors are needed to verify them. We investigate legal questions concerning obligations in the development phase, especially for technical systems developed using advanced methods. In particular, we consider methods of resilient and robust optimization. With these techniques, high performance solutions can be found, despite a high variety of input parameters. However, given the novelty of these methods, it is uncertain whether legal obligations are being met. The aim of this paper is to discuss if and how the choice of a specific computational method affects the developer’s product liability. The review of legal obligations in this paper is based on German law and focuses on the requirements that must be met during the design and development process.

Abstract: High-rise water supply systems provide water flow and suitable pressure in all levels of tall buildings. To design such state-of-the-art systems, the consideration of energy efficiency and the anticipation of component failures are mandatory. In this paper, we use Mixed-Integer Nonlinear Programming to compute an optimal placement of pipes and pumps, as well as an optimal control strategy.Moreover, we consider the resilience of the system to pump failures. A resilient system is able to fulfill a predefined minimum functionality even though components fail or are restricted in their normal usage. We present models to measure and optimize the resilience. To demonstrate our approach, we design and analyze an optimal resilient decentralized water supply system inspired by a real-life hotel building.

Abstract: Buckling of slender bars subject to axial compressive loads represents a critical design constraint for light-weight truss structures. Active buckling control by actuators provides a possibility to increase the maximum bearable axial load of individual bars and, thus, to stabilize the truss structure.For reasons of cost, it is in general not economically viable to use such actuators in each bar of the truss structure. Hence, it is an important practical question where to place these active bars. Optimized structures, especially when coupled with active elements to further decrease the number of necessary bars, however, lead to designs, which, while cost-efficient, are especially prone to bardamages, caused, e.g., by material failures. Therefore, this paper presents a mathematical optimization approach to optimally place active bars for buckling control in a way that secures both buckling and general stability constraints even after failure of any combination of a certain number of bars. This allows us to increase the resilience of the system and guarantee stable behavior even in case of failures.