Dr.-Ing.

Albrecht, Stefan

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  • Publication
    Reliability as a Key Driver for a Sustainable Design of Adaptive Load-Bearing Structures
    ( 2022-01-13)
    Efinger, Dshamil
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    Ostertag, Andreas
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    Dazer, Martin
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    Borschewski, David Sven
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    Albrecht, Stefan orcid-logo
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    Bertsche, Bernd
    The consumption of construction materials and the pollution caused by their production can be reduced by the use of reliable adaptive load-bearing structures. Adaptive load-bearing structures are able to adapt to different load cases by specifically manipulating internal stresses using actuators installed in the structure. One main aspect of quality is reliability. A verification of reliability, and thus the safety of conventional structures, was a design issue. When it comes to adaptive load-bearing structures, the material savings reduce the stiffness of the structure, whereby integrated actuators with sensors and a control take over the stiffening. This article explains why the conventional design process is not sufficient for adaptive load-bearing structures and proposes a method for demonstrating improved reliability and environmental sustainability. For this purpose, an exemplary adaptive load-bearing structure is introduced. A linear elastic model, simulating tension in the elements of the adaptive load-bearing structure, supports the analysis. By means of a representative local load-spectrum, the operating life is estimated based on Woehler curves given by the Eurocode for the critical notches. Environmental sustainability is increased by including reliability and sustainability in design. For an exemplary high-rise adaptive load-bearing structure, this increase is more than 50%.
  • Publication
    Sustainable Shape Memory Polymer Foams
    ( 2022)
    Walter, Mario
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    Pretsch, Thorsten
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    Borschewski, David Sven
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    Albrecht, Stefan orcid-logo
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    Lengsfeld, Kristin
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    Mügge, Maximilian
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    Lehmann-Brauns, Susanne orcid-logo
    Today, polymer foams are used in numerous industries such as automotive, consumer goods, construction, medical and aerospace. The thermal and mechanical properties of water-blown polyurethane (PUR) foams can be varied over a wide range, depending on the starting materials used to produce them. After thermomechanical treatment, also known as programming, certain PUR foams exhibit a self-sufficient switching behavior during heating and cooling. This can add value and enable new applications. Here, we introduce new polyurethane foams that are able to thermoreversibly change shape. This functionality, combined with good insulating properties, paves the way for novel concepts for material-inherent thermal management. By selecting the molecular building blocks, the switching temperature range and foam properties can be tailored. The sustainability of the materials can also be increased by customized formulations. Bio-based raw materials lead to a high proportion of renewable carbon, while the selection of linear building blocks enables the formation of thermoplastic polymers that can be mechanically recycled, for example. The ecological impact of such materials and the thermal management concepts based on them can be estimated with the aid of life cycle assessments. Financial support from Fraunhofer Cluster of Excellence Programmable Materials, grant number 40-03549-2500-00002, is kindly acknowledged.
  • Publication
    The dilemma of balancing design for impact sound with environmental performance in wood ceiling systems - A building physics perspective
    ( 2021)
    Müller, Theresa
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    Borschewski, David Sven
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    Albrecht, Stefan orcid-logo
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    Leistner, Philip
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    Späh, Moritz
    Due to the high consumption of resources and energy in the construction sector, the development of resource-efficient and sustainable construction solutions is gaining increasing attention. The awareness of sustainability and resource conservation results in the interest of using natural and renewable materials in contemporary architecture. Timber construction methods offer both constructive and ecological potential for sustainable solutions. From a building physics perspective, the acoustic performance of lightweight buildings, such as those made of timber, presents a challenge. Even if standard requirements are met, the increased low-frequency sound transmission typical for light-weight construction can cause discomfort and is already the subject of questions in building physics, which are currently increasingly extending to timber construction. Within the framework of a holistic approach, this paper compares the problem of acoustic properties, design optimizations and the ecological properties of timber-frame and solid timber construction components. The comparison with heavy materials, such as concrete, shows the relation of acoustic optimization with the change of the environmental profile. In order to establish the interaction between acoustic quality of wooden ceiling constructions and their ecological characteristics, this article aims to demonstrate the potential of materials used in the building sector under ecological aspects considering a life cycle analysis.