Post-earthquake structural damage shows that out-of-plane (OOP) wall collapse is one of the most common failure mechanisms in unreinforced masonry (URM) buildings. This issue is particularly critical in Groningen, a province located in the northern part of the Netherlands, where low-intensity induced earthquakes have become an uprising problem in recent years. The majority of buildings in this area are constructed using URM and were not designed to withstand earthquakes, as the area had never been affected by tectonic seismic activity before. OOP failure in URM structures often stems from poor connections between structural elements, resulting in insufficient restraint to the URM walls. Therefore, investigating the mechanical behaviour of these connections is of prime importance for mitigating damages and collapses in URM structures. This paper presents the results of an experimental campaign conducted on timber joist-masonry cavity wall connections. The specimens consisted of timber joists pocketed into masonry wallets. The campaign aimed at providing a better understanding and characterisation of the cyclic axial behaviour of these connections. Both as-built and strengthened conditions were considered, with different variations, including two tie distributions, two pre-compression levels, two different as-built connections, and one strengthening solution. The experimental findings underscored that incorporating retrofitting bars not only restores the system's initial capacity but also guarantees deformation compatibility between the wall and the joist. This effectively enhances the overall deformation capacity and ductility of the timber joist-cavity wall system.
In recent years, the number of human-induced earthquakes in Groningen, a large gas field in the north of the Netherlands, has increased. The majority of the buildings are built by using unreinforced masonry (URM), most of which consists of cavity (i.e. two-leaf) walls, and were not designed to withstand earthquakes. Efforts to define, test and standardize the metal ties, which do play an important role, are valuable also from the wider construction industry point of view. The presented study exhibits findings on the behavior of the metal tie connections between the masonry leaves often used in Dutch construction practice, but also elsewhere around the world. An experimental campaign has been carried out at Delft University of Technology to provide a complete characterization of the axial behavior of traditional connections in cavity walls. A large number of variations was considered in this research: two embedment lengths, four pre-compression levels, two different tie geometries, and five different testing protocols, including monotonic and cyclic loading. The experimental results showed that the capacity of the connection was strongly influenced by the embedment length and the geometry of the tie, whereas the applied pre-compression and the loading rate did not have a significant influence.
The seismic assessment of unreinforced masonry (URM) buildings with cavity walls is of high relevance in regions such as in Central and Northern Europe, Australia, New Zealand and China because of the characteristics of the masonry building stock. A cavity wall consists of two separate parallel walls usually connected by metal ties. Cavity walls are particularly vulnerable to earthquakes, as the out-of-plane capacity of each individual leaf is significantly smaller than the one of an equivalent solid wall. This paper presents the results of an experimental campaign conducted by the authors on metal wall tie connections and proposes a mechanical model to predict the cyclic behaviour of these connections. The model has been calibrated by us- ing the experimental results in terms of observed failure modes and force-displacement responses. Results are also presented in statistical format.
Horticulture crops and plants use only a limited part of the solar spectrum for their growth, the photosynthetically active radiation (PAR); even within PAR, different spectral regions have different functionality for plant growth, and so different light spectra are used to influence different properties of the plant, such as leaves, fruiting, longer stems and other plant properties. Artificial lighting, typically with LEDs, has been used to provide these specified spectra per plant, defined by their light recipe. This light is called steering light. While the natural sunlight provides a much more sustainable and abundant form of energy, however, the solar spectrum is not tuned towards specific plant needs. In this project, we capitalize on recent breakthroughs in nanoscience to optimally shape the solar spectrum, and produce a spectrally selective steering light, i.e. convert the energy of the entire solar spectrum into a spectrum most useful for agriculture and plant growth to utilize the sustainable solar energy to its fullest, and save on artificial lighting and electricity. We will take advantage of the developed light recipes and create a sustainable alternative to LED steering light, using nanomaterials to optimally shape the natural sunlight spectrum, while maintaining the increased yields. As a proof of concept, we are targeting the compactness of ornamental plants and seek to steer the plants’ growth to reduce leaf extension and thus be more valuable. To realize this project the Peter Schall group at the UvA leads this effort together with the university spinout, SolarFoil, whose expertise lies in the development of spectral conversion layers for horticulture. Renolit - a plastic manufacturer and Chemtrix, expert in flow synthesis, provide expertise and technical support to scale the foil, while Ludvig-Svensson, a pioneer in greenhouse climate screens, provides the desired light specifications and tests the foil in a controlled setting.
Nederlandse glastuinbouwbedrijven, onderzoekers en technologie spelen een grote rol in de voedselvoorziening wereldwijd. De productiviteit ligt hier door de kennis en kunde hoog, met een kleine footprint in vergelijking met producenten in andere landen. Met de huidige bevolkingsgroei en druk op veilige en duurzame voedselvoorziening in het achterhoofd, leveren onderzoekers en ondernemers een versterking van de glastuinbouwsector. De inzet van sensoren, data en data-analyse is gewenst om groei en opbrengst beter te monitoren, ziektes beter te bestrijden, en de footprint verder te verkleinen. Nederlandse telers zijn proeftuinen voor deze innovaties: zij experimenteren als eerste, om technologieën of methoden toe te kunnen passen en tegen lagere kosten meer te produceren. Innovatieagenda’s van betrokken topsectoren dragen sterk bij aan deze ontwikkelingen. Dit project stelt data over de plant centraal. Nu heeft een teler data over zijn klimaat, hij of zij ziet zelf iets met de plant gebeuren en past dan klimaat aan. Dit project zorgt voor meer data over de plant zelf, zodat de telers de teelt directer kunnen aansturen, met betere opbrengst en lagere kosten tot gevolg. In dit project wil het consortium van onderzoekers en ondernemers een grote stap zetten naar grootschalige toepassing van sensortechnologie voor het volgen van gewasgroei. Daarvoor moeten te ontwikkelen sensoren zowel low-cost als nauwkeurig zijn. Daarnaast is draadloos en contactloos werken van groot belang. De belangrijkste te meten parameters zijn de kopdikte van het gewas en de Leaf Area Index. Beide parameters samen zeggen iets over de sapstroom en de sapstroom is de belangrijkste parameter voor de groei van het gewas. Dit project is een vliegwiel voor technologieontwikkeling. Resultaten van het onderzoek en de ontwikkeling, met toeleveranciers, kwekers en veredelaars samen, kunnen na dit proeftuin-stadium de technologie verder brengen, vooral naar het buitenland, waar de vraag naar Nederlandse kennis en expertise alsmaar groter wordt.
In dit onderzoek werken de Hanzehogeschool Groningen en The Leaf samen aan het ontwikkelen en testen van een oplossing voor klimaatproblemen in (binnen)steden. Een ‘Leaf’ is een groene pergola die op meerdere thema’s als hittestress, wateroverlast, biodiversiteit en circulariteit inspeelt. Doel van dit onderzoek is om de effectiviteit, haalbaarheid en rendabiliteit van een Leaf in de praktijk te toetsen. Centraal in dit onderzoek staat het ontwikkelen van meerdere prototypes met verschillende karakteristieken, en deze met verschillende onderzoeksmethodes testen en vergelijken. Het onderzoek wordt met een interdisciplinair team van studenten en onderzoekers en ondersteuning van verschillende experts uit de praktijk uitgevoerd.
