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Multi-storey buildings require provisions to avoid disproportionate consequences after unexpected events, e.g. explosions or human error during design and construction. To prevent failure progression in the structure after an initial damage (loss of load-carrying elements), alternative load paths, like catenary action, should be provided. Catenary action supports the sagging structure after element loss by transferring the loads horizontally to the adjacent elements; this mechanism requires the connections to remain ductile under high load. Conventional dowel-type connectors in timber structures have limited potential to develop catenary action in beams or floors. A previously developed tube connector exhibited desirable behaviour to develop catenary action in cross-laminated timber floors; however, the tube exhibited and undesirable failure mode. In the present study, the behaviour of a newly designed variant of the tube connector was experimentally investigated under catenary action. The new connector design was tested in varying configurations, at both the component level and full-scale floor level, in Canada and Sweden. The results show that a more desirable behaviour of the adapted connector could be achieved compared to the previous design, with respect to catenary action., Funder: Government of British Columbia;ISBN för värdpublikation: 9781713873273, 9781713873273, Främja ökat byggande av flerfamiljshus i trä, Tallwood

NLDA Masterthesis, De huidige golf aan doorbraken op het gebied van Artificiële Intelligentie (AI), begonnen in het afgelopen decennium, wordt gedreven door de toenemende beschikbaarheid van grote hoeveelheden informatie en geavanceerde technologie. Hoewel AI voornamelijk is voortgekomen uit het civiele domein, zien militaire grootmachten inmiddels de potentie van AI voor oorlogvoering in de 21e eeuw. Echter waarschuwen verscheidene academici voor ingrijpende gevolgen van de toenemende militaire applicatie van AI. Er is een debat ontstaan waarbij AI verschillende escalerende gevolgen heeft: ondermijning van deterrence, een AI-wapenwedloop of zelfs het ontstaan van zogenoemde ‘hyperoorlogen’. Indien dit het geval is, is AI een directe bedreiging voor strategische stabiliteit. Deze thesis test de bovengenoemde hypothesen en onderzoekt de impact van militaire AI op strategische stabiliteit. Hiertoe wordt gebruik gemaakt van een framework gebaseerd op het concept ‘strategische stabiliteit’ in combinatie met deterrence- en arms race theorie. De thesis onderzoekt in hoeverre AI in militaire systemen voldoende potentieel heeft om een effect te hebben op strategische stabiliteit voor 2030. Hierbij worden de Verenigde Staten (VS), China, Rusland en Europese NAVO-lidstaten geanalyseerd op het gebied van militaire AI-strategie, financiering, AI-ecosystemen en civiel-militaire samenwerking. Het blijkt dat deze actoren met name militaire AI nastreven in drie focusgebieden: autonomie, door AI ondersteunde command & control en door AI gedreven cyber. Binnen deze focusgebieden is beoordeeld wat de technologische gereedheid is van militaire applicaties. Het onderzoek concludeert dat, hoewel het destabiliserende potentieel van AI op de lange termijn strategische stabiliteit kan beïnvloeden, de huidige waarschuwingen genuanceerd moeten worden. De technologie staat namelijk nog in de kinderschoenen op het gebied van oorlogvoering en de AIsystemen die strategische stabiliteit in gevaar zouden kunnen breng

Den platt- och skivlösare som utvecklats inom projektet Träinnovation i Norr (TiiN) har vidareutvecklats för beräkning av ortotropa skivor och plattor. Den vidareutvecklade lösaren är att betrakta som ett steg på vägen mot det långsiktiga målet att utveckla en enkel men riktig platt- och skivlösare för KL-trä. Plattlösaren har med goda resultat verifierats mot såväl en konstruerad lösning som mot beräkningar i Abaqus. Det har tyvärr inte varit möjligt att inom ramen för projektet verifiera skivlösaren.

Multi-storey buildings require mitigation of consequences of unexpected or accidental events, to prevent disproportionate collapse after an initial damage. Cross-laminated timber (CLT) in platform-type construction is increasingly used for multi-storey buildings, however, the collapse behaviour and alternative load paths (ALPs) are not fully understood. A 3D non-linear component-based finite element model was developed for a platform-type CLT floor system to study the ALPs after an internal wall loss, in a pushdown analysis. The model, which accounted for connection failure, timber crushing and large displacements, was calibrated to experimental results and then adapted for boundary conditions corresponding to typical residential and office buildings. Subsequently, five parameters (floor span, connection type, vertical location of the floor, tying level, horizontal wall stiffness) were varied, to study their effects on the ALPs in 80 models. The results showed that three ALPs occurred, of which catenary action was the most dominant. Collapse resistance was mainly affected by the floor span, followed by the axial strength, stiffness and ductility of the floor-to-floor connection, the weight of the level above and the floor panel thickness. This study provides an approach to model ALPs in a platform-type CLT floor system to design disproportionate collapse resistant multi-storey CLT buildings., Validerad;2021;Nivå 2;2021-05-19 (beamah)

This work was focused on the experimental testing and finite element analysis (FEA) of timber beams with and without flaws (different types of cracks and hole). The aim was analysing the effect of flaws on their load-carrying capacity. This topic is important for designers of timber constructions, since even today there is still a lack of knowledge in the field of fracture mechanics of wood. The results from experimental testing and numerical simulations were discussed in this paper. Two wood products were analysed, namely, sawn and glued laminated beams (glulam beams) and three types of flaws were considered for both products i.e. a vertical crack, an oblique crack and a circular hole. In addition for glulam beams the horizontal crack in the glue line was considered. Four-point bending test was created for experimental testing considering quasi-brittle characteristic of wood. 4 samples for each type of beam, 36 in total. XFEM (Extended Finite Element Method) was used for finite element analysis of beams with considering orthotropic-elastic properties for glulam beams were considered and The results of mechanical tests and FEA gave us an overview on how different types of flaws influence the load-carrying capacity of sawn and glulam beams and with what accuracy we can simulate cracks in wood using computational method.

Timber buildings are increasing in their dimensions. Structural robustness is imperative for all buildings and specifically important for tall buildings. Lives can be saved if disproportionate collapse can be avoided after a catastrophic event (e.g. accident, terrorism). The literature about robustness is comprehensive concerning concrete and steel buildings, but is rather limited regarding timber. This paper reviews robustness in general and robustness of timber buildings in particular. Robustness is an intrinsic structural property, enhancing global tolerance to local failures, regardless of the cause. A deterministic approach to assess robustness is to remove certain load-bearing elements from the structure and compare the consequences to given limits. Design methods for robustness may be direct by assessing effects of local failure, or indirect by following guidelines. For robust timber buildings, the connections are the key aspects. Usually, metal connectors may provide the required joint ductility. For robust light timber-frame construction, rim beams may be designed. For timber posts and beams and cross laminated timber, guidance regarding robustness is scarce, but in some aspects they seem to be similar to steel frames and precast concrete. Future research should assess the capacity of connections, and evaluate the adequacy of seismic connectors for robust timber buildings., Validerad;2019;Nivå 2;2019-02-15 (johcin), Vinnova BioInnovation 4.4

A shortcoming of the laminated bending process is that the product may become distorted after moulding. This study focused on the influence of fibre orientation deviation for individual veneers on the distortion of a moulded shell. The distortion of 90 cross-laminated shells of the same geometrical shape, consisting of seven peeled birch veneers, were studied under relative humidity variation. All the veneers were straight-grained in the longitudinal-tangential plane, but to simulate a deviation in fibre orientation, some of the individual veneers were oriented at an angle of 7° relative to the main orientation of the other veneers in the laminate. A finite element model (FEM) was applied to study the possibility of predicting the results of a practical experiment. The study confirms the well-known fact that deviation in fibre orientation influences shape stability. The results also show how the placement of the abnormal veneer influences the degree of distortion. From this basic knowledge, some improvements in the industrial production were suggested. However, the FE model significantly underestimated the results, according to the empirical experiment, and it did not show full coherence. The survey shows the complexity of modelling the behaviour of laminated veneer products under changing climate conditions and that there is a great need to improve the material and process data to achieve accurate simulations. Examples of such parameters that may lead to distortion are density, annual ring orientation in the cross section of the veneer, the orientation of the loose and tight sides of the veneer, and parameters related to the design of the moulding tool.