Automatic joinery has become a common technique for the jointing of beams in timber framing and roofing. It has revived traditional, integrated joints such as mortise and tenon connections. Similarly, but only recently, the automatic fabrication of traditional cabinetmaking joints has been introduced for the assembly of timber panel shell structures. First prototypes have used such integrated joints for the alignment and assembly of components, while additional adhesive bonding was used for the load-bearing connection. However, glued joints cannot be assembled on site, which results in several design constraints.In this paper, we propose the use of dovetail joints without adhesive bonding, on the case study of a timber folded plate structure. Through their single-degree-offreedom (1DOF) geometry, these joints block the relative movement of two parts in all but one direction. This presents the opportunity for an interlocking connection of plates, as well as a challenge for the assembly of folded plate shells, where multiple non-parallel edges per plate must be jointed simultaneously.

Structural behaviour of timber folded surface systems greatly depends on the connections ability to transfer the occurring forces between the adjacent elements and finally to the supports. This paper focuses on multiple tab-and-slot joints (MTSJ), where digital prefabrication is used to integrate connectors through plate geometry. Multiple plates assembled within a large scale folded surface structure were tested to examine the influence of connection detail type on its global structural behaviour. For this purpose an innovative test setup was devised that approximates uniformly distributed surface load. The connection details used were chosen with respect to preliminary small scale bending tests. Three groups of distinct large scale structures were tested: 1) structures with miter joint detail and adhesive applied along the edges; 2) structures with open slot MTSJ; and 3) structures with closed slot MTSJ. Extensive investigation into the load bearing behaviour and failure propagation for each of the three different types of structures has been conducted.For analysing their feasibility, the tested structures were also reviewed in terms of fabrication time, assembly and on-site construction. The obtained results show that even though adhesively joined structures provide highest structural stiffness, they exhibit multiple disadvantages when considering building scale applications. Open slot MTSJ structures results indicate that these joints cannot provide sufficiently reliable structural behaviour. Structures with MTSJ closed slots show that their joint geometry greatly improves both the ultimate load-bearing capacity as well as stiffness. Furthermore, by transferring the edge occurring forces mainly in compression, they provide additional ductility to the global system. Within the scope of this paper, closed slot MTSJ proved to be a very efficient connection type which can constitute a robust folded structural system made as a multiple assembly of thin timber plates.

Timber folded surface structures assembled using semi-rigid multiple tab and slot joints (MTSJ) have been shown to form feasible structural systems with high load bearing potential. However, for their further development and use on large building scales, a pertinent model for prediction of their structural behaviour has yet to be developed. This paper focuses on simplified numerical methods for accurately modelling the semi-rigid structural behaviour of bidirectional timber folded surface structures with multiple tab and slot connections. Within this scope, the structure behaviour is considered to be in the elastic stage. Three practical methods of analysis for such structural systems are presented. The first two approaches use the Finite Element Method (FEM), where the theory of plates and shells are applied. In the first method, the MTSJs are modeled using strip element models, while, in the second strategy, spring models are used. The third modeling strategy elaborates on the new macroscopic mechanical models, referred to as macro models. Sets of one-dimensional (1D) elements are used to represent the mechanical behaviour of the entire system. Both linear and geometric nonlinear analysis are performed for all three modeling strategies. The numerical results are then validated against the large scale experiments. Comparison of the strip and spring element model results have shown that the strips represent more accurately the experimentally obtained values. Concerning the macro modelling approach, very good agreement with both detailed FE modelling approaches, as well as experimental results, were obtained. The results indicate that both linear and nonlinear analysis can be used for modelling the displacements within the elastic range. However, it is essential to include geometric nonlinearities in the analysis for accurate modelling of occurring strains as well as for displacements when considering higher load levels. Finally, it is demonstrated that including semi-rigidity in the numerical models is of high importance for analysing the behaviour of timber folded surface structures with MTSJ.

This paper analyses the potential of different possible folded form topologies for generating timber folded surface structures. The main advantage of such structures lies primarily in the realm of ecology and sustainability. By offering an integral way of construction, which fulfils both a supporting as well as a covering function, very lightweight structures are achieved. Also, greater degree of prefabrication is possible which leads to reduced overall cost. Timber folded structures consist of a large number of discrete, thin plane elements, mutually connected to form an overall folded surface. Therefore proper edgewise connection details are needed in order to ensure an efficient load bearing system. For structures made of wood products this presents a great challenge using the state-of-the art joining techniques. For this reason, the use of timber folded plates in civil engineering applications has been very limited. However, recently new technical solutions have been proposed for efficient edgewise joining of thin timber panels. In this paper focus is put on integrated mechanical attachment technique which utilises digital prefabrication to integrate connectors through panel geometry. Taking into consideration material, fabrication and connection detail constraints, various topologies are examined for the considered application. Furthermore, structural behaviour of folded systems is studied and three feasible forms are compared by means of Finite Element Analysis. Finally, observations are made on a case study of a built prototype structure and the structural potential of the proposed systems is outlined.

<p>This paper analyses the potential of different possible folded form topologies for generating timber folded surface structures. The main advantage of such structures lies primarily in the realm of ecology and sustainability. By offering an integral way of construction, which fulfils both a supporting as well as a covering function, very lightweight structures are achieved. Also, a greater degree of prefabrication is possible which leads to a reduced overall cost. As these structures consist of a large number of discrete, thin plane elements, proper edgewise connection details are needed in order to ensure an efficient load bearing system. For structures made of wood products this presents a great challenge using the state-of-the art joining techniques. For this reason, the use of timber folded plate structures in civil engineering applications has been very limited. However, recently new technical solutions have been proposed for efficient edgewise joining of thin timber panels. In this paper focus is put on integrated mechanical attachment technique which utilises digital prefabrication to integrate connectors through panel geometry. Considering the material and the chosen connection detail fabrication as well as assembly related constraints, feasible folded forms for folded surface structures are explored. Their influence on structural performance is studied and different forms are compared by means of Finite Element Analysis. Furthermore, based on the obtained results, form improvements are proposed and observations made on a case study of a built prototype structure are presented.</p>