Robustness of Modular Timber Buildings

Abstract

Increasing housing demand in Europe and the need to be more sustainable are asking the construction industry to leave the traditional pathways and innovate. An emerging construction method with volumetric timber modules potentially offers the solution. However little is known about the robustness of this new innovation. Therefore, this thesis aims to advance the current research regarding collapse resistance in volumetric modular timber buildings. To achieve that goal, first, in this thesis, a literature study into robustness and modular buildings was performed. The study identified the importance of redundancy, proper connection design, ductility, and tying in modular structures for robustness. Secondly a case study was performed. The case study provided the structural design concept of a newly developed volumetric timber post and beam module by Lister Buildings, structurally designed by Pieters Bouwtechniek. The modules consist of glued laminated beams and columns with cross-laminated floor and ceiling slabs. With the modules, a hypothetical residential building of 5 storeys was created, which consecutively was decomposed into equivalent two-dimensional frame structures suited for 2D finite element analysis. To account for the mechanical behaviour of the connections in the models, nonlinear springs were used. To establish the springs, the component method was adopted. The spring behaviour was determined from the elastic, plastic and failure performance of the individual components of a connection in translational and rotational degrees of freedom. Then based on a notional element removal concept, multiple possible loss events of load bearing elements were analysed in the finite element software of Abaqus to examine the existence and development of alternative load paths. To do that, both nonlinear static and nonlinear dynamic analyses were performed. The results of this study indicate that the new design concept performs quite well on robustness. Several alternative load paths were identified, among which cantilever action, bridging action, and catenary action, depending on the removal event and scenario. In addition this thesis investigated the dynamic amplification factor (DAF) of the modular system. The results of this research imply that for alternative load path analysis of timber structures, a DAF of 2.0 should be applied in a (non)linear static analysis. More research will be necessary to examine whether a lower value than 2.0 can be used.