Timber Gridshell Research Articles

Timber gridshells: Numerical simulation, design and construction of a full scale structure

Timber gridshell structures, such as the Multihalle for the federal garden festival in Mannheim or the Downland Museum, have been the result of a creative–generative process that indissolubly ‘welded’ the structural contribution to that of form exploration. The challenging design and construction issues have been typically addressed and resolved in several inventive ways. However, still now, form-finding and erection of timber gridshells present many difficulties. In this regard, this paper aims to provide a series of novel steps to address some of the main design and construction issues that are associated with ‘actively-bent’ timber gridshell structures. First, the main characteristics of the construction process of timber gridshells are described and the basic theoretical concepts for its numerical simulation, through Dynamic Relaxation method, are introduced. Second, a practical method for sizing the laths' cross-section is presented. Third, a new erection technique for timber gridshells is proposed and applied to the construction of a full scale (prototype) structure, the Toledo gridshell 2.0. Fourth, a new bracing system for the same structure, which was built at the Faculty of Architecture, University of Naples Federico II in June–July 2014, is explained and discussed. The paper also highlights the need for further application to validate the techniques explained here, with particular attention being paid for the construction of large scale free-form structures.

Timber gridshells: beyond the drawing board

In March 2011, a week-long workshop that invited participation from all architecture and architectural technology students at Sheffield Hallam University, UK was organised with the objective of enhancing students' thinking and experience by construction thinking. It was aimed at creating a sense of realness to realise a design project collectively. Timber was set as the material of exploration. The students had to make use of bending to design and create a timber gridshell structure. This made use of a quality traditionally felt to be a structural weakness of the material. To do this, students form-found non-mathematically and non-digitally using paper gridmats. This paper describes the aims, activity and outcome of the timber gridshell workshop as a way of preparing architects and technologists of the future and introducing the challenges of architectural design in terms of economics and construction process, aesthetics, effective communication and structural intuition by working with a given material – all important aspects in achieving effective architecture.

Innovative Use and Characterization of Polymers for Timber-Related Construction

Timber gridshells have become a very popular, efficient, sustainable and beautiful structural application of timber. However, given the slender laths involved in this form of construction, there is concern over the durability of timber for this purpose, and Glass FRP (GFRP) laths have been proposed as a possible substitution. This paper considers this possibility. It goes on to look at the possible use of Basalt FRP (BFRP) for the same purpose, from the perspective of its creep characteristics. It is shown that the use of GFRP gridshells is a viable form of construction, and that enhanced durability characteristics of BFRP could lead to their adoption for gridshells, given that the creep characteristics of basalt fibres presented here are comparable to those of glass fibres. An altogether different form of timber construction is that of joist-and-floorboard. In the UK, there are thousands of historic buildings which use this floor construction, and a sizeable proportion of this building stock now requires upgrade, strengthening and/or stiffening to allow these buildings to be fit for purpose into the future. This paper goes on to consider the possible use of Carbon FRP (CFRP) to strengthen and stiffen such timber floors. It is shown that such strengthening and stiffening is entirely feasible, offering the potential for greatly enhanced stiffness, in particular. Further, it is shown that mechanical shear connection between CFRP and timber is best conducted using perpendicular-positioned screws, rather than raked screws.

Design and construction of the Downland Gridshell

A gridshell is a structure that gains its strength and stiffness through its double curvature configuration. Its advantages are a minimum use of materials, structural efficiency and the creation of a large volume, as well as the potential for quick and cost-effective construction. However, few gridshells have been built due to a lack of knowledge and data. The process of creating the Downland Gridshell, as a specialist museum workshop completed in the spring of 2002, is a case study of successful collaboration and innovation in architecture, engineering and construction led by a multidisciplinary team of practitioners. This gridshell structure was composed of a double layer of mats comprising four layers of thin timber laths. These were harnessed together as a flat mat and then formed into a three-dimensional structure by a carefully orchestrated lowering of each supporting scaffolding prop, thereby harnessing gravity to pull the mat into shape. Many innovations are described in detail: team working, risk sharing, multidisciplinary design, structural modelling, the creation of new structural components, cladding, and construction processes including the sequence and techniques of gridshell forming. Advances made in this project have added to the knowledge of gridshell behaviour, construction and cost, thereby making the design and construction of future timber gridshells a more viable option.

Downland gridshell—an innovation in timber design

Innovations in timber construction are relatively rare these days. However, a modest utility building at an open-air museum in Sussex has attracted worldwide attention for the novel features of its double-layer timber gridshell roof. Apart from being the first such structure in Britain, it was the first built with ‘optimised’ green oak, the first designed in accordance with the new timber Eurocode and the first to use a new patented node joint system. It sets a new benchmark for lightweight, sustainable, cost-effective construction.