Eucagrid 2016-2018

Title (acronym): Analysis of the stress relaxation in curved members and new joints solutions for timber Gridshells made out of Eucalyputs globulus (EUCAGRID)

Reference: BIA2015-64491-P

Funding: National Program for the Promotion of Scientific and Technical Research of Excellence, National Subprogram for Knowledge Generation, Spanish Ministry of Economy and Competitiveness.

Duration: 3 years (01/01/2016 – 31/12/2018).

Budget: 86.515,00 €

Financed amount: 71.500,00 €

Principal Research: Dr. Manuel Guaita Fernández

Research Team

Abstract

The sustainable and environmentally friendly construction is no longer a value-added to become a requirement of our society. Timber construction is experiencing a boost in Europe due to the environmental advantages of over other materials.

The emergence of new products and wood-based systems along with the evolution of structural analysis tools is causing hitherto unthinkable developments, such as multi-storey buildings and shell structures.

Shell structures are a very efficient structural type which acquires strength and stiffness because of its shape. The main drawback is that this geometry, usually irregular, often implies the construction of singular elements with the consequent impact on the implementation costs.

The gridshell technique allows to build long span timber shells structures with double curvature from standard elements. This technique is based on the on site bending of flat grids made of identical elements of good quality solid wood, great length and small section, constituting a system with high capacity of industrialization and standardization.

However, despite the enormous potential of the gridshell technique, just some unique works have been built following this structural type due to important scientific and technical difficulties that hinder its use. In particular, the lack of studies on the stress relaxation that occurs in timber elements with large curvatures, the necessary development of specific joint systems, the lack of adequate commercial wood products, and the lack of research on numerical models experimentally contrasted are several aspects that make difficult the implementation and development of this interesting structural system.

This project aims to create knowledge about these issues in order to achieve the implementation of gridshells made out of national wood species of high performance. In particular, the proposed research aims to deepen the understanding of the mechanical and structural properties of Eucalyptus globulus for its innovative implementation in such structures. For this purpose, the stress relaxation of the curved elements and two novel joint solutions will be numerically and experimentally analyzed. In addition, two full scale prototypes of gridshells will be tested, which will be useful for validating a new numerical model including the elastoplastic behavior of the joints, the bending stress and its relaxation, and the multilayer characteristic geometry of gridshells.

The research will be complemented by the innovative development of a lath finger-joint for Eucalyptus globulus necessary to get elements of great length.

Finally, as part of the dissemination strategy, a practical application of the developed research will be done by building a gridshell of ecualyptus for a parking cover. This action will extend the investigation beyond the project time limits by the monitoring of its long-term evolution and behavior.