International Conference on New Horizons in Green Civil Engineering
Wood structures such as the Wood Innovation and Design Center in Prince George and the UBC Tallwood House, an 18 storey, 53-meter-tall mass timber hybrid building are examples of new and innovative wood structures that encompass new construction techniques, unique materials and novel building practices. Empirical data on the condition of critical components and access to the real-time status of the structure during construction gives Architects, Engineers and Contractors critical information to make informed decisions to either validate or improve the construction plan. Data recorded during the life of the building helps validate the design decisions and proves the viability and feasibility of the design. Methods and practices used to monitor both the moisture performance of prefabricated cross laminate timber (CLT) as well as the vertical movement sensing of the building during and after construction are explored in this paper. Moisture content of the CLT panels has been recorded from manufacturing and prefabrication to storage, through transport and during installation and will continue throughout the service life of the building.
The calculated and expected displacement of the wood columns is scheduled to take several years as the structure settles, however a first-year analysis and extrapolation of the data was conducted. Monitoring during transport, storage, and construction proved that CLT panels were resilient to moisture issues while in the manufacturers storage, but prone to direct exposure to moisture-related problems regardless of the precautions taken on site. Despite construction during typical Pacific Northwest rain, informed decisions were made to ensure the panel moisture content could decrease to acceptable ranges before continuing to secondary construction phases. The moisture trends observed in the building were proportional to the control samples as both were subjected to similar environmental conditions.
Cross-Laminated Timber (CLT) structures exhibit satisfactory performance under seismic conditions. This ispossible because of the high strength-to-weight ratio and in-plane stiffness of the CLT panels, and the capacity ofconnections to resist the loads with ductile deformations and limited impairment of strength. This study sum-marises a part of the activities conducted by the Working Group 2 of COST Action FP1402, by presenting an in-depth review of the research works that have analysed the seismic behaviour of CLT structural systems. Thefirstpart of the paper discusses the outcomes of the testing programmes carried out in the lastfifteen years anddescribes the modelling strategies recommended in the literature. The second part of the paper introduces theq-behaviour factor of CLT structures and provides capacity-based principles for their seismic design.
This paper discusses the state-of-the-art of displacement-based seismic design (DBD) methods and their applications to timber buildings. First, an in-depth review of the DBD methods is presented, focusing in particular on the direct, modal and N2 methods. Then, paper presents DBD application on a wide range of construction systems, including both traditional light-frame structures as well as the emerging sector of tall and hybrid timber buildings. Finally, potentials of using these DBD methods for seismic design as well as possible implications of including DBD within the next generation of building codes are discussed.
A novel timber composite is presented, consisting of glued laminated timber (GLT) from softwoods and intercalated cross-layered plates of laminated veneer lumber (LVL) made of hardwood species, specifically beech. The structure is especially suited for beams with multiple, large rectangular holes, where the LVL acts as a highly efficient internal reinforcement and contributes to a damage-tolerant ultimate load behavior. The load capacity of the composite beam is not induced by the stress concentrations at the corners of the hole, which, in contrast to generic GLT, lead to a sudden propagation of cracks and brittle failure. It is shown that the structure, including the holes, can be designed analytically in a transparent manner by using beam theory, a parallel system approach, and modifications from FEM analysis for the verification of tensile forces at the hole periphery. The composite, firstly used in a recent multi-story building in Australia, significantly improves the competitiveness of timber in building works, which have been limited to steel and reinforced concrete structures.
The study reports on block shear investigations with bondlines of face-glued laminations and matched solid wood specimens from hardwood glulam (GLT) beams produced industrially from eight technically and stand volume-wise important species. The European hardwoods comprised oak, beech, sweet chestnut and ash and the tropical species were teak, keruing, melangangai and light red meranti. The adhesives were phenol-resorcinol and melamine-urea. When combining all species in one sample, a rather strong linear relationship of bond and wood shear strength was observed. The ratio of bond vs. wood shear strength was for all species on the mean value level = 0.9, and likewise (with one exception) for the respective strengths’ 5%-quantiles. Consistent with literature, the test results showed no significant correlations between bond shear strength and density, wood shear strength and wood failure percentage of individual species, respectively. The investigations render the methodological basics of some international standards on bond quality verification as being inappropriate. New, empirically validated hardwood GLT bond requirements are proposed for discussion and implementation at the CEN and ISO levels. The strength ratio specifications reflect respective ANSI provisions, yet the reference quantity wood shear strength is now determined in an unbiased manner from matched GLT specimens. The wood failure verification proposal is based on the 10%-quantile and mean level for initial type testing and factory production control. The requirements further account for the pronounced difference observed in scatter of wood failure between European and tropical species.
In this study, flexuralbehaviors of glue laminated timber beams manufactured from Pinussylvestristree were investigated by comparing the results with those of massive timber beams. The main variables considered in the study were number of laminations, types of adhesive materials and reinforcement nets used in the lamination surfaces. In scope of the experimental study, glue laminated beams with 5 and 3 lamination layers were manufactured with 90 x 90 mm beam sections. In the lamination process epoxy and polyurethane glue were used. Morever, in order to improve the bond strength at the lamination surface, aluminium, fiberglass and steel wire nets were used at the lamination surfaces. Load–displacement responses, ultimate capacities, ductility ratios, initial stiffness, energy dissipation capacities and failure mechanisms of glue laminated beams were compared with those of massive beams. It was observed that the general bending responses of glue laminated beams were better than those of massive beams. In addition to that the use of reinforcement nets at the lamination surfaces increased the ultimate load capacities of the tested beams. The highest ultimate load capacities were oberved from the tests of glue laminated beams manufactured using five laminated layers and retrofitted with polyurethane glue using steel wire reinforcement nets, in the direction normal to the lamination surface. Finally, the finite element simulations of some test specimens were performed to observe the accuracy of finite element technology in the estimation of ultimate capacities of glue laminated timber beams.