Wood is a hygroscopic material that primarily adapts its moisture content to the surrounding relative humidity. The climate in a structure or building depends on the building type and the region the structure is located in. In this study, the effect of region on the moisture content of wood was investigated. Measurements taken in 12 ventilated timber structures were compared to the theoretical equilibrium moisture content calculated from the relative humidity and temperature in 107 meteorological stations across Switzerland. The monitored load-bearing elements were made of softwood and protected from the direct impact of weather. The climatic conditions around the Alps, a mountain range that runs from France to Austria and crosses Switzerland, can be divided into the following three different regions: (1) south of the Alps, where the climate is affected mainly by the Mediterranean sea; (2) north of the Alps, where the climate is affected by the Atlantic Ocean; and (3) the inner Alps, where the climate is considered to be relatively dry. The climatic conditions of the three separate regions were reflected in the measurements made in the monitored timber structures. Differences between the regions were quantified. The moisture content and relative humidity, similarly to temperature, depended on altitude (above sea level).
Cross laminated timber (CLT) is a new engineered wood product that has experienced rapid growth and market acceptance for residential and non-residential construction in western and central Europe. Potential exists for rapid market adoption in North America if manufacturing capacities are developed. Dissemination of information on CLT North America markets, manufacturing capabilities, and product standards are the next key steps for facilitating investment in CLT manufacturing capacities in North America. This paper compares standards for CLT between Europe and North America.
Research has repeatedly pointed out the suitability of adhesive bonding to substitute to “traditional” joining techniques for numerous materials and loads, including timber to glass. Practitioners, however, are still reluctant to implement them into their designs. Adhesion as a method of joining, particularly in the context of hybrid structures, presupposes knowledge of all involved materials, including codes and procedures; most practitioners however tend to be focused on just a subset of materials. While such specialization is not unusual, it makes it challenging to implement novelty (i.e. new materials or techniques). Additionally, when it comes to adhesion where most of the knowledge has been generated by chemists, the lines become even more blurred. Taking the example of a pedestrian timber-glass bridge, this research shows how design and dimensioning of complex bonded hybrid structures can be performed in accordance with “traditional” engineering practice. The paper guides through every step, from the first concepts to the final design, including the manufacturing, of a relatively complex structure, in which timber and glass act together as equivalent members. The compliance of this process with engineering models is emphasized, and the embedment into existing codes and standards is sought after to ensure acceptancy by practitioners.
Cross-laminated timber (CLT) is a prefabricated solid engineered wood product made of at least three orthogonally bonded layers of solid-sawn lumber or structural composite lumber that are laminated by gluing of longitudinal and transverse layers with structural adhesives to form a solid rectangular-shaped, straight, and plane timber intended for roof, floor, or wall applications. While this engineered wood product has been used in Europe for over 15 years, the production of CLT and design of CLT structural systems have just begun in North America. For the acceptance of new construction materials or systems in North America, such as CLT, a consensus-based product standard is essential to the designers and regulatory bodies. This paper describes and documents the background information and some key issues that were considered during the development of the ANSI/APA PRG 320 Standard for Performance-Rated Cross Laminated Timber. This standard was developed based on the consensus standard development process of APA-The Engineered Wood Association as a standards developer accredited by the American National Standards lnstitute (ANSI). The CLT stress classes incorporated in this product standard are also discussed. The ANSI/APA PRG 320 standard has been approved by the Structural Committee of the lnternational Code Council (lCC) for the 20'15 lnternational Building Code (lBC).
Cross Laminated Timber (CLT) technology has been growing in the EU and Canada since the early 1990's and utilizes the mechanical properties of structural grade lumber to create a strong panel product for use in floor, ceiling and wall systems. The hypothesis of this project was that CLT panels made from non-structural lumber from lightweight species could also meet the performance criteria of the CLT product Standard. The objective of this project was to compare bond integrity in an optimized hybrid poplar CLT panel with standard CLT performance criteria Standard bond integrity tests were performed on CLT samples constructed using two adhesive types and three clamping pressure levels in order to find combinations that may pass the CLT product standard requirements. A lightweight structural CLT product made from hybrid poplar could be used as a model for other low density CLT products made from other less utilized resources.
The overall aim of this report is to assess the earthquake resistance on the basis of calculating the seismic design of a residentual building errected in Solid Timber Construction. Thus, a detailed analysis of the sample building focusing on the instantaneous seismic design situation and using the currently valid ONORM B 1998-1:2006, will be conducted. In the context of assessing the earthqake resistance of a building, it is also hughly interesting to analyse the control of the regular criteria in plane and evaluation due to their significant importance to the calculation. The final determination of the primary seismic components, in this example the focus is on the bracing panels, is also made by using the Austria currently valid Eurocodes for Timber Design in combination with the guidelines taken from the previously mentioned European Standard for Earthquakes.
The increasing interest in cross-laminated timber (CLT) construction has resulted in multiple international research projects and publications covering the manufacturing and performance of CLT. Multiple regions and countries have adopted provisions for CLT into their engineering design standards and building regulations. Designing and building CLT structures, also in earthquake-prone regions is no longer a domain for early adopters, but is becoming a part of regular timber engineering practice. The increasing interest in CLT construction has resulted in multiple regions and countries adopting provisions for CLT into their engineering design standards. However, given the economic and legal differences between each region, some fundamental issues are treated differently, particularly with respect to seismic design. This article reflects the state-of-the-art on seismic design of CLT buildings including both, the global perspective and regional differences comparing the seismic design practice in Europe, Canada, the United States, New Zealand, Japan, China, and Chile.
This comprehensive book provides in-depth knowledge and understanding of design rules according to Eurocode 5. It is based on the first edition of the STEP (Structural Timber Education Programme) series, which was prepared in 1995 by about 50 authors from 14 European countries. The present work updates and extends the STEP compilation and is aimed at students, structural engineers and other timber structure professionals.
In the National Building Code of Canada (NBCC) and American Society of Civil Engineering (ASCE) standard (ASCE7) , different criteria for a two-step analysis procedure to design podium buildings are provided. However, nonlinear time-history dynamic analysis results show that such designed buildings may not meet the intended seismic performance. A new criterion has been developed at FPInnovations (Chen&Ni,2017&2020). Analysis results show that when the normalized stiffness ratio is at least 10 times greater than the normalized mass ratio, the buildings designed by the two-step analysis procedure can meet the performancere quirement. This InfoNote briefly reviews the two-step analysis procedure, demonstrates the shortcoming of the NBCC and ASCE criteria, and introduces the developed criterion.