Openings are usually required to allow services like plumbing, sewage pipes and electrical
wiring to run through beams. This prevents an extra depth of the floor/ceiling, while preserving architectural considerations. The introduction of large opening causes additional tension perpendicular to grain in timber beams. The low tensile strength perpendicular to grain of wood allows crack formation. Crack propagation around the hole considerably decreases the load-carrying capacity of the beam. However, in most cases, crack formation and propagation around
the hole can be prevented by the use of an appropriate reinforcement. Screw, glued-in rods, and plywood are alternative options for the reinforcement. Design of the reinforcement requires that the working mechanism of the reinforcement is fully understood and properly addressed. In addition, reinforcement should be designed for actions produced in the section of the beam weakened by the hole. The current paper uses a simple truss model around the opening to calculate the tensile force in the reinforcement. Two simple formulations for design of the reinforcement are derived and compared with numerical and experimental results, showing an overall good correspondence. The proposed truss model can be considered for incorporation in future codes of practice.
A research study was undertaken to investigate the mechanical performance of glulam beams reinforced by CFRP or bamboo. Local reinforcement is proposed in order to improve the flexural strength of glulam beams. The glulam beam is strengthened in tension...
At the Institute of Structural Engineering at the ETH Zurich numerous of investigations are
conducted to analyse the load bearing capacity of glued laminated timber beams. The investigations are part of the research project ’Influence of varying material properties on the load bearing capacity of glued laminated timber (glulam)’.
The investigations are taking place on 24 glulam beams with well-known material properties.
The glulam beams are fabricated out of 400 timber boards. From those boards the material
properties are investigated non-destructively within a former research project. During the glulam
fabrication it is particularly focused to keep the information of the timber boards; i.e. after the
glulam fabrication the position of each particular timber board within the glulam beam and
thus the position of each particular knot is still known.
The glulam beams are investigated during a 4-point bending test. On the glulam members
the load bearing capacity, the bending stiffness and the density is measured. Furthermore
local strains within the glulam beams are investigated using an optical coordinate-measurement
device. Following the test the failure is investigated in detail. Hereby the type of failure (knot
cluster, finger joint, clear wood) and the amount of failure (number of damaged lamellas) is
documented. Afterwards the failed glulam beams are loaded again to analyse the remaining
bending strength and the corresponding remaining bending stiffness.
The major aim of the experimental analysis is the investigation of the load bearing capacity
of glulam beams with well-known local material properties. The gained results can be used for
an investigation of the influence of local weak zones, such as knot clusters or finger joints, on the
load bearing capacity of glulam. In addition a data basis is produced to develop a new model
(or to evaluate existing models) for the estimation of the load bearing capacity of glulam.
This study provides a comparative life cycle assessment (LCA) of a 4060 m2, 4-storey cross laminated timber (CLT) apartment building located in Quebec City, Canada and an equivalently designed building consisting of reinforced concrete slabs and columns with light gauge steel studded walls (CSSW). The emergence of CLT as a structural material that can be used in mid-rise building structures combined with limited work investigating the environmental performance of CLT in building applications provides the motivation for this comparative study.
International Design Engineering Technical Conferences and Computers and Information in Engineering Conference
August 4–7, 2013, Portland, Oregon, USA
As sustainable building design practices become more prevalent in today’s construction market, designers are looking to alternative materials for novel design strategies. This paper presents a case study comparing the sustainability performance of cross laminated timber (CLT) and reinforced concrete. A comparative sustainability assessment of cross laminated timber and concrete, considering economic, environmental, and social aspects was performed. Environmental impact is measured in terms of CO2 equivalent, economic impact is measured with total sector cost (including sector interdependencies), and qualitative metrics were considered for social impact. In order to conduct an accurate performance comparison, a functional unit of building facade volume was chosen for each product. For this paper, several end-of-life strategies were modeled for CLT and concrete facades. To understand environmental, economic, and social impact, three different scenarios were analyzed to compare performance of both CLT and concrete, including cradle to gate product manufacturing, manufacturing with landfill end-of-life, and manufacturing with recycling end-of-life. Environmental LCA was modeled using GaBi 5.0 Education Edition, which includes its own database for elements including materials, processes, and transportation. To compare the economic impact, Carnegie Mellon’s EIO-LCA online tool is used. Finally, social life cycle impact was considered by identifying process attributes of both products that affect the social domain. Based on this analysis, the use of CLT has a significantly lower environmental impact than concrete, however there are additional costs.
The glulam is determined by, and therefore a representation of, a new kind of ecological structural materials. The aim of this study was to summarize the mechanical performance especially the flexural behavior of various kinds of glulam and the physical...
This paper deals with the possibilities of using coupled timber-concrete structures by means a glued coupling bar. The described process of static reinforcement is particularly suitable for reconstruction of historic timber ceilings and places where it is necessary to prevent damage to non-supporting structures...