In timber-concrete composite systems, timber and concrete are inherently brittle materials that behave linearly elastic in both tension and bending. However, the shear connection between the members can exhibit significant ductility. It is therefore possible to develop timber-concrete composite systems with ductile connection that behave in a ductile fashion. This study illustrates the use of an elastic-perfectly plastic analytical approach to this problem. In addition, the study proposes an incremental method for predicting the nonlinear load-deflection response of the composite system. The accuracy of the analytical model is confirmed with a computer model, and numerical solutions of the analytical model are compared to experimental results from the bending tests conducted by previous researchers. Reasonable agreement is found from the comparisons, which validates the capacity of the analytical model in predicting the structural behaviour of the timber-concrete composite systems in both elastic and post-elastic stages.
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.
Australian Life Cycle Assessment Society conference
The use of timber construction products and their environmental impacts is growing in Europe. This paper examines the LCA approach adopted in the European CEN/TC350 standards, which are expected to improve the comparability and availability of Environmental Product Declarations (EPDs). The embodied energy and carbon (EE and EC) of timber products is discussed quantitatively, with a case study of the Forte building illustrating the significance of End-of-Life (EoL) impacts. The relative importance of timber in the context of all construction materials is analysed using a new LCA tool, Butterfly. The tool calculates EE and EC at each life cycle stage, and results show that timber products are likely to account for the bulk of the EoL impacts for a typical UK domestic building.
Some innovative and structurally efficient uses of massive wood panels, such as cross-laminated timber (CLT), will result in hollow structural sections. Light-weight wood construction as well as heavy timber assemblies using dropped ceilings or raised fl...
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.
With the aim of evaluating the bond behaviour between glulam and carbon fibre reinforced
polymer laminates strips, an experimental program using pull-out tests was carried, when the near-surface strengthening technique is applied. Two main variables were studied: the bond length and the type of pull-out test configuration. The instrumentation included the loaded and free-end slips, as well as the pullout force. Based on the obtained experimental results, and applying an analytical-numerical strategy, the local bond stress-slip relationship was determined. In this work the tests are described, the obtained results are presented and analysed, and the applicability of an inverse analysis to obtain the local bond law is demonstrated.