Design of Structural Timber: To Eurocode 5
Abstract
This New Casebook contains ten essays written about Blake's poetry since 1970 selected to show the diversity of Blake criticism during the last twenty years and the ways in which contemporary critical theories open up new readings of his work. Essays representative of Marxist, psychoanalytic, deconstructionist, feminist and new historicist criticism are included. David Punter's Introduction places these in the context of recent developments in critical theory and shows how today's student can best engage with Blake's complex and rewarding work.
... The timber floor is a one-way system and is simply supported on two beams. The equivalent viscous damping ratio of the timber floor (denoted by ) is 2%, as is commonly practised [5,6]. The boundary condition of the floor system on OPENSEES is that it is simply supported, i.e. one support is constrained longitudinally and horizontally and another is constrained longitudinally. ...
... The human walking signals depicted in Figure 2 were exerted on the timber floor system by conducting simulations on OPENSEES. The testing sequences are tabulated in (2) T ( o C) (3) fT (Hz) (4) mT (kg) (5) cT (%) (6) (1) total mass of the timber floor system (2) natural frequency of the main structure (3) working temperature of the SMA beam (4) natural frequency of one SMA cantilever beam (5) mass attached to the SMA cantilever beam (6) equivalent viscous damping ratio of the SMA cantilever beam ...
... The human walking signals depicted in Figure 2 were exerted on the timber floor system by conducting simulations on OPENSEES. The testing sequences are tabulated in (2) T ( o C) (3) fT (Hz) (4) mT (kg) (5) cT (%) (6) (1) total mass of the timber floor system (2) natural frequency of the main structure (3) working temperature of the SMA beam (4) natural frequency of one SMA cantilever beam (5) mass attached to the SMA cantilever beam (6) equivalent viscous damping ratio of the SMA cantilever beam ...
... where b c,ef is the effective flange width in compression and b w is the joist width as illustrated in Fig. 2. The value of the effective flange width that can be assumed to interact in the T-section must not exceed certain values due to effects of shear lag and plate buckling; for OSB/3, where the main chip direction is parallel to the joist, it can be obtained as Ref. 16 : ...
... From an instructive point of view, in order that the gluing or bond between floorboards and joists shall be effective, the timber joists must be planed (or surfaced), cleaned before applying glue, and adhesive pressure is obtained through screws (with at least a length of 50 mm) distributed at 300 mm (at floorboards' edge, the distance is halved) 14,17 . It is worthwhile to mention here that the planar or rolling shear at the flange glue lines needs to be checked to satisfy the requirements for the ultimate limit state 16 . ...
This study is aimed at investigating those parameters related to timber flooring that can affect the acceptability of vibration behaviour of a timber floor in a residential building in view of the criteria stated in Eurocode EC5. The timber floor investigated is made of OSB/3 floorboards and timber joists. The parameters that are investigated in this study are thickness of flooring, floor joist span, joist spacing and connection of floorboards to the joists. In this context, two cases are considered. First: the flooring is nailed or screwed to the joists and no composite action or interaction is obtained between joists and floorboards. Second: the flooring is glued sufficiently to the joists and full interaction is obtained. The result suggests that glued floorboards perform much better with respect to natural frequency, static deflection and peak floor velocity than nailed or screwed floorboards. In almost all cases of glued floorboards, the result complies fully with the Eurocode 5 design vibration requirements. However, as floor lengths increase, the static deflection will increase beyond the allowable limit, especially for relatively thin floor panels and relatively widely spread joists. For both cases, increasing floorboards thickness and decreasing the joist span by adding more beams can yield even better results to satisfy the requirement of vibration comfort.
... Moreover, other factors affect shear strength, such as moisture content. According to Table 2, the 10-year-old Acacia hybrid sample exhibited the lowest moisture content, where moisture content is reported to significantly influence timber's mechanical strength [28,31,33,34]. Madsen [35], in his study, found that moisture content significantly affects shear strength. ...
... Thus, it is agreed that the density of wood should not be the definite measurement of its strength [37]. McKenzie [33] reported that heartwood tissue's presence provides mechanical rigidity and strength to timber. From this study, the age group of 10 years old possessed the highest strength properties value as compared to other age groups. ...
An effort was carried out to fully utilise fast-growing Acacia hybrid usage in the timber engineering field; however, the research data are still lacking. This paper aims to evaluate the physical and mechanical properties performance between untreated (control) and treated with 10% copper chrome arsenic of Acacia hybrid collected from Daikin Plantation Sdn. Bhd. Bintulu, Sarawak at air-dry condition at different age groups using the small clear method. Mechanical properties test refers to shear parallel to grain (tangential and radial directions), cleavage (tangential and radial directions), and tension parallel to grain test. Meanwhile, the physical properties test refers to moisture content (MC) and density test. After treatment, mechanical properties increase with an average of 13.67%; meanwhile, moisture content decreased with an average of 0.58% or 0.09% MC, and density slightly increased with an average of 0.44% or 0.002 g/cm³. Results indicate that 10-year-old Acacia hybrid exhibits the highest strength values in shear parallel to the grain, tension parallel to the grain, and cleavage, followed by 13-year-old and 7-year-old. Treated samples in the tangential direction performed better with consistent mean results than that of the untreated samples, while radial direction gave a high average strength increment when treated.
... Sport stadium Majuro is an example of arch-type timber roof, where the main structures in the transversal direction are three hinged arches with span equal to 60 m ( Fig.1.). Two-hinged static schemes used for the structures with the short-spans in the case of glued cross-sections or for the long-span lattice arches [5] - [8]. Arch-type timber roof of Hakona hall is an example of the roof, where the main load-carrying structures in the transversal direction are lattice arches with the span equal to 86 m ( Fig.1.). ...
... Equation for the case, when specific load-carrying capacity of the arches was considered as a parameter of optimization, has the similar form. Rational from the point of view of materials consumption height and bay of the arches so as bays of the bracing members providing lateral strengthening of the top and bottom parts of the arches cross-sections were determined for the arch-type timber roof by the system of equations (5): (5) Where designations the same as for equation (4). ...
Possibility to increase load-carrying capacity of arch-type timber roof of multifunctional public building with the span equal to 60 m was analysed. Three-hinged segment arches with the rectangular glued cross-sections are considered as the main load-carrying structures in the transversal direction. Freely supported purlins with the massive rectangular cross-sections are considered as the main load-carrying structures in the longitudinal direction. The dependences between height of the arches, it bays and distances between the bracing members strengthening top and bottom zone of the arches cross-sections so as relative materials consumption and specific load-carrying capacity of the arches were obtained as the second power polynomial equations. Height of the arches and it bay changes within the limits from 10 to 30 and from 2 to 9 m, correspondingly. The distances between the bracing members strengthening top and bottom zone of the arches changes within the limits from 2 till 10 and from 4 till 16 m, correspondingly. The arch-type timber roof was considered under the action of the load combination which include structural dead weight, drifted and undrifted snow loads and wind loads. The relative materials consumption of the arches was determined as a relation between the dead weight of the arch to it span and changes within the limits from 24 till 114 kg/m. Glued and solid timber with strength classes GL24h and C24 are considered as materials of arches and purlins, correspondingly. The specific load-carrying capacity of the arches was determined as a relation between load –carrying capacity of the arche and volume of structural materials. Specific load-carrying capacity of the arches changes within the limits from 0.23 till 0.83 kN/m/t in the case, if purlins are taken into account. It was shown, that the rational from the point of view of materials consumption and specific load-carrying capacity height of the arche, it bays so as the distances between the bracing members strengthening top and bottom zone of the arches are equal to 15, 7.5, 5 and 15 m, correspondingly. Corresponding values of relative materials consumption and specific load-carrying capacity are equal to 24 and 0.23 kN/m/t. The depth and width of the arche cross-section were equal to 1617 and 318 mm, correspondingly. It was shown, that strengthening of the arches cross-section by the steel bars of strength class B500 and carbon fibre reinforced plastic tape Sika Crbo Dur S512 enables to increase load-carrying capacity of the arche by 10.20 and 9.48%, correspondingly. But common use of the steel bars together with the carbon fibre reinforced plastic tapes enables to increase load-carrying capacity of the arche by 18.89%.
... Testing of defect free specimens is a good method to compare the effects of different treatment processes and/or different treatment conditions. However, results of tests cannot be used for the calculation of constructive elements, at least not without the use of several safety factors (Brown et al. 1952, Kollmann 1968, McKenzie 2000, Natterer et al. 2004). The occurrence of natural defects in wood, such as knots, resin pockets, reaction wood and a deviating slope of grain, decreases the strength properties of timber. ...
... In most studies defect free specimens are used to determine the effect of heat treatment on the mechanical properties. Defect free specimens can be used to compare the effects of different treatment processes and/or different treatment conditions but not for the calculation of constructive elements, at least not without the use of several safety factors (Brown et al. 1952, Kollmann 1968, McKenzie 2000, Natterer et al. 2004). The occurrence of natural defects in wood, such as knots, resin pockets, reaction wood and a deviating slope of grain, decreases the strength properties of wood. ...
Thermal modification or heat treatment is an effective method to improve the dimensional stability and biological durability of wood. An undesired side effect is the reduction of mechanical properties of wood, mainly due to the high temperatures involved (150-280°C). In this thesis the effects of heat treatment on wood properties are discussed in relation to anatomical and molecular changes found in wood after heat treatment. The results are based on investigations of a full-scale industrial heat treatment method under relative mild conditions (< 200°C) including a moist and dry treatment stage. Several changes and/or modifications of the main components of wood (cellulose, hemicelluloses and lignin) appear to be involved in the effects of heat treatment on important wood properties like dimensional stability, strength/stiffness and biological durability. Although the effect of heat treatment on the anatomical structure of wood is limited, changes have been found affecting the properties of wood. This thesis provides a better understanding of thermal modification, which probably contributes to a more controlled use of heat-treated wood in service conditions.
... Testing of defect free specimens is a good method to compare the effects of different treatment processes and/or different treatment conditions. However, results of tests cannot be used for the calculation of constructive elements, at least not without the use of several safety factors (Brown et al. 1952, Kollmann 1968, McKenzie 2000, Natterer et al. 2004). The occurrence of natural defects in wood, such as knots, resin pockets, reaction wood and a deviating slope of grain, decreases the strength properties of timber. ...
... In most studies defect free specimens are used to determine the effect of heat treatment on the mechanical properties. Defect free specimens can be used to compare the effects of different treatment processes and/or different treatment conditions but not for the calculation of constructive elements, at least not without the use of several safety factors (Brown et al. 1952, Kollmann 1968, McKenzie 2000, Natterer et al. 2004. ...
... However, ensuring that the joint is completely tight is not feasible, since wood is a natural material that may shrink or swell, and tolerance gaps are unavoidable for constructability. Gaps between members vary in size depending on the type of connection and the extent of any shrinkage or swelling of the wood [5,6]. The best feasible gap width for connectors that are recessed in holes carved into the wood is 1 mm, but even with this design value, the in-use gap width could foreseeably increase to 6 mm-thus potentially exposing the metal connectors to high temperature gases. ...
Tolerance gaps in wood connections are unavoidable, for reasons of constructability and the effects of natural shrinkage in timber elements with changing moisture content. During a fire, these gaps may lead to a substantial heat transfer to the metal connectors that are considered heat protected being embedded by the wooden components of the connection. Aluminium connectors are popular due to their ease of production and assembly, but they are particularly vulnerable to elevated temperatures. This study investigates the effects of tolerance gaps on the fire performance of aluminium connectors in beam-to-column/wall shear connections. Reduced-scale experiments were designed to study the temperature evolution of aluminium connectors during standard fire exposure for 1 mm and 6 mm tolerance gaps, as well the mitigation effects of additional intumescent fire protection in a 6 mm tolerance gap connection. For the 6 mm gap, the temperature of the connector increased much faster, reaching 286 ± 36°C after 80 min, at which time the connector with a 1 mm gap had only reached 97 ± 1°C. The addition of intumescent protection in a 6 mm gap case led to lower temperatures in the connection, in comparison to an equivalent tolerance gap without protection. Subsequently, two additional loaded fire tests were performed, for 6 mm and 22 mm tolerance gaps without fire protection, to investigate the critical failure mode of the connectors. In these cases, the failure occurred in the connectors at 87 min and 32 min, respectively, when their average temperatures reached approximately 315°C. This study demonstrates the critical influence of gap size on the fire performance of aluminium-wood joints.
... However, ensuring that the joint is completely tight is not feasible, since wood is a natural material that may shrink or swell, and tolerance gaps are unavoidable for constructability. Gaps between members vary in size depending on the type of connection and the extent of any shrinkage or swelling of the wood [3,4]. The best feasible gap width for connectors that are recessed in holes carved into the wood is 1 mm, but even with this design value, the in-use gap width could foreseeably increase to 6 mmthus potentially exposing the metal connectors to high temperature gases. ...
Tolerance gaps or slips in wood connections are unavoidable, for reasons of constructability and the effects of natural shrinkage in timber elements with changing moisture content. During a fire, these gaps may lead to increased heat transfer through the connection. Aluminium connectors are becoming more popular due to their high malleability and availability, but they are particularly vulnerable to elevated temperatures. Thus, the objective of this study is to investigate the effect of tolerance gaps on the fire performance of aluminium connectors in beam-to-column/wall shear connections. An experimental campaign was designed to study the temperature evolution of the aluminium connectors during standard fire exposure for 1 mm and 6 mm tolerance gaps, as well the mitigation effects of additional intumescent fire protection in a 6 mm tolerance gap connection. The results showed a clear and consistent impact of the connection gap size on the temperature evolution of the aluminium connectors. For the larger 6 mm gap, the temperature of the connector increased much faster, reaching 286 ± 36 °C after 80 minutes, at which time the connector with a 1 mm gap had only reached 97 ± 1 °C. The addition of intumescent protection in a 6 mm gap case led to lower temperatures in the connection after 40 minutes of fire exposure, in comparison to an equivalent tolerance gap without fire protection. This study shows that tolerance gaps can lead to a significant reduction in the capacity of aluminium connectors, but this may be mitigated with additional fire protection.
... For the technical quality assessment of Co-Design processes and products, the online questionnaire showed that most technical quality requirements for timber and concrete construction are derived from national and international norms and standards. In contrast, there are currently no norms and standards for the use of fibre-composites for planning and manufacture Quality characteristics, which are relevant for the assessment are extracted from the received standards [37][38][39][40][41][42][43][44]. In order to clarify the understanding of the technical quality characteristics, exemplary quality characteristics, parameters, and criteria are shown in Table 1. ...
Facing rising building demands due to a fast-growing world population and significant environmental challenges at the same time, the building sector urgently requires innovation. The Cluster of Excellence Integrative Computational Design and Construction for Architecture at the University of Stuttgart tackles these challenges through a Co-Design approach for integrating computational design and engineering and robotic construction. Within this research framework, a Holistic Quality Model is developed to ensure the technical, environmental, and social quality of Co-Design processes and products. Up to now, quality models that consider and integrate all these three aspects throughout the life cycle of buildings are still missing. The article outlines the concept of holistic quality assessment based on a Holistic Quality Model for sustainable construction. A key mechanism for sustainable quality assessment in the Holistic Quality Model is the definition of control and decision points in the construction process where critical decisions are made that will affect the quality of the building throughout its entire life-cycle. Firstly, subject-specific quality concepts are defined and their interrelations are conceptualized. Subsequently, these interrelations and their effects on the overall Co-Design construction processes and products are explained using the example of the semi-robotic production of concrete slabs. Examples for control and decision points are given as well. The outline presented here serves as a basis for further advancing and concretizing the Holistic Quality Model and its applications in Co-Design for a functioning, liveable, and sustainable high-quality construction and building culture.
... Jarnerö et al. [20] measured the dynamic characteristics of a prefabricated timber floor with various boundary conditions at different construction stages. Two textbooks were also written on structural timber design to Eurocode 5 [21,22]. Recently, considerable attention has been paid to the dynamic responses of timber floors constructed with LVL (laminated veneer lumber) beams, glulam beams and CLT (cross-laminated timber) panels, and TCC (timberconcrete composite) floors. ...
Based on classic vibrational bending theory on beams, this paper provides comprehensive analytical formulae for dynamic characteristics of two equal span continuous timber flooring systems, including frequency equations, modal frequencies, and modal shapes. Four practical boundary conditions are considered for end supports, including free, sliding, pinned, and fixed boundaries, and a total of sixteen combinations of flooring systems are created. The deductions of analytical formulae are also expanded to two unequal span continuous flooring systems with pinned end supports, and empirical equations for obtaining the fundamental frequency are proposed. The acquired analytical equations for vibrational characteristics can be applied for practical design of two-span continuous flooring systems. Two practical design examples are provided as well.
... where: N is the axial force and A is the cross-sectional area According to [6,16] the design bending strength about the grain and principal axis is calculated for wood class C24: ...
This paper describes the optimum design and life cycle cost (LCC) assessment of timber roofs for sustainable construction. For this purpose, collar beam roof construction in a typical single-family house was analyzed. Special focus was placed on the impact of the patch cross-section position for different rafter spacing. The calculations were performed for four roof angles (15°, 30°, 45°, 60°). The main goal was to find the optimum LCC for each angle. It was found that smaller rafter spacing generates a higher assembly cost and takes more time to construct. On the other hand, the wood cost for these elements is lower. The implications of LCC were evaluated to find out which patch and rafter cross-section, as well as rafter spacing for each roof angle is the most economical solution.
... The timber floor is a one-way system, which means the floor slab is supported on two opposite sides only and bent in one direction. The equivalent viscous damping ratio of the timber floor (denoted by 1 ) is 2%, as is commonly practised (Thelandersson andLarsen, 2003, McKenzie andZhang, 2007). ...
Shape memory alloy (SMA) is becoming a popularly studied smart material in the field of structural control. The feasibility of utilising an SMA in a tuneable mass damper to reduce the excessive vibration of a timber floor system was revealed in a pilot study. However, the in-service excitations on a floor can be complex and involve more frequencies and randomness; therefore, this paper aims to assess the effectiveness of the SMA-based semi-active TMD in a real-scale timber floor, where the free vibration and human footfall-induced vibration are considered as inputs. This study is conducted using numerical simulations on OPENSEES. By reducing the floor vibration at a range of frequencies, both cooling and heating the SMA are effective in retuning the off-tuned TMD and reducing the structural response. Footfall excitation involves more than one excitation frequencies, and the higher dominant frequencies can resonate with the off-tuning frequencies, increasing the structural response. Simulation results demonstrate that retuning using SMAs can effectively lower the structural response at a wide range of frequencies, thus attenuating the footfall-induced vibration.
... Bahadori-Jahromi et al. developed multi-webbed engineered I-joists for constructing timber floors [25,26]. Two technical books were also published on [27,28]. This paper details a comprehensive study carried out on the dynamic response of timber flooring systems on behalf of the Metal Web Working Group, comprising ITW Alpine, Gang Nail Systems, MiTek Industries Ltd. and Wolf Systems [29]. ...
... From this study it is observed that the strength properties is directly proportional to it density. McKenzie also observed similar trend where strength properties increase with increasing density [23]. ...
The data performance for structural usage of highly engineered wood is very useful, however, the lacking of the data is
very much concern for fast-growing indigenous timber species in timber engineering field. In correlation with that, the
strength properties behaviour of Endospermum diadenum has to be studied to analyse the distribution pattern of strength
properties at a different distance from the vortex also known as pith. The species have been obtained from the East
Campus of Universiti Malaysia Sarawak’s forest reserve. Strength properties test were carried out namely, static bending
(modulus of rupture – MOR and modulus of elasticity – MOE), and the compressive strength (compression stress
parallel to grain). Meanwhile, physical properties test was carried out namely, moisture content (MC) and density. Small
specimens measuring 20 x 20 mm were tested in green and dry conditions in accordance with British Standard, BS
373:1957 (British Standards Institution, 1957). The green condition refers to moisture content greater than 19 percent
and dry condition with moisture content less than or equal 19 percent. All the results that had been tested were analyzed
using statistical analysis as mean results. The strength properties of specimen increased from the pith towards the
sapwood in which the strength is the lowest at 25 mm from pith followed by 50 mm, and the highest is at 75 mm from
the pith. Distribution of the basic density also increases slightly from the pith towards the sapwood with a significant
increment in average mean value at 25 mm from vortex with 0.54 g/cm3, 0.62 g/cm3 at 50 mm and 0.66 g/cm3 at 75 mm
from the vortex. Meanwhile, for dry condition, the increases in average mean value with 0.425 g/cm3 at 25 mm,
0.427 g/cm3 at 50 mm and 0.47 g/cm3 at 75 mm from the vortex. It can be concluded that the physical properties of the
wood have a direct impact on the wood stiffness and strength.
... The heaviest species, i.e. those with most wood substance, have thick cell walls and small cell cavities. They also have the highest densities and consequently are the strongest species, (McKenzie, 2000). Apart from that, effect of knots also caused the variety the mechanical strength value. ...
Timber is a renewable resource and preferred as building and construction material due to physical, mechanical, and has an aesthetically performance. However, timber varies due to its own property and proposes. The quality of the timber has a strong influence on the quality and value of timber products. Therefore, this study will be conducted to learn about mechanical strength properties of Terbulan (Endospermum diadenum sp.) fast-growing timber according to BS 373: 1957 Methods of Testing Small Clear Specimens of Timber. Instead of strength property, this study will be determined the suitable utilization of Terbulan timber for the construction industry. The test will be conducted on both conditions which are green and air-dry condition. Generally, Terbulan species is a fast-growing timber in Sarawak. From the point of view, the strength properties parameters such as basic density, modulus of rupture (MOR), modulus of elasticity (MOE) and compressive strength of Terbulan timber will be reviewed to determine the effectiveness of the species in the construction field. As a result of the analysis, it is found that Terbulan timber at the air-dry condition for MOR, MOE and compression parallel to grain reported with 84.17 N/mm², 10217.79 N/mm² and 28.94 N/mm² respectively. Terbulan is categorized in light hardwood timber and conclusion, related products are confined at the beginning it is a steel and concrete replacement that is mostly used in structure such as light construction, furniture and joinery.
... Weckendorf and co-workers studied the vibrational perform- ance of timber floors constructed with I-joists (Weckendorf, 2009;Weckendorf et al., 2008aWeckendorf et al., , 2008bWeckendorf et al., , 2010. Two technical books were also published on timber structural design to Eurocode (McKenzie and Zhang, 2007;Porteous and Kermani, 2012). ...
The aim of this research is to assess the effects of joist spacing, strongbacks and ceiling on the dynamic response of timber floors with metal web joists so as to evaluate the vibrational design criteria, for example, modal frequencies, modal shapes, damping and unit point load deflection, required by Eurocode 5-1-1 and the UK National Annex for timber floors. In general, joist spacing, strongbacks and ceiling do not greatly influence the fundamental frequency and damping ratio, but affect higher modal frequencies. The measured damping ratio for the fundamental mode is 0·86% on average. The use of strongbacks considerably reduces the number of first-order modes below 40 Hz, and provides easier fulfilment of the velocity design criterion. The test results indicate that the decrease in joist spacing, the increase in number, size and stiffness of strongbacks, and the use of a ceiling all greatly reduce the maximum displacement of the floors. On average, the calculated displacements based on the equations in the UK National Annex are close to those measured.
... Dowel-type fasteners include: nails, staples, bolts, dowels-smooth or threaded-and screws. Connector-type fasteners include: tooth-plates, splitrings, shear plates and punched metal plates in which the load transmission is primarily achieved by large bearing area at the surface of the members [39][40]. ...
Novel architectural forms can be created by connecting reciprocal frame (RF) and mutually supported elements (MSE) circuits together. These networks produce interesting architectural and engineering opportunities and challenges. The opportunities include the creation of roof and standalone structures that have distinctive architectural expression. The challenges include the determination of the often-complex configuration geometry between the elements and their connection system. A key feature of sloping RF and MSE geometry is that at the joint locations the element's centroidal axes generally do not coincide. An eccentricity at these positions has therefore to be incorporated within the connection system. This has a direct impact on element sizing, connection design, fabrication and erection sequences. RF and MSE spatial structure networks give rise to complex structural behaviour. Element-to-element connection eccentricity orientation is a controlling key feature in the determination of how the forces, moments and stresses are distributed between MSEs. The orientation of the eccentricity can be random or aligned to produce a vertical intersection distance as generally used in RF construction. The eccentricity derived from the common perpendicular to the centroidal axes is more commonly used in MSE circuit assembly. This paper considers the various methods used to connect RF and MSE networks and discusses their impact and comparative design advantages and disadvantages.
... Bahadori-Jahromi et al. developed multi-webbed engineered I-joists for constructing timber floors [25,26]. Two technical books were also published on [27,28]. This paper details a comprehensive study carried out on the dynamic response of timber flooring systems on behalf of the Metal Web Working Group, comprising ITW Alpine, Gang Nail Systems, MiTek Industries Ltd. and Wolf Systems [29]. ...
Metal web engineered timber joists are increasingly being used nowadays to replace traditional solid timber joists for constructing intermediate-span timber floors in low-rise houses and long-span floors in commercial buildings. Vibrational performance criteria become crucial for serviceability design of timber floors and often control the design. This paper presents an experimental study carried out on the dynamic performance of a series of full-scale floors constructed with metal-web joists with focus on modal frequencies, modal shapes and damping. The effects of a range of floor component configurations including spacing of joists, type, size, number and location of strongback, ceiling, etc., were examined. In general, joist spacing, strongback bracings and ceiling did not significantly influence the fundamental frequency and the corresponding damping ratio, required for the design of timber floors, but they did influence higher modal frequencies. The measured damping ratio for the fundamental mode was 0.9% on average, which is below the recommended value of 1% in Eurocode 5 Part 1-1 and much smaller than the recommended value of 2% in the UK National Annex to the code. The use of strongbacks, however, could considerably reduce the number of first-order modes below 40 Hz, used to determine the unit impulse velocity response, and in turn it could result in easier fulfilment of velocity design criterion.
... Wood can be compressed perpendicular and parallel to the grain. Compression parallel to the grain is common in wood constructions, i. e. in the top and bottom of horizontal joining elements or vertical elements in which load is applied from the both sides [14,15]. Resistance to the compression perpendicular to grain depends on the wood microstructure and loading direction (radial or tangential). ...
The influence of thermal treatment on the compression strength and static bending resistance of pinewood has been investigated. The thermal treatment conditions close to real technological regimes were selected. The samples were dried at 60, 80, 100 and 120 °C for 24, 48, 72 and 96 hours. Linear dimensions of the samples were 20 mm × 20 mm in cross section and length 30 mm for compression and 300 mm for bending test. It was shown that the thermal treatment increases compression resistance parallel to the grain, while compression perpendicular to the grain and bending strength decreases. The increase of thermal treatment regimes decreases bending strength of pinewood. Average width of annual rings also influences mechanical properties; larger width of annual rings increases compression strength perpendicular to the grain in radial direction. Static bending at these conditions reaches the lowest values. The character of dependencies between static bending strength and width of annual rings does not change under thermal treatment.
... Spanning capability and timber flanges make metal web joist a more desirable alternative to all steel systems. In the Eurocode 5 Part 1-1 [1] and the corresponding UK National Annex [2], vibrational criteria become crucial for serviceability design of timber floors and often control the overall design [3,4]. Those criteria include fundamental frequency, unit point load deflection and unit impulse velocity. ...
Metal web engineered timber joists have been largely used nowadays to replace traditional solid timber joists for constructing intermediate-span timber floors in low-rise houses and long-span floors in commercial buildings. Vibrational criteria become crucial for serviceability design of timber floors and often control the design. This paper presents the study on the dynamic performance of the floors constructed with metal-web joists with focus on modal frequencies, modal shapes and damping. The studied parameters included spacing of joists, type, size, number and location of strongback, ceiling, etc. In general, joist spacing, strongback bracings and ceiling did not significantly influence the fundamental frequency and damping ratio for Mode 1-1, both required for the design of timber floors, but they did influence those of higher modes. The measured damping ratio for the fundamental mode was 0.87% on average, which is below the 1% recommended in Eurocode 5 and much smaller than the 2% recommended in the UK National Annex. The use of strongback, however, could considerably reduce the number of first-order modes below 40 Hz, which, used to determine the unit impulse velocity response, can thus be decreased notably.
... Testing of defect free specimens is a good method to compare the effects of different treatment processes and/or different treatment conditions. However, results of tests cannot be used for the calculation of constructive elements, at least not without the use of several safety factors [11,24,31,32]. The occurrence of natural defects in wood, such as knots, resin pockets, reaction wood and an abnormal slope of grain, decreases the strength properties of timber. ...
Thermal modification at relatively high temperatures (ranging from 150 to 260°C) is an effective method to improve the dimensional stability and resistance against fungal attack. This study was performed to investigate the impact of heat treatment on the mechanical properties of wood. An industrially-used two-stage heat treatment method under relative mild conditions (< 200°C) was used to treat the boards. Heat treatment revealed a clear effect on the mechanical properties of softwood species. The tensile strength parallel to the grain showed a rather large decrease, whereas the compressive strength parallel to the fibre increased after heat treatment. The bending strength, which is a combination of the tensile stress, compressive stress and shear stress, was lower after heat treatment. This decrease was less than the decrease of only the tensile strength. The impact strength showed a rather large decrease after heat treatment. An increase of the modulus of elasticity during the bending test has been noticed after heat treatment. Changes and/or modifications of the main wood components appear to be involved in the effects of heat treatment on the mechanical properties. The possible effect of degradation and modification of hemicelluloses, degradation and/or crystallization of amorphous cellulose, and polycondensation reactions of lignin on the mechanical properties of heat treated wood have been discussed. The effect of natural defects, such as knots, resin pockets, abnormal slope of grain and reaction wood, on the strength properties of wood appeared to be affected by heat treatment. Nevertheless, heat treated timber shows potential for use in constructions, but it is important to carefully consider the stresses that occur in a construction and some practical consequences when heat treated timber is used.
This study is aimed at investigating those parameters related to timber flooring that can affect the acceptability of vibration behaviour of a timber floor in a residential building in view of the criteria stated in Eurocode EC5. The timber floor investigated is made of OSB/3 floorboards and timber joists. The parameters that are investigated in this study are thickness of flooring, floor joist span, joist spacing and connection of floorboards to the joists. In this context, two cases are considered. First: the flooring is nailed or screwed to the joists and no composite action or interaction is obtained between joists and floorboards. Second: the flooring is glued sufficiently to the joists and full interaction is obtained. The result suggests that glued floorboards perform much better with respect to natural frequency, static deflection and peak floor velocity than nailed or screwed floorboards. In almost all cases of glued floorboards, the result complies fully with the Eurocode 5 design vibration requirements. However, as floor lengths increase, the static deflection will increase beyond the allowable limit, especially for relatively thin floor panels and relatively widely spread joists. For both cases, increasing floorboards thickness and decreasing the joist span by adding more beams can yield even better results to satisfy the requirement of vibration comfort.
Traditionally, as a structural material, timber transferred the forces.
This chapter explains the mathematical and basic theoretical application as stipulated in the EYM.
Cross-Laminated Timber (CLT) is an engineered timber composite that is finding increasing structural application in construction today. Analysis of the structural behavior of CLT can be carried out by various analytical and numerical methods. Due to the complex behavior of CLT, use of numerical modelling such as the Finite Element Method (FEM) offers a convenient approach to analysis. In this paper, simulation of the elastic behavior of 1-way and 2-way spanning CLT panels using the FEM program ABAQUS is presented. Various modelling choices are explored numerically with the results being evaluated against those from either a 3D analytical method known as the State Space Approach (SSA) or existing experimental data. Among the case studies examined is a novel boundary condition for the SSA solution. In general, the optimum finite element model produced reasonable levels of accuracy with an average relative error equal to 3% in comparison to the SSA and a maximum of 10% in comparison to the experimental results.
In this article, cross-laminated timber panels are investigated as a novel engineering application of the state-space approach. As cross-laminated timber is a laminated composite panel, the three-dimensional analytical method provided by the state-space approach offers the potential for improved accuracy over existing common approaches to the analysis of cross-laminated timber. Before focusing on the specific application to cross-laminated timber, the general theory of the state-space approach is outlined. The method is then applied to describe the behaviour of a number of cross-laminated timber panel configurations previously examined experimentally and analytically. In order to demonstrate the capability of the state-space approach in this application, the results are compared with those from various two-dimensional and three-dimensional analytical approaches and finite element modelling briefly. With a view to design, different failure criteria are explored to assess the ultimate strength of the cross-laminated timber panels. The state-space approach demonstrates its superior capability in capturing the nonlinear distribution of the elastic stresses through the thickness of the cross-laminated timber panels over a range of span-to-thickness ratios common in practical applications.
The use of bolted sleeve joints has been proposed for assembling pultruded glass fiber-reinforced polymer (GFRP) tubular profiles into space lattice shell structures. Such joint configurations may introduce a semi-rigid end condition and further affect the capacity of the connecting members in compression. Three batches of specimens assembled with pultruded GFRP profiles of different lengths and bolted sleeve joints at both ends were prepared and tested under static axial compression. A detailed three-dimensional finite element model considering bolt geometry, contact behavior, bolt pretension, initial geometric imperfection, and failure criterion for fiber-reinforced polymer (FRP) composites was developed and validated with experimental results showing good comparisons. It was found that the bolted sleeve joints exhibited semi-rigid behavior and that the failure modes and the effective length factor were dependent on member slenderness. The relationship between effective length factor and member slenderness was derived based on finite element analysis and then used in conjunction with existing FRP column design equations to predict the member capacity for structural members with bolted sleeve joint end conditions.
This study investigated the impact of an industrially used two-stage heat-treatment method on the mechanical properties of full construction timber. Bending tests of full-size Norway spruce posts demonstrated changes due to heat treatment, such as a decrease in the density and bending strength, as well as an increase in the modulus of elasticity (MOE). The variability in bending strength and MOE appeared to be higher for treated posts and as a result the 5% values decreased, especially for the bending strength. The MOE was dependent on density for both treated and untreated posts, but this was not so for the bending strength. There appeared to be a relationship between the bending strength and the MOE, although it was rather weak, especially for treated posts. It was difficult to correlate the occurrence of natural defects in treated Norway spruce posts with an effect on the mechanical properties. Only a combination of several defects, such as large knots, enclosed pith and a deviating slope of grain, appeared to decrease the bending strength and MOE of treated posts, at least more than for untreated posts. The effect of a three year period of outdoor exposure on the strength properties of heat-treated terrace planking was limited. In particular, for the 5% value low strength range, where wood defects strongly determine the mechanical properties of wood, a three-year outdoor exposure did not change the bending strength or MOE of heat-treated wood.
ResearchGate has not been able to resolve any references for this publication.