| 1. |
- Bolmsvik, Åsa, 1975-, et al.
(författare)
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Vibration Distribution Due to Continous, Intermittent or Half Embedded Elastomer Connections in Wooden Constructions
- 2016
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Ingår i: Proceeding of the 2016 World Conference on Timber Engineering (WCTE), August 22-25, 2016 Vienna. - Vienna : TU-MV Media Verlag. - 9783903039001 - 9783903024359 ; , s. 2912-2920
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Konferensbidrag (refereegranskat)abstract
- Elastomers are commonly used to decrease the sound transmission between apartments in timber framed houses. In previous studies, different types of elastomers have been evaluated experimentally. The wooden assemblies, in which elastomers were used in the connections, showed that elastomers cause the vibrations to increase in the direction perpendicular to the applied load within the low frequency span.In this study, the effects on acceleration, depending on how the elastomers are placed are studied. The cases having the elastomer continuous, placed as intermittent pieces or positioned half embedded in the junctions are evaluated.The frequency dependent properties of the elastomers are needed in order to model the dynamic behaviour and thereby be able to predict sound- and vibration transmission in wooden houses. Here, the properties of a wooden construction having different elastomers connections are studied to enable simulations of the behaviour of the elastomers in a FE model in the future.
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| 2. |
- Buck, Dietrich, et al.
(författare)
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Further Development of Cross-Laminated Timber (CLT) : Mechanical Tests on 45° Alternating Layers
- 2016
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Ingår i: WCTE 2016 : Proceedings. - Vienna : Vienna University of Technology, Austria. - 9783903039001 ; , s. 1107-1114
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Konferensbidrag (refereegranskat)abstract
- In this paper, a series of experimental bending and compression tests were performed on cross-laminated timber (CLT) products with ±45° alternating layers, to evaluate their performance against conventional panels of 90° orientation. Engineered wood products, such as CLT with ±45° alternating layers can provide opportunities for greater use in larger and more sustainable timber constructions. A total of 40 panels, manufactured in an industrial CLT production line with either of these two configurations, were tested and compared. Panels were evaluated in bending tests n=20 and the remaining ones in compression tests. Results showed that 35% increased the strength in the four-point bending tests for panels containing ±45° alternating layers compared with the 90° alternating layers. Compression strength was increased by 15%. Stiffness increased by 15% in the four-point bending and 30% in the compression. The results indicate that CLT containing ±45° alternating layers has increased strength and stiffness compared to 90° alternating layers. These findings suggest that further developments in CLT are feasible in advanced building applications.
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| 3. |
- Fortino, Stefania, et al.
(författare)
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A multi-Fickian hygro-thermal model for timber bridge elements under Northern Europe climates
- 2016
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Ingår i: WCTE 2016. - 9783903024359 ; , s. 2068-2075
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Konferensbidrag (refereegranskat)abstract
- This work proposes a multi-Fickian method to analyse the hygro-thermal behaviour of timber bridge elements under Northern Europe climates. A temperature-dependent wood hysteresis is included in the model and the thermal effects due to temperatures above and below zero are taken into account. As a case study, the model is used for the hygro-thermal simulation of a glulam beam of Älsvbacka bridge in North of Sweden that was monitored by using wireless sensors in a previous study. The model, implemented in Abaqus FEM code, is able to predict the states of moisture and temperature in protected parts of the beam by using as external loads the relative humidity and temperature of the air provided by in-situ measurements. Furthermore a simplified model using a wood hysteresis independent of temperature is found to provide similar results and appears easier to implement in finite element codes.
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| 4. |
- Just, Alar, et al.
(författare)
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Execution of timber structures and fire safety
- 2016
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Ingår i: WCTE 2016. - 9783903024359 ; , s. 5555-5562
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Konferensbidrag (refereegranskat)abstract
- Fire safety is one of the six essential performance requirements to consider when building timber structures. Fire safety has to be proven for the whole building process and the end use of the building. On the building site during the execution there might be an increased risk for fire spread because of large amounts of unprotected timber and relatively open structures. Work processes dealing with high temperatures, smoking, vandalism or other reasons can lead to ignition of timber and end up with serious damages. Fire safety on the building site should be handled from the very beginning to the final stage of execution. During the execution the designed solutions have to be checked and followed. This paper gives the background and principles that should be considered in a new Nordic standard for execution of timber structures in terms of fire safety.
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| 5. |
- Lange, David, et al.
(författare)
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Reliability of timber elements exposed to fire
- 2016
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Ingår i: WCTE 2016. - 9783903024359 ; , s. 3874-3883
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Konferensbidrag (refereegranskat)abstract
- This paper discusses the principles of performance based structural design and motivates the need for probabilistic assessment of the response of structures and an assessment of the consequences of failure. Using the results from a series of tests carried out at SP in Sweden, we extrapolate data required for the assessment of timber structures under a range of parametric fires. This data also includes information required to develop probabilistic models of the response of timber elements under different parametric fires. Using methodologies from the literature, we then carry out a reliability analysis of timber structures, considering uncertainties the timberresponse to fire. This is carried out using the first order reliability method. We show that the opening factor has an influence on the reliability of timber structures, as a result of the rate of heating in a parametric fire exposure. A minimum reliability, evolving over time, is seen to occur at an opening factor of 0.14m1/2. Finally, we propose a modification to the Eurocode target reliability indices that allows these to be used as a target reliability index for structures exposed to fire. The proposed modification is dependent on the floor area and the method is exemplified here for a range of floor areas and its application to timber structures is illustrated.
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| 6. |
- Niklewski, Jonas, et al.
(författare)
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Durability of rain-exposed timber bridge joints and components
- 2016
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Ingår i: WCTE 2016. - 9783903024359 ; , s. 4667-4675
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Konferensbidrag (refereegranskat)abstract
- The design of details is an important aspect in durability design of rain-exposed timber structures. Joints are considered the weak-points of these structures as they accumulate moisture and facilitate deterioration by decay. The present study aims to study the influence of detail design, and its effect on the service life, by estimating the decay rate in a number of rain-exposed timber components and joints, typically found in timber bridges. A test-setup was exposed outdoors over a period of one year while the moisture content was measured in specific measuring points. The test-setup included groups of beams, columns and joints commonly found in timberbridges. For the beams and columns, the effectiveness of typical protective measures was also tested. The annual decay rate was estimated using two different decay prediction models. Compared to a reference beam, the results show that structural protection reduced the risk of decay while joints and end-grain tended to be at increased risk. The lowest service life, estimated to 3-4 years, was found close to end-grain where drying was hindered but moisture could accumulate. In general, the discrepancy between the two decay models was large for low to medium exposure and decreased with increasing exposure.
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| 7. |
- Ohman, Micael Bjorn, et al.
(författare)
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Dimensional stability in four different wooden facade claddings
- 2016
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Ingår i: WCTE 2016. - 9783903024359 ; , s. 2810-2818
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Konferensbidrag (refereegranskat)abstract
- The hypothesis is that a good cladding system in wood should be characterized by a homogeneous dimensional behaviour with minimal variation between individual panel boards to minimize maintenance, i.e. repainting or, in the worst case, replacement of whole panels. Four different types of cladding panels were tested: a regular spruce panel, a quality-sorted P-marked spruce panel, a regular panel of pine heartwood and a spruce glulam panel, 50 panels of each type. The objective was to study the dimensional changes under changing moisture conditions in order to find the cladding material with the smallest possible dimensional and distortion movements. The shape stability of the panels was measured and expressed in terms of bow, spring, twist and cupping. The spruce glulam panels showed the best shape stability, proven significantly different in comparison to the other two spruce panel systems. Panels of pine heartwood showed a tendency greater dimensional stability than the spruce panels, but not enough to be considered statistically significantly different in this study.
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| 8. |
- Olsson, Anders, 1973-
(författare)
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Determination of sawn timber properties using laser scanning : Development potentials and industrial applications
- 2016
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Ingår i: WCTE 2016 - World Conference on Timber Engineering. - Vienna : tuverlag. - 9783903024359 ; , s. 82-91
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Konferensbidrag (refereegranskat)abstract
- This paper starts with an overview of methods for machine strength grading of timber being used in industry. It discusses attempts that have been made over the years to improve the accuracy of different grading concepts. Then a newly approved method based on laser scanning and utilization of the tracheid effect is presented. It utilizes high resolution data supplied by an industrial scanner and it gives, in comparison to other methods, very accurate results. Still it is based on several crude assumptions. Therefore the latter part of the paper takes a starting point in the limitations of this scanning based method and discusses what can be done within research and development to reach an even higher grading accuracy. Future work should lead to detailed and accurate models for timber, including geometry of knots, growth layers and fibre orientation in 3D and information of local material stiffness properties, and it should be possible to establish such models for individual boards in productions speed. Some recent and ongoing research that contributes in this direction is discussed. With access to accurate timber models several different strategies for prediction of strength and other engineering properties would be possible.
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| 9. |
- Olsson, Jörgen, 1975-, et al.
(författare)
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Low Frequency Force to Sound Pressure Transfer Function Measurements Using a Modified Tapping Machine on a Light Weight Wooden Joinst Floor
- 2016
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Ingår i: Proceedings of WCTE, World Conference on timber Engineering, August 22-25, 2016, Vienna, Austria. - Vienna : Vienna University of Technology. - 9783903039001 ; , s. 2888-2895
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In recent years research has shown that low frequency impact sound is of significant importance for inhabitants´ perception of impact sound in buildings with light weight wooden joist floors. The tapping machine is well defined as an excitation device and is a standard tool for building acoustics. However, the excitation force spectrum generated for each individual floor is unknown when using a tapping machine. In order to increase the possibilities to compare simulations to impact sound measurements, there is a need for improvement of impact sound measurement methods. By measuring the input force spectrum by a modified tapping machine and the sound in the receiver room, transfer functions can be achieved.In the light weight wooden building used for the evaluation test of the proposed method, structural nonlinearities are evident in the frequency response functions stemming from different excitation levels. This implies that for accurate FRF-measurements in low frequencies, excitation magnitudes that are similar to these stemming from human excitations should preferably be used.
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| 10. |
- Pousette, Anna, et al.
(författare)
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Innovative façade elements of wood with modern design and new technology
- 2016
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Ingår i: WCTE 2016. - 9783903024359 ; , s. 3365-3372
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Konferensbidrag (refereegranskat)abstract
- The project included product development and materials research. The aim was to produce a wooden façade system with an attractive modern appearance and good constructive design with the help of modern woodworking technology. Important requirements to consider were that the system should have a contemporary, attractive expression and that the façade system should provide a product with high quality ambitions in terms of environmental impact. It should also be flexible and easy to use for architects and designers who want to create unique façades. The main focus in this study was about the visible wood surface appearance where the intention was to create a varied surface with interesting innovative designs, with a method that make it possible to always create new patterns. Two different façade cladding systems were developed by combining woodcraft tradition, new research, digital design tools and industrial processes in the wood construction industry. Prototypes with patterned surfaces on both individual boards joined together and on a system based on multi-layer solid wood panels were tested.
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| 11. |
- Rossi, Simone, et al.
(författare)
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Load-bearing capacity of ductile multiple shear steel-to-timber connections
- 2016
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Ingår i: WCTE 2016. - 9783903024359 ; , s. 195-203
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Konferensbidrag (refereegranskat)abstract
- The strength of connections typically governs the cross-sectional size of structural timber members. This is particularly true when multiple slotted-in plates and dowels are used. In such a case, in fact, the larger the number of slotted-in plates - which practically means "the wider the cross section" - the higher the capacity per dowel will be. However, in the case of several slotted-in plates, due to inevitable fabrication tolerances the plates of the connection could be unevenly loaded. It is very important, therefore, to choose a layout of the connection that allows for a ductile behaviour and thus for a possible load redistribution among the dowels and ultimately contribute to the overall robustness of the structure. The present paper deals with the results of an investigation conducted on dowel-type connections with multiple slottedin steel plates. A large set of laboratory tests were carried out at the Division of Structural Engineering, Lund University, Sweden. The tests were conducted by varying two different parameters, i.e. the number of slotted-in steel plates and the thickness of the timber elements. The objectives were 1) to assess the influence of these parameters on the performance of the timber joints in terms of load-bearing capacity, stiffness, and ductility; and 2) to provide design guidance in order to prevent premature (brittle) failure of the connection.
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| 12. |
- Östman, Birgit, et al.
(författare)
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Fire Safety Engineering – Opportunities and challenges for timber buildings
- 2016
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Ingår i: WCTE 2016. - 9783903024359 ; , s. 3829-3838
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Konferensbidrag (refereegranskat)abstract
- The combustibility of timber is one of the main reasons that many building regulations strictly limit the use of timber as a building material. Fire safety is an important contribution to feeling safe, and an important criterion for the choice of building materials. The main precondition for an increased use of timber in buildings is adequate fire safety. This paper reviews the opportunities and challenges to reach this goal by implementing Fire Safety Engineering and Performance Based Design principles.
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