Timber Wall Research Articles

Experimental behaviour of a full-scale timber-concrete composite floor with mechanical connectors

The timber-concrete composite (TCC) beam is a construction technique that can be used for upgrading of existing timber floors without the need of demolition. This possibility has been investigated through full-scale tests on a 6-storey experimental building with light-frame timber walls and platform construction, where the existing timber floor for domestic use was upgraded for reuse as an office building. The acoustic flooring was replaced with a 60 mm lightweight concrete slab, connected to the existing joists with inclined shear connectors (SFS screws) to form the TCC floor. The floor and environmental conditions were monitored during the concrete pouring and hardening, and during the application of the live load. Two different types of construction, propped and unpropped, were compared, and an extensive experimental investigation was performed on material components (lightweight concrete, timber, and connection system) with the aim to fully characterise the behaviour under short- and long-term loading. The unpropped floor was then tested to failure under monotonic loading, and two different boundary conditions, namely the actual joist-to-wall joint and a perfectly pinned support, were investigated. An advanced FE model was validated on the test results and used to predict the deflection in the long-term. The composite floor achieved the target stiffness and the design load for satisfying ultimate and serviceability limit states for office loading in the UK. The actual joist-to-wall restraint was characterized by a low degree of fixity, however it produced early longitudinal crack formation in the proximity of the support. The final collapse of the floor as a whole occurred progressively under increasing load after failure for fracture in tension of an individual joist. The higher drying shrinkage of lightweight concrete raised the deflection during concrete curing and hardening.

Structural behaviour of log timber walls under lateral in-plane loads

The present works intends to represent a further step in the knowledge of timber log-houses through an experimental approach, from which only few information is available. The main part of the experimental work is based on in-plane static tests conducted on timber log walls with distinct transversal stiffness, two vertical compression levels and different values of slenderness. Monotonic and cyclic tests were performed according to EN 12512:2001. The former were performed to define the elastic slip values and assessment of the failure mechanisms while the latter allowed for the evaluation of the impairment of strength, the measurement of the ductility and the quantification the energy dissipation. Previously to the full-scale tests of walls, an extensive characterization of the timber logs was made. Due to its importance, the connection between the first timber log and the basement was also evaluated through tests. In a second step of the research, a case study was used to develop a numeric analysis. Using FEM, the in-plane stiffness of timber logs walls was quantified, thus allowing to compare the result of distributing the horizontal loads by the walls according to their area of influence or their in-plane stiffness. Finally, improvements to the log system analyzed were suggested.

Laboratory experiments on hygrothermal behaviour of real-scale timber walls

Hygrothermal performance of massive wood and wooden materials used as structural purposes in building envelope are measured by means of laboratory tests. For this purpose, hygrothermal short-time behaviour of two massive timber walls exposed to summer climatic conditions were investigated. A double climatic chamber simulating real on-site conditions was designed and built at the LERMAB/ENSTIB site in Epinal and used during wall behaviour assessment. Temperature and

Shear performance of green timber wall panels

Korean building industry was developed by concrete and steel construction. However, concrete and steel have some problems which low carbon storage capability and difficulty of recycling. According to many studies, timber has high carbon storage capability, high recycling capability and sustainable supporting capability. Focus on this factors of timber, make new wall structure as Green Timber Wall panels and check the shear performance to use wall system in housing construction such as light-weight timber construction and nondearing wall on other construction. In the results, B-4-B and B-4-S show similar modulus of shear stiffness on the table. GH-4-GH has slip shape failure mode between Green Timber Wall boards. GH-4-GV has most stable characteristic curve than other specimens.

Variability of Charring Along the Wooden Wall Studs

The effect of timber densities on the charring of timber members insulated by heat-resistant mineral wool is described in this paper. Special attention is given to variability of charring along the stud. After the fire tests, the studs were saved in their entire length. Char layer was mechanically removed from the studs under investigation. Charred studs of timber frame walls were scanned three-dimensionally over the full length afterfull-scale fire tests. Densities were measured by X-ray and optical vibration scanner. Cross-section properties and densities of the studs were measured along the stud. Charring rate is not uniform along the full length of a single timber wall stud. This corresponds probably to the variation of density of wood. Adjusting the designmodel for charring of timber frame assemblies, as given in EN 1995-1-2, to allow for the influence of density may give an advantage for members with higher density.

Construction time and cost for post-tensioned timber buildings

This paper describes post-tensioned timber alternative designs for a six-storey office building in New Zealand. The building has long-span timber–concrete composite floors supported on laminated veneer lumber beams, columns and walls. Lateral loads are resisted with moment-resisting post-tensioned timber frames in one direction and post-tensioned cantilever timber walls in the other direction. This paper compares the time and cost of timber construction with the concrete building actually being constructed. Construction times of the timber and concrete buildings are found to be almost identical. The cost of the timber alternative is approximately 6% more than concrete or steel designs. This paper demonstrates the opportunity for post-tensioned timber to compete with concrete and steel for multi-storey long-span office buildings, providing a more sustainable alternative.

An experimental study of solid timber external wall performance under simulated bushfire attack

With the increasing threat of climate change there is a need to use renewable and green materials such as timber for house constructions. Timber is not generally regarded as a suitable material for the construction of homes in bushfire (or wildland fire) prone areas. However, our understanding of the performance of solid timber wall constructions under bushfire conditions is still limited. The objective of this research was to conduct a pilot experimental study of a solid timber wall system to assess its performance under severe bushfire attack conditions typical in Australia's bush land. Eight log wall specimens with and without various protection coatings were exposed to thermal radiation field produced by a gas-fired radiation panel at the BRL A40 level in accordance with the relevant Australian test standard. The heat flux on the exposed surface and temperatures on both the exposed and unexposed surfaces were measured. Flaming combustion and self-extinguishment were observed on most of the specimens while the external radiant heat varied from 40 kW/m 2 to 16 kW/m 2. The charring depth of the log walls was also measured. The performance of the solid timber walls was evaluated against the relevant standard. The experimental work showed that solid log wall assemblies are resistant to severe bushfire threat and timber can be a suitable material for building in bushfire prone areas if sufficiently thick and well sealed.

Experimental study of cross-laminated timber wall panels

The use of cross-laminated structural timber elements is becoming increasingly popular. The number of layers varies normally from three upwards. The structural performance of five-layer cross-laminated timber elements was investigated. The five layers consisted of 19 mm thick boards, laid successively at right angles to each other and glued together with PU-adhesive, layers 1, 3 and 5 lying in one direction and layers 2 and 4 in the other. The stiffness and strength of four cross-laminated timber elements (4955 mm long, 1250 mm wide and 96 mm thick) were studied during in-plane bending. Two of the elements were first partitioned into two parts that were reconnected in two different ways prior to testing. The influence of the way in which the cross-laminated timber elements were reconnected was studied, the behaviour observed being compared with the test results for the unpartitioned specimens with respect to both strength and stiffness. The experimental tests performed showed the cross-laminated timber elements to possess a high degree of stiffness and strength. There was also found to be a marked difference in behaviour between the two different ways in which the elements were connected to each other. One of the two connecting methods studied, being of less good design but earlier frequently used in Sweden, showed as expected poor structural performance, whereas the other one applied as a safer alternative performed well.

STUDY ON CALCURATION METHOD OF TENSILE AXIAL FORCE ACTING ON CONNECTION OF TIMBER WALL STRUCTURES

The objective of this study is to propose a calcuration method of tensile axial force acting on connections at top and bottom sheathed shear walls in timber wall structures. And the method is applied to practical design for light frame construction, simplified formulae using shear resistance factor are derived. The formulae are composed of three terms, and the axial force can be shown as the sums of vertical shear force in the shear wall, dead load, and additional force from the overturning moment generated in the boundary beam. The method and the formulae are confirmed by full-scale racking tests of 2-story walls of light frame construction. Concluding remarks are as follows: 1) The method can be applied to tha varieties of the shape of sheathed panels. 2) The method can be also applied to the varietied of disposition of walls in stories. 3) Calcuration values that uses existing stress and shear resistance factor are coincident satisfactorily with the experimental values.

FIRE RESISTANCE OF JAPANESE TRADITIONAL TIMBER-FRAME SOIL INTERNAL WALLS EXPOSED TO BOTH-SIDES HEATING

Mechanical fire resistance of internal load bearing walls under both-sides heating is important for the prevention of collapse of a dwelling in a fire. Feasibility of the 45 minutes mechanical fire resistance with Japanese traditional timber-frame soil internal wall is studied for this purpose. The tests were initiated with intermediate scale specimens for the examination of the charring and internal temperature field of the column and then loaded tests under both-sides exposure were conducted on two 1-story tall bare-timber wall specimens. The tests suggest significant influence of the mortises of columns for horizontal timber bars on the buckling of walls. The conventional predictive method of the mechanical fire resistance of bare timber walls is then modified for the tested configuration.

Life-time Material Effectiveness Analysis of Building Components

The paper compares the life-time material effectiveness of five exterior walls used to build residential build- ings. Effectiveness was measured by the MIPS method. The five exterior walls compared were: 1) a precast concrete wall, 2) a brick and concrete wall, 3) a brick and timber wall, 4) a timber wall, and 5) a straw wall. Expected service life of the exterior wall was 100 years. The precast concrete wall will consume about twice as much material over its 100-year lifespan as a wooden wall. The length of the service life of a wall affects the material effectiveness of concrete and brick walls significantly.

Nonstationary heat transfer in an inhomogeneous thermally insulated timber sample

A mathematical model and numerical methods to calculate the thermal state of a fragment of the exterior timber wall of a building are suggested. The character of the distribution of temperature fields in homogeneous and inhomogeneous (thermally insulated) timbers and the influence of the thermophysical and geometrical characteristics of a homogeneous timber sample and warmth-keeping lagging on it are determined.

University Of Ulster, FireSERT's New Laboratories

With the increasing threat of climate change there is a need to use renewable and green materials such as timber for house constructions. Current Australian standards for the construction of homes in bushfire prone areas do not consider the use of timber as a suitable material. However, our understanding of fire performance of solid timber wall constructions is still very limited. A new test standard has been drafted recently to set a special test protocol emulating Australian bushfire conditions. The objective of this research was to conduct a pilot study of experimental testing of a solid timber wall system utilising the basic principles of the Draft Standard AS 1530.8.1 to assess the wall performance under extreme bushfire attack. The experimental work showed that solid log wall assemblies are resistant to extreme bushfire threat and timber can be a suitable material for building in bushfire prone areas if sufficiently thick and well sealed.

Out-of-Plane Seismic Evaluation and Retrofit of Turn-of-the-Century North American Masonry Walls

Three masonry walls with their wood backing were extracted from an old three-story residential building. These specimens are representative of a type of construction widely used in North America circa 1900, in which a single wythe exterior masonry wall was tied only with nails to the timber structure, leaving an irregular gap between the masonry and timber walls. To seismically retrofit such buildings, special seismic-resistant anchorage of the walls would be required at every floor at a minimum. Questions remained, however, as to the out-of-plane resistance of the remaining walls spanning between floors. To partly answer these questions, the three specimens extracted from the existing building were tested using a shake table, submitting them to multiple ground motions of progressively larger intensity until structural failure. These tests have demonstrated that such walls could resist significant out-of-plane inertial accelerations without failure. Performance can be increased by different retrofit methods such as providing anchors at midheight to force the wood and masonry wall to move as a unit, and adding fiberglass strips epoxied to the masonry wall to increase its out-of-plane stiffness and strength.

Meldon Bridge: a centre of the third millennium BC in Peeblesshire

Rescue excavations on an extensive cropmark site at the confluence of the Lyne Water and Meldon Burn in the 1970s revealed several episodes of activity. A limited Mesolithic presence is indicated by the stone finds, but more intensive use is attested from the early/mid fourth millennium BC. Widely scattered groups of pits contained Impressed Ware of the local style. Radiocarbon dates chart this activity down to the early/mid third millennium BC, when a massive timber wall, 600 m long and up to 4 m in height, was constructed to shut off the 8 ha promontory between the Lyne Water and Meldon Burn. A timber avenue led into the enclosure on the north-west; standing posts and stones and settings of posts and stakes were erected; and cremation burials took place in the interior. No cultural material can certainly be associated with this phase and it probably lasted a century or less. A large stockade within the main enclosure could not be dated with certainty. A disturbed cist burial, yielding a jet pendant, 'slug' knife and possible Food Vessel sherds, may have been interred as one ofthe final acts in this phase. Renewed activity came in the mid/late second millennium BC, when the site was used for an extensive cremation cemetery. This involved erecting rows of posts, some standing in pits containing cremations. There was also a burial in a rough cist, and two cremations deposited in Cordoned Urns. There is no evidence for further activity until the Roman period when the road from Newstead to Castledykes was driven through the site, disturbing some of the prehistoric features. There were Roman forts just to the west at Easter Happrew and Lyne, and large temporary camps at Meldon Bridge itself. One of these partly overlay the prehistoric site, and appeared to have been constructed after the road. Long afterwards an 18th-century turnpike road was laid down on top of the old Roman road. At least some of the gravel pits found on both sides of the road were dug in this phase.

THE INFLUENCE OF MOISTURE ON THE COMBUSTION OF WOOD

A new three-dimensional (3-D) field model for enclosure fire growth has been developed by CSIRO and UNSW, Australia. The model includes the coupling of gas-phase combustion and the pyrolysis of wood. It has been used to predict the flame spread and fire development in a room witha rear timber wall and a propane burner. A parametric study of the effects of the moisture content of the timber on the flame spread and development of the fire in a room is described. The computed results compare satisfactorily with measurements from a fire test carefully conducted in a room.

Corrosion of lead shielding in a radiology department.

Corrosion of lead sheet used for structural radiation protection in the Princess Alexandra Hospital radiology department has been identified. The corrosion is thought to have been caused by organic acid vapours released from oregon timber wall panelling. Non-destructive testing (NDT) and X-ray transmission measurements were used to define the extent and severity of damage, and subsequently to provide the data necessary for estimation of staff and public radiation doses. Although radiation dose limits have not been exceeded, corrective actions including structural modifications and staff information sessions have been undertaken.

House dust mite allergen levels in public places in New Zealand

Background: House dust mite allergens are a risk factor for asthma in New Zealand, and levels in domestic dwellings have been found to be high compared with levels in most other countries. Studies in other countries have demonstrated lower levels of Dermatophagoides pteronyssinus allergens in public places compared with levels in domestic dwellings. Objectives: The purpose of this study was to measure reservoir Der p 1 levels in public places in New Zealand and to examine determinants of these levels. Methods: Reservoir dust was obtained in the two centers (Christchurch and Wellington) from hotels, hospitals, rest homes, churches, primary schools, childcare centers, cinemas, bank head offices, and airplanes; samples were also obtained from ski lodges. Single measurements of temperature and relative humidity were taken with thermohygrometers and an average humidity over 2 weeks was estimated with use of waxed wooden sticks. Information was collected on building construction, type of heating, and frequency of cleaning. Der p 1 levels (micrograms per gram of fine dust) for floor ( n = 202), bed ( n = 65), and seat ( n = 24) samples in public places were expressed as geometric means (95% confidence intervals). Results: Der p 1 levels in public places were significantly lower than domestic levels in both Wellington and Christchurch. Both floor and bed levels were higher in hotels than in other public places. After controlling for potential confounders, floor Der p 1 levels were higher with carpeted floors ( p < 0.0001) and lower with recent cleaning ( p = 0.02) and bed Der p 1 levels were higher with timber wall construction ( p = 0.03). Other building, heating, or cleaning characteristics did not show significant associations with allergen levels. Conclusion: Der p 1 levels were much lower in public places than in domestic dwellings with floor levels primarily affected by floor covering. (J Allergy Clin Immunol 1997;99:587-93.)

Moisture Conditions in a North Facing Wall with Cellulose Loose Fill Insulation: Constructions with and without Vapor Retarder and Air Leakage

This paper presents calculated moisture conditions of a wall exposed to a climate equivalent to the North of Sweden. A north facing timber wall with a brick facade and cellulose loose fill thermal insulation is studied both with and without vapor retarder and air leakage. If the vapor retarder is eliminated from the construction, the moisture levels will increase to unacceptable high values. The con struction becomes sensitive to the choice of facing materials and the indoor moisture supply. Air leakage carrying moist air into the construction leads to unacceptably high values even for moderate indoor moisture supplies.

An Archaeomagnetic Study of a Wattle and Daub Building Collapse

AbstractArchaeomagnetic methods, originally developed to assist in the reconstruction of pottery vessels, are applied to the study of sintered remains of Neolithic wattle and daub buildings in Calabria, Italy in order better to understand the circumstances of burning and structural collapse.These Stentinello-culture buildings from Piana di Curinga comprise one of the densest areas of Neolithic settlement known in the western Mediterranean. A spinner magnetometer was used to analyze both the orientations of thermoremanent magnetism vectors in one structure's daub fragments as well as the intersection angles they make with timber imprints and wall surface planes. It was found, in conjunction with experimentation, that the building was probably intentionally burned and that those who set fire to it knew the structure's walls would at least partially collapse. Several lines of evidence indicate how old, abandoned daub buildings were probably set afire so as to harden and hence preserve the pieces of now-fired...