Rectangular Timber Research Articles

Thickness of zero-strength layer in timber beam exposed to fuel-controlled parametric fires

Fire resistance is one of the essential requirements to be fulfilled in the design of timber structures. For this purpose, a reduced cross-section method is given in the European standards, Eurocodes. The method is based on the assumption that an initial, rectangular timber cross-section exposed to fire conditions reduces to an effective cross-section, which has material properties as at a room temperature. The reduced part of the cross-section with no resistance is determined by a sum of two parameters, namely a charring depth and a thickness of zero-strength layer. Eurocodes give a value of the latter only for the standard fire exposure, which is only one of the fire curves proposed in the same standards. Therefore, the present paper examines the thickness of zero-strength layer in case of 46 different fuel-controlled parametric fire exposures applied to a timber beam from three sides. A four-phase numerical analysis is applied for this purpose that includes the use of a hygro-thermal model and a mechanical model to determine temperatures of timber over the cross-section and the mechanical resistance of timber beam in fire conditions, respectively. The results show that the thickness of zero-strength layer takes the values between 7.9 and 18.4 mm for the fuel-controlled parametric fire exposures. Since it is clearly dependent on the parameters describing the parametric fire curve, five equations are proposed that can be used for determination of the thickness of zero-strength layer in case of parametric fire exposures.

Reuse process for timber elements to optimise residual performances in subsequent life cycles

The reuse of wooden elements is a sustainable operation, which makes the best use of the material’s grey energy. Currently, structural timber from selective demolition is mainly used for non-structural functions, with a lowering of its performance, due to the lack of standard and specific regulation. In fact, the visual grading used to define the structural characteristics of wood does not evaluate information deriving from the previous life cycles of the component. In the paper, taking samples of rectangular timber elements from selective demolitions made in the Valencian Community, the structural values that are assigned by visual strength grading legislation were compared with the real resistance values identified by experimental analysis to verify their compliance. The verification showed that the visual grading is not able to optimize the performance of the timber element in its reuse. Therefore, the purpose of the research, illustrated in the paper, is to find a reuse process for structural wooden elements to enhance residual performances. The identified process introduces additional steps compared in the current visual grading, that include a consideration of the effective modalities of reuse evaluated according to the worst defects and information arising from previous life cycles.

Reuse process for timber elements to optimise residual performances in subsequent life cycles

The reuse of wooden elements is a sustainable operation, which makes the best use of the material’s grey energy. Currently, structural timber from selective demolition is mainly used for non-structural functions, with a lowering of its performance, due to the lack of standard and specific regulation. In fact, the visual grading used to define the structural characteristics of wood does not evaluate information deriving from the previous life cycles of the component. In the paper, taking samples of rectangular timber elements from selective demolitions made in the Valencian Community, the structural values that are assigned by visual strength grading legislation were compared with the real resistance values identified by experimental analysis to verify their compliance. The verification showed that the visual grading is not able to optimize the performance of the timber element in its reuse. Therefore, the purpose of the research, illustrated in the paper, is to find a reuse process for structural wooden elements to enhance residual performances. The identified process introduces additional steps compared in the current visual grading, that include a consideration of the effective modalities of reuse evaluated according to the worst defects and information arising from previous life cycles.

Using Optimization Algorithms-Based ANN to Determine the Temperatures in Timber Exposed to Fire for a Long Duration

The article investigates the temperature prediction in rectangular timber cross-sections exposed to fire. Timber density, exposure time, and the point coordinates within the cross-section are treated as inputs to determine the temperatures. A total of 54,776 samples of wood cross-sections with a variety of characteristics were considered in this study. Of the sample data, 70% was dedicated to training the networks, while the remaining 30% was used for testing the networks. Feed-forward networks with various topologies were employed to examine the temperatures of timber exposed to fire for more than 1500 s. The weight of the artificial neural network was optimized using bat and genetic algorithms. The results conclude that both algorithms are efficient and accurate tools for determining the temperatures, with the bat algorithm being marginally superior in accuracy than the genetic algorithm.

Effect of CFRP-Reinforcement variation on the strength parameters of different timber beams

Abstract This study investigated the effect of Carbon Fibre Reinforced Polymer (CFRP) reinforcement on the strength parameters of different timber beams, subjected to flexural loading. For this purpose, two different timber species i.e. Cedrus Deodara (Deodar) and Pinus Wallichiana (Kail) were used. Rectangular timber beams strengthened using CFRP bands of varying widths, were tested, and their performance was in turn compared to reference beams (without CFRP strengthening). The results from the experimental investigation revealed substantial enhancement in the various flexural performance parameters of both types of beams strengthened with CFRP. However, it was noted that the performance improvement was proportional to percentage of CFRP area adopted. Further, the improvement in the strength parameters was higher in Kail beams compared to Deodar beams. Thus, CFRP strengthening can be effectively used in the retrofitting of all deteriorated timber structures with promising results, hence, catering to the sustainability considerations as well.

Performance of timber girders with end-notch: Experimental and numerical investigation

Many bridges built during the colonial times in Australia have timber girders as load transferring elements and they are still in service with increased traffic loads and consistent deterioration. Most of the timber girders in those bridges are notched at the ends for better seating arrangement. Therefore, it is necessary to quantify the strength characteristics of notched girders in order to ensure structural safety and make necessary intervention to extend their service lives. Hence experimental tests were conducted on the notched rectangular timber girder samples with three different notch depths (i.e.10%, 15% and 30% of the depth of beam) having the notched angle of 1:4. Consequently, detailed finite element models were developed for notched timber girders, and the models were validated with experimental results. The validated model was used to predict the shear and flexural strengths and stiffnesses of typical circular and rectangular timber girders with two different spans (i.e. 6 m and 9 m), three different notch angles (i.e. 1: 0, 1:2 and 1:4) and three depths (i.e.15%, 30% and 45% o of the depth of beam). Strength data developed for notched timber were used to compare the applicability of the design provisions in various timber design standards. Experimental and finite element model test results show that when the notch depth increased from 15% to 45%, the load carrying capacity of rectangular timber girder was reduced by 50%. Whilst, the reduction of the load carrying capacity of the corresponding circular timber girder was slightly low (i.e. 37%). Further, when the notched angle changes from 1:0 to 1:4, the load carrying capacity of circular and rectangular girders increased about 50%, 69% and 110% for the notch depths 15%, 30% and 45%, respectively.

Effective Strengthening of Timber Beams: Experimental Investigation

AbstractThis paper presents an experimental study on the strengthening of rectangular timber beams under monotonic loading. Both flexural and shear behavior of the specimens was studied. A total of...

ANN prediction of fire temperature in timber

PurposeFire degradation is an extremely important risk that threatens timber structures. It is therefore normal that timber design codes include provisions for the design and verification of structures under fire loading. Eurocode 5 is no exception to this, but the simplified methods presented in the code show some inconsistencies, and the advanced method is not practical to use for design purposes. Artificial neural networks (ANNs) have the ability to model complex problems and have been used in a variety of construction engineering problems. They can learn from a subset of data, and then they can be used to predict the results for other input parameters. The purpose of this study is to present the possibility of the use of ANNs for the prediction of temperatures in rectangular timber cross sections, under fire exposure.Design/methodology/approachIn this work, a multilayer feedforward ANN has been trained to predict the temperatures within a timber cross section, using as input the size of the cross section, the timber density, the time of exposure and the coordinates of the point within the cross section.FindingsThe results obtained clearly indicate that ANN can be used to predict the temperatures in a timber cross section subjected to fire.Originality/valueANNs have not been used for the prediction of temperatures in timber cross sections. The use of ANN makes the temperature prediction under a standard fire loading in a cross section extremely easy to implement in any code. These results can be used to calculate the strength of the elements after fire.

Strengthening and rehabilitation of deteriorated timber bridge girders

Research has shown that strengthening of degraded rectangular timber is possible via the use of Fibre Reinforced Polymers (FRP). Tests were conducted at James Cook University (JCU) using three round timber girders removed from a railway bridge in North Queensland, Australia. These were retrofitted with either a Carbon Fibre Reinforced Polymer (CFRP) or Glass Fibre Reinforced Polymer (GFRP) composite in one of three different strengthening profiles. Due to extensive deterioration, two of those girders failed during preliminary tests and thus were repaired as opposed to strengthened. The repaired members sustained enhanced moment capacity and ductility from their initial failure values. The unbroken girder when strengthened, produced a 30% reduction in deflection for the same moment while bending stiffness was increased by 30% from its initial un-strengthened state.

An Analysis of the Load-Bearing Capacity of Timber-Concrete Composite Beams with Profiled Sheeting

AbstractThis paper presents an analysis of timber-concrete composite beams. Said composite beams consist of rectangular timber beams and concrete slabs poured into the steel sheeting. The concrete slab is connected with the timber beam using special shear connectors. The authors of this article are trying to patent these connectors. The article contains results from a numerical analysis. It is demonstrated that the type of steel sheeting used as a lost formwork has an influence on the load-bearing capacity and stiffness of the timber-concrete composite beams.

A Late Iron Age and Romano-British Site at Gale Common, North Yorkshire

A late Iron Age to late Romano-British rural landscape centred on two core occupation areas was identified. The western settlement, in the form of a nucleated Iron Age farmstead, was inhabited in the first century bc, while the eastern core was occupied from the late first century ad. Settlement was predominantly at a basic rural level, shifting eastwards during the later second century ad to a less regular settlement with a rectilinear field system. The settlement became more Romanised, incorporating in the middle of the fourth century ad a rectangular timber building and proportions of pottery types more usually associated with villas. The settlement appears to either move, contract, or begin to dissipate in the later fourth century ad.

Experimental Study on Properties of Different Angles of FRP Shear Reinforced Timber Beams

Study of fiber reinforced plastics (i.e. CFRP, BFRP and AFRP) for rectangular beams reinforcement effect, using the FRP were 90o vertically and 45o slantingly parceled 10 rectangular timber beams shear performance, recorded specimen failure process. This paper analyzes the different FRP reinforcement plies, different reinforcement on beam properties of specimen, failure mode, bearing capacity, load-deflection relationship and strain distribution. The results showed that: FRP changed beams brittle failure mode, improve the beam bending, shear performance, ultimate bearing capacity increased by 28.2%~55.1%, the stiffness of the specimen and also improved ductility. In addition, its more effective to paste the FRP sheets vertically than slantingly with the angle of 45°. Using FRP strengthening beams the performance of the method is effective, the method can significantly improve the performance of wood. To improve the utilization efficiency of wood, expand the application range of timber provides useful reference.

Correction of World Coordinate Error in the Three-Dimensional Laser Scanning System of Human Body

This paper studies three-dimensional laser scanning system of human body, and make adjustments according to the world coordinate error correction based on the point cloud obtained. This paper also analyzed the cause and characteristics of three-dimensional laser scanning system’s world coordinates error, and established the world coordinate correction model on the condition that vertical column coordinate error is not included in the calibration plane and the error is minimum relative to other highly cross-section. With a standard rectangular timber as the scan objects, correction factor is fitted and the effectiveness of this method is proved through experiments in which point cloud’s world coordinate error is significantly reduced.

Effect of increased charring on the narrow side of rectangular timber cross‐sections exposed to fire on three or four sides

AbstractOwing to the influence of two‐dimensional heat transfer, fire tests and heat transfer calculations show that charring on the narrow side of rectangular timber cross‐sections may be considerably greater than charring on the wide side. For timber members unprotected throughout the time of fire exposure as well as members initially protected from fire exposure, it is shown by calculation, that the relationship between charring on the narrow side and time is nonlinear. In order to take into account increased charring on the narrow side of timber members a section factor ks was determined. By calculation it is shown that bending moment resistance is only insignificantly influenced by the effect of two‐dimensional heat transfer and the factor ks can therefore be neglected, making the fire design of timber members easier. Copyright © 2011 John Wiley & Sons, Ltd.

The role of the house in early Neolithic Ireland

The focus of this article is the use and abandonment of the rectangular timber buildings of the Irish early Neolithic, a period that corresponds roughly with the first half of the fourth millennium cal BC. While they do not represent the only remains of occupation at this time, the fact that they display a striking degree of homogeneity of size, shape and materials makes them an especially interesting part of settlement activity on the island. One particular feature of this patterning is the frequency with which early Neolithic timber buildings have been substantially or completely destroyed by fire. It will be argued below that this burning was deliberate and played an important role in the lifecycle – the creation, maintenance and destruction – of these buildings. To provide a context for this discussion, a more in-depth look will be taken at these distinctive buildings and at their form and function.

Design Charts for Timber Beam‐Columns

A general procedure to construct design charts for rectangular timber columns with prescribed end eccentricities and initial bow is presented. The design charts use the new load and resistance factor design (LRFD) format. These charts can be used to check trail sections or obtain suitable combinations of axial load and moments for a particular section and slenderness ratio. The current design format requires repeated calculations of a series of factors. Values of maximum axial load to factored compressive resistance ratios, and moment-magnification factors for ratios equal to and below maximum can be obtained from a single chart as a function of slenderness ratio alone. Use of design charts is explained for both columns with axial load alone and combined bending and axial load via an example problem, in accordance with the \IOntario Highway Bridge Design Code.\N Similar design charts may be developed to aid designers, reduce computational errors, and save calculation time.

Plas Gogerddan, Dyfed: A Multi-Period Burial and Ritual Site

At Plas Gogerddan, evidence was discovered for human presence from the middle of the fourth millennium B.C. up to the present day. Numerous pits and post-holes were excavated around a standing stone; one of these pits was dated to the tenth-fifteenth centuries B. c. To the west of the standing stone, three ring-ditches were constructed and used in the first millennium B.C.; in association with these ring-ditches were three iron age crouched burials. In the vicinity of the standing stone lay twenty-two east-west aligned, extended inhumation graves, three of which were surrounded by rectangular timber structures. A coffin stain from one of these graves was dated to the third-seventh centuries A.D.

St. Peter's Church, Barton-upon-Humber: Excavation and Structural Study, 1978–81

SummaryFour seasons of excavation and structural study in St. Peter's Church have revealed a complex sequence, beginning with domestic occupation of the Pagan Saxon period, followed by a Middle Saxon settlement enclosure with adjacent cemetery of Christian character. In the later tenth century a three-celled turriform church was built in the cemetery, after the exhumation of graves covering its intended site. Related features in the cemetery include the foundation of a large free-standing cross, a group of wells and an oven, probably for baking bread, all grouped to the east of the chancel. Some of the pre-Conquest graves yielded evidence of probable barkwood coffins built with clenches and roves, while some twenty further graves contained rectangular timber coffins in varying states of preservation. Several were in near-perfect condition and have yielded exceptionally good evidence for techniques and tools employed by Anglo-Saxon carpenters.The extant Saxon and medieval fabric of the church has been recorded in considerable detail, providing an insight into building and scaffolding methods, particularly of the tenth century. Excavation has revealed the complex development of the medieval church and its internal layout; and 1,326 graves, spanning a millennium, have been investigated.

Effect of frame construction on the sound insulation of unsealed windows

The sound insulation of two sets of unsealed windows with different frame cross-sections has been examined. One set of frames was constructed in situ using rectangular timber sections, the others being proprietary steel windows. The results showed that the unsealed steel windows had much lower sound insulations than the unsealed timber windows for gaps of the same length and width. The differences are discussed in terms of the cross-sectional shapes of the respective gaps.

The Iron-Age Hill-Fort and Romano-British Iron-Working Settlement at Garden Hill, Sussex: Interim Report on Excavations, 1968-76

The earthwork at Garden Hill, Hartfield, East Sussex, until then unrecognised, was identified in 1968 by Mr C. F. Tebbutt, who found early RomanoBritish material in a trial excavation. Five seasons of excavation (1972-76) by the Garden Hill Excavation Group have established the broad outline of the site's history. A scatter of worked flints indicates slight occupation in the Neolithic/Bronze Age period. Attributed to the late pre-Roman Iron Age are a round house and part of what may be another. A hill-fort, with stonerevetted and palisaded defences, was built, possibly against the Roman invasion, but soon fell into disuse and was followed by Romano-British occupation. This included a rectangular timber building, roastingand smeltingfurnaces and a forging-hearth of the first century; a rectangular building with two verandahs, using timber uprights set on padstones and in post-holes, and a four-post structure on the same alignment, both probably first-century; a timber building set on a stone platform and attached stone bath-building, of the second century; and undated post-hole and timber-slot systems (not fully excavated) representing fences and other timber structures. It is possible that Garden Hill was the base from which local iron-smelting sites were operated in the first and second centuries.