PROBABILISTIC CONDITION ASSESSMENT TECHNIQUE FOR TIMBER POWER POLES

Timber poles are extensively used in Australia to support overhead electric and telecommunication facilities. The strength of the pole degrades over time, and pole failure can have serious safety and economic implications. The failure occurs when stresses exceed the remaining strength of the timber element. In this paper, a probabilistic framework is developed to estimate the remaining life of the timber power pole system. The developed framework permits the user to consider the variability in the capacity of the timber pole and cross-arm, loading and deterioration processes, and to propagate the uncertainty associated in each stage of the assessment procedure. Further, the time-dependent failure rate of the pole system is estimated to develop the risk matrix to improve the current renewal and replacement decision making process used by the utility companies in Australia.

Strength Properties of Chestnut Structural Timber with Wane

Grading of timber for structural purposes allows material with similar physical and mechanical properties to be grouped together. The groups are defined by specific strength values and indicate the basic working stresses and stiffnesses to be used for structural design purposes. In particular, visual strength grading bases the assignment of each timber element to a grade on the characteristics that are visually measurable (i.e. knots, slope of grain, annual ring width). Very similar principles are implemented for the in situ assessment of timber structures, as recommended for example by the Italian standard UNI 11119, that specifies the procedures for the diagnosis of timber members. Currently, however, European standards and most of the national standards on strength grading refer to timber elements with rectangular cross section, while in existing buildings, members with irregular cross section are extremely common. Thus, 10 different provenances (5 from Italy and 5 from France) of chestnut timber were sampled. More than 600 structural elements with wane were visually examined in laboratory and all the characteristics were collected. Bending tests were then performed on each timber element until failure, and bending strength, as well as modulus of elasticity and density, were determined. Here, the limitations for the main strength-reducing characteristics and the characteristic values (fifth percentile for bending strength and density and the mean value for modulus of elasticity) of chestnut timber with wane are presented.

Investigation on the Self-Tapping Screws Capability to Induce Internal Stress in Timber Elements

In refurbishment operation of existing timber floors could prove of some interest the possibility of hogging the existing timber beams, in case of the presence of excessive permanent midspan deflections. In the case of sagged timber floors which cannot be buttressed due to heritage issues, the possibility of cambering a timber beam by simply putting another wooden beam on the top of it and inserting screws inclined at 45° relative to the beam axis has been experimentally investigated, with some promising result. The cambering procedure has proved to be more effective when the fastener are inserting starting from the internal part of the beam, permitting to obtain significant values of upward deflection (it has been observed an upward deflection of about one three-hundredth of the total beam length): the values could possibly be increased by reducing the screw spacing or by using fasteners able to generate a greater pressure. The effectiveness of this method is based on the capability of self-tapping screws to induce internal stress in timber element during the drilling procedure: the horizontal component of the resultant pressure yielded by the inclined screws is directly related to the possibility to hog the composite system. The aim of the experimental campaign described in this paper was to investigate the values of the internal stress induced by different type of fasteners during the drilling procedure, studying the influence of different parameters such as screw angle with respect to the grain direction, initial pressure, head penetration length, threaded part length, connector typology, wood density, time-dependence.

EXPERIMENTAL INVESTIGATION OF GLUED LAMINATED TIMBER BEAM-TO-BEAM CONNECTION / KLIJUOTOSIOS MEDIENOS SIJOS ELEMENTŲ TARPUSAVIO JUNGTIES EKSPERIMENTINIS TYRIMAS

Semi rigid mounting joints of glued laminated timber elements are connections that are fully assembled on construction site and capable to handle bending moments, axial and shear forces. The need for new type of semi rigid timber elements’ connection is obvious. The manufacturing possibilities of glued laminated timber elements’ are wide: straight element's length may extend up to 40 m or curved axis elements with dimensions of up to 10 meters in height, therefore, manufacturers, erectors and others face with transportation problems of non-standard, oversized elements. Semi-rigid mounting joints are used to solve this problem. In factory non-standard, oversized, glued, laminated timber elements are cut into standard transportation dimensions and fully mounted into integral element on construction site, using semi rigid mounting joints. In this article semi-rigid, glued, laminated timber elements’ joints which are used as beam to beam, beam to column and column to foundation connections are analysed. Also the main design principles of semi-rigid joints are discussed. The new type of semi rigid beam to beam connection is proposed and experimentally analysed. The experimentally and theoretically analysed connection is composed of welded steel details which are anchored into timber element. The main experiment is four point bending; the analysed connection is in the middle of the span. The beam's span is 3.20 m; the dimensions of the timber element's cross section are: width 200 mm; height 400 mm; mounting bolts are M16. Glued laminated timber strength class is GL24h. The tight contact between timber element and steel detail is created by anchoring steel detail's T shape part into timber element. The initial movement between timber element and steel detail is eliminated using fillers. Two types of fillers are used in these experiments: two component polyurethane and cement based filler with polymer fibres. Two joints with different fillers are tested in laboratory experiments. Bending bearing capacity and stiffness (displacements) of the joints’ are determined in laboratory. Experimental bearing capacities are compared with theoretical calculations according to European (EC5) and Lithuanian timber structures design codes. Conclusions and recommendations are presented for further experiments and computer simulations. Santrauka Straipsnyje analizuojami pusiau standūs montuojamieji klijuotosios medienos konstrukcijų mazgai, kurie naudojami elementams sujungti per ilgį, rėmų kampinėms jungtims tarp kolonos ir sijos bei jungtims tarp kolonos ir pamato. Aptariami pagrindiniai pusiau standžių montuojamųjų medinių konstrukcijų mazgų konstravimo principai. Pasiūlytas ir eksperimentiškai tirtas per ilgį sujungtų lenkiamųjų klijuotosios medienos sijos elementų mazgas. Mazgas įrengiamas naudojant plienines detales, suvirintas iš lakštinio plieno, kurios inkaruojamos medienos elementuose. Kontaktas tarp medienos ir metalo užtikrinamas ir pradinis mazgo slankumas panaikinamas užpildant tarpus tarp medienos ir metalo užpildu. Pasirinkti du skirtingo pagrindo (sudėties) užpildai: dviejų komponentų poliuretano ir cementinis, kurio sudėtyje yra polimerinių plaušų. Nustatytas cementinio užpildo lekiamasis ir gniuždomasis stipriai. Eksperimentinės jungčių laikomosios galios palyginamos su teoriniais skaičiavimais pagal Lietuvos ir Europos medinių konstrukcijų projektavimo normas. Pateikiamos išvados ir rekomendacijos tolesniems tyrimams.

The position effect of structural Eucalyptus round timber on the flexural modulus of elasticity

Round timber has great use in civil construction, performing the function of beams, columns, foundations, poles for power distribution among others, with the advantage of not being processed, such as lumber. The structural design of round timber requires determining the elastic properties, mainly the modulus of elasticity. The Brazilian standards responsible for the stiffness and strength determination of round timber are in effect for over twenty years with no technical review. Round timber, for generally present an axis with non-zero curvature according to the position of the element in the bending test, may exhibit different values of modulus of elasticity. This study aims to analyze the position effect of Eucalyptus grandis round timber on the flexural modulus of elasticity. The three-point bending test was evaluated in two different positions based on the longitudinal rotation of the round timber element. The results revealed that at least two different positions of the round timber element are desired to obtain significant modulus of elasticity.

Timber beams subjected to long - term loading

Timber beams subjected to long - term loadingWood is a significant structural material, which is often used for timber bearing structures. Elements of timber structures must especially satisfy safety requirements, which are expressed by the ultimate limit states in the established standards. The structure must also satisfy the serviceability limit states. Local and global deformations make it impossible for the structure to serve the purpose it was designed for. It is important to take the deflections and their possible increase into account in the design to provide a structure which can be used during the whole period of service. Based on earlier examinations, it is known that a timber element over the course of long-term loading shows creep behavior. The structure of wood is able to adapt to the conditions of the surrounding environment. The properties of wood are especially affected by the relative humidity of the air and then by the type, intensity and duration of the loading. The most important factors affecting the serviceability of timber structures are volume changes caused by humidity and additional deflections caused by the effects of long-term loading. These phenomena emphasize the importance of serviceability limit states for timber structures. The paper deals with a long-term experimental investigation of timber girders that are currently often used. The aim was to obtain the deflection curves and mark the time dependence and the final deflections. The paper will also define the approximations for simulating the time-dependent deflections and obtain the creep coefficients for calculating the final deflections of the girders investigated.

GIS-BASED RESTORATION SYSTEM FOR HISTORIC TIMBER BUILDINGS USING RFID TECHNOLOGY/GIS PAREMTA ISTORINIŲ RĄSTINIŲ PASTATŲ RESTAURAVIMO SISTEMA TAIKANT RFID TECHNOLOGIJĄ

Using geographic information system (GIS) and other established technologies, this paper develops an information management system that integrates graphic and non‐graphic data to enhance the effectiveness of historic building restoration work in Taiwan. Radio frequency identification (RFID) is used to permit real‐time tracking of assembly components and thus enhance restoration management efficiency. Restoration data stored in the memory of RFID tags can be changed and updated according to the needs of a specific restoration phase. The use of RFID handheld readers both improves data collection efficiency and system mobility. In the developed system, timber structure restoration data and drawings in the GIS can be accessed online immediately for use in the restoration process and to help advise strategic design, construction, and management decisions. Data of each timber element, including restoration sequence, restoration contractors, supervisors, evaluated strength capacity etc can be retrieved remotely through a handheld PDA reader‐writer used onsite. Data of component construction sequence during disassembly or re‐assembly, critical to project success, can be transmitted in a synchronized manner to the developed host system to achieve a level of accuracy and reliability significantly greater than that typically achieved using traditional reconstruction management approaches. Santrauka Taikant geografinę informacinę sistemą (GIS) ir kitas technologijas, straipsnyje plėtojama informacinė valdymo sistema, integruojanti grafinius ir negrafinius duomenis, didinanti istorinių pastatų restauravimo efektyvumą Taivane. Sudedamiesiems komponentams stebėti realiajame laike taikomas radijo dažnių identifikavimas (RFID), taip didinant restauravimo valdymo efektyvumą. Saugomi RFID ženklių atmintyje restauravimo duomenys gali būti keičiami ir atnaujinami pagal specifinės restauravimo fazės reikmes. Taikant RFID delninius skaitytuvus gerėja tiek duomenų kaupimo efektyvumas, tiek sistemos mobilumas. Sukurtoje sistemoje rąstų statinio restauravimo duomenys ir piešiniai (brėžiniai) geografinėje informacinėje sistemoje gali būti iš karto pasiekiami kompiuteriniu tinklu ir taikomi restauravimo procese bei padėti strategiškai projektuojant, konstruojant, taip pat ir valdymo sprendimams priimti. Kiekvieno rąsto elemento duomenys, restauravimo seka, restauravimo vykdytojai, prižiūrėtojai, stiprybių galimybės ir kita gali būti pasiekiami nuotoliniu būdu su delniniu PDA skaitytuvu-rašytuvu darbo vietoje. Komponentų konstravimo eilės tvarkos išmontuojant ar sumontuojant duomenys gali būti sinchroniškai perduodami sukurtai valdančiai sistemai siekiant daug didesnio tikslumo ir patikimumo lygio, nei įprastai pasiekiama taikant tradicinius restauravimo valdymo taikymus.

Eilean an Duin, Craignish, mid Argyll.

Summary In 1983 construction work led to the destruction of part of the island fort of Eilean an Duin and an archaeological investigation was undertaken. Two sections were cut through the stone-built rampart, and one through interior deposits of the site. The rampart may originally have included a timber element which had been burnt. In the interior a clear occupation deposit was recorded. Radiocarbon dates suggest that pre-rampart occupation occurred late in the first millennium BC; the fortification must have been built soon after.