This paper describes the experimental analysis of joints made with threaded steel rods epoxy-glued into high-density hardwood. Seventy specimens of 10 different types were tested until failure with a ...pull-pull device. The objective of the study was to evaluate the influence of the geometric and mechanical parameters of the joint on axial strength. Experimental results question the application of the existing joint design formulas to the case of high-density hardwood. Hence, experimental study on glued joints should be extended to include a greater variety of timbers of different densities.
Celotno besedilo
Dostopno za:
DOBA, FGGLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Pilot projects are common platforms for developing/testing construction methods or solutions for e.g. low-energy house-building. Whereas studies report on their technical/engineering outcomes, little ...is known from a learning perspective. In our study of pilot-project learning, the planning for and assessment of learning from a “low-energy quarter” pilot was explored. In step one, the initiators and the local authority participantswere addressed. The findings of the interviews indicatedthe changed understandings during the pilot of e.g. the planning and design criteria for sustainable building. Although stressed at the pilot outset, it seems that the learning among the stakeholders was not so well documented or systematically evaluated and shared so that the mainstream practice could have been informed or changed.
Timber buildings were widely constructed until reinforced concrete became popular due to availability of the material and workmanship in Turkey. The masters of the timber works presented different ...construction techniques, configurations, and styles. After the trend turned to reinforced concrete and steel, the timber construction techniques became obsolete and even the existing timber buildings suffered from the lack of interest, repair, and maintenance. As a result the historical building stock started to perish. Despite some appropriate restoration attempts for the timber structures, the limited number does not offer any confidence for the future of those structures. In this respect, this study aims to present the timber structural systems for buildings, to expose the current conditions of existing timber structures, and to concentrate on the structural restoration of an important historical timber structure in Turkey.
The use of adhesives to produce assembled structural joints in the building industry is increasing, particularly in the context of on-site rehabilitation of timber structures. On their own or ...together with steel or fibre reinforced polymer composite connecting materials, adhesives can
provide low intrusive, fast, versatile and effective on-site repair or reinforcement interventions to timber structures. Most common applications involve sealing and repair of cracks, drying fissures and delamination of glued laminated members; replacement of decayed beam ends; strengthening
of timber members; and repair and strengthening of mechanical timber joints. The performance of bonded joints highly depends on their design and detailing, surfaces preparation, selection and application of adhesives, and full compliance with their cure schedule. Therefore, the work should
be carried out by well-informed, trained and certified operators following a Quality Assurance Program to ensure satisfactory end-product strength and durability. Despite some recent developments, the exploitation of the full potential for on-site bonded joints is mainly restrained at
present by the lack of structural design guidance, standards for durability assessment and onsite acceptance testing. This article discusses briefly the use of adhesives on the construction site in the context of structural repair and reinforcement; the requirements and practical difficulties
in the work on site with regards to the strength and durability of the rehabilitated timber structure; and the consequent need for quality control. It also highlights the characteristics and requirements that must be fulfilled by structural adhesives and reinforcing materials; factors affecting
performance and durability of bonded joints; and ways to improve adhesion and durability. Finally, it points out some research needs and future developments identified by the authors.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
In order to improve the mechanical performance of timber beams, five rectangular-section beams were used in flexural test and ten for shearing. The effects of FRP types i.e. CFRP, BFRP and AFRP, ...layers of FRP sheets and the way FRP sheets pasted were studied. The failure pattern, load-deflection curve, strain distribution and ultimate load capacity of the specimens were analyzed. The results indicate that the ultimate load carrying capacity of beams were increased by 15.4% to 55.1% varyingly with the reinforcement of FRP, besides, the stiffness and ductility were improved also. The improvements were lower in the specimens with material defects such as the existence of knags and shrink cracks. It’s more effective to paste the FRP sheets slantingly with the angle of 45° than vertically. However, the effect on the initial stiffness is not distinct whether reinforced or not. The analysis of strain and stress distribution manifests that the plane cross-section assumption is efficient in design and calculation of FRP reinforced timber beam.
Modern timber construction techniques rely on metallic connectors. Their failure during fires is related to shear failure, which can happen at lower temperatures than those leading to pyrolysis. ...Based on this information, a series of tests were carried out exposing wood specimens to various heat fluxes in a Cone Calorimeter on a vertical configuration with no pilot ignition and a normal air atmosphere. The aim of this investigation was to develop a dependable temperature measurement methodology in wood samples exposed to high heat fluxes and to build a data-base in order to assess different wood pyrolysis models. The experiments yielded highly repeatable results that are hard to achieve with wood, although at lower heat fluxes the repeatability was poorer. The data were then normalized using a simple, inert, heat transfer model. It will be used as a tool to assess the importance of different terms that are incorporated in models that predict in-depth temperature profiles for wood. The samples behaved almost like an inert solid when subjected to low heat fluxes. Poorer repeatability at the lower levels of heat flux is justified by the beginning of pyrolytic reactions in wood at about 10
kW
m
−2.
In partially anchored shear walls, the leading stud is not fully anchored against the uplift; hence the uplifting force is resisted by the sheathing-to-framing joint along the bottom rail. These ...joint forces will introduce crosswise bending and shear in the bottom rail leading to possible splitting failures. To design partially anchored shear walls, plastic design methods can be used and, therefore, the bottom rails must not fail in a brittle manner. In this paper, results of two experimental programmes with respect to the splitting capacity of bottom rails with double-sided sheathing due to uplift in partially anchored shear walls are presented. This was evaluated varying the distance between the washer edge and the edge of the bottom rail, and the pith orientation of the bottom rail. The experimental results show two brittle failure modes for the bottom rail: (1) a crack opening from the bottom surface of the bottom rail and (2) a crack opening from the edge surface of the bottom rail. The results indicate that the distance from the edge of the washer to the edges of the bottom rail has a decisive influence on the load-carrying capacity and failure modes of the bottom rail.
The paper presents information about preservation of historic timber structures in the Kizhi open-air museum (Russian Federation). The approaches used by the restorers and conservators at the time of ...the museum establishment and existence are described. The system of biological control of timber structures used nowadays in the museum aims to prevent biodeterioration as a main factor decreasing the service life of wooden structures. The proposed monitoring system enables determination of the zones damaged by fungi and insects, assessment of the activity of a wide range of biological agents at initial stages, environmental control of biodeterioration. Introduction of the proposed monitoring system in the Kizhi museums proved its effectiveness. In combination with timely repair and elimination of the revealed defects, it increases the service life of historic timber structures while preserving their authenticity.
An apparent analytical peculiarity or paradox in the bending behavior of elastic-composite beams with interlayer slip, sandwich beams, or other similar problems subjected to boundary moments exists. ...For a fully composite beam subjected to such end moments, the partial composite model will render a nonvanishing uniform value for the normal force in the individual subelement. This is from a formal mathematical point of view in apparent contradiction with the boundary conditions, in which the normal force in the individual subelement usually is assumed to vanish at the extremity of the beam. This mathematical paradox can be explained with the concept of boundary layer. The bending of the partially composite beam expressed in dimensionless form depends only on one structural parameter related to the stiffness of the connection between the two subelements. An asymptotic method is used to characterize the normal force and the bending moment in the individual subelement to this dimensionless connection parameter. The outer expansion that is valid away from the boundary and the inner expansion valid within the layer adjacent to the boundary (beam extremity) are analytically given. The inner and outer expansions are matched by using Prandtl’s matching condition over a region located at the edge of the boundary layer. The thickness of the boundary layer is the inverse of the dimensionless connection parameter. Finite-element results confirm the analytical results and the sensitivity of the bending solution to the mesh density, especially in the edge zone with stress gradient. Finally, composite beams with interlayer slip can be treated in the same manner as nonlocal elastic beams. The fundamental differential equation appearing in the constitutive law associated with the partial-composite action in a nonlocal elasticity framework is discussed. Such an integral formulation of the constitutive equation encompassing the behavior of the whole of the beam allows the investigation of the mechanical problem with the boundary-element method.
Celotno besedilo
Dostopno za:
DOBA, FGGLJ, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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