Kjell Arne Malo

Kjell Arne Malo
Norwegian University of Science and Technology | NTNU · Department of Structural Engineering

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76
Publications
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Publications

Publications (76)
Article
Full-text available
Currently, there is limited knowledge of the dynamic response of taller glue laminated (glulam) timber buildings due to ambient vibrations. Based on previous studies, glulam frame connections, as well as non-structural elements (external timber walls and internal plasterboard partitions) can have a significant impact on the global stiffness propert...
Conference Paper
Full-text available
The next generation of Eurocode 5 "Design of timber structures" is currently planned with normative rules for prevention of fatigue failures in timber structures. Probably only a few building structures like windmill towers will need evaluation with respect to high numbers of cyclic loading, and the proposed rules will most likely be used in timber...
Article
Full-text available
A new timber frame structural system consisting of continuous columns, prefabricated hollow box timber decks and beam-to-column moment-resisting connections is investigated. The hollow box timber decks allow long spans with competitive floor height and efficient material consumption. To achieve long spans, semi-rigid connections at the corners of d...
Article
Full-text available
The use of moment-resisting frames with semi-rigid connections as a lateral load-carrying system in timber buildings can reduce the need for bracing with diagonal members or walls and allow for more open and flexible architecture. The overall performance of moment-resisting frames depends largely on the properties of their connections. Screwed-in t...
Article
The paper presents the results of a parametric study performed on FEM models of network arch timber bridges with inclined and spoked configuration of hangers. The study focuses on performance and instability of the arches depending on the geometry of the bridge. The parameters taken into account are the bridge span, the arch rise and the in-plane a...
Article
Long-span timber floor elements increase the adaptability of a building and they exhibit a significant market potential. High cost of the floor elements is a challenge, and the timber sector is under substantial pressure to find more economical solutions without weakening otherwise favourable environmental performance. The range of technical timber...
Article
Full-text available
Long-span timber floor elements increase the flexibility of a building and exhibit a significant market potential. Timber floor elements are endeavouring to fulfil this potential, but building projects employing long-span timber floors have encountered drawbacks. High costs and vibration performance are challenging, and the timber industry is under...
Article
A combined experimental and numerical approach to characterize a fracture process in wood composites of Norway Spruce is presented. Processed results of crack growth during wedge split tests in TL (tangential - longitudinal) and RL (radial-longitudinal) planes for mode I (opening) are used as a basis for numerical fracture characterization of wood...
Article
Full-text available
A wedge split test in mode I and mixed-mode was designed and performed for wood at structural component scale. The displacement fields around cracks during propagation were recorded and analysed to provide information on crack tip position, the composition of deformation modes, resistance to fracture propagation, and separation of the crack lips. T...
Article
As long-spanning timber floor elements attempt to achieve a meaningful market share, proof of serviceability continues to be a demanding task as international consensus remains unsettled. Initiatives to improve vibration levels are achievable, but a lack of confidence in the market is resulting in increases in margins for both manufacturers and con...
Article
Full-text available
Over the last decades, the increasing urbanization and environmental challenges have created a demand for mid-rise and high-rise timber buildings in modern cities. The major challenge for mid-rise and high-rise timber buildings typically is the fulfillment of the serviceability requirements, especially limitation with respect to the wind-induced di...
Article
The double notched shear test specimen has been redesigned to test wood in structural component scale using a compression test setup. A parametric finite element method (FEM) study was performed to obtain the best specimen shape within a domain of geometrically feasible layouts. Several criteria of stress state assessment were considered to charact...
Conference Paper
Full-text available
Wind-induced dynamic excitation is becoming a governing design action determining size and shape of modern Tall Timber Buildings (TTBs). The wind actions generate dynamic loading, causing discomfort or annoyance for occupants due to the perceived horizontal sway – i.e. vibration serviceability failure. Although some TTBs have been instrumented and...
Conference Paper
Wind-induced dynamic excitation is becoming a governing design action determining size and shape of modern tall timber buildings (TTBs). The wind actions generate dynamic loading, causing discomfort or annoyance for occupants due to the perceived horizontal sway – i.e. vibration serviceability failure. Although some TTBs have been instrumented and...
Article
Full-text available
Screwed-in threaded rods with wood screw threads feature high axial capacity and stiffness and can be used as fasteners in highly resistant and stiff timber connections. The purpose of the present paper is to review the existing literature and design rules in the present version of Eurocode 5 (EN 1995-1-1) and European Technical Assessments, to ide...
Article
Full-text available
Stress-laminated timber (SLT) decks in bridges are popular structural systems in bridge engineering. SLT decks are made from parallel timber beams placed side by side and pre-stressed together by means of steel rods. SLT decks can be in any length by just using displaced butt joints. The paper presents results from friction experiments performed in...
Article
Full-text available
Crack evolution in wood from Norway Spruce during mode I wedge splitting tests was measured using a Digital Image Correlation (DIC) system. The resulting series of deformation fields were post-processed in order to obtain kinematically based crack tip location histories throughout the loading procedure, by a purposely made algorithm. The developed...
Article
Full-text available
The mechanical behaviour of timber loaded in compression perpendicular to grain is essential for a rational design of many timber structures. Structural components frequently exposed to such loading include studs on bottom rails, stress-laminated timber decks, timber elements lying in between vertical load-bearing columns as well as traditional tim...
Article
The effects of variation in humidity coupled with long-term loading give rise to dimensional changes and creep effects in wooden elements. Many wooden products such as cross-laminated timber (CLT) plates as well as many common structural details used in timber engineering are vulnerable to variations in moisture content (MC) as well as to creep eff...
Conference Paper
WOODSOL is a research project that aims to develop a competitive and envi-ronmentally friendly structural system, suitable for mid-rise timber buildings with open and flexible architecture. The structural system consists of pre-fabricated, cassette-type, floor decks connected to continuous glulam columns. The main idea of the project is to introduc...
Conference Paper
Full-text available
ABSTRACT: Open and flexible architecture allows flexible use of buildings. A way to improve timber buildings in this direction is by introducing moment–resisting frames with rotationally stiff beam–to–column connections. In the present paper, a new concept for a beam–column moment–resisting timber connection is presented. The connection consists of...
Article
Full-text available
Long threaded rods have recently been widely used as a reinforcement of glued laminated timber in perpendicular to the grain direction. The recent research has thus focused mainly on the withdrawal properties of the threaded rods in the axial direction. Utilizing their large withdrawal stiffness and strength, the threaded rods can also effectively...
Article
Hanger arrangements suitable for timber network arch bridges with light timber decks on transverse crossbeams have been studied. The focus was on radial hanger patterns for glulam arches with circular shapes. The premise for the patterns are that the hangers always are attached in pairs to the transverse crossbeams, which are evenly distributed alo...
Article
Large spans of modern timber bridges can be achieved by use of glulam arches with network hanger configuration. Since transportation and production limit the length of timber elements, the glulam arches must be spliced on bridge site. However, it is difficult to obtain practical moment resisting on-site splicing of massive glulam elements featuring...
Article
Full-text available
An experimental investigation on withdrawal of pairs of screwed-in threaded rods embedded in glued-laminated timber elements is presented in this paper. Specimens with varying angles between the rod axis and the grain direction (α = 15°, 30°, 60°, 90°) and 2 different configurations with respect to edge distances and spacings were tested. The diame...
Article
This paper studies network arch timber bridges. The network patterns considered in the paper are suitable for bridges with a light deck on evenly spaced transverse crossbeams. Therefore, the equidistant distribution of hangers fastening points along the deck is assumed. In bridges made of steel and concrete, hangers are usually equally distributed...
Conference Paper
This paper presents a numerical material model for the withdrawal behaviour of screwed-in threaded rods embedded in wooden elements along the grain direction. Model aims to provide withdrawal stiffness assessment of one such fastener based on the real physical mechanisms occurring at the interface of two materials. Axisymmetric model is assumed and...
Article
In order to achieve larger spans of timber arch bridges, glulam massive timber sections must be spliced on-site by moment resisting and rotationally stiff joints. In this paper, a novel timber splice connection utilizing long threaded rods and grout-filled couplers is presented. Flexural characteristics of the splice joint were investigated by full...
Conference Paper
Full-text available
Axially loaded threaded rods feature high withdrawal capacity and stiffness and they can be a convenient, economical and easy-to-apply fastening system to be used in timber bridges. Bridges are subjected to repeated loading and therefore members and connections should have fatigue verification. Several studies have investigated the static propertie...
Conference Paper
Full-text available
A better knowledge of the mechanical behaviour of timber loaded in compression perpendicular to grain is essential for design of stress-laminated timber bridge decks to guarantee their proper behaviour during their whole lifetime. Several compression orthogonal to grain tests have been performed on timber. The paper presents numerical simulations o...
Conference Paper
Full-text available
Feasibility studies of glulam arches with network hanger configurations have shown possibilities to achieve large spans of timber bridges. However, the length of timber elements is limited due to production and transportation issues. Long-span arches of full-timber cross sections must thus be spliced at building site. Considering stability and buck...
Chapter
In this chapter, timber bridges are presented. In the first part the material properties are discussed and mechanical properties for timber products used in bridges are presented. The major part of the chapter is dedicated to design, structural modeling, verification procedures, and finally to design examples.
Conference Paper
Full-text available
In the present study, the influence of end grain effects on strength and deformation characteristics for structural timber joints is studied. Two series of test configurations were tested. The first configuration consisted of two timber specimens with direct contact of end fibers. In the second configuration, a steel plate was placed in between the...
Conference Paper
Full-text available
Building owners often state requirements that new buildings shall have open and flexible architecture in order to allow flexible use and future changes. A way to improve timber buildings in that direction is to increase the stiffness of the connections between horizontal and vertical members of the structural systems. This paper presents some numer...
Article
In the present paper, the withdrawal stiffness of axially loaded threaded rods screwed into timber elements is investigated using theoretical, numerical and experimental methods. The theoretical approach is based on the application of classical Volkersen theory on axially loaded connectors. An experimental investigation of withdrawal of threaded ro...
Article
Full-text available
“Treet” is a 14-storey timber apartment building in Norway currently under construction. Ground works started in April 2014, and the residents can move in autumn of 2015. The building will be one of the tallest timber buildings in the world. The building consists of load-carrying glulam trusses and two intermediate strengthened levels. Prefabricate...
Conference Paper
Full-text available
Various abiotic and biotic agents have a negative effect on the service life of materials used for bridge constructions. Corrosion of steel, carbonization of concrete and decay of timber are limiting their service lives. It is a common perception that the expected lifetime of a timber structure is only a fraction of that of a concrete or steel stru...
Conference Paper
Full-text available
There are various examples of use of moment resisting splice joints in the building industry. These are mostly placed in planar structures (frames, arches) and indoor conditions. There are fewer examples of usage for timber bridges. Introduction of moment-resisting splice joints in timber bridge engineering would allow new design possibilities and...
Conference Paper
Full-text available
Stress-laminated timber bridges are more and more used nowadays, but the knowledge about their long-term behaviour is still not sufficient. The present review shows critical details of timber bridges with regards to durability. Despite some of them are very common, there is still a need to improve their properties to limit the effects of high moist...
Conference Paper
Connections consisting of axially loaded connectors embedded in timber elements can be a strong and competitive alternative to dowel-type connections. Such connections combine high capacity and stiffness. However, especially in the case of screwed-in threaded rods, the up-to date theoretical models and available experimental results are limited. In...
Article
Full-text available
Dynamic properties of two timber floor specimens are experimentally evaluated by the impact method. Each specimen uses one specified type of connectors, either screws or nails. A numerical model is developed using constrained degrees-of-freedom for the modeling of connectors. Numerical analyses have been performed, and show good agreement with expe...
Article
Full-text available
Understanding the inherent damping mechanisms of floor vibrations has become a matter of increasing importance following the development of new composite floor layouts and increased span. The present study focuses on the evaluation of material damping in timber beam specimens with dimensions that are typical of common timber floor structures. Using...
Conference Paper
ABSTRACT: In seismic design of structures a careful balance of stiffness, strength and ductility is required in order to ensure a good structural performance in terms of damage mitigation and safety in case of minor and major seismic excitation respectively. Lateral stiffness, strength or ductility can be provided in timber structures by means of d...
Article
The present study deals with prediction of material damping in Timoshenko beams. Complex elastic moduli and complex stiffness are defined to derive an analytical model that predicts the hysteretic system damping for the whole structure. The prediction model comprises two parts, the first related to bending, and the second related to shear. Reliable...
Article
Full-text available
A semi-analytical prediction model of material damping in timber panels has been developed. The approach is derived from the strain energy method and the input is based on loss factors, which are intrinsic properties of the considered materials, together with other material properties and mode shape integrals, whose calculation can easily be implem...
Article
Glulam structures in service may exhibit considerable moisture induced stresses perpendicular to grain that may affect the load-bearing capacity. An option to enhance the low tensile strength of glulam perpendicular to grain is the use of self-tapping screws, which has shown promising results in constant climates. In varying climates, however, the...
Article
Climate variations affect timber structures by causing moisture induced stresses which may lead to cracks in timber members. The paper presents experimentally determined moisture induced stresses that arise perpendicular to the grain of glulam specimens during exposure to 1-dimensional drying and wetting. Although to a certain extent reduced by cre...
Conference Paper
A method for evaluation of robustness of beam structures is presented. The model covers the case where the floors are subjected to falling mass from failed floors above the one under consideration. The beam-like structure is transformed into an equivalent SDOF system. The method is independent of material, but where some assumptions are made, wood...
Article
Moisture-induced stresses resulting from climate variations of the environment can induce cracks in timber members and thus affect the safety and serviceability. The present study highlights—by means of numerical simulations—the distribution and development over time of moisture-induced stresses in various glulam cross sections during wetting. The...
Article
With the development of new composite floor layouts and increased spans, understanding damping mechanisms of floor vibrations has now become an important field of interest. In this study, timber beams were subjected to flexural vibrations by using the impact test method. Experimental modal analysis was used to process the damping ratio out of the f...
Article
The behavior of mid-sized self-tapping screws are considered when the inclination between grain direction and screw axis is zero and the application no longer is covered by Eurocode 5. Both experimental tests and a numerical analysis are carried out, and the results compared with state of the art analytical expressions based on the Volkerson model...
Article
The recent introduction of a common basis for structural design in Europe has led to a comprehensive set of standards covering the most used building materials. The basic principles of proper design are stated in EN 1990 and the actions are specified in EN 1991. For timber structures the governing regulations are given in EN 1995 (Eurocode 5), with...
Article
Stresses perpendicular to the grain arising from moisture changes might cause cracks and thereby severely affect the load bearing capacity and serviceability of timber structures. The present paper reviews parameters and mathematical models commonly applied for numerical simulation of moisture-induced stresses in glulam members. The basis of the ca...
Article
Full-text available
The cross laminated timber (CLT) concept has a potential to improve the performance of timber structures. Combinations of anisotropic wood material properties and the directional lay-ups of laminated structures give a high degree-of-freedom in the conceptual design of CLT. Many conditions can be taken into account in the strive for optimal performa...
Article
Glulam cantilever beams connected through a steel-plate using long threaded rods as fastener have been explored. The cantilever beam is a model of a propeller in a water turbine and must be designed for very large moment actions at the connection. Two experimental studies have been carried out, one for the withdrawal capacity of threaded rods and o...
Article
Full-text available
Wood composite products are promising materials, whose design needs to take into account all orthotropic properties for wood. The objective of this study is to demonstrate the influence of the annual rings patterns on the mechanical properties of wood and to compare two different methods to model them. In the first part, analytical derivation of ef...
Article
Shear properties of clear softwood from Norway spruce were investigated by means of the Arcan shear test. The test enabled fairly detailed measurements of pure shear until failure in each of the three orthotropic shear planes, where video extensometry was used for strain measurements. A total number of 85 specimens were tested in 6 different config...
Article
Determination of material parameters from experimental tests often rely on simplifying assumptions like the existence of uniform stress and strain fields within the considered part of the test specimen. However, more detailed analyses usually show that the stress and strain fields differ from the assumed (nominal) uniform distributions. In order to...
Article
The shear test described by Arcan was used to investigate orthotropic shear properties of clear softwood from Norway spruce. The test was chosen on the basis of a thorough literature study, although the experimental setup was somewhat modified compared to the original. A total number of 85 specimens were tested for loading and unloading in 6 differ...
Article
Wood specimens have been tested for compressive loading in the longitudinal direction. Planar deformation was recorded by means of video extensometry on the specimen surfaces. A post processing routine was developed to calculate stress and strain values from the sampled data. The routine made use of mathematical framework used in the finite element...
Article
The increased use of large span glulam timber structures is in part due to the development of more efficient connections with slotted-in steel gusset plates combined with steel dowels. In timber road bridges, also the fatigue behaviour of such connections must be considered. The paper shows that fatigue damage and failure may occur in timber struct...
Article
This paper describes an experimental, analytical and numerical investigation of the penetration and perforation of circular Weldox 460 E steel plates with different thicknesses struck by a blunt projectile at various impact velocities. In the experimental tests, a compressed gas gun was used to launch the sabot mounted projectile at impact velociti...
Article
Uniaxial tensile tests have been conducted for the commercial aluminium alloy AA7108 in different tempers. In addition, pure bending tests were performed for temper W (20min). The influence of heat-treatment on plastic anisotropy in strength, plastic flow and strain hardening has been investigated by performing tests with three loading directions w...
Article
Projectiles with three different nose shapes (blunt, hemispherical and conical) have been used in gas gun experiments to penetrate 12 mm thick Weldox 460 E steel plates. Based on the experimental results, the residual velocity curves of the target material were constructed and compared. It was found that the nose shape of the projectile significant...
Article
A continuum damage mechanics model coupled with an element erosion algorithm was adopted to simulate large mass, low velocity impact on 5 mm thin aluminium alloy plates. A hemispherical ended projectile with a mass of 55 kg impacted the target in the span between the stiffeners, i.e. at the location of the weld. The material model used is available...
Article
An experimental device has been developed for the quasi-static testing of panels exposed to equally distributed pressure loading. This test equipment uses water as the pressure medium and may be operated in several ways. The test facility is described and various operational aspects are discussed. Emphasis has been put on similarity in experimental...
Article
Slotted-in steel plates with dowels is the favoured type of joints for timber bridges in Norway today due to its advantages compared to other jointing methods. However, the documentation of the fatigue behaviour is insufficient. In this paper a brief technical presentation of a project on fatigue behaviour is given. The ultimate load of the connect...
Article
A literature study of explosion estimation reports from the Flixborough accident was performed and commented. The results from this survey were compared to the results obtained from explosion simulations. The simulations were done with a computer model of the Flixborough plant using the EXSIM software simulation tool. The comparison showed that exp...
Article
This paper presents a research programme in progress where the main objective is to study the behaviour of Weldox 460 E steel plates impacted by blunt-nosed cylindrical projectiles in the lower ordnance velocity regime. A compressed gas gun is used to carry out high-precision tests, and a digital high-speed camera system is used to photograph the p...
Article
Gas explosion simulators are often used as tools in process plant design. This article presents some properties of gas explosions found using the EXSIM simulation software on three offshore modules with a total of nearly 10,000 simulations. The selected results are chosen for their supposed applicability to structural design in the process industri...
Article
A method for calibration of anisotropic yield criteria based on yield stresses obtained in tensile and bending tests is developed. It is thus possible to calibrate anisotropic criteria by means of simple tests without using the R-ratios in combination with the associated flow rule. Explicit formulas are derived for the calibration of Hill's yield c...
Article
There are several sources for possible errors when numerical gas explosion simulators are applied to estimate loads on structures and equipment. The present paper proposes a partial coefficient method to deal with uncertainties that arises from variations of the location of the ignition source, and the lack of knowledge of size and location of the...

Projects

Projects (6)
Project
The project's goal is to quantify the structural damping in as-built tall timber buildings (TTB), identify and quantify the effects of connections and non-structural elements on the stiffness, damping and wind-induced dynamic response of TTBs, develop a bottom-up numerical finite element model for estimating the dynamic response of multi-storey timber buildings, validate the predicted response with in-situ measurements on TTBs and disseminate findings via a TTB Design Guideline for design practitioners. The project is supported under the umbrella of ERA-NET Cofund ForestValue. Project coordinator: RISE Research Institute of Sweden Project partners: - NTNU Norwegian University of Science and Technology (Norway) - University of Exeter (UK) - University of Ljubljana (Slovenia) - InnoRenew CoE (Slovenia) - CSTB Centre Scientifique et Technique du Bâtiment (France) - Linnaeus University (Sweden) - Moelven Töreboda AB (Sweden) - Moelven Limtre AS (Norway) - SWECO Norge AS avd Lillehammer (Norway) - Smith and Wallwork Engineers Ltd (UK) - GALEO (France) - EIFFAGE (France) - ARBONIS (France)