Multi-storey Timber Research Articles

Experimental Verification of Design Procedure for Elements from Cross-laminated Timber

Cross-laminated timber is widely used for load-bearing walls and panels of multi-storey timber buildings as well as for decking structure of pedestrian and road bridges. Design procedure for elements from cross-laminated timber was considered and validated by the experiment and FEM. The design procedure is based on the transformed section method. Eight cross-laminated timber panels with span equal to 1.8 m were experimentally checked under the action of static load. The difference between the experimentally and analytically obtained results is within the limits from 3.3 up to 20%.

Europe Goes Green

At the UN-Paris conference in 2015 countries accepted the challenge to fight Green House Gas emissions (GHG) during the next decades in an attempt to stop global warming. In Europe the aim is that all future new buildings aim at nearly zero-energy consumption and be highly material efficient whilst the existing building stock will be refurbished at a rate of 2% annually. Numerous international scientific studies have found that timber-framed buildings result in lower GHG emissions than their steel and concrete counterparts. For green building construction (relative) new timber products and connection methods conquer the market such as Cross Laminated Timber products. CLT products allow fast and cost effective execution of the building while structural limitations and disadvantages of the traditional timber frame construction are overcome. Examples of multi-storey timber structures are presented. These steps forward were ministered by the development of innovative timber fastener connections like self-tapping screws and reinforced dvw tube connections.

Rotational Behavior of Bolted Glulam Beam-to-Column Connections Reinforced with Section Steel

Bolted connections with slotted-in steel plates are commonly used to connect beams and columns in heavy timber structures. While due to the low tensile strength of wood in the perpendicular-to-grain direction, these connections are usually not able to present satisfying rotational performance. In order to solve this problem, a relatively new type of bolted connection, reinforced with section steel, was designed and tested in this paper. Two groups of total six specimens were tested under monotonic loading to investigate their rotational behavior. Tests showed that the brittle failure mode of wood splitting in the perpendicular-to-grain direction was fully restrained. Only slight cracks were observed in most specimens, except one that underwent bending failure in the beam member. Test results indicated an average increase of 78.7% in moment resistance and a 54.8% increase in ductility ratio for middle-storey connections, compared with conventional connections simply using slotted-in steel plates. Top-storey connections, without previous test results as comparison, also presented high moment-bearing capacity and reliable deformability. As a result, such connection may receive a broad application, especially in multi-storey heavy timber structures.

NMIT Arts & Media Building—Innovative structural design of a three storey post-tensioned timber building

The NMIT Arts & Media Building in Nelson, New Zealand is the first in a new generation of multi-storey timber structures. It employs a number of innovative timber technologies including an advanced damage avoidance earthquake design that is a world first for a timber building. Aurecon structural engineers are the first to use this revolutionary Pres-Lam technology developed at the University of Canterbury.This technology marks a fundamental change in design philosophy. Conventional seismic design of multi-storey structures typically depends on member ductility and the acceptance of a certain amount of damage to beams, columns or walls. The NMIT seismic system relies on pairs of coupled timber shear walls that incorporate high strength steel tendons post-tensioned through a central duct. The walls are centrally fixed allowing them to rock during a seismic event. A series of U-shaped steel plates placed between the walls form a coupling mechanism, and act as dissipaters to absorb seismic energy. The design allows the primary structure to remain essentially undamaged in a major earthquake while readily replaceable connections act as plastic fuses.With a key focus on sustainability the extensive use of timber and engineered-wood products such as laminated veneer lumber (LVL) makes use of a local natural resource, all grown and manufactured within an 80km radius of Nelson.This IstructE award winning project demonstrates that there are now cost effective, sustainable and innovative solutions for multi-storey timber buildings with potential applications for building owners in seismic areas around the world.

Horizontal Stabilisation of Sheathed Timber Frame Structures Using Plastic Design Methods – Introducing a Handbook Part 1: Design Principles for Horizontal Stabilisation

The authors have developed a plastic design method for sheathed timber frame shear walls. It has been presented and discussed for inclusion in Eurocode 5 and a Swedish handbook has been presented. In the plastic method, you can choose to transfer the anchoring force via the leading stud to the substrate, corresponding to a fully anchored shear wall (no uplift of studs), but you can also choose to utilize the sheathings to transfer the tensile force via the sheathing-to-framing joints to the substrate by anchoring the bottom rail, corresponding to a partially anchored shear wall (studs experience uplift). By the plastic method several alternatives for anchoring the wall are possible and they can also be combined in such a way that each of them take a portion of the uplifting force, e.g. through a simple tying down device, through the sheathing-to-framing joints and through anchoring of the shear wall to the transverse wall. The method also makes it possible to include the load-bearing capacity of wall segments including openings. The handbook treats primarily shear walls, but for the sake of completeness some aspects of the roof and floor diaphragms are also discussed. The interior force distribution in sheathed timber frame walls weak in shear is discussed, as are the fundamental difference between the effect of vertical loads on the stabilisation of walls which are rigid or weak in shear, and how the plastic design method is applied to multi-storey timber buildings.

Seismic performance of timber buildings: the Series project

This paper describes a shaking-table experimental programme performed on four different multi-storey timber houses within the transnational Seismic Engineering Research Infrastructures for European Synergies (Series) project at the National Laboratory of Civil Engineering in Lisbon, Portugal. The aim of the Series project was to promote cooperation between main European research centres by giving access to their facilities. Under the timber buildings research programme within the Series framework, four real-scale three-storey buildings of plan dimension 7 × 5 m were assembled and tested: two timber-frame houses, one log house and one cross-glued laminated timber house. This paper describes the common parts of the various tests undertaken, such as the test set-up and the measurement layout. The tests themselves are described in a series of companion papers by the authors.

Comparison of multi-storey cross-laminated timber and timber frame buildings by in situ modal analysis

The dynamic properties of two common structural systems for multi-storey timber buildings are compared through in situ testing of completed buildings. The two five-storey buildings examined are identical except for their structural system, which in one is sheathed stud-and-rail timber construction, and in the other a cross-laminated timber panel system. Both also have a reinforced-concrete core located at the centre of one edge of the rectangular plan of each building. An output-only modal analysis method was used to identify the modal properties of the buildings: the random decrement technique was applied to the stochastic measured response, and then the time-domain random decrement signature was used for modal analysis by the Ibrahim Time Domain method. The natural frequencies, damping ratios and mode shapes of the first three vibration modes of the buildings were identified, and compared with those modelled based on the properties of the core and timber walls. The variations in properties between the two buildings are discussed. The two structures show very similar natural frequencies and damping ratios, suggesting that they could perhaps be considered as the same class of building in design for lateral movement.

Design Methods for Load-bearing Elements from Crosslaminated Timber

Cross-laminated timber is an environmentally friendly material, which possesses a decreased level of anisotropy in comparison with the solid and glued timber. Cross-laminated timber could be used for load-bearing walls and slabs of multi-storey timber buildings as well as decking structures of pedestrian and road bridges. Design methods of cross-laminated timber elements subjected to bending and compression with bending were considered. The presented methods were experimentally validated and verified by FEM. Two cross-laminated timber slabs were tested at the action of static load. Pine wood was chosen as a board's material. Freely supported beam with the span equal to 1.9 m, which was loaded by the uniformly distributed load, was a design scheme of the considered plates. The width of the plates was equal to 1 m. The considered cross-laminated timber plates were analysed by FEM method. The comparison of stresses acting in the edge fibres of the plate and the maximum vertical displacements shows that both considered methods can be used for engineering calculations. The difference between the results obtained experimentally and analytically is within the limits from 2 to 31%. The difference in results obtained by effective strength and stiffness and transformed sections methods was not significant.

Performance-based and damage assessment of SFRP retrofitted multi-storey timber buildings

Performance-based and damage assessment of SFRP retrofitted multi-storey timber buildings

Conflict and Compromise in multi-storey timber architecture

From the Stone Age to the Silicon Age, humanity’s relationship with materials has framed our scientific and cultural evolution. Despite recent scientific advances that open the laboratory doors to a future of material experimentation, the building industry remains stuck in the Concrete Age. The next material age is likely to be a Timber Age, as engineered timber finally comes into its own as a structural material suitable for multi-storey buildings.The research and design methodology of our practice can be summarised as an essay in conflict and compromise; a continual infliction of self-imposed constraints that allows us to discover hitherto unimaginable paths through the available options. We achieve this by searching through a space of possibilities demarcated by the properties and performative logic of the material at hand. First, we create an abundant field of alternatives, then we often use evolutionary computations to find our way through this field towards a visionary and original design.All design involves conflicting objectives. The best schemes offer the best compromise between desires. This article discusses how evolutionary solvers can be used as a tool for material-based architectural optimisation of geometries and structures, and how we have used them in designs for the imminent Timber Age. As one potentially conflicting objective is weighed against another, we move closer and closer to a tradeoff: the fitness of cooperating, opposing or unconnected variables.A population of possible design responses is visualised as a ‘fitness landscape’. Inspired by the role of natural selection in biological evolution, we use evolutionary algorithms to perform a selection process in which the ‘most fit’ members of such a population survive, while the ‘least fit’ members are eliminated, with the selection process guiding the algorithm towards ever-better solutions. The resulting timber structures would have made Darwin proud.

Tests on glulam–CLT shear connections with double-sided punched metal plate fasteners and inclined screws

A new shear connection system was tested in order to be used in off-site manufactured cassette floor elements made with glulam beams and cross laminated timber (CLT) panels. This type of floor element can present advantages from weight, structural and assembly point of view in multi-storey timber construction. The shear connection proposed is made of double-sided punched metal plate fasteners, connecting CLT and glulam members to form a T-cross-section. Inclined screws are used in combination with the double-sided nail plates to secure the shear connection. Shear test results are presented and compared with a simple calculation model for estimating the mean load-carrying capacity and stiffness of the combined joint according to methods available in the literature.

Lifecycle carbon implications of conventional and low-energy multi-storey timber building systems

A consequential-based lifecycle approach is used here to explore the carbon implications of conventional and low-energy versions of three timber multi-storey building systems. The building systems are made of massive wood using cross laminated timber (CLT) elements; beam-and-column using glulam and laminated veneer lumber (LVL) elements; and prefabricated modules using light-frame volume elements. The analysis encompasses the entire resource chains during the lifecycle of the buildings, and tracks the flows of carbon from fossil energy, industrial process reactions, changes in carbon stocks in materials, and potential avoided fossil emissions from substitution of fossil energy by woody residues. The results show that the low-energy version of the CLT building gives the lowest lifecycle carbon emission while the conventional version of the beam-and-column building gives the highest lifecycle emission. Compared to the conventional designs, the low-energy designs reduce the total carbon emissions (excluding from tap water heating and household and facility electricity) by 9%, 8% and 9% for the CLT, beam-and-column and modular systems, respectively, for a 50-year lifespan located in Växjö. The relative significance of the construction materials to the fossil carbon emission varies for the different energy-efficiency levels of the buildings, with insulation dominating for the low-energy houses and plasterboard dominating for the conventional houses.

Modelling The Fire Performance of Structural Timber-Concrete Composite Floors

This paper describes numerical modelling to predict the fire resistance of engineered timber-concrete composite floor systems. The paper describes 3D numerical modelling of the floor systems using finite element software, carried out as a sequential thermo-mechanical analysis. Experimental testing of these floor assemblies has also been undertaken to validate the models, with multiple full scale tests conducted to determine the failure mechanisms and assess fire damage to the system components. The final outcome of this research is the development of simplified design methods for calculating the fire resistance of a wide range of engineered timber floor systems, as part of a larger research project on multi-storey timber buildings.

Multi-storey timber construction and bioeconomy – barriers and opportunities

Multi-storey timber construction has been developed and promoted in Finland since the 1990s. Despite these efforts, the share of timber frames in multi-storey construction has remained very low. Construction business is also very resource intensive and accounts for a large share of greenhouse gas emissions. Increasing the use of renewable materials, mainly wood, in buildings, could make construction more sustainable and a part of bioeconomy. This study aimed at identifying barriers to the adoption of multi-storey timber construction, ways in which wood could compete with established solutions and possibilities for partly integrating construction into bioeconomy. Based on 18 interviews of representatives from the entire value chain, this study presents insights into introducing new solutions into a conservative field. Our results indicate that multi-storey timber construction could offer competitive solutions for more sustainable construction, even though barriers to its adoption still exist.

Behaviour of post-tensioned timber columns under bi-directional seismic loading

Moment-resisting frames made of laminated veneer lumber (LVL) in combination with unbonded post-tensioning have recently been proposed for multi-storey timber buildings. Prefabricated and post-tensioned timber frames can be designed to have enhanced re-centering and energy dissipation after seismic loading. The unbonded post-tensioning provides re-centering capacity while energy is dissipated through the addition of special dissipating devices which also act as external reinforcing.
 As part of a research program on multi-storey timber structures, this paper describes experimental and analytical studies to investigate the behaviour of post-tensioned LVL columns under uni-and bi-directional seismic loading. The results show excellent seismic performance, characterized by negligible damage of the structural members and small residual deformations, even under the combined effect of loading in two directions. Energy is dissipated mostly through yielding of external mild steel dissipaters connecting the column and the foundation, which can be easily removed and replaced after an earthquake. Since post-tensioning can be economically performed on site, the system can be easily implemented for either column-to-foundation connections in multi-storey timber buildings as well as for pier-to-foundation and/or pier-to-deck connections in timber bridges.

Subjective and Objective Evaluation of Impact Noise Sources in Wooden Buildings

Multi-storey timber buildings up to 6 and more floors are increasingly built in many European countries. The challenge with these buildings can be that with traditional intermediate floor constructions in timber it can be difficult to fulfill the standard requirements and even when they are met, low frequency transmission can still cause complaints. Additionally it is difficult to develop appropriate light weight floor constructions since it is well known that the correlation between the standardized evaluation methods using the tapping machine and the human perception of impact noise can be poor, especially in buildings with light weight structures. In the AcuWood project, measurements and recordings on different intermediate timber floor constructions in the laboratory and the field were performed covering a wide range of modern intermediate timber floor constructions. Additionally, one intermediate concrete floor with different floor coverings was included in the study. Besides the standardized tapping machine, the modified tapping machine and the Japanese rubber ball and “real” sources were employed. Subjective ratings from listening tests were correlated to many technical single number descriptors including the standardized descriptors and non-standardized proposals. It was found that the Japanese rubber ball represents walking noise in its characteristics and spectrum best, taking into account the practical requirement of a strong enough excitation for building measurements. The standardized tapping machine, with an appropriate single number descriptor, L′nT,w + CI,50-2500 or slightly better, L′nT,w Hagberg 03, leads also to an acceptably high determination coefficient between the descriptor and the subjective ratings. Additionally, the study delivered data, from which proposals for requirements for the suggested single number ratings are deduced, based on the subjective ratings.

Seismic Analysis of a 2-Storey Log House

The current paper deals with the analysis of the results yielded by a series of tests performed to evaluate the seismic behaviour of a model log construction. The study was based on an experimental investigation performed to improve the existing knowledge on log houses subject to seismic events. The main part of the experimental work is based on a full scale shaking table test, conducted on a two-storey log house designed by the Portuguese company Rusticasa® in compliance with design rules for timber buildings. The test was performed by the University of Minho within the framework of the SERIES Project Multi-storey timber buildings and was coordinated by the University of Trento, at LNEC, Lisbon, Portugal. The geometry of the specimen, the design of the test, the setup and the instrumentation layout are first presented in this paper. The test procedure was conducted in stages with maximum accelerations (bi-directional) of 0.07g, 0.28g and 0.5g. During this incremental test procedure, whenever damage occurred, identification tests were performed to assess any variation in the fundamental period of the house. The experimental results of each test have been analyzed and the resultant values of inter-storey drift, wall slippage and uplift measurements, shear deformations and hold-down forces measured are presented. Most importantly, the dynamic properties (fundamental period and mode shapes) of the system have been determined.

Prefabricated timber walls anchored with glued-in rod connections: racking tests and preliminary design

A new beam and post system for multi-storey timber buildings has been developed in Sweden. The building is braced with timber walls constructed from two Kerto-Q LVL boards glued and screwed onto a glulam frame. The walls are prefabricated off-site and can be connected to the foundation using either glued-in steel rods with metric thread or nail plates. Introductory racking tests of full scale walls anchored with glued-in threaded rods were performed. The paper presents the results of the experiments and discusses the use of the transformed section method to predict racking capacity of the anchored wall. To evaluate the strength of the glued-in rods, a newly proposed model was employed. An analytical study was conducted to investigate the role of the sheathing and the contribution of the axial force on the racking capacity of the walls. The wall panels tested in this experimental programme showed high strength and stiffness under racking load. The anchoring joints with glued-in steel rods with metric thread demonstrated a high load-carrying capacity with, however, large scatter and a brittle failure mode characterized by pull-out from the timber member. The transformed section method was successfully used to predict the racking capacity of timber walls anchored with glued-in steel rods.

Acoustic Properties of Timber Joist Ceilings with Respects to their Response onto the Effects of Dynamic Loads

The paper discusses some issues connected to timber joist ceilings found not only in historical protected buildings but also in newly designed multi-storey timber based ones, with regards to their acoustic parameters perceived by the inhabitants of such objects. These problems are usually connected to the complaints of the users because of unsatisfying acoustic conditions indoors, observed mainly at low frequencies, even though the requirements given by the legislation are met. The paper with its content is a reaction to the contradiction between the results coming from measurements and subjective perception, and is complemented by structural evaluations seeking the effects of dynamic tremors and vibrations.

Study on the Structural and Aseismatical Performance of Multi-Storey Ancient Chinese Timber Structure Shangyou Tower of Palace Style

Based on the rich previous experimental data, the multi-storey ancient Chinese timber structure shangyou tower of palace style was studied. ANSYS10.0 software was used to establish the finite element models. One finite element model of large wooden frame was established by applying semi-rigid spring element to simulate the joint of mortise-tenon, tou-kung and the connection on column foot in the real wooden structure. The other finite element model of antique building corresponding to the finite element model above was established. The first 10 inherent frequencies and vibrations of the two models were obtained by the method of Block Lanczos with full transient analysis. The model displacement and acceleration time history curves were obtained by taking the two models subjected to El-Centro ground motion, Taft ground motion and Lanzhou artificial ground motion excitation. By the results analysis of the two models, it can be find that the vibration isolation performance of the ancient Chinese timber structure mainly manifests in the column foot, tenon and mortise connection and the tou-kung layer.