Research

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27 pages, 4625 KiB

Open AccessArticle

Guidelines for a Finite Element Based Design of Timber Structures and Their Exemplary Application on Modelling of Beech LVL

by Janusch Töpler, Lea Buchholz, Julian Lukas and Ulrike Kuhlmann

Buildings 2023, 13(2), 393; https://doi.org/10.3390/buildings13020393 - 01 Feb 2023

Cited by 1 | Viewed by 2378

Abstract

Design verifications of buildings are usually carried out supported by a finite element analysis (FEA), for which, however, there are only a few and almost exclusively non-binding application rules. Within the Cluster of Excellence Integrative Computational Design and Construction for Architecture (IntCDC) at [...] Read more.

Design verifications of buildings are usually carried out supported by a finite element analysis (FEA), for which, however, there are only a few and almost exclusively non-binding application rules. Within the Cluster of Excellence Integrative Computational Design and Construction for Architecture (IntCDC) at the University of Stuttgart, Guidelines for a Finite Element-Based Design of Timber Structures have been developed. The scope of the guidelines is daily engineering practice, expert engineering applications and product development and certification. Essential parts of the guidelines are design procedures, modelling (including geometrical, material and imperfection modelling), analysis, model verification and validation and design. The content and application of the guidelines are described and illustrated in this paper using two benchmarks. These two benchmarks, which are based on experimental investigations, deal with the elastic material modelling of glulam made of beech laminated veneer lumber (beech LVL) and dowel-type connections for beech LVL members. The experimental basis of the benchmarks is described. With the experiments for the benchmarks, all Poisson’s ratios and the complete elastic material stiffness matrix of beech LVL are determined by means of an optical measuring system. The experimentally determined stiffnesses of the investigated dowel-type connections in beech LVL are compared with normative values. Based on the experiments, a numerical model is developed in RFEM (Dlubal). Full article

(This article belongs to the Special Issue Timber Structures: Latest Developments, Challenges, and Perspectives)

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32 pages, 4194 KiB

Open AccessArticle

Social Representations of Mass Timber and Prefabricated Light-Frame Wood Construction for Multi-Story Housing: The Vision of Users in Quebec

by Baptiste Giorgio, Pierre Blanchet and Aline Barlet

Buildings 2022, 12(12), 2073; https://doi.org/10.3390/buildings12122073 - 26 Nov 2022

Cited by 1 | Viewed by 2791

Abstract

The increased use of wood and prefabrication are solutions that are helping to address current and future challenges in the construction sector. However, these practices are slow to become widespread due to the conservative nature of this industry. The objective of this study [...] Read more.

The increased use of wood and prefabrication are solutions that are helping to address current and future challenges in the construction sector. However, these practices are slow to become widespread due to the conservative nature of this industry. The objective of this study is to characterize the social representations of Province of Quebec (Canada) individuals with regard to these construction methods in order to determine the motivations and barriers to their use in the construction of multi-story housing. The social representations of a representative panel of the Quebec population were collected through standardized surveys. The data were analyzed using descriptive statistics. The results indicate that the use of wood in the construction of high-rise multi-story housing is not part of the representations of a majority of Quebecers. The motivations identified are the aesthetics of wood and the environmental aspect, although forestry exploitation remains an important concern for respondents. The main barriers are the safety aspect and lifespan because they tend to dominate the other themes in decision making. The results suggest that the acceptance and adoption of these construction methods by users can be improved by adapting the transfer of knowledge towards the negatively perceived themes and the identified social groups. Full article

(This article belongs to the Special Issue Timber Structures: Latest Developments, Challenges, and Perspectives)

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20 pages, 14728 KiB

Open AccessArticle

The Geometry of Timber Lamella Vaults: Prototype Analysis

by Milica Petrović, Isidora Ilić, Svetislav Mijatović and Nenad Šekularac

Buildings 2022, 12(10), 1653; https://doi.org/10.3390/buildings12101653 - 11 Oct 2022

Cited by 2 | Viewed by 3307

Abstract

This paper presents timber lamella structures applied to the circular cylinder surface when all lamellae axes intersect at the nodes. To achieve the uniformity of all elements in this structure, the geometry of the structure must be carefully designed. The main methods for [...] Read more.

This paper presents timber lamella structures applied to the circular cylinder surface when all lamellae axes intersect at the nodes. To achieve the uniformity of all elements in this structure, the geometry of the structure must be carefully designed. The main methods for the research are graphical and numerical methods for geometric design and a prototype construction for a specific geometric pattern. The methods are discussed for their ease of replication, as well as the possibility of reinterpretation on other surfaces, while the prototype design and construction give insight into the process from design to execution. The combination of these methods allows for a thorough analysis of the geometry for lamella structures. The analysis shows that geometrical design must begin from the whole to the lamella, and that the number of element types in the structure depends on the disposition of the elements and the angle of the pattern. The discussion shows the advantages and limitations of the proposed methods, while the conclusions give the guidelines for the implementation of lamella structures into new design projects. Full article

(This article belongs to the Special Issue Timber Structures: Latest Developments, Challenges, and Perspectives)

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40 pages, 16904 KiB

Open AccessArticle

Probabilistic Models for the Tensile Properties of Split Boards and Their Application for the Prediction of Bending Properties of Engineered Timber Products Made of Norway Spruce

by Raimund Sieder and Reinhard Brandner

Buildings 2022, 12(8), 1143; https://doi.org/10.3390/buildings12081143 - 01 Aug 2022

Viewed by 1375

Abstract

The main strength and elastic properties of structural timber products, such as glued laminated timber (glulam; GLT) and cross-laminated timber (CLT), are usually described via load-bearing models, which use the tensile properties parallel to the grain of the base material boards and finger [...] Read more.

The main strength and elastic properties of structural timber products, such as glued laminated timber (glulam; GLT) and cross-laminated timber (CLT), are usually described via load-bearing models, which use the tensile properties parallel to the grain of the base material boards and finger joints as input parameters. These load-bearing models assume that the strength-graded boards will retain their full dimensions in the final product. In some applications or use cases, however, the structural timber products are split lengthwise, e.g., split/resawn glulam, or comprise a random share of in width randomly lengthwise split lamellas. As a result of splitting, the material properties assigned to these boards during the grading process in their full cross-sections are no longer valid. Examples of such structural timber products are the novel flex_GLT-beams which are cut out from large dimensional multi-laminated timber panels. In the following paper, the bending properties and system effects of resawn glulam and flex_GLT-beams are described by means of a 3D stochastic-numerical beam model that uses probabilistic models to create the input values for unsplit and split boards as well as finger joints. The models are successfully validated by our own tests and tests from literature and applied in numerous parameter studies. Full article

(This article belongs to the Special Issue Timber Structures: Latest Developments, Challenges, and Perspectives)

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22 pages, 26397 KiB

Open AccessArticle

Experimental Investigation of Cross Laminated Timber Elements with Holes or Notches at In-Plane Beam Loading Conditions

by Mario Jeleč, Domagoj Damjanović, Damir Varevac and Vlatka Rajčić

Buildings 2022, 12(7), 967; https://doi.org/10.3390/buildings12070967 - 07 Jul 2022

Cited by 1 | Viewed by 1399

Abstract

Environmental and urbanisation challenges have encouraged steady growth of mass timber structures where cross laminated timber (CLT) stands out in applications as full-size wall, floor, or beam elements. Beam elements are used mainly in situations where cross layers have a reinforcing effect on [...] Read more.

Environmental and urbanisation challenges have encouraged steady growth of mass timber structures where cross laminated timber (CLT) stands out in applications as full-size wall, floor, or beam elements. Beam elements are used mainly in situations where cross layers have a reinforcing effect on the tensile stress perpendicular to the beam axis, such as when introducing holes or notches, which is common practice in beams, due to engineering, installation, or architectural requirements. This paper presents experimental investigations of CLT beams with holes or notches for comparison and validation of an analytical model provided in the literature. Different sizes of holes and notches as well as different placements of the holes were considered in the experiments. All relevant failure modes were analysed and discussed in detail. Two predominant failure modes were indicated, i.e., bending failure and shear failure in crossing areas (mode III). Results further indicate that reduced lamination widths near the hole, notch, or element edges have a relatively small influence on the beam strength. Parametric studies indicate net shear failure (mode II) and tensile failure perpendicular to the beam axis as the critical failure modes in most of the considered cases, indicating their strong underestimation in design verifications according to the analytical model. Full article

(This article belongs to the Special Issue Timber Structures: Latest Developments, Challenges, and Perspectives)

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42 pages, 12714 KiB

Open AccessFeature PaperArticle

Advanced Timber Construction Industry: A Review of 350 Multi-Storey Timber Projects from 2000–2021

by Hana Svatoš-Ražnjević, Luis Orozco and Achim Menges

Buildings 2022, 12(4), 404; https://doi.org/10.3390/buildings12040404 - 25 Mar 2022

Cited by 51 | Viewed by 10254

Abstract

Throughout the last two decades the timber building sector has experienced a steady growth in multi-storey construction. Although there has been a growing number of research focused on trends, benefits, and disadvantages in timber construction from various technical perspectives, so far there is [...] Read more.

Throughout the last two decades the timber building sector has experienced a steady growth in multi-storey construction. Although there has been a growing number of research focused on trends, benefits, and disadvantages in timber construction from various technical perspectives, so far there is no extensive literature on the trajectory of emerging architectural typologies. This paper presents an examination of architectural variety and spatial possibilities in current serial and modular multi-storey timber construction. It aims to draw a parallel between architectural characteristics and their relation to structural systems in timber. The research draws from a collection of 350 contemporary multi-storey timber building projects between 2000 and 2021. It consists of 300 built projects, 12 projects currently in construction, and 38 design proposals. The survey consists of quantitative and qualitative project data, as well as classification of the structural system, material, program, massing, and spatial organization of the projects. It then compares the different structural and design aspects to achieve a comprehensive overview of possibilities in timber construction. The outcome is an identification of the range of morphologies and a better understanding of the design space in current serial and modular multi-storey mass timber construction. Full article

(This article belongs to the Special Issue Timber Structures: Latest Developments, Challenges, and Perspectives)

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15 pages, 806 KiB

Open AccessArticle

Development of Creep Deformations during Service Life: A Comparison of CLT and TCC Floor Constructions

by Eva Binder, Wit Derkowski and Thomas K. Bader

Buildings 2022, 12(2), 239; https://doi.org/10.3390/buildings12020239 - 19 Feb 2022

Cited by 4 | Viewed by 2259

Abstract

Cross-laminated timber (CLT) slabs in residential buildings need additional weight, e.g., in the form of screeds or gravel layers, to fulfill the criterion for the highest impact-sound class. The additional mass is, however, not exploited for the load bearing behavior, but adds additional [...] Read more.

Cross-laminated timber (CLT) slabs in residential buildings need additional weight, e.g., in the form of screeds or gravel layers, to fulfill the criterion for the highest impact-sound class. The additional mass is, however, not exploited for the load bearing behavior, but adds additional weight and leads to an increased height of the floor construction. In this study, such a CLT floor construction with a construction height of 380 mm is compared with a composite slab consisting of a CLT plate with a concrete layer on top with a floor construction height of 330 mm. The timber concrete composite (TCC) slab has a different creep behavior than the CLT slab. Thus, the development of the time-dependent deflections over the service life are of interest. A straightforward hybrid approach is developed, which exploits advanced multiscale-based material models for the individual composite layers and a standardized structural analysis method for the structural slab to model its linear creep behavior. The introduced approach allows to investigate load redistribution between the layers of the composite structure and the evolution of the deflection of the slab during the service life. The investigated slab types show a similar deflection after 50 years, while the development of the deflections over time are different. The CLT slab has a smaller overall stiffness at the beginning but a smaller decrease in stiffness over time than the investigated TCC slab. Full article

(This article belongs to the Special Issue Timber Structures: Latest Developments, Challenges, and Perspectives)

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37 pages, 5397 KiB

Open AccessArticle

Out-of-Plane Tensile Properties of Cross Laminated Timber (CLT)

by Reinhard Brandner and Lukas Jantscher

Buildings 2022, 12(2), 135; https://doi.org/10.3390/buildings12020135 - 27 Jan 2022

Cited by 4 | Viewed by 2755

Abstract

A systematic investigation is still lacking for tension out-of-plane in cross laminated timber (CLT), as a planar timber construction product. The objectives of the present study are the determination of the tensile properties of CLT made of Norway spruce, the identification of essential [...] Read more.

A systematic investigation is still lacking for tension out-of-plane in cross laminated timber (CLT), as a planar timber construction product. The objectives of the present study are the determination of the tensile properties of CLT made of Norway spruce, the identification of essential product-specific influencing parameters and a comparative analysis with glulam. For this purpose, seven test series were defined, which allowed the determination of the tensile properties on board segments and thereof produced glulam and CLT specimens by varying the number of layers, layer orientation and number of elements within a layer. The orthogonal laminated structure of CLT led to between 50% and 70% higher tensile properties out-of-plane, which is explained by the different stress distribution compared to glulam; the regulation of 30% higher properties than for glulam is suggested. In addition, the lognormal distribution turned out to be a more representative distribution model for characterizing the tensile strength out-of-plane than the Weibull distribution. This was also confirmed with regard to the investigated serial and parallel system effects, in which a clearly more homogeneous behavior was found in CLT compared to glulam, which in turn can be attributed again to the different stress distributions. Full article

(This article belongs to the Special Issue Timber Structures: Latest Developments, Challenges, and Perspectives)

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26 pages, 2423 KiB

Open AccessArticle

A Numerical Study of the Stiffness and Strength of Cross-Laminated Timber Wall-to-Floor Connections under Compression Perpendicular to the Grain

by Shaheda T. Akter, Michael Schweigler, Erik Serrano and Thomas K. Bader

Buildings 2021, 11(10), 442; https://doi.org/10.3390/buildings11100442 - 28 Sep 2021

Cited by 5 | Viewed by 3279

Abstract

The use of cross-laminated timber (CLT) in multi-story buildings is increasing due to the potential of wood to reduce green house gas emissions and the high load-bearing capacity of CLT. Compression perpendicular to the grain (CPG) in CLT is an important design aspect, [...] Read more.

The use of cross-laminated timber (CLT) in multi-story buildings is increasing due to the potential of wood to reduce green house gas emissions and the high load-bearing capacity of CLT. Compression perpendicular to the grain (CPG) in CLT is an important design aspect, especially in multi-storied platform-type CLT buildings, where CPG stress develops in CLT floors due to loads from the roof or from upper floors. Here, CPG of CLT wall-to-floor connections are studied by means of finite element modeling with elasto-plastic material behavior based on a previously validated Quadratic multi-surface (QMS) failure criterion. Model predictions were first compared with experiments on CLT connections, before the model was used in a parameter study, to investigate the influence of wall and floor thicknesses, the annual ring pattern of the boards and the number of layers in the CLT elements. The finite element model agreed well with experimental findings. Connection stiffness was overestimated, while the strength was only slightly underestimated. The parameter study revealed that the wall thickness effect on the stiffness and strength of the connection was strongest for the practically most relevant wall thicknesses between 80 and about 160 mm. It also showed that an increasing floor thickness leads to higher stiffness and strength, due to the load dispersion effect. The increase was found to be stronger for smaller wall thicknesses. The influence of the annual ring orientation, or the pith location, was assessed as well and showed that boards cut closer to the pith yielded lower stiffness and strength. The findings of the parameter study were fitted with regression equations. Finally, a dimensionless ratio of the wall-to-floor thickness was used for deriving regression equations for stiffness and strength, as well as for load and stiffness increase factors, which could be used for the engineering design of CLT connections. Full article

(This article belongs to the Special Issue Timber Structures: Latest Developments, Challenges, and Perspectives)

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17 pages, 3179 KiB

Open AccessArticle

Comparison between Predicted and Measured Moisture Content and Climate in 12 Monitored Timber Structures in Switzerland

by Marcus Schiere, Bettina Franke, Steffen Franke and Andreas Müller

Buildings 2021, 11(5), 181; https://doi.org/10.3390/buildings11050181 - 24 Apr 2021

Cited by 1 | Viewed by 2414

Abstract

Wood is a hygroscopic material that primarily adapts its moisture content to the surrounding relative humidity. The climate in a structure or building depends on the building type and the region the structure is located in. In this study, the effect of region [...] Read more.

Wood is a hygroscopic material that primarily adapts its moisture content to the surrounding relative humidity. The climate in a structure or building depends on the building type and the region the structure is located in. In this study, the effect of region on the moisture content of wood was investigated. Measurements taken in 12 ventilated timber structures were compared to the theoretical equilibrium moisture content calculated from the relative humidity and temperature in 107 meteorological stations across Switzerland. The monitored load-bearing elements were made of softwood and protected from the direct impact of weather. The climatic conditions around the Alps, a mountain range that runs from France to Austria and crosses Switzerland, can be divided into the following three different regions: (1) south of the Alps, where the climate is affected mainly by the Mediterranean sea; (2) north of the Alps, where the climate is affected by the Atlantic Ocean; and (3) the inner Alps, where the climate is considered to be relatively dry. The climatic conditions of the three separate regions were reflected in the measurements made in the monitored timber structures. Differences between the regions were quantified. The moisture content and relative humidity, similarly to temperature, depended on altitude (above sea level). Full article

(This article belongs to the Special Issue Timber Structures: Latest Developments, Challenges, and Perspectives)

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17 pages, 4571 KiB

Open AccessArticle

Nonlinear Static Seismic Response of a Building Equipped with Hybrid Cross-Laminated Timber Floor Diaphragms and Concentric X-Braced Steel Frames

by Andrea Roncari, Filippo Gobbi and Cristiano Loss

Buildings 2021, 11(1), 9; https://doi.org/10.3390/buildings11010009 - 24 Dec 2020

Cited by 6 | Viewed by 9321

Abstract

Simplified seismic design procedures mostly recommend the adoption of rigid floor diaphragms when forming a building’s lateral force-resisting structural system. While rigid behavior is compatible with many reinforced concrete or composite steel-concrete floor systems, the intrinsic stiffness properties of wood and ductile timber [...] Read more.

Simplified seismic design procedures mostly recommend the adoption of rigid floor diaphragms when forming a building’s lateral force-resisting structural system. While rigid behavior is compatible with many reinforced concrete or composite steel-concrete floor systems, the intrinsic stiffness properties of wood and ductile timber connections of timber floor slabs typically make reaching a such comparable in-plane response difficult. Codes or standards in North America widely cover wood-frame construction, with provisions given for both rigid and flexible floor diaphragms designs. Instead, research is ongoing for emerging cross-laminated-timber (CLT) and hybrid CLT-based technologies, with seismic design codification still currently limited. This paper deals with a steel-CLT-based hybrid structure built by assembling braced steel frames with CLT-steel composite floors. Preliminary investigation on the performance of a 3-story building under seismic loads is presented, with particular attention to the influence of in-plane timber diaphragms flexibility on the force distribution and lateral deformation at each story. The building complies with the Italian Building Code damage limit state and ultimate limit state design requirements by considering a moderate seismic hazard scenario. Nonlinear static analyses are performed adopting a finite-element model calibrated based on experimental data. The CLT-steel composite floor in-plane deformability shows mitigated effects on the load distribution into the bracing systems compared to the ideal rigid behavior. On the other hand, the lateral deformation always rises at least 17% and 21% on average, independently of the story and load distribution along the building’s height. Full article

(This article belongs to the Special Issue Timber Structures: Latest Developments, Challenges, and Perspectives)

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Review

Jump to: Research

30 pages, 5772 KiB

Open AccessFeature PaperReview

From Trees to Skyscrapers: Holistic Review of the Advances and Limitations of Multi-Storey Timber Buildings

by Marcelo González-Retamal, Eric Forcael, Gerardo Saelzer-Fuica and Mauricio Vargas-Mosqueda

Buildings 2022, 12(8), 1263; https://doi.org/10.3390/buildings12081263 - 18 Aug 2022

Cited by 5 | Viewed by 3405

Abstract

Products derived from trees have been used by mankind for thousands of years, where timber has a long tradition as an ecological construction material. There is currently an increasing trend in multi-storey timber buildings, because of the projected growth in the demand for [...] Read more.

Products derived from trees have been used by mankind for thousands of years, where timber has a long tradition as an ecological construction material. There is currently an increasing trend in multi-storey timber buildings, because of the projected growth in the demand for housing in urban areas between now and 2050, along with the urgent need for a more sustainable and productive construction industry. The construction of these buildings is now possible thanks to the new advances in architecture, engineering, and construction (AEC) and the new technological developments around timber construction. Its industrialization requirements imply a paradigm shift for the construction industry, which requires, among other aspects, the early and collaborative integration of stakeholders in its design and construction process. According to this, the objective of this review article is to determine the main advances and limitations related to the design and construction of multi-storey timber buildings, categorizing them in aspects such as sustainability, engineering and construction sciences, and collaborative design. The methodology of this article was based on the review of 266 articles published in Web of Science (WoS), as indexed scientific journals, between 2017 and mid-2022, performing a comparative and cooccurrence analysis of the contents. The results evidenced that 73% of the articles showed advances and limitations corresponding to the engineering and construction sciences category, 23% to sustainability, and the remaining 4% to collaborative design. The main advances in the development of multi-storey timber buildings are related to seismic analysis, connections design, fire performance, and fire design. While the main limitations are related to social sustainability, the results are not conclusive due to the low number of publications that support them. Full article

(This article belongs to the Special Issue Timber Structures: Latest Developments, Challenges, and Perspectives)

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