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Huber, J. A., Ekevad, M., Girhammar, U. A. & Berg, S. (2018). A Review of Structural Robustness with Focus on Timber Buildings. In: : . Paper presented at 40th IABSE Symposium, Nantes 2018.
Open this publication in new window or tab >>A Review of Structural Robustness with Focus on Timber Buildings
2018 (English)Conference paper, Published paper (Refereed)
Abstract [en]

With an increasing number of storeys, timber buildings require closer attention to structuralrobustness. If a building can survive unforeseen events (e.g. accidents, terrorism), lives can be saved.The literature appears to be rather limited concerning robustness of timber buildings. This paperaims to give a brief review on robustness in general and design guidelines for timber in specific. Theresults indicate that connection design is a key aspect for robustness. Like in seismic design, by usingthe ductile capacity of connectors, the brittleness of timber can be controlled. For light timber-framebuildings, more guidelines exist than for posts and beams and cross-laminated timber, which bothseem to be similar to steel frames and precast concrete respectively regarding robustness.

Keywords
robustness, timber, disproportionate collapse, progressive collapse, alternative load path
National Category
Other Civil Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-70959 (URN)
Conference
40th IABSE Symposium, Nantes 2018
Funder
VINNOVA, Bioinnovation 4.4
Available from: 2018-09-24 Created: 2018-09-24 Last updated: 2018-09-24
Atashipour, S. R., Girhammar, U. A. & Challamel, N. (2018). A weak shear web model for deflection analysis of deep composite box-type beams. Engineering structures, 155, 36-49
Open this publication in new window or tab >>A weak shear web model for deflection analysis of deep composite box-type beams
2018 (English)In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 155, p. 36-49Article in journal (Refereed) Published
Abstract [en]

Deep box-type beams, consisting of framing members and sheathings, are sensitive to shear deformations and hence appropriate refined theories or complicated magnification factors are needed to be used to obtain accurate results. For sheathings or webs between the framing members that are weak in shear, additional shear deformations occur corresponding to the relative axial displacement between the framing members. These sandwich-type or partial interaction-type of in-plane shear behaviour between the framing members, needs to be taken into account, especially when the web shear stiffness is very low. The composite box-type beam treated here is composed of three framing members with sheathings on both sides. To incorporate effects of the sheathings shear deformations between the framing members on the deflection, the sheathings, here called web interlayers, are modelled as shear media with equivalent slip moduli corresponding to a partially interacting composite beam model. Governing equilibrium equations of the model are obtained using the minimum total potential energy principle and solved explicitly. The obtained results are compared with those based on different conventional beam theories and 3-D finite element (FE) simulations. It is shown that the model is capable of predicting accurately the deflection for a wide range of geometry and property parameters. It is demonstrated that the deflection of such deep box-type beams can be expressed as the summation of three different effects, namely bending deformations, conventional shear deformations in the framing members and sheathings, and additional in-plane shear deformations or shear slips of the weak web causing relative axial displacements between the framing members.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-59992 (URN)10.1016/j.engstruct.2017.10.073 (DOI)000419409800004 ()2-s2.0-85033432970 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-11-13 (andbra)

Available from: 2016-10-27 Created: 2016-10-27 Last updated: 2018-06-11Bibliographically approved
Huber, J. A., Ekevad, M., Berg, S. & Girhammar, U. A. (2018). Assessment of Connections In Cross-Laminated Timberbuildings Regarding Structural Robustness. In: : . Paper presented at 2018 World Conference on Timber Engineering, Seoul, Republic of Korea, August 20-23 2018.
Open this publication in new window or tab >>Assessment of Connections In Cross-Laminated Timberbuildings Regarding Structural Robustness
2018 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Cross-laminated timber makes timber buildings with an increasing number of storeys achievable. Withmore storeys, structural robustness needs more attention to make a building survive unforeseen events (e.g. accidents,terrorism) and save lives. For steel and concrete buildings, design methods for robustness focus on connection details.The assessment of joints in cross-laminated timber buildings regarding robustness is rather limited in the literature. Theobjective of this paper is to conduct an initial assessment of the connectors after the removal of a wall in a platformcross-laminated timber building. We used the finite element method and the component method for the analysis of acase building. The results indicate that the wall-to-wall and the floor-to-floor connectors may fail at low deflectionlevels leading to high shear loads in the floor panel above the removed wall, which might induce cracking. The removalanalysis was only partially completed, but we identified an indication of the deformation behaviour of the case building.Testing and refined modelling of the connections is needed in the future to verify the results. This study may facilitatefuture investigations regarding robustness of multi-storey cross-laminated timber buildings.

Keywords
Robustness, Connection, Component method, Cross-laminated timber, Finite element method, Disproportionate collapse
National Category
Other Civil Engineering Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-70599 (URN)
Conference
2018 World Conference on Timber Engineering, Seoul, Republic of Korea, August 20-23 2018
Projects
Bioinnovation 4.4
Funder
VINNOVA
Available from: 2018-08-27 Created: 2018-08-27 Last updated: 2018-08-31Bibliographically approved
Atashipour, S. R. & Girhammar, U. A. (2018). Influence of Grain Inclination Angle on Shear Buckling of Laminated Timber Sheathing Products. Structures, 13, 36-46
Open this publication in new window or tab >>Influence of Grain Inclination Angle on Shear Buckling of Laminated Timber Sheathing Products
2018 (English)In: Structures, ISSN 2352-0124, Vol. 13, p. 36-46Article in journal (Refereed) Published
Abstract [en]

Recent advances in timber production industries have enabled production of new innovative laminated timber products having layers with grain inclination angle. This paper is aimed to study influence of grain inclination angle in the laminated veneer lumber (LVL) and plywood sheathings on their shear buckling loads. Two extreme edge conditions of simply supported and clamped edges are considered. First, an accurate differential quadrature (DQ) computational code is developed using MAPLE programming software to obtain eigen buckling values and their corresponding eigen mode shapes. Next, for convenience of engineering calculations, approximate algebraic formulae are presented to predict critical shear buckling loads and mode shapes of LVL and plywood panels having layers with grain inclination angle, with adequate accuracy. Furthermore, finite element (FE) modelling is conducted for several cases using ANSYS software to show validity and accuracy of the predicted results for the problem. It is shown that the highest shear buckling loads of LVL sheathings is achievable when the inclination angle of about 30° with respect to the shorter edges is considered for production of LVL panels, whereas the same angle with respect to the long edges of the LVL sheathings results in a relatively lower buckling load. Considering similar inclination angle with respect to any edges of a plywood sheathings will also results in its highest pre-buckling capacity. It is also demonstrated that, under optimal design and certain loading circumstances, LVL shows a higher shear buckling capacity compared to a similar plywood sheathing.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-66675 (URN)10.1016/j.istruc.2017.10.003 (DOI)2-s2.0-85034242984 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-11-21 (andbra)

Available from: 2017-11-21 Created: 2017-11-21 Last updated: 2018-06-11Bibliographically approved
Huber, J. A., Ekevad, M., Girhammar, U. A. & Berg, S. (2018). Structural Robustness of Timber Buildings. In: : . Paper presented at 2018 World Conference on Timber Engineering, Seoul, Republic of Korea, August 20-23 2018.
Open this publication in new window or tab >>Structural Robustness of Timber Buildings
2018 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The number of storeys in timber buildings are increasing. With more storeys, structural robustness needsmore attention, to make a building survive unforeseen events (e.g. accidents, terrorism) and save lives. The state of theart regarding robustness of concrete and steel buildings seems to be rather refined, but for timber buildings, theliterature appears to be quite limited. This study aims to review the design methods for robustness of timber buildings.First, the terminology and definitions are introduced. Then, the state of the art for design methods for robustness ingeneral are presented. Finally, the design methods for timber buildings are discussed and compared to those from otherbuilding materials. The results indicate that the guidelines for light timber-frame buildings are more refined than thosefor post and beam and cross-laminated timber buildings. Regarding robustness, the latter two construction types exhibitcertain similarities to steel frames and precast concrete buildings respectively. For timber, ductile connections can beused to avoid brittle timber failure after local damages, which resembles the approach of seismic design. Future researchin robustness should focus on the connection details in multi-storey timber buildings.

Keywords
Robustness, Timber buildings, Disproportionate collapse, Progressive collapse, Alternative load paths
National Category
Other Civil Engineering Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-70593 (URN)
Conference
2018 World Conference on Timber Engineering, Seoul, Republic of Korea, August 20-23 2018
Projects
Bioinnovation 4.4
Funder
VINNOVA
Available from: 2018-08-27 Created: 2018-08-27 Last updated: 2018-08-31Bibliographically approved
Caprolu, G., Girhammar, U. A. & Källsner, B. (2017). Analytical models for splitting capacity of bottom rails in partially anchored timber frame shear walls based on fracture mechanics (ed.). Wood Material Science & Engineering, 12(3), 165-188
Open this publication in new window or tab >>Analytical models for splitting capacity of bottom rails in partially anchored timber frame shear walls based on fracture mechanics
2017 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, no 3, p. 165-188Article in journal (Refereed) Published
Abstract [en]

Plastic design methods can be used for determining the load-carrying capacity of partially anchored shear walls. For such walls, the leading stud is not fully anchored against uplift and tying down forces are developed in the sheathing-to-framing joints and the bottom rail will be subjected to crosswise bending, leading to possible splitting failure of the rail. In order to use these plastic design methods, a ductile behaviour of the sheathing-to-framing joints must be ensured. In two earlier experimental programmes, the splitting failure capacity of the bottom rail has been studied. Two brittle failure modes occurred during testing: (1) a crack opening from the bottom surface of the bottom rail and (2) a crack opening from the side surface of the bottom rail. In this article, a fracture mechanics approach for the two failure modes is used to evaluate the experimental results. The comparison shows a good agreement between the experimental and analytical results. The failure mode is largely dependent on the distance between the edge of the washer and the loaded edge of the bottom rail. The fracture mechanics models seem to capture the essential behaviour of the splitting modes and to include the decisive parameters. 

National Category
Building Technologies Other Mechanical Engineering
Research subject
Timber Structures; Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-15998 (URN)10.1080/17480272.2015.1075228 (DOI)000399667800006 ()2-s2.0-84941334544 (Scopus ID)f951919b-af7e-4d7f-ba90-8edc444e7b12 (Local ID)f951919b-af7e-4d7f-ba90-8edc444e7b12 (Archive number)f951919b-af7e-4d7f-ba90-8edc444e7b12 (OAI)
Note

Validerad; 2017; Nivå 2; 2017-04-24 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Atashipour, S. R., Girhammar, U. A. & Al-Emrani, M. (2017). Exact Lévy-type solutions for bending of thick laminated orthotropic plates based on 3-D elasticity and shear deformation theories. Computers & structures, 163, 129-151
Open this publication in new window or tab >>Exact Lévy-type solutions for bending of thick laminated orthotropic plates based on 3-D elasticity and shear deformation theories
2017 (English)In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 163, p. 129-151Article in journal (Refereed) Published
Abstract [en]

Exact solutions for static bending of symmetric laminated orthotropic plates with different Lévy-type boundary conditions are developed. The shear deformation plate theories of Mindlin-Reissner and Reddy as well as the three-dimensional elasticity theory are employed. Using the minimum total potential energy principle, governing equilibrium equations of laminated orthotropic plates and pertaining boundary conditions are derived. Closed-form Lévy-type solutions are obtained for the governing equations of both theories using separation of variables method and different types of classical boundary conditions, namely simply-supported, clamped and free edge, are exactly satisfied. Thereafter, 3-D elasto-static equations for orthotropic materials are solved for bending analysis of laminated plates using two different approaches. First, the method of separation of variables is utilized and an exact closed-from solution is achieved for simply-supported laminated orthotropic plates. Next, a combined Fourier-Differential Quadrature (DQ) approach is employed to present a semi-numerical solution for bending of laminated orthotropic plates with Lévy-type boundary conditions based on the three-dimensional elasticity theory. High accuracy of the presented solutions are proven and comprehensive comparative numerical results are provided and discussed. Presented comparative numerical results can serve as benchmark for investigating the correctness of new solution methods which may be established in the future.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-60002 (URN)10.1016/j.compstruct.2016.12.026 (DOI)000393931800012 ()2-s2.0-85006741906 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-01-09 (andbra)

Available from: 2016-10-27 Created: 2016-10-27 Last updated: 2018-09-13Bibliographically approved
Girhammar, U. A., Gustafsson, P. J. & Källsner, B. (2017). Modeling of shear walls using finite shear connector elements based on continuum plasticity. Frontiers of Structural and Civil Engineering, 11(2), 143-157
Open this publication in new window or tab >>Modeling of shear walls using finite shear connector elements based on continuum plasticity
2017 (English)In: Frontiers of Structural and Civil Engineering, ISSN 2095-2430, E-ISSN 2095-2449, Vol. 11, no 2, p. 143-157Article in journal (Refereed) Published
Abstract [en]

Light-frame timber buildings are often stabilized against lateral loads by using diaphragm action of roofs, floors and walls. The mechanical behavior of the sheathing-to-framing joints has a significant impact on the structural performance of shear walls. Most sheathing-to-framing joints show nonlinear load-displacement characteristics with plastic behavior. This paper is focused on the finite element modeling of shear walls. The purpose is to present a new shear connector element based on the theory of continuum plasticity. The incremental load-displacement relationship is derived based on the elastic-plastic stiffness tensor including the elastic stiffness tensor, the plastic modulus, a function representing the yield criterion and a hardening rule, and function representing the plastic potential. The plastic properties are determined from experimental results obtained from testing actual connections. Load-displacement curves for shear walls are calculated using the shear connector model and they are compared with experimental and other computational results. Also, the ultimate horizontal load-carrying capacity is compared to results obtained by an analytical plastic design method. Good agreements are found.

Place, publisher, year, edition, pages
Springer, 2017
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-62947 (URN)10.1007/s11709-016-0377-3 (DOI)000401744300002 ()2-s2.0-85017186171 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-05-30 (rokbeg)

Available from: 2017-04-07 Created: 2017-04-07 Last updated: 2018-07-10Bibliographically approved
Daerga, P.-A. & Girhammar, U. A. (2017). Programmering av Matlab-rutiner för utvärdering av experiment med knutpunktsförband i MFB-systemet: Beröringsfri mätning av krafter och deformationer med Qualisys Motion Capture – Beskrivning av mätsystem och efterbehandling av mätdata.
Open this publication in new window or tab >>Programmering av Matlab-rutiner för utvärdering av experiment med knutpunktsförband i MFB-systemet: Beröringsfri mätning av krafter och deformationer med Qualisys Motion Capture – Beskrivning av mätsystem och efterbehandling av mätdata
2017 (Swedish)Report (Other (popular science, discussion, etc.))
Publisher
p. 22
Series
Technical report / Luleå University of Technology, ISSN 1402-1536
National Category
Engineering and Technology Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-63467 (URN)978-91-7790-008-5 (ISBN)
Available from: 2017-05-20 Created: 2017-05-20 Last updated: 2017-11-24Bibliographically approved
Huber, J. A., Ekevad, M. & Girhammar, U. A. (2017). Review of Robustness in Timber Buildings. In: : . Paper presented at World Multidisciplinary Civil Engineering - Architecture - Urban Planning Symposium, Prague, June 12-16, 2017.
Open this publication in new window or tab >>Review of Robustness in Timber Buildings
2017 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

Timber buildings today aim for taller and larger dimensions to accommodate increased numbers of occupants.  In tall buildings, more human lives are at risk if large portions of the structure collapse progressively during catastrophic failure events. To safeguard timber structures from disproportionate collapse due to localised failures, the aspect of robustness in particular needs to be considered. In the literature about building structures the term robustness seems to be contemplated in diverse ways. Several possible approaches to define and analyse this property can be found. However, certain consensus as to what characterises a robust structure seems to exist. A review of the concept of robustness for building structures in general and timber structures in specific is presented in this paper. Certain commonly applied terminology and definitions in the context of robustness are analysed. In the literature, risk-based, reliability-based and performance-based concepts for robustness appear to be established. The first two concepts are briefly summarised. The performance-based concept is treated in greater detail to highlight different procedures of deterministic robustness analyses. Common general characteristics of robust buildings which seem to be agreed upon are summarised. Robustness provisions for timber buildings in specific are described and compared to provisions in other building materials such as steel and concrete. The development of alternate load paths during local failure seems to play an essential role in preventing progressive collapse in buildings. The literature about robustness seems to be comprehensive concerning general considerations and concerning structures built in concrete or steel but appears to be rather limited in regards to timber structures. Evaluations of robustness in timber structures seem to be focused on risk-based and reliability-based concepts in literature.

Keywords
robustness, timber structures, disproportionate collapse, progressive collapse, alternate load path, element removal
National Category
Wood Science Building Technologies Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-65890 (URN)
Conference
World Multidisciplinary Civil Engineering - Architecture - Urban Planning Symposium, Prague, June 12-16, 2017
Projects
Bioinnovation 4.4
Available from: 2017-09-29 Created: 2017-09-29 Last updated: 2017-11-24Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-0336-6433

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