NEW RESEARCH AND DEVELOPMENT IN THE FIELD OF TIMBER …€¦ · RECENT SANDWICH TECHNOLOGY IN...
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NEW RESEARCH AND DEVELOPMENT IN THE FIELD OF TIMBER STRUCTURES toward more optimal usage of Timber DR. RASOUL ATASHIPOUR Researcher in Lightweight Structures Division of Structural Engineering Chalmers University of Technology
Transcript of NEW RESEARCH AND DEVELOPMENT IN THE FIELD OF TIMBER …€¦ · RECENT SANDWICH TECHNOLOGY IN...
NEW RESEARCH AND DEVELOPMENT IN THE FIELD OF TIMBER STRUCTUREStoward more optimal usage of Timber
DR. RASOUL ATASHIPOURResearcher in Lightweight StructuresDivision of Structural EngineeringChalmers University of Technology
2019-05-23 Chalmers University of Technology 2
AGENDA Development of an Innovative sandwich panel for multi-storey timber building Research studies in the field of timber structures
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BACKGROUND Timber has been traditionally used for housing for centuries
→ Sweden has a strong background in timber structures
Manufacturing methods and products need to be developed more, toward more OPTIMAL USAGE of timber material.
There is a need for industrialized (fast and cost-effective) production
To be able to compete, we need to develop and utilize the knowledge of advanced structures and develop more efficient pre-fabricated timber structural elements!
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Innovative sandwich floor panel for multi-storey timber building
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NEED FOR ADVANCED TECHNOLOGIES To be able to compete, we need to develop and utilize the knowledge of advanced
structures and develop more efficient pre-fabricated timber structural elements!
One example: floors; In the current trend of constructing multi-story timber buildings, there is a need for new structural floor element that provides high stiffness and strength.
Conventional timber floor systems used in Sweden today have large structural height and are prone to vibration problems.
Other traditional timber building structural elements can be replaced with developed more efficient elements; light-weight roof, stabilization wall, etc.
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SANDWICH STRUCTURES Sandwich elements provide high strength and stiffness by using material in an efficient
way, and choose the right configuration.
They are composed of two sheets and a core in between; they exhibit high flexibility and great potential for optimal designs…
Nowadays, larger structures using sandwich elements are often made in steel or FRP.
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RECENT SANDWICH TECHNOLOGY IN CONSTRUCTION(Australia)
Oriented strand boards (OSBs) sheets that sandwich a layer offoam plastic core; Wall and lightweight roof panels
(Austria) Kielsteg a sandwich panel product with V-formed core
Application: Timber floor panel
(Switzerland) Lignatur is a timber sandwich product with web core shape,
developed for roofs and floors
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THE IDEAWe need a sandwich core shape that:
To be relatively easy and cost efficient to be manufactured
High structural performance
Stiff faces in stretching, and stiff core in shear!
Corrugated-core!Free spaces in the core can be used forinserts, piping, etc, and filled by insulation materials..
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THE IDEA Combination of the concepts of:
Laminated composites + Sandwich configuration + bio-material!
Desired lay-up pattern + various geometric dimensions + different timber material choices!
Flexibility in design:
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BENEFITS OF THE INNOVATIVE PANEL Lower height compared to traditional floors (50%)
→ more space to sell, → lower overall height of the building,→ possibility to fit more floors in a multi-storey building
with restricted height,
Larger spans to be covered (up to 12m)→ No intermediate columns (architecturally attractive)
Shear wall elements (stabilizing elements)
Roof elements (light-weight)
Tailor-made products (specific cuts, installations, etc.)
Light-weight prefabricated construction elements: less carbon footprint, cheaper transport,…
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THEORETICAL RESEARCH & OPTIMIZATIONMaterial choice
Grain global orientation
Corrugation orientation
Practical constraints
Method of analysis
Homogenization approach+
Plate theories
(The mathematical modelling and analytical solutions
enable optimization)
Mathematical modeling &analytical solutions ¶metric study
FE modelling and analysis,Time-consuming; no chance for optimization…!Used for validation + ULS check: buckling global & local, max stress, etc.
Finite element (FE) verification:
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OPTIMIZATION RESULTSOptimized geometry (height reduction) corresponding to each of: 5 different face materials / 2 core materials / 4 combination of grain orientation of faces & core / 2 possible corrugation alignment (along shorter or longer edge) / 5 different core sheet thicknesses
320 height-optimal cases
Minimization of used material
20 optimal cases
HEIGHT COMPARISON
050
100150200250300350400450500
Traditional Innovative
mm
Comparison of heights
fire gupsum gypsum boardacoustic insulation Structural partgypsum board Surface
• Traditional floors, 380 mm• Suggested concept, 135 mm • 245 mm/storey can be saved
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MANUFACTURING OF THE PANEL
Production of the corrugated core is found feasible!
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INTEGRATED PANEL, LARGE SCALE PRODUCTION
Flexibility in both sheet panels and the core make it possible to produce integrated large panels.
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TESTS FOR PROOF OF CONCEPT
Dynamic & Vibration performanceThe modal tests on the panel; to capture the Eigen-frequencies and damping factor of the panel
Static tests on the panelTo capture the stiffness of the plate (i.e. deflection related serviceability limit state) and evaluate the bi-directional behavior of the slab
Static tests on beamsBeams cut from the panel tested to verify the design assumption on failure load of the system (i.e. strength in ULS)
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FURTHER STUDIES Acoustics (bio-based insulating material to fill the cells!), Joints and connections, Effect of filling bio-based materials, Adhesive interlayer bonding, Fire performance.
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Research Studies in the field of Timber Structures
Improvement of design & development of reliable accurate calculation models
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STABILIZING WALL ELEMENT OF TRÄ8Improvement for multi-storey building Construction
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STABILIZING WALL ELEMENT OF TRÄ8
θ
τ cr
0 30 60 90 120 150 1800
20
40
60
80
100
120|-------| [90/0/0/0/0]S-|-----|- [0/90/0/0/0]S--|---|-- [0/0/90/0/0]S---|-|--- [0/0/0/90/0]SDQM
Clamped edges
θ
Effect of layup pattern and grain inclination
Accurate simple calculation models established without need of time-consuming simulation softwares
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STABILIZING WALL ELEMENT OF TRÄ8
h2 / h
w0,
* max
0.1 0.2 0.3 0.4 0.5 0.6 0.70
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2503-D FEM (Center)PresentReddy-BickfordTimoshenkoEuler-Bernoulli
L / h
(h/L
)3w
0,* m
ax
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403-D FEM (Center)PresentReddy-BickfordTimoshenkoEuler-Bernoulli
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STABILIZING WALL ELEMENT OF TRÄ8
h1
wi
0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.450
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WBendingWConventional shearWAdditional interlayer shear
h1
wm
ax
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3-D FEM (center)Present methodEarlier engineering method [1]Reddy-Bickford (conventional)Timoshenko (constant SC)Euler-Bernoulli
G =E
wm
ax
10-6 10-5 10-4 10-3 10-2 10-1 100 101 102
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100003-D FEM (center)Present methodEarlier engineering method [1]Reddy-Bickford (conventional)Timoshenko (constant SC)Euler-Bernoulli
Wooden box-type of beams
Sandwich-typeof beams
Trä8:G =E = 0.833
A weak shear web model based on Partial Composite Theory (PCT) is developed, Leading to a thorough but easy to be used model for deformation prediction!
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RESEARCH PROJECT ON GIR CONNECTION
Due to past disagreements, the design rules considering glued-in rods included in a previous version of the Eurocode 5 (EC5) was removed from the latest valid version.
The aim of this project is create and deliver design model for GiR connection through advanced analyses and experiments, to be implemented into a software.
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RESEARCH PROJECT ON GIR CONNECTION
P0
Pw
x
Laxu
Undamaged part
τfRegion of progressive damage
δ
τ Realistic behavior of adhesive Bi-linear model
τf
δf δmaxδ*max
Gf = Gf
Developing a reliable calculation model based on Nonlinear Elastic Fracture Mechanic (NLEFM)
Comparison of computer simulations and the developed model
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RESEARCH PROJECT ON GIR CONNECTION
Experimental studies are ongoning for calibration of the developed design model
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THANKS FOR LISTENING!
