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Folding Plate Roof StructuresProgramme : MSc in Civil Engineering with Integrated Design
Name of Student : Sokratis Baltas
Supervisor : Alessandro Margnelli, Daniel BosiaIndustrial Supervisor: Daniel Bergsagel
UCL Department of Civil, Environmental and Geomatic Engineering, Gower St, London ,WC1E 6BT
Industrial Partnership with AKT II Ltd
1. Introduction
2. Aims & Objectives
Establish a design and analysis methodology for folding structures
Investigate the possibility of accommodating thickness on a folding pattern so that it is able to be foully folded
Investigate the performance of novel materials on folding structures
Access the structural behavior of the structure when deployed on different positions
Investigate the dynamic response of the system and the change inflicted due to the change of deployment
Understand kinematics of deployment and suggest a design solution of the moving mechanism
Investigate the correlation of geometry to the structural properties of the system
3. Methodology
4. Analysis Results & Discussion
5. Conclusion 6. Future Work
The transformation of flat structural surfaces into folded geometries
through a series of folds, has been of interest to engineers, architects
and mathematicians. A folding pattern whether simple or complex,
is proven to provide aesthetically interesting architecture, as well as
structurally efficient systems. Origami tessellations, has been a field of
those research endeavors, whether it is on smaller scale applications
such as in aerospace engineering, or on a building scale. The
attribute of such folding patterns to evolve into spatial geometries
form flat surfaces, offers the opportunity for researching the feasibility
and design procedures of folding structures inspired by such
patterns.
In this thesis a roof structure that is designed to possess the attribute to fold and unfold and thus changing its
geometry in respect to its deployment position, is investigated. The concept of deployability, imposes design
challenges that need to be examined and resolved. However, the aspiration for designing a structure that
alternates its geometry to accommodate different function needs, or to acquire an optimum shape depending
on load or environment conditions, is interesting from an architectural and engineering perspective. Additionally,
folding patterns as the one studied hereby, offer the opportunity to design structures capable to be fully folded on
a flat pack stowed state and transported to be deployed on several locations or sites needed.
Fig.1 Paper model of the structure
Fig.2 Methodology process
Fig.5 Roof Tip (Uz) Deflection of the SLS combination on all deployment angles (100|200mm thickness set)
The structural analysis concluded into comparative
results among the different deployment angles in terms
of deflection and stresses. It has been shown that both
deflections and stresses increase as the angle ξ
increases up to 90o. There is also a significant
concertation of stresses along the basic fold line of the
cantilever support. At those concertation areas, there
are stressed parts by both principal tensile and
compressive forces. The constant increase of deflection
and stresses is due to the decrease of system inertia
because of the unfolding.Fig.6 Principal Forces on roof basic fold point (dashed lines are on vertical posts, continuous are on rood)
Fig.3 Physical Foamboard model that displays the folding motion and the material thickness trimming on the fold
The geometry of the system was inspired by
a simple Origami folding pattern
The foldability of the roof was investigated
when thickness is added
For the roof to be fully foldable, the plate
thickness had to be halved at the section of
the reverse fold
The final geometry was parametrically
designed
The plates were designed as carbon fibre
ribbed stressed skin panels
Finite Element analysis was executed (elastic
and modal) for 5 deployment angles and
two different panel thickness sets
(100|200mm & 200|400mm)
The folding motion was assessed and a base
moving mechanism was proposed
A business case for folding structures has
been established
The structural behavior is primarily depending to
the geometry rather that material. The inertia of
the structure is the one of the dominant
parameters
A multi variable optimization process should be
engaged to refine thickness and geometry
The ability of folding can be used to address
different structural needs depending on loading
conditions
Dynamics of the system are changing as it unfolds
Formulate a multi variable optimization design
process
Investigate the effect of wind on folding
lightweight structures (dynamically)
Investigate kinematics of deployment and
dynamics of folding movement
Design the linear hinges for the structure
Optimize material usage by following principal
stress paths and utilizing state of the art
fabrication methods
A modal analysis has been executed to evaluate
the change in dynamic response in relation to the
deployment process. It was concluded that as
the structure unfolds the global stiffness is
alternating, which results into different modal
periods [eigen values] and different modal
shapes [eigen vectors]. The translational mode in
axis Z starts as the 3rd mode in 22.5o, ending up to
be the 1st mode at 60o and 90o. A key
observation is that mostly at 60o and 45o , the 1st
and 2nd periods are almost identical, which
maybe raising aeroelastic concerns.
Fig.4 Folding pattern of the structure (a), geometric parameters of folds (b)
(a)
(b)
Fig.7 Fundamental mode shapes for each deployment
Fig.8 Fundamental periods
ξ=22.5ο ξ=30ο ξ=45ο ξ=60ο ξ=90ο
Fig.9 Structural and performance indicators
Fig.10 Correlation of calculated deflection to ρ
Fig.11 Optimal ξ in respect to deflection and
covered area
Evaluation indicators derived from the uniformly loaded
cantilever equations and correlated mathematically
only to angle ξ, were introduced.
y3: inertia indicator, ρ: tip deflection indicator, ρ’: fold
stress indicator, A: projected covered area by the roof.
This thesis was conducted with industrial partnership and under the supervision and guidance of AKT II Ltd
Software used:
September 2017 |London | United Kingdom