Folding Plate Roof Structures Programme : MSc in Civil Engineering with Integrated Design Name of Student : Sokratis Baltas Supervisor : Alessandro Margnelli, Daniel Bosia Industrial 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 90 o . 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 3 rd mode in 22.5 o , ending up to be the 1 st mode at 60 o and 90 o . A key observation is that mostly at 60 o and 45 o , the 1 st and 2 nd 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=22.5 ο ξ=30 ο ξ=45 ο ξ=60 ο ξ=90 ο 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. y 3 : 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