Timber gridshells are a very efficient way of covering large spaces while also providing a unique architectural and material quality. As this can still be considered an emergent technology, the design of such buildings has relied on a relatively substantial amount of experimental work. This thesis, upon reviewing the design and construction processes of previous timber gridshells, puts forward a structural model that aims to represent the true nature and specifics of single and double-layered timber gridshells. The parametrically determined geometry of a computational prototype is described and used as a basis for a non-linear elastic numerical analysis. Particular attention is given to modelling the connections between the timber laths that provide composite bending action in a double layer grid. The deformation behaviour and the imperfection sensitivity are assessed with a view to understanding how gridshells respond under different conditions. A new gridshell will inevitably be analysed with computer software, but the information presented in this dissertation will be useful for scheme design as well as the calibration of the computer analysis.

For the last few decades, the interest in green roofs has been developing quickly because of the benefits they have on the modern urban environment situation. Recently, of the range of native habitats in the UK appropriate for green roof application, calcareous grassland plant communities have been given much attention for use on green roofs because of the similarity that these habitats have to green roof conditions. However, there has been very little or no research into how locally-characteristic habitats can be recreated on green roofs, and this has led to a lack of specific recommendations for native plant communities or assemblages on green roofs in the UK. Thus, this thesis investigates the feasibility of calcareous grassland vegetation for green roof application in the UK. This study is comprised of four sections; (i) A review of calcareous grassland types, ecology and characteristics, (ii) A discussion of the restoration ecology of calcareous grasslands, (iii) An investigation into substrates for supporting calcareous grasslands on green roofs, (iv) Experimental investigation of plant selections and communities for calcareous grasslands on green roofs. The substrates investigation consisted of testing mixtures containing Limestone, LECA (Light Expanded Clay Aggregate), Brick rubbles with organic matter and loam in five composition rates. Leucanthemum vulgare, Briza media, and Prunella vulgaris were selected as indicator species. All the substrates met the minimum requirements that conform to FLL standards (the German guidelines for green roofs, Society of Landscape Development and Landscape Design), except for LECA and Limestone substrate types that tended not to meet the minimum moisture content (20%). Most of the substrates supported high seedling survival. In general, Limestone substrate types and a 60:20:20 (mineral material: loam: organic matter) composition rate tended to produce high seedling emergence and growth across all of the species, while LECA and Brick rubble substrate types, and 100:0:0 composition rate did in the opposite. The most successful substrate was a Limestone substrate type with 60:20:20 composition rate that had relatively good balance of moisture content and air filled porosity, and supported high seedling emergence, survival and growth across all of the species. To investigate plant selection and plant communities for calcareous grasslands on green roofs, seventeen forb species were planted to investigate the environmental tolerances of a range of species and to explore patterns of plant growth and flowering performance at the community and individual species level. Deeper substrate depth, the Limestone-based substrate, supplementary watering, and fertiliser addition tended to support significantly higher plant abundance, growth, structural characteristics, and flowering performance of the plant community. Some of individual species, however, showed different responses. Watering was an important factor regarding plant establishment and growth, especially with substrates of shallower depth. A 50 mm deep substrate is not suitable for satisfactory plant growth without additional watering; Supplemental watering produced statistically similar plant growth in the shallower substrate to that of the deeper substrate without it. The minimum substrate depth should be at least 100 mm to support good growth of the species on a green roof. Most species did not show significant difference in plant growth and performance between 100 mm and 200 mm depth. All the species in the Limestone-based substrate had a higher abundance rate, and the Limestone-based substrate produced significantly greater plant growth than the Zinco substrate. Additional fertiliser resulted in greater plant abundance and growth but there was a tendency for plant growth to be very vigorous. Hypochaeris radicata and Leucanthemum vulgare showed the greatest abundance under drought conditions in the shallow substrate depth. Overall, C. glomerata and H. nummularium across all treatments in a standard commercial green roof substrate without fertiliser addition, and P. officinarum and P. veris across all treatments including the additional fertiliser treatment were not effective green roof plants under the given conditions of the experiment. Across all experimental treatments except for the additional fertiliser treatment, the one legume in the experiment (Lotus corniculatus) tended to dominate over the 2-year period.

Over the last decade there has been a worldwide increase in the use of retractable roofs for stadia. This increase has been based on the flexibility and better economic performance offered by venues featuring retractable roofs compared to those with traditional fixed roofs. With this increased interest an evolution in retractable roof systems has followed. This dissertation is concerned with the development of concepts for retractable roof systems. A review is carried out to establish the current state-of-the-art of retractable roof design. A second review of deployable structures is used to identify a suitable retractable structure for further development. The structure chosen is formed by a two-dimensional ring of pantographic bar elements interconnected through simple revolute hinges. A concept for retractable roofs is then proposed by covering the bar elements with rigid cover plates. To prevent the cover plates from inhibiting the motion of the structure a theorem governing the shape of these plate elements is developed through a geometrical study of the retractable mechanism. Applying the theorem it is found that retractable structures of any plan shape can be formed from plate elements only. To prove the concept a 1.3 meter diameter model is designed and built. To increase the structural efficiency of the proposed retractable roof concept it is investigated if the original plan shape can be adapted to a spherical surface. The investigation reveals that it is not possible to adapt the mechanism but the shape of the rigid cover plates can be adapted to a spherical surface. Three novel retractable mechanisms are then developed to allow opening and closing of a structure formed by such spherical plate elements. Two mechanisms are based on a spherical motion for the plate elements. It is shown that the spherical structure can be opened and closed by simply rotating the individual plates about fixed points. Hence a simple structure is proposed where each plate is rotated individually in a synchronous motion. To eliminate the need for mechanical synchronisation of the motion, a mechanism based on a reciprocal arrangement of the plates is developed. The plate elements are interconnected through sliding connections allowing them mutually to support each other, hence forming a self-supporting structure in which the motion of all plates is synchronised. To simplify the structure further, an investigation into whether the plate elements can be interconnected solely through simple revolute joints is carried out. This is not found to be possible for a spherical motion. However, a spatial mechanism is developed in which the plate elements are interconnected through bars and spherical joints. Geometrical optimisation of the motion path and connection points is used to eliminate the internal strains that occur in the initial design of this structure so a single degree-of-freedom mechanism is obtained. The research presented in this dissertation has hence led to the development of a series of novel concepts for retractable roof systems.