Steel and Composite Steel-Concrete Structures
Reinforced Concrete Structures
Partially Bonded Non-metallic Prestressing Tendons
Expert Systems for Prestressed Concrete Bridge Design
Parallel-lay Rope Terminations
Very Long Span Bridges
Lateral Stability of Precast Concrete Beams
Polyester and Aramid Fibre Properties
Non-metallic Reinforcement for Concrete
Conceptual Methods for Structures and Mechanisms
Structural Vibrations and Control
Mechanics of Masonry Construction
Interdisciplinary Design for the Built Environment
Dr R.E. McConnel
A project to investigate the use of asymmetric hot-rolled sections and deep-troughed concrete-filled floors ("slimfloor") for large-span buildings continues. A stub-girder arrangement is being used for the main beams in order to extend the span range beyond the present practical limitation of 6 m. A full scale 13.2 m span test specimen is currently being erected and will in due course be tested to failure.
A study continues extending previous work on composite space-truss systems to include light-weight shell-like large-span roof structures. To date, an appropriate 2-noded beam-column finite-element, that can model member buckling in conjuction with both initial imperfections and a range of lateral loads within the length of the element, has been developed. This finite element is currently being calibrated against some small-scale model roof domes, before being used for the analysis of some large-span roofs.
Dr C.T. Morley
Some experimental evidence has been published(G13) on the intriguing `self-sealing' property of concrete, i.e. the marked decrease of permeability to water of certain types of concrete during the course of a standard permeability test spread over some days. Reverse flow tests, tests on fully-hydrated concrete, and tests with propanol permeant eliminated various proposed explanations of this self-sealing. The most significant mechanism seems to be dissolution and redisposition of alkalies, occurring mainly in specimens dried-out before testing.
Research has continued on possible simplified approaches to the analysis of structures made of materials exhibiting marked strain-softening. It appears that considerable progress can be made using the Galerkin method, which has recently been applied with success to some square concrete slabs with arching action due to various forms of lateral restraint at the boundaries.
Dr C.J. Burgoyne
The project on beams prestressed with partially bonded non-metallic tendons has now been completed. It showed that it is possible to achieve high strength (normally associated with fully bonded systems), and high rotation capacity (normally associated with unbonded systems), by judiciously debonding the tendons. This was achieved in two ways; by alternately bonding and debonding the tendon along its length, or by coating the tendon with a surface layer of known, low, shear strength. The tendons were made from aramid fibres, in the form of pultrusions or braided rods. Associated work has been investigating the bond behaviour between the rods and the concrete, since the mechanism of bond breakdown is critical to the behaviour of the tendons [Lees, J.M., PhD dissertation, see Section IV].
Dr C.J. Burgoyne
The development of an expert system to design prestressed concrete bridges continues as a PhD project by J. Sundaram. The system now takes due account of thermal and creep effects, and also takes into account additional effects caused by the construction sequence. It is now possible to design quite complex structures, with different configurations, in short periods of time; which allows designers to explore alternatives. Hitherto, the calculations were so complex that the first valid solution would have been accepted. Wherever possible, the system has been configured in such a way that the fundamental behaviour of prestressed concrete structures is built-in. Only when it is not possible for the system to calculate a value does the designer have to specify a value; and the designer is then given guidance as to the range of allowable values, and why a particular parameter has to be chosen. In this way, the designer is free to choose the optional parameters, leaving the computer to do the drudgery. Values calculated by the system can be overridden by the designer if necessary, provided the structural criteria remain satisfied.
Dr C.J. Burgoyne
The behaviour of parallel-lay rope terminations has been studied. The transverse properties of the fibres have been measured, as have their friction and abrasion characteristics. These have then been combined with the results of a complex, non-linear finite element analysis, which has taken account of the relative motion of the barrel, fibre and spike in the terminations. The result has been predictions about the amount of abrasion that is likely to take place under different operating conditions; and these have been correlated with fatigue test data obtained elsewhere. The results have shown that the behaviour of the terminations can now be understood, and the techniques will allow the effects future changes in termination geometry to be predicted [Brown, I.F., PhD dissertation, see Section IV].
Dr C.J. Burgoyne
Mr F.A McRobie
Work has continued on the dynamic stability of very-long span bridges (of spans over 2km) under wind loading. An improved model has been developed to examine the wind-induced oscillation behaviour of such highly flexible bridges in both twist and vertical motions: it uses four coupled oscillators. Two of these relate to the structural displacements in plunge and twist, while the other two relate to the behaviour of the leading-edge and trailing-edge wakes. Active control measures such as moving winglets, and passive damping systems such as tuned mass dampers, have been included in the model to investigate their effectiveness in mitigating dangerous oscillations of the structure.
Work is also in progress assessing the applicability of computational fluid dynamics (CFD) to the design of long-span bridges. Using a fully-coupled fluid-structure finite element code, the various aeroelastic instabilities such as flutter and vortex-induced oscillations can be modelled in the time domain, providing detailed insights to supplement wind-tunnel tests and simpler mathematical descriptions.
Dr C.J. Burgoyne
A study of the stability of long precast concrete beams is underway. These beams can become unstable under their own self-weight, especially when lifted, since in this configuration the restraint to lateral deflection is removed, and a toppling behaviour can result. Also of interest is the transportation problem, when the beam is supported on turntables at both ends. In this configuration, the primary problem is due to lateral loads caused by uneven ground or by centrifugal forces during cornering. The study has included the effects of initial imperfections, and has investigated the minor axis bending stresses that are induced. Design recommendations are being formulated.
Dr C.J. Burgoyne
The long-term properties of polyester and aramid fibres are being studied, with a view to drawing up safe levels of load for long-term structural applications. In the case of polyester, the uses are normally as soil-reinforcement, while for aramids, the normal uses would be as prestressing tendons. In both cases, a proper understanding of the stress-rupture, creep and relaxation properties can have a significant impact on the economics of using such materials.
Dr C.J. Burgoyne
Although the normal use of non-metallic systems in concrete will be as prestressing tendons, they can also be used to reinforce against shear, and to provide restraint against compressive failure. Both end uses require modifications to existing wisdom about structural behaviour.
In the case of shear reinforcement, yielding of the links can no longer be relied on, which means that the plasticity theorems no longer hold. This, in turn, means that an explicit relationship is required between the shear deformation and the forces in the links. As with the partially-bonded tendons discussed above, the bond behaviour is critical, since this controls the way in which the elements move relative to one another. A model of the equilibrium of the "tooth" of concrete between shear cracks is being developed.
The ability of systems based on fibres to provide restraint against compressive failure is well-known; but it has been ignored since the current design philosophy is that "under-reinforced" failure is desirable, so that the tendon fails before the concrete. But if beams are to be built with non-metallic tendons, and those tendons are brittle, then that implies that "over-reinforced" failure, where the concrete crushes before the tendon snaps, is a good thing. Thus, significant increase in ductility can be achieved by providing hoop reinforcement in the compression zone. The effect is not to increase the strength significantly, but rather to enhance the strain capacity, so that significant amounts of work are done within the concrete when it crushes.
Dr C.R. Middleton
Dr C.T. Morley
Dr T.J. Ibell
Dr A. Blackmore
Mr P. Fidler
Research on bridge assessment is continuing, with emphasis on the development and evaluation of collapse analysis methods for assessing the strength and safety of concrete bridges. The COBRAS generalised yield-line collapse-analysis program, developed within the Group, has been used to assess the strength of over 20 concrete bridges as part of the national bridge assessment programme. Very substantial savings have resulted from the more realistic predictions of strength that have been obtained using this approach. Research is on-going in validating this analysis method for a variety of bridge and load configurations, and extending the capabilities of this novel analysis program. Model tests examining ductility requirements in concrete bridge slabs and the effects of reinforcement corrosion on strength have also been conducted.
A major research contract for the study of shear in beam-and-slab concrete bridges is nearing completion. Five half-scale bridge models have been tested in the laboratory to verify newly developed plasticity solutions for the collapse behaviour of this form of bridge(G17,G18,G19). A study comparing the behaviour predicted for these structures using plastic analysis and non-linear finite-element methods has been completed. Recommendations for the application of plastic analysis to the evaluation of shear capacity of concrete beam-and-slab bridges are being developed as a result of this work.
A collaborative research project aimed at incorporating whole-life costing considerations into bridge assessment criteria, and in particular making allowance for the effects of material deterioration and actual vehicle loads on structural strength and safety, has now been completed(G2,G28). On the basis of this work, a major new research contract has been awarded to the Group to extend and implement the findings of the previous study. This project is part of an ongoing research effort aimed at developing and applying reliability analysis methods in bridge engineering and bridge management. A novel software package combining yield-line methods of structural assessment with reliability analysis has been developed, and it is being used to provide a rational method for ranking existing bridges in order to identify those most in need of strengthening or replacement.
An investigation into the use of non-destructive testing techniques for determining the location and degree of corrosion in the reinforcing bars of concrete structures is continuing in collaboration with an industrial partner.
Dr S. Pellegrino
Dr S.D. Guest
Dr Z. You
Last year's discovery of "generalized angulated elements" and "multiangulated elements" has been followed by the publication of a paper explaining this invention(G32). An undergraduate student, P.E. Kassabian, who did his final-year project on a retractable structure based on this invention has been awarded the first prize in the ICE Student Paper Competition. A highlight of Kassabian's study was his discovery, and analytical proof, that a structure whose two-dimensional layout consists of a tessellation of similar rhombuses can be supported on fixed points. He presented his work at an international conference(G20).
Work has continued on new concepts for deployable reflector antennas. A paper has been published on the recently-proposed concept of cable-stiffened pantograph rings that support a mesh surface(G31). An undergraduate student, B. Tibbalds, has proposed a new folding concept for rigid-surface reflectors. His project report won an I.Mech.E. student prize, and the work will be presented at next year's AIAA Structures, Structural Dynamics, and Materials Conference, in Long Beach, California.
Following work on the deployment simulation of deployable solar arrays(G22), a study of the interaction between such structures and the gravity-compensation system, used for ground testing, is being investigated. This work is supported by the European Commission TMR programme.
A new deployment system for rigid-panel structures, such as solar arrays or synthetic aperture radar panels, has been tested(G27) on behalf of Matra Marconi Space. Two papers on the shape control of prestressed truss structures have been published(G21,G29). A new foldable structure concept has been published(G30).
Following the success of last year's deployable structure model exhibited in New York and Istanbul, the Deployable Structures Group were invited to display two models at the exhibition "Les Ingenieurs du Siecle" that has marked the closure for refurbishment of the Pompidou Centre, Paris. The structures that were displayed were a pantographic deployable mast and a new flexible ring structure, both automatically driven by microprocessor-controlled electric motors.
On a personal note, two members of the Group received awards that enable to further develop their work on deployable structures. Dr You was awarded a five-year Advanced Research Fellowship from the Royal Academy; and Dr Pellegrino was awarded a Foresight Award from the Royal Academy of Engineering.
The Deployable Structures Group will be hosting an international symposium on Deployable Structures: Theory and Applications, in September 1998. The meeting is co-sponsored by the International Union of Theoretical and Applied Mechanics (IUTAM) and the International Association for Shell and Spatial Structures (IASS).
Work has continued on the analysis of symmetric structures and mechanisms. A new technique, based on the application of group representation theory to the force method has been developed, and has been successfully employed in the analysis of overconstrained mechanisms.
Work has continued on the analysis of constrained multi-body systems. A variable partitioning technique has been formulated to simplify the integration of the equations of motion of these systems(G11).
Dr S. Pellegrino
The design of the shape-memory alloy actuator developed last year has been improved, using a new way of providing thermal and electrical insulation for the Nitinol wire that drives the actuator. A prototype of the new design has been manufactured in the Departmental Workshops, and preliminary tests have been very promising. A user's guide to the design and simulation of actuators based on Nitinol wires has been presented at an international conference(G16). Preliminary studies of Nitinol rods in torsion have begun.
Work on stick-slip piezoelectric actuators has continued. During the last year, an experimental characterization of the non-linear interaction between stress, electric field, and elastic modulus of piezo-ceramics has been carried out. Work on two-degree-of-freedom actuators, which combine linear and rotary motion, has begun.
Dr S. Pellegrino
Work has continued on the non-linear vibration of thin-walled open-section cantilever beams. During the last year, a non-linear relationship has been derived between curvature and twist and the associated stress resultants, using the finite element package ABAQUS. This relationship will be used to set up a dynamical model that attempts to capture the modal interaction that is observed experimentally.
An actively controlled six-degree-of-freedom alignment control system, mounted at the tip of a flexible space structure, has been developed. Its performance under quasi-static and dynamic disturbances has been examined both experimentally and analytically(G7). The system consists of six stick-slip inertial actuators, forming a Stewart platform.
Mr F.A. McRobie
Research is being conducted into the dynamical behaviour of nonlinear elastic systems, focusing on the application of dynamical systems theory(G1). In collaboration with Dr J Lasenby, the use of Clifford Algebra as the appropriate mathematical framework in which to construct a large-rotation rod theory suitable for finite-element implementation has been developed(G24,G25). Work has also been undertaken on the development of dimension-reduction algorithms for extracting low-dimensional dynamic models from massive numerical simulations, applying techniques of inertial manifold approximation.
Professor C.R. Calladine
Work continues on the buckling of thin cylindrical shells under compressive load. The immediate motivation has been the structural performance of thin-walled silo shells. Two separate lines of enquiry have produced results which seem to suggest that, at last, a paradigm shift is due in this field. Tests on a Melinex model shell of diameter 0.9 m have demonstrated, in spite of the deliberate introduction of massive geometrical imperfections in the form of dents and dimples, load-carrying capacity in the upper range of buckling loads to be expected statistically on the basis of many previous tests reported in the literature. A distinctive feature of the experiments was the end-fitting arrangements, which provided less axial restraint than is usual in such tests, and which indeed constituted something approaching static determinacy.
A second set of experiments by P. Mandal was on the self-weight buckling of open-top small-scale silicone-rubber cylinders. Again, there was a clear absence of "scatter" in the measured buckling heights; and again that may be attributed to the static determinacy of the setup.
A third set of experiments, on the effect of localised inelastic damage on thin-walled steel shells has shown that under increasing axial load, dimples grow out of the damaged zones, and that they enlarge in a stable fashion until collapse occurs when a critical size has been reached(G12). Here, also, the ends of the shell were not strongly restrained in the axial direction.
A detailed investigation has been completed by M.ED. El-Mously into the modes and frequencies of natural vibration of hyperboloidal cooling-tower shells.
Professor C.R. Calladine
Professor A.C. Palmer
A laboratory-scale study of lateral thermal buckling of pipelines on the sea-bed is being conducted. The pipe is modelled by a strip of silicone rubber, and the thermal expansion of the pipe by a corresponding contraction of the expanded polystyrene bed, by means of long screws passing through it.
Interaction between the pipeline and the seabed is modelled by friction. The rig replicates in detail the local lateral buckling of pipelines in the seabed; and associated numerical work mimics closely the development of buckles as seen in the experiments. An interesting, and practically important, outcome of the work is that the localisation phenomenon turns out to be self-limiting, in the sense that the primary buckle lobe eventually stops growing as temperature increases, thereby throwing further lateral growth onto adjacent lobes. Ultimately, relatively few of the formally derived dimensionless groups of the problem are significant. Accounts of this work have been presented at two international conferences(G4,H2). [See also PETROLEUM ENGINEERING.]
Professor J. Heyman
Work continues on the application of structural mechanics to masonry construction. An assessment has been made of the fundamental frequency of vibration of masonry pinnacles, which are a central structural feature of Gothic architecture(G15). A paper has been written on a paradox raised by Hambly, in which the loads on individual legs of a four-legged stool may be higher than on those of a three-legged one. The paradox cuts across much of the conventional wisdom of structural engineers(G14).
Professor C.R. Calladine
Dr M.A. El Hassan
Investigations of the mechanics of double-helical DNA continue, at both local and global levels. A second edition of a textbook first issued in 1992 has been published(G5): it has been enlarged by the addition of two new chapters, one of which describes the detailed three-dimensional structural interaction between specific DNA and protein moieties.
Controversy continues over the validity of using "static" models of a molecule that is so small as to be under incessant thermal motion(G6). Static models do indeed have a good track record for correlating quantitative data on DNA obtained from experimental assays of many different kinds. Although a long, very slender object may be inherently flexible, its local behaviour need involve only very small strain: thus a length of garden wire may be used like string, while a short piece of the same wire is good as a nail.
The detailed, three-dimensional geometry of bending and twisting of the DNA double helix has been used to analyse a novel topological assay for the independent determination of both the bend and (un)twist angles imparted by the binding of the CAP protein(G23).
A long paper has been written(G9) on the sequence-dependent conformational rigidity and mobility seen in dinucleotide steps of naked DNA as found in single-crystal X-ray studies. The work makes use of detailed computational studies of electrostatic interactions between stacked base-pairs made by colleagues at Sheffield.
A geometrical analysis of the superhelical geometry of repeat-sequence DNA has been completed(G10). It is relevant to the interpretation of the anomalous mobility of DNA in electrophoretic gels, in terms of the conformational parameters of dinuncleotide steps having specific sequence.
A Turkish edition of a textbook on Plasticity has been published(G3).
The IDBE course is run jointly by the Department of Engineering and the Department of Architecture, under the auspices of the Cambridge Programme for Industry, which is a branch of the Board of Continuing Education. It is a part-time course lasting two years, and leading to the Master of Studies (M.St.) degree. The start-up funding for the course was provided by a generous grant from the Ove Arup Foundation; and that and the Quest Foundation continue to provide support in the form of student bursaries.
The course can trace its roots back to a conference on "Education for the Built Environment" that was held at Madingley Hall in 1991, and which highlighted the unfortunate consequences for our built environment of the practical compartmentalisation of the professions concerned : Engineers, Architects, Quantity Surveyors, Planners, etc. The course was set up as the first example of the new Cambridge part-time Master's degree course, with the first cohort of students starting in July 1994. The course involves a total of ten weeks of residence in Cambridge, and each period of residence involves lectures, case studies, design exercises, individual supervision and after-dinner talks on a wide range of topics in the built environment. Instruction is coordinated by Paul Kirby (Department of Engineering) and Giles Oliver (Department of Architecture); but there is a large and multi-disciplinary army of external lecturers and consultants who, in addition to about eight members of CUED staff, are involved in the various activities. The course has made strong links with the local authorities' planning and transportation officers, who are able to present real local problem-situations to the students.
In order to fulfil the requirements for the degree, the students are also required to complete a case-study, two essays and a dissertation in their own time.
The academic year 1996-97 was the second year for the 15 members of cohort 2 (members of Wolfson College) and the first year for the 17 members of cohort 3 (members of Peterhouse). Dr Robin Spence (Reader in the Department of Architecture) stood down as Course Director in December 1996, after three years in that position: in January 1997 Paul Kirby and Giles Oliver became Joint Course Directors.
The course structure and content and delivery are widely regarded as being excellent. But recruitment remains an up-hill struggle. More partial-bursaries are required in order to help with the establishment of the course in the eyes of the professions over the next few years. The precise structure of the course is currently under review.
G1. Baker, G., McRobie, F.A., Thompson, J.M.T. Implications of chaos theory for engineering science. Proceedings of the Institution of Mechanical Engineers, Part C, Journal of Mechanical Engineering Science, 211, (C5), 349-363 (1997).
G2. Blackmore, A., Middleton, C.R. Data collection report. In: Safety of Bridges: Proceedings, International Symposium, London (July 1996); Edited by P.C. Das, 203-222 (Thomas Telford, 1997).
G3. Calladine, C.R. Mühendislikte Plastisite. Translation into Turkish by E. Inan, E. Togrol, of Plasticity for Engineers. (Bilimsel ve Teknik Yayinlari Çeviri Vakfi, 1996).
G4. Calladine, C.R. Upheaval lateral buckling of submarine pipelines. Advances in Steel Structures, Proceedings, International Conference, Hong Kong (December 1996); Edited by S.L. Chan, J.G. Teng, II, 647-656 (Pergamon, 1996).
G5. Calladine, C.R., Drew, H.R. Understanding DNA: the Molecule and How it Works (2nd edition). (Academic Press, 1997).
G6. Calladine, C.R., Drew, H.R. A useful role for "static" models in elucidating the behaviour of DNA in solution. Journal of Molecular Biology, 257, 479-485 (1996).
G7. Darby, A.P., Pellegrino, S. Active alignment control of a payload using non-linear, long stroke actuators. Proceedings, IUTAM Symposium on Interaction between Dynamics and Control in Advanced Mechanical Systems, Eindhoven, the Netherlands (April 1996); Edited by D.H. van Campen, 91-100 (Kluwer Academic, 1997).
G8. Denton, S.R. The assessment of reinforced concrete bridge decks. Bridge Modification 2: Stronger and Safer Bridges: Proceedings, 2nd International Conference, Institution of Civil Engineers, London (November 1996).
G9. El-Hassan, M.A., Calladine, C.R. Conformational characteristics of DNA: empirical classifications and a hypothesis for the conformational behaviour of dinucleotide steps. Philosophical Transactions of the Royal Society of London, Series A, 355, (1722), 43-100 (1997).
G10. El-Hassan, M.A., Calladine, C.R. Curvature and torsion of infinitely repeating DNA sequences. Proceedings of the Royal Society of London, Series A, 453, (1957), 365-386 (1997).
G11. Guest, S.D. A variable partitioning technique for integrating constrained equations of motion in mechanism analysis. Multi-Body Dynamics: Monitoring and Simulation Techniques, Proceedings, 1st International Conference, Bradford (March 1997); Edited by H. Rahnejat, R. Whalley, 191-200 (Mechanical Engineering Publications, 1997).
G12. Hambly, E.T., Calladine C.R. Buckling experiments on damaged cylindrical shells. International Journal of Solids and Structures, 33, (24), 3539-3548 (1996).
G13. Hearn, N., Morley, C.T. Self-sealing property of concrete - experimental evidence. Materials and Structures/Matériaux et Constructions, 30, (201), 404-411 (1997).
G14. Heyman, J. Hambly's paradox: why design calculations do not reflect real behaviour. Proceedings of the Institution of Civil Engineers, Civil Engineering, 114, (4), 161-166 (1996).
G15. Heyman, J. The vibration of masonry pinnacles. In: Structural Studies, Repairs and Maintenance of Historical Buildings, Proceedings, 5th International Conference, STREMAH V, San Sebastian, Spain (1997); Edited by S. Sánchez-Beitia, C.A. Brebbia, 429-436. International Series on Advances in Architecture 3 (Computational Mechanics Publications, 1997).
G16. Huang, W., Pellegrino, S. Nitinol actuators for deployable space structures. Proceedings, International Conference on Shape Memory and Superelastic Technologies, Pacific Grove, CA, USA; Edited by A. Pelton (March 1997).
G17. Ibell, T.J., Morley, C.T., Middleton, C.R. The assessment of shear in existing concrete bridges. Proceedings, FIP/IABSE Conference on the Concrete Way to Development, Johannesburg, South Africa, 529-536 (March 1997).
G18. Ibell, T.J., Morley, C.T., Middleton, C.R. An experimental investigation into shear in large-scale concrete beam-and-slab structures. Cambridge University Engineering Department Technical Report CUED/D-STRUCT/TR.165 (October 1996).
G19. Ibell, T.J., Morley, C.T., Middleton, C.R. A generalised collapse analysis method for concrete bridges. Cambridge University Engineering Department Technical Report CUED/D-STRUCT/TR.166 (October 1996).
G20. Kassabian, P.E., You, Z., Pellegrino, S. Retractable structures based on multi-angulated elements. Proceedings, International Colloquium on Structural Morphology: Towards the New Millenium, Nottingham; Edited by J.C.Chilton, et al, 92-99 (August 1997).
G21. Kawaguchi, K., Hangai, Y., Pellegrino, S., Fuyura, H. Shape and stress control analysis of prestressed truss structures. Journal of Reinforced Plastics and Composites, 15, (12), 1226-1236 (1996).
G22. Kumar, P., Pellegrino, S. Deployment and retraction of a cable-driven rigid panel solar array. Journal of Spacecraft and Rockets (AIAA), 33, (6) 836-842 (1996).
G23. Lutter, L.C., Halvorson, H.R., Calladine, C.R. Topological measurement of protein-induced DNA bend angles. Journal of Molecular Biology, 261, 620-633 (1996).
G24. McRobie, F.A., Lasenby, J. Geometric algebra for engineering mechanics. Proceedings, 2nd Institute of Mathematics and its Applications (IMA) Conference on Mathematical Education of Engineers, Loughborough (April 1997).
G25. McRobie, F.A., Lasenby, J. Simo-Vu Quoc rods using Clifford algebra. Cambridge University Engineering Department Technical Report CUED/D-STRUCT/TR.169 (1997).
G26. Pamplona, D.C., Calladine, C.R. Aspects of the mechanics of lobed liposomes. Transactions of the ASME, Journal of Biomechanical Engineering, 118, (4), 482-488 (1996).
G27. Seffen, K.A., Pellegrino, S. Deployment of a rigid panel by tape-springs. Cambridge University Engineering Department Technical Report CUED/D-STRUCT/TR.168 (1997).
G28. Thoft-Christensen, P., Jensen, F.M., Middleton, C.R., Blackmore, A. Revised rules for concrete bridges. In: Safety of Bridges: Proceedings, International Symposium, London (July 1996); Edited by P.C. Das, 175-188 (Thomas Telford, 1997).
G29. You, Z. Displacement control of prestressed structures. Computer Methods in Applied Mechanics and Engineering, 144, (1-2), 51-59 (1997).
G30. You, Z. A pantographic deployable conic structure. International Journal of Space Structures, 11, (4), 363-370 (1996).
G31. You, Z., Pellegrino, S. Cable-stiffened pantographic deployable structures. Part 2: mesh reflector. AIAA Journal, 35, (8), 1348-1355 (1997).
G32. You, Z., Pellegrino, S. Foldable bar structures. International Journal of Solids and Structures, 34, (15), 1825-1847 (1997).
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