Editorial

Regular papers

The first paper, ‘Prestress multi-objective optimisation method of the large opening cable dome with rigid inner ring’ by Jiang Cao, Mingliang Zhu, Jin Wang and Shilin Dong, addresses the challenge of prestress design in cable domes with rigid inner rings. The authors develop a surrogate model of structural response based on a Backpropagation (BP) neural network, and establish a nonlinear mapping between prestress levels and both structural displacements and support reactions. This approach reduces the need for repeated finite element analyses during the optimisation process. Building on this model, the study employs an Artificial immune algorithm (AIA) and an improved Genetic–artificial immune algorithm (GA-AIA) within a Pareto-based multi-objective framework in order to consider vertical displacement, support reaction and prestress levels at the same time. The results show that the proposed neural network surrogate model provides high accuracy and good computational efficiency, and that the optimisation strategy offers reliable global search capability and strong potential for engineering application in the design of large opening cable domes.

The second paper, ‘Structural performance assessment of stochastic fractal grid-shell structures using different recursive generation algorithms’ by Yaser Shahbazi and Mahsa Abdkarimi, explores the structural potential of fractal geometries in grid-shell design. Fractal patterns are generated using three strategies: a fully stochastic approach, a deterministic approach with constant ratios in all iterations and a deterministic approach with independent ratios in each iteration. For comparison, a conventional grid-shell with square cells is also considered. The planar patterns are mapped onto spherical, hyperboloid and hyperbolic surfaces to form grid-shell structures. Using both single and multi-objective optimisation with structural mass and maximum deflection as the principal quantities to be minimised, the authors show that fractal grids, in particular those created by the third strategy, can lead to lightweight and efficient structural systems under both symmetric and asymmetric loading conditions. Comparisons with conventional square grid-shells confirm the advantages of fractal configurations in terms of mass, and in the distribution of stresses and deflections.

The third paper, ‘Configuration research and model practice on six-bar tetrahedral cylindrical tensioned stringed lattice shells’ by Jiangye Fu, Feng Miao, Shilin Dong, Jianyong Hu, Jianqi Chen and Weigang Chen, introduces and investigates a new six-bar tetrahedral tensioned stringed cylindrical lattice shell. Based on rhombic projection plane six-bar tetrahedral units, the authors propose a self-balancing structural system in which horizontal thrust at the supports is balanced by tension in added stringed elements. This leads to a more favourable internal force distribution while retaining the benefits of standardised design, industrial production and prefabricated construction. A parameterised modelling program with visualisation is developed and used to analyse the configuration of the structure, and its completeness and effectiveness are verified. The construction path of the structure is studied. On the basis of a test model of a six-bar tetrahedral cylindrical lattice shell, a tensioned stringed test model is built by adding struts and steel tie rods and by changing the bearing properties along the span direction from fixed bearing to sliding bearing. Static tests confirm the reliability of the proposed system.

In memory of Professor Hoshyar Nooshin: Futures of spatial structures

This issue continues the In Memory of Professor Hoshyar Nooshin: Futures of Spatial Structures series, which presents contributions from recipients of the Pioneers’ Award who reflect on the future of spatial structures and related design approaches.

The paper ‘ENDLESS FORMS; Future of Production’ by Haresh Lalvani (Pioneers’ Award 2002) extends the discussion of form and fabrication into the area of mass-customised production. The AlgoRhythms project on curve-folded sheet metal provided a model for the industrial production of mass-customised designs of simple architectural products such as columns, walls and ceilings. This work was extended to mass-customisation of emergent forms, illustrated by Morphing Platters, which are presented in this paper. Based on a new automaton, the project shows how a very large set of different designs can be produced at the same cost as identical designs, thereby challenging the traditional principle of economy of scale that has shaped industrial production since the Industrial Revolution. The example also demonstrates conservation of mass in design, since each platter has the same weight and the algorithm redistributes the same mass within the same area.

At a conceptual level, the paper proposes mass-customisation founded on three twin phenomena: design–production, infinity–eternity and unity–diversity. These are suggested as an overarching strategy for the generation of ‘endless forms’, a term adopted from Darwin’s classic work on evolution. The production of endless forms, without limit in time, is presented as an aspirational upper bound for the physical production of our designs. Combined with another triad, form–material–process, the author envisages an integrated universal design tool which could support continuous creativity in the making of physical objects and structures. This line of thought resonates strongly with Professor Nooshin’s lifelong interest in creativity of structural forms and in future directions for spatial structures.

In memory of R. Sundaram

This issue also records with deep regret the passing of R. Sundaram on 21 December 2025. As Chairman and Managing Director of Sundaram Architects Pvt. Ltd., he combined structural innovation with architectural clarity over a professional career of more than fifty five years. Educated at the Massachusetts Institute of Technology during a period of significant experimentation in structural engineering, he promoted the view that gravity is a collaborator in design rather than an adversary.

Sundaram was a pioneer in India in the use of precast and pre-stressed concrete, large concrete hypar shells, long span reinforced concrete and steel folded plate roofs, inverted umbrella and cylindrical shells, pre-cast pre-stressed folded plates and segmental bridges. From his first shell structure in 1961 to his work in 2018, he consistently showed how repetitive formwork and intelligent prefabrication can be used to produce economical, efficient and visually refined long span structures. His contributions extend across a wide range of building and infrastructure types, including industrial projects, information technology campuses, biotechnology facilities, shopping malls, sports stadia, educational campuses, chemical plants, flyovers and subways, multi-storey car parks, auditoria, convention centres, hospitals, housing and townships.

At international level, Sundaram was closely associated with the International Association for Shell and Spatial Structures (IASS) and the Structural Engineers World Congress (SEWC). He attended their annual international conferences from 1982 onwards as a keynote and invited speaker, and successfully organised a number of international conferences in India and abroad. He served as President of SEWC from 2007 to 2011, and was re-elected for two further terms until 2019, becoming the first person from India to hold this position.

His work received wide recognition through many honours and awards, including the Eduardo Torroja Medal of the IASS, the SEWC Roland Sharpe Medal, the CIDC Vishwakarma ‘Achievement Award for Industry Doyen’, and a life-time honorary membership of the Prestressed and Precast Concrete Society in Singapore. Princeton University published a thesis by Meggie June Betancourt on ‘R. Sundaram & Modern Thin Shell Concrete Structures’, which records aspects of his contribution to thin shell design. He also held leadership positions in professional bodies such as the Association of Consulting Civil Engineers (India) and the Indian Concrete Institute, and was active in organisations including the American Concrete Institute and the American Society of Civil Engineers. In addition, he was a Fellow of the Association of Consulting Civil Engineers (India), the Institution of Engineers (India) and the Indian Institution of Bridge Engineers. He was a permanent member of the International Advisory Board of the International Association for Shell & Spatial Structures (IASS).

Beyond these achievements, Sundaram gave long and valuable service as a member of the editorial board of the International Journal of Space Structures. I first met him at the Annual Symposium of the International Association for Shell and Spatial Structures in 2010 in Shanghai, where his energy, generosity and commitment to the advancement of our field were immediately apparent, Figure 1. He will be remembered as a visionary engineer-architect who helped to raise the profile of shell and spatial structures in India and across the world.

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Figure 1.

R. Sundaram at the annual symposium of the international association for shell and spatial structures IASS2010 in Shanghai, China.