When employing the strut-and-tie modelling (STM) method in the conceptual design of reinforced concrete structures, a suitable strut-and-tie (ST) model indicating load transfer mechanisms first needs to be identified. Topology optimization (TO) methods have frequently been used for this purpose. However, although TO methods employing either a ground-structure or a continuum-based TO approach can be used, the performance and effectiveness of these two methods have not been systematically investigated and compared. To obtain a better understanding of the characteristics of both methods, a systematic comparison procedure is proposed to investigate the generation process and the resulting ST designs. Three aspects, relating to structural performance, economic issues, and method applicability are considered in the comparison, with six metrics formulated to quantify these aspects. Based on investigation of designs for three reinforced concrete elements incorporating typical discontinuity regions (two 2D cases and a 3D case), the performance of the two methods is assessed. It is found that both methods result in safe and efficient ST designs, with comparable structural performance, while some differences in terms of computation time and usability are observed.

Failure of tall slender masonry structures during earthquakes often involves partial collapse of the structure well-above ground level. Consequently, the elastic response of the structure needs to be considered, which often requires modal analysis using finite element models — the generation of which can be labour-intensive and time-consuming. This paper presents a new integrated modelling approach which combines finite element analysis with rocking dynamics to model the seismic response of complex structural geometries in a computationally-efficient manner. The modelling strategy is implemented within the open-source computational framework COMPAS and is incorporated within the broader framework of a tool being developed for the seismic collapse assessment of masonry structures. The framework of this tool is first outlined, and the utility of the new modelling approach then demonstrated through application to the seismic assessment of a three historic masonry towers in North-Eastern Italy. The importance of accounting for elastic amplification effects, as well as the influence of varying boundary conditions on the dynamic response, is also illustrated.

This paper describes the structural design, digital fabrication and construction of KnitCandela, a free-form, concrete waffle shell with KnitCrete, a falsework-less formwork approach using a custom prefabricated knitted textile as multi-functional, structural shuttering layer and a form-found cable net as the main load-bearing formwork. The digitally designed and fabricated textile provided integrated features for inserting and guiding elements such as cables and inflatables that helped shape the sophisticated mould. With a total weight of only 55 kg, the 50 m² formwork was easy and compact to transport. On site, the formwork was tensioned into a timber and steel rig, the pockets were inflated, and then coated with a thin layer of custom-developed, fast-setting cement paste. This paste served as a first stiffening layer for the textile, minimising the formwork's deformations during further concrete application. Fibre-reinforced concrete was manually applied onto the formwork to realise a 3 cm-thick shell with 4 cm-deep rib stiffeners. The novel approach, for the first time applied at architectural scale in this project, enables the building of bespoke, doubly-curved geometries in concrete, with a fast construction time and minimal waste, while also reducing the cost and labour of manufacturing complex parts.

A novel formwork system is presented as a material saving, labour reducing and cost-effective solution for the casting of bespoke doubly curved concrete geometries. The approach uses a custom knit technical textile as a lightweight stay-in-place formwork with integrated solutions for the insertion of additional elements, and is fabricated as a nearly seamless fabric. Using weft knitting as the textile formation technique minimises the need for cutting patterns, sewing, welding or gluing, when compared to conventional weaving and gives the possibility to integrate channels, openings, have varying widths and directional material properties, thus broadening the geometric design space. The system has been tested through a small-scale concrete footbridge prototype, built using a pre-stressed hybrid knitted textile and a bending-active structure that acted as a waste-free, stay-in-place, self-supporting formwork. Through the gradual buildup of strength in thin layers of concrete, formwork deformations during casting were minimised. This allowed for low tensioning levels of the fabric and the possibility to use higher pressure (e.g. during shotcreting) in applying the subsequent concrete without intermediate support from below. The computational design and fabrication of the knitted textile formwork included integrated channels for the insertion of bending-active rods, tensioning ribbons and features for controlling the concrete casting. The analysis and process of increasing the stiffness of the lightweight and flexible formwork is presented. The hybrid approach results in an ultra-lightweight formwork that is easily transportable and significantly reduces the need for falsework support and scaffolding, which has many advantages on the construction site.