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Mainstream approaches to design spatial architectural forms that are structurally relevant consist either in adapting well-known and catalogued conventional types or in searching for close-to-optimum solutions of well-defined problems. Few means exist to explore structural forms detached from these routines. The approach in this paper generates diverse non-triangulated structural topologies that do not result from optimization procedures. The process incrementally transforms interim networks of bars and forces by means of a parametric policy (–) that maintains the static equilibrium of the network at every single step, (–) that ensures growth of the network within specified (non-)convex geometric boundaries, and (–) whose high-level abstract description controls all design parameters. The successive policy application aims at decreasing the number of interim forces while increasing the number of nodes and bars in compression or tension. The entire process ends when no interim force exists anymore, which is always achievable thanks to the permanence of the static equilibrium condition. From a designer perspective, the approach opens up the generative design black box by providing geometrical and topological control and partial automation of the generation process, while not resorting to common topology patterns – e.g. triangulated bar networks. This paper describes the conceptualization and its implementation into a computational framework, named Policy-based Exploration of Equilibrium Representations (PEER). It illustrates the potential of the approach to unveil unprecedented, unexpected, but statically-valid, structural topologies. Opportunities for further development are eventually discussed. • Generate bar networks in static equilibrium within specified non-convex geometric bounds. • Generation through a parametric policy to allow broader design space exploration. • Policy syntax, incepted and implemented by the authors, integrates static equilibrium. • This integration frees generated networks from equilibrium imposing post-processing. • The policy only considers geometric bounds to generate topologies for any given loads. • The network topology is not known a priori. Generating numerous topologies is the goal. • Generated networks not deemed optimum; rather inspire conceptual structural design. [ABSTRACT FROM AUTHOR]

This paper introduces computational techniques to support architects and structural designers in the shaping of strut-and-tie networks in static equilibrium. Taking full advantage of geometry, these techniques build on the reciprocal diagrams of graphic statics and enhance the interactive handling of them with two devices: (1) nodes-considered as the only variables-are constrained within Boolean combinations of graphic regions, and (2) the user modifies the diagrams by means of successive operations whose geometric properties do not at any time jeopardize the static equilibrium. This constructive approach enables useful design-oriented capabilities: a graphical control of multiple solutions, the direct switching of the dependencies hierarchy, the execution of dynamic conditional statements using static constraints, the computation of interdependencies, and coordinate-free methods for ensuring consistency between certain continuums of solutions. The paper describes a computer implementation of these capabilities. [ABSTRACT FROM AUTHOR]

• Challenges when allocating environmental impacts of reused building components. • Case study of a commercial building with reused components. • Comparison of design with upstream reuse and design for downstream reuse. • Comparison of six impact allocation methods over three typical life cycles. • Environmental assessment issues when applying circular economy principles in construction. The building industry is responsible for 35 % of all solid waste in Europe and more than a third of greenhouse gas (GHG) emissions. To address this, applying circular economy principles to the building sector is crucial, for example by reusing building elements from demolition sites rather than extracting and producing new materials. However, most current life-cycle assessment (LCA) tools are not appropriate to evaluate the environmental impact of a building when its components originate from prior buildings and/or will be used in future unknown ones. Still, robust measurement is needed to demonstrate the benefits of reuse towards environmentally sustainable cities. This paper compares existing methodologies to quantify the global warming potential (GWP, expressed in kg CO2e /unit) of recycled/recyclable and reused/reusable products, selected within widely recognised standards, rating schemes, and academic studies, such as the cut-off method, the end-of-life method, the distributed allocation (PAS-2050) method, the Environmental Footprint method, the Degressive method and the SIA 2032 method. Based on these recognised approaches for assessing the GWP of products, new equations are written and applied to buildings with reused/reusable materials for each of the methods. The Kopfbau Halle 118 building (Winterthur, CH, 2021), which is designed with reclaimed elements from local demolition sites, is chosen as a case study. Discrepancies in LCA methods are highlighted by applying them to three different life cycles corresponding to the first, intermediate, or final use of building components. This paper shows that current quantification methods to assess reuse give wide-ranging results and do not address the full spectrum of the reuse practice, that their boundaries are too limited, and that a number of critical features are currently hardly quantifiable, such as embedded use value, versatility, storage and transformation impacts, user-owner separation, dis/re-mountability, or design complexity. [ABSTRACT FROM AUTHOR]

The study explores an original idea that responds to the urgent need to reduce the detrimental environmental impacts of load-bearing floor construction in new buildings by reusing saw-cut reinforced concrete (RC) pieces salvaged from soon-to-be demolished structures. Cutting and reusing large RC pieces rather than crushing them to rubble is an untapped emerging circular construction method with a high potential for reducing waste generation, natural resource consumption, and upfront greenhouse gas emissions. Through an iterative design and analytical process, the study demonstrates how discarded cast-in-place RC floors can be cut and reused to build new low-carbon, little-extractive, load-bearing building floors. The study provides two new floor design solutions that valorise frequently discarded construction components (reinforced concrete slabs and steel profiles), combining construction technologies already used by the industry. The parametric design of 20′280 combinations of donor and receiver structures and their environmental analysis through Life-Cycle Assessment show that the new floor systems have shallow detrimental environmental impacts, with a reduction of upfront greenhouse gas emissions averaging 80 % compared to conventional practice. Floor-system solutions as low as 5 kgCO 2 e/m2 have been obtained. Structural assessments additionally show that flat slabs that are currently demolished meet the structural requirements at the preliminary design stage for reuse in new office or housing buildings. In particular, thanks to mandatory minimum reinforcement, 18-cm thick or thicker flat slabs built in Switzerland after 1956 and spanning up to 4 m are expected to be technically reusable as-is over their entire span. Overall, this study sets up a new benchmark for innovative floor systems with minimum environmental impacts and calls for considering soon-to-be demolished RC structures as mines of valuable construction components. • Reusing concrete pieces is an untapped circular resource-management strategy. • New load-bearing floor systems made of reused as-cut concrete pieces are introduced. • A procedure determines the allowable span for concrete pieces reused in bending. • A parametric study shows upfront greenhouse gas emissions as low as 5 kgCO 2 e/m2. • On average, embodied carbon is reduced by 80 % compared to a traditional concrete slab. [ABSTRACT FROM AUTHOR]

Extracting pieces of concrete from obsolete buildings and reusing them, as is, in new assemblies is today rarely considered a strategy for improving the sustainability of the construction sector. By delaying the crushing of concrete into aggregates and avoiding the need for fresh cement in new buildings, the circular strategy is however expected to reduce greenhouse gas emissions and threats to natural ecosystems. In reaction, the authors postulate that (1) built precedents of Piecewise Reuse of Extracted Concrete in new Structures (PRECS) have existed for several decades, (2) a large diversity of proven implementation techniques is readily available but knowledge is fragmented, (3) barriers to a broader adoption can be inferred from the existing documentation and are largely transitional. To support these postulates, this study first builds an original collection of 77 PRECS projects designed between 1967 and 2022 in Europe and the U.S.A. Next, a diachronic analysis determines seven historical trends and three periods since 1967, shedding new light on the development of PRECS and its design possibilities. Supporting and limiting forces for a broader adoption of PRECS are then identified through a synchronic analysis. Recommendations for future research directions are also given. In conclusion, this paper demonstrates that the reuse of concrete components is a practice with already a long history and several successful operations in terms of environmental impact and cost, which hence supports the potential of PRECS to become a more widespread strategy of cleaner construction. • Reusing concrete pieces in new structures is a rarely considered sustainability strategy. • An original database of 77 concrete reuse case studies is built and analyzed. • Ecological benefits are confirmed for a wide range of built cases. • Circumstances leading to economic benefits are identified. • Industrial and scientific developments can accelerate the strategy implementation. [ABSTRACT FROM AUTHOR]

This article develops a vector-based 3D graphic statics framework that uses synthetic and intuitive graphical means for the analysis and design of spatial structures such as networks of bar elements in static equilibrium. It is intended to support the collaborative work of structural engineers and architects from the conceptual phase of the design process. Several procedures for the construction of a vector-based 3D force diagram for any given 3D form diagram with an underlying planar or non-planar graph are identified and described. In the non-planar case, the proposed procedures rely on the preliminary topological planarization of the graph by cutting the crossing edges and reconnecting them to one or more newly inserted auxiliary vertices. Resulting planar graphs can be then used as a base for the assembly of 3D force diagrams, without altering the static equilibrium of the structure. An implementation of the proposed framework to real design scenarios is presented through two case studies. These examples demonstrate the benefits of bi-directional manipulations of form and force diagrams in the structural design process. [ABSTRACT FROM AUTHOR]

• Structural optimization with integrated Life Cycle Assessment. • Globally optimal element assignments via mixed-integer linear programming. • Environmental impact reduction by up to 56% for structures made of reused elements. • Statistical analysis carried out through varying 100 stock configurations. • Combining reused and new elements results in least environmental impact structures. An important share of building environmental impacts is embodied in load-bearing structures because of their large material mass and energy-intensive fabrication process. To reduce substantially material consumption and waste caused by the construction industry, structures can be designed and built with reused elements. Structural element reuse involves: element sourcing and deconstruction, reconditioning and transport. As these processes also generate environmental impacts, reuse might not always be preferred over new construction. This paper presents a method to design reticular structures with minimal environmental impact made from reused and new elements. The formulation given in this paper is based on a combination of Life Cycle Assessment (LCA) and discrete structural optimization. The LCA carried out in this work accounts for impacts generated from sourcing reclaimed elements to the assembly of the structure. Structural optimization is subject to stress constraints on element capacity and deflection limits for serviceability. Typical loading scenarios are considered. The method is applied to the design of three single-span steel trusses of different topology subject to 100 simulated stocks of reusable elements that have varying cross-sections and lengths. Benchmarks against minimum-weight solutions made solely from recycled steel show that this method produces structures with up to 56% lower environmental impact. Depending on stock availability, the lowest environmental impact is achieved through a combination of reused and new elements. [ABSTRACT FROM AUTHOR]