The priority program (PP) 2187 "Adaptive Modular Construction made in a Flux" brings together the disciplines of civil engineering, mechanical engineering, architecture, and mathematics. The goal is replacing the craft-based manufacturing of concrete components with automated, serial production methods. Since 2020, 14 individual sub-projects - in addition to the coordination project - researched across two funding periods of 3 years each towards this paradigm shift in concrete construction. Thereby, 9 universities, 22 institutes, 25 principal investigators (PI) and around 60 early-career researches participated from all over Germany. The PP was initiated and coordinated by the Institute of Concrete Structures at the Ruhr University Bochum. The structure and organization of the PP was carried out through thematic working groups, benchmark- and demonstrator projects. In addition to annual status meetings, the research findings were published in national and international journals as well as at conferences presenting project-related and collaborative results. Furthermore, workshops were organized and conducted to provide discipline-specific and interdisciplinary education for participants. The present contribution outlines the key developments and measures undertaken.

Rising global construction demand calls for greater economic efficiency and ecological sustainability. Precast concrete construction (PCC) can reduce on-site errors and waste by using controlled production environments. However, PCC remains limited by traditional, labour-intensive methods ill-suited to automation and individualised elements. Advances in digital fabrication enable customised concrete modules at scale, but realising this potential requires consistent digital representations that integrate design and production. This paper presents an integrated framework leveraging Industry 4.0 concepts to overcome these limitations, specifically employing the Asset Administration Shell (AAS) to implement modular Digital Twins (DTs). Drawing on perspectives from multiple disciplines, this research outlines design and optimisation methods that demonstrate the potential for highly differentiated, precise concrete modules from various digital production processes. Based on a conceptual multi-storey building as a case study, this work explores advances in the design and production of precast concrete modules to highlight the diverse requirements and use cases for DTs in PCC. Three DT case studies are developed, which support design, production, and quality control. These include the simulation-based geometric modularisation of building elements to support early design phases, the monitoring and structuring of production data for analytical insights, and the management of geometric deviations of individual building modules, assessed in relation to their cumulative effect on the overall structural assembly. The results demonstrate the feasibility and effectiveness of integrating the DT concept via the AAS to manage complexity across design and production phases of individualised precast structures, paving the way for more sustainable and efficient construction practices in concrete.

Modular construction with precast concrete elements offers significant potential for rapid and resource-efficient building. This paper presents findings from the scientific coordination project of Priority Program (PP) 2187, addressing key challenges in the design and production chain. Generalized structural models for 1D and 2D modular structures are derived, and load-bearing capacities of slender reinforced concrete modules are described using M/N interaction charts including geometric scatter. Production-induced tolerances are systematically quantified and propagated to the structural level via Gaussian error propagation. For multi-dimensional structures, a sensitivity-based placement strategy using Elementary Effects is proposed, reducing global deformations by up to 43%. Construction sequences are optimized using Simulated Annealing, ensuring intermediate construction states do not govern final dimensioning. The convertibility of modular structures is assessed through sensitivity analysis of load redistribution. All boundary conditions are integrated into a digital twin based on the Asset Administration Shell. The findings reveal that adaptive modular construction represents a viable pathway toward industrialized, sustainable, and circular concrete construction. Adaptive Modulbauweisen mit Flie ss fertigungsmethodenModulares Bauen mit Betonfertigteilen bietet erhebliches f & uuml;r eine schnelle und ressourceneffiziente Bauweise. Dieser Beitrag pr & auml;sentiert Ergebnisse des wissenschaftlichen Koordinationsprojekts des Schwerpunktprogramms (SPP) 2187 und behandelt wesentliche Herausforderungen aus dem Entwurf und der Produktionskette. Es werden verallgemeinerte Tragwerksmodelle f & uuml;r modulare 1D- und 2D-Strukturen hergeleitet. Die Tragf & auml;higkeiten schlanker Stahlbetonmodule werden mithilfe von M/N-Interaktionsdiagrammen unter Ber & uuml;cksichtigung geometrischer Streuungen beschrieben. Produktionsbedingte Toleranzen werden systematisch erfasst und mittels Gau ss scher Fehlerfortpflanzung auf die Strukturebene & uuml;bertragen. F & uuml;r mehrdimensionale Tragwerke wird eine sensitivit & auml;tsbasierte Platzierstrategie mithilfe Elementarer Effekte vorgeschlagen, die globale Verformungen um bis zu 43% reduziert. Baureihenfolgen werden mithilfe von Simulated Annealing optimiert, sodass Bauzust & auml;nde nicht f & uuml;r die Bemessung ma ss gebend werden. Dar & uuml;ber hinaus wird die Wandelbarkeit modularer Strukturen durch Sensitivit & auml;tsanalysen der Lastumverteilung bewertet. Alle Randbedingungen flie ss en in einen digitalen Zwilling auf Basis der Verwaltungsschale ein. Die Ergebnisse zeigen, dass adaptives, modulares Bauen eine vielversprechende Methode f & uuml;r eine industrialisierte, nachhaltige und kreislauff & auml;hige Betonbauweise darstellt.

Ensuring geometric accuracy in precast concrete production is becoming increasingly critical, especially for modular, tolerance-sensitive designs. This is particularly evident in segmental structures with dry joints, where even minor deviations can significantly affect assembly and structural performance. Within this context, a demonstrator for Digital Twin (DT)-based quality monitoring is developed using a modular precast segmental pedestrian bridge as a test case. High-resolution geometric data for individual segments are acquired via structured-light scanning and linked to digital representations of the segments. These are subsequently integrated into a DT of the overall structure, enabling the combined consideration of design and as-built information. The demonstrator illustrates how scan-based data can support the identification of geometric deviations and contribute to quality-related decision-making during production. In addition, the integration of measurement data into a DT environment is outlined, highlighting opportunities for improved traceability and consistency across production stages. Qualit & auml;tskontrolle auf Basis Digitaler Zwillinge: Sicherung der Pr & auml;zision bei BetonfertigteilenDie Gew & auml;hrleistung der geometrischen Genauigkeit bei der Herstellung von Betonfertigteilen gewinnt zunehmend an Bedeutung, insbesondere bei modularen, toleranzempfindlichen Konstruktionen. Dies zeigt sich besonders deutlich bei Segmentkonstruktionen mit Trockenfugen, bei denen bereits geringf & uuml;gige Abweichungen die Montage und die statische Leistungsf & auml;higkeit erheblich beeintr & auml;chtigen k & ouml;nnen. Vor diesem Hintergrund wird ein Demonstrator f & uuml;r die Digitale-Zwillings (DT)-basierte Qualit & auml;ts & uuml;berwachung entwickelt, wobei eine modulare Fu ss g & auml;ngerbr & uuml;cke aus Betonfertigteilen als Testfall dient. Hochaufl & ouml;sende geometrische Daten f & uuml;r einzelne Segmente werden mittels Streifenlicht-Scanning erfasst und mit digitalen Darstellungen der Segmente verkn & uuml;pft. Diese werden anschlie ss end in einen DT der Gesamtkonstruktion integriert, wodurch die kombinierte Ber & uuml;cksichtigung von Konstruktions- und Bestandsdaten erm & ouml;glicht wird. Der Demonstrator veranschaulicht, wie scanbasierte Daten die Identifizierung geometrischer Abweichungen unterst & uuml;tzen und zur qualit & auml;tsbezogenen Entscheidungsfindung w & auml;hrend der Produktion beitragen k & ouml;nnen. Dar & uuml;ber hinaus wird die Integration von Messdaten in eine DT-Umgebung skizziert, wobei M & ouml;glichkeiten f & uuml;r eine verbesserte R & uuml;ckverfolgbarkeit und Konsistenz & uuml;ber alle Produktionsstufen hinweg aufgezeigt werden.

With regard to climate change and the importance of utilization of solar energy, the development of a modular concrete heliostat is presented. The focus thereby lies on the design and the construction of the concentrator structure, demonstrating the technical proof of concept fora small-scale collector. The idea of using concrete as a structural material is its free shapeability, and its worldwide availability. With respect to accuracy demands, a high-performance concrete (HPC) is used that possesses a high compressive and also tensile strength. The collector is designed as a strut-like structure with main radial beams and a central mount to ensure high stiffness. A circular design minimizes shading effects in the solar field. By employing symmetry reduction methods, the concentrator is dissolved into equal segments making it a modular construction. To demonstrate the feasibility, a prototype with diameter 3.2 m and a weight of just about 340 kg consisting of four modules was developed. The production is achieved using a modular formwork made from polystyrene at the RPTU Kaiserslautern. The concrete heliostat is built-up and qualified at the solar tower J & uuml;lich (Germany) by means of photogrammetric measurement of the mirror surface. In addition, the concrete structure was measured in the lab of the Ruhr University Bochum. The deformations of the concrete structure vary mainly in the range of +/- 1 mm only indicating remarkable stiffness. In contrast, the mirror deformations reveal an optical efficiency of SDrms = 7.8 mrad. However, these deformations are primarily attributed to the simple mirroring concept by means of clamping, which was not the central subject of the development. However, deviations between varying collector positions are less than 2 mm and only occur in local areas of single mirror facets, which additionally underlines the stiffness of the concrete structure.

The reuse of reinforced concrete (RC) components from deconstructed buildings offers a promising approach to reduce the environmental impact of new constructions. However, it represents a complex combinatorial optimization problem to efficiently place the available modules, which vary in geometry and load-bearing capacity, into new structures while maximizing their utilization. This paper proposes a two-stage optimization method to enable the reuse of arbitrary RC modules. First, an agent-based model is employed to rapidly explore feasible geometric combinations of modules and preselect suitable placements based on a target span length. Second, metaheuristic optimization algorithms, namely Simulated Annealing and Tabu Search, are adapted to maximize the utilization of the modules' load-bearing capacity while ensuring global structural integrity. The methods are demonstrated on a case study of assembling a three-span continuous beam. Lacking real data of dismantled RC elements, a construction kit of 100 modules with varying cross-sectional properties and material parameters is artificially sampled. The results show the agent-based preselection effectively finds viable geometric combinations, while the metaheuristics converge on optimized module placements with up to 88% utilization on average. The proposed approach provides a computational framework to enable the direct reuse of structural concrete components, supporting the design of low-carbon circular buildings.

Im Anbetracht der gesellschaftlichen Herausforderungen des 21. Jahrhunderts, die an das Bauen der Zukunft gestellt werden, stellt sich die Frage, ob der Betonbau noch Teil dieser Zukunft ist. Das aber gerade mit dem Massenprodukt Beton ein ressourcenschonendes und klimaresilientes Bauen möglich ist, zeigen die in diesem Beitrag ausgewählten Beispiele, Ansätze und Möglichkeiten. Die Beleuchtung bereits vorhandener Erfahrungen aus der Tradition des Betonbaus und das Darstellen der aktuellen Entwicklungen skizzieren die zukünftigen Möglichkeiten. Es wird deutlich, dass die aufgezeigten Lösungen stets das Ziel verfolgen, in der Breite das Bauen mit Beton zukunftsfähig zu gestalten. So können auch einzelne Umsetzungsmöglichkeiten oder eine Kombination zielführend sein. Grundsätzlich gilt es, langlebige Bauwerke mit Lebensdauern über mehr als 100 Jahre sowie eine möglichst vollständige Umnutzung (Reuse) oder Wiederverwendung zu ermöglichen.

Automated, quality-assured processes for the rapid production of adaptive, reinforced concrete modules - implementation in a research facility Modular construction methods based on building blocks principle enable cost-effective and fast construction. This requires geometrically and materially precisely manufactured modules, which can be implemented and largely automated in industrial prefabrication. However, such prefabrication is not yet common and is limited to similar serial components such as railroad sleepers. In the paper, a full-scale research facility is developed that keeps the individual steps of automated production in high-precision variable and opens them up to modules of any shape. The system can be used to develop the individual process steps of shuttering, reinforcing, concreting, hardening or qualifying, and to develop the overall process in a quality-assured rapid circular manner or to test meaningful alteration (adaptivity), such as in cross-sectional dimensions or shapes. Three robots are integrated for automation. They place free-form molds and built-in parts, weld reinforcements or qualify geometrically with lasers and stereo cameras or mechanically with rebound hammers. A special curing chamber with circulating air and heating plates with direct contact to the steel formwork enables controlled heat and moisture treatments for curing times of less than an hour. A simulation model is being developed as part of the plant's digital twin, which will help to improve the robot movements.

The demand for new housing is constantly growing and cannot be met by artisanal, in-situ construction methods. At the same time, CO2 emissions generated from the construction of new buildings need to be significantly reduced. Precast concrete elements offer the potential for an optimized design with minimal material consumption using high-performance materials. However, this only makes sense when the precast modules can be fabricated in a serial manner. Therefore, a modularization approach is developed that resolves structures into a small number of similar modules to enable an efficient and rapid mass production. Walls and wall-like beams are divided into hexagonal honeycomb structures mainly consisting of Y-modules and columns. The load-bearing capacity of these modules is described holistically for bending, shear and stability. By means of clustering, modules with low CO2 emissions with respect to their load-bearing capacity are grouped into construction kits. These kits are then used to assemble the final honeycomb structures. This combinatorial optimization problem is solved with two metaheuristics, Tabu Search and Simulated Annealing. Three case studies show that this modular approach reduces CO2 emissions by up to 80% compared to monolithic structures. The optimized positioning saves a further 23% with the same load-bearing capacity.

The prefabrication of reinforced concrete components bears considerable advantages over conventional in-situ concrete construction. For instance, an integration of rapid heat treatment allows the processing time in rapid production to be reduced to just a few hours. Treatment time and temperature affect the development of the mechanical properties most. Control of the latter ensures the quality of the components. For concrete components, destructive tests on accompanying samples are common. In this paper, a method is developed with which compressive strength, modulus of elasticity and bond strength can be derived from testing integrated in the production process. The suitability of rebound hammer testing is analysed, taking into account the boundary conditions of heat treatment. Experiments are used to determine the specified target values for the high-strength Nanodur concrete during production with varying times of heat treatment. The experimental results are compared to the ones derived from standardised correlations. In this way, a model is formed with which primarily the compressive strength and along with it the modulus of elasticity and the bond strength are obtained. The method is discussed against the experimental and theoretical findings. Its application is demonstrated on a simple example and recommendations for checking the mechanical properties in rapid production practically are provided.

For a sustainable design, the equivalent reuse of reinforced concrete (RC) components helps to significantly reduce waste and CO_2 -emissions from construction. A key task is the development of new connections for the modules transmitting internal forces and shaping the new structure. In this contribution, the derivation of an additive joint for RC beams using steel-fiber reinforced concrete (SFRC) and additional steel reinforcement is presented. The geometry of the cut-out for jointing thereby relies on the maintenance of load-bearing capacity and serviceability with respect to a complete beam, which is experimentally investigated. The tests were performed in full scale and holistically measured, e.g., using digital image correlation to monitor deformations and growth of crack widths. The experiments revealed that the additive beam exhibits a 20

Process-accompanying derivation of mechanical properties of high-strength concretes during rapid production The prefabrication of reinforced concrete components bears considerable advantages over conventional in-situ concrete construction. For instance, an integration of rapid heat treatment allows the processing time in rapid production to be reduced to just a few hours. Treatment time and temperature affect the development of the mechanical properties most. Control of the latter ensures the quality of the components. For concrete components, destructive tests on accompanying samples are common. In this paper, a method is developed with which compressive strength, modulus of elasticity and bond strength can be derived from testing integrated in the production process. The suitability of rebound hammer testing is analysed, taking into account the boundary conditions of heat treatment. Experiments are used to determine the specified target values for the high-strength Nanodur concrete during production with varying times of heat treatment. The experimental results are compared to the ones derived from standardised correlations. In this way, a model is formed with which primarily the compressive strength and along with it the modulus of elasticity and the bond strength are obtained. The method is discussed against the experimental and theoretical findings. Its application is demonstrated on a simple example and recommendations for checking the mechanical properties in rapid production practically are provided.

Influence of rapid heat treatment on the short-term creep of high-strength concrete Assembly of modular load-bearing structures requires high precision geometry of precast concrete parts. Besides the manufacturing tolerances, transient, material-related deviations due to shrinkage and creep must be taken into account. Regarding deformations [1] has already shown that rapid heat treatment significantly reduces shrinkage in high-performance concretes. In this paper, the influence of heat treatment on creep deformation will be investigated. The focus is on short-term creep within the first 28 days after concreting in order to mimic early construction stages experimentally. Heat treatment immediately after concreting in durations of 2, 4 and 24 h at 80 °C and 60 % RH as well as samples without heat treatment for reference are investigated. Loading starts 48 hours after concreting to cover minimum times between production and assembly. The experiments are performed on cylinders ( D / H =100/200 mm) at load levels of 20 and 40 % of the early concrete strength. It is shown that heat treatment effectively reduces creep strains by up to 66 % (24 h) or 21 % (2 h), depending on the duration. Despite the high initial strength of the concrete, non-linear creep is observed. The test results are generalized for different durations of heat treatment and load levels and processed into functional relationships by polynomial response surfaces.

In modular structures, inaccuracies of the modules superimpose over the entire structure. Depending on the placement of the modules, these inaccuracies have (different) effects on stresses and total deformations. Especially for structures with many individual modules, it is favorable to place them according to their influence. To cover structural diversity, column-, beam-, and wall-like modular structures made from plane modules are investigated. In numerical simulation, geometric inaccuracies are applied via an equivalent temperature approach, which allows almost arbitrary nodal deviations of the modules. With the elementary effects method, the sensitivities of the modules’ inaccuracies regarding their structural impact can be determined with minimal computational effort. On a predefined control node, the overall structural inaccuracies are examined in a simplified manner. Column-like structures experience higher deformations due to inclination than beam-like or wall-like structures. For column-like, the bottommost modules are decisive for the overall inaccuracy, as they contribute significantly to the inclination. By contrast, modules at the supports are identified as particularly sensitive for beam- and wall-like structures. Controlling module placement towards their mean absolute influence, the deformation at the control node is mathematically reduced by at least 43% compared to random placement. Thereby, even modules that do not comply with tolerance requirements for structural components can be used in areas of low influence for a sustainable and low-waste design.

Optimization-based placement of individual void formers in plates Material savings are crucial in the construction industry. Without it, the worldwide climate targets cannot be achieved. In concrete slabs, void formers offer that opportunity. They displace up to 35 % of the concrete volume in regions of low shear or bending stresses. So far, special void formers have been used for each case. In this article, an optimization procedure is derived that surpasses established approaches in two respects. At first, it enables, depending on the capacity reserves, arbitrary shapes and sizes of void formers to be combined in one slab. The shapes can be arbitrarily rectangular, spherical, or ellipsoidal and are generalized by so-called superellipsoids. Moreover, the optimization is coupled to the determination of the internal forces of the slab. The stiffness-based change of the internal force distribution by the void formers is an integral part of the procedure. Thus, subsequent checks of internal forces become unnecessary. The core of the optimization procedure is the computational variation of the density, which is linked to the remaining concrete material. The load-bearing capacity is verified by minimum compression zone heights (bending) and reduced resistances of not shear-reinforced slabs (shear force). Two examples show the practical application on plate strips and flat slabs, respectively.

Der globale Erdüberlastungstag (Earth Overshoot Day) fiel letztes Jahr auf den 28. Juli 2022 und war damit der früheste der Menschheitsgeschichte. In Deutschland, als Industrienation, fand er in diesem Jahr bereits am 4. Mai statt. An diesem Tag sind theoretisch alle natürlichen Ressourcen, die auf unserer Erde innerhalb eines Jahres nachhaltig nutzbar sind, aufgebraucht. Ab diesem Zeitpunkt leben wir auf „Pump“, was durch zunehmende Extremwetterereignisse und deren katastrophale Folgen in den letzten Jahren vermehrt zu spüren war. Die Prognose für 2023 sieht ähnlich aus. Wir bräuchten also eigentlich zwei Erden. Eine Trendwende ist bisher nicht auszumachen. Vorhersagen zeigen eher eine stetige Verschlechterung simultan zum Wachstum der Weltbevölkerung, sodass wir bis 2050 sogar drei Erden benötigen würden. Einen wesentlichen Anteil des ökologischen Fußabdrucks machen dabei die CO2-Emissionen aus, welche zu einem großen Anteil auf das Bauen zurückzuführen sind. Als Bauingenieur:innen tragen wir die Verantwortung mit, das Ruder herumzureißen, besitzen aber einen vergleichsweise großen Hebel, dies auch zu schaffen. Wie? Das zeigen viele Ansätze aus unterschiedlichen Fachdisziplinen. Mit Optimierungsmethoden lassen sich kraftflussaffine Tragwerke herleiten, die nur dort Material besitzen, wo es für die Tragfähigkeit notwendig ist. „Grüner“ Stahl und klinkerarme Betone reduzieren maßgeblich die herstellungsbedingten CO2-Emissionen. Mit Hochleistungs- und Carbonbetonen lassen sich Tragwerke mit Dicken von nur wenigen Zentimetern herstellen. Additive Verfahren erlauben die Herstellung von komplexen, materialminimierten Geometrien. Die modulare Bauweise steigert die Produktivität und reduziert durch eine Schnellmontage vor Ort die eigentliche Bauzeit. Eine ganzheitliche Digitalisierung ermöglicht eine automatisierte Produktion und stellt das Monitoring über den gesamten Lebenszyklus sicher. Die genannten Ansätze allein, die nur eine Auswahl aufzeigen, stellen bereits einen Mehrwert dar. Idealerweise werden Synergien genutzt und Ansätze disziplinübergreifend zusammengeführt. Durch die Interdisziplinarität eröffnen sich neue Wege, die sonst durch den oft eingeschränkten Tunnelblick der eigenen Expertise verschlossen bleiben. Etwa im Research Network AdvanceAEC haben sich dazu verschiedene Forschungsverbünde zusammengeschlossen, um das Bauen durch Interdisziplinarität und Digitalisierung voranzubringen. Das Miteinander hilft die komplexen Aufgaben für ein nachhaltiges, verschwendungsarmes Bauen der Zukunft zu lösen. Gleiches spiegelt sich auch im vorliegenden Heft wider, mit Beiträgen von kleinen und großen Autor:innenteams, die methodische und experimentelle Entwicklungen aufzeigen, um das Bauen miteinander nachhaltig zu gestalten. Dr.-Ing. Patrick Forman Ruhr-Universität Bochum Lehrstuhl für Massivbau Patrick Forman

Modulare Tragwerke erfordern masshaltige Bauteile, da grosse prozess- oder materialbedingte Massabweichungen bei einzelnen Modulen die Montage zur Gesamtstruktur verhindern. Im Beitrag wird dazu eine Methode zur optimalen Platzierung auf Basis von Metaheuristiken vorgestellt. Sie hilft kostenintensive Nacharbeitungen zu vermeiden. Das Konzept wird auf Wabenstrukturen angewendet, in denen die einzelnen Module durch Permutation getauscht werden. Mit dem sog. Tabu Search und dem Simulated Annealing werden methodisch zwei Losungsverfahren verwendet. Dazu werden die maximalen Knotenabweichungen der assemblierten Module mit einer direkten Kinematik ermittelt und mit dem zulassigen Nennlochspiel von Schraubenverbindungen verglichen, um die Montierbarkeit der Module zu beurteilen. Berucksichtigt werden zum einen Toleranzen aus dem Schwinden des Betons und zum anderen solche aus den Produktionsschritten der Fertigung. Im Vergleich zu einer zufalligen Anordnung der Module gelingt die Reduzierung maximaler Knotenabweichungen von 9 mm auf das normierte Nennlochspiel von 3 mm mithilfe der Metaheuristiken. Wabenstrukturen mit einer Breite von ca. 7 m und einer Hohe bis 45 m, die besonders sensitiv hinsichtlich der Montierbarkeit sind, benotigen damit keine Nacharbeit mehr. Dabei erweist sich der Tabu Search mit sechsmal weniger Rechenzeit und bis zu 24 % geringeren zu kompensierenden Abweichungen als der deutlich effizientere Losungsalgorithmus. Ein Beispiel zeigt die praktische Anwendung. Tolerance-free assembly of modular concrete structures - optimization of module arrangement with metaheuristicsModular structures require dimensional stable components, since large process- or material-related dimensional deviations in individual modules prevent assembly to the overall structure. The article presents a method for optimal placement based on metaheuristics. It helps to avoid cost-intensive rework. The concept is applied to honeycomb structures in which the individual modules are swapped by permutation. With the so-called Tabu Search and Simulated Annealing, two solving techniques are methodically used. For this purpose, the maximum nodal deviations of the assembled modules are determined with direct kinematics and compared with the admissible nominal hole clearance of bolted joints in order to assess the assembly capability of the modules. Tolerances from the shrinkage of the concrete on the one hand and those from the production steps of fabrication on the other hand are taken into account. Compared to a random arrangement of the modules, the reduction of maximum nodal deviations of 9 mm to the normalized nominal hole clearance of 3 mm succeeds with the help of the metaheuristics. Honeycomb structures with a width of approx. 7 m and a height of up to 45 m, which are particularly sensitive in terms of assembly, thus no longer require any reworking. Tabu Search proves to be the significantly more efficient solution algorithm, with six times less computation time and up to 24 % fewer deviations to be compensated. An example shows the practical application.

Modular precast construction is a methodological approach to reduce environmental impacts and increase productivity when building with concrete. Constructions are segmented into similar precast concrete elements, prefabricated with integrated quality control, and assembled just-in-sequence on site. Due to the automatised prefabrication, inaccuracies are minimised and the use of high-performance materials is enabled. As a result, the construction process is accelerated, and the modules can be designed to be lightweight and resource-efficient. This contribution presents the fundamentals of modular constructions made from precast concrete components. Then, to elaborate the requirements of a contemporary modular precast construction, the historic developments are described. Further, concepts and technical processes–comprehensible to non-expert readers–are introduced to formalise the discussion about the current state-of-the-art methods. Three case studies treating ongoing research are introduced and related to the conceptual fundamentals. The research is evaluated with regard to current barriers and future directions. In conclusion, modular precast construction is able to reduce emissions and increase productivity in the sector if researchers and firms coordinate the development of suitable technologies that bring value to critical stakeholders.

Material savings are crucial in the construction industry. Without it, the worldwide climate targets cannot be achieved. In concrete slabs, void formers offer that opportunity. They displace up to 35 % of the concrete volume in regions of low shear or bending stresses. So far, special void formers have been used for each case. In this article, an optimization procedure is derived that surpasses established approaches in two respects. At first, it enables, depending on the capacity reserves, arbitrary shapes and sizes of void formers to be combined in one slab. The shapes can be arbitrarily rectangular, spherical, or ellipsoidal and are generalized by so-called superellipsoids. Moreover, the optimization is coupled to the determination of the internal forces of the slab. The stiffness-based change of the internal force distribution by the void formers is an integral part of the procedure. Thus, subsequent checks of internal forces become unnecessary. The core of the optimization procedure is the computational variation of the density, which is linked to the remaining concrete material. The load-bearing capacity is verified by minimum compression zone heights (bending) and reduced resistances of not shear-reinforced slabs (shear force). Two examples show the practical application on plate strips and flat slabs, respectively.

The construction industry faces the challenge of building sustainable and ever faster. The modular construction method with serial precast concrete modules is suitable to achieve this. Here, entire load-bearing structures are segmented into identical or similar modules, which are prefabricated and merely assembled on the construction site. However, the production of precast concrete components has so far by no means been an automated process, as there are hardly any repetition rates. Therefore, Industry 4.0 (I4.0) methods are to be transferred to the prefabrication process, targeted here in line with serial production. The aim is to mass-produce precast concrete modules with high precision and quality assurance in modern production systems based on the I4.0 concept. I4.0 refers to automation through continuous digitalization and networking of production. In the sense of I4.0, smart products seek an optimal path through production systems that interact with machines and processes self-controlled and self-managed. Thereby, the digital twin as a virtual representation for capturing and providing all relevant data is a key component. As a first step towards a holistic digital representation, a high-performance precast concrete module is presented in this work as both a digital twin and a real demonstrator. This Y-shaped module is part of a wall-like honeycomb structure. It is produced using rapid heat treatment and monitored by geometrical and thermal sensors during production and afterwards. The Asset Administration Shell (AAS) as the technical implementation of the digital twin in I4.0 is used to provide suitable methods for communication and interaction.