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The durability of aging bridge structures has become a serious societal concern. It has been estimated that 40%–50% of the bridge stock in Europe and 36% in the US is approaching and exceeding the intended service life in some cases. Conventional retrofitting methods are generally effective under predetermined loading scenarios and can mitigate to some extent the effect of damage through strengthening and stiffening. However, typical retrofit measures involve the addition of components, which might cause unwanted stress accumulation, and in addition, they cannot perform adaptation after damage to recover functionality. Adaptive structural systems can modify the response under loading using sensors and mechanical actuators, instead of relying solely on the resistance offered through material and geometry. Previous work has shown that well-designed adaptive structures are effective in reducing peak responses under strong loading resulting in configurations that embody far fewer material and carbon resources than conventional passive systems. This work investigats retrofit strategies using active control through mechanical actuators integrated into the bridge's primary load path or as external systems. The objective is to extend the durability of most common bridge types including beam, tied-arch, and cable-stayed. Two active retrofit systems are considered: (1) an external adaptive tensioning (EAT) for beam bridges; (2) linear actuators placed in the hangers and stays of tied-arch and cable-stayed bridges. Depending on the failure mode (e.g., corrosion-, fatigue-induced), the effect of active control is simulated through a quasi-static controller based on least-squares minimization or through a linear quadratic regulator and explicit time-history analysis. Results shows that the stress reduction achieved by the EAT system retrofitted to a concrete bridge with corrosion-induced damage could extend service by approximately 12 years. In both cable-stayed and tied-arch bridges, the stress range amplitude caused by vehicular traffic is reduced below the constant amplitude fatigue limit, potentially extending service beyond 75 years. [ABSTRACT FROM AUTHOR]

Functionally Graded Concrete (FGC) allows for a significant reduction in the mass of concrete components while maintaining their structural and functional requirements and improving recycling capacity. This is achieved by inserting spherical mineral hollow bodies into the structure where no material is required. Within the scope of this work, the behavior of FGC slabs exposed to fire is investigated both experimentally and numerically and compared to a corresponding solid cross-section. Therefore, FGC specimens are placed in a test furnace and subjected to fire exposure for 90 min. The temperature distribution, bending load-bearing capacity, and spalling behavior are investigated. The results of the numerical simulation of the solid cross-section are in good agreement with the values provided in the building code. However, for the FGC cross-section, differences in temperature at characteristic measurement points between the experimental and numerical results are observed, presumably due to convection. The experimental results suggest that the bending load-bearing capacity of the investigated FGC cross-section could be potentially greater than that of a corresponding solid cross-section. Furthermore, as expected through analytical analysis, the fire tests confirm that no spalling of the FGC specimens occurred. [ABSTRACT FROM AUTHOR]

The built environment faces significant challenges in managing energy demands amidst rising temperatures and increasing concerns linked to climate change. Meeting carbon emissions targets and resource management goals necessitates urgent innovation in more energy-efficient cooling solutions. Nature offers a large database of adaptive and efficient thermal solutions that can be harnessed through biomimetic methods in building design and systems. Emerging biomimetic and computational approaches hold promise in facilitating practical application efforts. This paper investigates the translation of morphological features from elephant skin to building facades, optimizing their inherent cooling capabilities through computational design using evolutionary algorithms. Through this exploration, we propose a set of generalized evolutionary principles, offering a foundational framework for the development of textured facade tiles with the aim of mitigating heat gain from solar radiation. This study provides an in-depth analysis of how assembly, texture depth, and orientation impact thermal performance, enabling the design of more effective passive cooling systems through an understanding of the relationship between morphological variations in textured surfaces and environmental performance. Future research may involve studying natural convection dynamics, optimizing capillary networks, evaluating materials for water adhesion and cleaning, assessing impacts on biological growth, and exploring biodiversity integration within textured facade panels. [ABSTRACT FROM AUTHOR]

Floor systems are typically designed to satisfy tight deflection limits under out-of-plane loading. Although the use of concrete flat slabs is common in the built environment due to the ease of construction, the load-bearing performance is inefficient because the material is not optimally distributed within the cross section to take the bending caused by external loads. This typically results in significant oversizing. Floor slabs account for more than 50% of the material mass and associated emissions embodied in typical low-rise reinforced concrete buildings. In addition, the volume of carbon-intensive cement production has tripled in the last three decades. Therefore, lightweight floor systems that use minimum material resources causing low emissions can have a significant impact on reducing adverse environmental impacts of new constructions. Recent work has shown that rib-stiffened slabs offer significant potential for material savings compared with flat slabs. This work investigates adaptive rib-stiffened slabs equipped with an adaptive tensioning system. The adaptive tensioning system comprises cables embedded within the concrete rib through a duct that enables varying the cable tension as required to counteract the effect of different loading conditions without applying permanent prestress that might cause unwanted long-term effects including tension loss and amplified deflection. The cables are positioned following a profile so that the tension force is applied eccentrically to the neutral axis of the slab-ribs assembly. The resulting system of forces causes a bending moment that counteracts the effect of the external load. The rib placement is optimized through a greedy algorithm with a heuristic based on the direction of the principal stresses. The deflection of the slab is reduced by adjusting the cable tensile forces computed by a quasi-static controller. Benchmark studies comparing different cable profiles and active rib layouts are carried out to determine an efficient control configuration. A case study of an 8×8-m adaptive rib-stiffened slab is implemented to evaluate material savings potential. Results show that the adaptive slab solution can achieve up to 67% of material savings compared with an equivalent passive flat slab. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Extended lightweight construction – Part 1: Lightweight materials For more than 20 years, the Institute for Lightweight Structures and Conceptual Design (ILEK) has been engaged in interdisciplinary research on the supposed paradox of "lightweight construction with concrete". Excerpts from the current research are now presented in a two‐part article. This first part considers developments at the material level (lightweight materials) with the aim of minimizing use of primary resources, material‐related emissions, and waste in different phases of building life cycle. These include: the substitution of natural aggregates with recycled ones, biomineralized calcium carbonate as an innovative substitute for cement, basalt fiber composite reinforcement as an alternative to conventional reinforcing and prestressing steel, and recyclable sand formworks for zero‐waste production of lightweight concrete structures. [ABSTRACT FROM AUTHOR]