Moacir Kripka

Purpose: The construction sector significantly contributes to global CO2 emissions, underscoring the need for structural optimization methods that explicitly integrate mechanical performance, cost, and environmental criteria. However, existing composite-truss optimization studies do not simultaneously couple truss topology and member sizing with composite slab geometry and reinforcement while considering these competing criteria. This work addresses the gap by developing an integrated multi-objective formulation for hybrid composite concrete–high-strength steel trusses, featuring a concrete-filled upper chord and simultaneous optimization of slab geometry with reinforcement. Design/methodology/approach: Two assessment stages were conducted: (1) single-objective optimization across spans of 8–24?m to quantify the structural and environmental benefits of pairing hybrid trusses with optimized slabs; and (2) multi-objective optimization for the best-performing span from (1), including slab capacity as an explicit objective. Particle swarm optimization (PSO) and multi-objective particle swarm optimization (MOPSO) algorithms were used to solve the single- and multi-objective problems, respectively. Findings: Results show that hybrid trusses combined with optimized slabs reduce emissions by up to 24% relative to the corresponding homogeneous trusses combined with catalog-based slabs, consistently select concrete strengths greater than 40 MPa for upper-chord filling, and achieve slab-depth reductions relative to the catalog-based slab configurations through reinforcement optimization. Compared with the minimum-CO2 solutions obtained using PSO, the selected MOPSO solutions provide improved slab load-bearing capacity with limited increases in emissions and cost. For usual loads ranging from 2 to 5 kN/m2, slab load-bearing capacity increased by up to 2.5 times relative to the MOPSO solution at 2 kN/m2 for the same span, with corresponding increases of up to 25% in CO2 emissions and 52% in construction cost. Higher load demands lead to substantial growth in both. Research limitations/implications: The study focuses on medium-span structures (8–24 m) and considers a specific set of material grades and design assumptions, which may limit direct generalization to other structural typologies or boundary conditions. Future research could extend the formulation to larger spans and alternative composite configurations. Practical implications: The proposed framework enables engineers to design more efficient hybrid truss–slab systems by explicitly balancing structural performance, cost, and CO2 emissions. The results demonstrate practical potential to reduce material use in slabs and to optimize concrete strength selection in composite trusses, supporting more sustainable design decisions in real-world applications. Social implications: By reducing material consumption and associated emissions in structural systems, the proposed approach helps lower the environmental footprint of buildings. This supports broader sustainability goals in the construction sector, including climate change mitigation and more responsible use of natural resources. Originality/value: This study introduces an integrated optimization framework that simultaneously couples truss topology, member sizing, and composite slab reinforcement design within a unified multi-objective formulation. Unlike previous studies, it explicitly links slab structural performance with hybrid truss optimization, providing a more comprehensive and sustainability-oriented design methodology.

Steel–concrete composite tubular columns have become increasingly attractive for sustainable structural applications due to their high load-carrying capacity and efficient material utilization. However, optimizing their structural performance while simultaneously minimizing embodied carbon emissions and material cost remains a challenging multi-objective problem. This study presents a comprehensive optimization framework for circular, rectangular, and square composite tubular columns composed of high-strength materials, and using the Particle Swarm Optimization (PSO) and Multi-Objective Particle Swarm Optimization (MOPSO) algorithms. The multi-objective optimization simultaneously maximizes axial load capacity while minimizing embodied CO₂ emissions, considering both sections with (WR) and without (WoR) additional longitudinal reinforcement, enabling the identification of optimal trade-offs between structural performance and environmental impact. Design variables include the cross-sectional dimensions, concrete compressive strength, steel yield strength, and reinforcement configuration. The resulting Pareto-optimal solutions are further evaluated using a multi-criteria decision-making approach based on Minkowski Metrics combined with Entropy Theory to identify the best overall compromise solution. The numerical results demonstrate that the use of high-strength materials can reduce embodied CO₂ emissions by up to 16% in the analyzed cases. The implemented load-bearing capacity formulation was also validated against experimental results, yielding a mean N_exp/N_NBR16239 ratio of 1.01 for the six specimens analyzed. The multi-objective formulation associated with Minkowski metrics produces a robust tool for determining the best solutions in general, as well as the best solutions related to the maximum load that the columns can support. Finally, for both the single-objective and multi-objective problem analyses, increasing the slenderness of the columns resulted in more costly solutions, both economically and environmentally.

The construction industry significantly impacts the environment due to its consumption of natural resources and the generation of solid waste, and concrete is responsible for a great part of this consumption, releasing considerable amounts of CO2. Hence, exploring eco-friendly alternatives to conventional concrete is crucial. This study investigates the use of whole PET bottles as an alternative to concrete in reinforced concrete structures. The aim was to assess the feasibility of using PET bottles as filling material in the tensile zones of reinforced concrete beams. Beams were constructed with no bottles, one layer of bottles, and two layers of bottles. Their performance was evaluated based on ultimate loads and stiffness, compared to beams made with conventional concrete. The goal was to reduce concrete usage without compromising structural integrity. The study of the experiments evidenced that using PET bottles as a filling material in reinforced concrete beams can be a viable approach to reducing concrete consumption and the environmental impact associated with structures.

This paper addresses the topological optimization of composite floor systems, specifically focusing on tubular composite trusses with and without concrete filling in the upper chord. The optimization problem is formulated and solved using particle swarm optimization (PSO) and the Bonobo Algorithm (BO), both with CO₂ emissions reduction as the objective. A comparative analysis is conducted against literature models using full-web beams, revealing a notable 20%+ reduction in total CO₂ emissions for the proposed composite truss configuration. Additionally, a parametric analysis examines how various design parameters affect the optimization solution. Results indicate that the use of concrete in the upper chord has a substantial effect on reducing overall CO₂ emissions, especially with concrete strengths exceeding 25 MPa. Notably, the Bonobo Algorithm outperforms PSO in finding optimal solutions for the composite floor system. The study contributes to the underexplored field of topological optimization for composite truss beams, providing valuable insights into sustainable design practices for structural engineering applications.

This study aims to present a parametric analysis in the optimization problem for steel-concrete composite cellular beams with steel deck slabs. A comparative analysis was carried out considering two scenarios, namely, (i) in the first scenario, the slab span and applied loads were varied, adopting slab configurations from a manufacturer’s catalog for spans of 10 m to 20 m with a step of 2.5 m; (ii) in the second scenario, the same span and loading conditions were considered; however, slab optimization was performed by introducing reinforcement in order to evaluate the resulting impacts on the structural design. In both analyzed scenarios, the objective function was defined as the composite system’s CO₂ emissions. The design constraints were defined based on literature recommendations, and to solve the optimization problem, the Particle Swarm Optimization (PSO) algorithm was also adopted. The results demonstrate that the PSO algorithm was effective in identifying optimal solutions and that the introduction of slab reinforcement, combined with optimal design, led to CO₂ emission reductions of up to 25% at the highest load levels analyzed.

Structural optimization is crucial in advancing simulation-based engineering by potentially improving design sustainability and resilience. However, optimizing for specific criteria often results in inefficient or vulnerable designs when evaluated against other critical factors. Among these factors, structural safety—particularly buildings’ resistance to progressive collapse (PC)—has garnered increasing attention. Despite significant experimental and numerical studies, the integration of PC resistance into structural optimization remains underexplored. This paper introduces a computational framework, termed Optimization-based Robust Design to Progressive Collapse (ObRDPC), combining simulation-based optimization techniques with PC-resistant design principles. The methodology also incorporates an automated strategy for considering soil-structure interaction (SSI), an aspect usually ignored in optimization-based structural design. The proposed framework is validated through five case studies involving 3D reinforced concrete skeleton buildings, each subjected to two load-bearing element removal scenarios using the Alternate Path method. Results demonstrate the pivotal role of SSI in achieving efficient designs and accurately assessing PC robustness. Neglecting SSI can lead to material usage differences of up to 24.29% and 22.09% in superstructure design following corner and exterior column failures, respectively. Findings also indicate that increasing the number of stories enhances structural robustness. In contrast, buildings with 8-meter spans may incur over 50% higher environmental impact to withstand the failure of a load-bearing element. The study also provides insights into load redistribution mechanisms that beams, columns, and foundations adopt to improve structural resilience. Finally, practical design guidelines are provided to support the replicability and real-world application of the framework, promoting sustainable and resilient infrastructure.

Steel plate I-girders are widely used in the construction industry worldwide. While numerous studies have explored ways to enhance their benefits, few have simultaneously optimized both key mechanical components—geometry and material—to develop novel and more efficient typologies. This research employs metaheuristic optimization to explore alternatives to traditional I-girders, formulating optimization problems that integrate geometric and material variables in both transverse and longitudinal planes. The objective is to minimize manufacturing costs, accounting for material expenses and seven key production activities such as welding, cutting, or painting, while ensuring compliance with Eurocode 3 specifications. The results indicate that material selection dominates in short-span girders, whereas geometric optimization becomes more critical for longer spans. The most cost-effective solution identified is the transversely hybrid with variable section (THVS) girder, which features tapered geometry and hybrid material distribution between the flanges and the web. Based on these findings, practical design recommendations are provided, including optimal span-to-depth ratios, hybrid ratios, taper angles, and transition positions for variable cross-section configurations. A proposed design methodology incorporating these recommendations is validated through a case study, demonstrating that THVS elements can reduce costs by up to 70% compared to traditional designs. However, challenges related to material availability, fabrication complexity, and local buckling risks must be addressed to fully realize the potential of these designs. Future research should prioritize FEA and experimental testing to refine these typologies and update design codes to better account for tapered and hybrid girders.