Life-cycle environmental impact optimization of an RC-THVS composite frame for sustainable construction Iván Negrin, Moacir Kripka, Víctor Yepes Engineering Structures, 2025 This study investigates the benefits of Life-Cycle Environmental Impact Optimization (LCEIO) in structural engineering, focusing on the RC-THVS composite typology as a sustainable alternative for frame-building construction. This innovative structural system integrates reinforced concrete (RC) columns with Transversely Hybrid Variable Section (THVS) steel girders serving as beam elements. The optimization problem is formulated to optimize the Global Warming Potential of the building structure during its life cycle. A novel LHS-CINS algorithm is introduced to solve the formulated optimization problems efficiently. Results show that LCEIO reduces environmental impact significantly, with optimized structures achieving up to a 32 % reduction in emissions compared to traditionally designed buildings. The most substantial improvement occurs in the manufacturing phase, where THVS girders lower emissions by up to 70 % compared to traditional I-section profiles. Additionally, maintenance-related impacts decrease by 45 % due to the girders' optimized tapered geometry. When comparing optimized solutions, rigid-joint composite typologies outperform RC systems in low-aggressiveness environments, reducing life-cycle emissions by 30 %. In highly aggressive environments, composite structures remain more sustainable than RC ones, although maintenance impacts are accentuated. Beyond individual component performance, THVS girders contribute to overall structural efficiency by reducing self-weight, thereby lowering axial loads on columns and foundations. Moreover, when slabs and walls are integrated into the superstructure, composite typologies further enhance system efficiency, cutting emissions by up to 42 % compared to bare frame models. The findings emphasize the capability of LCEIO and composite configurations to design more sustainable, efficient, and environmentally responsible building solutions. • LCEIO of a novel composite frame building structure is performed. • Optimized composite buildings achieve up to 30 % reductions in life-cycle emissions. • Lightweight THVS girders cut axial loads, reducing full assembly impact. • Composite frames lower emissions by 42 % when integrated with slabs and structural walls.
Manufacturing cost optimization of welded steel plate I-girders integrating hybrid construction and tapered geometry Iván Negrin, Moacir Kripka, Víctor Yepes International Journal of Advanced Manufacturing Technology, 2025 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.
An integrated framework for optimization-based robust design to progressive collapse of RC skeleton buildings incorporating soil-structure interaction effects Iván Negrin, Ernesto Chagoyén, Moacir Kripka, Víctor Yepes Innovative Infrastructure Solutions, 2025 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.
Design optimization of a composite typology based on RC columns and THVS girders to reduce economic cost, emissions, and embodied energy of frame building construction Iván Negrin, Moacir Kripka, Víctor Yepes Energy and Buildings, 2025 • A novel composite frame combining RC columns and THVS steel girders is introduced. • Optimized designs reduce costs by 6% and emissions/energy by 16% for shorter spans. • Pinned connections reduce emissions by 6% for longer spans with economic gains. • THVS girders’ light weight lowers axial loads, reducing construction costs further. The construction industry significantly contributes to global energy consumption and emissions, necessitating sustainable alternatives to conventional practices. In this context, this study introduces a novel composite structural typology that combines reinforced concrete (RC) columns with transversely hybrid variable section (THVS) steel girders as beam-type elements. The proposed building frame leverages the high horizontal stiffness of RC columns and the reduced weight of steel girders to lower material consumption. The THVS variant has proven to be one of the most sustainable steel I-girder configurations. Two arrangements are analyzed: one with fixed beam-column connections and another with pinned joints. Structural design optimization problems are formulated, targeting three objectives: economic cost, CO 2 (e) emissions, and embodied energy. These indicators are evaluated using a “cradle-to-site” approach. Results demonstrate that the fixed connection typology is optimal for buildings with shorter spans (4 m), achieving reductions in economic cost (6 %), emissions (16 %), and embodied energy (11 %) compared to traditional RC structures. The pinned variant is more suitable for longer span buildings (8 m), resulting in economic gains of around 5 % and a 6 % reduction in emissions despite higher energy requirements. Optimal THVS configurations indeed employ higher-grade steels in flanges than in the web, with tapered geometries varying by span length and connection type. The study also highlights that the THVS girders’ lighter weight significantly lowers axial loads on columns and foundations, further reducing construction costs and environmental impacts of the structural assembly. These findings underscore the potential of composite designs to enhance sustainability in building construction.
Optimized Transverse-Longitudinal Hybrid Construction for Sustainable Design of Welded Steel Plate Girders Iván Negrin, Moacir Kripka, Víctor Yepes Advances in Civil Engineering, 2024 I-section girders with different types of steel in the flanges and web (fyf > fyw, respectively) are known as transverse hybrid girders. These have proven to be more economical than their homogeneous counterparts. However, the use of hybrid configurations in the longitudinal direction of the element has yet to be studied. This paper uses optimization techniques to explore the possibility of constructing transverse and longitudinally hybrid (TLH) steel girders. The optimization objective is to minimize the manufacturing cost, including seven activities besides the material cost. The geometrically double symmetric I-girder design subjected to a uniform transverse load is performed using Eurocode 3 specifications. Nine case studies are implemented, varying the element span (L) and the applied load. The results show that establishing various configurations along the length of the element is beneficial. The optimum number of transition points is six, meaning the girder will have four configurations, i.e., one central and three others symmetrically distributed toward each half of the element. The optimum position for the first transition would be at 0.24∗(L/2), the second at 0.40∗(L/2), and the third at 0.60∗(L/2). The optimum extreme configuration is usually homogeneous (fyf = fyw = 235 MPa). The others increase the steel quality in the plates, maintaining hybrid arrangements to reach the central one that usually remains with S700 steel for the flanges and S355 for the web. The study shows that TLH configurations are more effective for elements with larger spans. By applying the formulated design recommendations in a different case study, the manufacturing cost dropped by over 50% compared to the traditionally designed element and by more than 10% relative to the optimized element with a homogeneous configuration. The study’s limitations and encouraging results suggest future lines of research in this area.
Design optimization of welded steel plate girders configured as a hybrid structure Iván Negrin, Moacir Kripka, Víctor Yepes Journal of Constructional Steel Research, 2023 This paper implements structural design optimization to improve the economic indexes of welded steel plate girders. The optimization problem is formulated in a way that allows the use of hybrid configurations, i.e., different types of steel in the flanges and web. Besides the cross-sectional dimensions, eleven steel grades are included as optimization variables. In addition to weight and material cost, the manufacturing cost is formulated as an optimization objective, which includes seven other activities, such as welding or painting. The geometrically double symmetric I-girder design subjected to a uniform transverse load is carried out through the Eurocode 3 rules. Nine case studies are implemented by varying the girder span and load values. The results show significant differences depending on the optimization objective, especially between weight and cost optimization. On the other hand, optimization-assisted design provides solutions up to 50% more economical than traditional design methods. Hybrid-optimized configurations can also improve these indexes by about 10% compared to their homogeneous counterpart, demonstrating the applicability of this novel practice. Certain concepts highlighting mechanical properties are proposed to compare the optimal solutions for each case study. These concepts can serve as design recommendations for future projects that include this structural element. Finally, based on the research gaps and the promising results obtained, future lines of research on this topic are established.
Metamodel-assisted meta-heuristic design optimization of reinforced concrete frame structures considering soil-structure interaction Iván Negrin, Moacir Kripka, Víctor Yepes Engineering Structures, 2023 It is well known that conventional heuristic optimization is the most common approach to deal with structural optimization problems. However, metamodel-assisted optimization has become a valuable strategy for decreasing computational consumption. This paper applies conventional heuristic and Kriging-based meta-heuristic optimization to minimize the CO2 emissions of spatial reinforced concrete frame structures, considering an aspect usually ignored during modeling, such as the soil-structure interaction (SSI). Due to the particularities of the formulated problem, there are better strategies than simple Kriging-based optimization to solve it. Thus, a meta-heuristic strategy is proposed using a Kriging-based two-phase methodology and a local search algorithm. Three different models of structures are used in the study. Results show that including the SSI leads to different design results than those obtained using classical supports. The foundations, usually ignored in this type of research, also prove significant within the structural assembly. Additionally, using an appropriate coefficient of penalization, the meta-heuristic approach can find (on average) results up to 98.24% accuracy for cohesive soils and 98.10% for frictional ones compared with the results of the heuristic optimization, achieving computational savings of about 90%. Therefore, considering aspects such as the SSI, the proposed metamodeling strategy allows for dealing with high-complexity structural optimization problems.
Hybrid steel girders: Review, advantages and new horizons in research and applications Agusztine Terreros-Bedoya, Iván Negrin, Ignacio Payá-Zaforteza, Víctor Yepes Journal of Constructional Steel Research, 2023 Although it is still common practice to use homogeneous steel girders (same yield strength in the flanges and web), implementing hybrid configurations seems to be an excellent alternative to improve the performance and sustainability of this type of structural element. Therefore, this paper provides a comprehensive review of the current state of knowledge on hybrid steel girders. The objective is to improve our understanding of this innovative and sustainable alternative to traditional homogeneous steel elements, with a focus on updating the theoretical basis for future design projects. The study analyzes 128 publications, from which information is extracted on five categorical variables, reflecting the current situation of hybrid elements. In addition to studying each variable separately and highlighting the most relevant research to date, a more in-depth statistical analysis is performed. It is based on simple correspondence analysis, which allows identifying the underlying relationships among the variables. Results summarize the design methods implemented to calculate these structures. Furthermore, the recommended hybrid ratios to achieve the best performance are presented. However, it is found that there are gaps in the research. Consequently, several promising lines of investigation are proposed.
