Farklı taşıyıcı sistemlerin lca açısından karşılaştırılması: betonarme, çelik ve beton dolgulu kompozit elemanlar
Comparative life cycle assessment of reinforced concrete, steel, and concrete-filled steel tube structural systems
- Tez No: 1015372
- Danışmanlar: DOÇ. DR. ELİF AĞCAKOCA
- Tez Türü: Yüksek Lisans
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2026
- Dil: Türkçe
- Üniversite: Sakarya Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: İnşaat Mühendisliği Ana Bilim Dalı
- Bilim Dalı: İnşaat Mühendisliği Bilim Dalı
- Sayfa Sayısı: Belirtilmemiş.
Özet
Yapı sektöründe kullanılan taşıyıcı sistemlerin çevresel etkileri, sürdürülebilir yapı tasarımı açısından giderek daha fazla önem kazanmaktadır. Yapıların yalnızca yapısal güvenlik ve ekonomik olarak değil, aynı zamanda çevresel performans açısından da değerlendirilmesi gerekliliği, yaşam döngüsü analizi yaklaşımını ön plana çıkarmaktadır. Bu doğrultuda, farklı taşıyıcı sistemlerin çevresel etkilerinin aynı yapı koşulları altında karşılaştırmalı olarak incelenmesi, sürdürülebilirlik temelli karar süreçleri açısından önemli bir araştırma konusunu oluşturmaktadır. Bu tez kapsamında, çelik taşıyıcı sistemli, betonarme taşıyıcı sistemli ve taşıyıcı sistemi beton dolgulu çelik tüp kolonlardan oluşan çerçeve sistemlerin çevresel performanslarının yaşam döngüsü analizi yöntemiyle değerlendirilmesine odaklanılmaktadır. İnceleme kapsamında ele alınan taşıyıcı sistemler için aynı plan geometrisi, aynı kat yükseklikleri, aynı sistem yüklemeleri ve zemin parametreleri esas alınarak yapısal tasarımlar oluşturularak analiz gerçekleştirilmektedir. Taşıyıcı sistemlerin yapısal analizleri SAP2000 bilgisayar yazılımı kullanılarak yapılmakta; analizler sonucunda kesit boyutları, iç kuvvetler minimum düzeyde tutularak elde edilen malzeme miktarları yaşam döngüsü analizi sürecinde girdi verisi olarak kullanılmaktadır. Bu yaklaşım sayesinde, taşıyıcı sistemler arasındaki karşılaştırmaların aynı yapı koşulları altında ve tutarlı bir çerçevede gerçekleştirilmesi sağlanmaktadır. Yaşam döngüsü analizi kapsamında, yapıların hammadde temini ve malzeme üretimi, inşaat süreci ve kullanım ömrü sonu aşamalarında oluşan çevresel etkiler kapsamlı biçimde değerlendirilmektedir. Analizlerde, taşıyıcı sistemlerin farklı malzeme türleri ve miktarları nedeniyle ortaya çıkan çevresel etki farklılıkları nicel olarak ayrıntılı biçimde ortaya konulmaktadır. Böylece, taşıyıcı sistem seçiminin yapıların toplam çevresel performansı üzerindeki etkisi bütüncül ve sürdürülebilirlik odaklı bir bakış açısıyla ele alınmaktadır. Çalışma sonucunda elde edilen bulgular, taşıyıcı sistem türünün yapıların yaşam döngüsü boyunca oluşan çevresel etkiler üzerinde belirleyici bir rol oynadığını göstermektedir. Karşılaştırmalı değerlendirmeler, farklı taşıyıcı sistemlerin özellikle malzeme üretim aşamasında ortaya çıkan çevresel etkiler bakımından farklılıklar sergilediğini ortaya koymaktadır. Bu tez çalışması, taşıyıcı sistemlerin çevresel performanslarının aynı yapı koşulları altında yaşam döngüsü analizi yöntemiyle değerlendirilmesine yönelik bütüncül bir yaklaşım sunmakta ve sürdürülebilir yapı tasarımına ilişkin karar süreçlerine çevresel etki temelli bir bakış açısı kazandırmaktadır.
Özet (Çeviri)
The environmental impacts associated with structural systems used in the construction sector have become increasingly important in the context of sustainable building design. In recent years, the rapid growth of the construction industry and the extensive use of natural resources have led to significant environmental burdens, including greenhouse gas emissions, energy consumption, depletion of raw materials, and waste generation. Accordingly, evaluating buildings not only in terms of structural safety and economic efficiency but also with respect to their environmental performance has become a fundamental requirement for sustainable development. Within this framework, Life Cycle Assessment (LCA) has emerged as one of the most comprehensive and widely accepted methodologies for quantifying and comparing the environmental impacts of buildings and construction materials throughout their entire life cycle. Life Cycle Assessment is a systematic method used to evaluate the environmental impacts associated with a product, process, or system from raw material extraction to final disposal. In the construction sector, LCA enables the assessment of environmental burdens arising during the production of construction materials, transportation, construction activities, maintenance, and end-of-life processes such as demolition, recycling, and disposal. Since structural systems constitute one of the most material-intensive components of buildings, the selection of an appropriate structural system plays a decisive role in determining the overall environmental performance of a building. Therefore, comparative analyses of alternative structural systems under identical design conditions provide valuable insights for sustainable design and decision-making processes. Within the scope of this thesis, the environmental performance of three different structural systems was evaluated by means of Life Cycle Assessment. The systems considered in the study consist of reinforced concrete structural systems, steel structural systems, and composite structural systems utilizing concrete-filled steel tube (CFST) columns. Concrete-filled steel tube columns combine the advantageous characteristics of both steel and concrete, offering high strength, enhanced ductility, and efficient use of materials. In addition to their structural benefits, such systems have the potential to reduce environmental impacts by optimizing material quantities. The principal objective of this study is to comparatively assess the environmental impacts of these three structural alternatives under the same building conditions and to determine the extent to which structural system selection influences the sustainability of buildings. To ensure a consistent and objective comparison, all structural systems were designed using identical architectural and geotechnical parameters. The models were based on the same plan geometry, number of stories, story heights, loading conditions, and soil characteristics. Consequently, any differences observed in environmental impacts can be attributed directly to the structural systems themselves rather than to variations in building configuration or design assumptions. Structural analyses and designs were performed using SAP2000 structural analysis software. The member sizes were determined in accordance with structural requirements while minimizing internal forces and ensuring compliance with applicable design criteria. Following the structural design process, the quantities of concrete, reinforcing steel, and structural steel were extracted and used as inventory inputs for the Life Cycle Assessment. The Life Cycle Assessment was carried out using SimaPro software, one of the most widely used tools for environmental impact analysis. The ecoinvent database was employed to provide background data for material production, transportation, waste treatment, and recycling processes. The environmental impacts were quantified using the ReCiPe Midpoint (H) impact assessment methodology, which evaluates a broad range of impact categories, including global warming potential, fossil resource scarcity, terrestrial acidification, freshwater eutrophication, human toxicity, and ecotoxicity indicators. The functional unit adopted in this study was one square meter (m²) of total floor area, allowing for a normalized and directly comparable assessment among the three structural systems. The system boundary was defined as cradle-to-grave, encompassing the product stage (A1-A3), construction process stage, and end-of-life stages (C and D) in accordance with EN 15804. The product stage includes raw material extraction, processing, and manufacturing of construction materials. The construction stage incorporates transportation to the site and equipment use during construction. The end-of-life stages account for demolition, waste treatment, landfill disposal, recycling processes, and the environmental benefits associated with the substitution of virgin materials by recycled materials. The use stage was excluded from the analysis because the compared alternatives were assumed to have identical operational characteristics, and differences in environmental performance were expected to arise primarily from the structural systems and their constituent materials. The life cycle inventory was developed based on the material quantities obtained from structural analysis and quantity takeoff procedures. For the reinforced concrete system, concrete and reinforcing steel were considered as the primary materials. The steel structural system included hot-rolled structural steel profiles. The composite system incorporated both structural steel and concrete used in concrete-filled steel tube columns. Transportation processes were modeled using appropriate truck and concrete mixer datasets, and on-site construction equipment such as concrete pumps and cranes was included where relevant. End-of-life scenarios were established based on realistic assumptions regarding demolition and recycling rates. Reinforcing steel and structural steel were assumed to be largely recycled, while concrete waste was partially recycled as inert fill and partially disposed of in inert material landfills. The results obtained from the Life Cycle Assessment demonstrate that the type of structural system has a significant influence on the environmental impacts of buildings throughout their life cycle. The product stage (A1-A3) was identified as the dominant contributor to most environmental impact categories for all structural systems, highlighting the critical importance of material production processes. Differences in environmental performance were found to be primarily associated with the quantities and types of materials used in each structural alternative. The comparative analysis revealed that the steel structural system generally exhibited the lowest environmental impacts in many impact categories. The high strength-to-weight ratio of steel allowed for reduced material consumption, which contributed to lower environmental burdens despite the energy-intensive nature of steel production. The reinforced concrete structural system tended to produce higher impacts due to the substantial quantities of concrete and reinforcing steel required. Cement production, in particular, was identified as a major contributor to global warming potential and other impact categories. The composite system with concrete-filled steel tube columns demonstrated an intermediate and balanced environmental performance, benefiting from both the efficiency of steel and the compressive capacity of concrete. This finding indicates that composite systems constitute a promising alternative for achieving both structural efficiency and environmental sustainability. The end-of-life stages (C and D) played an important role in reducing net environmental impacts, especially for steel-intensive systems. High recycling rates for structural steel and reinforcing steel generated significant environmental credits in Module D by offsetting the production of primary materials. Consequently, steel and composite systems benefited substantially from recycling processes, further improving their overall environmental performance. These results emphasize the importance of considering end-of-life scenarios and circular economy strategies when evaluating sustainable construction alternatives. In addition to environmental considerations, the study also provides insights into the relationship between structural performance and sustainability. Each structural system possesses distinct mechanical characteristics affecting stiffness, ductility, and load-carrying capacity. The integration of structural analysis results with Life Cycle Assessment demonstrates that environmentally favorable solutions can also satisfy structural performance requirements. This holistic approach underscores the necessity of incorporating environmental criteria into structural design decisions from the earliest stages of project development. The findings of this thesis confirm that structural system selection is a critical design parameter influencing the environmental sustainability of buildings. The results indicate that alternative structural systems can lead to considerable differences in life cycle environmental impacts, even when all other building characteristics remain unchanged. Accordingly, decisions regarding structural materials and systems should be supported not only by structural and economic analyses but also by comprehensive environmental assessments. This thesis presents an integrated methodology that combines structural analysis, quantity takeoff, and Life Cycle Assessment to evaluate the environmental performance of reinforced concrete, steel, and concrete-filled steel tube structural systems under identical conditions. The proposed approach contributes to the growing body of knowledge on sustainable construction and provides a practical framework for designers, engineers, and decision-makers seeking to reduce the environmental impacts of buildings. Furthermore, the study highlights the potential of steel and composite systems to offer competitive environmental advantages while maintaining satisfactory structural performance. As a result, the integration of Life Cycle Assessment into structural design processes is shown to be an effective strategy for developing buildings with reduced environmental impacts and improved sustainability. The methodology and findings presented in this thesis are expected to support future research and professional practice aimed at promoting environmentally responsible and resource-efficient construction.
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