特殊大跨徑橋梁碳足跡分析及減碳策略之研究：以「安心橋」為例

Abstract

隨著城市及工業發展而來的是全球溫室效應及氣候變遷問題日益嚴重，如何減碳並推展永續工程是接下來所有工程人員必須面對的重要課題，精準掌握工程碳排狀況並研擬減碳對策方能有效達成碳排減量目標。 本研究採用「文獻回顧法」，參考目前最新碳足跡標準發展及過往相關研究之碳盤查方式，並以一個具代表性的特殊大跨徑橋梁「安心橋」為實例，相關碳足跡量化則採用「排放係數法」。 本研究案例工程「安心橋」為安坑輕軌運輸系統計畫之跨越新店溪路段橋梁，結構型式為單塔非對稱斜張桁架複合式軌道橋，依碳盤查結果分析，此類特殊大跨徑橋梁之「工程材料」排碳量占比最高，達84.5%，其次為「機具能耗」，占比為11.3%，此二部分合計已達95.8%，為此類型工程減碳之關鍵因子，本研究案例工程採用以下二種方式達到減碳效益，而且此二種方式非但沒有增加施工成本，反而有撙節成本的效益。 一、改變混凝土配比：採用飛灰爐石替代率40%之配比，減碳量達2,360.2 tonCO2e，減碳效果已超過6座大安森林公園（25.8公頃，每年可吸碳約384.6 tonCO2e）每年可吸碳數量總和。 二、改變鋼桁架吊裝施工方式：藉由改變吊裝施工方式，讓原規劃設置於新店溪之施工便橋及臨時支撐架免設置，減少排碳量至少達301.6 tonCO2e(此減碳量尚未考慮施工便橋例行維護及遇颱風或豪大雨來襲，須將覆蓋板系統緊急撤除之相關作業)。

The rapid urban and industrial development has exacerbated the global greenhouse effect and climate change. Consequently, engineers face the imperative task of curbing carbon emissions and promoting sustainable engineering. This study employs the "Literature Review Method", refering to the latest carbon footprint standards and carbon inventory methodologies utilized in previous research. A case study of the "Anhsin Bridge," a notable long-spanning bridge, is presented to illustrate the application of these concepts. The case project "Anhsin Bridge" is a bridge crossing over Xindian Creek section of the Ankeng Light Rail MRT System. The structure is a single tower asymmetrical cable-stayed design with truss frames system rail bridge. Our carbon inventory analysis identified "engineering materials" as the most significant contributor, accounting for 84.5%. The second-highest contributor is "machine energy consumption," representing 11.3% of total emissions. These two factors account for 95.8% of carbon emissions in this particular project and are therefore key factors for carbon reduction efforts. The following two methods are proposed to achieve carbon reduction objectives, without increasing construction costs and even providing cost-saving benefits: Firstly, we adopt a concrete proportion adjustment. By substituting 40% of cement with fly ash and ground-granulated blast-furnace slag, carbon emissions can be curtailed by an impressive 2,360.2 tonCO2e. Notably, this reduction surpasses the annual carbon absorption capacity of 6 Daan Forest Park (spanning 25.8 hectares), estimated at approximately 384.6 tonCO2e per year. Secondly, we propose a modification to the truss frame installation method. By implementing an alternative approach, the temporary bridge and temporary support frame originally planned to be installed at Xindian Creek will no longer be required. And the reduction of carbon emissions will be more than 301.6 tonCO2e, excluding the carbon emissions associated with routine maintenance of the temporary bridge or the emergency removal of the Checked Metro Desk during typhoons or heavy rainfall.