Building carbon intensity is related to material choice, but more importantly, material volume. The building structural frame itself is responsible for 20–30% of whole-life carbon over 50 years. This figure will double once we build net-zero operational carbon buildings. Carbon savings in the use of materials are therefore he key to reducing the environmental impact of buildings. Recent studies have shown that up to 40% of material in building structural frames could be successfully removed without affecting design code compliance. This unnecessary overdesign of buildings is in part due to a lack of structural optimisation, and acceptance by designers of conservative serviceability assumptions that represent the “low hanging fruit” of reducing embodied carbon in buildings. This paper examines steel frames buildings to determine the carbon savings that can be achieved for cross-section optimisation, as this is the most accessible form of optimisation, without changing the floor system and beam layout. For this purpose the Lightest Beam Method (LBM) was developed that studied non-composite universal beams (UB) members in buildings. Choosing the lightest section with the Eurocodes we can achieve 26.5% of steel savings by mass, with a half of beams governed by serviceability limit states (SLS). If deflection is calculated using variable loads, the proportion of beams governed by the SLS drops to 31.1% giving additional 2.2% mass savings. The highest steel savings of 34.5% can be achieved for lower natural frequency assumptions (3 Hz) and using the average rather than the characteristic steel yield strength. In this case the proportion of beams by mass governed by SLS drops to 19.7%. Based on available case studies it was found that 1/3 of steel in the frames could have been saved which represents 36% of initial embodied carbon or 5% of whole-life carbon for the building over 60 years.

建筑碳强度与材料选择有关，但更重要的是与材料体积有关。在50年的时间里，建筑结构框架本身占整个生命碳的20％至30％。一旦我们建立了净零运营碳建筑，这个数字就会翻倍。因此，节省材料使用中的碳是减少建筑物对环境的影响的关键。最近的研究表明，在不影响设计规范合规性的前提下，可以成功清除建筑结构框架中多达40％的材料。建筑物不必要的过度设计部分是由于缺乏结构上的优化，以及设计者接受了保守的可使用性假设，这些假设代表了减少建筑物内含碳量的“低端成果”。本文研究了钢框架建筑，以确定横截面优化可实现的碳节省，因为这是最容易获得的优化形式，而无需更改地板系统和梁的布置。为此，开发了最轻梁方法（LBM），用于研究建筑物中的非复合通用梁（UB）构件。使用欧洲规范选择最轻的截面，按质量计算，我们可以节省26.5％的钢材，其中一半的梁由可维修性极限状态（SLS）控制。如果使用可变载荷计算挠度，则由SLS控制的梁比例将降至31.1％，从而进一步节省2.2％的质量。对于较低的固有频率假设（3 Hz），并使用平均值而不是特征钢屈服强度，可以实现最高34.5％的钢材节省。在这种情况下，受SLS控制的光束质量比例下降到19.7％。根据可用的案例研究，发现在60年的时间内，框架中的钢可以节省1/3，占初始体现碳的36％或全寿命碳的5％。