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Paper 2 plan Assessing the upfront carbon cost of structural adaptability…
Paper 2 plan
Assessing the upfront carbon cost of structural adaptability
Introduction
Climate crisis
40% global carbon emissions from built environment
Operational efficiencies leading to increased awareness of embodied carbon (EC)
EC = emissions due to material extraction, processing, transport, construction, maintenance, EoL, etc.
Units of kgCO2e and colloqiaully refered to as 'carbon'
Structural engineers aware of role in the solution (Structural Engineers Delcare)
Circular economy
3 principles
(Bocken et al., 2016)
Narrowing resource loops
i.e. optimisation / lean design (LD)
A lot of focus on LD in last ~decade
LD = minimising upfront material requirements
Closing resource loops
i.e. design for deconstruction (DfD) and reuse
Recent incrase in discussion of reuse (specifically how to design with reused elements now)
Slowing resource loops
i.e. design for adaptability (DfA)
DfA = designing structures that can adapt to changing context, avoiding obsolescence, resulting in slowing rate of demolition and rebuild
Goes against LD, therefore need to understand balance
Therefore, first need to understand EC cost of DfA strategies
(and, second, need to understand adaptability benefit of DfA strategies)
1.1. DfA strategies
(Watt et al., 2023)
Reserve capacity
Design parameters
Dynamic performance
/ vibration limit
Control of floor vibration such that natural frequency does not equal anticipated loading frequency (to avoid resonance build-up)
Typically achieved by stiffening of beams or increasing mass of floors. Both often result in increased EC
(although not necessarily with stiffening, although can impinge on other non-structural requirements, e.g. structural depth limits)
Concept design vibration limits not codified
Load carrying capacity
i.e. imposed load = anticipated weight experienced during typical building operation (although massively over-conservative)
Requirements codified in Eurocodes
Higher load capacity = stronger structure = more material = increased EC
Performance requirements vary between uses
Overdesigning allows for easy conversion between use types + redundancy to counter deterioration over time
Reserve capacity has anticipated EC burden
Open layouts
Design parameters
Grid arrangement
Defines column spacing and beam spans
Longer beams require progressively more material
Fewer, but higher loaded, columns
Varies with use type and fashion (percieved prestige)
e.g. open-plan/long-span offices in fashion currently
Grid arrangement also impacts EC relationship of the other design parameters
Storey height
i.e. storey height = clear height + service zone + finishes height + structural depth + deflection tolerance
e.g. 2.1–2.5m clear height for resi., 2.5–2.75m for office
e.g. increased cladding area (although beyond scope) and greater buckling capacity for longer columns
Vertical (distance between floors) and horizontal (distance between columns) space
Spatial requirements vary between uses, therefore the more open a space, the more uses provided for
Correlation between EC cost and open layout spec
1.2. EC cost of DfA
State of the art
Limited understanding of EC costs of adaptability
Review of adaptability scoring approach from McFarland et al. (2021)
Adaptability design approaches / future scenarios
Methodology
Four design parameters/variables
Imposed load
Vibration limit
Storey height
Grid arrangement
PANDA tool & baseline design
Description of PANDA
Assessment boundaries / fixed input parameters
LCA
IStructE carbon calculator
A1-5 upfront carbon
Adaptability scoring
Modified from McFarland et al. (2021)
Imposed load
Storey height
Grid arrangement
Added vibration limit scoring
Results
Imposed load
Vibration limit
Storey height
Discussion
Material quantities
EC
Adaptability scoring
Adaptability per EC
Conclusion
Abstract
Key messages
Not all adaptability strategies cost the same
Adaptability strategies are not linear in their benefit
Not possible to quantify single EC cost of adaptability
Research objectives
Refine adaptability scoring
Stepped profiles
To cover all major use types
Quantify material requirements and EC cost of each DfA strategy
Combine 1 and 2 to investigate DfA per EC sweet-spots