Re-evaluating the design life of buildings - Revision history

Designing Buildings at 06:59, 25 February 2021

2021-02-25T06:59:11Z

← Older revision		Revision as of 06:59, 25 February 2021
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	* Temporary structure.		* Temporary structure.

−	[[Category:Construction_management]] [[Category:Construction_techniques]] [[Category:Cost_/_business_planning]] [[Category:Design]]	+	[[Category:DCN_Commentary]] [[Category:DCN_Guidance]] [[Category:Construction_management]] [[Category:Construction_techniques]] [[Category:Cost_/_business_planning]] [[Category:Design]]

Editor at 12:29, 20 July 2020

2020-07-20T12:29:37Z

← Older revision		Revision as of 12:29, 20 July 2020
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	* Design quality for buildings.		* Design quality for buildings.
	* Fitness for purpose.		* Fitness for purpose.
		+	* ICE articles on Designing Buildings Wiki.
	* Resilience.		* Resilience.
	* Service life.		* Service life.

Editor at 12:11, 20 July 2020

2020-07-20T12:11:50Z

← Older revision		Revision as of 12:11, 20 July 2020
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−	[[File:DesignLife.png]]	+	[[File:DesignLife.png\|link=File:DesignLife.png]]

	= Introduction =		= Introduction =
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	= Related articles on Designing Buildings Wiki =		= Related articles on Designing Buildings Wiki =
		+
		+	* Concept structural design of buildings.
		+	* Design life.
		+	* Design quality for buildings.
		+	* Fitness for purpose.
		+	* Resilience.
		+	* Service life.
		+	* Temporary structure.

	[[Category:Construction_management]] [[Category:Construction_techniques]] [[Category:Cost_/_business_planning]] [[Category:Design]]		[[Category:Construction_management]] [[Category:Construction_techniques]] [[Category:Cost_/_business_planning]] [[Category:Design]]

Editor at 12:08, 20 July 2020

2020-07-20T12:08:16Z

← Older revision		Revision as of 12:08, 20 July 2020
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		+	[[File:DesignLife.png]]
		+
	= Introduction =		= Introduction =

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	Understanding the meaning of 'design life' and its influence over design decisions can help engineers optimise economies of scale.		Understanding the meaning of 'design life' and its influence over design decisions can help engineers optimise economies of scale.

−	It’s just like designing a phone-case!	+	It’s just like designing a phone case!

−	To explain my theory, I’d like to make a phone case analogy! If you were to design a phone case, you probably wouldn’t need it to be bullet-proof. But it is probably reasonable to design it to survive a drop from a height of 1.5m, which is the scenario the phone is likely to experience (slipping out of a hand when using the phone for example).	+	To explain my theory, I’d like to make a phone case analogy. If you were to design a phone case, you probably wouldn’t need it to be bullet-proof. But it is probably reasonable to design it to survive a drop from a height of 1.5m, which is the scenario the phone is likely to experience (slipping out of a hand when using the phone for example).

−	There is a spectrum of possible design qualities of phone cases, ranging from surviving meteor impact, down to being broken by accident. Likewise with buildings. Where your design lands on the spectrum depends on the engineer making sound discretionary decisions, on a case-by-case basis. In a nutshell, ‘What is your structure designed to survive?	+	There is a spectrum of possible design qualities of phone cases, ranging from surviving meteor impact down to being broken by accident.

−	~~Functionality and serviceability~~	+	Likewise with buildings. Where your design lands on the spectrum depends on the engineer making sound discretionary decisions on a case-by-case basis. In a nutshell, ‘What is your structure designed to survive?'

−	A one-year structure is likely to be a temporary work with a fundamentally different design requirement compared to a permanent work. The one-year structure is most likely to have no permanent, serviceability requirements, such as aesthetics, cracks and ~~water tightness.~~	+	= Functionality and serviceability =

−	What the structure will go through?	+	A one-year structure is likely to be a temporary work with a fundamentally different design requirement compared to a permanent work. The one-year structure is most likely to have no permanent, serviceability requirements such as aesthetics, cracks and water tightness.
		+
		+	= What the structure will go through? =

	Overall, the engineer needs to consider what scenarios the structure is likely to experience during its lifespan. What loadings is it required to resist? What environmental change is it likely to experience? What changes will the construction material experience over time?		Overall, the engineer needs to consider what scenarios the structure is likely to experience during its lifespan. What loadings is it required to resist? What environmental change is it likely to experience? What changes will the construction material experience over time?
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	Some loadings or risks only exist in the long term. For example, you may wish to design against the rise of sea levels for a marine structure. You may also choose to disregard a 100-years return earthquake period if you were to design a structure with a one-year design life, as it is unlikely to happen.		Some loadings or risks only exist in the long term. For example, you may wish to design against the rise of sea levels for a marine structure. You may also choose to disregard a 100-years return earthquake period if you were to design a structure with a one-year design life, as it is unlikely to happen.

−	The ‘behavioural problem’ over the long term	+	= The ‘behavioural problem’ over the long term =

	Some construction materials exhibit time-dependent behaviour, such as creep and drying shrinkage of concrete. The effects from such behaviours only start to become significant in the long term. Creep and drying shrinkage of concrete depends on several factors including the ambient temperature, humidity and concrete strength.		Some construction materials exhibit time-dependent behaviour, such as creep and drying shrinkage of concrete. The effects from such behaviours only start to become significant in the long term. Creep and drying shrinkage of concrete depends on several factors including the ambient temperature, humidity and concrete strength.

−	Natural materials such as soil exhibit time-dependent behaviour too, including consolidation, stress relaxation and creep. Consolidation of soil is the drainage of pore water when the ground is being squeezed. If the ground is relatively impermeable then the ground behaviour is closer to an ‘undrained’ condition, rather than ‘drained’, as there is not enough time for pore water to escape under the pressure. Stress relaxation is the ‘internalization’ of the deformation of soil particles, i.e. some elastic deformation turns into plastic deformation. Creep is the slow and gradual increase of deformation when subject to the same loads over the long term.	+	Natural materials such as soil exhibit time-dependent behaviour too, including consolidation, stress relaxation and creep. Consolidation of soil is the drainage of pore water when the ground is being squeezed. If the ground is relatively impermeable, then the ground behaviour is closer to an ‘undrained’ condition rather than ‘drained’, as there is not enough time for pore water to escape under the pressure.

−	~~Durability~~ of ~~different parts~~	+	Stress relaxation is the ‘internalisation’ of the deformation of soil particles, i.e. some elastic deformation turns into plastic deformation. Creep is the slow and gradual increase of deformation when subject to the same loads over the long term.

−	~~Not all parts~~ of ~~the structure are born equal. Some auxiliary~~ parts of the structure may have a much shorter design life compared to the main part of the structure. For example, joint sealants may have a design life of 20 years. Bridge bearings may have a life span of 20-45 years. If the whole structure is designed to last for 120 years, the design may be required to eliminate the use of these or have a service plan to inspect and replace them. If the structure is designed for one year's use only, you may choose cheaper alternatives or simply ignore them if you can.	+	= Durability of different parts =

−	~~End-~~of-life ~~considerations~~	+	Not all parts of the structure are born equal. Some auxiliary parts of the structure may have a much shorter design life compared to the main part of the structure.

−	~~Since~~ the structure is ~~intended~~ to ~~be used~~ for ~~one year only~~, the ~~designer ought~~ to ~~take into consideration~~ the ~~imminent de-commissioning~~ of the structure. Reusable materials with an ease of dismantling such as metals, rather than concrete, are more likely to be used to achieve economies of scale. The consideration on de-commissioning would be a much less serious consideration for ~~a 120-~~year ~~structure as your guess on the state of available technology~~ can ~~be wildly off~~.	+	For example, joint sealants may have a design life of 20 years. Bridge bearings may have a lifespan of 20 to 45 years. If the whole structure is designed to last for 120 years, the design may be required to eliminate the use of these or have a service plan to inspect and replace them. If the structure is designed for one year's use only, you may choose cheaper alternatives or simply ignore them if you can.

−	~~It’s all about the quality!~~	+	= End-of-life considerations =

−	‘Quality’ here does not just mean workmanship; a trendy buzzword for ‘resilience’. How critical is the structure? What is the impact of structural failure? Answering questions such as these will give you an indication on the risk tolerance and influence how much ‘resilience’ is required on the structure, which all translates into structure quality at the end of the day.	+	Since the structure is intended to be used for one year only, the designer ought to take into consideration the imminent de-commissioning of the structure. Reusable materials with an ease of dismantling such as metals, rather than concrete, are more likely to be used to achieve economies of scale.
		+
		+	The consideration on de-commissioning would be a much less serious consideration for a 120-year structure as your guess on the state of available technology can be wildly off.
		+
		+	= It’s all about the quality! =
		+
		+	‘Quality’ here does not just mean workmanship - a trendy buzzword for ‘resilience’. How critical is the structure? What is the impact of structural failure?
		+
		+	Answering questions such as these will give you an indication on the risk tolerance and influence how much ‘resilience’ is required on the structure, which all translates into structure quality at the end of the day.

	-----		-----
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	= Related articles on Designing Buildings Wiki =		= Related articles on Designing Buildings Wiki =
		+
		+	[[Category:Construction_management]] [[Category:Construction_techniques]] [[Category:Cost_/_business_planning]] [[Category:Design]]

Editor at 11:55, 20 July 2020

2020-07-20T11:55:21Z

← Older revision		Revision as of 11:55, 20 July 2020
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−	Introduction	+	= Introduction =

−	~~Civils~~ structures can typically have an intended ‘design life’ of up to 120 years. But, asks Structural Engineer Rifat Bin Ahmed, what does ‘design life’ mean? What if you were to reduce a structure’s design life down to one year? What design criteria could be relaxed? And could this save money?	+	Civil structures can typically have an intended ‘design life’ of up to 120 years. But, asks Structural Engineer Rifat Bin Ahmed, what does ‘design life’ mean? What if you were to reduce a structure’s design life down to one year? What design criteria could be relaxed? And could this save money?
		+
		+	= What is design life? =

	Understanding the meaning of 'design life' and its influence over design decisions can help engineers optimise economies of scale.		Understanding the meaning of 'design life' and its influence over design decisions can help engineers optimise economies of scale.
Line 7:		Line 9:
	It’s just like designing a phone-case!		It’s just like designing a phone-case!

−	To explain my theory, I’d like to make a phone case analogy! If you were to design a phone case, you probably wouldn’t need it to be bullet-proof. But it is probably reasonable to design it to survive a drop from a height of 1.5m, which is the scenario the phone is likely to experience (slipping out of a hand when using the phone for example). There is a spectrum of possible design qualities of phone cases, ranging from surviving meteor impact, down to being broken by accident. Likewise with buildings. Where your design lands on the spectrum depends on the engineer making sound discretionary decisions, on a case-by-case basis. In a nutshell, ‘What is your structure designed to survive?	+	To explain my theory, I’d like to make a phone case analogy! If you were to design a phone case, you probably wouldn’t need it to be bullet-proof. But it is probably reasonable to design it to survive a drop from a height of 1.5m, which is the scenario the phone is likely to experience (slipping out of a hand when using the phone for example).
		+
		+	There is a spectrum of possible design qualities of phone cases, ranging from surviving meteor impact, down to being broken by accident. Likewise with buildings. Where your design lands on the spectrum depends on the engineer making sound discretionary decisions, on a case-by-case basis. In a nutshell, ‘What is your structure designed to survive?

	Functionality and serviceability		Functionality and serviceability
Line 36:		Line 40:

	‘Quality’ here does not just mean workmanship; a trendy buzzword for ‘resilience’. How critical is the structure? What is the impact of structural failure? Answering questions such as these will give you an indication on the risk tolerance and influence how much ‘resilience’ is required on the structure, which all translates into structure quality at the end of the day.		‘Quality’ here does not just mean workmanship; a trendy buzzword for ‘resilience’. How critical is the structure? What is the impact of structural failure? Answering questions such as these will give you an indication on the risk tolerance and influence how much ‘resilience’ is required on the structure, which all translates into structure quality at the end of the day.
		+
		+	-----
		+	This article originally appeared on the [https://www.ice.org.uk/news-and-insight/ice-community-blog/july-2020/reevaluating-the-design-life-of-buildings ICE Community Blog] on 13 July 2020. It was written by Rifat Bin Ahmed, Structural Engineer, Builtech Consulting Engineers.
		+
		+	--[[User:Institution_of_Civil_Engineers\|Institution of Civil Engineers]]
		+
		+	= Related articles on Designing Buildings Wiki =

Editor: Created page with "Introduction Civils structures can typically have an intended ‘design life’ of up to 120 years. But, asks Structural Engineer Rifat Bin Ahmed, what does ‘design life’ me..."

2020-07-20T11:45:23Z

Created page with "Introduction Civils structures can typically have an intended ‘design life’ of up to 120 years. But, asks Structural Engineer Rifat Bin Ahmed, what does ‘design life’ me..."

New page

Introduction

Civils structures can typically have an intended ‘design life’ of up to 120 years. But, asks Structural Engineer Rifat Bin Ahmed, what does ‘design life’ mean? What if you were to reduce a structure’s design life down to one year? What design criteria could be relaxed? And could this save money?

Understanding the meaning of 'design life' and its influence over design decisions can help engineers optimise economies of scale.

It’s just like designing a phone-case!

To explain my theory, I’d like to make a phone case analogy! If you were to design a phone case, you probably wouldn’t need it to be bullet-proof. But it is probably reasonable to design it to survive a drop from a height of 1.5m, which is the scenario the phone is likely to experience (slipping out of a hand when using the phone for example). There is a spectrum of possible design qualities of phone cases, ranging from surviving meteor impact, down to being broken by accident. Likewise with buildings. Where your design lands on the spectrum depends on the engineer making sound discretionary decisions, on a case-by-case basis. In a nutshell, ‘What is your structure designed to survive?

Functionality and serviceability

A one-year structure is likely to be a temporary work with a fundamentally different design requirement compared to a permanent work. The one-year structure is most likely to have no permanent, serviceability requirements, such as aesthetics, cracks and water tightness.

What the structure will go through?

Overall, the engineer needs to consider what scenarios the structure is likely to experience during its lifespan. What loadings is it required to resist? What environmental change is it likely to experience? What changes will the construction material experience over time?

Some loadings or risks only exist in the long term. For example, you may wish to design against the rise of sea levels for a marine structure. You may also choose to disregard a 100-years return earthquake period if you were to design a structure with a one-year design life, as it is unlikely to happen.

The ‘behavioural problem’ over the long term

Some construction materials exhibit time-dependent behaviour, such as creep and drying shrinkage of concrete. The effects from such behaviours only start to become significant in the long term. Creep and drying shrinkage of concrete depends on several factors including the ambient temperature, humidity and concrete strength.

Natural materials such as soil exhibit time-dependent behaviour too, including consolidation, stress relaxation and creep. Consolidation of soil is the drainage of pore water when the ground is being squeezed. If the ground is relatively impermeable then the ground behaviour is closer to an ‘undrained’ condition, rather than ‘drained’, as there is not enough time for pore water to escape under the pressure. Stress relaxation is the ‘internalization’ of the deformation of soil particles, i.e. some elastic deformation turns into plastic deformation. Creep is the slow and gradual increase of deformation when subject to the same loads over the long term.

Durability of different parts

Not all parts of the structure are born equal. Some auxiliary parts of the structure may have a much shorter design life compared to the main part of the structure. For example, joint sealants may have a design life of 20 years. Bridge bearings may have a life span of 20-45 years. If the whole structure is designed to last for 120 years, the design may be required to eliminate the use of these or have a service plan to inspect and replace them. If the structure is designed for one year's use only, you may choose cheaper alternatives or simply ignore them if you can.

End-of-life considerations

Since the structure is intended to be used for one year only, the designer ought to take into consideration the imminent de-commissioning of the structure. Reusable materials with an ease of dismantling such as metals, rather than concrete, are more likely to be used to achieve economies of scale. The consideration on de-commissioning would be a much less serious consideration for a 120-year structure as your guess on the state of available technology can be wildly off.

It’s all about the quality!

‘Quality’ here does not just mean workmanship; a trendy buzzword for ‘resilience’. How critical is the structure? What is the impact of structural failure? Answering questions such as these will give you an indication on the risk tolerance and influence how much ‘resilience’ is required on the structure, which all translates into structure quality at the end of the day.