Reuse of Structural Steel Yields Significant Environmental Savings

There is growing pressure on the construction industry to be more resource efficient, reduce waste, and lower carbon impacts. The developing circular economy agenda in India and globally is focusing on waste, resource efficiency, recycling and reuse in construction. Increased structural steel reuse supports both these aims.

Waste Hierarchy

What is recycling and reuse?

Reuse and recycling are key stages of the Waste Hierarchy and are the preferred options after all has been done to prevent waste in the first place through design and manufacture.

Most Common Construction Materials

End-of-life Scenario for Steel

Steel Reuse

As distinct from recycling, reuse of construction products involves their reuse with little or no reprocessing. Reuse offers even greater environmental advantages than recycling since there are no (or very few) associated reprocessing that have environmental impacts. For example, reusing a steel beam in its existing form is better than remelting it and rolling a new steel beam, i.e., the energy used to remelt and re-roll the beam is saved.

Structural steel sections are robust and dimensionally stable elements that are generally bolted together to form structural assemblies which are inherently demountable. As such, structural steel is seen as an obvious candidate for reclamation and reuse as opposed to the current, common practice of recycling by remelting. Reusing structural steel yields significant environmental savings compared to recycling.

The realization that the current global consumption patterns are unsustainable leads to the conclusion that it is only a matter of time before reuse of buildings becomes mandatory.

Scope of Reuse

Although complete buildings and different elements of steel buildings can be reused, we will focus on structural building elements reclaimed from existing building structures. The principal focus is the reclamation and reuse of individual members within a new structure, rather than the reuse of an entire building structure in a new location.

The scope of reuse is limited to steelwork:

• which has not been subject to fatigue, e.g., not reclaimed from bridges.
• which has not been subject to significant strains, e.g. plastic hinges.
• without significant loss of section due to corrosion.
• which has not been exposed to fire.
• which are rolled sections but not built-up members.
• which has no splices along the length of the member-individual lengths may be used.

Reusing structural steel

Reusing steel components from existing buildings offers a new point of view on the design and execution of buildings and manufacture of construction products. They are no longer considered as end-products, but instead in the scope of circular economy as a part of continuous chain of the products ecosystem.

The construction and demolition waste becomes a new resource to be considered in the future buildings design. Structural steel is uniquely placed to deliver buildings that are flexible, adaptable, and ultimately reusable. Many steel construction products and components are highly re-usable including:

• Piles (sheet and bearing piles)
• Structural members including hollow sections.
• Light gauge products such as purlins and rails.

The process is straightforward:

• deconstructed sections are inspected to verify their dimensional properties.
• tested to confirm their mechanical properties.
• the section is then generally sand blasted to remove any coatings and refabricated and primed to the requirements of the new project.
• this will usually involve cutting the ends of the beams and columns to the required length.

Design for Deconstruction

Design for deconstruction (and reuse) is central to the circular economy. Current practice, is generally to demolish buildings with little thought about preserving the integrity and value of components for reuse. Only by designing buildings for deconstruction can we make reuse of buildings and building components more commonplace and commercially viable.

The ability to reuse building components is, to a large extent, dependent on how buildings have been constructed in the first place. Although designers routinely consider the constructability of buildings, generally little thought is given to their deconstruction and how elements and components could be reclaimed and reused. At its simplest level, there are two main considerations:

The types of materials and components used; some products, like structural steel, are inherently more reusable than other structural materials and systems.

The way the materials and components are put together (thus able to be taken apart) and deconstructed.

Key Principles

Key principles to follow in design for deconstruction are:

Simplicity – design building systems and interfaces that are simple to understand, with a limited number of different material types and component sizes.

Standardisation and regularity – design building systems and materials that are similar throughout the building and laid out in regular, repeating patterns. Where possible, standardise elements.

Focus is on the design for deconstruction and reuse of loadbearing frames, trusses and secondary elements of single-storey buildings framed in steel. This building type has broad applicability as industrial, commercial, sports, exhibition, warehouse facilities, and shows most potential in suitability for reuse and viability for circular-economy business models.

Design for Reuse

To facilitate greater reuse, it is important that designers optimise future reuse. Steps to maximise the opportunity for reusing structural steel include:

• Minimise the number of different grades of steel and components; fewer larger elements which are more durable and easier and quicker to remove are more likely to be reused.
• Standardise structural grids to facilitate future reuse.
• Optimise span:depth ratios.
• Use long-span beams as they are more likely to allow flexibility of use and to be reusable by cutting the beam to a new length
• Standardise span increments and frame spacing.
• Use bolted connections in preference to welded joints to allow the structure to be dismantled during deconstruction.
• Simplify and standardise connection details including bolt sizes and the spacing of holes. This allows for efficient construction and deconstruction and facilitates reuse without modification after deconstruction
• Standardise bolted haunch connection details.
• Use column base connections which are accessible and demountable.
• Ensure easy and permanent access to connections and their maintenance.
• Where feasible, ensure that the steel is free from coatings or coverings that will prevent visual assessment of the condition of the steel.
• Minimise the use of fixings to structural steel elements that require welding, drilling holes, or fixing with Hilti fasteners; use clamped fittings where possible.
• Identify the origin and properties of the component for example by bar-coding or e- tagging or stamping and keep an inventory of products.

Tata Steel Europe for the use of LCA to demonstrate the impact of the reuse of steel in a world class circular economy building in Holland

Global competition for resources, increasing population and global economic growth cause an increasing pressure on raw materials and ecosystems. This requires a major shift in the design of buildings and choice of materials in order to move to a circular economy.

Tata Steel and the Dutch Steel promotion Institute Bouwen met Staal have adopted new building practices to enable high steel re-use rates. These developments were used in the construction of the new 31,000 m2 Fokker 7/8 Distribution Centre at the International Schiphol Airport, Amsterdam.

Practices Include:

• Demountable connections for beams, columns(no on-site welding, adapted anchor bolts) and cladding(no shot connections)
• Shear stability provided by horizontal steel trusses instead of flooring
• Design using modular/standard beam and column dimensions, lengths, sizes.
• Development of a “Building Material passport” with all steel specifications for future reference and re-use.

A level of re-use of 20-40% gives an 18-36% improvement in the environmental footprint of steel, leveraging the position of steel in material decision making. The project demonstrates the importance of collaboration of LCA experts, marketing and commercial teams, together with customers.

Records

Provide a deconstruction plan outlining general concepts where the load path for the self- weight of structure and deconstruction loads follows conventional paths. Provide specific detailed plans where load paths are not conventional. All load transfer systems should be identified.

Record as-built conditions, i.e., what was built not just what was designed.

Record adaptations to the building over its life.

Ensure information is securely stored and remains accessible.

Documentation

Specifically in relation to structural steel:

• Provide clear documentation of all steel members used in the structure including, size, grade, length, and connection details.
• Keep records of the steel supplied, specifically mill test certificates including manufacturer, production date and standard.
• Ideally steel members should have a permanent marking or tagging to assist in traceability and to identify their chemical and mechanical properties.

Business Model

The demolition contractor reclaims the steelwork from an existing building. The demolition contractor sells the reclaimed steelwork to a stockholder. The stockholder tests and certifies the reclaimed steelwork.

The stockholder sells the certified, reclaimed steelwork to the steelwork contractor. The steelwork contractor fabricates the reclaimed steelwork. Reclamation Process

The overall process from reclamation of steelwork to re-use in another structure is summarised here.

Overall process

1. A building is offered for salvage of the steelwork for reuse. Considerations include the acceptability of the source material, the demountability of the structure, the increased cost of careful demolition, etc.
2. A business case is established between the stockholder and the company responsible for demolition.
3. Important details of the anticipated reclaimed steel are recorded
4. Reclaimed steelwork is received by the stockholder, grouped and listed. The necessary grouping has an important impact on the extent of testing required.
5. Members are inspected and tested, with the information appended to the stock data. The testing regime involves non-destructive and/or destructive testing, with the opportunity to make conservative assumptions about certain material characteristics. The seller of the stock is responsible for declaring the necessary characteristics as the material is sold.
6. Material is sold, with an accompanying declaration of the material characteristics by the holder of the reclaimed stock. The declaration covers all relevant material properties which allow the fabricated steelwork to be certified.
7. Structural design and member verification are completed with certain modifications, following the recommendations provided .

Data Records

The following data should be recorded and associated with each structural member:

Building information

• Building age, location
• Form of construction, e.g. braced, continuous, etc.
• Any related information, such as drawings, modifications, records.

Individual members

• Section size,
• Length,
• Group
• Member individual identification
• Tolerance check (section dimensions and bow imperfections)
• Comments, e.g. stiffeners or fabricated features
• Coating; Coating type (and thickness if determined),
• Condition of coating

Material Properties

Material properties shall be determined by non-destructive tests and/or by destructive tests. The test results, together with any derived values, shall be recorded for the following properties:

• Yield and ultimate strengths (non-destructive and destructive tests)
• Elongation (destructive tests)
• Chemical composition (non-destructive and destructive tests)
• Carbon Equivalent Value (CEV)
• Impact toughness (by destructive tests, if required).

Barriers to Reuse

Barriers in descending order of importance, are:

• Availability of reclaimed sections; particularly of the desired size, volume and in the right location
• Issues relating to the quality, traceability and certification of reclaimed sections.
• Additional cost associated with using reclaimed sections
• (Lack of) supply chain integration; particularly communication and sharing information through the supply chain and trust (and risk sharing) between companies
• Additional time required within construction programmes to allow for using reclaimed steel; in general, additional time incurs additional cost
• Reclaiming and reusing structural steel is a relatively uncommon practice and many organisations simply do not have the skills or experience to do it
• The perception that reclaimed steel is somehow inferior to new steel sections.

Overcoming Barriers

BIM technologies overcome several of the barriers to steel reuse by providing certainty about material properties, origin, traceability and eliminating the need for testing. Looking ahead therefore, structural steel (BIM) models offer a cost-effective means of enabling future reuse.

Steelwork contractors have been using BIM models for years and routinely offer their clients as-built structural models on building handover. By storing such models in a secure database, this will future-proof steel structures by enabling:

• efficient refurbishment and structural extension of existing structures
• safe deconstruction
• a detailed inventory of reclaimed steel sections for future use (with full traceability and all relevant material properties)
• optimising the recycling process through knowledge of the metallurgy of the steel.

Future Outlook

Significant scope for increasing reuse of steel construction products and work is underway within the sector to promote and facilitate this.

The proportion of recovered products that are reused will increase as design for deconstruction is better understood and a stronger market for reusable steel construction products is stimulated.

Acknowledgement: The article has been reproduced from the proceeding of the workshop ‘Steel for Sustainable Development’ organised by INSDAG, CEAI-WRC and IIT Bombay and at IIT Bombay on 4 February 2023.

References

The Steel Construction Institute (SCI) UK:

Structural Steel Reuse -Assessment, Testing and Design Principles P427 2019

The British Constructional Steelwork Association Ltd (BCSA) UK:

Model specification for the purchase of reclaimed steel sections 2022

European Convention for Constructional Steelwork (ECCS):

European Recommendations for Reuse of Steel Products in Single-Storey Buildings 2020.

About Author: Charles Simoes is an Independent Expert. As an Adjunct Faculty at Sardar Patel College of Engineering, Mumbai he teaches Master of Technology students in Structural Engineering and Construction Management. He holds a Bachelor's degree in Civil Engineering from VJTI, Mumbai, a Master of Technology degree in Structural Engineering from IIT Bombay, and a Master of Financial Management from Jamnalal Bajaj Institute of Management Studies, Mumbai. He is a Fellow of the Institution of Engineers, India.

During his professional career of over 35 years at Tata Consulting Engineers and Aker Solutions, Mumbai, he held leadership positions like Associate Director and Head of Civil, Structural and Architectural Engineering.

He has been actively involved in the design, fabrication and erection of major and challenging steel structures, both ‘stick-built’ and modular, for prestigious mega grass-root Oil Refineries, Gas, Offshore Platforms, Petrochemical, Chemical and Metals Projects for reputed clients in India, North, Central & South America, Europe, Africa, Middle-East, East Asia and Australia. He has a wide knowledge of Indian, American, European, British and other International Steel Standards and Codes.

He is also involved in training, mentoring and coaching engineers over several years and keeps abreast with the latest developments and technologies pertaining to structural steel.