Building a safer world

Skyscrapers
Professor Faris Ali
Professor Faris Ali
Faris Ali, Professor of Structural Engineering at the University of Ulster, details the complexities of producing suitable construction materials in the modern age…

The need to enhance the protection and performance of structures under extreme situations is rapidly increasing as such incidents are becoming more frequent in the modern world. A blast can take place in a domestic or industrial environment, or it can be caused by a terrorist attack. Moreover, it is more likely that a blast will trigger a fire than a fire triggering a blast.

The tragic September 11th attacks are perhaps the most pertinent examples of blast events accompanied by fire. It is now clear that fire was the main cause of the collapse of the two towers
Professor Faris Ali
The tragic September 11th attacks are perhaps the most pertinent examples of blast events accompanied by fire. It is now clear that fire was the main cause of the collapse of the two towers. The effects of fire were most evident in the 47-storey third tower that was brought down approximately seven hours after the twin towers. The 1995 Oklahoma bombing is another example of the devastating effect of blast forces. The blast shock wave was triggered by the detonation of 1,814kg of TNT at a 4.5m standoff distance, and caused devastating destruction to the surrounding buildings.

In recent years, there have been notable attempts to address the issue of fire-blast resistance, by developing blast mitigation methods that can also provide some resistance to fire. Some of the methods available use steel (or a core material covered with steel) as the main material of blast walls. Although steel has a high resistance to blast forces, its very heavy weight (7.8ton per m3) can cause difficulties with handling and installation. Steel also has very poor insulation properties, which means that it can assist the spreading of a fire by thermal conductivity.

Concrete has also been used in blast walls. Although it is approximately three times lighter than steel, it has two major drawbacks. Firstly, it is very brittle and, therefore, prone to fragmentation during blasts. Secondly, it is susceptible to explosive spalling when subjected to fire. A good example is the M1 fire at Watford in April 2011, which resulted in the motorway's closure due to structural damage caused by the explosive spalling of concrete.

A third approach uses purposely developed materials, or sandwich panels, that contain multilayers of various materials. In general, the costs associated with this group tend to be very high and usually involve the use of resin or polyethylene-based ingredients to assist in the absorption of the blast's shock wave. However, such components can be compromised by fire, as they melt at approximately 160°C. This makes them functionless under fire, particularly if the fire takes place before the blast. The cost of any blast protection system can be an important parameter when being widely used to provide safer environments. The challenge is to produce a system that is cost effective, capable of resisting blasts and fires, and that is logistically viable.

Terrorist attack on World Trade Center
After years of intensive research, the Fire-Blast Protection System (FBPS) was developed at the University of Ulster. The FBPS aims to provide protection for people, buildings (industrial/military) and infrastructure facilities (including tunnels) in events of blasts, fires, and a combination of the two.

The system is based on using low-cost concrete panels that provide a superior 'panel thickness to blast resistance' ratio. This allows for a significant reduction in panel thickness, and consequently a reduction in weight and cost. The developed panels have shown very high ductility when compared with other types of concrete panels, allowing the FBPS panels to behave like steel rather than concrete. Tests have shown that the panels have approximately 12 times higher ductility than standard concrete panels, including Ultra-High Performance Fibre Reinforced Concrete (UHPFRC).

Impact-Deformation Graph
This graph shows the superior capacity of the new concrete to absorb an impact's energy, compared to UHPFRC. The FBPS panels have demonstrated high ductility with a 10º rotation at supports without failure, which, when added to their resistance to fragmentation, makes them capable of providing excellent protection against blast forces.

The preliminary tests have shown that 25mm thick panels can withstand an impact equivalent to a blast of 500kg of TNT at a 30m standoff distance, making them compliant with US Department of Defense UFC 3-340-02 blast deflection response criteria. The panels can withstand higher blast pressures by increasing their thickness. The panels also provide fire resistance as they are immune to the explosive spalling that concrete is prone to under extreme heat. The FBPS panels are non-combustible, which makes them ideal for fire situations. Their ability to slow the progress of fire is one advantage of the FBPS panels over existing blast-proof materials. In addition, the panels have very good thermal insulation properties, enabling them to function as fire wall barriers.

The 'panel thickness to blast resistance' ratio provided by the FBPS system allows the panels to be produced in various thicknesses to resist a wide range of blast forces. For example, if the system is used for cladding or protecting existing walls, the panels can be 10-25mm thick. If the system is to be used to erect a new building, the panels can be manufactured in larger thicknesses such as 50-100mm. The relatively small thickness of the panels makes them lightweight and logistically efficient. Their ability to resist fire and blast forces, their low cost, their light weight and narrowness, make FBPS panels unique.

The panels are also ideal for use in other construction situations, including reinforcing and rehabilitating damaged structural elements. The panels can be fitted on building facades, internal walls and ceilings that are considered to be vulnerable to fire or explosion. In cases of cladding or protecting existing walls, the system can be provided onsite by fitting it into a frame.

SDOF system
Experimental research at Ulster has been supported by a numerical finite element study. This panel model allowed various intensities of blast loads to be investigated. The blast analysis was based on using the SDOF system and the idealised blast curve is illustrated in the image below.

The concept of this invention is protected by a patent. It is also being developed as a full military construction system. This system will enable the swift response to operational needs and will facilitate the fast erection of military units, including field administrative facilities, ammunition storage facilities, bunkers and other premises.

I believe that the introduction of this system will significantly enhance the safety of domestic and industrial buildings alike.

COMMENTS


(NOT DISPLAYED)




YOUR COMMENT WILL BE APPROVED BY A MODERATOR
HTML CODE IS NOT PERMITTED.
Thank you for your article, it gives a good brief about existing methods about providing fire and blast resistance construction materials.
I did design in the past a building to resist certain scenarios of blasts and it could be very relieving had the FBPS was available then. I have few questions regarding this system, and they are as follow:
1-Is this system commercially available and how adaptive it can be to normal construction usages?
2- What are the cost implications of this system for the short and long term impact?
3- I'm assuming that these panels needs to span certain distances and to be supported on a structure that can take the reactions, are such details available and has there been a study on practicality issues?
4- How adaptable these panels are to architectural finishes?

Thank you again for your article wishing you all the best with your efforts.
Nadeem

Nadeem Kamala - Libreville - Gabon
Faris
I can see you did great things, congragultions!

Amer
Amer Jalil - Iraq
Thank you Nadeem for your comments about the article. In relation to your questions I will to address them below
1. The system is still not available commercially and should be easily used in normal civil constructions
2. The system is much cheaper than any existing systems. The cost of the FBPS system can be 80% cheaper than other similar systems.
3. Yes the design approach is that the structure's frame provides the support for the blast reaction forces. There are currently preparations for further tests to address this issue.
4. The panels are very adaptable to architectural needs. It can be painted plastered, rendered, etc
I hope that I was able to respond to your questions and thank you again for the valuable and constructive comments.

Faris

Faris Ali - UK
Thank you for interesting and innovative material. The comparison presented in Fig. 1 is impressive. I can see a big potential for the FBPS panels and I hope they will be quickly applied in civil structures. I am looking forward to seeing your next research papers covering this topic.
Leslaw Kwasniewski - Warsaw, Poland
That's a genuinely imperssive answer.
Eloise - Unknown
Faris, well - great thing! My congratulations! It's really impressive. Implementation of the FBPS will solve many design problems and create pretty new possibilities of adapting existing building to contemporary threats, allowing for increasing their functionality as well. I'll be waiting for your new spectacular research results. Let me wish you all the best and a lot of success in your efforts.
Pawel A. Krol - Warsaw, Poland
Dear Prof. Faris Ali,

Accept my heartiest congratulations in offering to the world a great innovative system the Fire-Blast Protection System (FBPS). I am very happy to note that this concept is protected by a patent, I congratulate you and your group in evolving this system. I beleive it would definitely revolutionize the specific needs of man-kind. I beleive that cost should not be a serious concern, as it is required to be functional, catering to both fire loads and blast loads, no doubt one's investment shall be expected to be higher, demanding higher performance.

I am delighted to go through the the technical aspects of the innovative material to absorb impact. Undoubtedly, it is great concept and an invention that you must be proud of.

I wish that this proposed material would soon capture the minds of the construction industry and would definitely make its impact of your hard earned contribution to all of us in general.

Wishing you good luck in the days ahead.

Dr. Subhash C. Yaragal
B.E (NITK), M.E. (IISc.), Ph.D (IISc.), Post Doc. (Japan)
Associate Dean (Academic) and
Associate Professor
Department of Civil Engineering
National Institute of Technology Karnataka
Surathkal, PO: Srinivasnagar - 575 025
Karnataka, India.

e-mail: subhashyaragal@yahoo.com


Prof. Subhash C. Yaragal - Karnataka State, India
Very interesting indeed!
What was the size of the panel used in the preliminary test?
How was it supported?What were the supporting elements?
How did the supporting elements behave?
Can the concrete, adopted in the panel be shotcreted?

Congrats for the innovation and wish you the very best in all your future endeavours.

Dr.K.S.Babu Narayan
Associate Professor
Department of civil engineering
National Institute of Technology Karnataka,Surathkal
Srinivasnagar,mangalore-575 025,India.
Dr. K.S. BABU NARAYAN - MANGALORE, INDIA
Excellent article, and very well presented results.
It shows that this is not just useful in a military but also civilian setting.

I'll make sure any house I move into is made of this stuff.

Yassir Al-Refaie
Yassir Al-Refaie - Sawbridgeworth, UK
Thank you for your article. Wishing you all the best with your efforts. It gives a good brief about existing methods about providing fire and blast resistance construction materials.

Azi_Momtaz - Jahrom, Iran
Back to comment form
I'm sorry, I don't quite understand. Is this new organisation - set up obviously at enormous public expense - going to solve/cure/repair climate change or is it just an exercise in institutionalised handwringing with accompanied academic career building - with a logo attached?


Commented Roger Breeze on
Met Office launches Climate Service UK

publicservice.co.uk Ltd, Ebenezer House, Ryecroft, Newcastle-under-Lyme, Staffordshire ST5 2UB
Tel: +44 (0)1782 741785, Fax: +44 (0)1782 631856, www.publicservice.co.uk
Registered in England and Wales  Co. Reg No. 4521155   Vat Reg No. 902 1814 62