Stronger than the wall. We discuss the prospects of blast resistant design with Reynaers experts

The design of buildings resistant to extreme loads, in particular to the impact of a blast wave, the so-called blast resistant design, is one of the priorities in a troubled world. In Ukraine, for obvious reasons, even more so. 

A year of living in war conditions showed that the aggressor's plans to morally break Ukrainians and drive them underground, into basements and bunkers, did not come true. Ukrainians stubbornly return to their apartments after the alarm goes off, put things in order, make plans for the future. Ukrainian architects are designing new buildings with floor-to-ceiling windows in breakpoints and bomb shelters in the pauses between air raids and blackouts.

How to make these windows as safe and sustainable as possible in today's extreme conditions? Are new technologies able to respond to this non-standard life challenge? The experts of "Raynars Aluminum" LLC spoke about the extraordinary capabilities of modern fencing systems.

CROWNE PLAZA Hotel, Liege, Belgium. Reynaers Group fencing systems were used in the implementation of the project. The Forster thermfix vario system is heat-insulated, fireproof, burglar-resistant, and bulletproof. Image source: Reynaers Aluminum

Bravado, but not without reason

Windows and doors are one of the strongest and most meaningful symbols in culture. A symbol of the connection between the outer and inner world, a border, a portal. The cross-shaped window has become a symbol of war - both of the Second World War and the current one. Over the past year, Ukrainians have become real experts in the topic of "how to turn your home into a relatively safe fortress." Even children and pets have learned the two-wall rule.

In the list of priorities, safety has taken the first position, and people attach more and more meanings to this very word

Back in 1936, Spanish designers, in response to Franco's merciless bombings, turned shop windows into futuristic displays with complex graphics made of paper strips.

Ukrainian artists saw a symbol of hope in the random graphics of the broken windows of the "Ukrainian House" in Kyiv and created the cultural manifesto "Windows": "We are learning to live with war. We don't get used to it - we accept it. And the fact that we see birds in broken windows is proof that we are alive. We want to see beauty. This is our resource for active action. Therefore, "Windows" is our manifesto. We will glass our windows. We will rebuild the country. We will survive, win and be happy."

Injured as a result of the bombing of the window of the Ukrainian House, Kyiv. Photo: Olga Vieru

In post-war London, modernist towers of glass and steel were erected on the site of buildings destroyed during the Blitz and other air raids. New York developers responded to the 11/XNUMX attacks by creating hundreds of new high-rise landmarks. Ukrainians are preparing for the Great Renovation, and it has already begun in the western regions.

Such a reaction is not only a demonstration of the strength of spirit and love of life of the nation. There is reason to believe that technologists, engineers and architects will find a way to create safe housing without all the money in the world. Scientific papers, symposia, and conferences in various countries of the world are devoted to the topic of creating safe enclosing structures — windows, doors, and facades. This is relevant. For Ukrainians, it is three times more important.

Forster thermfix vario facades in the implementation of the clinic project. Image source: Reynaers Aluminum

A dynamic storm

The blast wave, which is the main cause of destruction and damage to buildings within a radius of hundreds of meters from the place of explosion or falling projectile, is insidious. A high-pressure front spreads faster than sound and damages surrounding structures in a few milliseconds.

The blast wave first pushes the windows inside the building, and then under the influence of negative pressure, they bend outward. The blast wave is followed by hurricane-force winds that overturn cars, tear off roofs, and carry a mass of dangerous debris. Any obstacle, including the window system itself, dampens the dynamic force of the blast wave and works as protection.

The task with an asterisk is to design the containment structures in such a way that they can withstand the excess pressure and subsequent bombardment with debris

Damage and the risk of personal injury can be minimized by using explosion-proof glazing that can crack but remain fixed in the frame or facade. This is exactly what the developers are striving for.

The impact of a blast wave on buildings and structures is complex physics. In the best research institutes in the world, they study what happens in those milliseconds when the blast wave hits the building and is reflected from all its corners and depressions. This is not just a sudden pressure drop - every detail of the surrounding landscape, the material of the surfaces, their orientation form an individual picture of the explosion. Paradoxes occur when reinforced concrete collapses, but a kitchen cabinet with plates and a ceramic rooster remains intact.

Simulating such situations requires a lot of computer time, but this is also done in Reynaers Aluminum's test center located at the company's headquarters in Belgium. Previously, PRAGMATIKA.MEDIA wrote about the unique testing process in the article "Anti-brittleness. Reynaers on safe glazing".

Test results of a sample of the Forster enclosure structure at the Reynaers Aluminum test center. Image source: Reynaers Aluminum

What can be opposed to extreme loads?

Architectural consultant of Raynars Aluminum LLC Dmytro Kaladzhiev confirmed that today the issue of security is becoming a key issue for customers on the Ukrainian market: "After the renewal of construction and reconstruction of buildings damaged by the Russian-Ukrainian war, the demand for Reynaers Aluminum bulletproof systems with the BP (Bullet Proof) index and anti-burglary modifications of systems with the AP index has increased among private customers (Anti-burglar Proof). It is obvious that the motivation for applying this or that decision is different. Bulletproof windows are used in order to save life and property during direct combat operations around the construction site. In addition, such windows will withstand the blast wave at the same level as general building wall structures.

Dmytro Kaladzhiev, architectural consultant of the Reynaers company

Windows from anti-burglary systems in combination with double-glazed windows of increased strength and safety will be able to stop burglary without the use of firearms, and will also withstand the impact of an explosive wave, from which we see the destruction of window structures almost every day."

CS 77 – BP (Bullet proof) external view

Hryhoriy Didyk, technical director of Raynars Aluminum LLC, agrees with his colleague: "In my opinion, safety can be the number one priority requirement for fencing structures. When a person feels safe, he can calmly work, develop, worry about his family, etc. Reynaers systems provide solutions for increasing the safety of structures: these are locks, fittings, handles, and special profiles. Many systems are tested according to classifications RC2, RC3, WK2, WK3 - this is a medium and high class of protection against hacking.

Hryhoriy Didyk, technical director of Reynaers

The resistance of glass to dynamic loads is higher than it seems at first glance, especially reinforced architectural glass, which is used to create facades and shop windows. But it is important that the entire structure has the appropriate indicators of strength, elasticity and plasticity. The situation when the frame is completely removed is even more dangerous, and the repair process will be more difficult and expensive.

In principle, how strong can windows be today? Are there technologies that allow you to strengthen the window blocks to the strength of the wall?

"The strength of transparent structures consists of the strength of the profile system, the strength of the glass units and the strength of the mounting fasteners. Reynaers Aluminum has a range of systems for installation in regions with extreme hurricane and earthquake conditions. The use of such specialized systems has proven their high profitability. This is achieved by balancing the high one-time cost of such systems and the degree of risk regarding the probability of the occurrence of extreme calculation extremes, in which the glazing structure collapses, - explains the architectural consultant Kaladzhiev. — Considering the year of the war, it can be said that the double-glazed windows were primarily damaged by the blast wave.

If double-glazed windows of increased strength were installed, sometimes the window frames do not withstand - in the event of such damage Raynars Aluminum LLC in Ukraine has the most complete stock of plugs and corresponding seals for the most prompt replacement. There are likely cases when double-glazed windows and shutters withstood the impact, and the weakest link was the window hardware of the turn-and-turn sashes, all parts for which we also have in stock.

CS 77 – BP (Bullet proof)

The most obvious solutions at the moment to prevent the destruction of window structures from the blast wave will be to increase the calculated thickness of the outer tempered glass of the double-glazed unit and to use reinforced modifications of Reynaers Aluminum window systems with the AP index.

Hryhoriy Didyk adds: "Yes, Reynaers has the technologies of ultra-strong windows and facades available, these are specially developed solutions for profiles and assembly details of such structures, they are tested through special independent certification bodies. In such solutions, individual brackets or a set of parts are used that allow this to be achieved, or a special metal substructure is made, to which or into which the window or facade is integrated."

The impact force of the blast wave is measured in kilopascals — kPa. Sometimes in kPa-msec, when both pressure and time are measured against a wall or window. This is called impulse loading. A load of 400 kPa-msec is destructive for structures. The impact angle is of great importance, that is, window systems on the first and last floors are affected to varying degrees.

"Reynaers has system solutions resistant to extreme explosive loads, these solutions, like the rest, are tested in special laboratories and can accept impulse loads up to 913 kPa-msec," Didyk explains.

Steel for difficult conditions

Life in specific military conditions dictates its own rules. Considering Ukraine, the market for steel systems for windows, doors and stained-glass windows will definitely grow not only in Ukraine, but also throughout the EU, Dmytro Kaladzhiev believes: "The Swiss brand Forster has increased its sales volume during its 5-year stay in the ownership of the Reynaers group of companies more than tripled and doubled the number of company personnel. The training center in the city of Arbon is waiting for Ukrainian contractors for thorough training in the processing of steel systems, so that the processors are ready for the new challenges of the post-war market."

Master class and demonstration of the possibilities of fencing structures in the Reynaers Aluminum showroom. Image source: Reynaers Aluminum

A steel profile is more expensive than an aluminum one, but in specific situations, steel is better because it has higher strength and elasticity characteristics. The steel profile is usually used in reinforced systems for banks and jewelry stores. Today, Ukrainian customers increasingly choose steel systems for private residential buildings and offices. The technology of creating window and facade systems allows you to "string", plus, combine special protective solutions, for example, ballistic protection, earthquake resistance, burglary resistance.

Hryhoriy Didyk: "Sometimes reinforced systems are used in civil construction, depending on the customer's requirements. Yes, these are solutions that have a larger price range compared to standard ones, but if the customer emphasizes the issue of maximum security, then these solutions can be offered to him.

Testing of a sample of the enclosure structure at the Reynaers Aluminum test center. Image source: Reynaers Aluminum

The Reynaers line of systems includes reinforced systems, both bulletproof and special solutions for seismically active regions. Solutions are developed at the expense of a complex combination of additional profiles, fasteners with the ability to accept seismic loads.

Bulletproof systems have several classes depending on the design and are equipped with special aluminum overlays — profiles reinforced with steel strips."

The use of an elemental glazing system individually created for the project based on ElementFacade 7 Reynaers Aluminum in the design of the facade of the office building Block 04 Unit.City, Kyiv. Image source: Reynaers Aluminum

Not just banks and headquarters

What corporate and private customers can afford, the state cannot always afford. Is it possible to use such reinforced systems in the construction of civil facilities and housing stock? Is it irrational and too expensive?

Dmytro Kaladzhiev: "We will try to simulate the specified balance in the conditions of Russia's long-term military aggression against Ukraine. Issues of protecting the life and health of residents of residential, public and office buildings, as well as issues of investments in construction, are natural. In our opinion, the use of special systems of increased strength and safety is rational where residents and workers cannot move to shelter with the onset of an air alarm: hospitals, administrative blocks of important infrastructure facilities, government and military facilities. In other cases, replacing damaged structures, even twice, will be financially more profitable than using special glazing systems."

As for new construction, it is more logical to design from the very beginning taking into account the use of advanced glazing systems

Objects built with the help of private investments will be considered flagships, which should be oriented towards the implementation of objects of national importance: airports, train stations, administrative buildings.

"New objects of increased responsibility, such as hospitals, given the extraordinary conditions of war, will most likely require unprecedented solutions. Reynaers has the experience, tools and vision to meet these challenges. Solving out-of-system tasks of bulletproof, super-strength glazing, as well as glazing with special requirements for military or government buildings, is a field of project development for which separate groups of experienced and qualified engineers work successfully at Reynaers Aluminum.

Examples of creation and implementation of unique systems can be found in Ukraine as well. In Kyiv, this is Block 04 Unit.City, towers with domes Taryan Towers. And in Mariupol, which has yet to rise from the ashes, before the war, installation of the world's first implementation of the revolutionary Reynaers MasterWall system on a building had already begun," recalls Dmytro Kaladzhiev.

Maison de la Musique – House of Music in Martinigny, Switzerland. Reynaers Forster Thermfix Light fencing systems were used in the implementation of the project. Image source: Reynaers Aluminum

Due to the fault of the aggressor, the bold engineering and architectural plan in Mariupol has not yet been implemented. Reynaers has no doubts: the innovative development of Reynaers MasterWall, as well as the most modern solutions in the field of security, will be successfully implemented during the construction of new facilities in Ukraine.