Today, POSCO Newsroom will be discussing “little” things. Have you heard of angles? They are L-shaped materials smaller than a palm but used to hold the walls of a building — the strongest L there is. The INNOVILT product to be introduced today is “Super Angle for Stone Building Construction” and POSCO Newsroom presents to you the story of a POSCO researcher who developed the product together with POSCO’s client, WOONHYUNG CO., LTD.

l Non-Visible Doesn’t Mean You Can Use Anything

I’m Kyung-Yun Yeau, a senior researcher at the POSCO Steel Solution Research Group. My task is to study the application technology of construction materials using POSCO steel. I usually handle large-scale construction materials and structural solutions, but what I’m going to talk about today is the small yet strong “angle”. Angle is used to supporting the stone material on the exterior wall of a building. In general, 1,500 to 2,000 angles are used in a five-story building, and annual domestic usage reaches over 30,000 tons.

Most large construction companies designate using STS304^* for angles since STS304 has excellent durability and corrosion resistance. However, angles aren’t exposed outside, making it difficult to check. And owing to this, some sites use imported STS200 series or STS410, which are relatively inexpensive. There are even cases where aluminum and general carbon steel are applied.

Since angles aren’t visible, is it ok to use anything? We thought no. Rather, we believe that more reliable materials should be adopted because we can’t see them. Recognizing the current situation, our research group immediately set on an R&D project of a new angle for stone building construction that applied POSCO steel. The mission was to attain both price competitiveness and safety by securing the strength while being cheaper than STS304. Another additional goal was to make the angles easily applicable on sites.

l Developing “Anchor Plus,” the Solution to Conventional Angle!

First, 293 patents for stone building construction angles in Korea, Japan, the U.S., and Europe were analyzed to grasp the conventional angle technology. As a result, we concluded that coming up with simple construction technology and implementing optimized structural performance was as important as securing price competitiveness. For this reason, the “anchor tightening method” was chosen. In this method, the angle is placed between the wall and the stone, and it fixes the stone material with its angle, control plate, plug tip, and bolts. Since it is installed with some distance between the wall and the stone material apart, there is no whitening, which causes white spots due to the inflow of rainwater. It also shortens the construction period while being relatively light.

However, the anchor tightening method also had some areas for improvement. First, since the angle is constructed without considering the concrete condition of the wall, the anchor bolt support may or may not be sufficient. Even if the anchor bolt support is satisfied when installed in solid concrete, it may be reduced due to unexpected wall cracking. Also, if weight is applied to the angle constantly, a creep may occur, which means that the material will continue to deform over time. The resulting angle bending and cracks in the stone material are also chronic issues.

However, there were other tasks to be solved as well. We had to point out cases where plug tips (locking pins on the outer wall stone) were intentionally omitted. The plug tip is a pin that fixes the angle and the exterior stone and is often omitted mainly because of two reasons: 1) it is constructed at a period in construction when management is insufficient, and 2) it is hard to check once it is installed. Another problem was that in fixing, there were cases where only epoxy was used and not a proper plug tip. Resolving these issues was also our job.

We decided to start with solving the bending caused by creep deformation. First of all, I thought of using high-strength steel that could reduce the weight of the anchor while securing the overall strength. And POSCO Super Ductile Duplex (PossSD), a corrosion-resistant high-strength duplex stainless steel completed with POSCO’s new technology crossed my mind. PossSD has high strength, excellent workability, and corrosion resistance. Hence, it can be applied to a wide range, such as architectural exterior materials, railway train parts, tableware, pipes, and evacuation ladders.

What if we applied PossSD and added structural reinforcement? While the conventional angle is bent only once in an L shape, our product was made stronger by adding bent wings on both sides of the material. With this improvement, the previously 5mm to 8mm thick angle made with conventional STS304 could be thinned to 3mm, while enhancing the resistance to creep at the same time.

After two years of R&D, the new angle for stone building construction obtained a patent under the brand name of “Anchor Plus” in 2017. Compared to conventional angle for stone building construction, the thickness was reduced by more than 40%, securing economic efficiency. Also, having been verified by a structural engineer for generated stress, working stress, generated bending, and permitted bending, the new material satisfies all conditions and can be put to use immediately at the sites.

l Anchor Plus, Not the End

There was one more task to be solved before the full-scale application of the newly developed product. Finding a manufacturer to help develop the demand for Anchor Plus. At the time, Woonhyung Co., Ltd., a manufacturer specializing in stainless steel angle, caught our eyes. Woonhyung Co., Ltd. supplied angles made of STS304 to Samsung C&T Bok-Sik Jang, CEO of Woonhyung, also recognized the potential of the angle for stone building construction, a combination of new materials and design improvements, and decided to cooperate with us. So, as a result of the joint marketing efforts of the two companies, more than 120,000 Anchor Plus products were applied to the site of “The Sharp Central City,” a multi-purpose complex consisting of 2,610 apartment units and 238 studios, in Songdo.

▲ Actual application of Anchor Plus

Anchor Plus was sold in large quantities, showing its excellence even in the conservative construction market. However, a problem occurred out of sudden. In 2018, the process line producing PossSD was decided to be closed, and so there would no longer be material to make Anchor Plus. As PossSD had shown high strength and corrosion resistance at a reasonable cost in Anchor Plus, we seemed to be in great trouble. Will Anchor Plus be discontinued? We couldn’t let that happen! We set out to find a substitute for PossSD.

l POSCO World Top Premium, PossHN0 to the Rescue!

When all hope seemed to be lost, POSCO World Top Premium (WTP) steel POSCO stainless High Nitrogen 0 (PossHN0) came to the rescue. PossHN0 is a new stainless steel product that is economical and stronger with reduced nickel content and increased nitrogen content than conventional stainless steel products. When I asked about the product to other co-workers, they said that its durability was comparable to STS304, meaning it could replace PossSD!

We started the structural review again, this time with PossHN0. Unfortunately, however, we concluded that it wasn’t enough to apply in angles compared to conventional PossSD. However, we couldn’t stop here. I decided to reinforce the strength through structural change. The idea was to apply an embossing rail to disperse the load!

Embossing rails are protruding railings that stand out. The problem in the conventional angles was that the load was concentrated on the curved part of the angle. To solve this issue, we attached an embossing rail to our product to disperse the load weight, as seen in the picture above. By applying the embossing rail, the angle could withstand heavier weights. Also, since the control plate and the angle are held tight, the overall work became more convenient, and the connection also became stronger than before.

Thanks to the embossing rail, the angle itself could secure enough strength, so the wing parts on both sides that were attached to prevent creep deformation in the conventional PossSD angle could be eliminated. Also, to solve the previously mentioned problem of plug tips, the plug tips were painted and added to the control plate as a whole so that there wouldn’t be any loss in the first place.

R&D can only be complete after performance verification. In other words, we had to check whether the PossHN0 angle is superior in price competitiveness as well as performance compared to the conventional STS304 angle! We conducted testing to measure the load by attaching actual stone panels to the conventional and newly developed products. As a result, the STS304 angle for stone building construction could withstand up to 22kg, while PossHN0 showed an outstanding performance of bearing up to 35kg.

It shows that even though the PossHN0 angle is lighter than the conventional STS304, it proved to demonstrate better performance. And this was confirmed again through a test report issued from the Korea Testing & Research Institute (KTR) and a structural review by the Structural Technology Office. Following these verification results, the new angle for stone building construction was released into the market in 2019.

l Small But Great, INNOVILT Super Angle for Stone Building Construction

With the birth of the new angle, Woonhyung spurred marketing activities, and POSCO also showed full support for our client. As a result, the angle was applied to multiple large-scale construction sites, including Samsung apartments, Daewoo apartments, and POSCO E&C apartments. And in 2019, it was finally selected as an outstanding product by the Korea Land & Housing Corporation, laying the foundation for its expansion in the future. It also received KS certification. In October 2020, the product was certified in the 4th batch of INNOVILT products under certification under the product name “Super Angle for stone building construction”.

Some features of the INNOVILT Super Angle found on site were delivered to us. First, the workers who have used this product were surprised by the workability. The PossHN0 angle is 3.2mm thick, 36% thinner than the 5mm of conventional STS304. As the thickness decreased, the weight became lighter as well. Also, since the control plate moves only back and forth along the rail, there is no extra work needed to be done to straighten the product in case of side swinging. This was one of the reasons that actual workers regarded this product as convenient.

There is another reason why INNOVILT angles were chosen. And that is because of its economic feasibility. The INNOVILT angle adopts high-strength steel so it can withstand at least the same or more weight than the conventional angle though being much thinner. Naturally, material cost can be reduced by a whopping 15%. The fact that PossHN0 contains less nickel, a relatively pricey material, compared to STS304 also contributed to its economic advantage.

But the bottom line is this — no matter how convenient and economical the angle is, it can’t be used if its safety is not guaranteed. The INNOVILT angle plays its role in full in that regard. It even further ensures safety since the plug tip is integrated into the control plate so that it is possible to check whether the plug tip is installed during site supervision.

The INNOVILT product to be introduced today is “POSCO Lightweight Soundproof Tunnel (PosLST)”. POSCO Newsroom presents to you the story of a POSCO researcher who developed the product together with POSCO’s clients, Tech Square and Yujin Steel Industry Co., Ltd.

l A Solution to Traffic Noise: Soundproof Tunnel!

It has become a challenge to enjoy calmness in the city, even up the mountain, since the traffic noise from far away is heard so well. The same also goes to labs where the windows are tightly closed. The loud sounds of horning and the engine of heavy trucks are more than enough to disturb work.

Before some explanation, let me introduce myself. I am Myung-Hyun Roh, a Senior Researcher at POSCO Steel Structure Research Group. And the reason my ears are so sensitive to traffic noise is that I am currently researching new soundproof tunnels that reduce noise.

Complaints for road traffic noise received by the Anti-Corruption & Civil Rights Commission over the past three years have steadily increased — 39,326 in 2017, 63,011 in 2018, and 113,073 in 2019. And about 98% of these complaints are from residents living near the roads. Residents complain that the inconvenience caused by noise is so great that it is difficult to live with the windows open.

But getting rid of all cars on the road can’t be a solution. And because of this, soundproof walls were built in various places. However, these walls couldn’t be the fundamental solution and turned out to be dissatisfactory, since they didn’t reduce noise significantly in high-rise buildings, reflected sunlight causing the indoor temperature to rise, and harmed the view of the residents on lower floors of the apartment buildings.

With these matters, the “soundproof tunnel” emerged as an alternative to such soundproof walls. And this is what we will be discussing today. Since the soundproof tunnel directly blocks the generated noise from reaching high, the soundproofing effect is excellent for high-rise buildings. Also, since it minimizes reflected noise, previously found in the case of conventional soundproof walls, the soundproof tunnel has received the spotlight as a representative technology that can be effective in reducing traffic noise on urban roads.

▲ Soundproof tunnel installed in the downtown area

However, the soundproof tunnel has many factors for improvement as it has not been sufficiently reviewed in various aspects, including safety, usability, economic feasibility, and aesthetics. There isn’t any standardized design method, so the design is made uniformly, in simple forms that do not harmonize with the surroundings. In complex urban areas, soundproof tunnels must be installed on existing structures such as bridges and overpasses. In this case, the excessive weight and additional loads caused by wind could exceed the design load, which becomes a critical problem.

This is the reason why our Steel Structure Research Group started to develop soundproof tunnels. With optimal design from POSCO steel to lighten the structure and objective performance evaluation, we thought of developing a reliable soundproof tunnel product and construction method, which could eventually help reduce traffic noise drastically. Since POSCO already has high-strength premium steel products, there was no reason not to do so. That’s how the R&D for new soundproof tunnels began.

l Our Best Partners in the Making

An outstanding R&D is accomplished through collaboration. So for the project, a client company with expertise in the field joined as a partner to support R&D. The company is none other than Tech Square Co., Ltd., which has excellent experience and capability and also holds a patent in the field of lightweight soundproof tunnels. In 2013, Tech Square proposed a “truss roof-type soundproof tunnel construction method,” which featured several steel pipes arranged in a triangular shape instead of H-shaped steel, the structural material of conventional soundproof tunnels.

The uniform frame structure of the H-shaped steel method caused excessive bending in soundproof tunnels when installed on wide roads. Increasing the size of the H-shaped steel could help solve the bending. However, this increased the product weight, which led to a rise in construction cost. Tech Square’s idea was to secure lightweight, economic feasibility, and safety with a truss structure using high-strength steel pipes instead of H-shaped steel. Since POSCO does not produce section steel, the idea of replacing them with steel pipes sounded promising.

Along with Tech Square, there was another client partner who joined the project — Yujin Steel Industry Co., Ltd., a specialized manufacturer of steel pipe. To replace H-shaped steel with steel pipes, it was necessary to find a company that could process high-strength steel plates into steel pipes. And Yujin Steel Industry, which had abundant experience in manufacturing pipes, decided to take over this role. Now that the dream team was complete, we could set on operation! Our goal was to reduce weight and costs compared to the conventional H-shaped steel method. And, in January 2014, we finally started full-scale R&D.

l The Journey to Develop a Light & Strong Soundproof Tunnel

There is one certain feature that a soundproof tunnel must meet: excellent noise reduction performance. For this, soundproofing panels are installed within soundproof tunnels, and they can be divided into “Sound-absorbing Panels (opaque),” which absorbs noise, and “Reflecting Panels (transparent or opaque),” which reflect the path of the noise. Most soundproof tunnels have opaque sound-absorbing panels installed on the side, and since noise is loud at their entrance and exit, the soundproof tunnel extends beyond the required section, or additional soundproof walls are installed at the entrance and exit. However, this causes other issues regarding cost and aesthetics. How can POSCO’s technology resolve these issues?

We decided to install sound-absorbing panels inside the steel pipe truss on the roof of the tunnel. The opaque sound-absorbing panels, which were originally installed to the sides, were put into the truss of the roof, and it was expected to help drivers secure their field of vision as well as to improve aesthetics. To verify the function of the sound-absorbing panels, we analyzed the result of a program dedicated to noise analysis. And the tunnel we designed was evaluated to reduce noise by an average of 1.0 dB due to the sound-absorbing panels inserted inside the steel pipe.

The second feature for the soundproof tunnel that we aimed for was that it should be light. As explained above, since the soundproof tunnel acts as an additional fixed load on existing structures, secure structural safety becomes challenging if it is heavy. Also, since soundproof tunnels must be constructed on roads that are being used, it is important to construct them quickly compared to other structures because longer road construction causes great inconvenience to users. So as a solution for this, we adopted POSCO high strength steel SHT460 (Structural High Strength Tube 460, a hot-rolled coil of tensile strength 590 MPa Grade) and PosH690 (POSCO High strength 690, a hot-rolled coil of tensile strength 690 MPa Grade) as the material for steel pipes.

he last feature is that the structure must be strong. This is because a soundproof tunnel has to withstand an external force, such as snow and rain, as well as the weight of the soundproof tunnel frame and the soundproof panels. Taking this into consideration in the design process, the safety of the structure was confirmed through various experiments. One of the experiments was the “load experiment”. We made a test specimen to see how many times the design load it can withstand. As a result, it could endure “wind load” up to three times the design load, and in the case of the “snow load,” more than five times the design load could be endured.

Focusing on the three features mentioned above, experiments and verification were repeated for 17 months of research. We obtained results showing the new product to be superior to conventional tunnels in all areas of noise reduction, weight reduction, and structural safety. Finally, we completed the new lightweight soundproof tunnel technology using POSCO materials. The new product was named POSCO Lightweight Soundproof Tunnel (PosLST)!

l Mission: Obtain New Excellent Technology!

Our mission didn’t end with just technology development. Once, a technician at a client company mentioned that outstanding technology objectively verified will someday show its value even if it does not employ expedient marketing. At the moment, I thought that it would be nice if the technology we developed could receive objective certification. So we embarked on a new task: Getting the New Excellent Technology^* certification!

Looking back, the task was quite challenging. It was not because of the low certification rate or the high level of judging, but because the effort and time spent on the entire NET screening process, from applying to being certified and notified, is never easy. We devoted ourselves nine months to the NET process, including on-site application and quality verification. And finally, on September 12, 2016, PosLST was proudly designated as New Excellent Technology No. 795 (Tunnel-type soundproof facility using truss pipes with transverse and detachable side soundproof panels and lateral sound-absorbing panels) from the Ministry of Land, Infrastructure, and Transport. It was the first soundproof tunnel construction technology in Korea to receive official verification.

The conservative industrial atmosphere makes the initial acceptance of new construction methods and products rather difficult. So, at first, I was worried that the market response would be insignificant.

Fortunately, such anxiety was nothing more than an overwhelming concern. In 2017, it was initially applied to the soundproof tunnel construction of the 2nd Gyeongin Anyang-Seongnam Private Expressway. Since then, it has also been applied to nine other projects, including the North Road Soundproof Tunnel in Wirye City and the Yongin Urban Planning Road Construction. And the PosLST Lightweight Soundproof Tunnel construction technology has been recognized for its excellence.

▲ A soundproof tunnel that applied the new steel pipe truss type construction method on the Anyang-Seongnam Expressway

l PosLST: Lightweight, Economical, and Aesthetic

So, what are the advantages of PosLST evaluated in the field?

The first advantage of PosLST is, of course, noise reduction. The sound-absorbing panels installed in the steel pipe truss on the roof of the soundproof tunnel are excellent in reducing the noise generated at the entrance and exit of the tunnel. Also, by placing the opaque sound-absorbing panels, originally installed on the sidewall of the tunnel, on the tunnel roof, the visibility of drivers has improved along with better lighting.

The next advantage would be the tunnel’s lightweight. Since PosLST tunnel is made of POSCO’s high-strength steel products, SHT460 and PosH690, it minimizes the overall pressure on the structure. Compared to conventional H-shaped steel adopted soundproof tunnel frames, the weight can be reduced by about 53%, satisfying the design load and achieving both lightweight and economic feasibility. Besides, the truss structure is effective in preventing bending by improving the structural strongness of the tunnel.

The third advantage is excellent constructability and economic feasibility. As mentioned earlier, in PosLST soundproof tunnels, the sound-absorbing panels, which are key functional material, are inserted into the steel pipe truss on the roof side. So, for the side of the tunnels, transparent boards can be installed instead of the opaque sound-absorbing panels. Also, it is manufactured in a detachable manner, so in case of damages, those parts can be partially replaced. In conventional soundproof tunnels, replacing the side sound-absorbing panel is difficult. Thus, maintenance costs are high. Previously, since the soundproof panels on the roof were installed on H-shaped steel, it was necessary to install a separate frame to support four sides but, with PosLST, the panels are installed on a round steel pipe, so you don’t need a frame — you only need to fasten bolts using angles! Thanks to this, if the optimal design is based on POSCO high-performance steel, construction costs can be reduced by about 15% compared to the existing construction technology, and maintenance costs required for replacing damaged sound-absorbing panels can be reduced by 31%.

Another thing that cannot be left out is “aesthetics”. The design of PosLST is superior compared to conventional tunnels since it applies artistic circular steel pipes. A variety of atypical structures can be implemented, enabling harmonious designs that are fit for the urban landscape.

The industry is also showing favorable responses to PosLST. Officials of the construction company in charge of the production and installation of soundproof tunnels say, “Since the material is made of POSCO steel, PosLST is lighter and requires fewer bolting parts. So the construction period is shortened, and the process is easier than when using conventional materials. Once installation is complete, it also boasts outstanding aesthetics features, so POSCO’s new technology is expected to spread widely in the future.”

The INNOVILT product to be introduced today is “UL700 Steel-Aluminum Hybrid Jack Support”. POSCO Newsroom presents to you the story of a POSCO researcher who developed the product together with POSCO’s client, Daehan Scaffolding.

l Temporary Materials? Safety Materials!

I am Tae-Hyu Ha, a senior researcher at POSCO Steel Structure Research Group. I am working on developing construction materials using POSCO steel, and today I am going to tell you the development story of “temporary materials“.

Let’s picture the construction of a building. Laying down the base work, building a framework, installing floors and ceilings, applying interior and exterior materials, and decorating the interior — these might probably be the construction processes that come to mind. However, there is one crucial process missing here. It is none other than “temporary work”.

Temporary work is the phase where temporary and basic structures necessary for construction are installed. It includes bringing in electricity for the construction tools, installing water facilities for drinking and sanitizing, and establishing safety facilities to prevent accidents. And “temporary materials” are essential in this temporary work. Temporary materials include walk plates and passages installed to enable work at high areas, supports that temporarily hold the building framework, and a double-deck that allows vehicles and pedestrians to walk above the construction section. Put differently, proceeding with construction is impossible without temporary materials.

Temporary materials are especially important in that they directly affect the quality of construction and the safety of workers on site. However, in most cases, they aren’t paid much attention because they are demolished once the construction is complete. Since temporary materials are perceived to be materials that are used for a short time anyway, many try to shorten the construction period by setting them up quickly and reduce costs by utilizing cheap materials imported from overseas.

▲ High-strength system scaffolding installed on sites

In this situation, POSCO set to pioneer the temporary material market using premium steel materials with its clients from 2009 as a measure to secure the safety of construction sites. The goal was to bring about a change in perception that temporary materials are not just temporary but are safety-related materials that are directly connected to the safety of workers. As a result, POSCO developed the premium steel tube “UL700 (Ultra Light 700)” for “scaffolding”. POSCO’s high-strength steel PosH690 was applied as the material for UL700.

What is scaffolding? Well, when passing a remodeling site or a construction site, you might have seen a structure where narrow steel pipes are woven together vertically and horizontally as if they were wrapping the building. This is called scaffolding, and it is a kind of a walk plate that enables workers to safely climb up and down in the construction of high-rise buildings. Scaffolding made with UL700 adopts POSCO premium steel and has a tensile strength of 700 MPa, replacing conventional scaffolding that mainly uses general steel pipe of 400 MPa tensile strength.

In the beginning, expanding high-strength premium products in the price-oriented steel pipe market was not easy. However, after receiving positive feedback from construction sites and being recognized for its economic feasibility and safety, demands for the products began to expand gradually.

l Making the Temporary Column “Jack Support” as Premium

As recognition for UL700 with its safety and high strength performance grew, product inquiries rushed in not only about scaffolding but about various other temporary materials. Then one day in February 2016, Min-Young Jeong, CEO of Daehan Scaffolding, visited the POSCO R&D Center in Songdo and shared his story with us.

“We are a company that manufactures and supplies a product called Jack Support. Jack Support is used to distribute the load of the upper part of a building. When concrete is poured on the floor, its strength increases as the concrete hardens, but it usually takes more than a week for the concrete strength to become sufficient. So, to proceed with construction on the upper floor, temporary support must be installed under the floor plate while the concrete is hardening and the temporary support used here is Jack Support.”

▲ Jack Support applied on construction sites

He went on, “However, we have a problem. For places with high ceilings, such as the lobby and public space on the first floor, a Jack Support of at least 5m is required, but the problem is that as the product length increases, the weight increases as well. Manufacturing and supplying aren’t a problem but installing a product weighing over 100kg is a definite issue. Imagine that workers have to lift, move, and install a material that weighs over 100kg. So, that’s why we need to develop a Jack Support that is light yet long enough. I heard that there is a steel pipe for scaffolding called UL700, and I wondered what if we apply such high-strength steel to Jack Support as well.”

Jeong’s suggestion was plausible, but I was not too sure. I could not help but think, “Oh, length issues. Again”. It was because I knew from my experience that when high-strength steel is applied to a long material, the performance does not come out properly due to “buckling”. Buckling is a phenomenon where a material, which has a long length compared to its cross-section, suddenly bends when the load is applied above the limit it can hold up. In the case of short types, high-strength steel can withstand much heavier loads without bending, but with the length increasing, even high-strength steel bends under similar loads as ordinary steels due to this buckling effect.

I said, “CEO Jeong, Since buckling occurs in long materials, it is highly likely that the results might be indifferent even in the case of high-strength steel. So, let’s design products by length using high-strength steel first, and then conduct performance tests with the prototypes. Detailed directions can be discussed later.”

First, as CEO Jeong suggested, I set on designing a standard-type Jack Support (with a height of 3 to 4m) and a high ceiling-type Jack Support (6 to 10m). The idea was to make four prototypes, two for each type — one with normal steel SS40 and the other with high-strength steel PosH690 — and check the maximum load each product can support. The design details were sent to Daehan Scaffolding and they were produced accordingly. Two months later, we met again at the Songdo R&D Center to evaluate the performance. After inspecting the completed prototype, we carefully started the testing. The results turned out as expected. The standard-type Jack Support adopting high-strength steel exhibited similar performance to conventional products while reducing the overall weight. However, in the case of the high ceiling-type Jack Support, both the high-strength prototype and the normal prototype didn’t meet the required performance, which is a maximum load of 30 tons.

Things didn’t work out as CEO Jeong had expected, and it was a little disappointing for us as well. We couldn’t attain the desired results, but we couldn’t stop there. We carefully made a new proposal.

“Developing a high ceiling-type Jack Support is difficult right now. How about applying high-strength steel to the standard-type Jack Support instead? As you could see in the testing, if high-strength steel is applied on the standard-type Jack Support, the product weight can be drastically reduced. It could enhance the price competitiveness of the product as well.” CEO Jeong considered our offer for a while and replied, “The product is widely applied, and the market is much larger, so it would be worth a shot. Let’s do it!” After that, we set on several detailed design and performance tests, and we finally launched a high-strength Jack Support with a maximum length of 3.8m.

It wasn’t a product of the initial plan, but the response from the market was hot! The secret was its lightweight, which is about half the weight of conventional products. It was an opportunity to capture the need for lightweight Jack Supports in the market. In construction sites, time and labor force are important, so the demand for high-strength lightweight products gradually increased, and the client company producing and supplying these products became busier than ever.

l Steel & Aluminum Together! The Advent of a Hybrid Jack Support

In November 2018, almost three years later, Daehan Scaffolding CEO Min-Young Jeong contacted us for another visit to the research center. Since the commercialization of the high-strength Jack Support, we hadn’t received any direct communication, so CEO Jeong’s contact was quite a surprise. Was there any problem? The story of CEO Jeong was as follows.

“Currently, our product is the lightest among domestic steel Jack Support products. The market has also expanded. But recently, more and more companies are making Jack Supports with aluminum. Aluminum is supposed to be expensive, but the price of these products aren’t very different from our products as well. So, I would like to take a chance to upgrade our products once again.”

There were two things that Daehan Scaffolding desired. The first was expanding the maximum length of use from 3.8m to 5m. CEO Jeong explained that the length of the product had to be increased than the present to respond to various demands on the field. The second was extending the range of length adjustment. The adjustment range of current products is only 30cm, and so to meet the length requirements of each construction site, the products have to be manufactured accordingly, resulting in over 10 different types of products, which is too many. CEO Jeong wanted to extend the adjustment range to 70cm with a single product that could be applied to more sites.

Listening to him, I realized that it was similar to what we had worked on three years ago. As I was going to say, “Let’s try a new method since it’s difficult to do that with high-strength steel.” CEO Jeong proposed an idea, “We designed a product where the length can be adjusted by inserting an aluminum inner tube into a UL700 steel pipe.”

Combining aluminum and steel? At first, it sounded like a non-realistic plan. I thought, ‘This product can be made with steel alone. Why should we apply aluminum here?’ But my thoughts soon changed as I saw the prototype sample. Since the aluminum inner tube allows precise machinability, it became easy to secure the straightness of the product, and the strength of the product was also steady thanks to the application of high-strength steel. Making the outer tube, which must withstand the load, with high-strength steel, while making the inner tube for length adjustment with aluminum to reduce the overall weight — it seemed like a workable idea.

We decided to come up with an optimal design based on the client’s prototype. First, we worked on finding the coefficient for the complex aluminum section design. Next, we calculated the buckling load of the steel pipe by length and improved the thickness of the steel pipe and the shape of the aluminum section accordingly.

Four types of test specimens were produced by different lengths, and load testing was conducted for each. The commercial product lineup was also complete taking into account the test results and the most required height at construction sites. Considering the buckling strength and field workability of the inner tube, the length of the aluminum inner tube was set to 1m, and it was produced in four different sizes. After a year of research and testing, we finally launched a high-strength hybrid Jack Support with aluminum inner tube in July 2019. It was such an achievement in 4 years since the first meeting with Daehan Scaffolding in 2016.

l Safety for Workers, Economics for Contractors

The collaboration of steel and aluminum — the two different competing materials — was embodied into this Hybrid Jack Support. And within a year of its introduction to the market, it has been applied to more than 30 apartment construction sites of leading domestic construction companies, such as Hyundai E&C, Daewoo E&C, and POSCO E&C.

▲ The UL700-Al Hybrid Jack Support applied on site

CEO Jeong said, “The product is really good because it’s light — this is what I hear a lot when supplying the products.” We started with the application of high-strength steel to temporary construction materials, which led to the development of ultra-lightweight, high-strength Jack Supports, and, finally, here we were with Hybrid Jack Supports.

Compared to the conventional 5-inch product, the Hybrid Jack Support has the same strength but is 50% lighter. It also weighs about 80% of an aluminum product. Since UL700 is high strength steel, it is possible to reduce the outer cross-sectional area to one-third of that of aluminum, which results in remarkable weight reduction. Supposing that the conventional Jack Support is 60kg, an aluminum product is 35kg and the Hybrid product is merely 29kg. Other than the fact that it can be handled more safely by the workers, what meanings do this ‘lightweight’ feature have on sites?

The most crucial fact is that it can be installed quickly due to its weight reduction. 29kg is a weight that a single worker can easily handle. Also, unlike conventional products, the length can be adjusted up to 70cm without bolts, so it allows quick and convenient work.See how a worker installs a Hybrid Jack Support on site in just 35 seconds!

The simple and quick installation enables a reduction in labor costs and shortens the construction period. In fact, there was a case where labor costs were reduced by more than 30% as the time required to install and disassemble products was shortened. Also, since a more number of products can be loaded on the trucks to carry them, transportation costs are reduced by about 30%.

However, there may be doubts like, “Wouldn’t there be a problem with durability if it becomes so light?” There might be concerns about the inner tube made of aluminum being damaged on sites. But the product we aimed to manufacture was a ‘light yet strong temporary material’ — not just a light one. Unlike conventional products, the Hybrid Jack Support is designed to be separated by parts, so there is less risk of damage, and even if it is damaged, the damaged part can easily be replaced, so the maintenance cost is also low. The exterior of the Hybrid Jack Support is made of POSCO UL700, which makes it much more durable.

Four years have passed since developing Jack Supports using high-strength steel and improving them to meet the needs of the market. The market looks stagnant, but its trend is changing fast. That’s why we can’t just sit still in the lab and make an experiment to develop products.

In that sense, the Hybrid Jack Support is the result of POSCO and its client going back and forth between the lab and the field, constantly thinking about ideas to overcome the weaknesses of the product. In the second quarter of this year, it was listed as one of the INNOVILT certified products as well.

The temporary materials market is a place with unclear quality standards and a high temptation of low-cost goods. However, it is our mission to change this perception and eliminate the blind spots for the safety of workers with our products and technologies. At the same time, we should create solutions that can bring substantial benefits to the constructors as well. This is the reason why, even today, INNOVILT Lab is busy developing new solutions.

POSCO Newsroom presents the story of premium construction material, INNOVILT, and today we will start with SP-CIP Pile(Smart(Steel) Pipe-Cast In Placed Pile)! Let’s take a peek at the note of POSCO’s researchers who developed the Steel pipe Pile together with clients — MS Pipe and Hankook Material.

l Bid Farewell to Heavy Rebar!

I am Dong-Wook Ahn, a senior researcher at POSCO Steel Structure Research Group. The field that I am interested in these days is ‘rebar’. You might wonder what rebar has got to do with POSCO since POSCO doesn’t manufacture rebar. Of course, I’m not talking about developing rebar. My goal is to develop a steel pipe that can replace rebar and make a premium construction material.

Rebar is the most commonly used material on construction sites. However, it has a major drawback: it is too heavy. Also, connecting the rebars by welding is impossible, so they should be tied together with wire, one by one making the rebar processing work highly dependent on manpower. Hence, the heavyweight of rebar causes great inconvenience to the workers at the site, and it is one of the main reasons why many construction workers suffer from musculoskeletal diseases.

All creation starts with a critical mind. The question of “Should it always have to be such heavy rebars?” led to the next question, “How about making a lighter yet stronger alternative to rebar?” How was this possible? With our very best steel technology! I soon started developing a lightweight steel pipe to replace rebar. With this lightweight steel pipe, my final goal was developing the construction material, ‘Steel Pipe-Cast In Placed Pile’.

A net pile made of rebar is commonly used for ground stabilization. It prevents cracks and degradation of the building. What if the rebar was replaced with steel pipes? It will become lighter and stronger, therefore, resolving the many problems mentioned earlier.

l Developing a High-Strength Steel Pipe with a Yield Strength of 800MPa!

The yield strength (YS) of rebars in the market is 400 MPa. This means that if a force of 400 MPa or more is applied to the rebar, it will deform and will not be restored. My task was to come up with a steel pipe that was at least equal or stronger compared to rebars. Considering that steel pipes are hollow in the middle, I decided to create steel pipes with a yield strength of 800MPa.

My team began research on POSCO’s high-strength steel, PosH690 (POSCO High strength 690). We made a steel pipe with this PosH690 at ‘MS Pipe’, our client company, to analyze yield strength caused by work hardening. Finally, we succeeded in deriving optimal production conditions.

With the steel pipe from MS Pipe, ‘Hankook Material’ produced the Steel Pile. (Hankook is another client company of POSCO.) The main rebar was replaced with a steel pipe, while the spiral rebar was used as it was, along with the wires used for tightening. Everything remained the same except for the main material. Test specimens — one where conventional rebar net pile was placed inside the concrete and the other Steel pipe pile inside the concrete — were made, and experiments were conducted to compare performances over and over again. The result turned out to be a huge success. The newly developed Steel pipe Pile showed similar performance to the rebar net pile. Finally, a Steel pipe Pile product using a steel pipe was all set!

▲ Testing of the flexural strength of piles

l Introducing the INNOVILT Steel Pipe-Cast In Placed Pile!

Hankook Material named the product Smart(Steel) Pipe-Cast In Placed Pile. The manufacturing process is a collaboration, and it is as follows: POSCO supplies PosH690 and MS Pipe produces steel pipes with it, and Hankook Material manufactures SP-CIP piles with the pipes.

Construction materials, especially those for ground construction, must be applied to the actual construction site and made sure that it is indeed as strong as the extracted research value. This means that research on construction materials does not end in the lab. Employees of MS Pipe, Hankook Material, and I carefully watched the construction process on site. It was also necessary to verify whether the product guarantees the desired performance after the construction was completed. After waiting for the concrete to harden for about a month, a dynamic load testing was conducted by striking a 10-ton hammer on the structure to measure the support force. A horizontal load testing was also carried out by pushing the structures away from each other to check seismic performance. Fortunately, both tests turned out to be satisfactory. The SP-CIP Pile went under two more on-site tests eventually proving that the product was indeed lighter, economical, and yet stable in strength compared to the use of conventional rebar pile.

l SP-CIP Pile with 100% POSCO Steel!

The weight of the product was dramatically reduced as intended, but there was one more task to be resolved — welding. As mentioned earlier, rebars cannot be welded because they do not secure chemical components. The steel pipe pile that we developed was woven with wire as well instead of welding. So we decided to go a step further and upgrade the product into a fully welded one. “Let’s make a steel pipe pile that can be welded with 100% POSCO steel!”

We considered using a steel wire rod that has two or more rows of bumps arranged on its surface, resembling the shape of rebar. Since the steel wire rod had already been qualified for the KS standard (KS D 3552), replacing spiral rebar with it became possible. Next, Hankook Material conducted welding tests on three types of products: 1) rebar & rebar, 2) steel pipe & rebar, and 3) steel pipe & steel wire. The results showed that the ‘steel pipe & steel wire’ product was the only one that could be welded with high quality.

We also acquired an official use certification from the Korean Construction Joints Association based on this test result. What started with the development of steel pipes to replace rebars eventually ended with producing Steel pipe Piles using 100% POSCO steel. It was an achievement that had taken four years.

▲ The automated welding facility of SP-CIP Pile at Hankook Material

l The Birth of SIP Pile: 3 Features in 1

In January, following joint marketing by POSCO and the client company, the product was finally applied to a construction site in Seoul for the first time. In the following six months, four additional sites adopted the product as well, and it succeeded in settling into the construction market. The response to the SP-CIP Pile is quite phenomenal, considering the conservative nature of the construction market. Here are some of the features that those who have used the SP-CIP Pile mention.

First of all, it is economical. Since the yield strength of the steel pipe is twice as high as conventional rebar, the sectional area required is reduced by half. Despite the unit price per ton being more expensive than that of rebar, the weight per meter is reduced by half, hence, the unit price per meter is also more economical than that of rebar.

Second, it is of stable quality. In the case of conventional rebar net piles, binding wires are used to bond the materials since welding is impossible. However, in the case of our products, they can be safely welded and supplied. Let’s skip the obvious explanation of which product is more stable.

Another feature is lightweight. It significantly reduces the labor intensity of workers on site. In fact, there was even a case that workers, who worked with steel pipes at the previous site, suggested changing the rebar to steel pipes at the new construction site.

One more thing. It is supplied through pre-production. SP-CIP Pile can be manufactured on site as well, but it is mostly pre-produced at factories and sent to the construction site.

In-Jeong Woo who was in charge of a construction site where SP-CIP Pile was applied said, “Since SP-CIP Pile is pre-produced in factories with excellent quality and only needs to be placed on site, it is especially convenient to handle in small-sized construction sites of downtown areas. The product is brought to the site in a complete form, so there isn’t any problem of handling the remaining rebars.” He also added, “Wire-connected rebar net pile is distorted when moved or placed for construction, but since Steel pipe Pile is produced by welding, the construction process becomes much safer.”

Hankook Material’s SP-CIP Pile was selected as an INNOVILT certified product in 1Q this year, and since then, it has been more actively applied at sites. Researchers at POSCO, including myself, are still working on technologies to expand the market. Our work will continue until the day comes where the steel technology required by clients is successfully realized into innovative products.

For outstanding products to be widely used in the market, branding and marketing are essential. However, there is something that needs to be done first — developing the product! This is why POSCO embarks on the mission together with its client companies from the very beginning, ‘developing INNOVILT products.’

l From a Sketch on a Tissue to a New Foundation for Groundworks

On a winter day in 2017, Jong-Beom Lee, CEO of Dokun Entech, POSCO’s Jung-Hae Lee, and Dong-Wook Ahn, were talking at a coffee shop after a meeting. Dokun Entech is POSCO’s client company and specializes in substructure and ground stabilization. To create an underground space when constructing a building, it is important to dig up and make sure the ground does not collapse. The material that prevents soil on both sides of the site from collapsing is called a ‘sheathing’. The most frequently used sheathing is a small size Rolled H (RH) section steel, which looks like H-shaped steel laid sideways.

Since POSCO does not manufacture section steel, it developed Built-up H (BH) section steel made by welding steel plates instead, enabling its clients to advance into the section steel market. In the case of Dukun Entech, it was necessary to develop BH section steel optimized for groundworks. The talk at the coffee shop was also about the development of this product, and this was when a new idea struck Dong-Wook Ahn.

“It doesn’t have to be H-shaped steel, does it? Since we make products by welding, what if we add another web?

Instead of H-shaped steel, it’s going to be ㅍ-shaped steel!

It will be stronger and more efficient since it can be made lighter yet with better performance.”

They set to work immediately, sketching the idea in detail on a tissue paper. Transforming the conventional H-shaped steel into a new ㅍ-shape seemed possible. They went straight back to their offices and labs to design this new product. High-strength steel was applied, therefore, increasing the strength of the product by more than 50 percent yet making it lighter by 20 percent. To realize it into an actual product, POSCO’s Jung-Hae Lee utilized all of his connections to find the best manufacturer. It took three months for him to find a fine manufacturer, and this was how POSCO, Dokun Entech, and Dongyang E&C came together to produce ㅍ-shaped steel. It was the first time to manufacture high-strength ㅍ-shaped steel for sheathing. The product was named Double I Beam (DIB), considering that it has two webs.

▲ A modeling image of DIB (left) and the actual product on site

Development and verification continued for about a year before the product made its debut on site. In January 2019, initial supplies were sent off to the construction site of a supermarket in Hanam, Gyeonggi Province. It was a moment when the idea sketched on a small piece of tissue became real. The response on-site was immediate. Since the product was made with high-strength steel, the amount of material required reduced significantly as well as the construction period. Workers said that their work became easier because the product was light. Since then, DIB has been applied to about ten different sites and is currently receiving proposals from various projects. Acknowledged for its marketability and innovation, the product was certified as an official INNOVILT product in the first quarter of 2020.

l Half of the INNOVILT Certified Products Are Co-developed by POSCO & Client Companies

As in the case above, there are a total of 36 cases that have started with the joint development of POSCO and clients and resulted in an INNOVILT certified product. Considering that the number of INNOVILT products is 72 as of 3Q, these cases account for half of them. Some major examples of INNOVILT candidate products becoming certified products are as follows: Hankook Material’s SP-CIP Steel Wire Mesh Pipe, Daehan Gasul’s High Strength Jack Support, NI Steel’s Steel Curtain Wall, and Dokun Entech’s DIB.

▲ POSCO jointly develops next-generation INNOVILT candidate products with its client companies. Once the development and commercialization of these products are complete, products qualified as INNOVILT products are officially certified by the INNOVILT brand committee. As of the end of August 2020, 36 products were certified as INNOVILT products.

POSCO’s unique system of branding and managing client companies’ products is unprecedented — even overseas. Not only this, POSCO also works on developing products for client companies with its own resources and employees — something that is innovative in the industry. This explains why POSCO’s support for its clients is named “Full Range Solution”. With INNOVILT, a pinnacle of the value of steel, POSCO is determined to innovate construction materials in the rapidly advancing construction industry while growing together with business partners.

l All the Way with POSCO Experts

A considerable time of collaboration between POSCO and its client companies is required for an INNOVILT candidate product to be successfully developed and put on the market. The entire process is composed of 7 stages which are as follows: ① Market Analysis: Analyzing market needs in-depth and establishing product position, ② Product Designing: Coming up with an optimal design using various software programs, ③ Quality Verification: Verifying product quality with POSCO’s test equipment, the best of its kind in Korea, ④ Certification of Use: Securing objective evaluation of product quality from academic societies and associations, ⑤ Supply Chain Establishment: Establishing an efficient supply chain, ⑥ Track Record: Applying product in a test-site to check its practical potential, and ⑦ Mass Production: Expanding field application through full-fledged marketing.

As INNOVILT products are “premium” products that require high cost and a considerable amount of time to be developed, POSCO experts participate in the entire process. POSCO researchers are responsible for product development, from product designing, quality verification, and certification of use, to track recording. Even after the product is put into the market, POSCO analyzes its competitiveness, and if there is a need for improvement, the company conducts research task projects to supplement.

POSCO’s marketers propose developing new products to client companies by analyzing the current market. They also build supply chains to help products get to market quickly. In case an outstanding product lacks recognition in the market, the marketers propose participating in an exhibition or work to strengthen joint promotion. Simply put, POSCO works together with its client companies from the beginning of product development to the end process, marketing.

POSCO holds a brand committee every quarter to select INNOVILT products and to provide active support making sure that these INNOVILT products are utilized in the market as premium construction materials. In addition, POSCO plans to reach out to clients and conduct R&D so that innovative products can be developed continuously. POSCO will continue taking these unprecedented steps in hopes that they would help business partners and strengthen the overall demand industry.