From on-site training to master

Summer is here, bringing with it a number of construction students to Oodi worksite, there to gain valuable experience to support their university studies. Most students spend their first summer undergoing on-site training from the perspective of construction workers. More experienced students may also get to try their hand at supervision.

The summer employees at the Oodi site consider themselves lucky to be able to participate in such a notable project. The unique construction method offers plenty to learn, and experience from a historical site is sure to look good on one’s resume. Miika Ranta (on the left) and Anniina Kallioniemi (on the right) will eventually graduate as master builders from the Metropolia University of Applied Sciences, while Annukka Laurila (centre) is currently studying at Aalto University for a Master of Science (Technology) degree.

Although Miika Ranta is still young at 23, he already holds a vocational upper secondary qualification in construction, as well as plenty of experience in the construction industry. So far, he’s tried his hand at water damage restoration, sheet metal cladding, moulding, as well as window and fitting installation.

“At Oodi, I’m undergoing supervisor training, with my area of responsibility being interior fixed and operable glass walls. I’m getting to know quality requirements, measuring required quantities, as well as planning and scheduling construction work. Once the glass contractor arrives at the site, I’ll also get to supervise work for the first time. Over the summer, I’ll gain plenty of excellent experience to support my career as a master builder.”

A “minister of industry” in overalls

Annukka Laurila, 22, who is studying mechanical engineering and building technology at Aalto University, has a surprising dual role. While currently undergoing on-site training, she also works as Minister of Industry in the Guild of Mechanical Engineers.

“There are hundreds of students in the Guild of Mechanical Engineers, and I serve as the guild’s business relationship liaison. I procure funding and facilitate meetings between students and companies. I ended up here at the Oodi worksite after contacting YIT on guild business. They asked me if I had already found a summer job.”

“The Oodi site has a lot to give, seeing as how it’s unlike any other worksite. It’s cool to see how such large masses are being built on top of the arches and how the arches serve as buttresses. There’s a lot more to learn here than on smaller worksites.”

Continuing the family trade as master builder

Anniina Kallioniemi, 24, admits that she’s following in her family’s footsteps in becoming a master builder. Her father also works as a master builder, in addition to which there are a number of engineers and architects in her extended family. Although her father encouraged her to study and work in the same field, in the end, the decision to do so was Anniina’s own. Her fascination with the industry has continued to grow ever since.

“According to dad, I’ll make a great master builder because I’m good at maths, social and assertive. I originally thought about specialising in the humanities, and ended up studying to become an agrologist. I actually completed my Bachelor of Agriculture and Forestry degree a year ago. I’m also interested in horses, but decided to keep that as a hobby. I have a horse of my own, as well as a co-owned racehorse. I’m also into horse photography.”

“I’m thrilled to get to work at the Oodi site. We’re building something truly exceptional here at an incredible location!”

Steel frame on the third floor

The first two aboveground levels of the library will be clad in wood, while the third floor’s facade material is glass. In the early summer, the construction has proceeded to the third floor steel structures that will support the glass panels.

The glass-bearing white steel parts will remain visible even after construction is complete, while the grey beams and pillars on the lower floors will be hidden behind cladding. The white frame of the third floor is now slowly extending southward.

“The glass facade panels will most likely be manufactured in two different factories, since we need so many of them. The panels will have a printed surface, completely white on top and thinning towards the bottom. Currently we’re still in the design phase, after which we’ll proceed to commission the assembly,” says YIT’s senior site manager Tero Seppänen, whose artistic coffee cup was painted by his firstborn at day care a few years ago.

The support structures of the building’s load-bearing steel arches are now in the process of being dismantled, as all the welding work on the arches has been completed and the cast-in-situ slab supporting them has been tensioned. The removal of the supports will enable the installation of hollow-core slabs by the arches and the gradual extension of the third floor steel structures towards the south.

Numbers reveal what’s happening at the site

Site Office Manager Paula Antila views the construction of Oodi from a perspective of her own: through numbers. The majority of her working day is taken up by the processing of purchase invoices. They detail the materials arriving at the site as well as completed contract work.

“I check that the invoices are relevant to the project and have been drawn up according to agreements. I also verify that the goods have arrived, that we have a consignment note for them and that they have been signed for by supervisory staff. We share some of our tasks with the supervisory staff. Invoices are processed by others as well, and in accordance with our division of duties we register them to the budget, meaning the goal estimate. My duties also include posting the invoices to bookkeeping accounts and sending them on for approval.”

Every invoice is checked by up to ten people, so getting invalid invoices approved would be very difficult, even during the summer holiday season.

“Checking invoices is a multi-stage process at both YIT and the City organisation, and the regular professionals are never on holiday at the same time. I myself also have an experienced colleague who serves as my substitute when needed.”

In May, Paula reached a notable milestone on her career: 10 years of services at YIT.


Text and pictures: Liisa Joensuu/Tmi Magic Words



Nerves and blood vessels are born underground

If steel constructions form the skeleton of Oodi, building engineering represents its nerves and blood vessels. Now, capacities are being built to create electricity, heat, water and fresh air in the library. Technical systems originate underground, from the library basement.

The installation of building engineering is not carried out conventionally, as the possible movement of the frame of the building and, for example, the needs of the movie theatre and recording studio are taken into account during the installation process. In the basement, Are Talotekniikka Ltd employees, project manager Tony Lindholm (on the left), plumber Simo Järvelä (in the middle) and plumbing project manager Jani Lindvall, examine the installation map.

According to Lindholm and Lindvall, the possibility for the frame to move is rarely taken into consideration during installation of building engineering. In the Oodi building site, this possibility is linked to the indoors bridge that supports the building and requires flexibility for the structures. The solution is to install compensators in the pipelines to cushion the movement. Besides, several reference and dispatch points will be installed. These all suppress the noise and ventilation noise carried on in the pipelines.

“In this project, acoustics play a major part. The starting point is that the operations of the library are based on a soft soundscape. The noise reduction systems of the movie theatre and studio premises form a special challenge. Tailor-made sound attenuators will be installed in the movie theatre. These plans will be handed over to an acoustician, who will calculate the optimal octave bands and final decibels,” Tony Lindholm says.

Pipelines in clean spaces

One might think that the basement where the works are going on is cold, dark and dusty, but the basement of Oodi offers a surprise. Temporary heating is in operation, the lights are on and the premises are clean.

“This is a building site with purity class P1, which means that no dust particles are allowed in the air. Ventilators will arrive in a couple of weeks. They can’t get dirty already in the installation phase,” Tony Lindholm explains.

Several mechanical rooms will be built in the basement. The largest of these rooms will be as big as 100 square metres. In the mechanical room portrayed in the picture, the installation of the main pipeline is nearly finished. There are bushing sleeves in the walls for the future installation of pipelines. Eventually, the whole space will be filled with different types of machines and equipment.

The mechanical room will be fitted with the technology required by district heating and district cooling, and ventilation systems for heating and cooling, including heat recovery. The large pipeline in the middle of the picture is a ventilation duct.

The masonry work of the dividing walls and the main pipeline installations continue in different parts of the basement. The main pipelines form a network in the ceiling, as there can be as many as a dozen pipelines side by side. The liquid running in the pipeline is either water or glycol, depending on the purpose of usage – heating, cooling, drinking water or melting. The welder works on the branch of the pipeline which forms the coupling point to the radiators.

Plumber Simo Järvelä fitted grease trap hangers in the ceiling of a space that is below the kitchen of the restaurant. Institutional kitchens must be fitted with acid-proof sewers, as plastic pipes won’t cope with hot frying fats, among other things.

The skeleton grows above the ground

The supervisor in charge at YIT, Tero Seppänen, says that the construction of the frame of Oodi has progressed quickly. Over 65% of the steel structures have been installed. The frame should be nearly finished by the end of June.

“The frame requires a lot of work. We must think carefully about how to proceed. If there is some work that obstructs the works on the frame, we must reconsider the procedures and find alternative installation locations to keep up with the schedule. The skeleton will start to look like a building in the summer, when we start to install the roof and the wooden elements and glass structures in the facade.”

The welding works on the steel arches that support the building have been finished, and the inspection of the welds has also been carried out. Steel trusses have already been installed in between the arches as part of the massive truss structure of the frame. The cast-in-situ concrete plate that will be built in the upper part of the shaft in the picture will be stressed to support the steel arches sideways.

In the north end of the building, the installation of hollow core floor elements, i.e. the floors and ceilings between the different stories, has already started. In April, the work continued by the lobby, next to the movie theatre.

Trusses that support the balcony have been installed in the north end of the building. Trusses haven’t yet been installed in the middle of the building, as they would obstruct the cranes and the installation of the steel structures of the roof.

Aaro trained father during parental leave

Site engineer Topias Rintala has just returned to work from a “training period” of five months, i.e. parental leave. During the parental leave his one-year-old son Aaro taught him stress management, organisation and multitasking, among other things.

“With a small child you sometimes end up in tighter situations than at the workplace, especially now that the son has started to walk,” the father says.

Rintala moved to the library construction crew from a building site of a senior centre in Leppävaara. His tasks include supervising the timetable and costs. The training provided by Aaro became very useful, as it requires a swift reaction to jump into a moving train.


Text and pictures: Liisa Joensuu/Tmi Magic Words

Inside steel with an ultrasound

While cranes lift up heavy pillars and hollow-core slabs at the Oodi worksite, also light manual tools are needed for working on the details. Special attention has been paid to welded joints. In March, Suomen Testauspalvelu Oy began inspections of the welded joints of the steel arches that support the entire library. For this task, they needed a small ultrasound device, magnetic particles and a hand-held electromagnetic yoke.

“We started the inspections from the south and north ends of the arches. When a welded joint is inspected, it is complete. We make sure that no welding mistakes have occurred and that the welded joint has not cracked during cool-down. Even though welding is carried out inside a weather guard tent, it is possible that hydrogen may develop in the joint, especially during rain or in humid air conditions. This may cause a delayed crack”, said managing director Tarmo Tuomela while checking the screen of the ultrasound device.

These tests must be done very carefully, as the welded joints to be inspected with the ultrasound device are only two or three millimetres thick. There are so many of them that, together, they make up the whole thickness of the arch’s casing, 120 millimetres.

“The ultrasound device transmits the sound at the steel, using a selected angle. If the joint is faultless, the sound moves through the steel without any problems. Any defects reflect the sound back. Hand-welded joints quite often have small defects that reflect the sound back, and then we need to review whether the joint can be approved or whether it needs to be opened and rewelded”, Tarmo Tuomela says, explaining the basic idea behind the method.

In addition to the ultrasound inspections, magnetic particle inspection will be performed on the joints. First, Tarmo Tuomela will spray white paint as a contrast colour onto the surface of the steel casing’s welded surface. When the paint is dry, he will grab the spray bottle and cover the surface with some black magnetic particle powder. The idea of this method is that the magnetic particles will gather on the possible defect when the yoke (pictured) with positive and negative magnetic poles is held above the substance.

Weather guard tents are a clear sign of where welding work is taking place on the arches. Each arch has seven welding sites, which means that there are total of 14 places were joints are made. The weather guard tents of the end casings are not shown in the picture. The arch load is still resting on the support grids, at this point.

As an installation site, the Central Library is a medium-sized worksite for Suomen Testauspalvelu. Previously, the company performed the steel structure inspections for Kamppi shopping centre, for example, and it is also in charge of the inspections of the engineering works on REDI shopping centre’s steel parts.

“We carried out the first inspections of the library’s steel structures back at the Normek engineering works in Oulu. Our special competence is physical dimensional inspection, i.e. the control measurements of various parts. They establish whether steel pillars, for example, have been made correctly and whether their holes are in the right places. Even a small difference would multiply during the installation, causing major problems for the heavy structures”, says Tarmo Tuomela.

Pillars in place on the north side

The library will be built from the north side towards the south. For the general public, one of the most interesting points on the north side is the cinema, first of its kind in the history of Finnish libraries. In this computer model, the cinema is shown in red, as are the first steel pillars of the frame behind it.

The north end of the building, the space between the stairwell shafts and cinema, will house both premises for building services and office spaces. Installation of stair elements has been started in shaft number one, on the left. In shaft number two, the cast-in-situ works of staircase landings are in progress. The ends of the steel arches that support the building are shown in blue in the image.

The shape of the cinema and its ascending floor can be clearly seen in the image. The area has been covered with the first hollow-core slabs that will become the floors and ceilings of different floors.

Erection of the frame will start with the steel pillars. The vertical pillars will be joined by horizontal beams, and, gradually, the frame will become an enormous grid structure.

The root of a steel pillar is being prepared for installation next to the cinema, in the future foyer. The frame is being built one pillar and one beam at a time, like a jigsaw puzzle in a gigantic scale.

The western side of the completed building will feature a long balcony with a beautiful view towards Kansalaistori and the Parliament House. The balcony will also be built on steel grids. The southernmost of them was installed in March.

Each jigsaw puzzle piece and every installation costs money. These costs are monitored and budgeted for by site engineer Ville Nevala. He is studying civil engineering and construction economy at Aalto University.

“My thesis is almost finished. For my bachelor’s degree, my thesis subject was foundation and rock engineering, and my current thesis is related to planning management and scheduling.”

Nevala thinks that the Oodi worksite has stayed well within budget and on schedule. Nearing the spring, keeping to the schedule for frame works has required hiring some more resources.


Text and pictures: Liisa Joensuu/Tmi Magic Words

Highest quality all the way to welded joints

The quality of construction is constantly monitored in detail at the Oodi site. Everyday activities include operational and quality monitoring actions and recording the data from them. Everything is based on a quality monitoring plan, which site engineer Ahmed Ibrahim (in the picture) prepared for the central library as the thesis work for his Master’s degree.

‘Digital project management tools and mobile equipment make monitoring and documentation significantly simpler. All of the necessary data can be entered into the system directly on a tablet or phone, and it is available to everyone in real time,’ Ibrahim says.

The most eagerly awaited construction phase, which is the erection of the steel arches that support the entire library, is now ongoing on the site. Welding the parts together also requires precise quality control: the welded seams will be inspected using ultrasound equipment.

Ahmed Ibrahim says that software and cloud-based services are part of construction operations today. Production used to be managed by using files and files of papers, which were then transported from one person to the next, requiring pictures to be scanned and documents printed and sent by post.

‘These days, everyone uses the same software. We can document various observations and measurements, and attach pictures. One person inspects, another approves, and the designer signs everything. This allows us to build faster.’

Ahmed Ibrahim wrote his Master of Engineering thesis on ‘Leadership in quality assurance and creating the conditions – Helsinki Central Library project’. Based on the Finnish Congrid system, he developed a quality management matrix suitable to be used in other YIT sites as well.

Arches under the magnifying glass

As planned, the steel arches that support the library arrived at the site in 12 parts in February. Their erection could be started quickly, as the support structures were already in place.

The north ends of the steel arches were resting on the support grids before mid-February. Their bottom parts are protected by a weather guard tent, inside which they are connected to their housings.

‘The housings were made so well that we had no problems installing the ends of the arches. The bottoms have been welded inside the tents, because welding must be done safe from water, and the protective gases must stay within the welding area. For now, everything has gone well with the erection of the arches,’ says Pasi Parkkinen, Project Leader at Normek Oy.

The steel arches will end up supporting several structures, which means that the securing of the load-bearing capacity of the arches is being monitored particularly carefully. This means, for example, that the welded seams connecting the various parts are inspected dozens of times.

‘At first, the arches are only welded a little, so that the parts are connected, but the full weight of the arches rests on the support structures. One seam needs to be welded about 100 times before the arches are fully in place and the supports can be taken down,’ Parkkinen says.

Around ten people are working on the welding of the arches. Each seam is worked by two people at the same time. A third person is needed who is responsible for the pre-heating of the place to be welded and the additional materials, such as gas and welding wire. Pre-heating is important, because if the area being welded is too cold, the seam will crack.

The arches are welded on the inside, as well as on the outside. The welder has access to the arch housing through a hatch on the side. The piece of arch works like a chimney, letting all the fumes and gases out through its end. The housing is not only for small people: they are approximately two metres in width and height.

Ultrasound imaging for the welded seams

The use of ultrasound in the inspection of welded joints has become more and more common, and it is used on the Oodi site as well. The objective is to have intact seams, which can take the necessary load.

Structural engineers have appointed certain values to the seams, and an external certified institution, Suomen Testauspalvelu Oy, uses ultrasound to ensure the integrity of the seams and that their thickness corresponds to the defined values.

Shafts also support structures

Along with the steel arches, the lift and staircase shafts are also parts of the library’s supporting frame. The third shaft in the middle of the building supports even the steel arches.

The cast-in-situ slab, i.e. the floor, located on the third floor of the third shaft, is connected to the shaft, as well as the steel arches. The slab can be cast between the shaft and the arch structure once the steel arches are in place and the weldings are strong enough. The support grids for the arches are only removed after the cast-in-situ slab is finished.

The staircase landings are being prepared in the first shaft in the northern end. The first two large landings are cast in their places, and the smaller landing slabs are installed as elements. At the turn of March, the stairs themselves will arrive at the site as concrete elements, and their installation can begin.

Site engineer Unto Miettinen preparing coffee with his arm in a sling, and said that construction has already started on the fourth staircase shaft, and its first floor is already completed. The fifth shaft, which will be placed opposite the Sanoma House, is only begun once the steel arches are fully welded and the support structures, which currently block the way of the shaft, are removed. Miettinen pointed out that he isn’t wearing the sling due to an occupational injury, but that the problem lies in an older shoulder injury.


Text and pictures: Liisa Joensuu/Tmi Magic Words

A video on the construction of Oodi

See how the unique steel arcs of library Oodi are constructed on the video! The library is designed by ALA architects and built by YIT.

Watch the video here

More support structures for the arches

The installation plan of the most extraordinaire solution of the new library, the steel arches supporting the building, has been given more detail. Erection of this unique internal bridge requires a few more support structures, which means that the installation process has been delayed a little from the original schedule.

“The loads of the arch structure are very great. The original idea was that during the installation phase, the arches will be supported directly to the existing floor. However, more specific calculations proved that in addition to the vertical supports, the arch load should also be distributed with a horizontal grid that transfers the load to the footing structure. The horizontal grid will be introduced as a new solution,” says Tero Seppänen, YIT’s senior site manager.

During the installation phase, the arches will be supported with vertical and horizontal transmission grids. The horizontal grids required by the updated installation plan will be the first structures to arrive at the worksite before the arches, so the logistics plan was also updated. The support structures will not be removed until the arches have been welded into one structure and tensioned.

“The first grid delivery will arrive during the night at the turn of January and February, during week five, and the next during week six. The deliveries mean night shifts for the unloaders, as the loads will be delivered between midnight and four am. The first installations of the arches will begin sometime before mid-February,” says Tero Seppänen.

Finnish construction ethics dictate that safety is not to be compromised in order to make the work go faster, not even when the deadline is approaching. The change in the design proves how important it is to supervise how theory and practise come together and adapt the plans as the situation requires.

While the transverse support grids have been manufactured in Oulu at Normek Oy factories, the on-site workers have assembled a tracked lattice boom crane, Havator, for installing the arch structure. It was delivered in several pieces from Äänekoski, from the worksite of Metsä Group’s bio-product plant. The wide wheelbase of the tracks takes up a lot of space, and very large steel elements will be delivered to the site, which means that the worksite had to be extended further. Since the fence was moved in December, it has been moved again towards the west and the Parliament House. The arches will be transported to Helsinki in 12 separate pieces. Each delivery carries two pieces, so, in total, there will be six deliveries.

Lifting the arches requires detailed plans

When one part of an individual arch weighs more than 85,000 kilos, the process ahead will be a heavy jigsaw puzzle that requires careful preparations. In addition to the lifting and installation plans, detailed occupational safety plans are needed. All of this has kept YIT’s worksite manager and occupational safety manager Mansoor Ardam busy. He acts as YIT’s supervisor during the steel frame’s installation.

“Success is based on careful planning. The arches and grids are a challenge, but we will proceed in bits and pieces, one matter at a time and in accordance with the plans approved by the structural engineer. The work will be paused, if we notice a safety risk. It is important to react in time during the implementation phase, so that the support towers can hold, lifts succeed and everyone can go home safe and sound after the workday. Motivation is strong, and even if the project is complex, it does not have to be complicated.”

Mansoor Ardam has construction work in his blood. He says that his grandfather was a major contractor in the Afghan state. Mansoor came to Finland in 2005, and in 2012 he graduated as a civil engineer from the Häme University of Applied Sciences. Currently, he is studying for a degree in Master of Engineering in an Industrial Management degree programme in English. He will graduate in May.

“Large projects are already familiar to me. I’ve been in part of the construction projects of HKL’s metro depot in Roihuvuori and Otaniemi metro station. Both were successful, transferred over with zero errors.”

First shafts about to be completed

The construction of lift and stair shafts has progressed on schedule, and the cast-in-situ works of the three first shafts are almost complete. At the beginning of February, the work for the fourth shaft can be started.

The first shaft in the northern end of the building will be around 20 metres high. It reaches through the entire building, from the cellar level to the third floor. The eaves height of the building itself is 23 metres. Next to the shaft, part of the movie theatre wall and the shape of its space can already be seen. The actual building construction will also start from the north end: the first steel pillars and grids will be erected in February.

It is easy to watch the shafts being built, but a lot is also going on below the ground, for example, in the process of covering the concrete vault seen in front of shaft number three. Temporary heating was installed for the basement, as masonry works were started in the premises. During the masonry works of the basement’s partition walls, channels for ventilation and electric system pipes will also be made. ARE was selected as the building system contractor that will manage heating, water, ventilation, electricity and automation works.

When the lattice boom crane’s chains start to lift up the pieces of steel, they can also be seen from far outside the worksite. The crane will see some action as the winter starts to turn towards spring.



Text and pictures: Liisa Joensuu/Tmi Magic Words

Make way for the new crane!

Caterpillar tracks will soon be making their way through the centre of Helsinki. New lifting capacity is required for the library construction site, and a new lattice boom crawler with rigging will see to that. In mid-December, a route was cleared for the new crane.

‘Lattice boom cranes are not seen on building construction sites every day, We need this 300-tonne Havator with rigging because it can move from place to place while carrying a load. We have to dismantle our tower crane to make room for the steel arcs’, explains Tero Seppänen (right), YIT’s senior site manager.

A team from Normek Oy has already arrived at the site for the erection of the steel arcs. Alongside Seppänen, the site map and the route for the new monster is being studied by Normek’s site manager Markku Roininen (left) and YIT’s site engineer Unto Miettinen.

For the time being, the tower crane has been joined by the wheel-mounted car hoist shown in the front of the picture, which took care of lifting the northern stairway shaft and the wall moulds for the movie theatre in December. The car hoist is supported by adjustable legs, which makes it unsuitable for the erection phase of the steel arcs.

The three northern shafts were worked on during the end of the year. This picture shows the tower crane lowering a wall mould into shaft three, in which both a lift shaft and a staircase will be built. The scaffolding is being built up as the moulds for the concrete castings are put in place. The tower crane is to be dismantled during the second week of January.

YIT has cleared the construction site and expanded it. The site is now intersected by a clear route for the new monster of a crane. A new gateway has been opened at the southern end of the plot, in front of Sanomatalo, and the site fence has been moved out to the west towards Kansalaistori. This additional space will be necessary as the parts for the steel arcs that will later on support the entire library arrive in January, along with their temporary supports.

Steel arcs arrive in batches during the night

The arrival of the support structures for the arc solution has been scheduled for the first week of January. Even though this delivery will only cover the supports and not the arcs themselves, the parts will be massive, reaching 10 metres in height. A total of ten support structures will be set up at the joints of the actual steel arcs that will then support the library.

According to the schedule, the parts for the actual arcs will be delivered in week 3. The parts for both steel arcs will be delivered in one batch. The delivery is therefore so big that its transportation is scheduled for a quiet time of day.

‘One part for one arc weighs over 85,000 kilos. With the delivery truck weighing 100 tonnes, its progress is slow and every turn takes a lot of time. On main roads, such a delivery causes a lot of disruption, and it can only be delivered in the centre of Helsinki in the middle of the night. The delivery will be coming from Normek’s facilities in Oulu. The vehicle cannot manage tight curves, and the only route with sufficient space is from behind the old storehouse,’ Seppänen explains.

‘The support structures will be completed as far as possible in early January. This will allow us to get the first pieces of the arcs in their places soon after they arrive. Even though the arcs now seem like the most impressive parts on the site, the fact is that erecting them is quite simple, and the challenges will only begin after that phase’, site engineer Unto Miettinen says.

The traverse steel gratings that will support the frame of the upper floors will be supported by the steel arcs when they are in place. The western arc is more sturdy than the eastern one, because it will bear a higher load. In comparison, the eastern gate could almost be called petite. The structure is new for YIT, but the cooperation partner for the phase, Normek, has already erected a similar arc structure in Helsinki.

The maker of the arcs also erected Isoisänsilta (‘Grandfather’s bridge’)

The Isoisänsilta bridge, which opened for bicycle and pedestrian traffic between Kalasatama and Mustikkamaa in September, was also erected by Normek. Unlike the library, however, the bridge did not include any structures that would need to be supported.

‘The library has a harsher structure’, says Normek’s site manager Markku Roininen, adding that the location in the centre of the city creates a bigger challenge.

The same installers who gained experience in the bridge project were available for this erection, bringing continuity to the installations for Normek. It may be surprising that only 2–4 installers are needed, compared to a total of eight welders.

The first parts of the arcs will be put into place at the southern end of the site. Roininen doesn’t foresee any problems with attaching the ends of the arcs to the steel casings that wait for them. Normek made the casings and arcs, and the parts were manufactured in Oulu exactly to measure.

The safety precautions on the site have been increased. Electric gates were installed on the fence, and everyone must be identified on their way in as well as out. YIT’s village of yellow containers already has three floors, because since the excavation phase, the number of people has increased by 20. A total of 57 experts in various fields now work on the site.


Text and pictures: Liisa Joensuu/Tmi Magic Words

Above ground construction starts with shafts

Worksite stories opened a new chapter in November. YIT took over the site, set up a village of yellow containers at the side of the park and brought many new characters into the story. Now, we will start construction above the ground. First, we will build the staircase and lift shafts, such as the northern stair shaft shown at the front of the picture. The building itself will be built from the north side towards the south.

The YIT’s site management team is excited about starting the building’s construction project. This is an one-of-a-kind project, in which we will build a unique building in the middle of Helsinki. For all those participating in the construction process, the building will become a historical part of their portfolio.

“The project’s challenges are related to the building structures that have not been often used in Finland. The frame structure is exceptional, but challenging projects teach us the most,” says senior site manager Tero Seppänen.

The library will become an urban space for millions of people and a new meeting place for them. According to Seppänen, this is a rewarding concept. The constructors will have the opportunity to bring added value to the lives of people. Team photo. From the left: site engineer Ville Nevala, site manager Janne Kurikka, senior site manager Tero Seppänen, site management intern Miika Luokkala, site manager Ardam Mansoor and site engineer Unto Miettinen.

At first, we compiled a shared schedule and then started the preparations for cast-in-situ structures. The worksite has five shafts, and during their cast-in-situ stage we will need around 30 workers on site. Tero Seppänen points at shaft number three, which is the site’s most important shaft.

The site will expand outside the current fences. After the turn of the year, new fences will be erected from the old magasin building towards Kansalaistori.

The building has been roughly divided into three sections: the northern A section, the middle B section and the southern C section. Each section has its own, more specific blocks. At first, we will start with the northern shafts, numbers 1 and 2, and the middle shaft number 3. Shaft number one will have stairs, shaft number two a lift and shaft number three both a lift and stairs.

“We have named shaft number four as ‘back-up place’. If work in other shafts will have to be put on hold for any reason, we will transfer the workgroup into this shaft. Three work teams are building the shafts,” says Tero Seppänen.

The southernmost shaft, shaft number five, will house stairs. The southern end of the building has an option for a city centre tunnel that would, according to initial plans, go from Länsiväylä to Sörnäisten rantatie, below the city centre. Through the stairs of shaft number five, people can exit the car tunnel by foot, if necessary.

Preparations for erecting the steel arches soon underway

These five shafts are standard construction projects, but the preparations for erecting the steel arches that support the entire library will be started in December. For these, we will first build temporary supports. Installing the actual arches will begin in January and if all goes according to the plan, the installation process could be finished in March.

Pictured are the stairway and lift shafts and the steel arches. The northern stairway shaft, pictured at the front of the image, is located on the side of a future film theatre. In the computer model, the film theatre’s stand is shown in violet colour.

“Due to the frame’s arch structure, certain movement margins must be taken into account. When the arches are burdened with the structures they support, they will bend down. Due to this, we will not make the permanent structures before the entire structural load of the arches has been built. We will leave expansion joints and movement margins for structures in several places.”

The finished building will also have a movement margin of a few tens of millimetres, as due to the arch structure solution, the payload – furniture, items and people – may move the structures. This movement is so small that the people inside will not notice it.

The tower crane placed in the middle of the worksite is in the way of the arch installations, which means that it will eventually be disassembled and replaced by mobile cranes. In the picture, the north-side end housings are shown on the left side of the crane and the cast moulds of the third shaft can be seen behind them. Both a lift and stairs will be built into the shaft.

A work team for preparing and erecting the arches will arrive at the worksite from Normek Oy. After installing the temporary supports, the arches will be mounted on them as separate pieces. Each arch has been divided into four sections. Finally, these pieces will be welded together.

With its curved walls, the form of this building is also extraordinary. According to Tero Seppänen, however, this does not slow down the building process or require much manual work.

“The curve forms over a long expanse of the structure, and it is possible to use elements for the outer walls. The wood panelling will be made over the elements. The frame also has many steel structures.” The floor levels are made of hollow-core slabs, which enable the quick building of large surface areas. Due to the arch structure solution, the hollow-core slabs will not be cast together immediately. The slabs will mostly be left without seams until the building’s total mass rests on the load-bearing arches and the arches have bent down equally to the load of the total mass. Only after this, the floors – which are also the roofs of the lower floors – will be cast.

Tero Seppänen takes things calmly. He has been working in construction for 20 years and has worked in site management for nearly as long. He knows that the project will proceed gradually and in smaller sub-projects. Several operators take part in the project and they all have their own roles. Architects and structural engineers manage their own duties and YIT is in charge of implementation.

For YIT, the unusual part of this project is that it does not start from a ‘clear table’ or as an unconstructed site. E.M. Pekkinen Oy has already carried through the bedrock excavation, civil engineering and basement construction works. Their work will still continue in the basement in the form of floor casts and sewer works, and the company will also finish the refill works of the sides of the building. The masonry works of the basement partition walls starts in January.

“When the partitions have been built in the basement, we will start constructing the machine rooms for building services. The brickwork walls will have openings for sewer and ventilation pipes and cable trays. In fact, the building services works are underway, as electrical piping has already been installed into the shafts,” says Tero Seppänen.

As the new constructor starts its work and the building starts to grow above ground, more attention will be paid to worksite supervision. Camera surveillance system will be installed, including motion sensors and alarms. The guards will be there within a few minutes.

Any communication of the building project of Central Library will be as open as possible. The Premises Centre, the library and YIT held a meeting together at the end of November, discussing each of their communication needs. In the future, information will also be available through YIT’s channels.



Text and pictures: Liisa Joensuu/Tmi Magic Words

Concrete work around the clock

The construction of the basement ceiling has meant long days and weekends at work for dozens of people. The plans have been revised as the work has proceeded, and reinforcements and new structures have been made along the way. Everything has been possible through flexibility, and the work has advanced at an amazing pace. The picture shows the cleaning stage of the southern end of the site, because the wooden casting moulds have already been dismantled.

‘We have tightened our schedule, working 12-hour days and throughout weekends since summer’, says Site Manager Kyösti Kontio.

The only place which still requires concreting as October draws to an end is the bull block of the bridge cover, shown on the right side of the picture with the steel reinforcements visible. A challenging task was beginning: the bull block would draw even more concrete than the 500 cubic metres required for the latest casting part of the basement ceiling.

‘A high load is focused on the bull block, as the steel arches of the interior bridge, which support the higher floors, are to rest on it. Some 800 cubic metres of concrete is used for the bull block alone. Even though the rectangular shape of the block is simple enough, the concreting still has to be carried out successfully in one go for every single square metre. The block is 10 metres wide and 105 metres tall, and counting the metal parts, the total area to be concreted adds up to some 1,100 square metres’, Kontio explains.

Anchoring cables tightened three times

The trick of the bull block lies in the anchoring cables running through it, which ensure the durability of the steel bridge which will support the library.

The anchoring cables are drawn between the southern and northern ends of the bridge. When the cables are tightened, the bridge arches reach their full bearing capability, and will not be able to separate from each other. This solution allows for the 100 metres of open space with no pillars in the first floor lobby of the library.

Both ends of the cables are drawn through the steel slabs which are a part of the housing structure complex. The above picture shows the housing structure complex at the northern end. The cables are still untightened, running through the holes of the steel slab. The slab has a total of 17 holes for the cable bundles. One bundle holds 31 cables, which brings the total number of cables to 527.

The total weight of the cables between the southern and northern end is 70,000 kilos, which is roughly equivalent to 70 average passenger cars. Sturdy solutions are required in order to ensure that the bridge structure can carry all three floors of the library, as even the traverse steel gratings that support the frame of the upper floors are supported by the arches of the bridge.

The cable bundles have been slipped into silver-coloured protective casings, which can be seen in the picture above, before the bull block was concreted. The cables can be tightened for the first time after the casting has been finished and the concrete has dried.

The first of three tightening rounds will be done from the southern end of the site. The second tightening will take place once the steel arch has been lifted into place, and surprisingly enough, the third after the entire building has been completed. This steel slab area at the southern end of the site is left open for a long time, so that the final tightening can be done here. A hole is also left inside the library behind the northern housing structure in order to allow the cables to be tightened even as the construction proceeds.

At the northern end, near the facilities of the future cinema, another hole is left so a two metre long and 50 cm wide jack can be placed behind the bridge housing structure and the anchoring cables can be tightened after the building is completed. At this point, some holes have also been left in the ceiling of the basement, which will allow supplies to be lowered to the basement for the work being continued there.

Floor castings beginning in the basement

Even though the ceiling has already been cast over the basement, plenty of work is still being carried below it. During the past weeks the underdrain and drainage systems have been built and radon pipes installed. Some places are beginning to look ready for the first floor castings: floor fillings are completed, and the insulating urethane plates are in place.

Runs for drainage pipes and air ducts, for example, are being prepared on the basement ceiling. The picture shows the bottom of the pipe channel on the eastern side of the site. Once this task is completed, concrete will be poured over the channel. At these times some 40 people are working on various assignments around the site.

The steel reinforcements of the bull block are beginning to hint at the curved shape of the exterior wall. The upright reinforcements show the line for the reinforcements of the socles of the exterior wall. Once the concreting is finished, E.M. Pekkinen will pass the baton on to YIT. The Pekkinen flag will come down from the flagpole in November. The curved shapes drawn by the architects are sure to present inspiration but also a challenge to the construction contractor.


Text and pictures: Liisa Joensuu/Tmi Magic Words

Tensioning a bridge with liquorice and bearings

As autumn arrives, so have the preparations for a thriller of its kind: the bridge cover is drawn onto the basement ceiling. It is a part of the exceptional structure of the library, the indoor bridge, which will support the upper floors. Cables are used to create a tension to the bridge cover, in order to improve the load bearing capacity of the structure. The cable looks like spun steel wire, and it stretches over dozens of metres.

The next thing that happens is a plot twist that couldn’t be anticipated by laymen: after the cables are tightened, the floor is far from stable. However, to engineers, the following steps of the story are familiar: a slight clearance is designed into the bridge cover, in order to make the structure more durable during temperature changes. The clearance required for the bridge indoors is not large, but it should be prepared for. This is the cue for bearings. One of the directors of the play is construction supervisor Kari Suomala, shown in the picture above.

The vault, or ceiling, of the basement is cast supported by the yellow formwork panels, which will be removed once the concrete has dried. The tension cables, which look like liquorice ropes, have been installed between the moulds on their brackets, and the surrounding steel reinforcement will also be covered with concrete. The picture shows the passive ends of the tension cables. This means that the tension will be created in the northern end.

The first scoops of dirt and sand were dug on the plot in September last year. Once the basement was constructed, the site returned above ground. The basement has been hidden underneath the casting moulds and steel reinforcements, and a random passer-by might not guess that they hide the concrete structures, pillars, partition walls, lift shafts, underdrain system, pumping station, driving ramps, and loading yard, as well as many other things. The narrow ditch around the basement is being filled with sand until the level reaches ground level, because 80 per cent of the waterproofing bitumen felt layers and thermal insulations are already in their places.


The mouldings stretch from south to north as one large field. At the moment, the people working with the steel reinforcements are under a great deal of time pressure: castings are being made at an increasing rate, and a steady line of concrete trucks visit the site every day. The picture above shows the site management exchanging information on their observations.

The concrete castings are ongoing in the southern end of the site, which is the ground-supported part. 200 cubic metres of cast concrete is no big feat for any one day. The concrete is floated and smoothed using machinery and as handwork. In front of the Sanomatalo building, excavation machines pick out the parts of the grooved wall, which was used to support the ditch.

Bearings allow the bridge cover to move

When you hear the word ‘bearing’, you might think of rounded ball bearings, but that is not the case with bridge construction.

‘The clearance for the bridge cover is ensured using slab-like bearings, which are similar to those used in bridges for vehicle traffic. In the case of traffic bridges, reservations are also made for a large variation in temperature: the bridge cover will stretch in hot weather, and contract in sub-zero temperatures. Long bridges also have expansion joint equipment, which emits a small bang when it is driven over. Without the expansion joint equipment, a gap of up to 10 cm could form by the seams of the bridge. Such an equipment is not required for the library bridge, because it is placed in a space with a stable temperature,’ explains Site Manager Kyösti Kontio.

One of the more brilliant turns of the plot is placed here, underneath the end housings of the steel bridge which will be built: who would have guessed that slab-like bearings were slid between the housing structure and the footing before the footing was covered by the casting moulds and iron reinforcements? In effect, the housing structure rests over the bearings, and if necessary, can slide for approximately 5 cm. However, that would require an approximately 40 degree change in temperature.

The computer model shows the side profile of the housing structure. The slab-like bearing plates can be seen as the bright green stack in the middle of the picture. They sort of look like a set of chopping boards. A Teflon coating between the steel beam (shown in grey) and the bearings (green) makes the movement easier. Extremely hard grouting concrete has been cast between the largest bearing plate and the concrete footing below it (shown in blue). But there is no cause for concern: even considering the clearance, the library floor is not intended to sway like the sea.

Liquorice and Luke

The library construction site has a surprisingly international atmosphere. The crane operator is Cuban, and various other roles include people from Russia as well as Morocco.

‘The construction business was international when IT was in its child’s shoes. Our sites have employed people from around the world for years,’ Kontio says.

Luke Parsons from Australia is one of the newest faces at the library site. The young man moved to Finland because of love, after having lived in Australia with his Finnish girlfriend. Luke has previously operated many kinds of machinery at a coal mine. He found the job at the library construction through his girlfriend’s father.

‘Work is going well, but I’m a bit afraid of the winter coming. I’ve heard that it’s only a matter of how you dress. If I can make it through the winter, I believe there won’t be any problems surviving in Finland,’ he ponders.

As for the clothing, he has already received some instructions: it’s no good going to work in shorts and flip-flops in September.



Text and pictures: Liisa Joensuu/Tmi Magic Words