Acoustic screen doors with escape properties.

After previous cooperation on projects including the N3, the A50 and the A4, Heijmans is again calling on the expertise of Alara-Lukagro for the widening of the A1. The specialist in custom sound and noise control has been awarded nine acoustic screen doors with escape properties for the A1 Apeldoorn - Twello project. For the previous project A1 Apeldoorn - Azelo there were already three pieces
custom manufactured, delivered and assembled.

Alara-Lukagro's screen doors in the noise barriers along the A1 have a dual function. Through the door, people can safely leave the highway in case of an emergency. On the other hand, the doors provide emergency services with efficient access to the highway from the residents' side. "We delivered a first series of doors in 2020 and the second series in 2023," says Ronald van Ditshuizen, account manager at Alara-Lukagro. "Originally, we supply acoustic doors, grilles and partitions from the construction business unit, which have been supplemented over the years with all kinds of additional functions, whether combined or not, such as fire resistance, burglar resistance or with escape function and other specific functionalities. We can supply standard products as well as customized products. The latter is our strength. We are inventive and think along in solutions."

Sheet steel 

An escape door is included in a noise barrier every 400 meters so that people have to travel a maximum of 200 meters in case of an emergency. "Because this is a noise barrier, it is important that the doors are also soundproofed and seal well in the rebate," says Pieter Hanselaar, project engineer at Alara-Lukagro. "In this case, we used 80 mm sheet steel doors with an acoustic core and a rubber seal all around. The door is equipped on the road side with a door handle with panic function and on the occupant side with a fixed knob. A special triangular key allows emergency services to unlock the mechanical lock. There is also a door closer so that the door locks automatically after use and we use a storm chain to limit the door opening.

Spar size

Alara-Lukagro prepared the screen doors ready-made in a steel frame, also acoustically insulated, so that the whole thing could be easily mounted on site in the recess of the sound barrier. "For projects like this, we actually use two options," Pieter explains. "Either we base the drawing work on practice, measuring the door on site, or we specify the recess size on the drawing so that the contractor can take this into account when building the noise barrier. Because of the lead time, Heijmans chose option 2 for the A1." Alara-Lukagro then assembled the doors on site in several phases: three pieces in 2020 for the A1 Apeldoorn - Azelo project and for the A1 Apeldoorn - Twello project two pieces in 2023, and the remaining seven are/were assembled in 2024. "The installation will take place in good mutual consultation with Heijmans, who will cordon off a road section for this purpose to ensure the safety of our mechanics."

Acoustic performance

The screen doors and frames are coated with a double layer wet paint system with a minimum layer thickness of 220 µm in the customer's desired RAL color, namely RAL 7039 (quartz gray). Also, the mechanical lock and the door closer are provided with a specific coating that makes the whole extremely resistant to the weather, Ronald assures. "In addition to the door and frame, we also finished the connection of the frame to the sound barrier acoustically to ensure a seamless whole. In this case, an acoustic performance of 25 dB was required." It is good to know that Alara-Lukagro is able to supply acoustic doors that can contain noise much further. For cinemas, studios and theaters among others that attenuate up to 56 dB of sound. "But also in infrastructure we sometimes get very challenging projects on our plate, especially if it concerns a sound barrier along a railroad line where sound waves have to be absorbed. We are also entrusted with that. We don't shy away from any challenge."