Escalators for La Losa

The design, execution, functionality and aesthetic of a TKE escalator project in Spain

submitted by TKE

In 1999, as part of a project called Cinturón Verde (Green Walk), the work to bury the railroad tracks in the center of the city of Oviedo, Spain, was completed. This involved the creation of a new square 700-m long with 38,000 m² of surface area over the station itself and the railroad lines, supported by 220 pillars. This deck is popularly known as La Losa and has become the most spacious and longest promenade in the city of Oviedo, including several fountains, ponds, lamp posts, gardens and spaces for children’s games, as well as several sculptures, such as “The Dolphin Man” by Salvador Dalí.

This action culminated in the elimination of the railway line that ran along the city, which was an architectural barrier that isolated the peripheral neighborhoods from the downtown area.

To overcome the unevenness generated in the surroundings of the railroad station, the main access road to “the slab” (which is the English translation of “la losa”), due to its location in front of the main street of Oviedo, Uría Street, a pair of outdoor escalators were installed on each side of the station to overcome the existing height of 9.41 m. Additionally, on the southwest side of the station, a hydraulic elevator was installed for use by people with reduced mobility.

These escalators became an essential element of urban mobility in the city, moving up to 8,000 people a day, according to current data.

More recently, the escalators were subject to two arson attacks, causing serious damage to the machines (2015 and 2021). After the second event, given that the equipment had already exceeded 20 years of useful life, the City Council of Oviedo opted for their replacement due to the high cost of repair.

In 2022, architect Arturo Suárez Alonso was awarded the project for the renovation of the escalators together with an improvement of the surroundings. In November 2023, TK Elevadores España, SLU, (TKE) as the successful bidder for all the work to be carried out (escalators, elevators and other environmental actions), began the work in accordance with the tendered project.

Between April and June 2023, the work was handed over to the City Council in several phases to speed up the commissioning of the different units. The last unit, the southwest elevator, was put into service on July 4, 2023.

Project Details

This project was unique based on the following aspects: design, execution, functionality and aesthetics.

Design

The most striking feature of this project is undoubtedly the escalator-canopy assemblies. These canopies, or roofs, are structures made of metal profiles with a square tubular section forming lattices.

Disadvantages arose due to the different ownership of the surrounding land, which made a simple approach impossible: It was not possible to support the canopies to the ground with straight feet. Other possibilities, such as a structure independent of the escalators to support them only at the extreme levels, had a negative impact on the final image and, in addition, required the installation of additional elements of relative importance, also affecting the cost of the work.

As an escalator manufacturer, TKE collaborated in the development of the solution that was finally implemented: The escalators and the canopies were to be considered as a single unit supported entirely by the escalator frames, specifically designed for this purpose. This solved the problem of land ownership and avoided the extra cost of complex additional structures which, in turn, would make assembly more difficult.

An additional measure was incorporated by the architect in charge to allow this design: The canopies would be covered with ETFE (ethylene tetrafluoroethylene) sheets, a single-layer system. ETFE is a plastic material that is highly resistant to heat, corrosion and UV rays. It is manufactured by extrusion with wide slot nozzles, up to 1,550 mm, and its thickness ranges from 50 to 250 microns. 

The main advantage it brought to the project was its weight of only 175 grams/m². It is a material totally impermeable to water, but with an adequate level of transparency, suitable for the final backlit finish that was proposed. In addition, it allowed printing with a design of small circles arranged in a diamond shape — a geometry designed for its integration with the shapes of the structures.

These coatings, using a combination of xerographic and transparent ETFE sheets, allowed the architect to obtain the desired eye-catching final finishes.

Execution

The main complexities in execution were due to:

Dimensional Tolerances

TKE worked with a cumulative tolerance of no more than 5 mm for structure lengths of more than 20 m, in roof-escalator couplings and in the upper faces of the galleries themselves. This tolerance was imposed by the assembly requirements of the ETFE sheets. This required the development of fabrication drawings to solve the problem of the truss tube joints, and topographical measurements were taken during the assembly phases to verify the measurements.

Access to Intervention Points

This was a construction site with almost continuous presence of scaffolding systems, elevating platforms and even baskets attached to cranes due to the impossibility of obtaining the necessary reaches with conventional platforms. With the access of operators to the roofs, elevator shafts, walkways and the sides of the pedestrian stairs being sometimes very complex, the positioning of these means was due to the limited space available.

Other Work at Heights

In addition to the work from hoists and/or scaffolding, safety procedures and measures had to be determined for each phase of the work for the correct development of the work (escalator shafts, sides of pedestrian stairways, etc.).

Load Lifting

The use of self-propelled cranes of up to 200 t was necessary for the removal of the existing escalators, the placement of the new stairs, the positioning of the elevator gantry way shaft and the placement of the covers.

The location of the work in the center of the town of Oviedo, in an area of high traffic of vehicles and people, with limited space and with many complications (commercial premises, railroad station, cab rank, handicapped parking or access to parking), required continuous execution plans that had to be approved by the City Council and local police.

In addition, the following disadvantages were present:

• Prohibition of positioning lifting or any other type of equipment, including material stockpiles, on the upper level of the slab. With the exception of the final phase of finishing off the ETFE sheets, the rest of the work had to be carried out with machines parked on the lower level.
• There was a subway parking lot in front of the lower landing of the stairs on the northeast side, which made it impossible to position cranes or heavy vehicles in this area, making it necessary to move trucks and cranes significantly away from the points of operation. This significantly increased the complexity of the maneuvers and forced the use of cranes of greater tonnage.
• Need to maintain open walkable routes: TKE was required to keep a passageway from Uría Street to Plaza de Los Ferroviarios open to the public at all times. To this end, a schedule was established that alternated work on each side of the railroad station, keeping a pedestrian stairway open and without interference from the lifts in use, with minimum margins for maneuvering to meet the required work deadlines. The striking nature of the maneuvers carried out and the means employed meant a permanent presence of the work during its execution in the local press.

Functionality

One of the main concerns of the City Council of Oviedo, as the owner of the facilities, is the equipment’s reliability. The escalators and elevators must be continuously available for use. The experience with the old machines showed daily stoppages due to vandalism and misuse. For example, as demonstrated by the recording systems of the new escalators, there are continuous daily stoppages caused by improper operation of the safety stops and the provoked actuation of the handrail entry safeties. In addition, the City Council required the possibility of programming schedules and modes of operation if required, as well as the incorporation of energy efficiency measures.

To meet these requirements, escalators and elevators are equipped with remote control and monitoring systems in real time with TKE’s Insight solution, which lets users:

• Know and visualize at all times the status of the machines from any computer or mobile device.
• Control and program their operating modes and schedules, including automatic mode with Stop&Go efficiency function, thanks to their speed regulation equipment and modern detection systems installed in the plinths along the entire length of the stairs.
• Give orders remotely and select the desired colors/schedules for your LED illuminations.

In addition, the technologies integrated in the machines allow automatic resetting in perfect safety conditions in the event of unjustified shutdowns, as in the case of improper activation of the emergency stops.

Finally, any possible incident in the normal operation of the machines will be automatically and instantly reported to TKE’s technical service, with details of what happened, for immediate correction.

Aesthetics

The geometry of the staircase-roof sets, the white color and its contrast with the surroundings, the striking of the Northeast elevator shaft with its walkway and the possibilities offered by the lighting systems have turned this work into a new landmark in the city of Oviedo. Furthermore, the City Council has planned calendars with lighting color changes for specific dates, such as local holidays (blue), World ALS Day (orange) or Women’s Day (pink).

These color changes can be programmed in remote mode, without the presence of technical personnel on site, thanks to built-in connectivity measures.

La Losa Project Team