This is how one of Buda's transport arteries is being renovated

The dismantling of the reinforced concrete bridge abutments and steel bridge supports protruding onto the cantilevered parts of the deck is on schedule at the southern overpass of Flórián Square in Óbuda. The two flyovers of one of the capital's major transport intersections are undergoing a complete overhaul with the general construction of KM Építő Kft., part of the Zrt. (BKK) project of the Budapest Transport Centre. Our newspaper was informed about the details during a site visit.

The overpasses were in dire need of renovation

The widening of the Árpád Bridge from 2 to 6 lanes made it necessary to build the Flórián Square flyovers in the early 1980s. The flyover, which is now approaching its 43rd year of life, is in a state of disrepair and its renovation has become urgent. The main reason for the current overpass renovation was the severe corrosion damage to the overhead beams due to dilatation soaking.

The works are currently underway on the south bridge, while traffic on the north flyover is unimpeded in two lanes. It is planned to move traffic to the renewed southern flyover in the autumn, when the reconstruction of the northern road overpass at Flórián Square will start.

Our March visit to the southern flyover revealed the following:

• temporary traffic engineering interventions were carried out before the start of the works to ensure the safety of road users,
• demolition work on the asphalt pavement of the flyover has been completed,
• after pavement milling, the ageing spray insulation of the entire bridge deck was removed,
• a condition survey of the existing reinforced concrete track slab, which has been exposed after the demolition of the asphalt pavement, is underway,
• on both sides of the flyover, individual scaffolding will be built to prevent the dispersion of debris during demolition works,
• demolition work on the existing steel bridge supports and guard rails has started,
• work began on the demolition of the reinforced concrete bridge abutment,
• on the flyover, demolition of the reinforced concrete structures above the supports has started on half the width of the flyover, where the investor has decided to remove the existing dilatations.

Brief information on the technical content of the southern flyover was provided by KM Építő Kft.

The flyover is structurally equivalent to a girder bridge with twelve spans and eleven openings, constructed with non-continuous prestressed reinforced concrete beams and a monolithic reinforced concrete deck.

Its structural length is almost 370 metres, with a maximum free opening of 30 metres. The pavement width varies between 8.5 and 9.3 metres and the superstructure was built in 1982 and 1984 respectively.

Preserve the edges that give the bridge its character

A key part of the project will be the construction of a new reinforced concrete bridge edge system, which will be a key aesthetic feature of the overpasses. The system of monolithic structural components and precast curbs will maintain the unaltered appearance of the superstructure.

The new monolithic edgings are used for drainage and for anchoring the safety steel bridge supports. Production of the new edging elements is still underway and installation of the edging is scheduled to start in May.

The new prefabricated edging elements represent a higher level of technical content, as the significantly higher technical performance increases the lifetime and durability of the prefabricated edging.

The last major renovation was also designed by Főmterv

Főmterv Budapest Engineering Design and Consultancy Zrt. is involved in the construction of a major road overpass in Budapest as a day-to-day participant. Főmterv Zrt. produced the original designs for the bridges, as well as the last major comprehensive refurbishment in the early 2000s, so they have the necessary expertise to carry out the design tasks for the current refurbishment.

During the visit, we learned that it gives the contractors great security to know the design history of all the technical content of the flyovers.

This is the solution to eliminate leaks

During the site visit, we also learned that, according to the investor's request, the aim of the renovation is to eliminate the supposedly developing leaks around the supports, so the demolition of dilatations is one of the project's tasks for all supports. The solution to the problem of leaking at the dilatation points was found on the design table, in consultation with the operator, to remove the dilatation sections in their entirety and to concrete them together. Concreting the superstructures together requires the installation of dilatation structures to allow greater movement at the bridge ends.

The photos taken by our newspaper also show that the environment around the dilatation is extremely degraded, the steel cover plates at the existing monolithic border have lost their function, they are completely destroyed."

Bridge abutments will have much higher load-bearing capacity

Due to the changes described above, the existing elastomeric hinges - which act as connectors between the structural elements - will be surface cleaned and preserved.

The free movement of the superstructure will be ensured by new spherical glass columns at the bridge ends, which will be able to withstand significantly higher loads. In these sections, the existing hinges are dismantled while the superstructure is slightly raised. The contractor will then use a hydraulic jack connected to a common oil circuit to raise the superstructure by 2-3 cm and replace the worn-out hinges.

Findings following the planned breakdowns

During the spring period, planned demolition works will be a major part of the works, and a full picture of the bridge's true condition will be available once these are completed. As we wrote in an earlier part of this article, the 43-year-old structure is in worse condition than its age, as confirmed by the condition of the reinforced concrete bridge deck that became visible after the asphalt pavement was demolished. In this context, the contractor has requested the involvement of an expert, an independent expert who will assist in determining the exact condition of the existing condition.

Following the demolition of the bridge parapets, the condition of the concrete surfaces covered by the edging will be of paramount importance.