In this state of affairs, the concept of structural reinforcement of the tower included the following measures: strengthening and underpinning foundations from the west and north, bracing the tower in horizontal planes with reinforced concrete shields, which also took over the function of the ceilings, strengthening the structure of pillars and other parts of the walls in terms of strength by means of injection mortar penetration and by means of transverse and longitudinal reinforcement introduced into the working sections, reinforcement of the body with an additional system of steel anchors inserted into the cross-section of the walls through specially drilled holes, later filled with mortar by pressure injection. After these procedures of fundamental importance were carried out, the masses of walls, which were not related to the date of creation of the monument, were successively removed, bay windows and interiors were reconstructed and the layout was adapted to new utility functions. Conservation work on the tower and adjacent underground parts lasted for 6 lat. Currently, this valuable monument with a unique medieval interior design is open to the public.
During conservation works related to the town hall tower, by ‘ strengthening the foundations were discovered outside the tower body on the north side, at a depth of 3.5-6.0 m below the current level of the Rynek plateau, well-preserved wall relics not recorded on any of the old plans. Detailed exploration works allowed to uncover the walls and part of the vaults, as well as many architectural details, which made it possible to fully read the assumptions in the plan of the building. It turned out, the exposed walls, from the 13th-14th centuries, they are walls separating several rooms of the oldest town hall. Based on found original Gothic architectural details, fragments of the ribs of the vaults, window and door frames, some interior details, floor tiles, etc. it was possible to recreate the spatial arrangement of the rooms. Therefore, the Presidium of the National Council m. Kraków decided to reconstruct the underground rooms and make them available to the public in a new utility function.
Basements with an area of approx. 400,0 no usable area have been reconstructed in medieval decor and adapted for public purposes.
Town hall tower in Krakow. Restored basement and ceiling structure
Among the various construction problems, special attention was paid to the solution of the basement covering. In this situation, the rooms were completely under the plate of the orderly Market Square.
Whereas, that the rebuilt stone and brick vaults should be isolated from shocks, caused by vehicles passing over these vaults, especially in the event of a fire, as well as crowds of people during celebrations and mass gatherings, it was decided to spread a massive reinforced concrete ceiling over the vaults, which, on the one hand, would completely relieve the vault from external static and dynamic loads, on the other hand, it served as an insulating screen against shocks and vibrations, caused by traffic.
It needs to be highlighted that, that during the reconstruction of the vaults they could also be strengthened in this way, so that they can take over all the burdens themselves. However, the described variant was chosen, which allows you to completely isolate both the vaults from the sources of shocks, and some parts of the walls.
The use of the described solution made it possible to isolate the underground room from moisture in a more beneficial way, and at the same time correctly solve the insulation of the vaults and make their construction independent of thermal influences, to which the surface of the newly shaped Market Square is constantly exposed.
The technical work was very unusual and tedious, because they also had to take into account the requirements of sanitary technology, especially heating and full air conditioning. During the work to strengthen the tower and discovered. underground, constant supervision and control examinations had to be carried out. attention to public safety.