REHABILITATION OF THE OLD BRIDGE

MOSTAR

NEWSLETTER    7                         JANUARY 31, 2003         MOSTAR, BOSNIA AND HERZEGOVINA

 

Pavement assembled and pallets prepared for stone blocks

 

DISLOCATION OF STONES TO THE CEMETERY

SEMOVAC COMPLETED

 

On 13th January 2003, the last stone from the Old Bridge was dislocated to cemetery Semovac. This provides permanent free access to each stone from the bridge.  

 

Pavement from the left bridge entrance

 

Pavement remnants whose dismantling started on 31.10.2002 are ranged in the same way they were on both entrances of the bridge and bridge remnant on the left side. This way it will be easier in the future to classify, choose and take all necessary data on quantities and dimensions of missing pieces of pavement, and those that will be built in the bridge again.

 

Assembled stone blocks

 

Present experts on the session:

 

1.  Dr. Mounir Bouchenaki, Member of the ICE, Assistant   

     Director General of UNESCO for Culture

2.  Mr. Laurent Levi-Strauss, Deputy Director of the division

     for Cultural Heritage - Tangible Heritage CLT/CH/TH

3.  Prof. dr. Leon Pressouyre, Chairman of the ICE,

     archeologist

4. Dr. Azeddine Beschaouch, Member of the ICE, archeologist

 

Prof. Pekovic explains the results of archaeol. excavations

 

5.   Prof. dr. Giorgio Macchi, Member of the ICE, civil engineer

6.   Prof. dr. Gaby Dolff - Bonekamper, Member of the ICE, art

      historian

7.   Prof. dr. Radovan Ivancevic, Member of the ICE, art

      historian

8.   Mr. Ferhad Mulabegovic, Member of the ICE, architect

9.   Prof. dr. Zlatko Langof, Member of the ICE, civil engineer

10. Prof. dr. Mihailo Muravljov, Member of the ICE, civil  

      engineer

11. Prof. dr. Cevat Erder,  Member of the ICE, architect

12. Prof. dr. Eddy De Witte, Member of the ICE, expert for the

      materials,

 

and representatives of PCU-a (Rusmir Cisic and Tihomir Rozic), the Supervison (Zeljko Pekovic, Blaz Gotovac and Dragan Milasinovic) and the Contractor (Snjezana Hadzic and Maja Popovac).

 

Press conference

 

Few days after the session, team of experts gave the following propositions and recommendations:

 

Recomendations

 

CENTERING

 

Considering that it is necessary for the bridge reconstruction not to focus only on the technical discussion and documentation of the centering design but  also to  take into

 

 

Appropriate materials are stainless steel and titanium.

 

 

Cramp built in blocks and leaded

 

 

MORTARS

 

It is recommended that, according to the Venice Charter, only mixtures proven by long-term application should be used as mortar for filling the joints of the stone masonry.  However, cement mortar should be avoided.

 

The vertical joints of the arch should preferably be less than 10 mm thick.  In the case of use of traditional lime mortar, centering should be in place for a period sufficient to reach partial carbonation and solidity.  Experimental applications on site or in the laboratory should be resorted to in order to check the appropriate consistency for a satisfactory application.

 

Old bridge before destruction

 

 

GEOMETRY

 

It is again recommended that the geometry of the Old Bridge be kept according to the photogrammetric survey done in 1982, with only minor modifications where needed and justified.  The structural calculations by finite elements should be done by applying permanent and variable actions and seismic actions to a numerical model built according to such a geometry.  Such calculations have not yet been presented to the ICE.

 

 

STONE-CUTTING WORKS BEGAN

 

These days, test cutting and connecting of stone blocks began in stone storage in Komos.

 

Blocks of desired size, in this case from tenelija waste material which  is  the same  quality  as  the  one  that  will  be  

 

 

Auxiliary construction for lifting the transversal grids

 

CENTERING

 

After production of concrete pillars, preparatory works for lifting the transversal grids began. Between the pillars on both sides, auxiliary steel constructions were placed and they served only for lifting the grids.

 

Parts of steel grids on the platform

 

Each of these four steel grids was made in three parts for easier transport. Even then, because of the enormous  dimensions, their transport from Zivinice, through Sarajevo to Mostar was treated as special transport and demanded special permits from authorized ministries. 

 

Transversal grids arrived on the platform on 15.01.2003.  They were brought on the pontoon by crane, where they were put together, and then manually, using the system of steel iron ropes and chains were individually lifted on concrete pillars.

 

Lifting of steel grids

 

 

Dislocation of remnants of stone blocks began on 27.12.2002, and was finished on 13.01.2003. Blocks are assembled on wooden pallets, and great effort was made in order not to damage them during transport, and for their marks to be visible for easier identification later on.

 

 

 

7th SESSION OF THE INTERNATIONAL COMMITTEE OF EXPERTS

 

 

1st  session in Center for Culture

 

On 15th and 16th of January in Center for Culture 7th session of the International committee of experts was held.

 

During the session, experts were introduced with the work progress, several times they had an opportunity to visit the Site, and talk with the workers and the staff in charge. Representatives of the Contractor and Supervision Teams held several presentations for the experts about different fazes and aspects of the project.

 

Experts during visit to the Site

 

Only after few visits to the Site and presentations in the Centre, experts expressed their satisfaction with the progress and the quality of works on the bridge.

 

After completed presentations and discussions, press conference was held, on which Mr. Bouchenaki, Mr. Ćišić and Mr. Rozić informed media representatives about all activities during the session, about comments of team members and plans for further work progress.

 

 

consideration the close link between the arch concept of the Old Bridge and the centering, the experts adopted the following recommendations:

 

Transversal grids of the centering

 

1)       The actual centering design must be revised in order to consider all possible deflections, the compression of centering foundation columns, the rotation of the centering foundation columns and cantilevers, the horizontal venting.

2)       The revision must include radial beams and height regulators.

3)       It is  important to add to the centering a system of hydraulic jacks.

4)       Monitoring of the deflections of the centering by means of precision levelling should be permanent and a survey progremme should be defined.  Such a programme should envisage procedures appropriate to keep constant the points of the intrados of the arch.   

Detail of the centering

 

5)       It should be determined if there is enough space on both sides of the bridge for a secure access during the treatment of the joints.

6)       The temporary reinforced concrete pillars should be removed at the end of the works by demolition in such a way as to avoid any vibrations on the Old Bridge.  Appropriate means are helocoidal wires with diamond edges.

 

DOWELS

 

For dowels permanently connecting the stone blocks it is highly recommended to use the metals which have proved to be not subject to serious corrosion for a period of the order of 100 years. 

 

Carbon steels produced by modern industrial processes do not have the properties of the iron produced in the 16th century.  Their expansion caused by corrosion gives rise to ruptures of the stone.  

 

 

Tools for stone cutting

 

used on  the  bridge are manually treated, connected with mortar, cramps, dowels and leaded.      

 

This is how the stonecutters are preparing for the most difficult task which is before the Contractor – masonry of the arch. Techniques and the way of cutting are being tried out as well as treatment of the stone surface.

 

Workers are cutting stone blocks in Komos

 

The next step which is in front of the Contractor is to test segment of the arch, measure 1:1. This part would be cut apart after some time in order to determine how good and stabile the connections between materials are.

 

 

Leading

 

After cutting and treatment of blocks faces, square cavities are made inside the stone, in which the metal cramps are placed. After that, lead melted on gas flame is poured into cavities.  In this process it is important that the stone block is completely dry around the cavity, so the lead, whose temperature is enormous in that moment, does not cause its braking.

 

 

Partially cut stone block

 

REPAIR OF ABUTMENT WALLS

 

Works on abutment walls are almost completed. Stone blocks that were missing or were damaged, are replaced with new ones. Surface of each new block was treated in the same way as the surfaces of the old blocks

 

Left upstream abutment wall

 

Stone blocks are connected with steel cramps on their upper side and leaded. The difference in color between the old and the new blocks will equalize in relatively short period of time.

 

 

ARCHAEOLOGICAL EXPLORATIONS

 

Archaeological explorations on both sides of Neretva are almost finished. In the next newsletter number we will inform you of its results in more details.

 

Quadrant on the left bank

 

This NEWSLETTER was made in accordance with prevailing articles of the Contract No 002/2002 about the Rehabilitation of the Old Bridge, by ER-BU CONSTRUCTION / TURKEY