Restoration works carried out on the historical

Mehmed Pasha Sokolovic Bridge across the

River Drina in Bosnia and Herzegovina

Halide Sert, Süheyla Yılmaz, Mutluhan Nas, Hakan Demirci, Ayşe Avşin,

G. Sibel Turan, Nurdan Apaydın

Ministry of Transport, Maritime Affairs and Communications, General Directorate of Highways, Department of Structures, Division of Historical Bridges, Ankara, TURKEY.

Abstract Having witnessed the development of many civilizations for centuries,

Anatolia has been knitted all around with road networks from end to end in order

to meet the transportation-based needs of communities such as communications,

military, trading etc. Within the process, the bridges that are a part of the transport

system have become a complementary part of the cultural history over time as

useful structures serving in terms of the commercial, economic, military, social

and cultural issues. This study reports the restoration project and application

studies conducted under the technical counseling and supervision of the General

Directorate of Highways between 2009 and 2016 on the Historical Mehmed Pasha

Sokolovic Bridge crossing over the river Drina within the boundaries of Republika

Srpska/Bosnia and Herzegovina and included in the World Heritage List in 2007,

and this study is believed to contribute to the restoration discipline requiring the

cooperation of different professional groups.

1 Introduction

In addition to constructing new roads and bridges, improving the existing

historical bridges through maintenance and repair is also among the primary duties

of the General Directorate of Highways. According to the Division of Historical

Bridges' Inventory (as of December 2015), there are a total of 1816 bridges at

home, including stone bridges (1721), wooden bridges (29), iron bridges (32) and

reinforced concrete bridges (34), and a total of 308 bridges abroad, including

(121) in Bosnia and Herzegovina, (25) in Greece, (11) in Kosovo, (2) in Croatia,

(42) in Serbia-Montenegro-Sandzak, (20) in Macedonia, (3) in Lebanon, (18) in

Albania, (26) in Bulgaria, (1) in Palestine, (4) in Iraq, (2) in Romania, (1) in

Hungary, (1) in T.R.N.C, (4) in Syria, (3) in Crimea, (1) in Saudi Arabia and (23)

in Egypt, which were built during the rule of Ottoman Empire.

2

2 Routes in the Balkans during the Ottoman Period

As an outpost of the Ottoman Empire, the Balkans had always a strategic

importance for Istanbul, that served as the Empire's capital as of 1453, and acted

as a technology, information and communication bridge between the Ottoman

Empire and the Europe. Due to this strategic importance of the Balkans, the routes

connecting Anatolia to the Balkans and to the inner Europe has always maintained

its importance. These paths were composed of three main routes, including the

Right, Center and Left Arm departing from Istanbul, and secondary road

connected to these main routes and these three routes connected the Empire to

Crimea via the Right Arm, to Vienna over Belgrade via the Center Arm and to

Athens over Thessaloniki via the Left Arm. Thanks to the road system developed

by the Ottomans in Rumelia, both the cities were supported in economic and

military terms and, thanks to this road system, the end centers were also developed

rapidly. The best example in this regard is that Sarajevo, which was an end center

before, turned into a major trading center with the settlement of population and

still maintains its viability with its three extant covered bazaars and downtown.

The Center Arm which was heavily used in the active trading activities between

the Empire and the Europe during the Ottoman Period and also served as the main

route followed by the army during the expeditions launched from time to time

between Istanbul and Belgrade, was also intensely used by the messengers and

thus both the road and the bases on the road were always kept well-maintained

(Halaçoğlu, 2002; İnalcık, 2010).

3 Ottoman Bridges in Bosnia and Herzegovina

Within the borders of Bosnia and Herzegovina where the majority of Ottoman

bridges in the Balkans are located, only a total of 100 bridges, 32 of which are

non-extant today, have been duly identified so far although a total of 121 historical

bridges were reported to exist there before. Therefore, it would be reasonable to

attribute the main reason why those bridges were so destroyed to the fact that the

bridges in the region were blasted during the World War I, II as well as the Civil

War in the region between the years 1992 and 1995. Among these bridges located

in the Bosnia and Herzegovina are also the bridges built by Mimar Sinan which

marked the Classical Ottoman Architecture during the 16th

century. After being

appointed as the "Imperial Chief Architect", "Sinan the Architect" played a

leading role in the design and application of the architectural masterpieces

symbolizing the power of the Empire and built a total of 9 bridges within the

borders of Turkey and 3 bridges outside our borders (Bektaş, C.,1968).This paper

reports the restoration project and application studies carried out on the historical

Mehmed Pasha Sokolovic Bridge over the river Drina which is located on the

route providing access to the Adriatic Sea over Sarajevo and Dubrovnik by

departing, in Nis and Constanta, from the middle route connecting Istanbul to

Belgrade and reached today thanks to the repairs performed on it in different

periods despite particularly the devastating effects caused by wars.

3

4 Historical Mehmed Pasha Sokolovic Bridge

4.1 Location, History and Architectural Features of the Bridge

Crossing over the river Drina in the city center of Visegrad within the borders

of Republika Srpska/Bosnia and Herzegovina, the bridge is 1070 km far from

Istanbul and 130 km from the capital, Sarajevo (Figure 1). The bridge was built by

Mimar Sinan, the Imperial Chief Architect, between the years 1571 and 1577 at

the behest of the grand vizier Mehmet Pasha Sokolovic who was born in the

village of Sokolovic (Sokol) near Visegrad. According to foundation charter of

1574: “The founder of the Foundation (Mehmet Pasha, Sokolovic, son of the

martyr Sinan Bey) has had a high and twelve-arched stone bridge built over the

river known as Drin (Drina) beside the town of Veşgırad (Visegrad) in the

starboard of Bosnia in Rumelia and devoted it to the passers-bys', passengers' and

other people's service… Also, in order to preserve the bridge and other charity

works, the endower has devoted a great deal of real properties for bringing in

money and ensuring their repair and maintenance; in return for this, may the name

of the endower be remembered with gratitude by people and all these good deeds

done by the endower be written in the books of deeds forever….” [VGM (General

Directorate of Foundations) Archive, Reg. No: 572].

Figure 1. Mehmed Pasha Sokolovic Bridge over the river Drina.

The L-shaped bridge has a total length of 228,60 m, including 179,40 m over

the river bed and 49,20 m as the ascending ramp, and a total width of 7,25 m. The

bridge which has a total of 12 arches, including 11 under the part crossing over the

river and 1 under the ascending & descending ramp, has 3 more arches under its

part where the ramp is connected to the road. The abutments (flood splitters) were

built in a triangular form in the upstream side and of in a circular form in the

downstream side. The sofa is located opposite the richly decorated stela situated

Downstream, 2007

Sarajevo

Istanbul

4

on the abutment A6 in the upstream side and there, there are two inscriptions on

the construction of the bridge stating that the bridge was built at the behest of

Mehmed Pasha Sokolovic between 1571 and 1577.

On the spandrel walls, there are niches and palmettes and a rosette on the

spandrel wall situated on the bending side of the bridge. What put the bridge on

the map today is the novel 'The Bridge on the Drina' which describes, by the

testimony of the bridge, the last 350 years of the relationship between different

ethnic cultures living in the region and brought the Nobel Prize in Literature to its

author Ivo Andrić in 1961.

4.2 Pre-Restoration State of the Bridge

With the effect of the dams constructed in the downstream side of the bridge in

1966 and in the upstream side in 1989, the irregularities in the river bed have

gradually increased and the problems in the foundations and abutments of the

bridge have got bigger. After being indicated among the 100 endangered sites in

the world by the "World Monuments Watch" in 2005, the bridge was included in

the World's Cultural Heritage List by UNESCO in 2007. In order for the

elimination of damages on the bridge and the execution of restoration works by

Turkey, a cooperation protocol was signed between TIKA on behalf of Turkey

and the Commission to Preserve National Monuments, the Ministry of Education

and Culture of the Republika Srpska and the Municipality of Visegrad on behalf

of Bosnia and Herzegovina on April 19,.2010. In addition, another protocol was

signed between TIKA and the General Directorate of Highways on March 5, 2008

in terms of the Supervision Services for the Restoration Project and on December

8, 2011 in terms of the Supervision Services for the Restoration Application.

4.3 Restoration Application Projects

Technical Research Studies; Prior to the restoration works, Dzemal Bijedic

University of Mostar carried out technical research studies on the bridge from

2007 to 2008, and in this scope, topographic measurements were made on the

river bed, core samples were collected from (11 points on) the bridge through both

mechanical methods and drilling and thus the geological and geotechnical

investigations describing the bridge's body, foundations and the ground on which

the bridge is located were performed, and, thanks to the original samples, the

physical, chemical and mechanical properties of the new materials to be used in

restoration were identified. In conclusion of these studies, it was seen that the

foundations of 4 abutments situated in the side facing Sarajevo were settled on a

solid rock whereas other abutments were settled on a poor and a very poor rock

and the foundations with a height ranging from 1.30 m to 4.20 m and given the

form of an encasement were constructed on a pine-type wooden grid system

5

1 2 3 4 5

6

7 8 9 10

consisting of 2 or 3 rows. It was determined that the original mortar used in the

abutments other than those numbered A3, A4, A5 and A6 which were

reconstructed between 1949 and 1952 and filled internally with cement mortar

was the lime mortar containing stone chips and powder, and the stone used there

was krečnjak (a limestone as hard as marble) whereas it was sedra (a hollowed-

type limestone) in the abutments, arches, spandrel walls, cornices and parapets.

Measured Drawings; All surfaces of the bridge, the measuring works of

which were started on 18.11.2008, were scanned with laser and a 3-D model of the

bridge was obtained. It was also found out that, due to the changes occurred in the

water level and flow rate of the river Drina following the construction of the

Bajina Bašta Dam in the downstream side of the bridge and the Visegrad Dam in

its upstream side, the river bed profile has undergone some changes in places and

the foundations have substantially come out into the open. As a result of the

structural analyses, it was observed that there occurred significant tensile stresses

in the bridges' foundations which were exposed to both its own weight and

hydraulic loads. As a result of technical researches conducted on the bridge and

the river bed, the bridge's construction system as well as the current status of the

relations between ground-foundation-river were identified and the measured

drawings were prepared in line with these data (Figure 2,3).

Figure 2. Upstream Facade, Measured Drawing

Figure 3. Scouring in the Abutment A3, Perspective View and Structural Analysis

Restitution Projects; In order to identify the bridge's state when it was first

built and the changes it underwent in the time; all historical researches, foundation

certificate-charters, archive data, previous projects, old photographs, engravings

285

.92

A

3

Top encasement level of the Abutment A3: 285,92

Abutment A3

Abutment A3

Top

encasement

level of the

Abutment

A3: 285,92

Thalweg

level of the

Abutment

A3: 283.66

283

,66 Thalweg level of the Abutment A3: 283.66

Hydraulic load analysis of the current status:

Max. tensile strength: 1,05 MPa

6

and traces on the bridge were investigated. Based on the archival studies

conducted in the Prime Minister's Ottoman Archives, it was determined from the

documents dated 1854 and 1865 that the several correspondences were exchanged

for the repair of damage in the bridge's abutments and for requesting an allowance

in this regard, and that the bridge was repaired in 1873, however fully submerged

during the great flood in 1896.

It is also stated by the resources that the inscriptions heavily damaged during

the World War I and brought to the State Museum of Sarajevo in 1928 were

reconstructed by the museum and the same inscriptions completely destroyed

along with the richly decorated stela during the World War II were restored

through repairs in 1949/52 and 1977/79 (Mujezinović, M., 1953). Besides, the

bridges built by Mimar Sinan were typologically analyzed and the bridges built in

Europe in the same century were also examined in this context, and all repairs

undergone by the bridge so far were analyzed in line with the documents and

information obtained as a result of large-scale researches. It was also found out

that the foundations of the bridge which was heavily damaged during the World

War I and II (Figure 4,5) and reconstructed along with its five arches and

abutments, underwent a thorough repair between 1980 and 1982 and a concrete

injection was performed to the foundations of the abutments A5, A6 and A8

(Gojković,M.,1989).

Figure 4. After World War I, 1915. Figure 5. After World War II,1943. Despite some changes resulting from the repairs performed in different

periods, it was observed that the bridge has maintained its original architectural

and structural properties. As a result of the evaluation of all these documents and

information, a restitution project was prepared for the bridge's possible state in the

period when it was first built.

Restoration Application Projects were prepared in accordance with the

principle of minimum intervention on the basis of maintaining the bridge's original

construction system and material properties, uniforming the water flow through

amendments to the river bed and thus improving the bridge’s resistance against

natural conditions and time by individuating the environmental conditions as far

as possible (Figure 6). In this context, it was envisaged to provide a stone support

as a raft foundation in a way to also cover the foundations outcropped, to take out

the secondary elements on the bridge floor, to re-construct the stone cladding, to

repair the damaged parts and the three-arch bridge in the ramp section and to

7

ensure the lighting of the bridge along with landscaping. The Restoration

Application Projects were approved by the General Directorate of Highways and

TIKA on 26.10.2009, by Institute for Protection of Cultural, Historical and

Natural Heritage of Republika Srpska on 07.04.2010 and by the Commission to

Preserve National Monuments of Bosnia and Herzegovina on 17.06.2010. Upon

receipt of the building permit from the Ministry of Landscaping, Construction and

Ecology/Bosnia and Herzegovina, the tender for the Restoration Application

Works was held under the coordinatorship of TIKA in Bosnia and Herzegovina on

December 12, 2012. The Restoration Application Works were actually started on

April 1, 2013 in accordance with the work schedule and with the preparation of

the stones to be used in the stone support as a raft foundation projected to be built

on the riverbed.

Figure 6. Layout Plan and Upstream Facade, Restoration Project.

Mehmed Pasha Sokolovic Bridge

(L:179,40 m)

Three-Arch Bridge

(L:30m)

Linking Road

(L:81m)

Ramp Section

(L:49,20m)

Protected Area’s Boundary

K

8

4.4 Restoration Application Works

Before the restoration works, joint meetings were held with the officials of

Visegrad and Bajina Bašta Dams in the upstream and downstream of the bridge,

and it was aimed to ensure minimum water level from September 1 to October 1

taking into account the electricity generation and ecological balance and to

complete the anticipated works in the riverbed within this period. It was

determined from the topographic surveys of 01.09.2013 on the riverbed and

encasements that scouring in the thalweg line was still continuing, and the

scouring was minimum(1,90 m.) in the upstream side of the abutments A8 and A9

and maximum in the downstream side of the abutments A3, A4, A5 and A6.

Accordingly, the top level of the stone support to be built as a raft foundation was

determined to be 285.92, which is top encasement level of the original abutment

A3. The stone support projected as a raft foundation was built as about 18m long

in the upstream and 24m long in the downstream side and, on the river shore, until

starting point of the solid ground in according with the project levels(Fig 3,7,8).

Figure 7,8 . Constr. of stone support as a raft foundation/Install. of scaffolding.

The earth fill on the cornice level, involving the ramp (49,20 m), linking road

(81 m) and three-arch bridge(30 m), and the sediments amassed by the running

water were carefully scoured, cleaned and subsequently, the remnants of a wall

(12 m) belonging to an ancient road network under the ground of the three-arch

bridge were reached and the necessary revisions were made to the project . Then,

the impaired stones on the spandrel wall's surface were decomposed and then

completed, the stones deviating from the vertical direction were numbered,

removed and then brought to the plummet and used in original places (Fig 6,9,10)

Figure 9,10. Excavation/Decomposition-Removal Works.

Downstream, 2013 Downstream, 2013

A2

A3

A1

A1

9

The fouling on the stone surfaces of the spandrel wall, especially on the

abutments and inside the arches, were removed using a low pressure (1.5 bar)

water and soft plastic brush without damaging the patina and joints (Figure 11).

Figure 11,12. Cleaning Works / Joint Opening and Pointing

In order to fill the structural gaps under the spring line of the arches,

foundations and other sections under the water, a 30% ready-mixed mortar was

added to the original mortar mixture ratio and a low pressure injection was

applied. The damaged and disappeared joints between the original abutments,

arches, spandrel walls, wing walls and parapet stones were renovated using lime-

based mortars prepared in accordance with the original mixture ratio .In 2014, the

non-original cubic stone flooring on the cornice line over the riverbed was

removed and replaced by a flat flooring made of krečnjak stone and this was also

applied on to the bridge's sections over the ramp and the three-arched bridge. In

2015, however, the top levels of the stone support built as a raft foundation on the

riverbed were removed and, after checking their suitability for the project, the

necessary corrections were applied and, following the completion of the remaining

works, the cubic stones dismantled from the bridge deck were used in the parking

lot between the linking road and the main road and in the landscaping works in

Visegrad, and also the lighting system of the bridge was installed.It is planned to

complete, in 2016, the landscaping works in the immediate vicinity of the bridge,

all the planned manufacturing of which was achieved within the Restoration

Application Project, and to put the bridge into service in May 2016 (Fig. 12,13,14)

Figure 13,14. View of the bridge after restoration works.

Downstream, 2016 Downstream, 2016

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5 Conclusion

Having meticulously executed the Project and Application works within the

historical KONJIC Bridge's restoration thanks to the experiences it gained from

technical counseling services given during the reconstruction of the historical

MOSTAR Bridge, our General Directorate takes the same great care to the

Restoration Project and Application works of the historical MEHMED PASHA

SOKOLOVIC BRIDGE. In conclusion, the Bridges ensuring the continuity of the

transportation system by providing a seamless gateway service during the

commerce, communication, pilgrimage, migration and excursion and "bringing the

past to the present" by reflecting the architectural and engineering know-how of

the period will survive thanks to the restoration work carried out by the General

Directorate of Highways despite the destructive effect caused by people and

natural conditions and continue to be useful structures serving the social and

cultural issues.

References

1. Batur, A, Batur, S (1968) Works by Sinan, C. BEKTAŞ, on behalf of Koca Sinan Association,

Sinan Committee (Published by Sinan Committee for the 380th Death Anniversary), Doğuş

Printing House-1567, İstanbul; 63-92.

2 Çulpan, C (1975) Turkish Stone Bridges, Turkish Historical Society Publications, Ankara.

3.Erdoğan,M. (1988) Strategic Importance of the Works by Mimar Sinan within the Military

Bodies of the State, VGM Publications, İstanbul.

4.Gojković, M (1989) Stari kameni mostovi (Old Stone Bridges), Naučna knjiga.

5.Halaçoğlu,Y. (2002) Transport and Communication in the Ottoman Empire, General

Directorate of PTT, Ankara.

6.İnalcik, H. and Ari,B. (2010), Turkish Islamic and Ottoman Urbanism, Proceedings Book of

Turkish World and Cities Board -III, s.57-70, 24-27 May 2010, Astana.

7.KGM (2007) History Highways, Turkish Road Association Publications, Ankara.

8.KGM (2013) Division of Historical Bridges Inventory, KGM Archive, Ankara.

9.KGM, TİKA (2009) Sokollu Mehmet Paşa Bridge Construct. Drawing and Rest., Unpublished

Tech. Report, KGM Archive, Archive Reg. No: BIH / VİSEGRAD / N.86 / RUP-2009, Ankara.

10.Ortayli, İ (2007) Turkey Organizational and Administrative History, Cedit Publica., Ankara.

11. Sert, H et al. (2009) Historical Bridges' Technical Specifications, Legislations, Inventories,

Projects, Maintenance and Repair, KGM Publication No:268, KGM Publishing House, Ankara.

12. Sert, H et al. (2012) Historical Bridges' Technical Specifications, Legislations, Inventories,

Projects, Maintenance and Repair, KGM Publications, KGM Publishing House, Ankara.

13. Sert, H (2012) Restoration Works Conducted on the Ottoman Bridges in BIH, Hist. Mostar,

Mehmed Pasha Sokolovic and Konjic Bridges, Turkish World Engineering, Architecture and

Urban Plann. Conf., Proceed. Book, s.151-168, 15-18 Ekim 2012, Trabzon.

14. Sert, H, (2013), Restoration Project and Application Works Conducted on the historical

Mehmed Pasha Sokolovic Bridge crossing over the river Drina in Bosnia and Herzegovina, 4th

Symposium on Strengthening of Historical Structures and Their Safe Transfer to the Future,

TMMOB Chamber of Civil Engineers, İstanbul Office, İTÜ, İstanbul.

15.VGM Archive, Reg. No: 572.

Note: The unacknowledged photos used in this paper were taken from the archive of the General

Directorate of Highways, Division of Historical Bridges.