English

Either in the Phase A report (see §1.3), either in the Inception Report (see §1.4), the issue of the ancient stones was accurately examined and it was worked out the most desirable solution for this issue but at the same time many limits were raised: "[…] These stones, first of all, represent an important documentation of the ancient and refined technique used at the time for voussoirs assembling, they moreover have an historical value to be preserved since they are the original ancient stones and unique left portions of the destroyed monument. The future use of these stones is, therefore, very much delicate and should be carefully analysed to avoid any reduction of their importance and value.

One of the most desirable destination of the former Bridge stones is to reuse them in the rehabilitated Bridge of Mostar, positioning them in their original location and in the exact condition as they are at the moment (or at least after an accurate cleaning of the surfaces). The above hypothesis may be also confirmed by the following notes:

• the first PCU's objective of the present work is to rebuild "a structure identical to the one prior to destruction" (or at least as much close as possible)
• any other location of the stones, different to the original one in the bridge, would be arbitrary
• reuse of ancient stones would very much valorise them
• the rehabilitated Bridge of Mostar could assume a stronger historical value and stronger symbolic meaning

Although this would probably be among the most desirable solutions for what concern this issue, there are, also in the present case, some limits, difficulties and technical impediments that may force us to choose either a completely different solution, either a compromise.

The most important thing is that anything worked out could be the result of a demonstrated and accurate analysis of the possible solutions and that all the technical impediments were evaluated and verified. […]".

All the above has been subsequently confirmed, and limits to stone reuse appeared to be too many and too wide even when results of the laboratory tests were not yet available. Moreover technical and practical limits compelled to unacceptable compromises and were leading to a difficult position in the objectives of the whole design which was not compatible with the internationals codes of restoration.

The analysis of the limits for the ancient stones reuse was already introduced in the Inception report (see §1.4.1 and §1.4.2) and prosecuted in the Phase A report (see §1.3.1): here below it is reported to explain final evaluation and conclusion on the matter.

Technical and practical limits are here listed and analysed:

• limits due to "quantity" of the recovered stones
• limits due to "quality" of the recovered stones
• limits due to the determination of the position
• limits due to the assembled blocks of ancient stones

About quantity it has been noted that, unlikely, the amount of the recovered stones is not pretty much compared to the global size of the bridge. For the load bearing arch of the bridge a punctual evaluation of this matter may be introduced: all the voussoirs from the geometry analysis count 456 arch stones while from the analysis of the recovered stones we have only 162 stones on the platform. The percentage has been estimated around 36% of the total amount plus the built-in stones next to the abutments and minus all the broken ones, (refer to §4.3.6 of this report for detailed evaluations). For the other bridge elements we have 24 cornices, 44 ashlars coming from the spandrels, and 19 parapets elements.

On the other side it has to be underlined that the most important stones were the worked ones, placed on the arch, on the intrados, on the external elevations and on the walk path, while the loss of small stones, used as bridge fill, is of less importance.

Anyway, being the ancient stones not many, the reuse and repositioning operation would loose a part of its value and, being the lacks too wide, the recomposing work would be lacks-full (refer to §4.3.7 of this report).

About quality of the recovered stones it can be said that the bad condition in which these masonry elements have been kept for years, (especially underneath water), may have corrupted their characteristics, and above all, their resistance to any compressive stress, even if, this doesn't seems to be a problem, following the laboratory test results; nevertheless the shooting and the final collapse event may have caused, in some of them, damages like internal cracks (as confirmed by laboratory tests). Moreover some of the recovered stones look like they have been bevelled by the water of the river or by fractures of the perimeter portions specially on the edges and on the corners.

All the underlined problems of quality, being confirmed, reduce the number of usable stones, increasing, this way, the mentioned problem of "quantity".

Original position of stones is also an important limit for the right performing of this step, until now it is available a detailed identification book but there isn't any positioning scheme of stones, And if all the pictures of the former Bridge are only the ones till now received, it may result very difficult to perform this task to the company that will get the assignment.

Without knowing the exact positions of the recovered stones, the reuse of the ruined portions of the bridge gets a different meaning: it is not anymore a matter of reassembling broken masonry but it is a matter of using ancient stones instead of new quarried ones.

Another limit to be considered is the one of the big blocks composed by many stones which have been partially recovered, and one of which is still underneath water. These blocks actually weights many tons and, in case one wanted to reuse them in the rehabilitated Bridge of Mostar, different difficulties would arise like the ones here next listed:

• to put on site the blocks as they are (as a whole) it would be necessary a very powerful crane.
• so big weights being put at once on one side may cause the instability of the load bearing vault during construction
• resistance and behaviour of assembled blocks would be different from the rest of the structure causing calculations model problems and difficult evaluation of future resistance of the whole structure
• assembled blocks of stone would be linked with the ancient cramps and dowels that may be corrupted after being for so long on the riverbed

It has been thought that a possible device to face this limit could be to disassemble the stones of each big block by numbering and surveying the position of each voussoir, and to remount the examined portion on site using new cramps and dowels. But this is not an easy task, since stones are often linked to the adjacent ones by cramps and dowels and working either with a saw, either with sawing wires, it seems difficult to dismantle them without any damage. Moreover by dismantling the blocks we might loose part of their historical value and the original models of the strengthening technique used at the time.

Among the most remarkable philosophical or conceptual limits there is the fact that a recomposing work with little use of ancient original elements is opposite to the methodology followed in these cases: usually reconstruction is not part of the restoration procedures at all, and nowadays we talk only about "preservation" and about the techniques to make historical monuments last as much as possible during time. Only exceptionally, and only when documentation is wide enough it may be possible to make recomposing operations of very small portions trough the use of the so called anastilosis technique.

Another limit is represented by the position of the former bridge stones: if this can not be established with accuracy, then the anastilosis technique may be not performed, and it would be an huge conceptual mistake settling the original stones in wrong or random locations. This would irreversibly compromise either the value of the ancient stones, either the value of the rehabilitated bridge. This would be moreover the worst way to face the problems of the lack of lime stones coming from the quarry from which the blocks of the bridge were originally taken.

The recovered stones of the ancient bridge will have to be respected and preserved as single ones, and as assembled groups, this because they still are the real "Old Bridge of Mostar", they are what remains of an ancient refined constructive technique: they show us traces of the stone cutting technique and of the assembling technique trough the use of cramps and dowels. This way they are an important historical document that will be left intact for future generations and for future studies.

As already pointed out, the reuse of the former bridge stones has been a very delicate step because it is strictly linked to the objectives of the whole intervention in the Monumental Complex of the Stari Most. Moreover we do not have many similar case to which we can refer to in our recent history, also because the restoration ideals have recently developed towards more mature positions, and because past interventions generally may be not taken as a good examples for this type of situations. Besides an architectonic complex, being composed by simple stones, is generally considered not as precious as other art manufactures and it is usually manipulated with no respect and attention, making also conceptual mistakes.

But just let’s think for a while that we do not have a bridge to work on, but a vase, an ancient and precious vase: this vase has been broken into pieces. Of course the ruined portions of the ancient vase still have a great historical value, not as much as the whole vase, but they are precious anyway. If the broken portions are almost the total amount of the vase, it could be a good thing, (if we have a wide documentation like pictures or surveys), to remount all the pieces in the original position, maybe it would be also accepted if we use special reinforcement or internal structures to put everything in the original location. For the lacks some different material or colour may be adopted, like a neuter texture to denounce immediately that something has been lost and it is not original.

But, in the case that only small portions of the vase are left, things would be a little different, it wouldn’t be the most desirable solution to make a new white and neuter vase putting on it the small left portions, maybe this ruined parts would be better settled on a little pedestal or on a steel structure, always on the original location (if known).

Anyhow, concerning the above example, it is obvious that a recomposed vase with the original portions, settled in locations different to the original ones or manipulated (repainted or bevelled) would have no value and would even represent an irreversible damage to the left portions. It is also obvious that, a new vase, perfectly alike to the original one, will have no value unless it is exposed next to the original portions with the aim of documenting how it was the original ancient vase and declaring that the new one has been worked out after studies and analysis on pictures, documentation and surveys.

For the Old Bridge of Mostar we should operate as if it were an ancient precious object like the mentioned example: if we had a large quantity of the original stones (compared to the global structure) it would be possible to plan or to try a recomposing work (following the anastilosis technique, and making clear differences for the lacks), but having, instead, a few recovered stones, we are compelled to preserve them as they are, settling them in the best position for exhibition and in a place where their long lasting is guaranteed. This is the real Old Bridge of Mostar, or at least what remains of it: history may be not changed and with war something has been lost.

Nevertheless the Old Bridge of Mostar represented to its citizens, to Bosnia, and to the World something more than an historical monument, and during war (and also now that war is over), it has acquired even more importance as the symbol of the revitalisation and rehabilitation of the whole Bosnia. Undoubtedly the Old Bridge of Mostar has got now a value that is at the same time historical, political, social, and moreover constitutes a symbol of national identity. All the above may be not neglected by this design, and for this reason the town of Mostar has required "a structure identical to the former one". The "new old bridge of Mostar" has been planned taking care of all the above mentioned considerations and giving to it a special and new value and purpose: it should represent a declared copy of the original, a study of what the monument was, a documentation reproduced on real scale, and it should be considered a sort of useful integration for a better understanding of the ruins exposed in the city museum. Everybody, this way, will easily accept the existence of a declared copy of the bridge for historical documentation aims and for symbolic and social reasons, knowing that the ruins of the real Old Bridge of Mostar are kept preserved in a safe place and that have not been irreversibly manipulated.

Willing to follow the above indications it is obvious that a big effort has been spent on the researches and studies to reproduce the Old Bridge exactly identical to the original one, using all the available documentation.

Other design strategies wouldn't have easily been conceptually valid as the one here exposed: a "new old bridge", rebuilt with a not significant number of ancient stones, settled in random positions and maybe worked again, cut again, disassembled and recomposed, a bridge like that would be really far from being considered a valuable intervention: the reuse of ancient stones would look more like a saving of money for the stones quarry and, what is even worst, the only historical value left would appear definitely lost forever.

Recovered stones final settlement leads to plan a purpose built museum, where the ruins of the bridge could be partially organised and recomposed in a wire frame structure made of steel. This museum could be not only about the ancient stones, but it could host also all the cultural heritage of the town of Mostar, documents, findings, and any other, plus anything referable to the Monumental Complex of Stari Most: studies, project, the current work and all the documented phases. A museum so settled may be also an attractive pole for tourism and for cultural visits in the scope of a general revitalisation of the town and valorisation of its cultural heritage and, of course, of the Old Bridge.

Even if a design proposal of no reuse of the recovered stones has been explained in the previous paragraphs, other additional analysis should be performed either to have a complete and wide examination of this delicate matter, either for historical studies sake.

To better understand this issue, two inquiries have been held: one concerns a detailed, statistical evaluation of all the bridge stones, and the other is about the original location of all the recovered stones in the shape and in the thickness of the former bridge, trough expertise in digital numerical management.

These matters were clearly not included in General Engineering assignment (as it has been pointed out), and should have been handed to the company before the starting date of the works. PCU and PCU TA have asked General Engineering to perform these works anyway in order to give to the ICE an exhaustive explanation. Of course General Engineering hadn't performed purpose surveys for these special investigations and had always declared that the lack of ancient information and pictures would have brought to huge difficulties (see §1.4.1 pages 23-24 of the Inception Report). So the analysis, here next explained, should be considered as a preliminary stage to be developed in the case that the ICE will ever require to relocate stones in the original position. In that case, of course a new assignment and more starting data would be necessary.

For what concern the survey of each recovered stone we may refer to the work held by Mostar Institute for Preservation of Cultural Heritage – ICHM – (Mr Demirovic'). This work is precious and may be not neglected for the current investigation, although the copy that has been handed to General Engineering, (which seems to be the only one available), is of very scarce quality: pictures are hardly visible and dimensions are not properly represented; moreover photographic images are referred only to one side of the stones, and the cornices which are of two types, (upper and lower) have been classified in only one category. This last mentioned limit has often led to consider cornices as one group only. General Engineering, for the above reasons have been compelled to proceed to an additional unforeseen on site survey.

For what concern instead the bridge stones which are still built-in (next to the abutments) the reference survey is the photogrammetry elaboration that has been held in the development of the Phase A (see §5.2 of this report).

But all the above is not enough: a full classification and detailed scheme is required either to explain these matters, either for other design steps.

The classification and the coding system is here next explained, and this one is related to the bridge stones current condition. For global classification system refer to chapter 2 of this report (all the classification systems are strictly related).

The scheme (current condition) actually splits all the stones (Stari Most Stones) in three main categories: Recovered stones, Lost stones and Built-in Stones (which are the ones still on-site next to the abutments). Subsequently each group is subdivided into four types: arch, bridge, fill and paving: this peculiar division is mostly aimed at the restoration requisites being the load bearing arch a more delicate portion of the other bridge stones. Moreover the bridge arch may be not considered as a north and south sided element, but as whole.

Other tags and codes which are printed in a lighter grey in the scheme may be considered as optional marks that may be specified or not, depending on the analysis; among these there is the subdivision among intact stones, and broken stones which is a very rough and approximate division since it is based on a simple quality observation of stones. Stones that are here defined as intact ones, are apparently in that condition, and may be fractured in the interior portions, but this will be enough for this preliminary evaluation of the matter.

CREDITS:

Intellectual property of this report and of the design drawings is owned by General Engineering s.r.l.

© - General Engineering Workgroup -

SOURCE:

Final Design Report