Old masonry towers, in all their variety – be it a bell tower, a city tower, clock tower, inhabited residential towers, and/or guard/watchtowers – can be found all around the world representing typical urban centre feature, and in some cases –they are the countryside panorama landmark. Statics analysis and calculation are the first steps towards engineering interventions on cultural and historical heritage buildings. In the structural analysis of clock towers, the typical critical points and places where crucial damages that could lead to the collapse, are expected are in the top sections of the building - where the oscillation amplitude reaches its maximal value. Effect on building structure is observed concerning the oscillation frequency and building’s own frequency and energy, which can explain why minaret towers and high slim towers, in some cases, can better withstand earthquakes than extremely rigid buildings; given that the resonance, low-quality materials and other factors can lead to the vulnerability of a building structure. This type of building is designed on a simple, regular shape ground plan, or, in other words, the towers have a symmetrical ground plan and uniformly distributed mass and height. The second statement provides that, depending on building materials used and the cross-section dimensions, towers can be very heavy, which can cause the appearance of significant inertia forces during earthquake oscillations. If there’s mass eccentricity, the horizontal loads could tip the building over. Gradačac clock tower’s load-bearing structural walls are built with masonry stone blocks. The vertical loads are, via slabs and wooden beams, conducted to the walls and down to the foundations. Foundation structure consists of a slab, 80cm thick, positioned at -8.25m which sits on a well-compacted layer of soil. Wooden staircases are used for vertical transportation between storeys. Structural analysis calculation is based on a 3D model of a building and is performed by using the finite elements method (FEM) in Tower calculation software. The requirements for the authenticity in preservation actions imply that the interpretation and the presentation must correlate with basic authenticity principles, in compliance to Nara document (ICOMOS, 1994), protecting cultural values, from both – the hazardous influences of intrusive infrastructure and load of visitors, and incorrect and inappropriate interpretations.

In the protection of historical heritage evaluating the current state of a facility is a very important phase since it provides for the project framework and the decision-making guidelines, which is all crucial for the final goal – protection of Gradačac Old Town complex. There are several historical layers encompassed by Gradačac Old Town - starting from the medieval fortification system, expanding to the Ottomans’ period where main buildings (a residential tower, a clock tower, and a mosque) were added by the Ottomans, extending and continuing the works on adding a library and a gymnasium in the Austro-Hungarian period. The overall Complex flows with the natural morphology of the terrain; nowadays these green areas are used as the main city park. Complex of Gradačac has two separate fortification zones, the main area of around 33 000 m2, and the accentuated part with the tower, of around 3 000 m2. The fortification (The Old Town) ground plan is approximately a square one, with sides from 180 to 200 m, consisting of the two main parts: The Lower and the Upper City. In the north-west area, there’s the Upper City (fortification inside the fortification, namely Husein-Captain Gradaščević’s Tower). The Old Town is accessed through three gates: The North (the main gate), the South, and the West gate. Upper City with Husein-Captain Gradaščević’s tower is positioned on the topmost point in the north side of the fortification complex. It rests on a terrace which encloses it from the south and the east side. On the north side of the Upper City, there are outer perimeter walls constituent to the whole of the Complex. Architectural heritage preservation and valorisation are increasingly important social and economic issue in many countries. The issues encountered in these undertakings range from defining and choosing required level of safety, via the question of electing methodologies relevant for contracting reliable structural analyses and safety check-ups, up to choosing the design and installation of suitable materials, and the intervention.

The unexpected loss of values, as one result of the total destruction during the armed conflicts and war, put us on the challenge to properly decide about methods of rehabilitation, and integrating and understanding values and actions that could vary from restoration to, in many cases, even full reconstruction. During the 1992-1995 war in BiH, many valuable assets of cultural heritage like national monuments, historical places, and historical structures were damaged and/or destroyed. After the aggression, the first step has been to regain and/or establish the function of the places destroyed, while for the cultural heritage assets these attempts called for the approaches more careful. It is not only that the importance or the significance of places and structures destructed is different, the level of destruction also is. These inputs are essential in having preparedness for any action when without possibilities to rely on unique methodology. Even though it is now 20 years after the conflict, Bosnia is still faced with the post-war recovery efforts, with problems newly occurred that are the outcomes of unsuccessfully implemented methods of rehabilitation. This paper aims to present an overview of the interventions implemented within Bosnia and Herzegovina given in respect to the typology of a building, its importance including intangible values and the level of its destruction. Giving examples of Ferhadija/Ferhat Pasha Mosque in Banja Luka and the Old Bridge in Mostar – the examples of total reconstruction, will guide one to understand aspects of choosing the reconstruction action as the appropriate intervention. There are also valuable examples of post-war recovery and rehabilitation for the historical places, such as is the Old town of Počitelj with its entire valuable structures, where after the urban reconstruction – we now have the new challenge of managing the historic place. The inside view shall be more oriented on the case of the Handanija Mosque in Prusac where correct methodology approach had been applied regarding the diagnostic, identifying and/or determining the nature and causes of damage and deterioration of the facility through the inspection and examination, but some rather improper conclusion and decision have been derived from that investigation works. In addition, some analyses of Index of shifts of minaret have been conducted too. Index of shift represents the relation of minaret height – h and width of its layout (D or 2r) or the diameter of circular cross-section. Analyses of conducted work could provide us with a better understanding of the damaged buildings potential weaknesses and weak spots. Reinforcement and strengthening of damaged construction structure has been among the most important tasks. In some cases, improper interventions on heritage structures may have been damaging - in sense of impairing the authenticity, while sometimes it was an insufficient knowledge on structural behaviour and the materials used in historic structures that brought unexpected additional damages. The use of traditional crafts, techniques, and materials is one of the most important elements in the process of architectural heritage protection, contributing to the adequate protection, restoration, conservation, as well as its maintenance.

Nowadays, masonry heritage buildings usually experience changes during exploitation. In areas of emphasized seismic risk, in cases of extensions, alterations to the original dimensions, reconstruction (the removal of bearing elements, replacement of materials, introduction of new fittings), or the subsequent erection of properties close by, with a comparison of the foundation levels change of use, refurbishment, extension, or additional building to an existing building. It is necessary to analyze the seismic aspect of such interventions in seismic prone areas. At first, we’ll focus on the legal and technical regulations. For start we’ll look back at UNESCO’s Program on Masonry Heritage, then domestic and regional legal and technical regulations and with all of that we will define the first step of the process. Next step would be a detailed registration of the current condition of the building, and also determining the characteristics of the embedded materials. The load bearing structures of the building must also be accurately identified, with all relevant measurements and, in particular, a description of the building materials and their condition. This includes all detailed maps, plans, and details of the used materials, and especially detailed record of all the damages on the structure. Even at this early stage of investigative works it may prove necessary to secure certain structural elements, or even the entire building, to prevent it from collapsing. As a rule, this requires not only the removal of the outer cladding or even of parts of a wall to determine the depth of cracks but also, if there is any suggestion of subsidence, excavations around the building or to the depth of the foundations. Calculations, based on the planned and current condition of the building, will show whether the strengthening and rehabilitation are needed for the structure. The elements that need reinforcement or conservation can be identified during the initial visit, and provision can immediately be made to take the necessary steps to relieve the load. It is necessary to do all the steps regarding technical regulations, legal regulations, methods of approach, theoretical consideration, methods of calculation, and in the end to determine the needs of that building. Theoretical consideration regarding the determined condition of structure, from all the above aspects, is the next step to be done. This also includes evaluation of the viability of these interventions, based on experience. The most sensitive issue, without doubt, is determining the condition of the foundations. This should be addressed with the utmost care with the general opinion of the building’s stability in mind.

Life cycle assessment (LCA) is defined as decision making method for buildings from “cradle to grave”. Considering the fact that the construction industry produces 38% of total waste and 40% of total CO2 emissions and uses 50% of all natural resources, according to EIB 2015, the building industry has to change this way of thinking to the concept “cradle to cradle”. According to European Commission (Directive 2008/98/EC 2008), the first and preferred option is waste prevention and the second option are other types of recovery. The waste should be prevented in the design phase and LCA should help a lot in this stage. The main goal of this paper is to show how the LCA can be used as a tool in design phase to help decision process in building design of one of the building systems and make that part circular and, if possible, without waste. External wall, as one of the systems of a building, is taken as case study in its different materialization to show LCA use in the construction waste elimination in building practice. The external wall is the system of a building which is the most exposed to external factors, as weather conditions and human. Very often, the wall is damaged before other systems of a building. Hence the design and building of external walls that produce less waste, is a huge step in construction waste management. The LCA software is used to compare two chosen case studies. The first one is prefabricated wooden wall for low energy houses. The second one is the wooden wall made for Green Design Centre in Mostar in 2018. The first results show that in the second case study, the wall made for reversible and transformable building, and designed according to circular building principles, has better chances to last longer, and produce less waste during its transformations and aging. The paper shows main principles for designing the low waste wooden walls and also some remarks how to upgrade the software to be more helpful in the design phase of the wall systems.

The paper deals with selected examples of clock towers in Bosnia and Herzegovina, representing high masonry heritage buildings made of stone, and explains the approach used in their preservation and restoration. The aim of this paper is to present a specific method of conservation used on stone structures. Three clock towers from Bosnia and Herzegovina were selected as representative examples: Sarajevo Clock Tower from the 16th century is an example of well-preserved building; The Clock Tower in Gradačac, the youngest building of this type in Bosnia and Herzegovina, is in poor structural conditions and in danger of collapsing; The Clock Tower in Banja Luka, the first clock tower in Bosnia and Herzegovina, was demolished in 1993 but the reconstruction project is planned for the current year. This paper addresses the structural properties of masonry clock tower from the Ottoman period, with special attention to preservation, analysis and strengthening. These tasks are still a challenge for masonry practitioners even if significant advances in research have been made in the last decades. The dynamic behavior of the historical buildings is usually analyzed to design repair intervention solutions and retrofitting. The structural behavior is analyzed using FEM modeling to examine how far the structural defects endanger the stability of the tower. The soil properties problem under the tower has been considered. Simplified yet effective procedures have been used as well. Results of the analysis have confirmed insufficient performance of the structure under horizontal action and the need for improvement.

In a post conflict zone, restoration of monuments is not only a scientific or technical matter but also a highly symbolic and emotional act of reclaiming culture, identity and urban form. In Bosnia and Herzegovina minarets are shaped by local building traditions and materials, influenced by the ottoman classical minaret format. Most of the prominent mosques have stone minarets, especially in regions abundant with suitable stone and craftsmanship. Wooden minarets were usually built alongside local neighbourhood mosques and they defined city image due to their frequent occurrence in most parts of the urban core. Restoration of these two types of minarets is significantly different mainly due to the nature of the material itself. Interventions on stone minarets were carried out through reconstruction and re-composition of elements, based on documentation about the structure. Stone remains were actually the prime source of information for geometry and breadth of the minaret body and for the complex structural considerations – mainly how to counteract the tension forces. Restoration of wooden minarets had its own challenges, due to the fact that after a major destruction its parts could not be reused and there was less available documentation about the original state. The paper will consider different parameters and make a comparative analysis on both typologies, from materials, structure, aspects of intervention and their subsequent role in restoring the historic urban landscape.

The architecture initiated during the time of the Austro-Hungarian period was distinctly expressed both in Sarajevo and in the whole region of Bosnia-Herzegovina. A substantial number of these buildings was assessed for their historical, architectural, ambient and aesthetical values and, as such, represent the valuable historic heritage of these regions. Standing among them in its impressive dimension and being of a great national value is the palace of the former Provincial Government, which was designed by Josip Vancaš in Vienna (1884). The aim of the present paper is to emphasize the importance of atrial and open spaces integrated into the volume of the building. These spaces can be used to synthesize and functionally transform spaces into controlled and contextually selected forms, contemporary shapes and materials by applying functional creativity without endangering the ambience and historical values of the building. On the contrary, by closing the courtyard and atrial spaces, it would be possible to ensure a buffer zone between the interior and the exterior as well as to create a micro-climate and eliminate processes that generally occur in façades facing such spaces. These spaces could be synthesized and functionally transformed into useable, controlled and contextually selected forms by creatively applying contemporary shapes and materials without endangering the ambiance and historic values of the building. The view towards the sky through a diagonal lattice would present an association to the “lattice window” or “mušebak”, creating a comfortable microclimate. Several different structural concepts were studied. The aim of the paper was to evaluate structural concepts in terms of feasibility and energy efficiency measures pay off. There are numerous examples of transparent roof extensions introduced when rehabilitating the existing cultural-historical buildings, the extensions known for their power in terms of quality and quantity or the harmonious bond between the old and the new. The atrium roof structure will be supported on the walls of existing building. Since the roof structure would be on the interior of the building footprint it is important to consider manageable erection process.

Traditional art of building in Bosnia and Herzegovina comprises brick or stone masonry structures. Most historical buildings belonging to national cultural heritage were made of stone-masonry. The country is situated in seismic active region of South-East Europe. In the case of strong earthquake motion such buildings could suffer heavy damages. Some structural elements of historical buildings, as domes and arches, cracked already by moderate earthquake but without the loss of stability. Substantial damages were caused by recent war disaster. Damages could be accumulated through the history as well. Generally, stone-masonry buildings in Bosnia and Herzegovina can be classified in vulnerability classes between A and C according to European Macroseismic Scale. Design and construction procedures for rehabilitation are presented here with examples of repair and strengthening of mosques, which present historical stone masonry structures dating from the Ottoman period in Bosnia and Herzegovina. Traditional and contemporary materials were used for their rehabilitation. It is important to preserve original forms, especially those of damaged elements. The challenge for structural engineers and architects was to find equilibrium between aesthetical and structural demands.

Among other pieces of architectural historical heritage in Sarajevo, and Bosnia-Herzegovina in general, the Austro-Hungarian architecture has preserved its original architectural, artistic and engineering characteristics. Both residential and public representative urban blocks, streets and squares are of distinguishable ambience in the architectural and urban image of the city and are testifying about our architectural past. A number of buildings is valorised and protected by law in terms of their architectural, artistic and historical value. In addition, these buildings have a distinct functional, ambiental, historical, and even aesthetical value. To make them last longer, refurbishment of these buildings is challenging and presents potential and multiple benefits for the city, and beyond. Refurbishing built environment through functional reorganizing, redesign and energy efficiency measures applications could result in prolonged longevity, architectural identity preservation and interior comfort improvement. Besides, implemented measures for energy efficiency, through the refurbishment process, should optimize the needs for energy consumption in treated buildings. This paper defines options in comfort improvements and redesign, without implying risks to the building longevity, analyses interventions and energy efficiency measures which would enable potential energy saving assessment in the refurbishment process of masonry buildings. This paper also discusses the different techniques that can be adopted for conservation and preservation of historical masonry buildings from the Austro-Hungarian period dealing with energy efficiency. The works were preceded by historical research and on-site investigations. This paper describes a methodology to quantify their vulnerability. A scheme of structural retrofitting is suggested following the research conducted. Revitalization of the building consisted in the reconstruction of the old building structure, creating the inner courtyard and covering it with a glass roof.