Unreinforced unconfined solid brick masonry walls were experimentally tested in full scale (233x241x25cm) and reduced scale (100x100x25cm) at the laboratory of the Institute for materials and structures, Faculty of Civil Engineering in Sarajevo. Cantilever walls were loaded in cyclic shear or pushed monotonically. In order to study the nonlinear behavior in a detailed and global manner, finite element mesoand macro-models of the tested walls were created using finite element software Diana 10.1. Brick units are discretized by continuum elements in a meso-model and discontinuity in displacement field is introduced by interface elements between units. In order to account for brick cracking, an additional interface element was added in the unit middle. Continuum macro-models approximate heterogeneous masonry wall by a single material and discretization is independent of brick layout, i.e. bricks, mortar and unit-mortar interface are smeared out in the continuum. Recently developed engineering masonry model is an orthotropic total-strain continuum model with smeared cracking and it was used with shell elements. Numerical results are verified against the data obtained from experimental research program. In case of low precompression, the walls exhibit rocking failure mode while for higher vertical stresses diagonal cracking occurs. The results show good matching with the experimentally obtained curves regarding the ultimate load and ductility. Macro-modeling approach was also employed for analysis of an existing masonry house in Sarajevo.

Unreinforced masonry structures are generally vulnerable to earthquake actions. Brittle masonry walls are very stiff and attract considerable seismic forces which cannot be sustained without cracking. In order to enhance ductility and load bearing capacity, certain strengthening techniques need to be applied. An experimental program concerning in-plane behavior of solid clay brick masonry walls was performed at the Institute for Materials and Structures, Faculty of Civil Engineering University of Sarajevo, in cooperation with Institute for Lightweight Structures and Conceptual Design, University of Stuttgart. The physical models include two unconfined unreinforced full scale masonry walls L/H/D=233/237/25cm and two strengthened full scale walls jacketed on both sides with 5cm thick concrete and reinforced with Q196 steel mesh. Twelve reduced scale walls L/H/D = 100/100/25cm were additionally constructed in order to test different strengthening methods which include one-or two-sided jacketing and CFK 150 strips. Specimens were exposed to cyclic shear as well as to monotonic push over loading program for different vertical stress levels with the aim to quantify shear strength, stiffness and energy dissipation. For lower vertical loads the tested walls exhibit rigid body rotation in each displacement cycle. For higher precompression mixed flexural and shear failure mode was registered, characterized by toe crushing and diagonal cracking. No separation of jacketing from the masonry was detected. Numerical models of tested wall panels were developed using finite element programs.

A seismic assessment of a typical unreinforced masonry residential building without tie beams is presented in the paper. The numerical analysis was conducted according to the finite-element method using experimental data on the quality of the masonry constitutive elements and reinforced concrete. The computation was made using the nonlinear static pushover analysis and nonlinear dynamic time history analysis. The crack development pattern was compared for the procedures, as well as parts of the hysteresis curves.

In this paper some experimental and numerical results pertaining to unreinforced masonry walls and its components are presented. This is the first phase of the joint project to be implemented by the Faculty of Civil Engineering, University of Sarajevo and the Institute for Lightweight Structures and Conceptual Design, University of Stuttgart. Testing methods for solid clay brick, lime-cement mortar, wallet compressive and shear strength and elastic modulus follow national standards and European norms. Full scale tests of the unreinforced masonry walls were conducted at the Institute for Materials and Structures, Faculty of Civil Engineering in Sarajevo. Numerical modelling concerns prism compression test and full scale masonry wall exposed to vertical and horizontal forces. Snap-back instabilities due to brick-mortar mechanical and geometrical mismatch are tackled as well. In the second phase it is planned to apply several strengthening methods and to compare the wall behaviour with the unreinforced one. The main goal of the research project is to investigate the influence of the different strengthening methods on the structural behaviour of originally unconfined masonry walls under cyclic horizontal loading.

The paper discussed the behaviour of a typical multi-storey masonry residential building in Sarajevo as part of the massive construction during the 50's and 60's in the Western Balkans. It is noted that these kinds of buildings have been designed without utilizing any seismic codes. Structural walls are located mainly in one direction. As, such buildings represent a large portion of residential unreinforced masonry building stock in a wider region, which most probably do not satisfy the latest code provisions, this leads to the necessity for investigation of their seismic vulnerability. Global numerical models of the building taking into account nonlinear material characteristics have been created. Time History Analysis was done in Finite Element Method (FEM) program, while Pushover Analysis was done in Equivalent Frame Model (EFM) as well. Several comparisons were done and results were found to be in a very good correlation. The paper's aim was to assess the seismic safety of this type of structure. As the building showed inadequate behaviour in X-direction strengthening proposals have been made.

The paper discusses the behavior of a typical masonry building in Bosnia and Herzegovina built in the 50’s without any seismic guidelines. A global numerical model of the building has been built and masonry material has been simulated as nonlinear. Additionally, calculations done with a "less" sophisticated model are in a good correlation with the finite element method (FEM) calculations. It was able to "grasp" the damage pattern; not as detailed as in the FEM calculations, but still quite good. On the basis of this it may be concluded that in this case calculation with Frame by Macro Elements (FME) program could be recommended for future analysis of this type of structures, having quite good results with a less computation time. However, in the need for more precise results FEM should be utilized. Key-words —: masonry, nonlinear analysis, B&H residential masonry buildings, pushover, finite element method, equivalent frame method Pushover Analysis and Failure Pattern of a Typical Masonry Residential Building in Bosnia and Herzegovina

Bosnia Herzegovina is situated in a seismically active region of south-eastern Europe where peak ground accelerations could reach 0.30-0.35 g. Robust and durable stone masonry buildings, which constitute an important part of cultural heritage, can be very vulnerable to earthquake motion. Design and construction procedures for rehabilitation and strengthening of two mosques dating from the Ottoman period are presented. The analyzed structures were heavily damaged in the 1969 earthquake, renovated afterwards and then completely blasted in 1993 during war time. Traditional and contemporary materials were used for retrofit of all bearing elements comprising domes, drums, squinches, pendentives, arches, walls, minarets and foundations. In the course of reconstruction, special attention was paid to seismic requirements of slender minarets susceptible to lateral loads. Static and response spectrum analysis were performed using beam, solid and shell finite elements. The challenge for structural engineer was to find equilibrium between aesthetical and structural demands. .

Bosnia and Herzegovina is situated in seismic active region of South-East Europe, divided in seismic zones with peak ground acceleration of 0.1–0.2 g for 500 years return period, even PGA of 0.30-0.35 g in some parts. Traditional art of building comprises masonry structures. Most historical buildings belonging to the national cultural heritage were made of stone-masonry with robust and enduring structure. In the case of stronger earthquake motion such buildings could suffer substantial or heavy damages. Some structural elements of historical buildings, as domes and arches, crack already by moderate earthquake but without the loss of stability. Stone-masonry buildings in Bosnia and Herzegovina can be classified in vulnerability classes B and C according to European Macro-seismic Scale, where A stands for the weakest seismic structures and F for those expected to have best seismic performance. Design and construction procedures for rehabilitation are presented here on examples of repair and strengthening of mosques situated in three different seismic regions. These mosques are historical stone masonry structures dating from the Ottoman period in Bosnia and Herzegovina. Traditional and contemporary materials were used for their rehabilitation. The challenge for structural engineers was to find equilibrium between aesthetical and structural demands considering seismic codes as well.

There are a number of old buildings constructed of plain masonry with timber floors located in Sarajevo and elsewhere in Bosnia and Herzegovina. The building where the Embassy of the Republic of Turkey to Bosnia and Herzegovina is currently located is one of them. Due to its historic value, this building has been added to a list of sites that are under the protection of the Cultural and Historic Heritage of the City of Sarajevo. After the 31 March 2009 earthquake cracks were noticed on the load-bearing structure. Damages were assessed utilizing the damage index and vulnerability classification, as well as by defining the level of individual walls. Damages that occurred to the structure are identified; causes for the damage and recommendations for rehabilitation are given in this paper.