This thesis tries to enlighten the importance of analysing the hot spot or the structural stress approach on the critical weld points of an element. The study has taken into consideration a hexdecagonal steel lighting pole with a height of 35-40 m. There are considered two types of stresses, nominal and structural ones. The steel lighting poles models are done in Autodesk Inventor Professional. A stress analysis and a fatigue strength assessment based on structural hot-spot stress is presented using finite element analysis. The cumulative damage between the hot-spot and the nominal stress method for the base connection is in considerable difference. Even in the connection of the pole and the floodlight maintenance platform, there is a significative difference. The cumulative damage is directly related to the number of cycles of stress range.
Unreinforced Masonry Buildings (URM) represents the largest part of Albanian existing buildings. These types of structures are mainly built before the 90’ based on template buildings. The vulnerability of Unreinforced Masonry Buildings in seismic areas is now acknowledged and severe damages to collapse is documented by post-earthquake site surveys evaluations reports in seismic prone areas. Due to its location in the Mediterranean seismic belt, previous earthquakes and seismic hazard evaluation of Albania, the need emerges to evaluate the seismic adequacy of existing unreinforced masonry.
The objective of this thesis is to evaluate the seismic performance of unreinforced masonry residential buildings. Five template designs with a varying number of stories are taken into consideration in order to assess a large proportion of building stock in Albania. Finite Element macro-modelling is adopted for the structural modelling of the selected buildings and pushover analysis is conducted to assess the capacity of the buildings by using SAP 2000 software. The evaluation of seismic capability was performed in compliance with ATC-40 report. Performance point could be defined for 2 and 3 story unreinforced masonry building and the brittle behaviour and low ductility point out the need for rehabilitation of unreinforced masonry buildings.
In Albanian construction practice, hollow masonry infill walls are frequently used as non-structural partition walls in reinforced concrete buildings. Due to the modelling difficulty, consideration of infill walls during the design stage is generally omitted. However, observations from the past reconnaissance team reports after earthquakes and past studies showed that these walls may have favourable or unfavourable effects on the overall response of the building capacity.
In this study, the effect of infill walls on earthquake response of reinforced concrete buildings was investigated. For this purpose, two different buildings with different heights were chosen to represent low and mid-rise constructions. Three and five-story buildings were modelled as bare frame and with different orientations of infill walls along the height of the buildings. Modelling of the unreinforced masonry infills walls is simulated by strut model per FEMA 356 guidelines. Time history analyses under a set of twelve ground motions are deployed to study the influence of infill wall effects on the seismic performance of reinforced concrete structures. The parameters that were considered were natural period of vibration, energy dissipation, overturning moments and base shear.
The results indicated that the natural period of vibration decreases from bare frame to the biaxial loading for both structures. Energy dissipation is directly related with the presence of the URM infills from bare frame to biaxial loading. Stability is lost when structures are loaded only in one direction, while it is improved when loading is done in both directions. Regarding base shear and axial load, for both types of structures, there is an increase of these parameters when it refers to the bare frame and biaxial loading
In the last century major earthquakes have occurred in Albania and numerous buildings have suffered different level of damages. Throughout of its history it is observed that many important cities like Shkodra, Durrës, and Vlora have been destroyed due to severe earthquakes. Most of the buildings are designed according to earlier versions of Albanian Codes and several buildings were constructed without code provisions. Considering the fact that Albania is a moderate seismic country which has been hit frequently by the hazardous ground motions, establishes the need to assess the performance of the existing reinforced structures.
The inelastic response of existing reinforce concrete (RC) buildings designed without seismic details is investigated, presenting the results from more than 1200 nonlinear analysis. The seismic performance evaluation is conducted for two buildings, three and seven story residential buildings, which represent the building block in Albania. The overall objective of the current study is to investigate the structural performance of low- and mid-rise RC buildings under seismic loading.
For the purpose of this research, two performance earthquake engineering (PBEE) procedures are utilized: static and dynamic non-linear analysis also known as pushover and time-history analysis. Moreover, a new and modern procedure known as Incremental Dynamic Analysis (IDA) or dynamic pushover analysis, is considered for the seismic assessment of building models. Zeus-NL, a finite element analysis program, and SAP2000 are employed for the numerical analysis phase.
In addition, a methodology is presented for the process and strategies followed up to generate the IDA curves by interpolation, the performance levels and finally the IDA fractiles.
Afterwards, the structural performance under different loading condition is investigated using nonlinear procedures. Results are interpreted based on the code provision followed by FEMA 356. Moreover, capacity/demand ratios are followed to extend the interpretation of the structural behavior. Finally, a comparison between static and dynamic pushover curves is accomplished, in order to find correlation points among those curves. At the end, general conclusions and drawbacks are outlined while recommendation for further studies are suggested.
Historic structures have a significant role in the social and cultural heritage of Kosovo. Many of the old monuments in Kosovo are mosques of Ottoman period, and the construction material used is mostly stone masonry. The majority of those mosques are still functional serving for religious purposes. Due to the aging of the structures, seismic activities, temperature changes, weather conditions, inappropriate maintenance, and lack of studies caused many structural deficiencies. In order to provide a fundamental understanding for the origin and impacts of structural defects, structural assessment of a related case should be done. Since it is required a representative model, Bajrakli Mosque located in western Kosovo is selected as a case study.
The first assessment of the study involves visual inspection of the structure for identifying cracks and other structural deficiencies. During the observations, many cracks are found in structural elements such as domes, pendentives, arches and load bearing walls. One of the causes of the cracks is the stress concentration of the critical regions of the structure.
For a better and detailed understanding of the structural deficiencies, finite element analysis is prepared in SAP2000 for Bajrakli Mosque. During the analysis, structural behavior of the undamaged model is observed through static and dynamic loads.
Finite element analysis provided important data on identifying the critical regions of the structure. The maximum displacement for load combination of self-weight and earthquake load is found in the middle dome and around the arches of the entrance hall with a value of 7.1 mm and 8.0 mm for X and Y direction respectively. Furthermore, the highest stress concentration values are found to be in the small domes of entrance hall, in the openings around the main domes and its connection with arches, and around the openings of the load bearing walls. The output values of the stresses in the roof system exceed the allowable limits defined in the study. The results provided by finite element analysis correspond to the findings from visual inspections.
Albanian building stock is composed of reinforced concrete and masonry buildings. Most of these buildings are designed according to earlier versions of Albanian Seismic Codes (KTP Codes) and some of them were constructed without a definite construction project. Considering these facts and the observations done in Albanian construction industry, presence of structural irregularities is very common in these buildings. Irregularities are weak points in the building which may cause failure of one element or total collapse of the building during an earthquake. Irregularities encountered in Albanian construction practice consist of short column, large and heavy overhangs and soft story. Since Albania is country with moderate seismicity which has been hit many times from earthquakes of different magnitudes establishes the need to study the effect of irregularities. All these irregularities are taken in consideration in this study under lateral loads on low and mid-rise buildings of Albanian construction practice. In order to get the effect of structural irregularities on RC buildings response several numbers of Nonlinear Static (Pushover) analyses are done. The considered frames consist of regular frames, frames with soft story because of higher height and lack of masonry infill walls in ground story or because of the presence of both cases, presence of short column because of semi-infilled bays, overhangs because of presence of balconies, presence of soft story and heavy-overhangs. These irregularities are considered for two types of structures, 3 and 6- story frames representing low and mid-rise buildings respectively. The analyses has been performed by using ETABS and Seismosoft software. Effect of structural irregularities and performance of the considered frames are achieved by using capacity curves of the frames and performance point by considering two different response spectrums, from EC 8 and KTP codes. The results of the analyses indicate that low and mid-rise structures with soft story- two sided overhangs and short column are more vulnerable during earthquakes. Frames with soft story and two sided overhangs showed 266% and 300% lower strength, 120% and 92% lower stiffness than 3 and 6 story reference frames respectively; frames with short column showed 100% and 92% lower stiffness and 140% and 122% lower strength than 3 and 6 story reference frames respectively.
Masonry is one of the most used construction material in Albania. Brick masonry construction reached its peak application during the communist period (1944-1990) where template projects of residential buildings made of masonry load bearing walls were designed according to Albanian Code (KTP) guidelines. The increased seismic activity in the Albanian region in the recent years, pointed out the vulnerability of these structures and made the verification of their seismic resistance a very important topic to consider.
This study highlights the real risk of seismic damage to the template masonry buildings of Albanian building stock. An unreinforced masonry building (URM) and a confined one, built in Tirana in 1960 and 1984, respectively, are selected among the stock and subjected to a seismic performance assessment. Their template designs are good representatives of residential buildings in most of the cities in Albania.
The assessment methodology proposed by the International Council on Monuments and Sites (ICOMOS) is chosen to be followed. The process starts with a site investigation where samples of masonry units are taken from the two case study buildings. Experimental tests are conducted according to ASTM C67–09 regulations, where material properties of masonry units are determined. DIANA v.9.6, a finite element analysis program, is employed for the numerical analysis phase. Both structures are modeled by using the macromodelling approach and the mechanical characteristics of masonry are taken from the experimental test results. The analysis use the extended N2, adopted by Eurocode 8 and FEMA440 capacity spectrum methods to determine the displacement demands of possible earthquake scenarios. A seismic hazard assessment determines the seismic demand using probabilistic and current European code provisions. The seismic demand is then compared to the results of pushover analysis completed using DIANA v.9.6 software. Damage classification is done in accordance with the damage criteria presented by Lagomarsino and Penna. Another criteria based on interstorey drift distribution, presented by Calvi, is used in this study.
The analysis results show that the URM building suffers extensive damage under seismic loads and any intervention to strengthen it could be economically unfeasible. On the other hand, the confined one exhibits higher seismic resistance by indicating moderate damage, thus, any strengthening intervention could be feasible. At the end, several intervention techniques are presented. A post-intervention analysis to highlight the seismic performance improvements are recommended as possible future works.
Keywords: unreinforced masonry, confined masonry, finite element modelling, earthquake performance assessment, repair and strengthening.
Masonry is one of the most commonly used materials not only throughout Albania but also worldwide for the construction of low to mid rise buildings. In Albania, until the end of communist period in 1990’s, masonry buildings continued to be built using template designs. Masonry was used for public and governmental buildings as a low cost construction method for the time. Today these buildings are still in use and main functions are mostly for residential purposes.
Albania is one of the most seismic-prone countries in Balkans. Recent devastating earthquakes in neighboring countries (Italy-2009, Greece-2008 and Turkey-1999) have shown that masonry buildings suffered the maximum damage and accounted for the maximum loss of life. Due to several reasons such as aging, interventions on these buildings made by the people and the older code provisions at that time; these buildings have lower reliability. Therefore it is important to assess the seismic performance of these buildings and based upon this evaluation, techniques should be developed for the strengthening of building stock to resist the potential earthquake damages.
The purpose of this study is to evaluate the seismic performance of residential buildings with selected template designs in Albania considering the nonlinear behavior of masonry. Three residential buildings with template designs were selected to represent an important percentage of residential building stock in Albanian medium seismic regions. Selection of the template designed buildings and their design properties were based on archive survey. Capacity curves of the investigated buildings were determined by pushover analyses conducted in two principal directions. Seismic performance evaluation was carried out in accordance with the FEMA 440 guidelines. The detailed examination of capacity curves and performance evaluation identified the deficiencies.
Evaluation of the capacity curves for the investigated buildings points out that two out of three buildings do not satisfy the required performance levels. Inadequate performance of these buildings makes the development of the effective and affordable rehabilitation techniques essential. The most convenient technique in Albania is the use of additional concrete members. Finally, conclusions are provided and future research needs on the topic are outlined.
In order to design new buildings or retrofit existing ones, the use of the design code with all the seismic requirements and provisions is obliged by law. Here, the seismic provisions differ time by time and code by code. In Albania there are three milestones in the seismic provisions for structural design of the buildings, KTP-63, KTP-78 and KTP-89. In this study, the adequacy of Albanian Design Code of 1989 (KTP-89) is evaluated. The evaluation procedure includes also Eurocode 8 provisions. This serves to make a comparison between several codes in order to achieve a better visual understanding of the differences. To reach this comparison one existing building designed by KTP-89 is taken. This building is redesigned by using Eurocode 8 (2004) provisions. The same geometrical data are used. These two buildings differ only in the reinforced cross sections of the members.
A pushover analysis is performed for the nonlinear cases of these two models by the means of FEMA 356 plastic hinges definitions and target displacement calculations and ATC 40 for the lateral load pattern. Also N2 method is mentioned in performance assessment methods for these purposes as it is integrated in Eurocode 8 (2004).
The comparison chart of the elastic base shear initially informed us that the difference between elastic base shear of the Eurocode 8 was 25-30% greater than KTP-89. This implied that the KTP-89 design code adequacy is found to be 20% less than the Eurocode 8 adequacy. In both x and y directions in terms of interstory drift ratios the ductility of the structures differs and even though the lateral capacity of the Eurocode 8 is 20% greater than that of KTP-89 the ductility of the existing building seems to be satisfactory. This is shown in the plastic hinge formation distribution too. The principle of “strong columns-week beams” is emphasized in both codes but it seems to be more obvious in Eurocode 8 due to rich ductile detailings.
This study has purported the assessment of KTP-89 after 23 years it has been issued.
An existing building is considered, representing a large number of the building stock in Albania. In terms of findings the performance level of this building obtained from the pushover analysis by the means of SAP2000 is found to be satisfactory. The differences between base shear forces calculated by KTP-89 and Eurocode 8 does not necessarily mean that the buildings designed by KTP-89 are totally unsafe.
Albania has been the cradle of many civilizations throughout the history as a result of its location. Each civilization had left its physical signs in the form of small objects to large scale buildings and sometimes even to almost complete cities. Some of the remains of the past have been able to survive until our time and the others have been lost in the course of time partly by human activities and other natural disasters.
Hundreds of masonry churches have been constructed in Albania during hundreds of years. The majority of them exist at their original location; a significant part of them are not still in use. These structures should be conserved in their own settings with their original characteristics or with as minimum changes as possible. However, natural or man-made hazards cause a serious risk for their survival. While some of them require to be strengthened only, some should be relocated to a new site, since there is no means to save them without transporting. They are the major points for the continuity of history. Therefore, in order to develop suitable restoration projects without neglecting any of the unique cultural values, it is very important to determine the present conditions of these structures. In this context, Roman and post- Byzantine masonry churches attract special attention to Albania in the world.
It is necessary to carry out systematic studies to assess an inventory and determine the state of masonry churches in Albania, to preserve them, to strengthen their basic structural element, the arch, vault and other constructive components and soundly deliver them into the future.
From this point of view, this study aims to classify the churches built in post-Byzantine period based on the plan and spatial composition of these structures. After that, depending upon this typological classification, the church of the “Monastery of Saint Nicholas” is selected as a case to investigate its structural performance. The church of the Monastery of Saint Nicholas is a domed single-nave church dating back to the 16th-17th century. It is located in the outskirts of Saranda, in the village of Dhiver. This church is situated inside a monastery complex and it is proclaimed a monument of culture by IMK (Intitute of Monuments of Culture Albania).
Albania is an earthquake prone country and lies in the Mediterranean seismic belt. Throughout its history it has suffered the consequences of some strong earthquakes. Important cities like Durres, Shkodra and Vlora have been destroyed in the past due to these severe earthquakes. For this reason, the earthquake resistant considerations for building design have been implemented in Albania during the last 50 years. However, it is important to understand weather the structures built according to these provisions have an adequate performance in light of modern seismic provisions.
The objective of this thesis is to evaluate the seismic performance of a public reinforced concrete building by nonlinear analysis methods. As a case study was considered a 5-story reinforced concrete building designed to serve as a health clinic in Tirana. For the seismic performance evaluation of the case study building were used both nonlinear static (pushover) analysis and nonlinear dynamic (time-history) analysis. The capacity curves of the investigated building were determined by pushover analysis conducted for both principal directions in accordance with the Capacity Spectrum Method. Performance of the structure was evaluated based on seismic demands determined from the response spectra of both KTP-N.2-89 and Eurocode 8. The nonlinear dynamic time history analysis was conducted with a set of seven natural earthquake ground motions from the Mediterranean seismic region.
The global response of the structure was evaluated in terms of base shear and drift demands. The performance evaluation was carried out considering response parameters such as interstory drifts. The results showed that the structure exceeded the allowable interstory drift limit values by varying degrees for different analysis methods or type of structure.
One of the natural phenomena, the earthquake, is the crucial factor generating a lot of structural failure, damage, loss of human life etc. There exist irregularities such as soft story, short columns, overhangs and the infill of masonry in all engineering structures. Moreover, these irregularities put human life in risk during an earthquake. The behavior of structure containing different irregularities during an earthquake is what the engineers are interested for. A lot of research has been made and continues taking into consideration different earthquakes, structural irregularities, soil type etc. The aim of this study is to compare the nonlinear behavior of a reinforced concrete building influenced by different structural irregularities. A seven story reinforced concrete building located in Albania is taken into consideration for this study. During the studies eleven cases with different structural irregularities are generated and analyzed, using the structural software CDSWin (Computer Design of Structure) according to the Eurocode norms, and compared with each other. Nonlinear static analyses (NSA), is used to analyze the structural irregularities and its effects on structural behavior and based upon the results, which of the cases is the worst during an earthquake is derived in the end.
Performance-based seismic design explicitly evaluates how a building is likely to perform, given the potential hazard it is likely to experience, considering uncertainties inherent in the quantification of potential hazard and uncertainties in assessment of the actual building response. It permits design of new buildings or upgrade of existing buildings with a realistic understanding of the risk of casualties, occupancy interruption, and economic loss that may occur as a result of future earthquakes.
It also establishes a vocabulary that facilitates meaningful discussion between stakeholders and design professionals on the development and selection of design options. It provides a framework for determining what level of safety and what level of property protection, at what cost, are acceptable to building owners, tenants, lenders, insurers, regulators and other decision makers based upon the specific needs of a project.
In contrast to prescriptive design approaches, performance-based design provides a systematic methodology for assessing the performance capability of a building, system or component. It can be used to verify the equivalent performance of alternatives, deliver standard performance at a reduced cost, or confirm higher performance needed for critical facilities.
Thousands of reinforced concrete buildings have been constructed all over Albania during the last 60 years. According to the Population and Housing Census records of 2012 the number of residential buildings in Albania was 598 267. More than 80 % were mainly one storey detached houses, with only one dwelling. Only 3.7 % (22 136) of them were apartment buildings, of which 31.3 % (6 929) were located in the prefecture of Tirana. Only 1.0 % (5 983) of them had 6 floors and more, while 2.1 % of the total had 9 dwellings or more. Buildings with 2 floors and buildings with 2 dwellings were about 10.0 % of the buildings used for residential purposes.
These buildings have been designed and constructed according to the relevant standards in force. As Albania is running towards the European Union and in the near future it will be part of the European family, it rises the obligation to revise and adapt all present Albanian standards with the relevant European Norms. One of the critical standards to be adapted to EUROCODE 8 is the Seismic Design of Buildings (KTP-N2-89). In this context this study aims to assess the seismic performance of 4-story and 7-story buildings designed for ductility class medium and ductility class high and for importance category 1 to 4. This will help Albanian structural designers to be aware of the seismic performance of the buildings designed according to EUROCODE-8.
In this present study two symmetrical R/C buildings, one 4-storey and the other one 7-storey, are designed (according to EUROCODE-8) for ductility class high and ductility class medium, for different importance categories form 1 to 4 using the commercial software STA4-CAD V.12.0. A total of 16 cases (8 for 4-story building and 8 for 7-storey building) haven designed. All design cases have been analyzed using Pushover Analysis. The pushover analysis has been carried out using ETABS Nonlinear Version 9.7.0.
The results of analysis are compared in terms of base shear, ductility, storey drift, and performance capacity. Based on the achieved results it can be stated that the all building cases designed according to EUROCODE-8 show a high overall seismic structural performance. Buildings designed for DCM exhibit less lateral and interstorey drift ratios than the ones designed for DCH. The total base shear capacity is higher in buildings designed for DCM than the ones designed for DCH.
Basilicas built in the Post Byzantine period in Albania spans a period of four hundred years, from the XVI century through the XIX century. These masonry religious objects shows particular interest because of the different types of building typologies that is why it is important to be saved for the forthcoming generations.
This study describes the St. Sotiri basilica located in the southern city of Gjirokastra, a city with historical and architectural value which is considered a world heritage city and it is protected by UNESCO.
However for these religious masonry buildings there are no restoration plans until today so the purpose of this study is to present a solution to repair the structural problems of this historical object without changing the identity of the monument.
This case study involves the study of different methods for the rehabilitation of historic masonry structures, inspection and analysis of the Basilica of St. Sotiri structure by the method of finite elements in engineering program Sap 2000.
The masonry structure is analyzed under static and dynamic loads and there are identified the weak locations prone to failure.
After conducting the seismic analysis of the building and finding the weak points of the structure are presented restoration methods that are in harmony with the physiognomy of the object and are simple to implement/
Many existing structures located in seismic regions are inadequate based on current seismic design codes. In recent years a significant amount of research has been devoted to the study of various strengthening techniques to enhance the seismic performance of existing RC structures. In this study has been made a hypothesis of retrofitting of a four story multi-functional building, with the ground floor used for shopping spaces and the other floors as apartments. The geometrically regular frame structure of the building has been designed according to the “KTP ‘89” code. Through the nonlinear static analysis (Pushover analysis) was evaluated the seismic performance of the structure. The processing of the received data has been made according to the FEMA-356 and ATC-40 guidelines. Through these design codes it has been evaluated the global and local state of the structure. Based on the seismic evaluation results, two possible retrofit techniques were applied to improve the seismic performance of the structure, including addition of shear walls and addition of RC column jackets.