Department of Civil Engineering

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http://hdl.handle.net/20.500.11905/1210

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BEHAVIOR OF PIN CONNECTIONS UNDER AXIAL LOAD
(2023-01-27) YAHYA, Mustafa Ahmed; SÖNMEZ, Ertan
Pin connections are commonly used in engineering structures due to their simplic ity and ease of construction. Although their structural behavior and design is rel atively simple, the stress distribution due to the mechanics of two contact surfaces is actually quite complex. In design codes, the geometry of the pin connections is typically restricted by some empirical equations without any detailed information on their development. In this thesis, the behavior of pin connections under axial load is investigated by analyzing parametric finite element models and studying the effects of pin-to-hole diameter ratio, eccentricity of the hole (in axial direction), and bend ing of the pin. The contact interaction between the pin and the plate is modeled by face-to-face penalty contact formulation. The contact between the pin and the plate is assumed to be frictionless. The accuracy of models is checked via mesh sensitiv ity analyses and comparison to analytical solutions given by Hertz for non-conformal cylindrical contacts and by Persson for conformal cylindrical contact. Based on the results of analyses performed in this study, it is found that all three parameters (i.e., pin-to-hole diameter ratio, eccentricity of the hole and bending of the pin) can have significant effects on stress concentration in pin connections. Although two-dimensional models are useful in preliminary assessment and model verification, they ignore through-thickness effects that may be significant in some cases; therefore, three-dimensional models provide more accurate representation of stress distribution in the pin connections. The analyses also confirm that the analytical solutions of both Hertz and Persson gave reasonable results for smaller contact angles when pin bending effect is not present while Hertz’s solution deviates significantly from the results of finite element models with neat-fit pin having a more conformal contact surface with larger contact angles (i.e., total contact angles higher than 40◦ ).
OPTIMIZATION OF CONCRETE FILLED STEEL TUBULAR COLUMNS UNDER ECCENTRIC COMPRESSIVE LOADING
(2022-04-10) AL-NUWAB, Sirree Naji Mahmood; AKIŞ, Tolga
This study addresses the optimum design of circular concrete filled steel tubular (CFST) columns under the action of eccentric loading. The well-known particle swarm optimization (PSO) algorithm is used for the cost minimization of these columns. Two dimensional axial force-bending moment interaction curves are assumed to be in the forms of polynomial expressions, which are evaluated by a number of empirical equations based on experimental results. The local and global buckling are considered to be the two main constraints used in the optimization studies. A computer code is developed in the scope of this work in which the PSO algorithm in MATLAB is implemented. Circular CFST columns with different heights, steel yield stresses and concrete strengths are considered in the optimization studies. The obtained numerical results, based on different values of axial loads and bending moments indicate the usefulness and efficiency of the proposed approach in optimum design of the CFST columns.
STRENGTHENING DEFICIENT RC BUILDINGS USING EXTERNAL STEEL BRACES
(2022-06-14) ERPEK, Berk; MERTOL, Halit Cenan
Based on Ministry of Environment and Urbanization of Turkey, there are 5 million earthquake resistant apartments out of a total of 19,5 million apartments in Turkey. Seven million apartments need urgent action for a strengthening solution or shall be demolished immediately. It is not possible to demolish and rebuild all these deficient structures. Strengthening them includes many complications. One of the most important complications is the replacement of the occupants from the deficient buildings during the construction process. Strengthening of existing reinforced concrete structures using external steel braces method is getting popular worldwide since it may be performed faster, cheaper and without impacting the inhabitants who live in these structures. The purpose of this research is to determine the effectiveness of external strengthening using steel braces for existing reinforced concrete buildings. Four building models having number of stories 3, 6, 9, and 12 were analytically investigated. These building models were designed as deficient buildings according to Turkish design codes. The performances of the deficient building models were evaluated using three different methods, Equivalent Static Earthquake Load, Pushover Analysis, and Time History Analysis. These deficient buildings were strengthened using external steel braces and the performances were evaluated using these methods. The results indicated all building models can effectively be strengthened using inverted-V configured external steel bracing system. Buildings up to 9 stories can be effectively strengthened using X configured steel bracing system. The most cost effective strengthening system was the one having one steel frame on each side of the building.
UTILIZATION OF POWDERED GLASS AND EXPANDED POLYSTYRENE BEADS (EPS) AS ADDITIVES IN CLAYEY SOILS
(2022-06-14) ÇİĞDEM, Öykü Yağmur; AKIŞ, Ebru
Waste management is gaining importance since the impact of climate change on human life becomes more apparent. In this study, it is aimed to investigate the effect of waste materials on the improvement of high plasticity clay. Glass powder and expanded polystyrene beads (EPS) are selected as waste materials since both additives have the lowest recycling rate (4.43% and 4.47%, respectively) among solid wastes. The effect of these materials is evaluated both individually and together with various experiments such as the Atterberg limit test, standard proctor test, one-dimensional swell, and unconfined compressive strength tests. Additive percentages are set at 0.3%, 0.9%, and 2% of the dry weight of the soil sample for EPS and 2%, 4%, and 6% of the dry weight of the soil for glass powder. Test results show that the addition of waste glass powder causes an increase in unconfined compressive strength and a decrease in free swell values. When EPS is used as the only additive, a decrease in the unconfined compressive strength and free swell values is observed. Furthermore, the combination of 4% of glass powder and 0.9% of EPS addition causes the most effective improvement in both unconfined compressive strength and free swell values. In addition to the experimental studies, the obtained data from this study, and the test results of related studies in the literature are used together to build up datasets. These datasets are used to perform multilinear regression (MLR) and artificial neural network (ANN) analyses. As a result of MLR analyses, prediction equations are proposed to estimate the free swell or unconfined compressive strength of the improved soils depending on the additive contents, free swell, or unconfined compressive strength of untreated soils. When the same dataset is used for ANN analysis, similar results with the MLR analyses are observed. Furthermore, if the provided data is limited to the Atterberg limits only, the ANN method provides reliable predictions of those parameters. A 5-fold cross variation is performed to verify that the results of ANN analysis do not depend on the selection of the data sets. Both MLR and ANN methods show that it is possible to predict the free swell and unconfined compressive strength of treated soil samples with high correlation coefficients.
USE OF ROCK MASS CLASSIFICATION SYSTEMS FOR THE PREDICTION OF TUNNEL SUPPORTS: A CASE STUDY OF SIIRT MADENKOY ENTERPRISE
(2022-05-12) BALCI, Bora Mehmet; ÖZGENOĞLU, Abdurrahim
It is extremely important to apply the support systems in the tunnels according to the physical and mechanical properties of the formations. This issue, which has also been studied by researchers, continues to be investigated today in the disciplines of civil and mining engineering. Rock mass classification systems are used for the implementation of support proposals. Many tunnel projects have been designed with the help of these systems. Among these rock mass classification systems, RMR and Q classification systems are the most preferable systems to design supports. Tunnel are designed by using these systems. It is necessary to utilize rock mass classification systems while preparing the tunnel designs due to the changing formations in the tunnel path. It is clear that the rock classification method and support design proposals put forward by Barton et al. can be an important tool for determining whether any support is required for the opening given in metal mine main galleries or in determining the maximum unsupported opening in a certain rock unit. It is even possible to argue that the use of Q classification systems can help for the selection of the support methods such as rock bolts or shotcrete with today’s technology. These classification systems were used by Siirt Madenköy Copper Mine Enterprise. Since such classifications were very important tools required at every stage of excavation and support, the current research progressed in the safest and fastest way.
RISK ASSESSMENT IN PUBLIC-PRIVATE PARTNERSHIP CITY HOSPITAL PROJECTS IN TURKEY
(2022-09-12) DOĞAN, Tuğba; AKÇAY, Emre Caner
Governments have difficulties in realizing the services that they should provide to the public due to their limited funds. This leads to the gradual increase in the use of the Public-Private Partnership (PPP) model, which is an alternative financing model. PPP is a long-term cooperation between the private and public sector to provide public services. Turkey is one of the developing countries that does not have enough funds, and implements the PPP model to fulfill urgent public needs. For the last ten years, Turkish Government has widely used the PPP model especially in realizing city hospital projects. However, the investors have experienced with several difficulties in implementing the projects due to several risk factors. Therefore, the main objective of this thesis is to perform the risk assessment for the PPP city hospital projects in Turkey. In this context, the list of potential risks in PPP city hospital projects was investigated by means of an extensive literature review. The probability of occurrence and the severity of impact of risk factors were explored through a questionnaire survey. The collected data was analyzed to investigate the priority of risk factors. The results revealed that the top five most important risk factors in PPP city hospital projects in Turkey are foreign exchange rate fluctuations, inflation rate volatility, high finance cost, fiscal, and economic crisis, whereas poor productivity of equipment was the least significant risk factor. The results of this thesis can guide the future investors willing to invest in PPP city hospital projects in Turkey.
EVALUATION OF MODIFIED AND EXTENDED PUSHOVER METHODS FOR RC BUILDINGS HAVING SETBACK IRREGULARITY
(2022-09-12) HASAN, Ghadeer; MERTOL, Halit Cenan
Irregular configurations of reinforced concrete buildings were frequently identified as one of the main causes of failures during previous earthquakes. The setback irregularity which occurs due to abrupt reduction of the lateral dimension of the building at specific levels of elevation may be catastrophic for buildings having various heights. Engineers are more likely to adopt simplified nonlinear static analytical procedures such as pushover analysis when evaluating the seismic performance of reinforced concrete buildings due to its ease in application. The use of conventional pushover analysis methods provides acceptable results low-rise buildings. However, these methods do not provide sufficient results for mid- and high rise buildings whose behavior under seismic actions is not only governed by the fundamental mode shape. To overcome this problem, some advanced methods considering the effects of higher mode shapes were proposed by various researchers. However, the applicability of these methods to three dimensional high-rise buildings having setback irregularity was not addressed in the literature. In this study, a total of 6 mid- and high-rise building models having setback irregularity at various locations were analyzed using nonlinear pushover analysis methods namely the Inverted Triangular Lateral Load Pattern (TLP) according to ASCE 7-22, First Modal Shape Lateral Load Pattern (FLP), Uniform Lateral Load Pattern (ULP), Modified Upper Bound Method (MUB), and Extended Upper Bound Method (EUB), to evaluate the applicability of these methods. The results obtained using these methods were compared to the Nonlinear Time History Analysis Method (NLTHA) which provided benchmark solutions to the problems. Three of the building models had 6 stories and the other three had 12 stories. The story heights of the models were all 4.5 m at the ground story and 3.2 m for the rest of the stories. All models had four bays in both plan view directions with a typical length of 6 m each. One model of each height level was a regular building and used for comparison purposes. Other two models of each height level had setback irregularity in various locations of the elevation in one direction. The results were assessed for seismic demand variables such as lateral displacements, interstory drift ratios, and plastic hinge rotations. The EUB method also provided more accurate results of interstory drift ratios of all irregular building models compared to those of the conventional pushover analysis procedures (TLP, FLP, and ULP). Conventional pushover methods were not sufficient to predict the plastic hinge rotations at the upper stories of the 6 and 12 story building models, whereas the EUB method provided reasonable estimates of these plastic hinge rotationsfor irregular buildings.
NUMERICAL MODELING OF THE AUGUSTUS TEMPLE
(2010-01-27) DÖĞER, Rıdvan; SARI, Yasin Dursun
This thesis reviews the numerical modeling of the Augustus Temple. “3DEC” software by Itasca and “PLAXIS” software by PLAXIS B.V. were used to perform the numerical analysis. Recommendations for future testing and monitoring were discussed. Analysis methods and properties of dry stone structures were also discussed in this thesis.
ANALYTICAL INVESTIGATION OF MULTI-LAYER COMPOSITE TUBES SUBJECT TO PRESSURE
(2010-01-27) ATLI, Ahmet; AKIŞ, Tolga
The aim of this study is to present an analytical approach for the stress analysis of multi-layer composite tubes under internal and external pressure. The expressions of stresses and displacements for single, two and three-layer tubes are obtained and the critical cases of yielding are examined using Tresca’s and von Mises yield criterion. The analytical solutions are checked numerically for different material sets and the stress and displacement distributions are obtained. It is found that yielding begins at the inner surface of the single layer tubes under internal or external pressure. For the two-layer tubes, yielding may begin at the inner surface of the inner or outer tubes or simultaneously at both locations. For the three layer tubes different cases of yielding may occur depending on the material properties. In the study, the conditions for these various yielding cases are thoroughly examined.
INVESTIGATING USE OF UNTENSIONED PRESTRESSING STRANDS IN REINFORCED CONCRETE FLEXURAL MEMBERS
(2011-01-26) ARSAVA, Tuğba; BARAN, Eray
In this thesis use of untensioned prestressing strand in flexural members as tension reinforcement is investigated. In manufacturing of prestressed/precast concrete elements prestressing strands are used. According to a questionnaire survey carried out by companies being active in manufacturing of prestressed/precast products it is observed that the remaining pieces of cut strands are used only as lifting hooks. In case these remaining pieces could be used as bending reinforcements, it will be possible to make a more economical use of these high strength products which are imported from abroad. When conventional reinforcing bar and high strength strand compared, high strength strand strands indicate different stress-strain behavior. The fulfillment of the design requirements of the contemporary building regulations about using concrete elements reinforced with high strength strands instead of concrete elements reinforced with conventional reinforcing bars, is still a field which is open to investigation and research. Aiming to contribute closing the gap in literature on the subject issue, a research is carried out consisting of laboratory tests supported by analytical analysis. thirteen reinforced concrete beams prepared, seven out of thirteen beams were reinforced with conventional reinforcing bars and the remaining six beams reinforced with high strength strands. All beams were tested under two point loading. Following the laboratory tests, a numerical parametrical evaluation is carried out on beams with different cross-sectional areas and with different material properties. Following the laboratory tests and the numerical analysis, the behaviour of concrete members which are reinforced with high strength steel strands instead of standard reinforcing bars under bending conditions are evaluated and the differences observed are noted. Finally the applicability of the procedures with regard to provision of moment carrying capacities and the minimum required ductility levels identified in American Concrete Institute (ACI-318) and TS500 regulations to concrete beam elements reinforced with high strength tensile strands are reviewed and summarized.
DEVELOPMENT OF STEEL-CONCRETE HYBRID CONNECTIONS FOR PRECAST CONCRETE MOMENT-RESISTING FRAMES
(2013-06-21) KURTOĞLU, Metin; BARAN, Eray; BARAN, Mehmet
Hybrid beam-column connection details to be used in precast concrete moment resisting frames were developed in this study. Experimental part of the study included testing of fourteen precast concrete beam-column connection specimens utilizing the proposed hybrid connections and two monolithic beam-column connection specimens under reversed cyclic loading. Strength, stiffness, energy dissipation capacity and ductility characteristics of the specimens were examined by evaluating the test results. The effect of various parameters including the geometry of steel connection components, amount of bolt pretension to be used at the connection region, method of anchoring the connection components in beam elements, and the detailing of beam reinforcement near the connection region on the behavior of the beam-column connection region was investigated. After producing useful experimental evidence, further analytical studies were conducted in an attempt to study the behavior of typical precast concrete structural systems made of moment resisting frames under lateral load effects. Within this context, finite element models of three- and five-story planar frames were prepared and lateral nonlinear static pushover analyses were conducted on these models. The experimental and analytical studies revealed that the proposed hybrid precast concrete beam-column connection details offer the potential of providing a performance comparable to their monolithic counterparts.
LATERAL LOAD BEHAVIOR OF COLD-FORMED STEEL WALL PANELS
(2013-06-15) ALICA, Hüseyin Çağatay; BARAN, Eray
In this thesis, lateral load behavior of cold-formed steel (CFS) wall panels was investigated. For this purpose full-scale CFS wall panel specimens were tested experimentally. Measured load capacity of wall panels were also compared with numerically predicted values. Experimental part of the study included monotonic lateral load testing of twenty one CFS wall panels. Wall panels were sheathed with oriented strand board (OSB), fibercement and betopan panels. Influence of additional parameters, such as sheathing panel thickness, screw spacing, CFS section size, existence of diagonal struts and double-sided sheathing was also investigated. Using the information obtained from load tests, the lateral behavior of the wall panels was studied and the differences and similarities in the response of these panels were investigated. Response of wall panels under lateral loading was determined to be directly related with the behavior of the hold-down attachment used at the base of panels. In most of the specimens tested in this study, the strength and stiffness of the hold-down attachment prevented the wall panels to reach the expected strength and stiffness levels. Among the parameters investigated in this study the one that had the most significant effect on the behavior of wall panels was the screw spacing used at exterior framing members. Between the cases of 15 cm and 30 cm screw spacing, the increase in load capacity of wall panels was between 37% and 85% depending on the type and thickness of sheathing panel.
ENHANCING CIVIL ENGINEERING EDUCATION USING ACTIVE LEARNING TECHNIQUES
(2013-08-14) ÇALIŞKAN, Nihan Tuğba; MERTOL, Halit Cenan
In the last few decades the civil engineering prefession has rapidly developed to be able to adapt to changing conditions in various areas worldwide. Besides, the 21st century students are also completely different from the students who lived in the 20th century. The advances in technology have a great influence on these students. They don’t know the life before computer, cell phones etc. The traditional educational methods containing passive teaching methods no longer work for current students. Most of the students in this century are active learners and active teaching methods should be used to be able to get good performance from these students. In this study computer games, hands-on-practices, experiments, laboratory works used as active teaching methods and applied on different courses such as Statics, Dynamics, Strength of Materials, and Fundamentals of Reinforced Concrete, and the change in students’ performance is evaluated.
ROAD SAFETY AUDIT AND A CASE STUDY ON KANO-KADUNA ROAD IN NIGERIA
(2014-06-09) BALA, Nura; AYDIN, Cumhur
The consequence of increasing number of traffic volume, road safety improvement is becoming a major policy for the road authorities. Road accidents create both social and economic cost on the country’s economy. When this is taken into consideration, it is therefore important to display different solution alternatives considering the budget limitations of the road authorities. Road accidents are serious problems throughout the world especially in low and middle income countries considering social, health and economic terms. The number of road accidents in such countries tends to increase every year. In this thesis, a case study is selected in Nigeria and the studies were performed to summarize actual practices of road safety auditing on existing roads in different countries. By taking account these different opinions and auditing procedures into account a strategy for road safety auditing on existing roads that fits to Nigerian roads conditions is proposed. For an evaluation, a case study was conducted in order to determine whether the proposed methodology adds a value to the highway network follow up and improvements. Based on this study, the audit report was prepared to summarize findings with possible countermeasures.
WORK ZONE SAFETY AUDIT AND CASE STUDY IN KANO, NIGERIA
(2014-06-09) UMAR, İbrahim Khalil; AYDIN, Cumhur
The continuing increase in vehicles demand resulted in the construction of new roads as well as improvement of the existing ones, hence creating more work zones. These work zones poses more dangers to the life and safety of road users and the workers performing various tasks. This thesis research reviews the concept of work zone safety audit at construction stage. The various safety measures for efficiently and safely guiding traffic through the work zone, improving the safety of workers, equipment, and the road users traversing through the work zone were also reviewed. A case study on a Nigerian highway was conducted where lack of regular maintenance of the installed temporary traffic control devices, non-compliance with standards, human behaviors like over speeding, disregard to traffic rules in the work zone were identified to be the major causes of all hazards within the work zone.
IN-DEPTH ACCIDENT ANALYSIS AND CASE STUDY IN NIGERIAN ROAD AND TRAFFIC CONDITION
(2014-06-09) DAYYABU, Abubakar; AYDIN, Cumhur
The in-depth accident investigation is the process of detail data gathering related to the involved persons, the road/environment, involved vehicles for the purpose of detail analysis and the reconstruction of the accident. It can be used to conclude on the main causes of accidents and proposing an appropriate and effective countermeasure, to prevent re-occurrence of similar accident type. The thesis has reviewed and modified European Truck Accident Causation Study methodology. The modified methodology was applied on Nigerian Highways. In the modified methodology 100 parameters comprising of detail information of involved persons, vehicles, road and environment were collected and analyzed to come up with the accident causes and proposed an effective countermeasure. The use of the Nigerian National Accident Investigation Manual, the comprehensive Truck database can help in better understanding the main causes of truck involved accidents, and hence providing effective countermeasures.
FLEXURAL BEHAVIOR OF PRECAST PRESTRESSED CONCRETE HOLLOW-CORE SLABS WITH CAST-IN-PLACE CONCRETE TOPPING
(2014-06-09) HARUNA, Sadi İbrahim; BARAN, Eray
Flexural behavior of precast prestressed concrete hollow-core units with cast-in-place concrete topping was evaluated through load testing of five full-scale specimens. The specimens were divided into two groups of wide and narrow. A cast-in-place concrete was cast on top of the hollow-core units selected from the two groups to form a composite system. An additional specimen was tested with restraining mechanisms used at both ends in order to reduce the relative slip between the hollow-core unit and topping slab. Presence of cast-in-place topping slab improved the behavior of hollow-core units by increasing the flexural crack initiation and maximum load capacities as well as the stiffness. Specimens tested with cast-in-place concrete topping slab suffered from a sudden drop in the load resisting capacity due to the slip of the topping slab relative to the hollow core unit. As a result of premature loss of composite behavior, the predicted load capacity of these specimens assuming a fully composite behavior remained on the non-conservative side. The loss of composite behavior corresponded to an interfacial shear strength value that is smaller than the values specified by the ACI and AASHTO Specifications. The results obtained in this study suggest that floor system made of cast-in place concrete topping placed over the machine finished surface of precast concrete hollow-core units with no interfacial roughening is not able to provide the interface shear strength required to develop a fully composite behavior.
SAFETY AUDITING ON URBAN ROADS WITH SPECIAL EMPHASIS TO INTERSECTIONS IN A CASE STUDY IN KANO, NIGERIA
(2014-06-09) HABIBU, Abubakar Sani; AYDIN, Cumhur
The current international reviews and action plan strategies regarding rapid increase in road traffic volumes and present status of huge number of traffic accidents have made road safety audits/inspection procedures necessary major policy for implementation in any country worldwide. Road traffic accidents affect social and economic aspects of any country which need serious and urgent action to be taken in order to provide effective improvements, solutions, suitable and desired counter measures so as to avert the present situations. In this aspect, urban road safety audits have been analyzed in the study. A case study of an urban Katsina Road section in Kano, Nigeria was selected and evaluated using actual practices, strategies, and procedures of road safety audits in developed countries in relation to deficiencies, hazards and intersection capacity and level of service measures. Based on the evaluated case study conditions through proposed methodology, different number of safety defects were detected and related counter measures were proposed for the present case study accident potentials, capacity and level of service for accident severity reduction and elimination.
PARAMETRIC STUDY OF OIL AND GAS INTERNAL PRESSURES IN BURIED PIPELINES
(2014-07-09) SHAALAN, Heyam Hussein; SARI, Yasin Dursun
This study presents a parametric analysis of the behavior of buried oil and gas pipelines in different soil condition, subjected to static loading, where the influence of fluid internal pressures is taken into account. The crown steel pipe displacement has been computed numerically with respect to the applied surface loads for different burial depths of soil conditions (dense sand, loose sand and clay). The mechanical behavior of pipes is evaluated by means of a two- dimensional finite element method PLAXIS. A large number of the calculation results were analyzed and evaluated. On this basis, the results were fitted by non-linear regression analysis. This study is concerned with the effect of soil media (dense sand, loose sand and clay), burying depth, fluid materials (oil and gas), location of applied load, adjoin pipes, internal fluid pressure and mechanical parameters of pipe (such as pipe diameter and pipe wall thickness).Comparison was also carried out.
DYNAMIC AND STATIC ANALYSES OF THE OIL AND GAS PIPELINES
(2014-07-09) HASSAN, Marwan Adil; SARI, Yasin Dursun
In this study, a numerical calculation on interaction between soil and steel pipelines was performed. Properties of soil and pipe may cause significant effects on the movements of buried pipelines. To improve the understanding of the behavior of buried pipelines subjected to dynamic and static loading, different oil and gas pipes have been considered in this study. Earthquake load of magnitude 5.4 with time shaking of 10 sec and surface loads (50, 100, 150 and 200 kPa) have been used. To simulate numerically this effects, 2D finite element method PLAXIS is performed. The results are discussed and fitted by univariate linear and non-linear analysis. Some influential factors such as soil types (clay, loose and dense sand), soil layers (one, two and three soil layers), underground water table, static water loads (of height 20m above soil), burying depth, pipe diameter and pipe thickness are discussed in details. Based on the results, it can be concluded that these factors are important items on pipeline displacement for both static and dynamic loads. Some significant comparisons and conclusions are drawn.

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