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- 저자 : Barbaro, Bruno (검색결과 34 건)
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Camber calculation of prestressed concrete I-Girder considering geometric nonlinearity
Barbaros Atmaca,Şevket Ateş 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.19 No.1
Prestressed concrete I-girders are subject to different load types at their construction stages. At the time of strand release, i.e., detensioning, prestressed concrete girders are under the effect of dead and prestressing loads. At this stage, the camber, total net upward deflection, of prestressed girder is summation of the upward deflection due to the prestressing force and the downward deflection due to dead loads. For the calculation of the upward deflection, it is generally considered that prestressed concrete I-girder behaves linear-elastic. However, the field measurements on total net upward deflection of prestressed I-girder after detensioning show contradictory results. In this paper, camber calculations with the linear-elastic beam and elastic-stability theories are presented. One of a typical precast I-girder with 120 cm height and 31.5 m effective span length is selected as a case study. 3D finite element model (FEM) of the girder is developed by SAP2000 software, and the deflections of girder are obtained from linear and nonlinear-static analyses. Only geometric nonlinearity is taken into account. The material test and field measurement of this study are performed at prestressing girder plant. The results of the linear-elastic beam and elastic-stability theories are compared with FEM results and field measurements. It is seen that the camber predicted by elastic-stability theory gives acceptable results than the linear-elastic beam theory while strand releasing.
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Determination of proper post-tensioning cable force of cable-stayed footbridge with TLBO algorithm
Barbaros ATMACA 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.6
The pleasing appearances, economic and easy construction of cable-stayed footbridges (CSFB) have made them one of the most preferred options for pedestrian traffic crossing over the highways. The basic structural members of CSFB can be sortable as a foundation, pylon, deck, and stay-cables. The stay-cable has an important role in the formation of structural integrity by ensuring that the deck and pylon work together with the help of proper post-tensioning forces (PTF) applied to them. In this study, it is aim to determine proper set of PTF with the help of the developed optimization process which provides to work together metaheuristic algorithm named Teaching-Learning-Based Optimization (TLBO) and Open Applicable Programming Interface (OAPI) properties of SAP2000 with codes created in MATLAB. In addition of this aim, the study also presents the importance of PTF for structural behavior of CSFB. TLBO algorithms use a randomly created initial population. The teacher phase and student phase are the main part of this algorithm. Five different proper sets of PTF are determined by using developed optimization process and the structural response such as displacement and internal forces of structural members of the selected CSFB compared with each other. Consequently, PTF directly affects the behavior of CSFB, as it ensures that displacements of deck and pylon remain between the acceptable limits, controls the distribution and magnitude of the internal forces for different load combinations. Furthermore, the evaluation of PTF might not have a single solution because CSFB are highly statically indeterminate so there are more different possible sets of PTFs that satisfy strength and serviceability requirements.
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Determination of minimum depth of prestressed concrete I-Girder bridge for different design truck
Barbaros Atmaca 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.24 No.4
The depth of superstructure is the summation of the height of girders and the thickness of the deck floor. In this study, it is aim to determine the maximum span length of girders and minimum depth of the superstructure of prestressed concrete I-girder bridge. For this purpose the superstructure of the bridge with the width of 10m and the thickness of the deck floor of 0.175m, which the girders length was changed by two meter increments between 15m and 35m, was taken into account. Twelve different girders with heights of 60, 75, 90, 100, 110, 120, 130, 140, 150, 160, 170 and 180 cm, which are frequently used in Turkey, were chosen as girder type. The analyses of the superstructure of prestressed concrete I girder bridge was conducted with I-CAD software. In the analyses AASHTO LRFD (2012) conditions were taken into account a great extent. The dead loads of the structural and non-structural elements forming the bridge superstructure, prestressing force, standard truck load, equivalent lane load and pedestrian load were taken into consideration. HL93, design truck of AASHTO and also H30S24 design truck of Turkish Code were selected as vehicular live load. The allowable concrete stress limit, the number of prestressed strands, the number of debonded strands and the deflection parameters obtained from analyses were compared with the limit values found in AASHTO LRFD (2012) to determine the suitability of the girders. At the end of the study maximum span length of girders and equation using for calculation for minimum depth of the superstructure of prestressed concrete I-girder bridge were proposed.
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Barbaros ATMACA,Tayfun DEDE,Maksym GRZYWİNSKİ 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.34 No.6
In recent years, due to the many advantages cable-stayed bridges have often constructed in medium and long span. These advantages can be listed as an aesthetically pleasing appearance, economic and easy construction, etc. The main structural elements of cable-stayed bridges are listed as deck, pylon, cables and foundation. Perhaps one of the most vital and expensive of these structural elements is stay-cables. Stay-cables ensure the allowable displacement and distribution of bending moments along the bridge deck with prestressing force. Therefore the optimum design of the stay-cables and prestressing force are very important in achieving the performance expected from the cable-stayed bridges. This paper aims to obtain the stay-cables size and prestressing force optimization of the cable-stayed bridge. For this purpose, single pylon and fan type cable configuration Manavgat Cable-Stayed Bridge was selected as an example. The three dimensional (3D) finite element model (FEM) of the bridge was created with SAP2000. Analysis of the 3D FEM of the bridge was conducted under the different combined effects of the self-weight of the structural element, prestressing force of stay-cable and live load. Stay-cable stress and deck displacement were taken into account as constraints for the optimization problem. To optimize this existing bridge a metaheuristic algorithm named Jaya was used in the optimization process. 3D FEM of the selected bridge was repeatedly analyzed by using Open Applicable Programming Interface (OAPI) properties of SAP2000. To carry out the optimization process the developed program which integrates the Jaya algorithm and the required codes for calling SAP2000 is coded in MATLAB. At the end of the study, the total weight of the stay-cables was reduced more than 40% according to existing stay cables under loads taken into account.
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Construction stage analysis of three-dimensional cable-stayed bridges
Barbaros Atmaca,Sevket Ates 국제구조공학회 2012 Steel and Composite Structures, An International J Vol.12 No.5
In this paper, nonlinear static analysis of three-dimensional cable stayed bridges is performed for the time dependent materials properties such as creep, shrinkage and aging of concrete and relaxation of cable. Manavgat Cable-Stayed Bridge is selected as an application. The bridge located in Antalya, Turkey, was constructed with balanced cantilever construction method. Total length of the bridge is 202 m. The bridge consists of one ë shape steel tower. The tower is at the middle of the bridge span. The construction stages and 3D finite element model of bridge are modeled with SAP2000. Large displacement occurs in these types of bridges so geometric nonlinearity is taken into consideration in the analysis by using P-Delta plus large displacement criterion. The time dependent material strength and geometric variations are included in the analysis. Two different finite element analyses carried out which are evaluated with and without construction stages and results are compared with each other. As a result of these analyses, variation of internal forces such as bending moment, axial forces and shear forces for bridge tower and displacement and bending moment for bridge deck are given with detailed. It is seen that construction stage analysis has a remarkable effect on the structural behavior of the bridge.
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Baseskioglu, Barbaros,Duman, Berna Bozkurt,Kara, I. Oguz,Can, Cavit,Yildirim, Mustafa,Acikalin, Mustafa Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.11
Background and Objectives: This study aimed to present the clinicopathological characteristics and treatment of patients with bladder carcinoma with sarcomatoid differentiation at our institution. Methods: Between 1995-2009, 950 patients were followed-up for bladder carcinoma. Among them, 14 patients with sarcomatoid carcinoma were retrospectively reviewed, and their clinical, pathological features and treatment were recorded. Results: Median age of the patients was 65 years (range: 41-86 years), 12 (86%) being male and 2 (14%) female. All the patients presented with hematuria and 11 (88%) had a history of smoking. The tumor growth pattern was solid in 10 patients, papillary in 2, and mixed in 2. In all, 5 of the patients had urothelial carcinoma with sarcomatoid differentiation and 9 were diagnosed with sarcomatoid carcinoma. Five patients underwent radical cystectomy with ileal conduit surgery, 2 patients refused cystectomy, and 8 patients underwent re-TUR. Following diagnosis, 12 of the patients died in mean 10.7 months (range: 1-48 months). Conclusion: Urothelial carcinomas with sarcomatoid features are aggressive and are usually at advanced stage at the time of diagnosis. The outcomes of multimodal treatment are not satisfactory. Significant findings of the present study are that early diagnosis positively affect survival and that gemcitabine and cisplatin in combination can positively affect survival.
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Determination of bearing type effect on elastomeric bearing selection with SREI-CAD
Atmaca, Barbaros,Ates, Sevket Techno-Press 2017 Advances in computational design Vol.2 No.1
The aim of this paper is to develop software for designing of steel reinforced elastomeric isolator (SREI) according to American Association for State Highway and Transportation Officials Load and Resistance Factor Design (AASHTO LRFD) Specifications. SREI is used for almost all bridge types and special structures. SREI-structures interface defines support boundary conditions and may affect the seismic performance of bridges. Seismic performance of the bridge is also affected by geometrical and materials properties of SREI. The selection of SREI is complicated process includes satisfying all the design constraints arising from code provisions and maximizing performance at the lowest possible cost. In this paper, design stage of SREI is described up to AASHTO LRFD 2012. Up to AASHTO LRFD 2012 analysis and design program of SREI performed different geometrical and material properties are created with C# object-oriented language. SREI-CAD, name of the created software, allows an accurate design for economical estimation of a SREI in a short time. To determine types of SREI effects, two different types of bearings, rectangular and circular with similar materials and dimension properties are selected as an application. Designs of these SREIs are completed with SREI-CAD. It is seen that ensuring the stability of circular elastomer bearing at the service limit state is generally complicated than rectangular bearing.
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