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An experimental study on strengthening of vulnerable RC frames with RC wing walls
M. Yasar Kaltakci,Gunnur Yavuz 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.41 No.6
One of the most popular and commonly used strengthening techniques to protect against earthquakes is to infill the holes in reinforced concrete (RC) frames with fully reinforced concrete infills. In some cases, windows and door openings are left inside infill walls for architectural or functional reasons during the strengthening of reinforced concrete-framed buildings. However, the seismic performance of multistory, multibay, reinforced concrete frames that are strengthened by reinforced concrete wing walls is not well known. The main purpose of this study is to investigate the experimental behavior of vulnerable multistory, multibay, reinforced concrete frames that were strengthened by introducing wing walls under a lateral load. For this purpose, three 2-story, 2-bay, 1/3-scale test specimens were constructed and tested under reversed cyclic lateral loading. The total shear wall (including the column and wing walls) length and the location of the bent beam bars were the main parameters of the experimental study. According to the test results, the addition of wing walls to reinforced concrete frames provided significantly higher ultimate lateral load strength and higher initial stiffness than the bare frames did. While the total shear wall length was increased, the lateral load carrying capacity and stiffness increased significantly.
Prediction of force reduction factor (R) of prefabricated industrial buildings using neural networks
M. Hakan Arslan,Murat Ceylan,M. Yasar Kaltakci,Yüksel Ozbay,Fatma Gulten Gulay 국제구조공학회 2007 Structural Engineering and Mechanics, An Int'l Jou Vol.27 No.2
The force (load) reduction factor, R, which is one of the most important parameters in earthquake load calculation, is independent of the dimensions of the structure but is defined on the basis of the load bearing system of the structure as defined in earthquake codes. Significant damages and failures were experienced on prefabricated reinforced concrete structures during the last three major earthquakes in Turkey (Adana 1998, Kocaeli 1999, Duzce 1999) and the experts are still discussing the main reasons of those failures. Most of them agreed that they resulted mainly from the earthquake force reduction factor, R that is incorrectly selected during design processes, in addition to all other detailing errors. Thus this wide spread damages caused by the earthquake to prefabricated structures aroused suspicion about the correctness of the R coefficient recommended in the current Turkish Earthquake Codes (TEC - 98). In this study, an attempt was made for an approximate determination of R coefficient for widely utilized prefabricated structure types (single-floor single-span) with variable dimensions. According to the selecting variable dimensions, 140 sample frames were computed using pushover analysis. The force reduction factor R was calculated by load-displacement curves obtained pushover analysis for each frame. Then, formulated artificial neural network method was trained by using 107 of the 140 sample frames. For the training various algorithms were used. The method was applied and used for the prediction of the R rest 33 frames with about 92% accuracy. The paper also aims at proposing the authorities to change the R coefficient values predicted in TEC - 98 for prefabricated concrete structures.
An experimental study on strengthening of vulnerable RC frames with RC wing walls
Kaltakci, M. Yasar,Yavuz, Gunnur Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.41 No.6
One of the most popular and commonly used strengthening techniques to protect against earthquakes is to infill the holes in reinforced concrete (RC) frames with fully reinforced concrete infills. In some cases, windows and door openings are left inside infill walls for architectural or functional reasons during the strengthening of reinforced concrete-framed buildings. However, the seismic performance of multistory, multibay, reinforced concrete frames that are strengthened by reinforced concrete wing walls is not well known. The main purpose of this study is to investigate the experimental behavior of vulnerable multistory, multibay, reinforced concrete frames that were strengthened by introducing wing walls under a lateral load. For this purpose, three 2-story, 2-bay, 1/3-scale test specimens were constructed and tested under reversed cyclic lateral loading. The total shear wall (including the column and wing walls) length and the location of the bent beam bars were the main parameters of the experimental study. According to the test results, the addition of wing walls to reinforced concrete frames provided significantly higher ultimate lateral load strength and higher initial stiffness than the bare frames did. While the total shear wall length was increased, the lateral load carrying capacity and stiffness increased significantly.
Muhammad Yasar Javaid,Mark Ovinis,Fakhruldin B.M. Hashim,Adi Maimun,Yasser M. Ahmed,Barkat Ullah 대한조선학회 2017 International Journal of Naval Architecture and Oc Vol.9 No.4
We are developing a prototype underwater glider for subsea payload delivery. The idea is to use a glider to deliver payloads for subsea installations. In this type of application, the hydrodynamic forces and dynamic stability of the glider is of particular importance, as it has implications on the glider's endurance and operation. In this work, the effect of two different wing forms, rectangular and tapered, on the hydrodynamic characteristics and dynamic stability of the glider were investigated, to determine the optimal wing form. To determine the hydrodynamic characteristics, tow tank resistance tests were carried out using a model fitted alternately with a rectangular wing and tapered wing. Steady-state CFD analysis was conducted using the hydrodynamic coefficients obtained from the tests, to obtain the lift, drag and hydrodynamic derivatives at different angular velocities. The results show that the rectangular wing provides larger lift forces but with a reduced stability envelope. Conversely, the tapered wing exhibits lower lift force but improved dynamic stability.
Javaid, Muhammad Yasar,Ovinis, Mark,Hashim, Fakhruldin B.M.,Maimun, Adi,Ahmed, Yasser M.,Ullah, Barkat The Society of Naval Architects of Korea 2017 International Journal of Naval Architecture and Oc Vol.9 No.4
We are developing a prototype underwater glider for subsea payload delivery. The idea is to use a glider to deliver payloads for subsea installations. In this type of application, the hydrodynamic forces and dynamic stability of the glider is of particular importance, as it has implications on the glider's endurance and operation. In this work, the effect of two different wing forms, rectangular and tapered, on the hydrodynamic characteristics and dynamic stability of the glider were investigated, to determine the optimal wing form. To determine the hydrodynamic characteristics, tow tank resistance tests were carried out using a model fitted alternately with a rectangular wing and tapered wing. Steady-state CFD analysis was conducted using the hydrodynamic coefficients obtained from the tests, to obtain the lift, drag and hydrodynamic derivatives at different angular velocities. The results show that the rectangular wing provides larger lift forces but with a reduced stability envelope. Conversely, the tapered wing exhibits lower lift force but improved dynamic stability.
Adjuvant Chemotherapy and Prognostic Factors in Stage II Colon Cancer - Izmir Oncology Group Study
Kucukzeybek, Yuksel,Dirican, Ahmet,Demir, Lutfiye,Yildirim, Serkan,Akyol, Murat,Yildiz, Yasar,Bayoglu, Ibrahim Vedat,Alacacioglu, Ahmet,Varol, Umut,Salman, Tarik,Yildiz, Ibrahim,Can, Huseyin,Tarhan, M Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.6
Background: Although adjuvant chemotherapy is a standard treatment in stage III colon cancer, its benefit is not as clear for stage II patients. In this retrospective analysis, we aimed to evaluate the survival of patients with low-risk stage II colon cancer, the efficacy of adjuvant chemotherapy in high-risk stage II colon cancer patients, and prognostic factors in stage II disease. Materials and Methods: One hundred and seventeen patients who were diagnosed with stage II colon cancer between January 2006 and December 2011 were included in the study. Patients were stratified into two groups as being low-risk and high-risk according to risk factors for stage II disease. Adjuvant 5-fluorouracil-based chemotherapy were administered to the patients with risk factors. Results: Ninety-four patients were treated with adjuvant chemotherapy due to high risk factors and 23 were monitored without treatment. Median follow-up time was 43 months. In terms of disease free survival and overall survival, adjuvant chemotherapy did not provide a statistically significant difference. Univariate analysis demonstrated that bowel obstruction was the major risk factor for shortened disease-free survival, while bowel perforation and perineural invasion were both negative prognostic factors for overall survival. Conclusions: The recommendation of adjuvant chemotherapy for stage II colon cancer is not clear. In our study, it was found that adjuvant chemotherapy did not contribute to survival in high-risk stage II patients. Due to the fact that prognosis of stage II patients is good, many more patients will be needed for statistically significant differences in survival. Adjuvant chemotherapy containing 5 fluorouracil is being used to high-risk stage II patients although it is not a standard treatment approach.