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Öğe Bending Capacity of T-Shaped Reinforced Concrete Beams Subjected to High Temperatures(TURKISH CHAMBER CIVIL ENGINEERS, 2010) Erdem, HakanFires, which cause life and material loss, result in a decrease both in strength of concrete and steel and moment capacity of reinforced concrete (RC) members. Reinforced concrete (RC) beams are also affected by heat and a decrease in the moment capacity occurs. To investigate hazardous effects of high temperature, temperature distribution, and internal forces in the investigated cross-sections are required. In the present study, the temperature acting on section surfaces is calculated by the equation given in ISO834. The temperature distribution within the section is defined using Laplace temperature transmission equation and losses in the strengths of materials are determined using the given formulation in Eurocode2. The heat conduction equation is solved by finite difference method, and the temperature distribution in small pieces inside the cross-section is obtained. The tensile and compressive forces are calculated using the decreased strengths of materials in small pieces inside the cross-section. Later, the moment capacity is calculated using equilibrium equations. Additionally, a practical method is suggested to determine temperature-distribution in RC beams with T-section. Efficiency of the suggested practical method and negative effects of high temperature on moment capacity of beams are investigated. According to the obtained results, it is observed that the suggested practical method is quite effective to determine temperature-distribution in T-sections, and bending capacity of the cross-section decreases significantly with increasing fire exposure time.Öğe Effect of insulation materials on the nominal moment capacity in reinforced concrete flat slabs at high temperature(ACADEMIC PUBLICATION COUNCIL, 2010) Erdem, HakanIn this study, the effects of high temperature caused by fire on the nominal moment capacity of reinforced concrete (RC) plane slabs are investigated. The possible improvements on the nominal moment capacities due to the use of isolation materials are also examined. To this end, temperature distribution through RC slab thickness is obtained for two cases: with or without using isolation materials, having various thicknesses and different thermal conductivities. The nominal moment capacity versus temperature is obtained to illustrate the effects of heat on the nominal moment capacities of the RC plane slabs. It is shown that isolation materials having low thermal conductivity are more efficient for durability to fire. The result of the study suggests that the lack of availability of the high temperature durable material is compensated using isolation materials with greater thermal conductivity, provided that the material is thick enough.Öğe Predicting residual moment capacity of thermally insulated RC beams exposed to fire using artificial neural networks(TECHNO-PRESS, 2017) Erdem, HakanThis paper presents a method using artificial neural networks (ANNs) to predict the residual moment capacity of thermally insulated reinforced concrete (RC) beams exposed to fire. The use of heat resistant insulation material protects concrete beams against the harmful effects of fire. If it is desired to calculate the residual moment capacity of the beams in this state, the determination of the moment capacity of thermally insulated beams exposed to fire involves several consecutive calculations, which is significantly easier when ANNs are used. Beam width, beam effective depth, fire duration, concrete compressive and steel tensile strength, steel area, thermal conductivity of insulation material can influence behavior of RC beams exposed to high temperatures. In this study, a finite difference method was used to calculate the temperature distribution in a cross section of the beam, and temperature distribution, reduction mechanical properties of concrete and reinforcing steel and moment capacity were calculated using existing relations in literature. Data was generated for 336 beams with different beam width (by), beam account height (h), fire duration (t), mechanical properties of concrete (f(cd)) and reinforcing steel (f(yd)), steel area (A), insulation material thermal conductivity (kinsulation). Five input parameters (b(w), h, f(cd),f(yd) A(s) and k(insulation)) were used in the ANN to estimate the moment capacity (M-r). The trained model allowed the investigation of the effects on the moment capacity of the insulation material and the results indicated that the use of insulation materials with the smallest value of the thermal conductivities used in calculations is effective in protecting the RC beam against fire.Öğe Predicting the moment capacity of RC beams exposed to fire using ANNs(ELSEVIER SCI LTD, 2015) Erdem, HakanThis research investigates the implementation of artificial neural networks (ANNs) to estimate the moment capacity (M-r) of reinforced concrete (RC) beams under rising temperatures due to fire. 280 data were obtained for ANN model. Input layer in ANN model consisted of eight input parameters; the beam width (b(w)), the beam depth (d), the ratio of (b(w)/d), distance from the beam edge to the center of the rebar (d'), the ratio of (d'/d), fire time (t(exposure)), the reinforcement area (A(st)), and concrete compressive strength (f(c)). It is shown that the ANN model can be used to predict the M-r of RC beams exposed to fire with high accuracy. The predicted M-r by ANN are consistent with the results obtained using M-r equation. It was observed from the results the ANN model reduces the computational complexity problem in determining M-r. Consequently, the ANN model was used to examine the effects of the inputs parameters on M-r. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Prediction of the moment capacity of reinforced concrete slabs in fire using artificial neural networks(ELSEVIER SCI LTD, 2010) Erdem, HakanIn this study, the application of artificial neural networks (ANN) to predict the ultimate moment capacity of reinforced concrete (RC) slabs in fire is investigated. An ANN model is built, trained and tested using 294 data for slabs exposed to fire. The data used in the ANN model consists of seven input parameters, which are the distance from the extreme fiber in tension to the centroid of the steel on the tension side of the slab (d'), the effective depth (d), the ratio of previous parameters (d'/d), the area of reinforcement on the tension face of the slab (A(s)), the fire exposure time (t). the compressive strength of the concrete (f(cd)), and the yield strength of the reinforcement (f(yd)). It is shown that ANN model predicts the ultimate moment capacity (M(u)) of RC slabs in fire with high degree of accuracy within the range of input parameters considered. The moment capacities predicted by ANN are in line with the results provided by the ultimate moment capacity equation. These results are important as ANN model alleviates the problem of computational complexity in determining M(u). (C) 2009 Elsevier Ltd. All rights reserved.Öğe The dynamic instability of FG orthotropic conical shells within the SDT(Techno-Press, 2017) Sofiyev, Abdullah H.; Zerin, Zihni; Allahverdiev, Bilender P.; Hui, David; Turan, Ferruh; Erdem, HakanThe dynamic instability of truncated conical shells subjected to dynamic axial load within first order shear deformation theory (FSDT) is examined. The conical shell is made from functionally graded (FG) orthotropic material. In the formulation of problem a dynamic version of Donnell's shell theory is used. The equations are converted to a Mathieu-Hill type differential equation employing Galerkin's method. The boundaries of main instability zones are found applying the method proposed by Bolotin. To verify these results, the results of other studies in the literature were compared. The influences of material gradient, orthotropy, as well as changing the geometric dimensions on the borders of the main areas of the instability are investigated.Öğe Yangının mod birleştirme analizi sonuçlarına etkisi(2024) Erdem, Hakan; Erdem, EmineYapılarda meydana gelebilecek yangın nedeniyle zamana bağlı olarak artan yüksek sıcaklıklar oluşur. Betonarme yapıları oluşturan elemanların rijitlikleri ve kütleleri de bu yüksek sıcaklık nedeniyle etkilenir ve azalır. Yapının deprem kuvvetlerinin analizinde kullanılan yapının titreşim periyotları ve buna bağlı olarak hesaplanan birçok değer değişir. TS-EN 1992 1-2’de yüksek sıcaklığın malzeme özellikleri üzerindeki etkileri için verilen bağıntılar kullanılarak kütle ve rijitlik matrisleri yeniden oluşturulması gerekir. Bu çalışmada yapının kütlesi ve elastisite modülündeki sıcaklığa bağlı değişimler dikkate alınarak seçilen bir betonarme yapının birinci periyotlarındaki, yatay elastik tasarım spektral ivmelerindeki, taban kesme kuvvetlerindeki ve seçilen bir düğüm noktası için yer değiştirmelerindeki değişimler incelenmiştir.
