Person: SÜRMELİ, MELİH
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Dr. Öğr. Üyesi
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SÜRMELİ
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MELİH
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Publication Necessity and adequacy of near-source factors for not-so-tall fixed-base buildings(Springer, 233 Spring St, New York, Ny 10013 USA, 2015-03) Alhan, Cenk; SÜRMELİ, MELİH; 53191; 175417Nonlinear response history analyses and use of strong ground motion data including near-field effects has become a common practice in both performance based design of tall buildings and design of base-isolated buildings. On the other hand, ordinary buildings are commonly analysed via response spectrum analysis following the rules of conventional seismic codes, most of which do not take near-field effects into account. This study evaluates the necessity and the adequacy of near-source factors for ordinary fixed-base buildings that are not specifically classified as tall, by comparing dynamic responses of 3, 8, and 15-story benchmark buildings obtained via (1) linear time history analyses using 220 record components from 13 historical earthquakes and 45 synthetic earthquake records of different magnitudes and fault distances and (2) response spectrum analyses in accordance with the Turkish Earthquake Code 2007 -representing seismic codes not taking near-field effects into account- and the Uniform Building Code 1997 which takes near-field effects into account via near-source factors that amplify design response spectrum. It is shown that near-source factors are crucial for the safe design of not-so-tall ordinary fixed-base buildings but those defined in UBC97 may still not be adequate for those located in the vicinity of the fault.Publication An adaptive modal pushover analysis procedure (VMPA-A) for buildings subjected to bi-directional ground motions(2018-11) Yüksel, Ercan; SÜRMELİ, MELİH; 175417; 154472A new modal pushover analysis procedure (VMPA-A) is developed and implemented in MATLAB code for three-dimensional buildings subjected to bidirectional ground motions. VMPA-A uses stepwise force patterns to represent changes in the dynamic characteristics because of the accumulated structural damages. The hybrid-spectrum concept is introduced to account for the bidirectional ground motion effects. Due to enactments of the equal displacement rule and the secant stiffness-based linearization process, nonlinear analysis is performed for specific displacement targets without stipulation of full modal capacity curves for each mode. Horizontal components of an earthquake record are considered simultaneously, and the consistency between the force and displacement vectors for each mode is provided. These are the main advantages of the proposed procedure against modal pushover analysis (MPA). An existing 21-story reinforced concrete building is analyzed to exemplify VMPA-A. The response parameters such as displacements, story drifts, internal forces, strains, etc. are discussed by comparing the results of VMPA-A with nonlinear time history analyses, which is accepted as the ‘‘exact solution’’. Though consistent demand estimations are obtained for story drifts, displacements and deformations, some conservative results are obtained for story shears.Publication A capacity curve model for confined clay brick infills(Springer, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands, 2016-03) Özkaynak, Hasan; Yüksel, Ercan; SÜRMELİ, MELİH; 40475; 175417; 154472Experimental studies have proven that clay brick infills, confined with carbon-fiber-reinforced polymers (CFRP) in reinforced concrete (RC) frames, have some advantages in terms of stiffness, strength, energy dissipation capability and damage intensity. Owing to these advantages, existing infill walls in RC frames may be retrofitted with CFRP strips, especially in low-rise buildings in earthquake-prone areas. There is a gap in the literature concerning their behavior model, for use in structural analysis. A piecewise linear capacity curve model called "DUVAR'' is proposed here, which estimates the envelope of force-vs.-displacement hysteresis, depending on the data compiled from the literature and the completed experimental studies. A nonlinear shear spring element is utilized in the model to represent the bare and retrofitted infills. The ultimate shear strength and the corresponding displacement, the ratio of cracking stiffness to initial stiffness, the ratio of ultimate strength to cracking strength, and the ductility ratio are the five key parameters of the model. The model is validated against the experimental results of two sovereign studies. Finally, the model is employed in the performance evaluation of an existing three-story RC building to exemplify its straightforward application.Publication A variant of modal pushover analyses (VMPA) based on a non-incremental procedure(Springer, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands, 2015-11) Yüksel, Ercan; SÜRMELİ, MELİH; 175417; 154472A variant of modal pushover analysis (VMPA) is presented to evaluate the seismic performance of the structures. The suggested procedure is based on an iterative process in which secant stiffnesses are used both at the element level and in the modal response. VMPA diverges from the existing modal pushover analyses for the following reasons: (1) mode compatible adaptive forces are applied to the structure at each iteration step, (2) the application of the equal displacement rule in combination with secant stiffness based linearization in the spectral displacement (S-d)-spectral acceleration (S-a) relation eliminates the necessity to produce a modal capacity diagram for each mode. The displacement controlled algorithm determines the single ordinate of the modal capacity diagram corresponding to the target displacement demand for the nth mode (S-dn_p, S-an_p) by reducing elastic spectral acceleration (S-an_e) to converge to the plastic acceleration (S-an_p). A Matlab based computer program known as DOC3D-v2 is developed to implement the proposed procedure. To verify the success of the suggested procedure, 9- and 20-storey LA SAC buildings are analysed, and the resulting demands are compared with several existing procedures, such as the extended N2, MPA and MMPA, as well as nonlinear time history analyses performed for two different set of acceleration records. VMPA yields enhanced results in terms of storey drifts, especially for the 20-storey LA building, compared with the other methods. Although the storey displacements and drifts are largely consistent with nonlinear time history analysis results, conservative estimates are obtained for the storey shear forces.