Browsing by Author "Ucar, Taner"

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Citation - WoS: 3
Citation - Scopus: 3
Derivation of Yield Force Coefficient for Rc Frames Considering Energy Balance and P-Delta Effects
(Techno-Press, 2021) Ucar, Taner; Merter, Onur
Currently, prominent energy balance concept can efficiently be used to calculate the yield base shear force of structures. Energy balance equation is an additional constraint for the balance of seismic input energy by the energy absorption of the structure. This equation can be defined as the sum of elastic and plastic energies of structural systems using elastic and plastic load-deformation characteristics and the total energy dissipation capacity can finally be equated to the seismic energy demand. The objective of this paper is to present a procedure for the determination of energy-based yield force coefficient of reinforced concrete (RC) frame structures considering P-delta effects. The total of elastic and plastic energies are computed by means of elastic spectral velocity and energy modification factor, which is originally derived for structural systems with geometric nonlinearity. Total inelastic energy of single-degree-of-freedom (SDOF) system is transformed into the total inelastic energy of the multi-degree-of-freedom (MDOF) system using the conversion based on structural dynamics. Plastic energy of MDOF system is formulated after total seismic energy demand is obtained. It is accordingly equated to the total work done by inelastic MDOF structure with P-delta effects and consequently, a dimensionless yield force coefficient is derived. Nonlinear static analyses are performed for selected multi-story RC frames and yield force coefficients are compared with the results of the energy-based formulation. The results show that the proposed formulation taking P-delta effects into account can be effectively used to estimate the yield force coefficient of RC frame structures.
Elastic and Inelastic Input Energy Demands on Structures Under Pulse-Like Ground Motions
(Springer international Publishing Ag, 2025) Ucar, Taner; Merter, Onur
It is well established that pulse-like ground motions typically exhibit distinct characteristics that can substantially influence the seismic demands on structures. During the 2023 Kahramanmaras earthquake, numerous pulse-like ground motion records were collected from various seismic stations. In this study, the elastic input energy spectra are computed for 5% damping considering the selected pulse-like ground motion records of the 2023 Kahramanmaras earthquake. Subsequently, the inelastic input energy spectra of these records are computed for the same damping, considering the specific hysteretic model used in the analysis. A comparison of the inelastic input energy demands on single-degree-of-freedom (SDOF) systems subjected to the selected pulse-like ground motions is presented for various ductility ratios. The ratios of inelastic energy spectral ordinates to elastic energy spectral ordinates are then compared graphically. It is observed that as the ductility ratio increases, the ratio of inelastic to elastic input energies begins to decrease, because inelastic input energy tends to diminish with higher ductility ratios. The results are presented graphically for the selected pulse-like ground motions from the 2023 Kahramanmaras earthquake, revealing fluctuations around the ratio of 1.0 across different periods.
Citation - WoS: 3
Citation - Scopus: 3
An Energy-Based Approach To Determine the Yield Force Coefficient of Rc Frame Structures
(Techno-Press, 2021) Merter, Onur; Ucar, Taner
This paper proposes an energy-based approach for estimating the yield force coefficient of reinforced concrete (RC) frame structures. The procedure is mainly based on the energy balance concept and it considers the nonlinear behavior of structures. First, an energy modification factor is defined to consistently obtain the total energy of the equivalent elastic-plastic single-degree-of-freedom (SDOF) system. Then, plastic energy is formulated as functions of the several structural parameters such as the natural frequency, the strength reduction factor and the yield displacement. Consequently, the plastic energy formulation is derived for multi-degree-of-freedom (MDOF) systems and the yield force coefficient is determined by equating the plastic energy relation to the work needed to push the structure from the yield displacement up to the maximum displacement monotonically. The validity of the energy-based approach is assessed on several RC frame structures by means of nonlinear static pushover analysis considering both material and geometrical nonlinearity. A modification factor is proposed for the yield force coefficient to consider the strain-hardening effects in lateral forces. Moreover, the modified energy-based yield force coefficients are correlated to practical design by using the ductility ratios imposed by Turky Building Earthquake Code and a quite good agreement is observed.
Hysteretic Energy to Input Energy Ratio Spectra of the 2023 Kahramanmaras Earthquake
(Springer international Publishing Ag, 2025) Merter, Onur; Ucar, Taner
Hysteretic energy, closely related to seismic hazard as it quantifies the energy a structure can dissipate through inelastic deformation under earthquake forces, has been chosen as a key parameter in energy-based design approaches due to its direct measurement of energy dissipation during cyclic loadings. A total of 56 distinct pulse-like and non-pulse-like ground motion records from the 2023 Kahramanmaras earthquake are selected. Time history analyses are performed on the selected inelastic single-degree-of-freedom (SDOF) systems, followed by the computation of hysteretic energy spectra for 5% damping. The bilinear hysteretic model is employed to represent the nonlinear cyclic behavior of the structural systems and different ductility ratios are considered. Simultaneously, inelastic input energy spectra are computed for all selected ground motion records. Then, the hysteretic energy to input energy ratio spectra are graphically computed for different ductility ratios, and the mean values are presented along with their standard deviations. It is observed that the hysteretic energy to input energy ratio spectra tend to remain nearly constant beyond a certain period value. In the study, the hysteretic energy to input energy ratio spectra are also generated separately for the selected pulse-like and non-pulse-like ground motions, allowing for the identification of the impact of pulse behavior.
Inelastic Input Energy Spectra of Far-Fault Ground Motions: Influence of Hysteresis Model
(Yildiz Technical Univ, 2022) Merter, Onur; Ucar, Taner
The main purpose of the present study is to compute the input energy spectra of selected far-fault ground motions (GMs) for linear elastic systems, and inelastic systems having a constant ductility ratio. Elastic-perfectly plastic (EPP) and Modified Takeda hysteresis models have been adopted in nonlinear modeling of single-degree-of-freedom (SDOF) systems. Accelerograms of far-fault GMs have been compiled from the Pacific Earthquake Research Center (PEER) database. Linear and nonlinear time history analyses have been performed using the selected GMs records for SDOF systems having a damping ratio of 5%. Input energy spectral ordinates have been computed in terms of energy equivalent velocity. The results have shown that there is no significant difference be tween elastic and inelastic input energy spectral values at intermediate and long periods. However, for short period systems, input energy demand imposed on inelastic systems is generally greater than that of imposed on elastic systems. For short period systems, it can be inferred from the computations of the study that the input energy spectral values obtained using Modified Takeda hysteresis model are greater than those of other models that have been employed. However, input energy spectra for inelastic systems have no significant dependency on hysteresis models, especially for intermediate and long period systems.
Citation - WoS: 7
Citation - Scopus: 8
Predictive Model for Constant-Ductility Energy Factor Spectra of Near- and Far-Fault Ground Motions Based on Gauss-Newton Algorithm
(Taylor & Francis Ltd, 2022) Ucar, Taner; Merter, Onur
Gauss-Newton algorithm is originally applied for estimating constant-ductility energy factor spectra of near- and far-fault ground motions. First, constant-ductility energy factors are clarified, a three-parameter exponential equation relating energy factor to period is proposed and estimation of parameters of the proposed equation by means of Gauss-Newton algorithm is fully demonstrated. A set of 100 both pulse-like and non-pulse like near-fault ground motion records and 112 ordinary far-fault ground motion records is assembled as seismic input. Mean energy factor spectra of the utilized ground motions are preliminarily computed from nonlinear time history analyses for five constant ductility ratios ranging from 2 to 6, and then the same spectra are estimated by Gauss-Newton method. Very strong correlation between the computed and the estimated energy constant-ductility energy factor spectra is observed after few iteration steps.