• Journal of the Korean Data and Information Science Society
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• v.20 no.5
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• pp.913-917
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• 2009

The measures of leverage in linear regression has been extended to nonlinear regression models. We consider several curvature measures of nonlinearity in an estimation situation. The relationship between measures of leverage and statistical curvature are explored in nonlinear regression models. The circumstances under which the Jacobian leverage reduces to a tangent plane leverage are discussed in connection with the effective residual curvature of the nonlinear model.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.2
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• pp.8-14
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• 1996

Key stream generator consisting of several linear feedback shift registers with a nonlinear combining function have been applied in stream cipher system. Most of the papers until now have been focusing on correlation atack and analysis of key stream generator with nonlinear combining function. Given some part of key stream sequences. We can generate identical output sequences with original key stream sequences if the feedback connection and the maximum order of nonlinear combination function are known.

• Steel and Composite Structures
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• v.28 no.6
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• pp.767-778
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• 2018

The purpose of this study is to investigate how a fully restrained bolted beam splice affects the connection behavior as a column-tree connection in steel special moment frames under cyclic loading when located within the plastic hinge zone. The impacts of this attachment in protected zone are observed by using nonlinear finite element analyses. This type of splice connection is designed as slip-critical connection and thereby, the possible effects of slippage of the bolts due to a possible loss of pretension in the bolts are also investigated. The 3D models with solid elements that have been developed includes three types of connections which are the connection having fully restrained beam splice located in the plastic hinge location, the connection having fully restrained beam splice located out of the plastic hinge and the connection without beam splice. All connection models satisfied the requirement for the special moment frame connections providing sufficient flexural resistance, determined at column face stated in AISC 341-16. In the connection model having fully restrained beam splice located in the plastic hinge, due to the pretension loss in the bolts, the friction force on the contact surfaces is exceeded, resulting in a relative slip. The reduction in the energy dissipation capacity of the connection is observed to be insignificant. The possibility of the crack occurrence around the bolt holes closest to the column face is found to be higher for the splice connection within the protected zone.

• Earthquakes and Structures
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• v.12 no.3
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• pp.359-374
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• 2017

The seismic events in Northern Italy, May 2012, have revealed the seismic vulnerability of typical Italian precast industrial buildings. The aim of this paper is to present a seismic fragility model for Italian RC precast buildings, to be used in earthquake loss estimation and seismic risk assessment by comparing two building typologies and three different codes: D.M. 3-03-1975, D.M. 16-01-1996 and current Italian building code that has been released in 2008. Based on geometric characteristics and design procedure applied, ten different building classes were identified. A Monte Carlo simulation was performed for each building class in order to generate the building stock used for the development of fragility curves trough analytical method. The probabilistic distributions of geometry were mainly obtained from data collected from 650 field surveys, while the material properties were deduced from the code in place at the time of construction or from expert opinion. The structures were modelled in 2D frameworks; since the past seismic events have identified the beam-column connection as the weakest element of precast buildings, two different modelling solutions were adopted to develop fragility curves: a simple model with post processing required to detect connection collapse and an innovative modelling solution able to reproduce the real behaviour of the connection during the analysis. Fragility curves were derived using both nonlinear static and dynamic analysis.

• Coupled systems mechanics
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• v.4 no.4
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• pp.337-364
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• 2015

In this paper we present methodology for parameters identification of constitutive model which is able to present behavior of a connection between two members in a structure. Such a constitutive model for frame connections can be cast in the most general form of the Timoshenko beam, which can present three failure modes. The first failure mode pertains to the bending in connection, which is defined as coupled plasticity-damage model with nonlinear softening. The second failure mode is seeking to capture the shearing of connection, which is defined as plasticity with linear hardening and nonlinear softening. The third failure mode pertains to the diffuse failure in the members; excluding it leads to linear elastic constitutive law. Theoretical formulation of this Timoshenko beam model and its finite element implementation are presented in the second section. The parameter identification procedure that will allow us to define eighteen unknown parameters is given in Section 3. The proposed methodology splits identification in three phases, with all details presented in Section 4 through three different examples. We also present the real experimental results. The conclusions are stated in the last section of the paper.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.961-972
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• 2002

Flat plate structures under lateral load are susceptible to the brittle shear failure of plate-column connection. To prevent such brittle failure, strength and ductility of the connection should be ensured. However, according to previous studies, current design methods do not accurately estimate the strength of plate-column connection. In the present study, parametric study using nonlinear finite element analysis was performed for interior connections. Based on the numerical results, a design method for the connection was developed. At the critical sections around the connection coexist flexural moment and shear developed by lateral and gravity loads, and maximum allowable eccentric shear stresses were proposed based on the interactions between the flexural moment and shear, The proposed method can precisely predict the strength of the connection, compared with the current design provisions. The predictability of the proposed method was verified by the comparisons with existing experiments and nonlinear numerical analyses.

• Structural Engineering and Mechanics
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• v.57 no.3
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• pp.507-528
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• 2016

Reduced beam section (RBS) moment resisting connections are among the most economical and practical rigid steel connections developed in the aftermath of the 1994 Northridge and the 1995 Kobe earthquakes. Although the performance of RBS connection has been widely studied, this connection has not been subject to in the skewed conditions. In this study, the seismic performance of dogbone connection was investigated at different angles. The Commercial ABAQUS software was used to simulate the samples. The numerical results are first compared with experimental results to verify the accuracy. Nonlinear static analysis with von Mises yield criterion materials and the finite elements method were used to analyze the behavior of the samples The selected Hardening Strain of materials at cyclic loading and monotonic loading were kinematics and isotropic respectively The results show that in addition to reverse twisting of columns, change in beam angle relative to the central axis of the column has little impact on hysteresis response of samples. Any increase in the angle, leads to increased non-elastic resistance. As for Weak panel zone, with increase of the angle between the beam and the column, the initial submission will take place at a later time and at a larger rotation angle in the panel zone and this represents reduced amount of perpendicular force exerted on the column flange. In balanced and strong panel zones, with increase in the angle between the beam and the central axis of the column, the reduced beam section (RBS), reaches the failure limit faster and at a lower rotation angle. In connection of skewed beam, balanced panel zone, due to its good performance in disposition of plasticity process away from connection points and high energy absorption, is the best choice for panel zone. The ratio of maximum moment developed on the column was found to be within 0.84 to 1 plastic anchor point, which shows prevention of brittle fracture in connections.

• Journal of the Korean Data and Information Science Society
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• v.18 no.1
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• pp.229-235
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• 2007

Measures of leverage in nonlinear regression models are discussed by extending the leverage in linear regression models. The connection between measures of leverage and nonlinearity of the models are explored. Illustrative example based on real data is presented.

• Steel and Composite Structures
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• v.51 no.5
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• pp.487-498
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• 2024

Steel moment resisting frames (MRFs) typically have inter-story drift concentrations at lower stories during earthquakes as found from previous research. Hinged walls (HWs) can be used as structural strengthening components to force the MRFs deform uniformly along the building height. However, large moment demands are often observed on HWs and make the design of HWs non-economical. This paper proposes a method to reduce the moment demand on HWs using a ductile connection system between the MRFs and the HWs. The ductile connection system is designed with a yield strength and energy dissipation capacity, for the purpose of limiting the seismic forces transferred to the HWs and dissipating seismic energy. Nonlinear time history analyses were performed using 10 far-filed earthquakes at maximum considered earthquake level. The analysis results show that the proposed ductile connection system can reduce: (1) seismic moment demands in the HWs; (2) floor accelerations; (3) the connection force between HWs and MRFs.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.2
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• pp.85-92
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• 2024

This study presents code-compliant seismic details by addressing dry mechanical splices for precast concrete (PC) beam-column connections in the ACI 318-19 code. To this end, critical observations of previous test results on precast beam-column connection specimens with the proposed seismic detail are briefly reported in this study, along with a typical reinforced concrete (RC) monolithic connection. On this basis, nonlinear dynamic models were developed to verify seismic responses of the PC emulative moment-resisting frame systems. As the current design code allows only the emulative design approach, this study aims at identifying the seismic performances of PC moment frame systems depending on their emulative levels, for which two extreme cases were intentionally chosen as the non-emulative (unbonded self-centering with marginal energy dissipation) and fully-emulative connection details. Their corresponding hysteresis models were set by using commercial finite element analysis software. According to the current seismic design provisions, a typical five-story building was designed as a target PC building. Subsequently, nonlinear dynamic time history analyses were performed with seven ground motions to investigate the impact of emulation level or hysteresis models (i.e., energy dissipation performance) on system responses between the emulative and non-emulative PC moment frames. The analytical results showed that both the base shear and story drift ratio were substantially reduced in the emulative system compared to that of the non-emulative one, and it indicates the importance of the code-compliant (i.e., emulative) connection details on the seismic performance of the precast building.