• Steel and Composite Structures
• /
• v.20 no.3
• /
• pp.469-486
• /
• 2016

Codes EN 1993 and EN 1994 require to take into account actual joint characteristics in the global analysis. In order to implement the semi-rigid connection effects in frame design, knowledge of joint rotation characteristics ($M-{\phi}$ relationship), or at least three basic joint properties, namely the moment resistance $M_R$, the rotational stiffness $S_j$ and rotation capacity, is required. To avoid expensive experimental tests many methods for predicting joint parameters were developed. The paper presents a comprehensive analytical model that has been developed for predicting the moment resistance $M_R$, initial stiffness $S_{j.ini}$ and rotation capacity of the minor axis, composite, semi-rigid joint. This model is based on so-called component method included in EN 1993 and EN 1994. Comparison with experimental test results shows that a quite good agreement was achieved. A computer program POWZ containing proposed procedure were created. Based on the numerical simulation made with the use of this program and applying regression analysis, simplified equations for main joint properties were also developed.

• Structural Engineering and Mechanics
• /
• v.39 no.1
• /
• pp.147-168
• /
• 2011

To ensure safety and long term performance, structural control has rapidly matured over the past decade into a viable means of limiting structural responses to strong winds and earthquakes. Nonlinear response history analysis requires rigorous procedure to compute seismic demands. Therefore the simplified nonlinear analysis procedures are useful to determine performance of the structure. In this investigation, application of improved capacity demand diagram method in the control of structural system is presented for the first time. Developed pole assignment method (DPAM) in structural systems control is introduced. Genetic algorithm (GA) is employed as an optimization tool for minimizing a target function that defines values of coefficient matrices providing the placement of actuators and optimal control forces. The ground acceleration is modified under induced control forces. Due to this, performance of structure based on improved nonlinear demand diagram is selected to threshold of nonlinear behavior of structure. With small energy consumption characteristics, semi-active devices are especially attractive solutions for limiting earthquake effects. To illustrate the efficiency of DPAM, a 30-story steel moment frame structure employing the semi-active control devices is applied. In comparison to the widely used linear quadratic regulation (LQR), the DPAM controller was shown to be just as effective and better in the reduction of structural responses during large earthquakes.

• Structural Engineering and Mechanics
• /
• v.29 no.1
• /
• pp.17-35
• /
• 2008

Neglecting the real joint behaviour in frame analysis may result in unrealistic predictions of the response and reliability of steel frames. The reliability of the prediction of main joint properties according to the component method (Eurocode 3-Part 1.8) still remains open to further investigation. The first step toward the solution is to compare the theoretical expressions given in EN 1993-1-8 and the experimental results. With that goal in mind six nominally the same, but really different specimens of welded beam-to-column joints subjected to static load were tested. The specimens present a combination of nominally identical structural elements produced in different European mills. This paper provides these tests, as well as their detailed evaulation and interpretation. All three joint structural properties (rotational stiffness, moment resistance and rotation capacity) have been considered. Four models for determining the plastic resistance out of experimental Mj-${\phi}$ curves have been applied. The results that have been discussed in detail, point to the fact that EN 1993-1-8 underestimates the real structural properties of the tested type of joint, as well as to the conclusion that detailed research of this problem needs to be conducted using the probabilistic reliability methods.

• Smart Structures and Systems
• /
• v.4 no.6
• /
• pp.809-828
• /
• 2008

Real-time hybrid testing is an attractive method to evaluate the response of structures under earthquake loads. The method is a variation of the pseudodynamic testing technique in which the experiment is executed in real time, thus allowing investigation of structural systems with time-dependent components. Real-time hybrid testing is challenging because it requires performance of all calculations, application of displacements, and acquisition of measured forces, within a very small increment of time. Furthermore, unless appropriate compensation for time delays and actuator time lag is implemented, stability problems are likely to occur during the experiment. This paper presents an approach for real-time hybrid testing in which time delay/lag compensation is implemented using model-based response prediction. The efficacy of the proposed strategy is verified by conducting substructure real-time hybrid testing of a steel frame under earthquake loads. For the initial set of experiments, a specimen with linear-elastic behavior is used. Experimental results agree well with the analytical solution and show that the proposed approach and testing system are capable of achieving a time-scale expansion factor of one (i.e., real time). Additionally, the proposed method allows accurate testing of structures with larger frequencies than when using conventional time delay compensation methods, thus extending the capabilities of the real-time hybrid testing technique. The method is then used to test a structure with a rate-dependent energy dissipation device, a magnetorheological damper. Results show good agreement with the predicted responses, demonstrating the effectiveness of the method to test rate-dependent components.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2006.05a
• /
• pp.1005-1008
• /
• 2006

In this paper, we provide data of wireless environment in indoor for Bluetooth and wireless LAN systems. To accurately measure transmission characteristic for influence of the indoor wall, we used radiation measurement system with antennas. And various structure and material of the indoor wall are measured. Results of the measurement show that the attenuation of power is about $1\sim3dB$ for cement wall(25cm). In the case of cement wall with steel frame, the attenuation of power was increased using horizontal polarization but was not affect using vertical polarization.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.19 no.5
• /
• pp.112-119
• /
• 2015

In this paper, the strengthening method was proposed for improving the seismic performance of the vulnerable structural frames. To improve the brittle characteristics of columns, aramid fiber sheet was used for the lateral confinement of columns. And to introduce the energy dissipation capacity, a steel damper with S-shaped struts was installed. By making the unreinforced and reinforced specimens with full size specimens were evaluated for lateral load resistance capacity. It was confirmed the strengthening effects by the evaluation of failure shape, strength, stiffness degradation, and energy dissipation capacity. Also from the FE analysis using ABAQUS, the hysteretic behavior of the specimens were predicted and evaluated.

• Journal of the Korean Society for Precision Engineering
• /
• v.33 no.12
• /
• pp.965-970
• /
• 2016

Fuel used in the steel metallurgy industry is stored in huge stage systems called SILO. Fuel is released by RDM (Rotary Discharge Machine), at the place of utilization. RDM is located in the Silo, and is constituted of a main frame, driving part, discharging part and control part. RDM is combined to a direct motion on the rail in tunnel, having a rotary motion enabled by a motor. In this paper, we calculate the theoretical discharging capacity of RDM to confirm the correlation between design element and discharging capacity of RDM. Also, through structure analysis, we confirm the vulnerable point of RDM when it discharges the storage materials. We hope to apply these results to design a more efficient RDM.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.7 no.4
• /
• pp.201-208
• /
• 2003

The Hybrid Wall System(HWS) building composed of center core reinforced concrete walls and exterior steel frame has open space around the center core walls. It is necessary to develop design methodologies for the HWS building that the coupled shear walls withstand the most of lateral load and expect the most energy dissipation at the coupling beams and at wall foots. Major factors considered in this paper are connection type of coupling beams and scale of story. The studies of the system are investigated in terms of shear force, overturning moment, maximum lateral displacement, story drift ratio, and dynamical characteristics under the action of vertical and lateral forces such as wind and seismic loads.

• Earthquakes and Structures
• /
• v.13 no.4
• /
• pp.337-351
• /
• 2017

In the present study a capacity spectrum method based on constant ductility inelastic spectra to estimate the seismic performance of structures equipped with elastic viscous dampers is presented. As the definition of the structures' effective damping, due to the damping system, is necessary, an alternative method to specify the effective damping ratio ${\xi}eff$ is presented. Moreover, damping reduction factors (B) are introduced to generate high damping elastic demand spectra. Given the elastic spectra for damping ratio ${\xi}eff$, the performance point of the structure can be obtained by relationships that relate the strength demand reduction factor (R) with the ductility demand factor (${\mu}$). As such expressions that link the above quantities, known as R - ${\mu}$ - Τ relationships, for different damping levels are presented. Moreover, corrective factors (Bv) for the pseudo-velocity spectra calculation are reported for different levels of damping and ductility in order to calculate with accuracy the values of the viscous dampers velocities. Finally, to evaluate the results of the proposed method, the whole process is applied to a four-storey reinforced concrete frame structure and to a six-storey steel structure, both equipped with elastic viscous dampers.

• Steel and Composite Structures
• /
• v.29 no.4
• /
• pp.483-491
• /
• 2018

Timoshenko beam model is widely exploited in the literature to examine the mechanical behavior of stubby beam-like components. Timoshenko beam theory is well-known to require the shear correction factor in order to recognize the nonuniform shear distribution at a section. While a variety of shear correction factors are appeared in the literature so far, there is still no consensus on the most appropriate form of the shear correction factor. The Saint-Venant's flexure problem is first revisited in the frame work of the classical theory of elasticity and a highly accurate approximate closed-form solution is presented employing the extended Kantorovich method. The resulted approximate solution for the elasticity field is then employed to introduce two shear correction factors consistent with the Cowper's and energy approaches. The mathematical form of the proposed shear correction factors are then simplified and compared with the results available in the literature over an extended range of Poisson's and aspect ratios. The proposed shear correction factors do not exhibit implausible issue of negative values and do not result in numerical instabilities too. Based on the comprehensive discussion on the shear correction factors, a piecewise definition of shear correction factor is introduced for rectangular cross-sections having excellent agreement with the numerical results in the literature for both shallow and deep cross-sections.