• Structural Engineering and Mechanics
• /
• v.17 no.2
• /
• pp.187-201
• /
• 2004

A shaking table test on a three-story one-bay steel frame model with metallic yield dampers and their parallel connection with oil dampers is carried out to study the dynamic characteristics and seismic performance of the energy dissipation system. It is found from the test that the combined energy dissipation system has favorable reducing vibration effects on structural displacement, and the structural peak acceleration can not evidently be reduced under small intensity seismic excitations, but in most cases the vibration reduction effect is very good under large intensity seismic excitations. Test results also show that stiffness of the energy dissipation devices should match their damping. Dynamic analysis method and mechanics models of these two dampers are proposed. In the analysis method, the force-displacement relationship of the metallic yield damper is represented by an elastic perfectly plastic model, and the behavior of the oil damper is simulated by a velocity and displacement relative model in which the contributions of the oil damper to the damping force and stiffness of the system are considered. Validity of the analytical model and the method is verified through comparison between the results of the shaking table test and numerical analysis.

• Journal of the Korean Geotechnical Society
• /
• v.26 no.3
• /
• pp.47-57
• /
• 2010

Yield seismic coefficient plays an important role in the estimation of permanent displacement of a soil slope subjected to earthquake using Newmark's sliding block theory. However, yield seismic coefficients currently used in practices are not mechanically rigorous since most of them are estimated using limit equilibrium methods considering equilibrium condition only. Therefore, estimation of permanent displacement of a soil slope based on existing yield seismic coefficient may cause problems. Limit analysis estimating the range of mechanically rigorous solution is thought to be effective in evaluating the validity of existing yield seismic coefficient. In this study, a simple stability chart for yield seismic coefficient useful in practices is proposed by considering various slope conditions including stability number, slope inclination, strength parameters, etc.

• International Journal of Concrete Structures and Materials
• /
• v.11 no.2
• /
• pp.275-284
• /
• 2017

A formula to estimate the yield displacement observed in the pushover analysis of coupled wall lateral force-resisting systems is presented. The estimate is based on the results of an analytical study of coupled walls ranging from 8 to 20 stories in height, with varied amounts of reinforcement in the reinforced concrete coupling beams and walls, subjected to first-mode pushover analysis. An example illustrates the application of these estimates to the performance-based seismic design of coupled walls.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.11 no.6
• /
• pp.53-61
• /
• 2007

This study investigates the effect of site class, post-yield stiffness ratio, damping ratio, yield-strength reduction factor, and natural period on inelastic displacement ratio of bilinear SDF systems located at the sites classified as NEHRP site class B,C,D. The previous studies developed inelastic displacement ratio using equal displacement rule in the intermediate and long period range. But, this approximation overestimates the inelastic displacement ratio. Furthermore, inelastic displacement ratio has not been developed for the systems having a damping ratio less than 5%. This study conducts nonlinear regression analysis for proposing equations for calculating median and deviation of the inelastic displacement ratio of the bilinear SDOF system having damping ratios ranging from 0 to 20%. Using median and deviation of the inelastic displacement ratio, probabilistic inelastic displacement ratio is estimated, which can be used for performance-based seismic evaluation.

• Journal of Veterinary Clinics
• /
• v.36 no.1
• /
• pp.68-73
• /
• 2019

We determined the risk factors for displacement of the abomasum (DA), and the relationships between DA and postpartum disorders, milk yield, and reproductive performance in dairy cows. Initially, we identified the risk factors for DA using data regarding cow health and calving season from 2,208 lactations. Then, we compared the incidence of postpartum disorders, culling, death, and reproductive performance between cows with DA and their control herdmates (each n = 57). In addition, serum metabolites concentrations and milk yield were compared between cows with DA and controls (each n = 33). Ketosis (odds ratio [OR] = 9.27, p < 0.0001) and twin calves (p = 0.06) increased the risk of DA. Cows with a parity of three had a higher risk (OR = 5.23, p < 0.01) of DA than primiparous cows. Serum total cholesterol concentration was lower but non-esterified fatty acid, ${\beta}-hydroxybutyrate$, and alanine aminotransferase concentrations were higher after calving in cows with DA than in controls (p < 0.05). The removal rate from the herd by 2 months after calving was higher (p < 0.05) but milk yield 1 and 2 months after calving (p < 0.01) and the rate of first insemination by 150 days postpartum were lower (hazard ratio = 0.49, p < 0.05) in cows with DA than controls. In conclusion, higher parity, twin calves, and ketosis are risk factors for DA in dairy cows, which is associated with a higher removal rate from the herd, lower milk yield, a longer calving to first insemination interval, and unfavorable levels of metabolites related to energy and liver function.

• Earthquakes and Structures
• /
• v.12 no.6
• /
• pp.713-723
• /
• 2017

Steel plate shear walls (SPSWs) are effective lateral systems which have high initial stiffness, appropriate ductility and energy dissipation capability. Recently, steel plate shear walls with low yield point strength (LYP), were introduced and they attracted the attention of designers. Structures with this new system, besides using less steel, are more stable. In the present study, the effects of plates with low yield strength on the seismic design parameters of steel frames with steel plate shear walls are investigated. For this purpose, a variety of this kind of structures with different heights including the 2, 5, 10, 14 and 18-story buildings are designed based on the AISC seismic provisions. The structures are modeled using ANSYS finite element software and subjected to monotonic lateral loading. Parameters such as ductility (${\mu}$), ductility reduction ($R_{\mu}$), over-strength (${\Omega}_0$), displacement amplification ($C_d$) and behavior factor (R) of these structures are evaluated by carrying out the pushover analysis. Analysis results indicate that the ductility, over-strength and behavior factors decrease by increasing the number of stories. Also, the displacement amplification factor decreases by increasing the number of stories. Finally, the results were compared with the suggestions provided in the AISC code for steel plate shear walls. The results indicate that the values for over-strength, behavior and displacement amplification factors of LYP steel plate shear wall systems, are larger than those proposed by the AISC code for typical steel plate shear wall systems.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.281-284
• /
• 2008

Performance evaluation exposing the performance of structure is affected by the material and structural characteristics. these should be necessary for the analysis about the effect of structure performance. Thus, to evaluate the structural performance affected the material properties and structural characteristics, firstly it is conducted the eigenvalues analysis and non-linear static analysis of the structure, secondly it is analyzed the performance influence factor of the structure. The performance influence factors affecting the performance of structure divided into five classes(strength of concrete, longitudinal and transverse reinforcement, aspect ratio, axial force). From the result of analysis about the change of performance influence factor, the more the strength of concrete is increasing, the more the maximum shear force is increasing and the yield displacement is not changed, the more longitudinal reinforce is increasing, the more yield displacement and the maximum basis shear force is increasing, the more the transverse reinforce is increasing, the change of maximum basis shear force is trivial. The yield displacement of structure is increasing and the maximum basis shear force is decreasing by increasing the aspect ratio, the more the axial force increases, the more yield displacement and maximum basis shear force decease.

• Journal of Korean Association for Spatial Structures
• /
• v.13 no.1
• /
• pp.69-77
• /
• 2013

This study is the research appling the representative Displacement-Based Design which is the basic concept of Direct Displacement Based Design proposed by Chopra and Goel to original Reinforced Concrete moment frame and determining the thickness of retrofit Steel Jacket about the Maximum design ground acceleration, and developing the more improved Algorithm as well as program by the Retrofit Design method and Nonlinear analysis by the Performance design method before and after reinforcement appling the determined retrofit thickness. It also shows the result of the seismic performance improvement which is the ratio of seismic performance appreciation result yield displacement 19%, yield strength ratio 24%, displace ductility ratio the maximum 27% comparing Multi degree of freedom, column member of Reinforced Concrete with the performance improvement column member considering the thickness of the determined Steel Jacket. The developed Algorithm and program are easy to apply seismic design and application to the original Reinforced Concrete building, at the same time, it applicate to display well the design result of Target displacement performance level about nonlinear behavior.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2004.05a
• /
• pp.148-151
• /
• 2004

Mechanical properties such as Young's modulus and hardness of thin film in coated steel are difficult to determine by nano-indentation from the conventional analysis using the load-displacement curve. Therefore, an analysis of the nano-indentation loading curve was used to determine the Young's modulus, hardness and strain hardening exponent. A new method is recently being developed for plasticity properties of materials from nano-indentation. Elastic modulus of the thin films shows relatively small influence whereas yield strength and strain hardening are found to have significant effect on measured data. The load-displacement behavior of material tested with a Berkovich indenter and nano-indentation continuous stiffness method is used to measure the modulus and hardness through thin films.

• Transactions of Materials Processing
• /
• v.13 no.8
• /
• pp.731-737
• /
• 2004

Mechanical properties such as Young's modulus and hardness of thin film in coated steel are difficult to determine by nano-indentation from the conventional analysis using the load-displacement curve. Therefore, an analysis of the nano-indentation loading-unloading curve was used to determine the Young's modulus, hardness. A new method is recently being developed for elastic-plastic properties of materials from nano-indentation. Elastic modulus of the thin films shows relatively small influence whereas yield strength is found to have significant effect on measured data. The load-displacement curves of material tested with a Berkovich indenter and nano-indentation continuous stiffness method is used to measure the modulus and hardness through thin films, and then these are computed using the analysis procedure. The developed neural networks apply also to obtain reliable mechanical properties.