• Steel and Composite Structures
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• v.43 no.5
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• pp.565-579
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• 2022

This study investigated the yielding capacity and performance of seismic dampers constructed with steel ring plates using numerical and analytical approaches. This study aims to provide an analytical relationship for estimating the yielding capacity and initial stiffness of steel ring dampers. Using plastic analysis and considering the mechanism of plastic hinge formation, a relation has been obtained for estimating the yielding capacity of steel ring dampers. Extensive parametric studies have been carried out using a nonlinear finite element method to examine the accuracy of the obtained analytical relationships. The parametric studies include investigating the influence of the length, thickness, and diameter of the ring of steel ring dampers. To this end, comprehensive verification studies are performed by comparing the numerical predictions with several reported experimental results to demonstrate the numerical method's reliability and accuracy. Comparison is made between the hysteresis curves, and failure modes predicted numerically or obtained/observed experimentally. Good agreement is observed between the numerical simulations and the analytical predictions for the yielding force and initial stiffness. The difference between the numerical models' ultimate tensile and compressive capacities was observed that average of about 22%, which stems from the performance of the ring-dampers in the tensile and compression zones. The results show that the steel ring-dampers are exhibited high energy dissipation capacity and ductility. The ductility parameters for steel ring-damper between values were 7.5 to 4.1.

• Earthquakes and Structures
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• v.23 no.6
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• pp.527-534
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• 2022

EDCC (Eco-Friendly Ductile Cementitious Composites) is a recently created class of engineered cementitious composites that exhibit extremely high ductility and elastoplastic behavior under pure tension. EDCC contains reduced amounts of cement and very large volumes of fly ash. Due to these properties, EDCC has become one of the solutions to use in seismic upgrading. This paper discloses previous studies and research that discussed the seismic upgrading of unreinforced, non-grouted, unconfined, and non-load bearing masonry walls which are called URM infill walls using the EDCC technique. URM infill wall is one of the weak links in the building structure to withstand the earthquake waves, as the brittle behavior of the URM infill walls behaves poorly during seismic events. The purpose of this study is to fill a knowledge gap about the theoretical and experimental ways to use the EDCC in URM infill walls. The findings reflect the ability of the EDCC to change the behavior from brittle to ductile to a certain percentage behavior, increasing the overall drift before collapse as it increases the energy dissipation, and resists significant shaking under extensive levels with various types and intensities.

• Steel and Composite Structures
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• v.47 no.3
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• pp.375-382
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• 2023

The H-shaped steel beam is popular due to its ease of manufacturing and connection to the column. This profile, which is used as a shallow beam, needs the high weak-axis bending stiffness and torsional stiffness to meet the overall stability. Achieving the local beam flange stability, bearing capacity, bending stiffness, and torsional requirements need a great thickness and width of the beam flange, which causes, which will cause more uneconomical structural design. So, the box-section beam is the ideal alternative. However, the current design specifications do not have design rules for the bolt-and-welded connection of the box-section beam and box-section column. The paper proposes a novel bolt-and-welded connection of the box-section beams and box-section columns based on a high-rise structural design scheme. Three connection models, BASE, WBF, and RBS, are analyzed under cyclic loading in ABAQUS software. The failure modes, hysteresis response, bearing capacity, ductility, plastic rotation angle, energy dissipation, and stiffness degradation of all models are determined and compared. Compared with the other two models, the model WBF exhibited excellent seismic performance, ductility, and plastic rotation ability. Finally, model WBF was chosen as the connection scheme used in the project design.

• Computers and Concrete
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• v.32 no.2
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• pp.173-184
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• 2023

In this study, mechanical, flexural post-cracking, and torsional behaviors of recycled steel fiber-reinforced concrete (RSFRC) incorporating steel fibers obtained from recycling of waste tires were investigated. Initially, three concrete mixes with different fiber contents (0, 40, and 80 kg/m³) were designed and tested in fresh and hardened states. Subsequently, the flexural post-cracking behaviors of RSFRCs were assessed by conducting three-point bending tests on notched beams. It was observed that recycled steel fibers improve the post-cracking flexural behavior in terms of energy absorption, ductility, and residual flexural strength. What's more, torsional behaviors of four RSFRC concrete beams with varying reinforcement configurations were investigated. The results indicated that RSFRCs exhibited an improved post-elastic torsional behaviors, both in terms of the torsional capacity and ductility of the beams. Additionally, numerical analyses were performed to capture the behaviors of RSFRCs in flexure and torsion. At first, inverse analyses were carried out on the results of the three-point bending tests to determine the tensile functions of RSFRC specimens. Additionally, the applicability of the obtained RSFRC tensile functions was verified by comparing the results of the conducted experiments to their numerical counterparts. Finally, it is noteworthy that, despite the scatter (i.e., non-uniqueness) in the aspect ratio of recycled steel fiber (as opposed to industrial steel fiber), their inclusion contributed to the improvement of post-cracking flexural and torsional capacities.

• Steel and Composite Structures
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• v.45 no.2
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• pp.193-204
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• 2022

The need for establishing the contribution of pultruded FRP encasements and additional FRP wraps around these encasements to the shear strength and load-deflection behavior of reinforced concrete beams is the main motivation of the present study. This paper primarily focuses on the effect of additional wrapping around the composite beam on the flexural and shear behavior of the pultruded GFRP (Glass Fiber Reinforced Polymer) beams infilled with reinforced concrete, taking into account different types of failure according to av/H ratio (arch action, shear-tension, shear-compression and pure bending). For this purpose, nine hybrid beams with variable shear span-to-depth ratio (av/H) were tested. Hybrid beams with 500 mm, 1000 mm, and 1500 mm lengths and cross-sections of 150x100 mm and 100x100 mm were tested under three-point and four-point loading. Based on the testing load-displacement relationship, ductility ratio, energy dissipation capacity of the beams were evaluated with comprehensive macro damage analysis on pultruded GFRP profile and GFRP wrapping. The GFRP wraps were established to have a major contribution to the composite beam ductility (90-125%) and strength (40-75%) in all ranges of beam behavior (shear-dominated or dominated by the coupling of shear and flexure). The composite beams with wraps were showns to reach ductilities and strength values of their counterparts with much greater beam depth.

• Structural Engineering and Mechanics
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• v.84 no.2
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• pp.269-283
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• 2022

In this paper, a particular type of all-steel HSS brace members with a locally reduced cross-sectional area was experimentally and numerically investigated. The brace member was strengthened against local buckling with inner and outer boxes in the reduced area. Four single-span braced frames were tested under cyclic lateral loadings. Specimens included a simple steel frame with a conventional box-shaped brace and three other all-steel reduced section buckling-restrained braces. After conducting the experimental program, numerical models of the proposed brace were developed and verified with experimental results. Then the length of the proposed fuse was increased and its effect on the cyclic behavior of the brace was investigated numerically. Eventually, the brace was detailed with a fuse-to-brace length of 30%, as well as the cross-sectional area of the fuse-to-brace of 30%, and the cyclic behavior of the system was studied numerically. The study showed that the proposed brace is stable up to a 2% drift ratio, and the plastic cumulative deformation requirement of AISC (2016) is easily achieved. The proposed brace has sufficient ductility and stability and is lighter, as well as easier to be fabricated, compared to the conventional mortar-filled BRB and all-steel BRB.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.2 s.54
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• pp.206-214
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• 2009

Due to its outstanding feature, FRP is used widely for the material of strengthening in USA and Japan recently, and there have been active researches in korea as well. This study evaluates the behavior and ductility of each structure experiment using EBR and NSMR strengthening method with different AFRP types and strengthening area. There was the biggest increase in the load when the strengthening area is expanded showing a brittle aspect, and eventually the immature failure occurred. With regard to the methods, it is found that the NSMR method is more effective to strengthen the structure, and the uneven surface causes ductile failure.

• Earthquakes and Structures
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• v.27 no.3
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• pp.165-176
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• 2024

In this study, a direct Lagrangian-based three-dimensional computational procedure is developed to evaluate the seismic performance of reinforced concrete liquid-containing circular tanks (RC-LCT). In this approach, fluid-structure interaction (FSI), material nonlinearity, and liquid-structure large deformations are formulated realistically. Liquid is modeled using Mie-Grüneisen equation of state (EOS) in compressible form considering the convective and impulsive motions of fluid. The developed numerical framework is validated based on a previous study. Further, nonlinear analyses are carried out to assess the seismic performance of RC-LCT with various diameter-to-liquid height ratios ranging from 2.5 to 4.0. Based on observations, semi-deep tanks (i.e., D/H_l=2.5) show low collapse ductility due to their shear failure mode while shallow tanks (i.e., D/H_l=4.0) behave in a more ductile manner due to their dominant wall membrane action. Furthermore, the semi-deep tanks provide the least over-strength and ductility due to their catastrophic failure with little energy dissipation. This study shows that LCTs can be categorized as between immediately operational and life safety levels and therefore a drift limiting criterion is necessary to prevent probable damages during earthquakes.

• Structural Engineering and Mechanics
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• v.32 no.5
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• pp.587-608
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• 2009

Modern earthquake-resistant design aims to isolate architectural precast concrete panels from the structural system so as to reduce the interaction with the supporting structure and hence minimize damage. The present study seeks to maximize the cladding-structure interaction by developing an energy-dissipating cladding system (EDCS) that is capable of functioning both as a structural brace, as well as a source of energy dissipation. The EDCS is designed to provide added stiffness and damping to buildings with steel moment resisting frames with the goal of favorably modifying the building response to earthquake-induced forces without demanding any inelastic action and ductility from the basic lateral force resisting system. Because many modern building facades typically have continuous and large openings on top of the precast cladding panels at each floor level for window system, the present study focuses on spandrel type precast concrete cladding panel. The preliminary design of the EDCS was based on existing guidelines and research data on architectural precast concrete cladding and supplemental energy dissipation devices. For the component-level study, the preliminary design was validated and further refined based on the results of nonlinear finite element analyses. The stiffness and strength characteristics of the EDCS were established from a series of nonlinear finite element analyses and are discussed in detail in this paper.

• Proceedings of the Korean Nuclear Society Conference
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• 2004.10a
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• pp.911-912
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• 2004

1. Cathodic hydrogen charging considerably reduced the tensile ductility of ODS steels and a 9Cr-2W RMS. The hydrogen embrittlement of ODS steels was strongly affected by specimen sampling orientation, showing significant embrittlement in the T-direction. This comes from the microstructural anisotropy caused by elongated grains of ODS steels in L-direction. 2. The ODS steels contained a higher concentration of hydrogen than 9Cr-2W RMS at the same cathodic charging condition, and the critical hydrogen concentration required to transition from ductile to brittle fracture was in the range of $10{\sim}12$ wppm, which approximately 10 times larger than that of a 9Cr-2W martensitic steel. 3. The ODS steels showed a typical ductile to brittle transition behavior and it strongly depended on the specimen sampling direction, namely L- and T-direction. In T-direction, the SP-DBTT was about 170 L, irrespective of the ODS materials, and L-direction showed a lower SP-DBTT than that of T-direction.