• International Journal of High-Rise Buildings
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• v.10 no.2
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• pp.93-97
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• 2021

Supplementary damping systems, such as tuned mass dampers (TMDs) and tuned sloshing dampers (TSDs) - also known as tuned liquid dampers (TLDs) - have been successfully employed to reduce building motion during wind events. A design of a damping system consisting of a TMD and two TSDs performing in unison has been developed for a tall building in Taiwan to reduce wind-induced motion. The architecturally exposed TMD will also be featured as a tourist attraction. The dual-purpose TSD tanks will perform as fire suppression water storage tanks. Linearized equivalent mechanical TSD and TMD models are coupled to the structure to simulate the multi-degree of freedom system response. Frequency response curves for the structure with and without the damping system are created to evaluate the performance of the damping system. The performance of the combined TMD-TSD system is evaluated against a conventional TMD system by computing the effective damping produced by each system. The proposed system is found to have superior performance in acceleration reduction. The combined TMD-TSD system is an effective and affordable means to reduce the wind-induced resonant response of tall buildings.

• Journal of Aerospace System Engineering
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• v.15 no.1
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• pp.47-55
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• 2021

When an abnormal landing occurs, aircraft structures should be designed to guarantee occupants survivability without preventing egress. To find out fire root causes at crash, lots of fixed aircraft crash tests were conducted. Appropriate crash load factors were established with the comprehension of structural behavior based on dynamic analysis and investigation of human tolerance. Cargo restraint criteria were set up considering passengers safety and operational cost while analyzing past cargo aircraft accident data using a probabilistic approach. Reviewing results of past crash tests, current crash landing load factor was appreciated physically, medically, and economically.

• Structural Engineering and Mechanics
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• v.77 no.6
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• pp.705-720
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• 2021

Reinforced concrete (RC) columns are the primary type of vertical support used in building structures that sustain vertical loads. However, their strength may be insufficient due to fire, earthquake or volatile environments. The load demand may be increased due to new functional usages of the structure. The deformability of concrete columns can be greatly reduced under high axial load conditions. In response, a novel steel encasement that distinguishes from the traditional steel jacketing that is assembled by welding or bolt is developed. This novel strengthening method features easy installation and quick strengthening because direct fastening is used to connect the four steel plates surrounding the column. This new connection method is usually used to quickly and stably connect two steel components by driving high strength fastener into the steel components. The connections together with the steel plates behave like transverse reinforcement, which can provide passive confinement to the concrete. The confined column along with the steel plates resist the axial load. By this way, the axial load capacity and deformability of the column can be enhanced. Eight columns are tested to examine the reliability and effectiveness of the proposed method. The effects of the vertical spacing between adjacent connections, thickness of the steel plate and number of fasteners in each connection are studied to identify the critical parameters which affect the load bearing performance and deformation behavior. Lastly, a theoretical model is proposed for predicting the axial load capacity of the strengthened RC columns.

• Steel and Composite Structures
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• v.41 no.5
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• pp.731-746
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• 2021

The purpose of this paper is to investigate the axial bearing capacity and residual properties of steel reinforced recycled aggregate concrete (SRC) column after elevated temperature. A total of 48 SRC columns were designed for the static loading test after elevated temperature. The variables include replacement ratios, designed temperature, target duration, thicknesses of cover concrete, steel ratios and stirrup spacing. From this test, the mass loss ratio and stress load-deformation curve were obtained, and the influence of various parameters on residual bearing capacity were analyzed. ABAQUS was used to calculate the temperature field of specimens, and then got temperature damage distribution on the cross-section concrete. It was shown that increasing of the elevated temperatures leaded to the change of concrete color from smoky-gray to grayish brown and results in reducing the bearing capacity of SRC columns. The axial damage and mechanism of SRC columns were similar to those of reinforced natural aggregate concrete columns at the same temperatures. Finally, the calculation method of axial compressive residual bearing capacity of SRC columns recycled concrete columns after high temperature was reported based on the test results and finite element analysis.

• Journal of Korean Association for Spatial Structures
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• v.22 no.4
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• pp.89-98
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• 2022

The recent earthquake in Korea caused a lot of damage to reinforced concrete (RC) columns with non-seismic details. The nonlinear analysis enables predicting the hysteresis behavior of RC columns under earthquakes, but the analytical model used for the columns must be accurate and practical. This paper studied the nonlinear analysis models built into a commercial structural analysis program for the existing RC columns. The load-displacement relationships, maximum strength, initial stiffness, and energy dissipation predicted by the three analysis models were compared and analyzed. The results were similar to those tested in the order of the fiber, Pivot, and Takeda models, whereas the fiber model took the most time to build. For columns subjected to axial load, the Pivot model could predict the behavior at a similar level to that of the fiber model. Based on the above, it is expected that the Pivot model can be applied most practically for existing RC columns.

• Steel and Composite Structures
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• v.52 no.1
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• pp.57-76
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• 2024

The management of waste tire rubber has become a pressing environmental and health issue, requiring sustainable solutions to mitigate fire hazards and conserve natural resources. The performance of waste materials in structural components needs to be investigated to fabricate sustainable structures. This study aims to investigate the behavior of glass fiber reinforced polymer (GFRP) reinforced rubberized concrete (GRRC) compressive components under compressive loads. Nine GRRC circular compressive components, varying in longitudinal and transverse reinforcement ratios, were constructed. A 3D nonlinear finite element model (FEM) was proposed by means of the ABAQUS software to simulate the behavior of the GRRC compressive components. A comprehensive parametric analysis was conducted to assess the impact of different parameters on the performance of GRRC compressive components. The experimental findings demonstrated that reducing the spacing of GFRP stirrups enhanced the ductility of GRRC compressive components, while the addition of rubberized concrete further improved their ductility. Failure in GRRC compressive components occurred in a compressive columnar manner, characterized by vertical cracks and increased deformability. The finite element simulations closely matched the experimental results. The proposed empirical model, based on 600 test samples and considering the lateral confinement effect of FRP stirrups, demonstrated higher accuracy (R² = 0.835, MSE = 171.296, MAE = 203.549, RMSE = 195.438) than previous models.

• Steel and Composite Structures
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• v.52 no.3
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• pp.313-325
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• 2024

This work presents experimental and numerical investigations on the flexural performances of composite deep-deck plate slabs. Seven deep-deck plate slab specimens with topping concrete were fabricated; the height of the topping slab as well as presence and type of shear connector were set as the main variables to perform bending experiments. The flexural behaviors of the specimens and composite behaviors of the deck plate and concrete were analyzed in detail. The contributions of the deck plate to the flexural stiffness and strength of the slab were identified through finite element (FE) analysis. FE analysis was carried out using the validated FE model by considering the varying bond strengths of the deck plates and concrete, thickness of the deck plate, and types and spacings of the shear connectors. Based on the results, the degree of composite of the deep-deck plate was examined, and a flexural strength equation for the composite deck plate slabs was proposed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.6
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• pp.727-736
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• 2021

Road tunnel lengths are increasing. Some 1,300 tunnels with 1,102 km in length had been increased till 2019 from 2010. There are 64 tunnels over 3,000 m in length, with their total length adding up to 276.7 km. Safety facilities in the event of a tunnel fire are critical so as to prevent large-scale casualties. Standards for installing disaster prevention facilities are being proposed based on the guidelines of the Ministry of Land, Infrastructure and Transport, but they may be limited to deep underground tunnels. This study was undertaken to provide guidelines for the spacing of evacuation connection passages and the widths of evacuation connection doors. Evacuation with various spacing and widths was simulated in regards to evacuation time, which is the measure of safety, using the evacuation analysis simulation software EXODUS Ver.6.3 and the fire/smoke analysis software SMARTFIRE Ver.4.1. Evacuation connection gates with widths of 0.9 m and 1.2 m, and spacings of 150 m to 250 m, were set to every 20 m. In addition, longitudinal slopes of 6 % and 0 % were considered. It was determined to be safe when the evacuation completion time was shorter than the delay diffusion time. According to the simulation results, all occupants could complete evacuation before smoke spread regardless of the width of the evacuation connection door when the longitudinal slope was 6 % and the interval of evacuation connection passage was 150 m. When the evacuation connection passage spacing was 200 m and the evacuation connection gate width was 1.2 m, all occupants could evacuate when the longitudinal slope was 0 %. Due to difference in evacuation speed according to the longitudinal slope, the evacuation time with a 6 % slope was 114 seconds shorter (with the 190 m connection passage) than with a 0 % slope. A shorter spacing of evacuation connection passages may reduce the evacuation time, but this is difficult to implement in practice because of economic and structural limitations. If the width of the evacuation junction is 1.2 m, occupants could evacuate faster than with a 0.9 m width. When the width of a connection door is 1.2 m with appropriate connection passage spacing, it might provide a means to increase economic efficiency and resolve structural limitations while securing evacuation safety.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.2
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• pp.71-78
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• 2014

There is a big risk of bullet impact because military rotorcraft is run in the battle environment. Due to the bullet impact, the rapid increase of the internal pressure can cause the internal explosion or fire of fuel cell. It can be a deadly damage on the survivability of crews. Then, fuel cell of military rotorcraft should be designed taking into account the extreme situation. As the design factor of fuel cell, the internal fluid pressure, structural stress and bullet kinetic energy can be considered. The verification test by real object is the best way to obtain these design data. But, it is a big burden due to huge cost and long-term preparation efforts and the failure of verification test can result in serious delay of a entire development plan. Thus, at the early design stage, the various numerical simulations test is needed to reduce the risk of trial-and-error together with prediction of the design data. In the present study, the bullet impact numerical simulation based on SPH(smoothed particle hydrodynamic) is conducted with the commercial package, LS-DYNA. Then, the resulting equivalent stress, internal pressure and bullet's kinetic energy are evaluated in detail to examine the possibility to obtain the configuration design data of the fuel cell.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.76-83
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• 2021

This study examines the bending behavior of lap-spliced ultra-high-strength fiber-reinforced concrete members and evaluates the safety of the design codes for ultra-high-strength fiber-reinforced concrete structures. An experiment on a total of six beams was performed. The main variables were the fiber-inclusion and the lap-spliced length at the center of the beams. The steel fibers in a volume fraction of 2% were used, and the lap-splice lengths were determined to be 8db and 16db. As a result of the test, the specimens not reinforced with fiber lost abrupt load-bearing capacity at the lap region and did not experience yielding of the reinforcing bar. In the case of fiber-reinforced concrete, if a lap-splice length of 16db is secured, the yielding of the main reinforcing bar can be experienced, and appropriate flexural strength can be expressed. Based on the experimental results of this study, as a result of reviewing the lap-splice length calculation formulas of the current design standards and the ultra-high-strength concrete structural design recommendations, it was found that all of them were evaluated conservatively.