• Steel and Composite Structures
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• v.16 no.3
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• pp.253-267
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• 2014

Based on the test on a 1/2.5-scaled model of a two-bay and three-story inner frame composed of reinforced concrete beams and lattice steel reinforced concrete (SRC) irregular section columns under low cyclic reversed loading, the failure process and the features of the frame were observed. The subsequence of plastic hinges of the structure, the load-displacement hysteresis loops and the skeleton curve, load bearing capacity, inter-story drift ratio, ductility, energy dissipation and stiffness degradation were analyzed. The results show that the lattice SRC inner frame is a typical strong column-weak beam structure. The hysteresis loops are spindle-shaped, and the stiffness degradation is insignificant. The elastic-plastic inter-story deformation capacity is high. Compared with the reinforced concrete frame with irregular section columns, the ductility and energy dissipation of the structure are better. The conclusions can be referred to for seismic design of this new kind of structure.

• Computers and Concrete
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• v.16 no.5
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• pp.703-722
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• 2015

This study investigates the performance of advanced hollow reinforced concrete (RC) bridge column sections with triangular reinforcement details. Hollow column sections are based on economic considerations of cost savings associated with reduced material and design moments, as against increased construction complexity, and hence increased labor costs. The proposed innovative reinforcement details are economically feasible and rational, and facilitate shorter construction periods. We tested a model of advanced hollow column sections under quasi-static monotonic loading. The results showed that the proposed triangular reinforcement details were equal to the existing reinforcement details, in terms of the required performance. We used a computer program, Reinforced Concrete Analysis in Higher Evaluation System Technology (RCAHEST), for analysis of the RC structures; and adopted a modified lateral confining effect model for the advanced hollow bridge column sections. Our study documents the testing of hollow RC bridge column sections with innovative reinforcement details, and presents conclusions based on the experimental and analytical findings. Additional full-scale experimental research is needed to refine and confirm the design details, especially for the actual detailing employed in the field.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.1
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• pp.33-43
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• 2016

This study investigates the performance of hollow precast segmental bridge columns with reinforcement details for material quantity reduction. The proposed triangular reinforcement details are economically feasible and rational, and facilitate shorter construction periods. The precast segmental bridge columns provides an alternative to current cast-in-place systems. We tested a model of hollow precast segmental bridge columns under a constant axial load and a quasi-static, cyclically reversed horizontal load. We used a computer program, Reinforced Concrete Analysis in Higher Evaluation System Technology (RCAHEST), for analysis of reinforced concrete structures. The used numerical method gives a realistic prediction of performance throughout the loading cycles for hollow precast segmental bridge column specimens investigated. As a result, proposed reinforcement details for material quantity reduction was equal to existing reinforcement details in terms of required performance.

• Steel and Composite Structures
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• v.20 no.3
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• pp.501-512
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• 2016

High-strength structural bolts have been utilized for beam-to-column connections in steel-framed structural buildings. Failure of these components may be caused by the bolt shank fracture or threads stripping-off, documented in the literature. Furthermore, these structural bolts are galvanized for corrosion resistance or quenched-and-tempered in the manufacturing process. This paper adopted the finite element simulation to demonstrate discrete mechanical performance for these bolts under tensile loading conditions, the coated and uncoated numerical model has been built up for two numerical integration methods: explicit and implicit. Experimental testing and numerical methods can fully approach the failure mechanism of these bolts and their ultimate load capacities. Comparison has also been conducted for two numerical integration methods, demonstrating that the explicit integration procedure is also suitable for solving quasi-static problems. Furthermore, by using precise bolt models in T-Stub, more accurately simulate the mechanical behavior of T-Stub, which will lay the foundation of the mechanical properties of steel bolted joints.

• Journal of Biosystems Engineering
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• v.30 no.5 s.112
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• pp.280-284
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• 2005

Front the production on the farm to the consumer, agricultural products are subject to various physical treatments involving mechanical techniques and devices. It is essential to understand the physical laws governing the response of these biological materials so that the machines, processes, and handling operations can be designed fur maximum efficiency and the highest quality of the end products. A compression test system was developed to test the physical properties of fruits including apple, pear, and peach which may lead to a better understanding of the physical laws. The test system consisted of a digital storage oscilloscope and simple mechanism which can apply quasi-static compression to fresh fruits. Rupture force, energy, and deformation were measured at the five levels of compression speed from 1.25 to 62.5 mm/min for each internal and external tissues. Rupture forces for apple and pear were in the range of 42.2 to 46.2 N and 38.8 to 41.2 N for external and infernal tissues, respectively. Rupture forces fir peach external tissues were in the range of 48.2 to 54.0 N.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.275-278
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• 2005

INCONEL 718, nickel based superalloy, has good formability, high strength, excellent corrosion resistance and mechanical properties at high temperature. Owing to theses attractive properties, it finds use in applications such as combustion system, turbine engines and nuclear reactors. In such applications, components are typically required to be tolerant of high stress impact loading. This may cause material degradation and lead to catastrophic failure during service operation. In order to design optimal structural parts made of INCONEL 718, accurate understanding of material's mechanical properties, dynamic behavior and fracture characteristic as a function of strain rates are required. This paper concerned with the dynamic material properties of the INCONEL 718 for the various strain rates. The dynamic response of the INCONEL 718 at intermediate strain rate is obtained from the high speed tensile test machine test and at the high strain rate is from the split Hopkinson pressure bar test. Based on the experimental results, the effects of strain rate on dynamic flow stress, work hardening characteristics, strain rate sensitivity and elongation to the failure are evaluated. Experimental results from both quasi-static and high strain rate up to the 5000/sec are interpolated in order to construct the Johnson-Cook model as the constitutive relation that should be applied to simulate and design the structural parts made of INCONEL 718.

• Transactions of Materials Processing
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• v.14 no.6 s.78
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• pp.559-564
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• 2005

INCONEL 718, nickel based superalloy, has good formability, high strength, excellent corrosion resistance and mechanical properties at high temperature. Owing to theses attractive properties, it is utilized in applications such as combustion system, turbine engines and nuclear reactors. In such applications, components are typically required to be tolerant of high stress impact loading. This may cause material degradation and lead to catastrophic failure during service operation. Accurate understanding of material's mechanical properties with various strain rates is required in order to guarantee the reliability of structural parts made of INCONEL 718. This paper is concerned with the dynamic material properties of the INCONEL 718 at various strain rates. The dynamic response of the INCONEL 718 at the intermediate strain rate is obtained from the high speed tensile test and at the high strain rate is from the split Hopkinson pressure bar test. The effect of the strain rate on dynamic flow stress, work hardening characteristics, strain rate sensitivity and elongation to the failure is evaluated with the experimental results. Experimental results from both the quasi-static and the high strain rate up to 5000/sec are interpolated in order to construct the Johnson-Cook model as the constitutive relation that should be applied to simulate and design the structural parts made of rNCONEL 718.

• Smart Structures and Systems
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• v.24 no.6
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• pp.783-791
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• 2019

Prefabricated reinforced-concrete shear walls are used extensively in building structures because they are convenient to construct and environmentally sustainable. To make large walls easier to transport, they are divided into smaller segments and then assembled at the construction site using a variety of connection methods. The present paper proposes a precast shear wall assembled using steel shear keys, wherein the shear keys are fixed on the embedded steel plates of adjacent wall segments by combined plug and fillet welding. The anchoring strength of shear keys is known to affect the mechanical properties of the wall segments. Loading tests were therefore performed to observe the behavior of precast shear wall specimens with different anchoring components for shear keys. The specimen with insufficient strength of anchoring components was found to have reduced stiffness and lateral resistance. Conversely, an extremely high anchoring strength led to a short-column effect at the base of the wall segments and low deformation ability. Finally, for practical engineering purposes, a design approach involving the safety coefficient of anchoring components for steel shear keys is suggested.

• Steel and Composite Structures
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• v.11 no.3
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• pp.251-271
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• 2011

To make direct comparisons regarding the cyclic behavior of thin steel plate shear walls (TSPSWs) with different infill-to-boundary frame connections, two TSPSWs were tested under quasi-static conditions, one having the infill plate attached to the boundary frame members on all edges and the other having the infill plate connected only to the beams. Also, the bare frame that was used in the TSPSW specimens was tested to provide data for the calibration of numerical models. The connection of infill plates to surrounding frames was achieved through the use of self-drilling screws to fish plates that were welded to the frame members. The behavior of TSPSW specimens are compared and discussed with emphasis on the characteristics important in seismic response, including the initial stiffness, ultimate strength and deformation modes observed during the tests. It is shown that TSPSW specimens achieve significant ductility and energy dissipation while the ultimate failure mode resulted from infill plate fracture at the net section of the infill plate-to-boundary frame connection after substantial infill plate yielding. Experimental results are compared to monotonic pushover predictions from computer analysis using strip models and the models are found to be capable of approximating the monotonic behavior of the TSPSW specimens.

• Coupled systems mechanics
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• v.8 no.3
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• pp.273-287
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• 2019

Elastoplastic analysis of an annular disc, being fully constrained on its outer rim and interacting with a purely elastic inclusion perfectly bonded with its inner rim, is conducted to study its plastic deformation and residual stress under thermal cycles. The system is termed the composite disc. Quasi-static plane-strain deformation is assumed, and the von Mises yield criterion with or without the Ludwik hardening rule is adopted in our finite element calculations. Effects of multiple material properties simultaneously being temperature dependent on the plastic behavior of the composite disc are considered. Residual stress is analyzed from a complete loading and unloading cycle. Results are discussed for various inclusion radii. It is found that when temperature dependent material properties are considered, the maximum residual stress may be greater than the maximum stress inside the disc at the temperature-loaded state due to lower temperature having larger yield stress. Temperature independent material properties overestimate stresses inside materials, as well as the elastic irreversible temperature and plastic collapse temperature.