• Earthquakes and Structures
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• v.7 no.3
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• pp.317-331
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• 2014

An experimental study was performed to investigate the seismic performance of solid steel reinforced concrete (SRC) frames with special-shaped columns that are composed of SRC special-shaped columns and reinforced concrete beams. For this purpose, two models of two-bay and three-story frame, including an edge frame and a middle frame, were designed and tested. The failure process and patterns were observed. The mechanical behaviors such as load-displacement hysteretic loops and skeleton curves, load bearing capacity, drift ratio, ductility, energy dissipation and stiffness degradation of test specimens were analyzed. Test results show that the failure mechanism of solid SRC frame with special-shaped columns is the beam-hinged mechanism, satisfying the seismic design principle of "strong column and weak beam". The hysteretic loops are plump, the ductility is good and the capacity of energy dissipation is strong, indicating that the solid SRC frame with special-shaped columns has excellent seismic performance, which is better than that of the lattice SRC frame with special-shaped columns. The ultimate elastic-plastic drift ratio is larger than the limit value specified by seismic code, showing the high capacity of collapse resistance. Compared with the edge frame, the middle frame has higher carrying capacity and stronger energy dissipation, but the ductility and speed of stiffness degradation are similar. All these can be helpful to the designation of solid SRC frame with special-shaped columns.

• Journal of the Earthquake Engineering Society of Korea
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• v.25 no.5
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• pp.191-199
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• 2021

In seismic design, hollow section concrete columns offer advantages by reducing the weight and seismic mass compared to concrete section RC bridge columns. However, the flexure-shear behavior and spirals strain of hollow section concrete columns are not well-understood. Octagonal RC bridge columns of a small-scale model were tested under cyclic lateral load with constant axial load. The volumetric ratio of the transverse spiral hoop of all specimens is 0.00206. The test results showed that the structural performance of the hollow specimen, such as the initial crack pattern, initial stiffness, and diagonal crack pattern, was comparable to that of the solid specimen. However, the lateral strength and ultimate displacement of the hollow specimen noticeably decreased after the drift ratio of 3%. The columns showed flexure-shear failure at the final stage. Analytical and experimental investigations are presented in this study to understand a correlation confinement steel ratio with neutral axis and a correlation between the strain of spirals and the shear resistance capacity of steel in hollow and solid section concrete columns. Furthermore, shear strength components (V_c, V_s·, V_p) and concrete stress were investigated.

• Journal of the Earthquake Engineering Society of Korea
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• v.21 no.1
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• pp.11-20
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• 2017

This study investigates the seismic performance of solid reinforced concrete columns with triangular reinforcement details using nonlinear seismic analysis. The developed reinforcement details are economically feasible and rational, and facilitate shorter construction periods. By using a sophisticated nonlinear finite element analysis program, the accuracy and objectivity of the assessment process can be enhanced. Solution of the equations of motion is obtained by numerical integration using Hilber-Hughes-Taylor (HHT) algorithm. The proposed numerical method gives a realistic prediction of seismic performance throughout the input ground motions for several column specimens. As a result, developed triangular reinforcement details were designed to be superior to the existing reinforcement details in terms of required performance.

• FOCUS: LIFE SCIENCE
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• no.1
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• pp.4.1-4.15
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• 2024

The Avantor® ACE® UltraCore series encompasses High Performance Liquid Chromatography (HPLC) and Ultra High Performance Liquid Chromatography (UHPLC) columns designed to deliver high throughput and high-efficiency ultra-fast separations. Utilizing ultra-inert solid-core silica particles with monodisperse particle distribution, these columns combine the high efficiency of UHPLC with the operability of HPLC instrumentation, yielding lower backpressure and high-resolution separations suitable for a broad spectrum of analytes. The Avantor® ACE® UltraCore range includes three primary product types: • UltraCore BIO: Designed for large biomolecules (≥5 kDa), these columns offer exceptional performance in separating biologically derived compounds. • UltraCore: Ideal for standard small organic molecules, providing rapid separations for both synthetic and natural mixtures. • UltraCore Super: Equipped with encapsulated bonding technology for small organic molecules in extreme pH conditions, optimal for high pH buffer requirements. The Avantor® ACE® UltraCore columns present a versatile and high-efficiency solution for chromatographic separation needs, accommodating a wide range of molecular sizes and providing enhanced resolution and reduced analysis time. Their adaptability to both HPLC and UHPLC systems, combined with the advantages of solid-core technology, makes them an invaluable tool in analytical and preparative chromatography.

• Computers and Concrete
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• v.17 no.3
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• pp.387-406
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• 2016

Confined transverse reinforcement was arranged in a plastic hinge region to resist the lateral load that increased the lateral confinement effect in the bridge substructure. Columns increased the seismic performance through securing stiffness and ductility. The calculation method of transverse reinforcements at plastic hinges is reported in the AASHTO-LRFD specification. This specification was only proposed for solid reinforced concrete (RC) columns. Therefore, if this specification is applied for another column as composite column besides the solid RC column, the column cannot be properly evaluated. The application of this specification is particularly limited for composite hollow RC columns. The composite hollow RC column consists of transverse, longitudinal reinforcements, cover concrete, core concrete, and an inner tube inserted in the hollow face. It increases the ductility, strength, and stiffness in composite hollow RC columns. This paper proposes a modified equation for economics and rational design through investigation of displacement ductility when applying the existing specifications at the composite hollow RC column. Moreover, a parametric study was performed to evaluate the detailed behavior. Using these results, a calculation method of economic transverse reinforcements is proposed.

• Journal of the Korea Concrete Institute
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• v.28 no.1
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• pp.75-84
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• 2016

The purpose of this study was to investigate the performance of solid reinforced concrete columns with triangular reinforcement details. The proposed reinforcement details has economic feasibility and rationality and makes construction periods shorter. A model of solid reinforced concrete columns with triangular reinforcement details was tested under a constant axial load and a quasi-static, cyclically reversed horizontal load. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. The used numerical method gives a realistic prediction of performance throughout the loading cycles for several test specimens investigated. As a result, proposed triangular reinforcement details for material quantity reduction was superior to existing reinforcement details in terms of required performance.

• FOCUS: LIFE SCIENCE
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• no.1
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• pp.3.1-3.7
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• 2024

The article discusses the critical role of chromatography in the analysis and purification of proteins in biopharmaceuticals, emphasizing the importance of comprehensive characterization for ensuring their safety and efficacy. It highlights the use of Avantor® ACE® HPLC columns for the separation and purification of proteins, focusing on the analysis of intact proteins using reversed-phase liquid chromatography (RPLC) with fully porous particles. This article also details the application of different mobile phase additives, such as TFA and formic acid, and emphasizes the advantages of using type B ultra-pure silica-based columns for efficiency and peak shape in biomolecule analysis. Additionally, it addresses the challenges of analyzing intact proteins due to slow molecular diffusion and introduces the concept of solid-core (or superficially porous) particles, emphasizing their benefits over traditional porous particles for the analysis of therapeutic proteins. Furthermore, it discusses the development of Avantor® ACE® UltraCore BIO columns, specifically designed for the high-efficiency separation of large biomolecules, such as proteins, and demonstrates their effectiveness in achieving high-resolution separations, even for higher molecular weight proteins like monoclonal antibodies (mAbs). In addition, it underscores the complexity of analyzing and characterizing intact protein biopharmaceuticals, requiring a range of analytical techniques and the use of wide-pore stationary phases, operated at elevated temperatures and with relatively shallow gradients. It highlights the comprehensive range of options offered by Avantor® ACE® wide pore columns, including both fully porous and solid-core particles, bonded with a variety of complementary stationary phase chemistries to optimize selectivity during method development. The use of ultrapure and highly inert base silica is emphasized for enabling the use of lower concentrations of mobile phase modifiers without compromising analyte peak shape, particularly beneficial for LC-MS applications. Then the article concludes by emphasizing the significance of reversed-phase liquid chromatography and its compatibility with mass spectrometry as a valuable tool for the separation and analysis of intact proteins and their closely related variants in biopharmaceuticals.

• Steel and Composite Structures
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• v.46 no.6
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• pp.793-804
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• 2023

In this study, cyclic loading tests were conducted to assess the seismic performance of cast-in-place (CIP) concrete-filled hollow core precast concrete columns (HPCC) constructed using steel ducts and rubber tubes. The outer shells of HPCC, with a hollow ratio of 47%, were fabricated using steel ducts and rubber tubes, respectively. Two combinations of shear studs & long threaded bars or cross-deformed bars & V-ties were employed to ensure the structural integrity of the old concrete (outer shell) and new CIP concrete. Up to a drift ratio of 3.8%, the hysteresis loop, yielding stiffness, dissipated energy, and equivalent damping ratio of the HPCC specimens were largely comparable to those of the solid columns. Besides the similarities in cyclic load-displacement responses, the strain history of the longitudinal bars and the transverse confinement of the three specimens also exhibited similar patterns. The measured maximum moment exceeded the predicted moment according to ACI 318 by more than 1.03 times. However, the load reduction of the HPCC specimen after reaching peak strength was marginally greater than that of the solid specimen. The energy dissipation and equivalent damping ratios of the HPCC specimens were 20% and 25% lower than those of the solid specimen, respectively. Taking into account the overall results, the structural behavior of HPCC specimens fabricated using steel ducts and rubber tubes is deemed comparable to that of solid columns. Furthermore, it was confirmed that the two combinations for securing structural integrity functioned as expected, and that rubber air-tubes can be effectively used to create well-shaped hollow sections.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.949-954
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• 2006

The purpose of this paper is to investigate the stability of tapered columns with clamped one end and carrying a tip mass of rotatory inertia with translational elastic support at the other end. The linearly tapered columns with the solid rectangular cross-section is adopted as the column taper. The differential equation governing free vibrations of such Beck columns is derived using the Bernoulli-Euler beam theory. Both the divergence and flutter critical loads are calculated from the load-frequency curves which are obtained by solving the differential equation. The critical loads are presented as functions of various non-dimensional system parameters: the taper type, the subtangential parameter, mass ratio and spring stiffness.

• Steel and Composite Structures
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• v.24 no.4
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• pp.409-423
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• 2017

This paper presents an experimental study on damage evolution laws of solid-web steel reinforced concrete (SRC) T-shaped columns along the direction of the web under various loadings. Ten specimens with a scale ratio of 1/2 and a shear span ratio of 2.5 were designed and fabricated. The influences of various parameters, including the axial compression ratio, steel ratio, and loading mode, were examined. The mechanical performances including load-displacement curve and energy dissipation capacity under the monotonic and low cyclic loadings were analyzed. Compared with the monotonic loading, bearing capacity, ultimate deformation capacity, and energy dissipation capacity of the specimens decrease to some extent with the increase of the displacement amplitude and the number of loading cycle. The results show that the damage process of the SRC T-shaped column can be divided into five stages, namely non-damage, slight-damage, steadily-developing-damage, severe-damage and complete-damage. Finally, based on the Park-Ang model, a modified nonlinear damage model which combines the maximum deformation with hysteretic energy dissipation is proposed by taking into account the dynamic influence of the aforementioned parameters. The results show that the modified model in this paper is more accurate than Park-Ang model and can better describe the damage evolution of SRC T-shaped columns.