• Journal of Korean Society of Steel Construction
• /
• v.26 no.5
• /
• pp.431-439
• /
• 2014

Concrete filled tubular columns are widely used because the mutual reaction between the concrete and the tube improves strength and ductility of the columns. In an attempt to secure efficient use of members, built-up square columns featuring large width-thickness ratio and the use of thin steel plates are suggested in this study. In order to evaluate the structural characteristics and seismic performance of the column-to-beam connections of the new shape columns, cyclic load test of T-shaped column-to-beam connections was conducted with variables of diaphragms and concrete-filling. Moment-rotational angle relationship, dissipated energy and failure behavior were compared to evaluate stress transfer mechanism of the new shape built-up square column-to-beam connections associated with the variables.

• Journal of Korean Society of Steel Construction
• /
• v.14 no.1
• /
• pp.121-130
• /
• 2002

This paper presents the tensile behavior of a Concrete-Filled Square Steel Tubular (CFT) column to H-beam welded connections. These connections were externally reinforced with T-shaped stiffeners at the junction of CFT column and beam. The tensile loading tests of eighteen tee-joint connections and finite element analysis using ANSYS were carried out. The main parameters of tests are as follows: 1) the thickness of Square Steel Tubular Column : 6 mm, 9 mm, 2) the strength ratios of tensile strength of horizontal stiffeners to tensile strength of beam flange : 70 %, 100 %, 150 %, 3) the strength ratios of shear strength of vertical stiffeners to tensile strength of beam flange : 80 %, 115 %, 160 %. The results of the tests demonstrate that overall behavior and failure modes of all the specimens are governed mainly by the horizontal stiffeners rather than the vertical stiffeners, and the vertical stiffener played only a role in transferring load introduced from beam to column.

• Steel and Composite Structures
• /
• v.5 no.6
• /
• pp.459-484
• /
• 2005

In recent years, the use of steel tube confined concrete (STCC) columns has been the interests of many structural engineers. The present study is an attempt to study the monotonic and cyclic behaviours of STCC columns. For the monotonic behaviours, a series of tests on STCC stub columns (twenty one), and beam-columns (twenty) were carried out. The main parameters varied in the tests are: (1) column section types, circular and square; (2) tube diameter (or width) to thickness ratio, from 40 to 162, and (3) load eccentricity ratio (e/r), from 0 to 0.5. For the cyclic behaviours, the test parameters included the sectional types and the axial load level (n). Twelve STCC column specimens, including 6 specimens with circular sections and 6 specimens with square sections were tested under constant axial load and cyclically increasing flexural loading. Comparisons are made with predicted column strengths and flexural stiffness using the existing codes. It was found that STCC columns exhibit very high levels of energy dissipation and ductility, particularly when subjected to high axial loads. Generally, the energy dissipation ability of the columns with circular sections was much higher than those of the specimens with square sections. Comparisons are made with predicted column strengths and flexural stiffness using the existing codes such as AIJ-1997, AISCLRFD- 1994, BS5400-1979 and EC4-1994.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.11a
• /
• pp.13-16
• /
• 2006

This article summarizes tests conducted on two full-scale interior slab-column connections with and without partially debonded reinforcement subjected to cyclic loading. Each test specimen consisted of a 4.2m square slab with a 355mm square column protruding 1.5m above and below the slab. The slab thickness was 152mm. The specimen with partially debonded reinforcement exhibited more lateral drift capacity than did the specimen with fully bonded reinforcement. With partial debonding of the flexural reinforcement, cyclic load appeared to produce less damage to the connection in the vicinity of the slab-column joint region.

• Earthquakes and Structures
• /
• v.16 no.3
• /
• pp.253-263
• /
• 2019

The efficacy of a galvanized steel wire mesh (GSWM) as an alternative material for the rehabilitation of RC beam-column connections damaged due to reversed cyclic loading was investigated. The repair mainly uses epoxy resin infused under pressure into the damaged zone and then confined using three types of locally available GSWM mesh. The mesh types used herein are (a) Weave type square mesh with 2mm grid opening (GWSM-1) (b) Twisted wire mesh with hexagonal opening of 15 mm (GSWM-2) and (c) welded wire mesh with square opening of 25 mm (GSWM-3). A reduced scale RC beam-column connection detailed as per ductile detailing codes of Indian Standard was considered for the experimental investigation. The rehabilitated specimens were also subjected to similar cyclic displacement. Important parameters related to seismic capacity such as strength, stiffness degradation, energy dissipation, and ductility were evaluated. The rehabilitated connections exhibited equal or better performance and hence the adopted rehabilitation strategies could be considered as satisfactory. Confinement of damaged region using GSWM-1 significantly enhanced the seismic capacity of the connections.

• Bulletin of the Korean Mathematical Society
• /
• v.59 no.3
• /
• pp.617-642
• /
• 2022

For positive integers n and d with d < n, an n × n array A based on 𝒳 = {0, 1, …, nd} is called a sparse anti-magic square of order n with density d, denoted by SAMS(n, d), if each non-zero element of X occurs exactly once in A, and its row-sums, column-sums and two main diagonal-sums constitute a set of 2n + 2 consecutive integers. An SAMS(n, d) is called regular if there are exactly d non-zero elements in each row, each column and each main diagonal. In this paper, we investigate the existence of regular sparse anti-magic squares of order n ≡ 1, 5 (mod 6), and prove that there exists a regular SAMS(n, d) for any n ≥ 5, n ≡ 1, 5 (mod 6) and d with 2 ≤ d ≤ n - 1.

• Steel and Composite Structures
• /
• v.32 no.3
• /
• pp.411-422
• /
• 2019

Six shear-critical square tubed steel reinforced concrete (TSRC) columns using the high-strength concrete ($f_{cu,150}=86.6MPa$) were tested under constant axial and lateral cyclic loads. The height-to-depth ratio of the short column specimens was specified as 2.6, and the axial load ratio and the number of shear studs on the steel shape were considered as two main parameters. The shear failure mode of short square TSRC columns was observed from the test. The steel tube with diagonal stiffener plates provided effective confinement to the concrete core, while welding shear studs on the steel section appeared not significantly enhancing the seismic behavior of short square TRSC columns. Specimens with higher axial load ratio showed higher lateral stiffness and shear strength but worse ductility. A modified ACI design method is proposed to calculate the nominal shear strength, which agrees well with the test database containing ten short square TSRC columns with shear failure mode from this study and other related literature.

• Steel and Composite Structures
• /
• v.22 no.1
• /
• pp.63-77
• /
• 2016

Top-down construction is a construction technique in which pit excavation and structure construction are conducted simultaneously. Reducing construction time and minimizing noise and vibration which affect neighboring structures, the technique is widely employed in constructing downtown structures. While H-steel columns have been commonly used as core columns, concrete filled steel tube (CFT) columns are at the center of attention because the latter have less axial directionality and greater cross-sectional efficiency than the former. When compared with circular CFT columns, square CFT columns are more easily connected to the floor structure and the area of percussion rotary drilling (PRD) is smaller. For this reason, square CFT columns are used as core columns of concrete encased and filled square (CET) columns in underground floors. However, studies on the structural behavior and concrete stress transfer of CET columns have not been conducted. Since concrete is cast according to construction sequence, checking the stress of concrete inside the core columns and the stress of covering concrete is essential. This paper presents the results of structural tests and analyses conducted to evaluate the usability and safety of CET columns in top-down construction where CFT columns are used as core columns. Parameters in the tests are loading condition, concrete strength and covering depth. The compressive load capacity and failure behavior of specimens are evaluated. In addition, 2 cases of field application of CET columns in underground floors are analyzed.

• Structural Monitoring and Maintenance
• /
• v.7 no.3
• /
• pp.215-231
• /
• 2020

In a reinforced concrete building different shapes of column are adopted depending on the structural orientation and the architectural aspect. When there is an increase in loading due to changes in usage or revision in the design codes these columns need to be strengthened for enhanced performance during their service life. Strengthening materials such as carbon fiber and glass fiber polymer has been successfully used however, due to high cost application other alternative materials need to be explore. Galvanized steel wire mesh (GSWM) is one of the suitable materials locally available. High tensile strength, low weight, corrosion resistance, easy installation, minimum change in dimensions of the sections and cost effectives are the advantages of GSWM. Therefore, in this paper, four different shapes of column such as circular, square, rectangular and L were wrapped with different layers GSWM and jacketed with mortar. All the specimens were tested under axial compression. The objective of the study is to investigate the effectiveness of GSWM as a confining material for strengthening of column having varying shape. Test results shows that the axial strength enhanced with wrapping of GSWM jacket and a circular column presented the highest load carrying capacity and ductility as compared to the others. From the study of 22 column specimens, it is found that axial load is increased upto 20% and 19% when circular and square column are strengthened with one wrap of GSWM respectively, while a rectangular and L column required a wraps of two and three layers respectively in order to achieved the same load capacity as that of a circular column. Based on the present study, it is concluded that GSWM can be effectively used for strengthening of different shapes of concrete columns economically.

• Journal of Korean Society of Steel Construction
• /
• v.14 no.6
• /
• pp.823-834
• /
• 2002

Maximum-strength concrete-filled steel square tubular columns were tested under concentric and biaxial eccentric load. Buckling length-section depth ratio $L_k/D$, magnitude of eccentricity e, and angle of eccentric load ${\theta}$ were selected as experimental parameters. Strength and behavior were also examined. Test results showed that the maximum strength of columns under biaxial eccentric load could be predicted using the previously proposed strength formula of columns undr uniaxia eccentric load. Likewise, the behavior and maximum strength of columns could be predicted using the analysis.