• Structural Engineering and Mechanics
• /
• v.22 no.5
• /
• pp.541-562
• /
• 2006

This paper compares the performance of axially loaded concrete filled steel tube (CFST) columns cast using a conventionally vibrated normal concrete (NC) and a novel self-consolidating concrete (SCC) made with a new viscosity modifying admixture (VMA). A total of sixteen columns with a standard compressive strength of about 50 MPa for both SCC and NC were tested by applying concentric axial load through the concrete core. Columns were fabricated without and with longitudinal and hoop reinforcement (Series I and Series II, respectively) in addition to the tube confinement. The slenderness of the columns expressed as height to diameter ratio (H/D) ranged between 4.8 and 9.5 for Series CI and between 3.1 and 6.5 for Series CII. The strength and ductility of SCC columns were found comparable to those of their NC counterparts as the maximum strength enhancement in NC columns ranged between 1.1% and 7.5% only. No significant difference in strain development was found due to the presence of SCC or NC or due to the presence of longitudinal and hoop reinforcement. Biaxial stress development in the steel tube as per von Mises yield criterion showed similar characteristics for both SCC and NC columns. The confined strength ($f^{\prime}_{cc}$) of SCC was found to be lower than that of NC and $f^{\prime}_{cc}$ also decreased with the increase of slenderness of the columns. Analytical models for the prediction of confined concrete strength and axial strength of CFST columns were developed and their performance was validated through test results. The proposed models were found to predict the axial strength of CFST columns better than existing models and Code based design procedures.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.9 no.4
• /
• pp.217-226
• /
• 2005

This study made member specimen for taking specimen, core with the concrete mixing normal concrete, admixture and conducted the same air curing as field conditions. After performing destructive and nondestructive test by age, estimate expression was suggested by analyzing correlations between compressive strength, rebound number and ultrasonic pulse velocity and the results are as follows. As a result of comparing error rate of existing expressions and this estimation expression, error rate of this estimation is reduced compared to existing expressions and has higher reliability. When conventional concrete expression is applied to admixture concrete, error rate occurs and then this study suggests the estimation expressions depending on types of admixture concrete.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2015.05a
• /
• pp.164-165
• /
• 2015

Recently, the reason of using foamed concrete is for core of panel, filler of construction material to give lightness. However, cement causes environmental problem. The cement generates CO₂ but we normally use cement during manufacturing foamed concrete. Accordingly, this study focuses on dynamic properties of matrix according to the addition ratio of paper ash to make lightweight matrix with blast furnace slag and paper ash which are industrial by-product. The experiment progessed in order to select th optimum mixing ratio of the blast furnace slag and paper ash. There are totally 7 levels such as B100:P0, B95:P5, B90:P10, B85:P15, B80:P20, B75:P25, B70:P30 in this study. As a result of the test, B95:P5 matrix has the best density and compressive strength.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.05a
• /
• pp.475-480
• /
• 2002

Tension tests of six half-thickness concrete containment wall elements were conducted as part of a Korea Atomic Energy Research Institute (KARRI) program. The aim of the KAERI test program is providing a test-verified analytical method for estimating capacities of concrete reactor containment buildings under internal overpressurization from postulated degraded core accidents. The data from the tests reported herein should be useful for benchmarking method that requires modeling of material behavior including concrete cracking and reinforcement/concrete interaction exhibited by the test. Major test variable is the compressive strength of concrete and its effect on the behavior of prestressed concrete panel subjected to biaxial tension.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2009.05a
• /
• pp.223-224
• /
• 2009

This study was performed to development 80MPa high strength concrete using local raw material of Busan and to estimate field application ability. As the result of three types of mixture, fresh and hardened properties were satisfied with target requirement properties. Hydration temperature was revealed mean 75$\sim$85$\circ$C. Additionally, in case of compressive strength, core specimen's strength is six times higher than field curing specimen by very high hydration heat.

• Advances in concrete construction
• /
• v.10 no.1
• /
• pp.13-20
• /
• 2020

Steel corrosion in embedded steel causes a significant durability problems and this usually propagates to structural degradation. Large-scaled concrete structures, PSC (Pre-stressed Concrete) or RC (Reinforced Concrete) structures, are usually constructed with mass concrete and require quite a long construction period. When they are located near to sea shore, chloride ion penetrates into concrete through direct or indirect exposure to marine environment, and this leads durability problems. Even if the structures are sheltered from chloride ingress outside after construction, the chloride contents which have been penetrated into concrete during the long construction period are differently evaluated from the initially mixed chloride content. In the study, chloride profiles in cores extracted from anchorage concrete block in two large-scaled suspension bridge (K and P structure) are evaluated considering the exposure periods and conditions. Total 21 cores in tendon room and chamber room were obtained, and the acid-soluble chlorides and compressive strength were evaluated for the structures containing construction period around 3 years. The test results like diffusion coefficient and surface chloride content from the construction joint and cracked area were also discussed with the considerations for maintenance.

• Steel and Composite Structures
• /
• v.11 no.6
• /
• pp.469-488
• /
• 2011

This paper consists of two parts; the first part describes the laboratory work concerning the behavior of lightweight aggregate concrete filled steel tubes (LACFT). Based on eccentricity tests, fifty-four specimens with different slenderness ratios (L/D= 3, 7, and 14) were tested. The main parameters varied in the test are: load eccentricity; steel ratio; and slenderness ratio. The standard load-strain curves of LACFT columns under eccentric loading were summarized and significant parameters affecting LACFT column's bearing capacity, failure mechanism and failure mode such as confinement effect and bond strength were all studied and analyzed through the comparison with predicted strength of concrete filled steel tube columns (CFT) using the existing codes such as AISC-LRFD (1999), CHN DBJ 13-51-2003 (2003) and CHN CECS 28:90 (1990). The second part of this paper presents the results of parametric study and introduces a practical and accurate method for determination of the maximum compressive strength of confined concrete core ($f_{max}$), In addition to, the study of the effect of aspect-ratio and length-width ratio on the yield stress of steel tubes ( $f_{sy}$) under biaxial state of stress in CFT columns and the effect of these two factors on the ultimate load carrying capacity of axially loaded CFT/LACFT columns.

• Journal of the Korea Concrete Institute
• /
• v.15 no.1
• /
• pp.60-68
• /
• 2003

Tension tests of six half-thickness concrete containment wall elements were conducted as a part of Korea Atomic Energy Research Institute (KAERI) program. The aim of the KAERI test program is to provide a test-verified analytical method for estimating capacities of concrete reactor containment buildings under internal overpressurization from postulated degraded core accidents. The data from the tests reported herein should be useful for benchmarking analytical method that require modeling of material behavior including concrete cracking behavior and reinforcement/concrete interaction exhibited by the test. Major test variable is compressive strength of concrete, and its effect on the behavior of prestressed concrete panel subjected to biaxial tension is investigated.

• Steel and Composite Structures
• /
• v.28 no.5
• /
• pp.573-588
• /
• 2018

The objective of this paper is to investigate the mechanical performances of polygonal concrete-filled circular steel tubular (CFT) stub columns under axial loading through combined experimental and numerical study. A total of 32 specimens were designed to investigate the effect of the concrete strength and steel ratio on the compressive behavior of polygonal CFT stub columns. The ultimate bearing capacity, ductility and confinement effect were analyzed based on the experimental results and the failure modes were discussed in detail. Besides, ABAQUS was adopted to establish the three dimensional FE model. The composite action between the core concrete and steel tube was further discussed and clarified. It was found that the behavior of CFT stub column changes with the change of the cross-section, and the change is continuous. Finally, based on both experimental and numerical results, a unified formula was developed to estimate the ultimate bearing capacity of polygonal CFT stub columns according to the superposition principle with rational simplification. The predicted results showed satisfactory agreement with both experimental and FE results.

• Steel and Composite Structures
• /
• v.35 no.2
• /
• pp.159-169
• /
• 2020

Sandwich composite wall consists of concrete core attached by two external steel faceplates. It combines the advantage of steel and concrete. The appropriate composite action between steel faceplate and concrete core is achieved by using adequate mechanical connectors. This research studied the compressive behavior of the sandwich composite walls using steel trusses to bond the steel faceplates to concrete infill. Four short specimens with different wall width and thickness of steel faceplate were designed and tested under axial compression. The test results were comprehensively evaluated in terms of failure modes, load versus axial and lateral deformation responses, resistance, stiffness, ductility, strength index, and strain distribution. The test results showed that all specimens exhibited high resistance and good ductility. Truss connectors offer better restraint to walls with thinner faceplates and smaller wall width. In addition, increasing faceplate thickness is more effective in improving the ultimate resistance and axial stiffness of the wall.