• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.321-330
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• 2002

This paper presents the experimental results of composite basement wall in which H-pile and reinforced concrete wall are combined using shear connector Twelve specimens are tested to evaluate the shear capacity of the wall. Main variables in the test are composite ratio, distribution of shear connector, thickness of wall, shear-span ratio, and shear reinforcement. Test results indicate that the shear capacity of test specimens varies with the foregoing variables except the composite ratio. The results are compared with strengths predicted using the equations of ACI 318-99, Zsutty, and Bazant. Based on this investigation, a method for predicting the shear strength of composite basement walls is proposed.

• Journal of the Korea Concrete Institute
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• v.29 no.1
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• pp.93-100
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• 2017

This study examined the one-way shear in concrete beam region and shear friction in joint region of a hybrid H-steel-reinforced concrete (HSRC) beam system with a simple ductile connection. One-way shear tests were conducted under overhanging beam system with a shear span-to-depth ratio of 1.6. Simple beams for shear friction were tested under two-point symmetrical top loads producing a clear shear span-to-depth ratio of 0.1. Test results showed that the dowel bars arranged in joint region insignificantly influence the propagation of shear cracks but enhances the shear strength of the HSRC beams by approximately 25%. The one-way shear strength and shear friction strength of HSRC beams can be conservatively evaluated using the design equations specified in ACI 318-14 and EC2 shear provisions.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.133-140
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• 2010

Five strengthened columns and an unstrengthened column were tested under constant axial load and cyclic lateral loads to examine the seismic performance of the unbounded strengthening procedure using wire ropes and T-plates. Main variables considered were the presence of mortar cover for strengthening steel element and anchorage method of T-plate. Test results clearly showed that T-plates having a proper anchorage contribute to transfer of applied moment as well as enhancement of ductility of reinforced concrete columns. However, T-plate not anchored fully into a column base can seldom transfer the externally applied moment, though it highly improves the ductility of column. The presence of mortar cover for strengthening steel elements is significantly effective in enhancing the initial stiffness and flexural capacity of the strengthened columns, but has an adversely effect on enhancing the ductility. The ultimate moment strength predicted from the extended section laminae method in better agreement with test results compared with predictions obtained using stress black specified in ACI 318-05.

• Structural Engineering and Mechanics
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• v.66 no.2
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• pp.203-215
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• 2018

A large body of experiments have been conducted to date to evaluate the punching shear strength of flat slab-column connections, but it is noted that only a few of them have been considered for the development of the ACI Code provisions. The limited test results used for the development of the code provisions fall short of predicting accurately the punching shear strength of such connections. In an effort to address this shortfall and to gain an insight into the factors that control the punching shear strength of flat slab-column connections, we report a qualified database of 650 punching shear test results in this article. All slabs examined in this database were tested under gravity loading and do not contain shear reinforcement. In order to justify including any test result for evaluation punching shear database, we have developed an approved set of criteria. Carefully established set of criteria represent the actual characteristics of structures that include minimum compressive strength, effective depths of slab, flexural and compression reinforcement ratio and column size. The key parameters that significantly affect the punching shear strength of flat slab-column connections are then examined using ACI 318-14 expression. The results reported here have paramount significance on the range of applicability of the ACI Code provision and seem to indicate that the ACI provisions do not sufficiently capture many trends identified through regression of the principal parameters, and fall on the unsafe side for the prediction of the punching shear strength of flat slab-column connections.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.199-206
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• 2002

The objective of this study is to investigate the seismic behavior and evaluate structural performance of columns in Ordinary Moment Resting Concrete Frames (OMRCF). For this purpose 3 story OMRCF building was designed and detailed in compliance to ACI 318 (1999). Only gravity load is considered for the design. It is important to note that details strongly relate to the structural performance. The 1st story columns in the 3 story building are considered in this study since 다lese columns shall resist the largest axial and lateral forces during an earthquate. Four test specimens were made for representing the upper part and lower part of exterior and interior columns. All specimens are two-third scale. Based on the test results this study estimates deformation, ductility, strength, and energy absorption capacities as well as plastic hinge length.

• Advances in concrete construction
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• v.14 no.5
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• pp.331-339
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• 2022

Geopolymer concrete (GPC) is one of the best substitute materials for conventional concrete in construction. The conventional concrete provided by Portland cement has a detrimental influence on the environment during its production. In this study, the bond strength, which is an important structural property, of deformed steel bars with slag-based GPC was measured. In accordance with the ASTM C234 procedure, bond strength was measured on 18 specimens of slag-based GPC with three sizes of steel bars and different embedded lengths. Two groups of GPC specimens with different compressive strengths, which were cured under ambient conditions, were tested. The results indicated that the bar diameter has a great effect on the bond strength, and the bond strength behavior of the slag-based GPC is comparable with that of conventional concrete. The ACI-318 Code for the bond strength of ordinary Portland cement concrete can be used conservatively to determine the bond strength of the GPC reinforced with deformed steel bars.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.145-150
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• 2019

This paper proposes a model for the calculation of the ultimate torsional strength in normal-strength and high-strength concrete beams which include the concrete contribution strength and use a reasonable thickness of shear flow. The adequacy of the proposed model is evaluated by comparing the calculated torsional strength with the experimentally observed results from 104 test specimens reported in the literature. The results are also compared with the calculations of the KCI and the ACI building code equations, and those of other model which include the concrete contribution strength. The comparisons show that the ultimate torsional strengths calculated by the proposed equation and Rahal's equation are closer to the experimentally observed results than those calculated by the code equations.

• Journal of the Korea Concrete Institute
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• v.29 no.2
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• pp.201-208
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• 2017

In exterior beam-column joints, hooked bars are used for anchorage, but usage of high-strength and large-diameter bars increases, headed bar is preferred for solving steel congestion and difficulty in construction. To investigate the structural performance of headed bars, Six exterior beam-column joints were tested under cyclic loading. Tests parameter were the anchorage methods and concrete strength. The test results indicate that behavior of headed bar specimens shows similar performance with hooked bar specimens. All specimens failed by flexural failure of the beam. Headed bar specimens shows better performance in anchorage and joint shear. All specimens were satisfied the criteria of ACI374.1-05. Test results indicate that use of headed bar in exterior beam column joint is available.

• International Journal of Concrete Structures and Materials
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• v.10 no.2
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• pp.177-188
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• 2016

One of the primary concerns about the design aspects is that how to deal with the shear reinforcement in the ultra-high performance fiber reinforced concrete (UHPFRC) beam. This study aims to investigate the shear behavior of UHPFRC rectangular cross sectional beams with fiber volume fraction of 1.5 % considering a spacing of shear reinforcement. Shear tests for simply supported UHPFRC beams were performed. Test results showed that the steel fibers substantially improved of the shear resistance of the UHPFRC beams. Also, shear reinforcement had a synergetic effect on enhancement of ductility. Even though the spacing of shear reinforcement exceeds the spacing limit recommended by current design codes (ACI 318-14), shear strength of UHPFRC beam was noticeably greater than current design codes. Therefore, the spacing limit of 0.75d can be allowed for UHPFRC beams.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.365-372
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• 2002

This experimental investigation was conducted to examine the behavior of eight a third scale columns made of high-strength concrete(HSC). The columns were subjected to constant axial load corresponding to target value of 30 percent of the column axial load capacity and a cyclic horizontal load-inducing reversed bending moment. The variables studied in this research are the volumetric ratio of transverse reinforcement(Ps=1.58, 2.25 ％), tie configuration(hoop-type, cross-type, diagonal-type) and tie yield strength(fy=5,600, 7,950 kgf/$\textrm{cm}^2$). Test results indicated that the flexural strength of all the columns did not exceed calculated flexural capacities based on the equivalent concrete stress block used in current design code. Columns with 42 percent higher amounts of transverse reinforcement than that required by seismic provisions of ACI 318-99 were shown ductile behavior. With axial load of 30 percent of the axial load capacity, the use of high-strength steel as transverse reinforcement may lead to equal or higher ductility than would be achieved with low-strength steel.