• Journal of Korean Society of Steel Construction
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• v.27 no.1
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• pp.87-97
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• 2015

In this study, an experimental study was performed to evaluate the concrete breakout strength of cast-in-place(CIP) anchors in cracked concrete under static shear loading. The CIP anchors involved in this study were 30mm in diameter with an edge distance of 150mm and an embedment length of 240mm. The experiment was carried out for two specimens in uncracked concrete and three specimens in cracked concrete orthogonal and parallel to the direction of shear loading, respectively. Compared to the uncracked concrete specimen, cracked specimen orthogonal to the direction of shear loading showed no reduction in the concrete breakout strength and that parallel to the load direction about 91% strength which corresponds to 84% of uncracked concrete strength defined in ACI 318-11. Therefore, the experimental results showed smaller decrease in the shear resistance of CIP anchors in cracked concrete than that specified in ACI code which account for 71% strength of uncracked concrete in cracked concrete.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.2
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• pp.171-175
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• 2019

Mandible with severe alveolar bone atrophy poses a significant challenge in terms of reproducing clinically acceptable anatomy for a removable prosthesis. To overcome this potential complication, altered cast impression technique is often recommended to capture accurate and functional gingiva tissues. It becomes possible to get proper anchors functional impression by placing 2 implants crowns which were impossible in previous implant overdenture impression technique. In this case, an 80-year old female patient with severe mandibular ridge atrophy was treated with an implant-assisted removable partial denture with two implant crowns on the canine area. An altered cast impression was taken with an individual tray on a metal framework of removable partial denture on both posterior edentulous areas. The patient was satisfied with the final prosthesis after failure of 2 previous prostheses. Clinician had a difficult time to manage disabled patient and patient were suffered with ill-fitting denture due to inaccurate impression in conventional overdenture condition. The oral rehabilitation was completed with placing 2 implants as proper anchor.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.151-152
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• 2020

Recently, concrete expansion anchors which are a type of post-installed mechanical anchors are widely used in reinforcement concrete structures. In order to be used in the reinforced concrete structures designed in accordance with ACI 318-19 or ACI 349-13, the structural performance tests of the concrete expansion anchors should be conducted in accordance with ACI 355.2. The effectiveness factor(k) of concrete expansion anchors should be determined through the reference tests and used for the design of anchorage to concrete according to ACI 318-19 or ACI 349-13. In this study, we will look into the method for determining the effectiveness factor(k) of concrete expansion anchors and anchorage design process of concrete expansion anchors by using the effectiveness factor(k) in accordance with ACI 349-19.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.225-226
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• 2022

The construction industry, which has a labour-intensive and conservative nature, is exclusive to adopt new technologies. However, the construction industry is viably introducing the 4th Industrial Revolution technologies represented by artificial intelligence, Internet of Things, robotics and unmanned transportation to promote change into a smart industry. An image-based artificial intelligence technology is a field of computer vision technology that refers to machines mimicking human visual recognition of objects from pictures or videos. The purpose of this article is to explore image-based artificial intelligence technologies which would be able to apply to the construction sites. In this study, we show two examples which is one for a construction waste classification model and another for cast in-situ anchor bolts defection detection model. Image-based intelligence technologies would be used for various measurement, classification, and detection works that occur in the construction projects.

• Journal of Korean Society of Steel Construction
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• v.17 no.1 s.74
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• pp.93-102
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• 2005

Manufacturing conventional column base plate requires much manpower and time. In this research, a new method for constructing column base plate is introduced to improve on conventional methods through the use ofcast steel that is available for adjusting base plate thickness and enlarging base plate stiffness. The main purposes include reducing welding work, enlarging base plate stiffness, and clarifying the stress flow. Also, construction convenience and improvement in quality can be expected. For developing this cast steel base plate, test specimens of conventional and cast steel base plates are made and tested to analyze strength and stiffness. Also, the efficiency for long-term use is checked by fatigue tests. From these comparative tests, cast steel base plates have the same strength and stiffness as conventional base plates.

• Journal of Korean Society of Steel Construction
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• v.27 no.3
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• pp.347-357
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• 2015

In this study, an experimental study was performed to evaluate the concrete breakout strength of unreinforced cast-in-place anchors by seismic qualification test under shear loading. The CIP anchors tested herein were 30mm in diameter with an edge distance of 150mm and an embedment depth of 240mm in uncracked and cracked concrete. The cracked specimen consisted of orthogonal and parallel crack to the loading direction, respectively. The dynamic loading sequence during the seismic qualification test was determined based on CSA N287.2, ACI 355.2 and ETAG 001 codes. After the dynamic loading, the static loading was applied until failure occurs. The shear resistance by seismic qualification tests showed almost the same strength as that obtained from the static tests in uncrcaked and cracked concrete, respectively. Meanwhile, the breakout depth did not reach $8d_0$, therefore the modified strength equation of ACI 318-11 could estimate properly the concrete breakout strength, which does not consider effective bearing length.

• Steel and Composite Structures
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• v.36 no.3
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• pp.321-337
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• 2020

Contemporary design and construction of steel-concrete composite structures employs the use of prefabricated concrete elements and demountable shear connectors in order to reduce the construction time and costs and enable dismantling of elements for their potential reuse at the end of life of buildings. Bolted shear connector with mechanical coupler is presented in this paper. The connector is assembled from mechanical coupler and rebar anchor, embedded in concrete, and steel bolt, used for connecting steel to concrete members. The behaviour and ultimate resistance of bolted connector with mechanical coupler in wide and narrow members were analysed based on push-out tests and FE analyses conducted in Abaqus software, with focus on concrete edge breakout and bolt shear failure modes. The effect of concrete strength, concrete edge distance and diameter and strength of bolts on failure modes and shear resistance was analysed. It was demonstrated that premature failure by breakout of concrete edge occurs when connectors are located 100 mm or closer from the edge in low-strength and normal-strength reinforced concrete. Furthermore, the paper presents a relatively simple model for hand calculation of concrete edge breakout resistance when bolted connectors with mechanical coupler are used. The model is based on the modification of prediction model used for cast-in and post-installed anchors loaded parallel to the edge, by implementing equivalent influence length of connector with variable diameter. Good agreement with test and FE results was obtained, thus confirming the validity of the proposed method.

• Journal of the Society of Disaster Information
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• v.12 no.4
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• pp.366-372
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• 2016

Recently in case of the concrete retaining wall precast technological change in the field assembled by the way. A precast wall is devied into upper and lower respectively, and the way, assembled in field is being performed. But the assembled part could have been damaged by the earth pressure in a relatively high buttress wall. And, it have been pointed out that large-scale disaster can be occurred. Thus, in this thesis, a structural stability for the buttressed retaining wall with pre-cast joint method was analyzed by a numerical analysis method. The structural stability of the three height retaining wall(7.6m, 8.5m, 10m) was conducted respectively for earth pressure. The maximum principal stress applied to the concrete retaining wall was analyzed to occur locally in the vicinity of the fixing anchor as 23.3 ~ 43.2 MPa.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.3
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• pp.127-135
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• 2019

The seismic performance of non-ductile reinforced concrete (RC) frame retrofitted with H-beam frame and cast expansive mortar into joint between existing RC frame and H-beam frame is investigated experimentally and analytically. RC frames considered in the study contain non-ductile reinforcement details of low-rise school building constructed in Korea before 1988. The tests were conducted on half-scale specimens simulating the lower frame assemblages of a typical school building. Two one-bay, one-story RC frames with and without retrofitting with H-beam frame and expansive joint mortar were tested to failure. Test and analysis results indicated that seismic strengthening using H-beam and expansive joint mortar significantly improved the lateral strength and stiffness of non-ductile RC frame without installing anchor bolts to fit H-beam frame into existing RC frame. The effectiveness of seismic strengthening technology proposed in the study for non-ductile RC frame was verified experimentally and analytically.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.5
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• pp.453-467
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• 2012

Usage of underground space is increasing at metropolitan city. More than 90% of flood damages have occurred at downtown of metropolitan cities. In order to prevent and/or minimize the flood-induced damage, an underground rainwater detention cavern was proposed to be built underneath existing structures. As for underground caverns to be built for flood control, multi-caverns will be mostly adopted rather than one giant cavern because of stability problem. Because of the stress concentration occurring in the pillars between two adjacent caverns, the pillar-stability is the Achilles' heel in multi-caverns. So, a new pillar-reinforcing technology was proposed in this paper for securing the pillar-stability. In the new pillar-reinforcing technology, reinforced materials which are composed of a steel bar and PC strands are used by applying pressurized grouting, and then, by applying the pre-stress to the PC strands and anchor body. Therefore, this new technology has an advantage of utilizing most of the strength that the in-situ ground can exert, and not much relying on the pre-cast concrete structure. The main effect of the pressurized grouting is the increase of the ground strength and more importantly the decrease of stress concentration in the pillar; that of the pre-stress is the increase of the ground strength due to the increase of the internal pressure. In this paper, ground reinforcing effects were verified the stress change in pillar is obtained by numerical analysis at each construction stage. From these results, the effects of pressurized grouting and pre-stress are verified.