Structural Performance Evaluation of a Precast PSC Curved Girder Bridge Constructed Using Multi-Tasking Formwork

Sung-Jae Kim,Jang-Ho Jay Kim,Seong-Tae Yi,Norhazilan Bin Md Noor,Sung-Chul Kim 한국콘크리트학회 2016 International Journal of Concrete Structures and M Vol.10 No.3

Recently, advanced transit systems are being constructed to reduce traffic congestions in metropolitan areas. For these projects, curved bridges with various curvatures are required. Many curved bridges in the past were constructed using aesthetically unpleasant straight beams with curved slabs or expensive curved steel box girders with curved slabs. Therefore, many recent studies have been performed to develop less expensive and very safe precast prestressed concrete (PSC) curved girder. One method of reducing the construction cost of a PSC curved girder is to use a reusable formwork that can easily be adjusted to change the curvature and length of a girder. A reusable and curvature/dimension adjustable formwork called Multi-tasking formwork is developed for constructing efficient precast PSC curved girders. With the Multi-tasking formwork, two 40 m precast PSC box girders with different curvatures were constructed to build a two-girder curved bridge for a static flexural test to evaluate its safety and serviceability performance. The static flexural test results showed that the initial cracking load was 1400 kN, exceeding the design cracking load of 450 kN. Also, the code allowed deflection of 50 mm occurred at a load of 1800 kN, verifying the safety and serviceability of the precast PSC curved bridge constructed using the multi-tasking formwork.

3D 프린터로 제작된 비정형 거푸집의 최대 측압에 대한 유한요소해석

이정호,주영규,김학범,Lee, Jeong-Ho,Ju, Young K.,Kim, Hak-Beom 한국공간구조학회 2017 한국공간구조학회지 Vol.17 No.4

The F3D(Free-Form Formwork 3D Printer) technology that manufactures EPS(Expanded Polystyrene) formworks for irregular-shaped concrete structures by 3D printers was developed to reduce the cost and time. Because of weak strength and low elastic modulus of the EPS, structural performance including lateral pressure by fresh concrete of the formwork that consisted of EPS should be investigated. In order to calculate lateral pressures acting on formwork, several variables including sizes, shapes of formwork, tangential force(fricition) between fresh concrete and formwork, and material properties of fresh concrete should be considered. However, current regulations have not considered the properties of concrete, only focused on vertical formwork. Galleo introduced 3-dimensional finite element analysis models to calculate lateral pressure on formwork. Thus, proposed finite element analysis model based on previous studies were verified for vertical formwork and irregular-shaped formwork. The test results were compared with those by FEM analysis. As a result, the test agrees well with the analysis.

Structural Performance Evaluation of a Precast PSC Curved Girder Bridge Constructed Using Multi-Tasking Formwork

Kim, Sung-Jae,Kim, Jang-Ho Jay,Yi, Seong-Tae,Noor, Norhazilan Bin Md,Kim, Sung-Chul Korea Concrete Institute 2016 International Journal of Concrete Structures and M Vol.10 No.3

Recently, advanced transit systems are being constructed to reduce traffic congestions in metropolitan areas. For these projects, curved bridges with various curvatures are required. Many curved bridges in the past were constructed using aesthetically unpleasant straight beams with curved slabs or expensive curved steel box girders with curved slabs. Therefore, many recent studies have been performed to develop less expensive and very safe precast prestressed concrete (PSC) curved girder. One method of reducing the construction cost of a PSC curved girder is to use a reusable formwork that can easily be adjusted to change the curvature and length of a girder. A reusable and curvature/dimension adjustable formwork called Multi-tasking formwork is developed for constructing efficient precast PSC curved girders. With the Multi-tasking formwork, two 40 m precast PSC box girders with different curvatures were constructed to build a two-girder curved bridge for a static flexural test to evaluate its safety and serviceability performance. The static flexural test results showed that the initial cracking load was 1400 kN, exceeding the design cracking load of 450 kN. Also, the code allowed deflection of 50 mm occurred at a load of 1800 kN, verifying the safety and serviceability of the precast PSC curved bridge constructed using the multi-tasking formwork.

파이프서포트(V6)의 좌굴특성에 관한 연구

백신원 ( Shin Won Paik ),송인용 ( In Yong Song ) 한국안전학회(구 한국산업안전학회) 2011 한국안전학회지 Vol.26 No.3

Among the accidents and failures that occur during concrete construction, many are formwork failures which usually happen when concrete is being placed. A system of formwork filled with wet concrete has its weight at the top and is not basically a stable structure. Slab formwork consists of sheathing, stringer, hanger and shore. There are several types of adjustable shores. In construction site, pipe supports are usually used as a shore of slab formwork. In this study, pipe support systems with/without horizontal connector were measured by buckling test. Buckling load of respective pipe support system was analyzed by structural analysis program(MIDAS). Buckling load of pipe support with/without horizontal connector was got by test and structural analysis. According to these results, we know that horizontal connector made pipe support system very safe. Buckling load of pipe support with horizontal connector is 56% higher than that without horizontal connector. So horizontal connector is important in slab formwork systems. Finally, the present study results will be used to design slab formwork system safely in the construction sites.

3D 프린터로 제작된 EPS 비정형 거푸집의 유한요소해석을 통한 설계

이정호,주영규 한국복합신소재구조학회 2018 복합신소재구조학회 학술발표회 Vol.2018 No.04

Construction of irregular-shaped concrete structures requires a lot of time and money. To reduce the cost and time, the F3D(Free-Form Formwork 3D Printer) technology was adopted in manufacturing EPS(Expanded Polystyrene) formwork for irregular-shaped concrete structure. To design EPS formwork precisely, lateral pressure acting on irregular-shaped formwork and deformation of EPS form liner should be evaluated. However, in current Korean formwork standard, there are no standards for irregular-shaped formwork as it includes a lot of complex variables. For this reason, several researchers developed 3-dimensional finite element analysis model to calculate lateral pressure exerted by fresh concrete. In this study, deformation of irregular-shaped EPS formwork and lateral pressure acting on formwork was examined using finite element analysis model.

재사용 파이프서포트의 내력변화 연구

백신원,최순주,Baek, Sin-Won,Choe, Sun-Ju 한국건설안전협회 2006 建設 安全技術 Vol.38 No.-

Formwork is a temporary structure that supports its weight and that of freshly placed concrete as well as construction live loads. In constructions site, pipe supports are usually used as shores which are consisted of the stab formwork. The strength of a pipe support is decreasing as it is frequently being used at the construction site. Among the accidents and failures that occur during concrete construction, there are many formwork failures which usually happen at the time concrete is being placed. The objective of this study is to find out the strength change of used pipe support and unused pipe supports according to aging. In this study, 2857 pipe supports were prepared. Among these pipe supports, 2337 pipe supports were lent to the construction companies free of charge. 520 pipe supports were kept on the outside. Compressive strength was measured by knife edge test and plate test at each 3 month. Test results show that the strength of unused pipe supports as well as used pipe supports was decreasing according to age, use frequency and load carrier, and the strength of used pipe supports was lower than the strength of unused pipe supports at the same age. So, the strength of used pipe supports from 191 days to present day was not satisfied the specification of KSF 8001. In this study, the strength of pipe support according to age, use frequency and load carrier was predicted using SPSS 12.0. It was known that the strength of pipe support using for 5 years was reduced to 42.8%. According to these results, it shows that attention has to be paid to formwork design using used pipe supports. Therefore, the present study results will be able to provide a firm base to prevent formwork collapses.

3차원 콘크리트 거푸집의 설계 및 시공성 개선

박성준(Park, Seong-Jun),당고손(Dong, Ngoc Son),강휘랑(Kang, Hwirang),심창수(shim, Chang-Su) 한국BIM학회 2017 KIBIM Magazine Vol.7 No.1

Aesthetic design guidelines of bridges were developed in many countries. As iconic structures, bridges need to be attractive and durable as they serve many generations. In this paper, a new design process of concrete structures considering 3D shapes and texture was proposed. The 3D design needs to consider function, economy, advanced technology, tradition and local culture. 3D printers enable the combination of artistic design and engineering design for concrete structures. Parametric modeling with iconic design was utilized to produce 3D formworks. As a pilot project, a railway bridge girder was designed and the proposed technologies were applied. Detail requirements to improve constructability and quality of concrete surfaces were derived. From the pilot applications, design guidelines were suggested.

FRP판과 현장타설 콘크리트 사이의 단순 부착모델 제안

유승운 한국구조물진단유지관리공학회 2008 한국구조물진단유지관리공학회 논문집 Vol.12 No.1

최근에 상용 FRP 판(plank)을 콘크리트 구조물의 영구 거푸집 및 보강재로 이용하기 위한 연구가 진행되고 있다. FRP 판과 타설 콘크리트가 합성효과를 발휘하기 위해서는 두 재료간의 부착이 중요한 요인 중의 하나이다. 이러한 부착을 확보하기 위하여 FRP 판에 모래를 일반적으로 건설현장에서 많이 사용하는 에폭시를 이용하여 부착하였다. FRP 판과 콘크리트 합성구조의 구조적 거동을 이해하기 위해서는 FRP판과 타설 콘크리트 사이의 정량적인 국부 부착모델이 필요하다. 본 연구에서는 이와 같은 합성구조 시스템에 간단히 적용할 수 있는 단순 부착모델을 제안한다. The use of hybrid FRP-concrete structures with a dual purpose of both permanent formwork and reinforcement, has been considered in some studies recently. For the FRP plank and the concrete to act as a composite structural member a satisfactory bond at the interface between the smooth surface of the pultruded plank and the cast-in-place concrete must be developed. Sand was bonded to the pultruded FRP plank using a commercially available epoxy system. In applying general analysis techniques to evaluate the performance of composite structures with FRP stay-in-place forming, it is essential that characteristics of the bond stress-slip relation be identified. In this study I would like to propose a simplified bilinear bond stress-slip model for FRP composite structures.

표면처리 및 양생 조건이 초고성능 콘크리트-보통 콘크리트 계면 부착강도에 미치는 영향

강성훈,홍성걸 한국구조물진단유지관리공학회 2015 한국구조물진단유지관리공학회 논문집 Vol.19 No.3

이 연구에서는 초고성능 콘크리트 (UHPC)와 보통 콘크리트 (NSC)간 계면부착강도에 관한 연구를 수행하였다. UHPC를 보수⋅보강재 로 활용하기 위한 기존의 부착강도에 관한 연구와 달리, UHPC를 프리캐스트 합성부재로 활용하기 위한 연구에 초점을 맞추었으며, 여기 에 영향을 미칠 수 있는 다양한 요인에 대하여 검토하였다. 기존 연구들을 분석한 결과, UHPC-NSC 계면 부착강도에 영향을 미칠 수 있는 요인으로는 계면의 형상, 합성 전 UHPC의 경화 진행상태, 합성 전 UHPC의 수분 흡수상태, 그리고 합성 후 양생장소와 같이 크게 4가지 로 구분되었다. 계면의 형상을 변수로 한 실험에서는 형상에 따라 각기 다른 파괴모드가 나타났으며, 기존 연구에서 확인되지 않았던 거칠 게 처리한 UHPC 계면 일부가 파괴되는 새로운 파괴모드가 발견되었다. 합성 전 UHPC의 경화진행 상태가 부착강도에 영향을 미치는 것 으로 나타났으며, 이러한 영향은 부착 파괴모드에 따라 다르게 나타났다. 또한, 합성 전 UHPC의 수분상태가 부착강도에 영향을 주었으며, UHPC의 양생방법에 따라 서로 상반되는 결과를 보였다. 마지막으로, 합성한 시편의 양생조건 역시 계면 부착강도에 영향을 미친다는 것 을 확인하였다. This study reports the interfacial bond strength between Ultra High Performance Concrete (UHPC) and Normal Strength Concrete (NSC). While previous studies have focused on the interfacial strength between NSC substrate and UHPC overlay, this study use precast UHPC for enhanced constructability and replacement of formwork. The factors affecting the interface strength are comprehensively reviewed. It can be classified int interface shape, degree of hardening and moisture condition of UHPC before combining with NSC, and curing condition of composite materials. Conducted experiments verify the effects of each factor on the interface strength and, accordingly show different failure modes. In particular, a new failure mode of the failure of a part of UHPC was firstly found in the case of sample with rough interface between UHPC and NSC. The other factors of the degree of hardening and the moisture and curing conditions of UHPC were discussed. This research will provide a valuable foundation to utilize the UHPC as a composite material.

표면처리 및 양생 조건이 초고성능 콘크리트-보통 콘크리트 계면 부착강도에 미치는 영향

강성훈,홍성걸 한국구조물진단유지관리공학회 2015 한국구조물진단유지관리공학회 논문집 Vol.19 No.3

This study reports the interfacial bond strength between Ultra High Performance Concrete (UHPC) and Normal Strength Concrete (NSC). While previous studies have focused on the interfacial strength between NSC substrate and UHPC overlay, this study use precast UHPC for enhanced constructability and replacement of formwork. The factors affecting the interface strength are comprehensively reviewed. It can be classified into: interface shape, degree of hardening and moisture condition of UHPC before combining with NSC, and curing condition of composite materials. Conducted experiments verify the effects of each factor on the interface strength and, accordingly show different failure modes. In particular, a new failure mode of the failure of a part of UHPC was firstly found in the case of sample with rough interface between UHPC and NSC. The other factors of the degree of hardening and the moisture and curing conditions of UHPC were discussed. This research will provide a valuable foundation to utilize the UHPC as a composite material. 이 연구에서는 초고성능 콘크리트 (UHPC)와 보통 콘크리트 (NSC)간 계면부착강도에 관한 연구를 수행하였다. UHPC를 보수⋅보강재로 활용하기 위한 기존의 부착강도에 관한 연구와 달리, UHPC를 프리캐스트 합성부재로 활용하기 위한 연구에 초점을 맞추었으며, 여기에 영향을 미칠 수 있는 다양한 요인에 대하여 검토하였다. 기존 연구들을 분석한 결과, UHPC-NSC 계면 부착강도에 영향을 미칠 수 있는요인으로는 계면의 형상, 합성 전 UHPC의 경화 진행상태, 합성 전 UHPC의 수분 흡수상태, 그리고 합성 후 양생장소와 같이 크게 4가지로 구분되었다. 계면의 형상을 변수로 한 실험에서는 형상에 따라 각기 다른 파괴모드가 나타났으며, 기존 연구에서 확인되지 않았던 거칠게 처리한 UHPC 계면 일부가 파괴되는 새로운 파괴모드가 발견되었다. 합성 전 UHPC의 경화진행 상태가 부착강도에 영향을 미치는 것으로 나타났으며, 이러한 영향은 부착 파괴모드에 따라 다르게 나타났다. 또한, 합성 전 UHPC의 수분상태가 부착강도에 영향을 주었으며, UHPC의 양생방법에 따라 서로 상반되는 결과를 보였다. 마지막으로, 합성한 시편의 양생조건 역시 계면 부착강도에 영향을 미친다는 것을 확인하였다.