Post-fire test of precast steel reinforced concrete stub columns under eccentric compression

Yong Yang,Yicong Xue,Yunlong Yu,Zhichao Gong 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.33 No.1

This paper presents an experimental work on the post-fire behavior of two kinds of innovative composite stub columns under eccentric compression. The partially precast steel reinforced concrete (PPSRC) column is composed of a precast outer-part cast using steel fiber reinforced reactive powder concrete (RPC) and a cast-in-place inner-part cast using conventional concrete. Based on the PPSRC column, the hollow precast steel reinforced concrete (HPSRC) column has a hollow column core. With the aim to investigate the post-fire performance of these composite columns, six stub column specimens, including three HPSRC stub columns and three PPSRC stub columns, were exposed to the ISO834 standard fire. Then, the cooling specimens and a control specimen unexposed to fire were eccentrically loaded to explore the residual capacity. The test parameters include the section shape, concrete strength of inner-part, eccentricity ratio and heating time. The test results indicated that the precast RPC shell could effectively confine the steel shape and longitudinal reinforcements after fire, and the PPSRC stub columns experienced lower core temperature in fire and exhibited higher post-fire residual strength as compared with the HPSRC stub columns due to the insulating effect of core concrete. The residual capacity increased with the increasing of inner concrete strength and with the decreasing of heating time and load eccentricity. Based on the test results, a FEA model was established to simulate the temperature field of test specimens, and the predicted results agreed well with the test results.

Experimental study on shear performance of partially precast Castellated Steel Reinforced Concrete (CPSRC) beams

Yong Yang,Yunlong Yu,Yuxiang Guo,Charles W. Roeder,Yicong Xue,Yongjian Shao 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.2

A new kind of partially precast or prefabricated castellated steel reinforced concrete beam, which is abbreviated here as CPSRC beam, was presented and introduced in this paper. This kind of CPSRC beam is composed of a precast outer-part and a cast-in-place inner-part. The precast outer-part is composed of an encased castellated steel shape, reinforcement bars and high performance concrete. The cast-in-place inner-part is made of common strength concrete, and is casted with the floor slabs simultaneously. In order to investigate the shear performance of the CPSRC beam, experiments of six CPSRC T-beam specimens, together with experiments of one cast-in-place SRC control T-beam specimen were conducted. All the specimens were subjected to sagging bending moment (or positive moment). In the tests, the influence of casting different strength of concrete in the cross section on the shear performance of the PPSRC beam was firstly emphasized, and the effect of the shear span-to-depth ratio on that were also especially taken into account too. During the tests, the shear force-deflection curves were recorded, while the strains of concrete, the steel shapes as well as the reinforcement stirrups at the shear zone of the specimens were also measured, and the crack propagation pattern together with the failure pattern was as well observed in detail. Based on the test results, the shear failure mechanism was clearly revealed, and the effect of the concrete strength and shear span-to-depth ratios were investigated. The shear capacity of such kind of CPSRC was furthermore discussed, and the influences of the holes on the steel shape on the shear performance were particularly analyzed.

In-Plane Quasi-Static Cyclic Tests on Emulative Precast Concrete Walls

Zhu Zhangfeng,Guo Zhengxing 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.8

This paper presents two types of emulative precast concrete walls with dry horizontal connection and semi-dry horizontalconnection. As for dry connection, vertical continuity reinforcing bars are grouted in metal bellows embedded in the precast wallpanel. As for semi-dry connection, the web reinforcing bars are still grouted in embedded metal bellows while the reinforcing barswithin boundary elements are overlapped and anchored in cast-in-place concrete. To assess the seismic performance of the twoconnections, three full-scale specimens, including one reference monolithic specimen and two precast specimens for eachconnection, were prefabricated and tested under in-plane quasi-static cyclic loading. The strength, stiffness, displacement ductility,and energy dissipation of the specimens were measured and compared. The experimental results demonstrated that, compared withthe monolithic specimen, both precast specimens exhibited satisfactory behavior and the semi-dry precast specimen performed betterthan the dry precast specimen in terms of ductility and energy dissipation. In addition, the analytical results showed that precastspecimens exhibited reliable seismic performance with high bearing capacity and large deformation capacity.

원심성형 철근콘크리트 말뚝 이음부의 보강 효과

주상훈,황훈희 한국산학기술학회 2019 한국산학기술학회논문지 Vol.20 No.11

The construction of foundation piles for buildings and bridges is changing from pile driving to an injected precast pile method. The goal is to minimize environmental damage, noise pollution, and complaints from neighboring residents. However, it is necessary to develop economic piles that are optimized for precasting by a centrifugal method in terms of both the material and structural system. A reinforced joint method is proposed for reinforced concrete piles (RC piles) manufactured by centrifugal casting. A previous study concluded that the structural performance of the current joint system for RC piles could be improved by using a reinforced joint composed of extended circular band plates and studs. In this study, the structural performance of such a joint was validated experimentally by bending and shear strength measurements. The proposed joint reinforcement method showed adequate structural performance in terms of bending and shear strength. The overall load-deflection behavior is close to that of a structure without joints, so it is expected that the behavior and performance of the design can be reliably reflected in site structures. 최근 건축과 토목 구조물 기초에 적용되는 말뚝의 시공법은 환경 훼손, 소음 공해, 그리고 주위 민원을 최소화하기 위해 항타공법에서 매입공법 위주로 변화하는 추세를 보이고 있다. 이러한 시공방법의 변화로 인해 기존의 항타공법으로 사용되었던 말뚝 대신, 재료 및 구조적인 시스템 측면에서 보다 최적화되고 경제적인 매입용 말뚝의 개발이 요구되고 있다. 본 연구에서는 매입용 말뚝인 원심성형 철근콘크리트 말뚝의 보강된 이음방법을 제안하였다. 이전의 연구에서는 원심성형 철근콘크리트 말뚝에 대해 연장된 원형띠판과 스터드로 구성된 이음 보강방법이 기존 이음방법의 구조성능을 개선 시킬 수 있을 것으로 검토되었다. 따라서, 본 연구에서는 이러한 이음방법의 구조성능을 말뚝의 휨과 전단 강도 실험을 통해 검증하였다. 이 제안된 이음방법은 설계에서 요구되는 휨과 전단 강도에 대해 충분한 성능을 보인 것으로 실험에서 나타났다. 또한, 전반적인 하중-처짐 거동이 이음부가 없는 일체형 구조에 근접하므로 설계에서 예상하는 거동과 성능이 안정적으로 현장 구조물에 반영될 수 있을 것으로 기대된다.

Experimental and numerical studies of precast connection under progressive collapse scenario

Joshi, Digesh D.,Patel, Paresh V.,Rangwala, Husain M.,Patoliya, Bhautik G. Techno-Press 2020 Advances in concrete construction Vol.9 No.3

Progressive collapse in a structure occurs when load bearing members are failed and the adjoining structural elements cannot resist the redistributed forces and fails subsequently, that leads to complete collapse of structure. Recently, construction using precast concrete technology is adopted increasingly because it offers many advantages like faster construction, less requirement of skilled labours at site, reduced formwork and scaffolding, massive production with reduced amount of construction waste, better quality and better surface finishing as compared to conventional reinforced concrete construction. Connections are the critical elements for any precast structure, because in past, major collapse of precast structure took place because of connection failure. In this study, behavior of four different precast wet connections with U shaped reinforcement bars provided at different locations is evaluated. Reduced 1/3^rd scale precast beam column assemblies having two span beam and three columns with removed middle column are constructed and examined by performing experiments. The response of precast connections is compared with monolithic connection, under column removal scenario. The connection region of test specimens are filled by cast-in-place micro concrete with and without polypropylene fibers. Performance of specimen is evaluated on the basis of ultimate load carrying capacity, maximum deflection at the location of removed middle column, crack formation and failure propagation. Further, Finite element (FE) analysis is carried out for validation of experimental studies and understanding the performance of structural components. Monolithic and precast beam column assemblies are modeled using non-linear Finite Element (FE) analysis based software ABAQUS. Actual experimental conditions are simulated using appropriate boundary and loading conditions. Finite Element simulation results in terms of load versus deflection are compared with that of experimental study. The nonlinear FE analysis results shows good agreement with experimental results.

Experimental Study on Emulative Hybrid Precast Concrete Shear Walls

Zhu Zhangfeng,Guo Zhengxing 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.1

The reversed cyclic lateral loading experiments were conducted on three, full scale, emulative hybrid precast concrete shear wall specimens with different post-tensioned forces and one reference monolithic RC shear wall specimen, and the measured results were then discussed in this paper. The emulative hybrid wall combined grouted vertical reinforcements with unbonded post-tensioned high-strength multi-strand tendons for lateral resistance, attempting to emulate the cast-in-place RC wall. Because of the presence of the unbonded post-tensioned tendon, by contrast to the monolithic wall specimen, the emulative hybrid wall specimens possessed higher strength, higher stiffness, and smaller residual displacement. The opening gap, resulted from the discontinuity of concrete and the locally debonding of vertical connecting reinforcements, was limited mainly due to the vertical connecting reinforcements across the joint distributed over total cross-section. Meanwhile, the emulative hybrid wall specimens were capable of providing energy dissipation and ductility capacity comparable to that of the monolithic specimen, and the negative effect of the post-tensioned force on energy dissipation was more obvious than on ductility. Moreover, the post-tensioned tendon remained elastic throughout the test and the yielding of the connecting reinforcements was delayed.

직접전단 시험을 통한 분리타설된 강섬유 보강 콘크리트의 전단마찰강도 분석

이혜원(Lee, Hye-Won),손동희(Son, Dong-Hee),배백일(Bae, Baek-Il),최창식(Choi, Chang-Sik) 대한건축학회 2023 대한건축학회논문집 Vol.39 No.10

When precast concrete elements and cast-in-place concrete are formed separately, they create shear friction at their interface. Ensuring structural integrity is vital, and this involves placing shear friction reinforcement at this interface. Steel fibers are recognized for enhancing shear strength by leveraging the dowel action of shear friction reinforcements, and shear friction capacity can be improved by using steel fibers locally. In this study, 12 push-off tests were conducted to assess how steel fiber reinforced concrete (SFRC) contributes to shear friction strength in direct shear. The experimental findings were also compared with the predicted values from current code provisions. These experiments revealed that the crack width at maximum shear friction strength increased as the volume of steel fibers increased, and the contribution of concrete also increased with higher steel fiber volume. Notably, Eurocode 2 yielded higher contributions compared to AASHTO LRFD. Eurocode 2, which takes into account concretes tensile strength, provided the most accurate results. Therefore, future studies should consider the influence of concrete when designing for shear friction strength.

Theoretical and experimental study on shear strength of precast steel reinforced concrete beam

Yong Yang,Yicong Xue,Yunlong Yu 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.32 No.4

With the aim to put forward the analytical model for calculating the shear capacity of precast steel reinforced concrete (PSRC) beams, a static test on two full-scale PSRC specimens was conducted under four-point loading, and the failure modes and strain developments of the specimens were critically investigated. Based on the test results, a modified truss-arch model was proposed to analyze the shear mechanisms of PSRC and cast-in-place SRC beams. In the proposed model, the overall shear capacity of PSRC and cast-in-place SRC beams can be obtained by combining the shear capacity of encased steel shape with web concrete determined by modified Nakamura and Narita model and the shear capacity of reinforced concrete part determined by compatible truss-arch model which can consider both the contributions of concrete and stirrups to shear capacity in the truss action as well as the contribution of arch action through compatibility of deformation. Finally, the proposed model is compared with other models from JGJ 138 and AISC 360 using the available SRC beam test data consisting of 75 shear-critical PSRC and SRC beams. The results indicate that the proposed model can improve the accuracy of shear capacity predictions for shear-critical PSRC and cast-in-place SRC beams, and relatively conservative results can be obtained by the models from JGJ 138 and AISC 360.

Seismic Isolation Systems Incorporating with RC Core Walls and Precast Concrete Perimeter Frames -Shimizu Corporation Tokyo Headquarter-

Shimazaki, Dai,Nakagawa, Kentaro Council on Tall Building and Urban Habitat Korea 2015 International journal of high-rise buildings Vol.4 No.3

Shimizu Corporation Tokyo Headquarters, one of the city's leading office buildings, features many pioneering technologies that contribute to a sustainable society through environmental stewardship and a sophisticated disaster management facility. In terms of structural engineering, a seismic isolation system incorporating reinforced concrete core walls and precast concrete perimeter frames create a robust structure in the event of a large earthquake. In addition to the seismic resistance of the structure, several pioneering construction methods and materials are adopted. This office building can serve as a basis for new design and construction approaches and methodologies to ensure safe and economical structures.

PC 및 RC공동주택 골조공사에 대한 공사기간 절대비교

김기호 ( Kim Ki-ho ),이범식 ( Lee Bum-sik ),김진원 ( Kim Jin-won ),김연호 ( Kim Yeon-ho ),이동건 ( Lee Dong-gun ),손정락 ( Sohn Jeong-rak ) 한국건축시공학회 2023 한국건축시공학회 학술발표대회 논문집 Vol.23 No.1

In accordance with recent changes in construction trends, interest in introducing the OSC, such as the Precast Concrete, is increasing in apartment buildings. In domestic studies, studies on the prediction of the construction period of PC apartment buildings through simulation have been conducted, but there is no study on the comparison of the construction period according to the actual construction of Precast Concrete(PC) and Reinforced Concrete(RC). Therefore, this study seeks to grasp the technology of the current PC construction method and to secure the original technology of project management through comparison of the absolute time of frame construction for PC and RC buildings composed of the same plane.