Effect of Varying Top Beam Reinforcement Anchorage Details on Ductility of HSC Beam-Column Joints

Ali Ahmed,Muhammad Mazhar Saleem,Zahid Ahmad Siddiqui 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.5

The ductility of external beam-column joints effects seismic behavior of a structure and can be a reason for structural collapse. High strength concrete and large amount of steel present in the joint region reduces the ductility even further. This study presents a radical way of increasing high strength concrete external beam-column joint’s ductility by varying the beam top reinforcement detailing. Two types of joints (three specimens each) were tested, type-1 specimens were prepared as per regular standards while type-2 specimens were prepared by reducing the beam’s top reinforcement anchoring in the column. Load-deflection behavior was studied to observe the stiffness degradation and energy dissipation by joints. Experimental results demonstrated that type-2 specimens were considerably more ductile as compared to type-1 specimens. The energy dissipated by type-2 joints (with 40% less reinforcing bar area in the beam) was 41.5% more than type-1 joints without substantial stiffness degradation. Furthermore, it was observed that by reducing the steel reinforcement in beam, the cracks location changed from inside the joint to beam-column joint’s face which may be attributed for increased ductility in type-2 joints. This study shows that by changing the steel reinforcement detailing near external beam-column joints, fatigue behavior and energy absorption capacity can be enhanced hence providing better performance against seismic activities.

Influence of High Column Axial Loads in Exterior R/C Beam-Column Joints

Vladimir Guilherme Haach,Ana Lucia Homce De Cresce El Debs,Mounir Khalil El Debs 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.2

Joints are problematic regions to study and to build because they generally present high steel ratio in reduced geometricaldimensions. Column axial load is one among several variables that influence the behavior of the exterior beam-column joints. Thispaper investigates the influence of the column axial load on the reinforced concrete exterior beam-column joints throughexperimental tests and compares the results with some theoretical methods of failure prediction. Three exterior beam-columnconnections, with the same geometrical properties are tested applying different levels of column axial loads. Then, an analysis ofreinforcement strains and cracking pattern of the joints is presented in an attempt to better explain the behavior of the exterior beamcolumnjoints. Design models are applied to the experimental specimens and their results are compared. The present study indicatesthat the column axial loads influence the failure mode and further research on this topic is necessary to ensure more accuracy of thedesign models in the prediction of the ultimate failure load of beam column joints.

Classification of failure mode and prediction of shear strength for reinforced concrete beam-column joints using machine learning techniques

Mangalathu, Sujith,Jeon, Jong-Su Elsevier 2018 ENGINEERING STRUCTURES Vol.160 No.-

<P><B>Abstract</B></P> <P>Beam-column joints are one of critical components that control the oveerall performance of reinforced concrete building frames under seismic loadings. To identify the response mechanism, including the classification of failure mode and the prediction of associated shear strength, of beam-column joints, this paper introduces the application of machine learning techniques. The efficiency of various machine learning techniques is evaluated using extensive experimental data from 536 experimental tests, all of which exhibited either non-ductile joint shear failure prior to beam yielding or ductile joint shear failure after beam yielding. It has been seen from the comparison that lasso regression has a better efficiency and reasonable accuracy in the classification and prediction. The suggested formulations as a function of influential input variables can be easily used by structural engineers to provide an optimal rehabilitation strategy for existing buildings and to design new structures.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Identification of mode of failure of beam-column joints through machine learning techniques. </LI> <LI> Probabilistic models to capture the type of failure and shear strength of beam-column joints. </LI> <LI> Sensitivity of input variables to joint shear strength. </LI> <LI> Comparison of various machine learning techniques to estimate the shear strength of beam-column joints. </LI> </UL> </P>

Seismic performance of exterior R/C beam-column joint under varying axial force

Yanbing Hu,Masaki Maeda,Yusuke Suzuki,Kiwoong Jin 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.78 No.5

Previous studies have suggested the maximum experimental story shear force of beam-column joint frame does not reach its theoretical value due to beam-column joint failure when the column-to-beam moment capacity ratio was close to 1.0. It was also pointed out that under a certain amount of axial force, an axial collapse and a sudden decrease of lateral load-carrying capacity may occur at the joint. Although increasing joint transverse reinforcement could improve the lateral load-carrying capacity and axial load-carrying capacity of beam-column joint frame, the conditions considering varying axial force were still not well investigated. For this purpose, 7 full-scale specimens with no-axial force and 14 half-scale specimens with varying axial force are designed and subjected to static loading tests. Comparing the experimental results of the two types of specimens, it has indicated that introducing the varying axial force leads to a reduction of the required joint transverse reinforcement ratio which can avoid the beam-column joint failure. For specimens with varying axial force, to prevent beam-column joint failure and axial collapse, the lower limit of joint transverse reinforcement ratio is acquired when given a column-to-beam moment capacity ratio.

Experimental study on seismic behavior of exterior composite beam-to-column joints with large size stiffened angles

Peng Wang,Zhan Wang,Jianrong Pan,Bin Li,Bo Wang 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.37 No.1

The top-and-seat angles with double web angles are commonly used in the design of beam-to-column joints in Asian and North American countries. The seismic behavior analysis of these joints with large cross-section size of beam and column (often connected by four or more bolts) is a challenge due to the effects from the relatively larger size of stiffened angles and the composite action from the adjacent concrete slab. This paper presents an experimental investigation on the seismic performance of exterior composite beam-to-column joints with stiffened angles under cyclic loading. Four full-scale composite joints with different configuration (only one specimen contain top angle in concrete slab) were designed and tested. The joint specimens were designed by considering the effects of top angles, longitudinal reinforcement bars and arrangement of bolts. The behavior of the joints was carefully investigated, in terms of the failure modes, slippage, backbone curves, strength degradation, and energy dissipation abilities. It was found that the slippage between top-and-seat angles and beam flange, web angle and beam web led to a notable pinching effect, in addition, the ability of the energy dissipation was significantly reduced. The effect of anchored beams on the behavior of the joints was limited due to premature failure in concrete, the concrete slab that closes to the column flange and upper flange of beam plays an significant role when the joint subjected to the sagging moment. It is demonstrated that the ductility of the joints was significantly improved by the staggered bolts and welded longitudinal reinforcement bars.

CFRP 그리드-ECC 블록으로 보강된 외장 RC 빔-기둥 접합부의 성능 평가

팍멩하이 ( Phoeuk Menghay ),최동영 ( Choi Dong-yeong ),정연준 ( Jeong Yeon-jun ),이인 ( Lee In ),권민호 ( Kwon Minho ) 한국구조물진단유지관리공학회 2023 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.27 No.1

The reinforced concrete beam-column joint is susceptible to failure during earthquakes especially the joint of the structure built prior to the 1970s due to poor reinforcement detailing which was inadequate to ensure strong column-weak beam behavior. The failure of the beam-column joint can induce large lateral displacement. Furthermore, it can also lead to the progressive collapse of the whole structure. To prevent such accidents, the beam-column joint has been retrofitted to enhance the performance of the member in terms of strength and ductility. The failure mode is also expected to shift away from joint area. Hence, in this study, two cross-shaped beam-column joint specimens representing the exterior joint of the structure built in the late 1950s in New Zealand were fabricated on a 5/8 scale. One specimen was used as a reference specimen, and another one was retrofitted by CFRP grid-ECC block at the joint area. The purpose of this study is to make the RC beam-column joint stronger by keeping the dimensions of the column the same. As a result, it demonstrated that the joint became stronger and more ductile. The retrofitted specimen could also withstand the lateral displacement much longer than the reference specimen.

Seismic resistance and mechanical behaviour of exterior beam-column joints with crossed inclined bars

Bakir, P.G. Techno-Press 2003 Structural Engineering and Mechanics, An Int'l Jou Vol.16 No.4

Attempts at improving beam-column joint performance has resulted in non-conventional ways of reinforcement such as the use of the crossed inclined bars in the joint area. Despite the wide accumulation of test data, the influence of the crossed inclined bars on the shear strength of the cyclically loaded exterior beam-column joints has not yet been quantified and incorporated into code recommendations. In this study, the investigation of joints has been pursued on two different fronts. In the first approach, the parameters that influence the behaviour of the cyclically loaded beam-column joints are investigated. Several parametric studies are carried out to explore the shear resisting mechanisms of cyclically loaded beam-column joints using an experimental database consisting of a large number of joint tests. In the second approach, the mechanical behaviour of joints is investigated and the equations for the principal tensile strain and the average shear stress are derived from joint mechanics. It is apparent that the predictions of these two approaches agree well with each other. A design equation that predicts the shear strength of the cyclically loaded exterior beam-column joints is proposed. The design equation proposed has three major differences from the previously suggested design equations. First, the influence of the bond conditions on the joint shear strength is considered. Second, the equation takes the influence of the shear transfer mechanisms of the crossed inclined bars into account and, third, the equation is applicable on joints with high concrete cylinder strength. The proposed equation is compared with the predictions of the other design equations. It is apparent that the proposed design equation predicts the joint shear strength accurately and is an improvement on the existing code recommendations.

Dynamic experimental study on single and double beam-column joints in steel traditional-style buildings

Xue, Jianyang,Qi, Liangjie,Yang, Kun,Wu, Zhanjing Techno-Press 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.5

In order to study the failure mode and seismic behavior of the interior-joint in steel traditional-style buildings, a single beam-column joint and a double beam-column joint were produced according to the relevant building criterion of ancient architectural buildings and the engineering instances, and the dynamic horizontal loading test was conducted by controlling the displacement of the column top and the peak acceleration of the actuator. The failure process of the specimens was observed, the bearing capacity, ductility, energy dissipation capacity, strength and stiffness degradation of the specimens were analyzed by the load-displacement hysteresis curve and backbone curve. The results show that the beam end plastic hinge area deformed obviously during the loading process, and tearing fracture of the base metal at top and bottom flange of beam occurred. The hysteresis curves of the specimens are both spindle-shaped and plump. The ultimate loads of the single beam-column joint and double beam-column joint are 48.65 kN and 70.60 kN respectively, and the equivalent viscous damping coefficients are more than 0.2 when destroyed, which shows the two specimens have great energy dissipation capacity. In addition, the stiffness, bearing capacity and energy dissipation capacity of the double beam-column joint are significantly better than that of the single beam-column joint. The ductility coefficients of the single beam-column joint and double beam-column joint are 1.81 and 1.92, respectively. The cracks grow fast when subjected to dynamic loading, and the strength and stiffness degradation is also degenerated quickly.

Effect of geometrical configuration on seismic behavior of GFRP-RC beam-column joints

Ghomia, Shervin K.,El-Salakawy, Ehab Techno-Press 2020 Advances in concrete construction Vol.9 No.3

Glass fiber-reinforced polymer (GFRP) bars have been introduced as an effective alternative for the conventional steel reinforcement in concrete structures to mitigate the costly consequences of steel corrosion. However, despite the superior performance of these composite materials in terms of corrosion, the effect of replacing steel reinforcement with GFRP on the seismic performance of concrete structures is not fully covered yet. To address some of the key parameters in the seismic behavior of GFRP-reinforced concrete (RC) structures, two full-scale beam-column joints reinforced with GFRP bars and stirrups were constructed and tested under two phases of loading, each simulating a severe ground motion. The objective was to investigate the effect of damage due to earthquakes on the service and ultimate behavior of GFRP-RC moment-resisting frames. The main parameters under investigation were geometrical configuration (interior or exterior beam-column joint) and joint shear stress. The performance of the specimens was measured in terms of lateral load-drift response, energy dissipation, mode of failure and stress distribution. Moreover, the effect of concrete damage due to earthquake loading on the performance of beam-column joints under service loading was investigated and a modified damage index was proposed to quantify the magnitude of damage in GFRP-RC beam-column joints under dynamic loading. Test results indicated that the geometrical configuration significantly affects the level of concrete damage and energy dissipation. Moreover, the level of residual damage in GFRP-RC beam-column joints after undergoing lateral displacements was related to reinforcement ratio of the main beams.

Dynamic experimental study on single and double beam-column joints in steel traditional-style buildings

Jian-yang Xue,Liangjie Qi,Kun Yang,Zhanjing Wu 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.5

In order to study the failure mode and seismic behavior of the interior-joint in steel traditional-style buildings, a single beam-column joint and a double beam-column joint were produced according to the relevant building criterion of ancient architectural buildings and the engineering instances, and the dynamic horizontal loading test was conducted by controlling the displacement of the column top and the peak acceleration of the actuator. The failure process of the specimens was observed, the bearing capacity, ductility, energy dissipation capacity, strength and stiffness degradation of the specimens were analyzed by the load-displacement hysteresis curve and backbone curve. The results show that the beam end plastic hinge area deformed obviously during the loading process, and tearing fracture of the base metal at top and bottom flange of beam occurred. The hysteresis curves of the specimens are both spindle-shaped and plump. The ultimate loads of the single beam-column joint and double beam-column joint are 48.65 kN and 70.60 kN respectively, and the equivalent viscous damping coefficients are more than 0.2 when destroyed, which shows the two specimens have great energy dissipation capacity. In addition, the stiffness, bearing capacity and energy dissipation capacity of the double beam-column joint are significantly better than that of the single beam-column joint. The ductility coefficients of the single beam-column joint and double beam-column joint are 1.81 and 1.92, respectively. The cracks grow fast when subjected to dynamic loading, and the strength and stiffness degradation is also degenerated quickly.