Behavior Of Beam-column Joints Research Articles

PROGRESSIVE COLLAPSE ANALYSIS OF UNBONDED POST-TENSIONED PRECAST RC FRAME STRUCTURES USING COLUMN REMOVAL METHOD

To study the behavior of beam-column joints and the progressive collapse performance of unbonded post-tensioned precast concrete frame structures, finite element models were established in OpenSEES and compared with experimental results. With the established beam-column joint models, a six-story unbonded post-tensioned precast concrete frame and a cast-in-place concrete frame with similar structural configurations were simulated. Progressive collapse analysis was performed for these two kinds of frames using column removal method. Results of the numerical analysis show that, with the interior column removed, the ultimate load at failure of the post-tensioned precast frame is 24.2% higher than that of the cast-in-place frame; the percentage increased to 35.7% if an exterior column is removed. Removal of an exterior column is more likely to cause a progressive collapse than removal of an interior column. The results also show that with the same reinforcement layout of the column and the same flexural capacity of the beam, the post-tensioned precast RC frame exhibit better collapse-resisting performance than the cast-in-place RC frame.

Experimental behavior of beam-column joints made with EAF concrete under cyclic loading

This paper presents the results of an experimental campaign carried on exterior beam-column joints made with recycled concrete, containing Electric Arc Furnace (EAF) slag as full replacement of coarse natural aggregates. Three real-scale joints, one made with a conventional mix and two with EAF slag concrete, were tested under horizontal reversed cyclic loading, applied in quasi-static conditions. The three joints exhibited the same failure mode, which involved shear failure of panel joint and yielding of beams steel bars. This failure mode is indeed mainly influenced by concrete strength and was chosen to better highlight the influence of EAF slag use. Similar hysteresis response, stiffness decay, dissipated energy and ductility were obtained both with the conventional and EAF concrete joints. Results demonstrate that the specimens made with EAF concrete are able to attain higher loads than the conventional specimen at the same imposed displacement, and that the panel joint is less damaged.

Effect of Fibres on Beam Column Joint Failure

Concrete is one of the most resourceful and environmental friendly building materials. It can be cast to fit any structural shape from a cylindrical water storage tank to a rectangular beam, slabs and column in a high-rise building. In RC buildings, portions of columns that are common to beams at their intersections are called beam column joints. Beam-column joints have a crucial role in the structural integrity of the buildings. Review of literature indicates that numerous studies were conducted in the past to study the behaviour of beam-column joints with normal concrete. However, those recommendations are not intended for the fibre reinforced concrete. Some indicates that this material is an alternative to the confining reinforcement in the joint region. So the comparative study of the performance of different fibres in beam column joint has a greater importance and relevance in the field of RCC framed structures. This thesis aims to study the behaviour of beam column joint by evaluating the performance of fibre reinforced concrete. The incorporation of fibres in beam column joint is analysed in this study. The use of different types of fibres such as steel and polypropylene are evaluated.

EFFECT OF USING HIGHLY CONFINED SHORT LAP-SPLICE REINFORCEMENT ON SEISMIC PERFORMANCE OF EXTERIOR BEAM-COLUMN JOINT

The present paper aims to examine the behavior of exterior beam-column joints with different reinforcement details of their columns: continuous and lap splice longitudinal bars were adopted as design parameter. The experimental program was carried out at the Concrete Research Laboratory at Housing and Building Research Center in Egypt; included three exterior reinforced beam column joints that were tested under the effect of quasi-static cyclic loading. One sample was designed according to the provisions of the current seismic design codes and served as a control sample. Columns of the other two samples were detailed with well confined shorter lap spliced longitudinal reinforcement. The overall behavior of the beam-column joints and conclusions are discussed in this paper.

Experimental and Simulation Study on Seismic Behavior of Beam-Column Joints with Cast Steel Stiffener

AbstractA series of six full-scale cruciform H-shaped beam to square tube column joint with cast steel stiffener specimens was tested under cyclic loading to study the seismic behavior of the new joints. A parametric numerical analysis based on the test results was also conducted. The hysteretic curves of specimens not filled with concrete were full, and the ones of specimens filled with concrete were pinched. The maximum moment resistance of the joints filled with concrete in the column increased from 10 to 30% compared with that of the joints not filled with concrete. The energy dissipation coefficient of the joints not filled with concrete in the column varied from 2.681 to 3.585, whereas it changed from 1.892 to 1.711 for the joints filled with concrete when the width of the square tube column ranged from 300 to 500 mm. The results demonstrate that the joints with cast steel stiffeners have excellent moment capacity, deformation performance, and energy dissipation coefficients. The new joints could po...

Computational methodology to determine the strength of reinforced concrete joint

Seismic performance of structures depends on the force flow mechanism inside the structure. Discontinuity regions, like beam-column joints, are often affected during earthquake event due to the complex and discontinuous load paths. The evaluation of shear strength and identification of failure mode of the joint region are helpful to (i) define the strength hierarchy of the beam-column sub-assemblage, (ii) quantify the influence of different parameters on the behaviour of beam-column joint and, (iii) develop suitable and adequate strengthening scheme for the joints, if required, to obtain the desired strength hierarchy. In view of this, it is very important to estimate the joint shear strength and identify the failure modes of the joint region as it is the most critical part in any beam-column sub-assemblage. One of the most effective models is softened strut and tie model which was developed by incorporating force equilibrium, strain compatibility and constitutive laws of cracked reinforced concrete. In this study, softened strut and tie model, which incorporates force equilibrium equations, compatibility conditions and material constitutive relation of the cracked concrete, are used to simulate the shear strength behaviour and to identify failure mechanisms of the beam-column joints. The observations of the present study will be helpful to arrive at the design strategy of the joints to ensure the desired failure mechanism and strength hierarchy to achieve sustainability of structural systems under seismic loading.

Effect of loading velocity on the seismic behavior of RC joints

The strain rate of reinforced concrete (RC) structures stimulated by earthquake action has been generally recognized as in the range from 10-4/s to 10-1/s. Because both concrete and steel reinforcement are rate-sensitive materials, the RC beam-column joints are bound to behave differently under different strain rates. This paper describes an investigation of seismic behavior of RC beam-column joints which are subjected to large cyclic displacements on the beam ends with three loading velocities, i.e., 0.4 mm/s, 4 mm/s and 40 mm/s respectively. The levels of strain rate on the joint core region are correspondingly estimated to be 10-5/s, 10-4/s, and 10-2/s. It is aimed to better understand the effect of strain rates on seismic behavior of beam-column joints, such as the carrying capacity and failure modes as well as the energy dissipation. From the experiments, it is observed that with the increase of loading velocity or strain rate, damage in the joint core region decreases but damage in the plastic hinge regions of adjacent beams increases. The energy absorbed in the hysteresis loops under higher loading velocity is larger than that under quasi-static loading. It is also found that the yielding load of the joint is almost independent of the loading velocity, and there is a marginal increase of the ultimate carrying capacity when the loading velocity is increased for the ranges studied in this work. However, under higher loading velocity the residual carrying capacity after peak load drops more rapidly. Additionally, the axial compression ratio has little effect on the shear carrying capacity of the beam-column joints, but with the increase of loading velocity, the crack width of concrete in the joint zone becomes narrower. The shear carrying capacity of the joint at higher loading velocity is higher than that calculated with the quasi-static method proposed by the design code. When the dynamic strengths of materials, i.e., concrete and reinforcement, are directly substituted into the design model of current code, it tends to be insufficiently safe.

Seismic Tests on RC Building Exterior Joints with Wide Beams

Reliable assessment procedures of existing RC buildings are currently available, and have been introduced in the Italian and European codes reporting new rules for seismic analysis. However, further studies are required in order to further improve such procedures and, specifically, obtain more accurate data on the behavior of beam-column joints, whose role on the global behavior of framed RC buildings can be crucial. Until now studies on this issue have been mainly devoted to joint specimens with stiff beams, however frame structures having wide (also called flexible or flat) beams are widely used in the European residential building stock. To this purpose, given the lack of knowledge, an experimental investigation on full scale beam-column joints with wide beam has been planned and is currently in progress. In the present paper the main results of three tests are reported and discussed. The role of different earthquake resistant design levels on joint performances is pointed out.

STATIC BEHAVIOUR OF DIFFERENT TYPES OF R.C BEAM-COLUMN CONNECTIONS AS AFFECTED BY BOTH VALUE ACTING LATERAL HORIZONTAL FORCEAND GRADE OF USED CONCRETE (THEORETICAL STUDY) Part Two

This paper describes a theoretical study of forty eight (48) Reinforced Concrete RC beam column joints, which generally classified as interior, exterior and corner joints. The most main parameters, which may influence the behavior of beam-column joint, transverse reinforcement, lateral shear reinforcement, longitudinal reinforcement, joint area, column axial load, concrete compressive strength, end boundary conditions …etc. In this research FEA (finite element analysis) using ABAQUSCAE commercial software will be developed to build a detailed model to predict the nonlinear behavior of beam-column joint under seismic loadings. The ABAQUSCAE 6.7 solution is a practical way to implement the nonlinear dynamic earthquake analysis for the finite element model. Our study is focusing with joints where statically lateral load was applied and gradually increased maintaining constant axial load at the top of the column equal to 0.15 (AcFc). Several linear variable horizontal displacement transducers were mounted , the net story drift, bond stress, axial shear stresses and strains as well as energy absorption for using different grades of concrete C250, C400, C600 and C1200 are evaluated and discussed to illustrate the behaviour of the studied joints under the case study of loadings.

A Study of R. C. C. Beam Column Junction Subjected To QuasiStatic (Monotonic) loading

Beam and column where intersects is called as joint or junction. The different types of joints are classified as corner joint, exterior joint, interior joint etc. on beam column joint applying quasi-static loading on cantilever end of the beam. and study of various parameters as to be find out on corner and exterior beam column joint i.e. maximum stress, minimum stress, displacement and variation in stiffness of beam column joint can be analyzed in Ansys software ( Non-Linear FEM Software) Significant experimental research has been conducted over the past three decades on hysteretic behavior of beam-column joints of RC frames under cyclic displacement loading. The various research studies focused on corner and exterior beam column joints and their behavior, support conditions of beam-column joints. Some recent experimental studies, however, addressed beam-column joints of substandard RC frames with weak columns, poor anchorage of longitudinal beam bars and insufficient transverse reinforcement. the behavior of exterior beam column joint is different interior beam-column joints by Nonlinear finite element analysis using ATENA a software for nonlinear analysis of reinforced concrete structures. The model has been calibrated using the results of the third authors tests. The behavior of exterior and interior beam-column turned out to be different .The parameters influencing the shear strength are not the same for both types of connections. Different parameters like effect of the material properties, effect of geometry of connection, effect of reinforcement, effect of concrete compressive strength and joint slenderness. The parameters influencing the shear capacity are different for exterior and interior connections. The FE results were compared with the authors experimental results and the good agreement between the two was achieved. Kuang J.S. and Wong H. F. (2 ) Reversed cyclic-load tests are carried out on full-scale reinforced concrete (RC) exterior beam-column joints, which are fabricated to simulate those in as-built RC framed buildings designed to BS 8110. Emphasis of the study is placed on the effects of the types of beam bar anchorage and location of laps in column reinforcement on the seismic behavior and shear strength of RC exterior joints subjected to simulated earthquake load. Shear strength of a beam-column joint predicted by the criterion of initial diagonal cracking is highly dependent on the level of axial loads applied on the column; this model gives very good correlations with all the test data in this study

보-기둥 접합부 비탄성 전단거동을 고려한 5층 철근콘크리트 보통모멘트골조의 푸쉬오버해석

In this study, the effects of the inelastic shear behavior of beam-column joint and the vertical distribution of lateral load are evaluated considering higher modes on the response of RC OMRF using the pushover analysis. A structure used for the analysis was a 5-story structure located at site class SB and seismic design category C, which was designed in accordance with KBC2009. Bending moment-curvature relationship for beam and column was identified using fiber model. Also, bending momentrotation relationship for beam-column joint was calculated using simple and unified joint shear behavior model and moment equilibrium relationship for the joint. The results of pushover analysis showed that, although the rigid beam-column joint overestimated the stiffness and strength of the structure, the inelastic shear behavior of beam-column joint could be neglected in the process of structural design since the average response modification factor satisfied the criteria of KBC2009 for RC OMRF independent to inelastic behavior of joint.

Cyclic Tests on External RC Beam-Column Joints: Role of Seismic Design Level and Axial Load Value on the Ultimate Capacity

A wide experimental program on beam-column RC joints carried out in the framework of the DPC-Reluis Project (DPC: Department of Civil Protection, Reluis: Network of University Laboratories of Earthquake Engineering) is presented. All the experimental tests were performed at the Laboratory of Structures of the University of Basilicata, Potenza, Italy. The main objective of the experimental campaign is to study and compare the post-elastic behavior of beam-column joints with different earthquake-resistant design levels, indicating the role of some structural parameters such as the axial load value acting on the column, beam dimensions, and steel type, on the joint performances and failure mechanism. The analyses have mainly been devoted to improving the assessment procedures regarding existing buildings but also to verifying the prediction capability of the capacity models relevant to beam-column joints contained in literature and in the new seismic codes. Following a short description of the experimental methodologies used in other campaigns, the experimental program is presented, providing a detailed description of the specimens and of the testing set-up. This is followed by a report of the main results of the cyclic tests performed on the beam-column specimens that highlight the role played by axial load and seismic design level in determining the failure mechanism and the global response of the joints.

Seismic behavior of interior RC beam-column joints with additional bars under cyclic loading

The behavior of beam-column joints in moment resisting frame structures is susceptible to damage caused by seismic effects due to poor performance of the joints. A good number of researches were carried out to understand the complex mechanism of RC joints considered in current seismic design codes. The traditional construction detailing of transverse reinforcement has resulted in serious joint failures during earthquakes. This paper introduces a new design philosophy involving the use of additional diagonal bars within the joint particularly suitable for low to medium seismic effects in earthquake zones. In this study, ten full-scale interior beam-column specimens were constructed with various additional reinforcement details and configurations. The results of the experiment showed that adding additional bars is a promising approach in reinforced concrete structures where earthquakes are eminent. In terms of overall cracking observation during the test, the specimens with additional bars (diagonal and straight) compared with the ones without them showed fewer cracks in the column. Furthermore, concrete confinement is certainly an important design measure as recommended by most international codes.

Seismic Behavior of Beam-Column Joints Reinforced with GFRP Bars and Stirrups

Reinforced concrete beam-column joints are commonly used in structures such as parking garages and road overpasses, which might be exposed to extreme weathering conditions and the application of deicing salts. The use of the noncorrodible fiber-reinforced polymer (FRP) reinforcing bars in such structures is beneficial to overcome the steel-corrosion problems. However, FRP materials exhibit linear-elastic stress-strain characteristics up to failure, which raises concerns on their performance in beam-column joints in which energy dissipation, through plastic behavior, is required. The objective of this research project is to assess the seismic behavior of concrete beam-column joints reinforced with glass (G) FRP bars and stirrups. Five full-scale exterior T-shaped beam-column joint prototypes were constructed and tested under simulated seismic load conditions. The longitudinal and transversal reinforcement types and ratios are the main investigated parameters in this study. The experimental results showed that the GFRP-reinforced joints can successfully sustain a 4.0% drift ratio without any significant residual deformation. This indicates the feasibility of using GFRP bars and stirrups as reinforcement in the beam-column joints subjected to seismic-type loading. It was also concluded that, increasing the beam reinforcement ratio, while satisfying the strong column-weak beam concept, can enhance the ability of the joint to dissipate seismic energy.

Experimental Investigation on the Seismic Behavior of Beam-Column Joints Reinforced with Superelastic Shape Memory Alloys

Superelastic Shape Memory Alloys (SE SMAs) are unique alloys that have the ability to undergo large deformations and return to their undeformed shape by removal of stresses. This study aims at assessing the seismic behavior of beam-column joints reinforced with SE SMAs. Two large-scale beam-column joints were tested under reversed cyclic loading. While the first joint was reinforced with regular steel rebars, SE SMA rebars were used in the second one. Both joints were selected from a Reinforced Concrete (RC) building located in the high seismic region of western Canada and designed and detailed according to current Canadian standards. The behavior of the two specimens under reversed cyclic loading, including their drifts, rotations, and ability to dissipate energy, were compared. The results showed that the SMA-reinforced beam-column joint specimen was able to recover most of its post-yield deformation. Thus, it would require a minimum amount of repair even after a strong earthquake.

Modeling Beam-Column Joints in Fragility Assessment of Gravity Load Designed Reinforced Concrete Frames

Reinforced concrete (RC) frame structures customarily have been designed in regions of low-to-moderate seismicity with little or no consideration of their seismic resistance. The move toward performance-based seismic engineering requires accurate reliability-based structural analysis models of gravity load designed (GLD) RC frames for predicting their behavior under seismic effects and for developing seismic fragilities that can be used as a basis for risk-informed decision-making. This analytical approach requires particular attention to the modeling of beam-column joints, where GLD frames differ significantly from their counterparts in high-seismic areas. This article focuses on modeling shear and bond-slip behavior of beam-column joints for purposes of seismic fragility analysis of GLD RC frames. The joint panel constitutive parameters are defined to replicate the experimental joint shear stress-strain relationships, while the effect of bond-slip is taken into account through a reduced envelope for the joint shear stress-strain relationship. The joint model is validated using two full-scale experimental RC beam-column joint test series. A fragility assessment of an existing three-story GLD RC frame reveals the importance of modeling shear, anchorage, and bond-slip in joints of GLD frames accurately when performing seismic risk assessments of buildings.

The effects of stirrups and the extents of regions used SFRC in exterior beam-column joints

Seven full-scale exterior beam-column joints were produced and tested under reversible cyclic loads to determine. Two of these seven specimens were produced using ordinary reinforced concrete (RC). Steel Fiber Reinforced Concrete (SFRC) was placed in three different regions of the beams of the rest five specimens to determine the extent of the region where SFRC is the most effective. The extent of the region of SFRC was kept constant at the columns of all five specimens. Three of these five specimens which had one stirrup in the joint, were tested to evaluate the effect of the stirrup on the behavior of the beam-column joint together with SFRC. In production of the specimens with SFRC, all special requirements of the Turkish Earthquake Code related to the spacing of hoops were disregarded. Previous researches reported in the literature indicate that the fiber type, the volume content, and the aspect ratio of steel fibers affect the behavior of beam-column joints produced with SFRC. The results of the present investigation show that the behavior of exterior beam-column joints depends on the extent of the region where SFRC is used and the usage of stirrup in the joint, in addition to the parameters listed in the literature.

Seismic design of beam-column joints in RC moment resisting frames - Review of codes

The behaviour of reinforced concrete moment resisting frame structures in recent earthquakes all over the world has highlighted the consequences of poor performance of beam column joints. Large amount of research carried out to understand the complex mechanisms and safe behaviour of beam column joints has gone into code recommendations. This paper presents critical review of recommendations of well established codes regarding design and detailing aspects of beam column joints. The codes of practice considered are ACI 318M-02, NZS 3101: Part 1:1995 and the Eurocode 8 of EN 1998-1:2003. All three codes aim to satisfy the bond and shear requirements within the joint. It is observed that ACI 318M-02 requires smaller column depth as compared to the other two codes based on the anchorage conditions. NZS 3101:1995 and EN 1998-1:2003 consider the shear stress level to obtain the required stirrup reinforcement whereas ACI 318M-02 provides stirrup reinforcement to retain the axial load capacity of column by confinement. Significant factors influencing the design of beam-column joints are identified and the effect of their variations on design parameters is compared. The variation in the requirements of shear reinforcement is substantial among the three codes.

Improvement of the earthquake resistance of R/C beam-column joints under the influence of P-△ effect and axial force variations using inclined bars

In this study, theoretical and experimental results are presented which were obtained during an investigation of the influence of the <TEX>$P-{\Delta}$</TEX> effect that was caused by the simultaneous changing of the axial load P of the column and the lateral displacement <TEX>${\Delta}$</TEX> in the external beam-column joints. The increase or decrease of <TEX>${\Delta}$</TEX> was simultaneous with the increase or decrease of the axial compression load P and caused an additional influence on the aseismic mechanical properties of the joint. A total of 12 reinforced concrete exterior beam-column subassemblies were examined. A new model, which predicts the beam-column joint ultimate shear strength, was used in order to predict the seismic behaviour of beam-column joints subjected to earthquake-type loading plus variable axial load and <TEX>$P-{\Delta}$</TEX> effect. Test data and analytical research demonstrated that axial load changes and <TEX>$P-{\Delta}$</TEX> effect during an earthquake cause significant deterioration in the earthquake-resistance of these structural elements. It was demonstrated that inclined bars in the joint region were effective for reducing the unfavourable impact of the <TEX>$P-{\Delta}$</TEX> effect and axial load changes in these structural elements.

RC 기둥과 RS 보로 이루어진 보-기둥 접합부의 비탄성 거동

RC 기둥과 RS 보로 이루어진 보-기둥 접합부의 비탄성 거동