Modeling Of Beam-column Joints Research Articles

A comparative seismic fragility analysis of a multi and single component beam-column joint models

Reliable quantification of joint flexibility of non-ductile RC frames is critical for seismic vulnerability assessment. The issue of super-element joint models causing numerical divergence in non-l...

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.

Monotonic and cyclic tests on beam-column joints of industrial pallet racks

Pallet racks are characterized by boltless beam-column connections and the extensive use of thin-walled cold-formed steel members. Due to the great number of beam-end connector types and member geometries, a reliable evaluation of their structural behavior, especially under seismic loads, requires a thorough modeling of beam-column joints, whose moment-rotation curves can be reliably assessed only through experimental tests. In this paper, the authors present results of monotonic and cyclic tests on four different types of industrial rack joints. Tested joints differ from one another in the type of beam-connector, which is obtained by folding the beam end or is welded to the beam-end section with different welding layouts. Moreover, joints differ in the number of tabs and the relative thickness of the upright and the beam-end connector. Experimental results from cyclic tests allows for moment-rotation curves of joints to be accurately identified, confirming that they are significantly different from traditional steel framed buildings due to pinching in hysteresis loops. Obtained curves can be used for reliable modeling of joints in seismic analyses of steel pallet racks. As producers of steel rack structures are interested in reducing the total welding length of beam-end connectors for time efficiency and cost saving, the influence of the welding layout of beam-end connectors on the structural response and failure mode of joints has also been investigated. Finally, some joints have also been equipped with additional bolts to evaluate their influence on the bearing capacity, initial elastic stiffness and dissipated energy per cycle.

Modeling of interior beam-column joints for nonlinear analysis of reinforced concrete frames

Beam-column connections undergo significant shear deformations and greatly contribute to story drifts during earthquake loading, yet their response is typically neglected in traditional frame analyses through the use of rigid end offsets. Although local joint models are available in the literature for the investigation of single, isolated joints, there is a lack of holistic frame analysis procedures simulating the joint behavior in addition to important global failure modes such as beam shear, column shear, column compression, and soft story failures. The objective of this study is to capture the impact of local joint deformations on the global frame response in a holistic analysis by implementing a joint model into a previously-developed global frame analysis procedure. The implemented joint element simulates the joint shear deformations and bar-slip effects. Concrete confinement effects are also considered so that both older and modern joints can be modeled. The developed procedure successfully captures the local load-deflection response of joints within a global frame analysis procedure. The ratio of predicted and observed peak load had a mean of 1.25 before the modification, and a mean of 1.05 after the modification.

Performance Evaluation of Exterior Beam–Column Joint with Core Reinforcement Technique Subjected to Reverse Cyclic Loading

The present work aims to study the performance of exterior beam–column joint with core reinforcement technique subjected to reverse cyclic loading. In this experimental study, three sets of one-third scaled exterior beam–column joint specimens using M30 grade concrete were cast and tested. The first set of specimens were detailed as ordinary moment resisting frame (IS:456 and SP:34) and designated as joint BCJ1. The second sets of specimens were detailed as special moment resisting frame (IS:13920) and designated as joint BCJ2. In the third set, the reinforcement detailing followed in joint BCJ1 was integrated with a new type of reinforcement (called “core reinforcement”) proposed in this study and designated as joint BCJ3. Based on the experimental result, the joint BCJ3 gave the better performance considering the strength in terms of load-carrying capacity, energy dissipation capacity, stiffness and ductility factor. The results of reverse cyclic loading tests performed in the exterior beam–column joint models indicate that the additional core reinforcement in the beam–column joint region provide adequate ductility. The stiffness of the joint with additional core reinforcement in the beam–column joint region did not undergo much reduction when compared to other types of joints. In addition, the usage of core reinforcement in the joint region can reduce its installation and difficulties in placing and compacting the concrete. This combination of core reinforcement technique in the beam–column joint region may contribute to reduction in destruction due to earthquakes.

Component-based reinforced concrete beam-column joint model

A reinforced concrete (RC) beam–column (RCBC) joint model for the quasi-static monotonic analysis of cast in situ RC frames is developed and implemented in a finite element analysis program for framed structures. The joint model was developed in the framework of the component method, a method originally developed for steel joints, which consists of three steps: (a) identification of the joint relevant basic components, their interaction, and contribution to overall joint behavior; (b) characterization of the mechanical behavior of each component; and (c) assembling of the components. With regard to the model implementation, the material nonlinear analysis is performed by the fictitious forces method—all the required steps are presented and explained—while the P–Δ method for the geometrical nonlinear analysis of frames is extended to include the beam–column joint model. The paper closes with illustrative and validation examples; while some of these are fully analytical, the others simulate lab-tested subframes subjected to quasi-static monotonic loads.

Nonlinear seismic analysis of a super 13-element reinforced concrete beam-column joint model

Several two-dimensional analytical beam column joint models with varying complexities have been proposed in quantifying joint flexibility during seismic vulnerability assessment of non-ductile reinforced concrete (RC) frames. Notable models are the single component rotational spring element and the super element joint model that can effectively capture the governing inelastic mechanisms under severe ground motions. Even though both models have been extensively calibrated and verified using quasi-static test of joint sub-assemblages, a comparative study of the inelastic seismic responses under nonlinear time history analysis (NTHA) of RC frames has not been thoroughly evaluated. This study employs three hypothetical case study RC frames subjected to increasing ground motion intensities to study their inherent variations. Results indicate that the super element joint model overestimates the transient drift ratio at the first story and becomes highly un-conservative by under-predicting the drift ratios at the roof level when compared to the single-component model and the conventional rigid joint assumption. In addition, between these story levels, a decline in the drift ratios is observed as the story level increased. However, from this limited study, there is no consistent evidence to suggest that care should be taken in selecting either a single or multi component joint model for seismic risk assessment of buildings when a global demand measure such as maximum inter-storey drift is employed in the seismic assessment framework.

Beam-Column Joint Model for Nonlinear Analysis of Non-Seismically Detailed Reinforced Concrete Frame

An efficient and simplified plane beam-column joint model that can describe the strength deterioration, stiffness degradation, and pinching effect was developed for the nonlinear analysis of non-seismically detailed reinforced concrete frames. The proposed beam-column joint model is a super-element consisting of eight spring components and one panel zone component, representing the bond-slip mechanism of the longitudinal reinforcement and the shear deformation mechanism of the joint concrete core region, respectively. In order to represent the dynamic response at the system level, the elastic constitutive law is applied to the eight connector springs, while the Bouc-Wen-Baber-Noori (BWBN) model is adopted to describe the hysteretic behavior of the panel zone component. For the implementation of the finite element analysis, the algorithmically consistent tangent of the BWBN model is derived as a uni-axial constitutive model, while the initial stiffness of the panel zone component is determined by the concrete compression strut assumption. The accuracy and efficiency of the proposed beam-column joint model were calibrated at both the component and structural levels by comparing the simulated results with the experimental data for non-seismically detailed joint sub-assemblages and a reinforced concrete plane frame.

Perbaikan Balok Beton Bertulang dengan Metode Jacketing dengan Bahan Ferosemen Akibat Beban Siklik pada Beban Ultimit

A large number of buildings construction was made of reinforced concrete structure, composed of concrete and steel. The reinforced concrete structure elements could experience damage due to earthquake, from light to heavy failure, such as heavy bending-shear crack near the beam column joint. It is necessary, therefore, to repair the structure adopted good method and workability. The specimens were part of exterior beam-column joint model. Cyclic lateral load was applied to simulate earthquake load. This research used 3 specimens: US-1, the shear damage specimen as the result of first-step loaded test, then are repaired by using 1 layer rectangular galvanized welded wire mesh became R-US.1. US-2, the shear damage specimen as the result of first-step loaded test, then are repaired by using 2 layers rectangular galvanized welded wire mesh became R-US.2. UBB, the bending damage specimen as the result of first-step loaded test, then are repaired by using 2 layers rectangular galvanized welded wire mesh became R-UBB. The result showed that the retrofitted on ultimate load by using jacketing ferrocement increased the ultimate strength capacity of 91,667%(US-1 to R-US.1), 81,818%(US-2 to R.US.2) and 28,571%(UBB to R-UBB) respectively. Increasing the hysteretic energy were 215, 66%(US-1 to R-US.1), 273,11%(US-2 to R.US-2) and 389, 84%(UBB to R-UBB). The ductility of retrofitted specimen 6,64(R-US.1) and 12,72(R-US.2). The initial stiffness of retrofitted specimens decreased 60%(US-1 to R-US.1), 40%(US-2 to R-US.2) and 18%(UBB to R-UBB).

Fragility curves for non-ductile reinforced concrete frames that exhibit different component response mechanisms

Around the world, a large percentage of buildings in regions of high seismicity are older, non-ductile reinforced concrete. To assess the risk posed by these buildings, fragility functions are required to define the likelihood that these buildings will sustain damage and collapse under earthquake loading. This paper presents the initial phase of a research effort to develop fragility functions for non-ductile concrete frames using numerical simulation; the research presented in this paper focuses on development of the numerical model and application of the model to develop fragility functions for a prototype non-ductile concrete frame. To enable numerical simulation of concrete frame buildings, response models for beam–column joints and columns are developed to provide (1) appropriate simulation of component response and, thereby, reliable assessment of risk and (2) computational efficiency and robustness. These new models are developed using existing experimental data, build on response models proposed by others, and employ component and material models available in the OpenSees analysis platform (http://opensees.berkeley.edu). A new beam–column joint model combines a new expression for joint strength and newly developed cyclic response parameters; a new column response model includes a new shear-strength model and newly developed cyclic response parameters. Numerical models of a prototype non-ductile concrete frame are developed that include simulation of one or more of the following characteristics: (1) rigid beam–column joint, (2) nonlinear joint shear response, (3) nonlinear joint shear and bond–slip response, and (4) column shear failure. Dynamic analyses are performed using these frame models and a suite of ground motions; analysis results are used to develop fragility curves. Fragility curves quantify the vulnerability of the frame and provide understanding of the impact of different component failure mechanisms on frame vulnerability.

Finite Element Analysis on the Resistance Capability of a New Precast Concrete Tube Column

A new type of composite structure, precast concrete tube column is proposed, and its axial compression performance and the seismic performance of beam-column joint are studied. Nine groups of precast concrete tube column models and three groups of common solid column contrast models with the same outer diameters (600,800,1000mm) were established by software ABAQUS, and a beam-column joint model for horizontal low cyclic loading was established combining with practical project. The results show that the ultimate bearing capacity of precast concrete tube column is higher than that of the common solid column with the same outer diameter by 5% to 20%, and it increases slightly as the thickness of tube increases. Displacement - load hysteresis curve of the beam-column joint is relatively full under cyclic load, and the slope of skeleton curve decreases slowly, which provides an important basis for engineering applications.

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.

Evaluation, Calibration, and Verification of a Reinforced Concrete Beam–Column Joint Model

A model for use in simulating the response of reinforced concrete interior beam-column joints is developed and evaluated using an extensive experimental data set. This model builds on previous work by Lowes and Altoontash in 2003, modifying the previously proposed model to improve prediction of response and extend the range of applicability. First, a new element formulation is proposed to improve simulation of joint response mechanisms. Second, a new method for simulating the shear stress-strain response of the joint core is developed. This method assumes joint shear is transferred through a confined concrete strut and simulates strength loss due to load history and joint damage following yielding of beam longitudinal steel. Third, modifications are made to enable better simulation of anchorage zone response. Comparison of simulated and observed response histories indicates that the new model represents well stiffness and strength response parameters for joints with a wide range of design parameters.

Investigation on the effects of fiber composites at concrete joints

This investigation involves parametric studies of the application of fiber-reinforced polymer (FRP) composite laminates to exterior beam–column joints to increase their moment capacity. Three beam–column joint models were examined using various fiber composite laminates and wraps, and various thickness. Composite laminates and wraps considered were made out of epoxy and fibers such as E-glass, carbon, and kevlar. One beam–column joint model without FRP reinforcement was used as a control specimen for comparison. The other two beam–column joint models studied included laminates bonded to the tensile faces with and without wraps. The wraps were provided to prevent the peeling of the laminates. The finite element analysis results indicated that the choice of the fiber composite materials, the laminate and wraps arrangement and thickness affected the enhancement of the structural joint performance significantly. Furthermore, an increase in the moment capacity of up to 37% was observed when the joints were reinforced with FRP laminates and were compared to the control specimen.

Modeling bond-slip deformations in reinforced concrete beam-column joints

A new finite element model for reinforced concrete beam-column joints is proposed. The model considers the effects of bond-slip and shear deformations in the joint panel region. The problems associated with modeling bond-slip of anchored reinforcing bars are discussed. The proposed bond-slip model is examined at the element level by comparing its predictions with other analytical and experimental results. The ability of the model to simulate bond deterioration and eventual pullout of anchored reinforcing bars under severe cyclic excitation is demonstrated. This model is incorporated into the global beam-column joint element. Further comparisons are made between the predictions of the proposed beam-column joint model and other analytical and experimental results under reversed cyclic loading to show the validity of the model to describe the bond-slip behavior of the joints.Key words: bond, bond-slip, finite element, beam-column, reinforced concrete, cyclic.

プレキャスト・プレストレストコンクリートはり・柱接合部モデル試験体の静的正負繰返し加力実験報告

本実験では建築構造における主要材料であるはり・柱接合部を取り上げ, その重要な耐震性能である剛性や耐力に対してどのように損傷を受けるのかを実験的に調べることを目的とし, 強度と変形能力を確認した。とくに, 本実験ではプレキャストのプレストレストコンクリート構造の圧着接合の復元力特性を得ることを主目的とした。その結果, 圧着接合は十分に接合効果があり層間部材角で±1/100rad, ±1/50radを与えても十分安全性があり, ±1/25radを与えても破壊することがなかった。さらに, パネルゾーンにひびわれが発生していないことはパネルゾーンの増強工法に適用できるものといえる。