Beam Column Research Articles

Comparison Between EBR Method and a NSM New Technique for Strengthening Concrete Beam–Column Joints

Comparison Between EBR Method and a NSM New Technique for Strengthening Concrete Beam–Column Joints

Comparison of emulation evaluation methods of precast concrete moment resistance structures

Despite widely acknowledged advantages of the precast concrete (PC) structures, limited cases exist in which PC structures have been used to construct middle-to-high-rise structures. To construct PC structures, technologies for various tasks (e.g., transfer mechanisms, assembly, lifting, structural integrity) are required. In particular, the emulation related to the seismic design should be clearly evaluated, that is, whether PC structures have structural performance and serviceability equivalent to monolithic structures. Currently two methods are used to evaluate the emulation of the PC structures: relative and absolute methods. Both methods have advantages and disadvantages. The results of the two methods are not always consistent. Emulation results differed depending on the material and structural characteristics. In this study, ten PC beam–column joint specimens were tested, and their structural performance was evaluated using both the relative and absolute methods of emulation evaluation. Furthermore, the most suitable method was selected by analyzing the test results of 160 reinforced concrete beam–column joint specimens. Experimental and analytical results showed that it was desirable to evaluate the emulation of PC frames on relative evaluation criteria. The method under absolute conditions was too strict for special moment resistance frames. The absolute emulation evaluation criteria should reflect the type of frames, and the material and sectional characteristics of specimens because the strength reduction ratio, energy dissipation ratio, and stiffness of the specimen vary depending on the cross-sectional and material characteristics.

Behavior of new hybrid connection between steel beam and concrete-encased composite column

A new bending connection between a steel beam and concrete-encased composite column (CECS) with a bolted flange plate is proposed which maintains the integrity of the column and allows for the interchangeability of the beam for improvement of the connection. The confinement of the steel plates and the central steel core (H-section column) is provided by reinforced concrete and cover plates, thus lateral torsional and local buckling of the through plate (TP) and the central core is prevented. Three full-scale samples of the proposed exterior connection with variable TP thickness and different bending capacities under lateral cyclic and constant axial loads in the column were tested. The moment contribution in the components and seismic behavior of the connection were studied. The load transfer to the panel zone occurred through four components in the bending plane; TP, concrete performance, tensile studs, and side plates. The average share of the resistant elements which is immediately behind the front plate were determined as 56%, 26%, 12.50%, and 5.5%, respectively. The internal panel zone remained undamaged and the stresses were below the yield limit, so that the plastic hinge could occur outside the connecting members in the beam. In general, the specimens with sufficient pre-tensioning in the connection bolts had stable hysteresis curves and less pinching. In addition, these specimens showed acceptable energy dissipation that provided a high ductility index.

Behaviour of Stainless-Steel Fibre-Reinforced Exterior Beam-Column Joints under Reverse Cyclic Loading

The objective of this study is to evaluate the flexural behaviour of stainless-steel fibre-reinforced concrete beam-column (BC) joints under reverse cyclic loading. Based on the properties of concrete with various percentages of fibre, the optimized volume fraction was obtained as 0.75% of stainless-steel fibre. In the present work, two sets of beam-column joints with and without fibres were cast and tested under reverse cyclic loading. The beam-column joints were loaded up to five cycles, to study their behaviour, and examine the failure pattern of the joint. Based on test results, parameters such as ductility and the energy absorption capacity characteristics were evaluated. It is concluded that the inclusion of stainless-steel fibre improves the overall seismic resistance of RC beam-column joints.

Stability analysis of stiffness reduction models on rotary- and non-rotary straightened W-shapes

This paper presents a parametric study of stiffness reduction models on rotary- and non-rotary straightened hot-rolled steel W-shapes to examine if the models for non-rotary straightened sections are appropriate for stability analysis of rotary-straightened members. Four stiffness reduction models were investigated, which include (1) a conventional model adopted by AISC 360, which is known as the CRC model, (2) a model fitting the column strength curves provided in Eurocode 3, and models fitting cross-section distributed plasticity curves incorporating (3) the ECCS residual stress pattern and (4) a residual stress pattern of rotary-straightened sections. Beam finite element models were created and second-order inelastic analyses were conducted. A range of different cross-section geometries typically used for beam–columns was investigated, which includes various aspect ratios and flange-to-web area ratios. Columns and beam–columns were investigated with uniaxial bending about the major and minor axes with several axial utilization ratios. The effects of the stiffness reduction models on the stability limit state are discussed. The results of the parametric study are presented along with comparisons of the stiffness reduction values for hot-rolled steel members, which provide further understanding of the stiffness reduction model’s influence on the stability analysis of rotary straightened hot-rolled steel members.

Experimental investigation of the seismic resistance of RC beam–column connections after freeze–thaw cycle treatment

The freeze–thaw cycle (FTC) is one of the major factors leading to damage to reinforced concrete (RC) structures in severely cold regions. The seismic resistance of FTC-damaged RC beam–column connections is critical to the assessment of structural safety. However, studies on the seismic resistance of FTC-damaged RC beam–column connections under severely cold environments are still scarce. In this study, the seismic resistance of FTC-damaged RC connections was investigated in terms of the failure process, hysteresis, energy consumption, core area shear behavior, etc. Furthermore, the effects of FTC action at the microscopic level and macroscopic level and the damage mechanisms of the connections were investigated. The results showed that the shear force ratio of the connections varied via the “diagonal compression strut model” and “truss model” propagation due to the FTC-induced deterioration of the bond performance between the longitudinal rebar and concrete in the beam end; this variation in the shear force ratio, in turn, led to the transformation of the failure mode of the connections. Moreover, as the number of FTCs increased, the ductility of the connections increased slightly, and the shear distortion in the core region as well as its contribution to the whole displacement gradually rose. When the shear–compression ratio is >0.208, increasing the axial force ratio will reduce the load carrying capacity and the shear distortion in the core zone. Based on the test results, a calculation model of the shear force–strain envelope curve of RC connections that integrates the effects of the inhomogeneous temperature field distribution and axial compression ratio was established.

Geopolymer Haunch Beam‒Column Connection Behavior

Geopolymer Haunch Beam‒Column Connection Behavior

Pullout Tests on Concrete Breakout Strength of Headed Reinforcement Bars Embedded in Roof Exterior Beam-Column Joints

Recently, the use of headed bars as mechanical anchorage in reinforced concrete beam-column joints has increased rapidly. This type of anchorage is used for T-shaped beam and exterior column joints at middle floors and for L- and T-shaped beam-column joints at the rooftops of buildings. However, few experimental data are available regarding the anchorage capacity of headed bars embedded in L-shaped beam-column joints. Nine pullout tests are conducted to investigate the anchorage capacity of headed bars embedded in L-shaped beam-column joints. Parameters affecting the anchorage capacity, such as the diameter, embedment length, location of the headed bars, and the number of supplementary bars are considered. The anchorage capacity of the headed bars is evaluated using empirical formulas proposed by Kubota and Murakami and a formula for concrete cone failure. The failure behavior of the specimens is concrete failure with cracks propagating in the diagonal direction at the maximum applied load. The anchorage capacity increases with the embedment length and diameter of the headed bars, number of supplementary bars, and concrete area. For most specimens, the Kubota and Murakami formulas overestimate the anchorage capacity, whereas formula for concrete cone failure yields lower anchorage capacities as compared with the test results.

Haunch retrofit of RC beam–column joints: Linear stress field analysis and Strut‐and‐Tie method application

AbstractThis paper addresses the stress field of reinforced concrete (RC) beam–column joints retrofitted with haunches. Design of such solution currently assumes internal forces evaluated by the so called β‐factor approach, which was originally conceived targeting the enhancement of steel moment‐resisting frames. Extension to RC is subsequent as it emerges from the literature survey. The analytical model is first critically rediscussed. Inconsistencies of the adopted structural scheme, with respect to the actual mechanical behavior, may lie on the compatibility conditions which are imposed between the haunch and concrete beam (or column). In this regard, two‐dimensional finite element models (FEM), using linear‐elastic materials, are employed to study the stress field of two benchmark specimens derived from literature. A partial validation is carried out against experimentally derived internal forces. Results show that, for haunches with extended flat plates and stiff diagonals, compressive diffusion affects the entire haunch region. Consequently, beam's kinematic hypothesis of linear strains is no longer valid. The predicted joint shear demand resulted underestimated by β‐factor approach by 50%. Since 2D FEM may be not efficient for many practical circumstances, an application of Strut‐and‐Tie is alternatively proposed. Finally, both the limitations and possible extensions of the proposed approaches are stated transparently.

Autonomous 3D vision‐based bolt loosening assessment using micro aerial vehicles

AbstractEarlier identification of bolt loosening is crucial to maintain structural integrity and prevent system‐level collapse. In this study, a novel drone‐based 3D vision methodology has been proposed for autonomous bolt loosening assessment. First, a low‐cost micro aerial vehicle with various types of sensors is designed. Second, a drone‐based autonomous image collection method is proposed. Third, a 3D point cloud of the bolted connection is generated using the acquired images. Fourth, 3D point cloud processing methods are proposed to localize and quantify bolt loosening. The proposed method has been implemented on structural beam–column connections. The results show that the proposed drone‐based data collection method can effectively acquire images for 3D reconstruction. The 3D point cloud processing methods can reliably localize and quantify bolt loosening at high accuracy. The proposed method provides a more robust and comprehensive evaluation of bolt loosening, compared to existing 2D vision methods, which process 2D images captured at a specific camera view.

Re-planning of Concrete Structures in the Ngoro Dormitory Project in Surabaya

The current trend of building construction is using steel frames and reinforced concrete frames. The construction design concept is based on strength limit analysis (ultimate strength) which has sufficient ductility to absorb earthquake energy according to applicable regulations. In addition to this, it is also necessary to consider the economic aspect. All of these structural considerations will influence planning alternatives, such as column layout, beam length, and span. Dormitori Ngoro Surabaya is one of the low-rise buildings that will be redesigned to comply with SNI 2847:2013. This research is expected to answer the need for earthquake-resistant building construction using the ETABS program and according to SNI 2847:2013 standards. In this study the method used with the concept of Flowcharts in order to facilitate the research stage. As for this study, it produced a maximum moment of 137.58 KNm with the use of beam dimensions of 40 x 75 cm, using 8D16 top main reinforcement and 3D16 bottom main reinforcement with stirrups D10-200 in the support area and D10-100 in the field area. Whereas the ratio of beam reinforcement based on manual calculations is 0.24% and the ETABS results are 0.22%.

A general scaled model design method of stiffened plate subjected to combined longitudinal compression and lateral pressure considering the ultimate strength and collapse modes

A general and efficient scaled method for stiffened plates subjected to combined longitudinal compression and lateral pressure is proposed based on slenderness, simply by adjusting the number of stiffeners. The design method makes it easier to determine the dimensions of the scaled model for a given scale ratio compared with the previously proposed method. The emphasis is on the influence of the plate slenderness, the column slenderness, and the non-dimensional parameter of the lateral pressure on the ultimate strength. By maintaining the consistency of the plate slenderness and column slenderness, the proposed method is applicable for designing scaled models with materials of different yield stresses and Young's moduli. A similar effect of the lateral pressure on the ultimate strength of the prototype and scaled models is achieved by maintaining the non-dimensional parameter. In addition, the applicability of the scaled method to the initial deflection is considered, which provides a reference for similar models. The similitude of the scaled method is verified for several typical buckling modes, including the beam–column, tripping, web and overall collapse modes. Given the numerical results, the proposed general and fast scaled method can provide reasonable dimensions of scaled stiffened plates subjected to combined loads.

Damage Analysis of Reinforced Concrete Columns Based on Fiber Beam–Column Element

The method of damage analysis of reinforced concrete columns based on the fiber element model is established by combining the uniaxial damage constitutive model of concrete and steel with the fiber beam–column element model. The quasi-static test and the shaking table test of reinforced concrete columns are simulated and analyzed, respectively. The results show that the established fiber element model can predict nonlinear mechanical behavior and the damage distribution of reinforced concrete columns with good accuracy. Furthermore, the model can effectively simulate the evolution process of damage of columns, and describe weak parts of columns, and has high computational efficiency and solution accuracy, thus providing a practical analysis method for the simulation of building structures during earthquake.

Shear capacity estimation of core steel tube reinforced PCCC column-beam interior joint under quasi-static load

In this study, the quasi-static tests were conducted on 13 core steel tube (CST) reinforced PVC-CFRP confined concrete (PCCC) column-beam interior joints. Distinct shear failure occurred in all joint specimens. The load-displacement hysteresis curves appeared pinching phenomenon, and the shape of hysteresis loops gradually deformed from shuttle to arch and finally changed to reverse S shape. The overall shape of hysteresis curves were relatively full, demonstrating that the joints had favorable seismic performances and energy dissipation capacity. The strain development law of materials in the joint area in the process of stress was clarified. The increment of joint stirrup ratio ([Formula: see text]), axial compression ratio ([Formula: see text]), column reinforcement ratio ([Formula: see text]) or beam reinforcement ratio ([Formula: see text]) improved the calculated shear capacity of the joints. The calculated shear capacity increased first and then decreased slightly as the diameter-thickness ratio of CST ([Formula: see text]) increased. In comparison, spacing of CFRP strip had little impact on the calculated shear capacity. Additionally, the concrete strength enhancement coefficient ([Formula: see text]) and joint stirrup utilization coefficient ([Formula: see text]) were introduced respectively to modify the shear capacity of concrete and joint stirrups, and a simplified formula for predicting the shear capacity of CST reinforced PCCC column-beam interior joints under quasi-static load was proposed. The predicted results agreed well with the test data.

Testing, FE modelling and design of pin-ended stainless steel equal-leg angle section columns and beam–columns

The behaviour and design of pin-ended stainless steel equal-leg angle section members under compression and compression plus minor-axis bending are investigated herein. The studied members are cylindrically pinned about the minor axis. An experimental investigation, including material testing, initial geometric imperfection measurements and physical tests on hot-rolled stainless steel equal-leg angle section members is first presented. Numerical models are developed and validated against the new experimental data. A numerical parametric study is then presented considering both hot-rolled and cold-formed stainless steel angle section columns alongside beam–columns with a wide range of slenderness values. Finally, new design proposals for pin-ended stainless steel equal-leg angle section members under compression and combined compression and minor-axis bending are developed and verified against the results of existing physical experiments, as well as the newly-generated test and numerical results. The proposed design rules are shown to offer substantially more accurate and consistent resistance predictions compared to existing codified design rules. The reliability of the new design provisions, with a recommended partial safety factor γM1=1.1, is verified following the EN 1990 procedure.

Cyclic Loading Test for Beam–Column Joints of Precast Concrete Beam and Concrete-Encased Steel Angle Column

Cyclic Loading Test for Beam–Column Joints of Precast Concrete Beam and Concrete-Encased Steel Angle Column

Strengthening of RC Beam-Column Joints Using Steel Plates and Shear Connectors

Abstract: The role of a beam‐column joint is very vital in RCC framed structures. Most of the structural collapses due to earthquakes have been initiated by the failure of the beam‐column joints and therefore understanding the behavior of beam‐column joints is important. The beam column joint is a crucial area where loads from the beam and columns are transferred. It becomes the most critical part of the structure when poor detailing ,unsafe design adopted in the region ,overuse or lack of maintenence.

Development and seismic performance evaluation of New high strength reinforced concrete column and steel beam (New-RCS) joint

Reinforced Concrete column and Steel beam (RCS) structural systems have recently become popular in Taiwan for office buildings. High seismic demand makes the size of conventional concrete columns enormous and the reinforcement over-crowded, which can be solved using high-strength materials. However, due to the lacuna of research regarding the usage of high-strength materials, existing design guidelines for the RCS systems have restricted the maximum grade of steel reinforcement to 410 MPa. Also, using high-strength materials in RCS joints necessitates innovative joint detailing and design to develop sufficient joint bearing and shear strength. Thus, a new high-strength reinforced concrete column and steel beam (New-RCS) joint was developed in this study, incorporating the use of Grade 690 MPa steel as reinforcement along with Grade 84 MPa concrete. A combination of wide flange bearing plate and flange doubler plate joint detailing was developed to improve the bearing and shear capacity of the joint. Also, a design methodology based on moment–curvature analysis was proposed to include the contribution of locked longitudinal reinforcement to bearing resistance. Subsequently, two large-scale interior beam-column subassemblies were subjected to quasi-static cyclic loading to verify the seismic behaviour of the proposed joint. One specimen was designed explicitly considering the material hardening and overstrength of steel beams. While the other was designed following the Taiwanese practice, which does not explicitly consider material hardening and overstrength but implicitly does it through strength reduction factors. Both the specimens exhibited a drift capacity of 4% with a stable and ductile hysteretic response and eventually failed through beam plastic hinging.

Assessment of the beam configuration effects on designed beam–column connection structures using FE methodology based on experimental benchmarking

Abstract Purpose This article aims to investigate the structural behavior of beam–column joints subjected to axial force. The geometry used is the addition of a number of beam connections to the column, and the differences in the numbers of beams used are 1, 2, 4, and 4, denoted as V1, V2, V3, and V4, respectively. Design/methodology/approach In this work, the analysis was performed using the numerical finite element method with ABAQUS software. A benchmarking analysis was also conducted to validate the numerical results. Findings Several numerical simulations showed that of the variations tested, the V2 model demonstrated the highest force value among the four test models, at 130.883 kN. The displacement caused by the force was 227.32 mm, which was the lowest value among the four test models. On the other hand, the V3 model received the smallest force value among the four test models, at 24.576 kN, with a displacement of 227.49 mm. The displacement value was greater than that for the V2 model, further indicating that the V2 model was the stiffest of the four models tested. Originality/value This study shows that the influence of beam–column joint geometry is not limited to double-extended end-plate bolted connections.

Performance-based design method for bolted stiffened end-plate connection under monotonic loading

Bolted stiffened end-plate connection is one of the solutions for steel beam to column connections in moment resisting frames implemented after the Northridge and Kobe earthquake incidents. The connection comprises a steel end-plate shop welded to the beam and field bolted to the column flange. In addition, the end-plate extensions are stiffened using angular stiffener plates. Out of the prevailing design codes and guidelines, Eurocode 3-1-8 [1] has provided specifications to design bolted end-plate connections using the equivalent T-stub method, but it does not incorporate the effect of end-plate stiffeners in the design of the connection, whereas AISC [2] design guidelines provide specifications to design the particular connection components. However, these design methods do not address the performance enhancement of the bolted stiffened connection.For these reasons, this study investigates a performance-based design method through numerical analyses to improve the performance of the bolted stiffened end-plate connection. This method is primarily based on the strong column and weak beam concept. Here, primary and secondary yield mechanisms are organized in a hierarchy so that the connection failure occurs in a predefined way by identifying the yield mechanisms and failure modes of the connection. Through this, the targeted performance characteristics of the connection identified as ductility and energy dissipation capacity can be improved. Thus, this performance-based design method is a better approach than the conventional load resisting design method proposed by the code of practice.