Beam-hinge Mechanism Research Articles

Influence of the Vertical Load Bearing Status on the Seismic Performance of Weak-Joint-Type RC Frames Strengthened by the Wing Wall Installation Method

“Strong column–weak beam, strong joint–weak member” is a core concept for the seismic design of buildings. For existing reinforced concrete (RC) frame buildings that do not satisfy this concept, installing RC wing walls beside existing columns is a simple and effective method for strengthening both columns and joints to promote a beam-hinging mechanism. In this study, a numerical simulation method is used to analyze the seismic performance of weak-joint RC frames strengthened by additional wing walls considering the column axial force ratio and to determine whether to consider the secondary load as a variable. The results show that when the secondary load is not considered, i.e. existing columns do not bear a load during the strengthening process, the strength, stiffness and energy dissipation of the structure increase with increasing axial force ratio, but the ductility of the structure decreases. When the secondary load is considered, the strength and initial stiffness of the frame are the greatest when the column axial force ratio is 0.4. When the axial force ratio is less than 0.4, the secondary load has less influence on the strength, stiffness and energy consumption. When the axial force ratio is greater than 0.4, the secondary load has a significant impact on the seismic performance of the strengthened structure, and the strength, stiffness, energy consumption and ductility are significantly greater than those in the case in which the secondary load is not considered. Additionally, the larger the axial force ratio is, the more significant the difference is. It is revealed that in engineering seismic strengthening using the wing wall installation method, the influence of secondary load on seismic performance should not be ignored, especially when the axial force ratio is large.

Experimental and numerical study on seismic performance of assembled platform canopy with mortise-tenon joints

To investigate the seismic performance of a Y-shaped single-column platform canopy assembled using mortise-tenon joints, a 1:4 scaled specimen with two roof panels was fabricated using a real assembly process. The seismic performances, including the failure mode, hysteretic behavior, bearing capacity, ductility, and energy dissipation capacity, were measured by a low cyclic loading test, and the main influencing parameters, such as the longitudinal reinforcement ratio, linear stiffness ratio of the laminated beam to the precast column, and canopy slab height, were analyzed using validated finite element models. The test results showed that the hysteretic curve presented a pinch effect, indicating shear slip characteristics. The ultimate drift angle was 1/17, and the displacement ductility coefficient was greater than 4.5, indicating that the structure has good deformation capacity and ductility. Plastic hinges appeared at the ends of the laminated beam and base of the prefabricated columns, and the failure mode was the beam-hinge mechanism. The results of the finite element analysis were in good agreement with the test results. Parameter analysis indicated that when the longitudinal reinforcement ratio increased, the seismic performance, including the initial stiffness, ultimate bearing capacity, and ductility, increased. As the linear stiffness ratio of the laminated beam to the precast column and the height of the canopy slab increased, the initial stiffness and ultimate bearing capacity improved significantly, whereas the ductility decreased.

Optimal Seismic Design Method Based on Genetic Algorithms to Induce a Beam-Hinge Mechanism in Reinforced Concrete Moment Frames

Optimal Seismic Design Method Based on Genetic Algorithms to Induce a Beam-Hinge Mechanism in Reinforced Concrete Moment Frames

Equal-displacement principle-based direct seismic-design method for single-yielding precast-concrete frame

This study aims to improve the seismic performance and reduce damage of a structure using energy-dissipation connectors, while avoiding the design difficulties of existing methods. In this study, a single-yielding–precast-concrete (SYPC) frame was proposed to realize the design of a controllable bending moment at the beam end. An equal-displacement principle-based direct seismic-design method was proposed for the SYPC frame. First, using a dynamic time–history analysis, the key parameters affecting the stiffness of the frame and the adjustment strategy were explored. Subsequently, based on the equal-displacement principle, the seismic intensity control and target interstory drift were directly determined. Finally, a direct seismic-design method for the SYPC frame based on the equal-displacement principle was proposed. A six-story SYPC frame was designed according to the proposed design method. An elastic–plastic dynamic time–history analysis was performed for the designed frame to verify the effectiveness and accuracy of the proposed design method. The results show that the equal-displacement principle can rapidly and accurately determine the target elastic–plastic displacement of the underground motions of the structure and effectively avoid the iterative solution of structural plastic characteristic parameters, such as equivalent damping and ductility coefficient, encountered in traditional design methods. The proposed design method not only effectively controls the deformation pattern of the structure but also realizes an ideal beam-hinge mechanism. Additionally, by controlling the length and section area of the replaceable energy-dissipating connectors (REDCS) to satisfy the ductility requirement, the stiffness was verified to satisfy the requirements of the frame deformation mechanism.

Experimental study on PSPC beam – Concrete encased CFST column frame installed with novel steel panel dampers

A concrete-filled steel tubular (CFST) column has a bearing capacity with a relatively small cross section. From the perspective of the assembly, a partially steel-reinforced precast concrete (PSPC) beam can combine the merits of both the reinforced concrete beam and steel beam. However, strong earthquake action puts forwards a dramatic seismic requirement for the high-rise frame. In this study, to improve the seismic performance of the structure in an economical way, the duplex assembled I-shaped steel panel damper (DAISPD) was introduced to the PSPC beam-concrete encased CFST column frame through the eccentric brace. A half-scaled two-storey two-bay substructure specimen was tested under cyclic loading. A series of seismic properties was then analysed, including the failure modes, hysteretic performance, and energy dissipation capacity. To further investigate the contribution of the damper, groups of numerical analyses were conducted on the key design parameters of the DAISPD. The introduction of the damper provides an adequate lateral stiffness and energy absorption to the frame, especially when the interstorey drift is within the elastic and plastic drift limits. The damage of the damper and the beam hinge mechanism occurs sequentially, which results in a two-stage failure mode. Considering the predamage contribution and the postdamage influence of the damper, it is recommended to design with a moderate yield force and a small height.

Experimental study on seismic behaviors of prefabricated embedded concrete-filled steel tube special-shaped column exterior frame

The new type of prefabricated embedded concrete-filled steel tube (CFST) special-shaped column structure delivers green and environmentally-friendly strengths and high space. In this study, a full-scale frame test piece with one frame façade, two stories and two spans are designed and fabricated for purposes of exploring the seismic performance and node connection safety of filled built-in steel tube concrete-filled special-shaped column, and low cyclic load testing is implemented. The bearing characteristics, deformation capacity, energy-dissipating capacity, ductility and stiffness degradation of the test piece are analyzed. The results showed that the failure mechanism is typical beam hinge mechanism. The fabricated beam-column and column-column connection nodes in this paper are safe and reliable. The hysteretic curve of fabricated embedded CFST special-shaped column is full, the ductility and energy dissipation capacity of fabricated embedded CFST special-shaped column are better than such indexes of ordinary reinforced concrete special-shaped column. The inter-story displacement angle is 1/32 when the test piece is damaged, being significantly higher than the limit value of elastic-plastic inter-story displacement angle of 1/50 under strong earthquake. The precast embedded steel-reinforced concrete special-shaped column structure is only required to be connected with steel ribs to significantly improve the construction speed and quality, delivering great economy.

Seismic performance of prefabricated middle frame composed of special-shaped columns with built-in lattice concrete-filled circular steel pipes

Prefabricated buildings are green and environment-friendly, with high construction efficiency. Concrete-filled steel pipe structures have high bearing capacity and strong deformation ability. Special-shaped column frame structures of prefabricated concrete-filled circular steel pipe with built-in lattice can give full play to the advantages of prefabricated buildings and concrete-filled steel pipe structures, with the advantage of high space utilization rate of special-shaped column structures. In order to study Seismic performance of frame in special-shaped columns of prefabricated concrete-filled circular steel pipe with built-in lattice, a full-scale middle frame model specimen with two floors and two spans was designed, and the failure mechanism of the specimen was obtained by low-cycle loading test. The hysteretic performance, deformation capacity, energy dissipation capacity and stiffness degradation of the specimen were analyzed. The results showed that the failure mechanism of the prefabricated concrete-filled steel tubular special-shaped column is a typical beam hinge mechanism, which meets the design requirements of “strong column and weak beam”. The special-shaped columns frame of built-in concrete-filled circular steel pipe has full hysteretic curve, good ductility and energy dissipation capacity, and stable stiffness degradation. When the specimen is damaged, the inter-story drift angle reaches 1/23, which is much higher than the limit requirement of elastic–plastic inter-story drift angle of 1/50 under strong earthquake. The existence of built-in concrete-filled steel pipe changes the bearing mechanism of the structure. After the external concrete falls off, the internal force of the structure redistributes, forming a stress system of built-in concrete-filled steel pipe truss. The post-cast joint between overlapping precast column and superposed beam and grouting connection joint between precast column and column sleeve are not damaged, and the fabricated joints are safe and reliable.

Seismic Performance Experiment Involving One-Story, Two-Bay Self-control Energy Dissipation UPPC Frames under Low Cyclic Loads

This paper presents an experimental study of the behavior of three one-story, two-bay unbonded partially prestressed concrete (UPPC) frames, of which two frames are self-control energy dissipation UPPC frames. This study aims to use the self-control energy dissipation UPPC frame as a new frame, and its seismic performance is evaluated compared to that of existing UPPC frames. The new frame utilizes energy dissipation components to provide energy dissipation capabilities, which allow the frame to form a beam-hinge mechanism under earthquake actions. The influence of the prestress release percentage on the seismic performance of the UPPC frame is experimentally examined. The test results show that the new UPPC frame displays better ductility and energy dissipation capabilities as the prestress release percentage increases, but the lateral resistance is slightly weaker than that of a common UPPC frame. Overall, the new frame displays better seismic performance than the conventional UPPC frame and can be reused after retrofitting.

Experimental Seismic Performance of Self-Control Energy Dissipation UPPC Frame

A self-control energy dissipation unbonded partially prestressed concrete (UPPC) frame refers to the rational setting of self-control energy dissipation components in the UPPC frame, which aims at reducing the stress of unbonded prestressed reinforcement during severe earthquakes. Besides, part of the prestress in the beam during that period can be released to form a beam-hinge energy dissipation mechanism and strong column-weak beam ductility frame. In this paper, the experimental study of two frames (UPPC frame and self-control energy dissipation UPPC frame) under low cyclic loading demonstrates that the self-control energy dissipation UPPC frame of this experiment presents a better energy dissipation capacity and thus can form a beam-hinge mechanism.

Experimental Study on Novel Energy‐Dissipating Prefabricated Beam‐Column Joints

A new dapped‐end beam to column connection is designed in this paper. Its assembly connection zone changes from inside the joint to midspan of the beam. The proposed connection can not only provide good structural integrity but also ensure that the plastic hinge moves away from the column edge. The rotational capacity of the plastic hinge determines the internal force redistribution of the joint and the energy dissipation capacity. The high‐strength bolts and steel plates are used to realize connection, further enhancing the rotation of the plastic hinge and minimizing the cast‐in‐place concrete volume. Three full‐scale exterior beam to column joints are casted and then subjected to reversal cyclic loading. The finite element (FE) analyses are carried out to compare with experimental results and study the effect of connection position on the structural behaviours. The obtained results show that the plastic hinges of all three specimens are firstly developed to a distance from the column edge, thus revealing that this kind of joint can achieve beam hinge mechanism and prevent joint shear failure. And the connection position is the most disadvantaged when coinciding with the plastic hinge zone, which would result in the excessive deformation and the early failure of the steel bar anchor system. The new type of joint shows good seismic performance during earthquake if the connection can be properly designed, and thus this kind of structural form can be applied to actual engineering structures in seismic regions.

Experimental Seismic Performance of Self-Adapting Energy Dissipation UPPC Frame

Our research team put forward a self-adapting energy dissipation unbonded partially prestressed concrete (UPPC) frame structural system, which is a new UPPC frame structure with good deformability and energy dissipation capacity. This new structure refers to the rational setting of self-adapting energy dissipation components in the UPPC frame, which aims at reducing the stress of unbonded prestressed reinforcement during severe earthquakes. Besides, part of the prestress in the beam during that period can be released to form a beam-hinge energy dissipation mechanism and strong column-weak beam ductility frame. In this paper, the experimental study of two frames (UPPC frame and self-adapting energy dissipation UPPC frame) under low cyclic loading demonstrates that the self-adapting energy dissipation UPPC frame of this experiment presents a better energy dissipation capacity, and thus can form a beam-hinge mechanism.

Required Column Overdesign Factor of 3D Steel Moment Frames with Square Tube Columns

Steel moment frames are designed to ensure sufficient energy absorption capacity by achieving an entire beam-hinging collapse mechanism against severe earthquakes. Therefore, the column overdesign factor is stipulated in seismic design codes in some countries. For example in Japanese seismic design code, the specified column overdesign factor is 1.5 or more for steel moment frames with square tube columns. And this paper describes seismic response by 3D analysis of steel moment frames, and presents seismic demand for the column overdesign factor to keep the damage of square tube columns below the specified limit of plastic deformation. The major parameters are column overdesign factor, horizontal load bearing capacity, shape of frames and input direction of ground motion. In order to investigate 3D behavior of frames and correlation between plastic deformation of columns and column over design factor, apparent column overdesign factor, which is defined as the ratio of full plastic moment of the column (s) to the full plastic moment of the beam (s) projected in the input direction of the ground motion, is introduced. From the earthquake response analysis, it is clarified that the profile of maximum value of cumulative plastic deformation of columns to apparent column overdesign factor, with the similar horizontal load bearing capacity, are nearly identical regardless of number of stories, floor plan, and input direction of ground motion. As a result, the required column overdesign factor to keep the damage of columns below the limit of plastic deformation is proposed under the reliability index of 2.

Experimental and Numerical Investigation of Concrete‐Filled Double‐Skin Steel Tubular Column for Steel Beam Joints

This paper presents a new type of joint for connecting steel beams with a concrete‐filled double‐skin steel tubular (CFDST) column. Four half‐scale specimens of the joint with different specifications were constructed and tested under a constant axially compressive force with vertical low‐reversal loads applied to the beam ends to examine their failure modes and hysteretic behaviors. The beam hinging mechanism of the joint was observed in the radian area of the horizontal end plates. The proposed connection was found to exhibit good energy dissipation capabilities with its limit rotation in the failure state reaching 0.05 rad, thus satisfying the FEMA‐350 ductility requirement of ≥0.03 rad for seismic resistance. A finite element analysis (FEA) model of the joint was also established and validated by comparing its predictions with experimental results. The FEA model was used to investigate the effects of different parameters such as the stiffened height of the web anchorage plate, axial load level, steel and concrete strengths, steel ratio on the moment‐rotation relationship, and initial stiffness of the connection. This paper presents some important design considerations of the connection, as well as aspects requiring further study.

Seismic performance evaluation of RC frame-shear wall structures using nonlinear analysis methods

To further understand the seismic performance of reinforced concrete (RC) frame-shear wall structures, a 1/8 model structure is scaled from a main factory structure with seven stories and seven bays. The model with four-stories and two-bays was pseudo-dynamically tested under six earthquake actions whose peak ground accelerations (PGA) vary from 50[Formula: see text]gal to 400[Formula: see text]gal. The damage process and failure patterns were investigated. Furthermore, nonlinear dynamic analysis (NDA) and capacity spectrum method (CSM) were adopted to evaluate the seismic behavior of the model structure. The top displacement curve, story drift curve and distribution of hinges were obtained and discussed. It is shown that the model structure had the characteristics of beam-hinge failure mechanism. The two methods can be used to evaluate the seismic behavior of RC frame-shear wall structures well. What’s more, the NDA can be somewhat replaced by CSM for the seismic performance evaluation of RC structures.

Seismic behavior of lightweight aggregate concrete frame

A one-fifth scale, two-story, two-bay reinforced lightweight aggregate concrete (LWAC) frame subjected to quasi-static cyclical loading was analyzed to investigate the seismic behavior of this innovative system, primarily focusing on the failure modes, plastic hinge mechanism, load-deformation response, skeleton curves, stiffness degradation and energy dissipation capability. Overall, the test demonstrates that the LWAC frame meets the requirement of a “strong-column and weak-beam, strong-joint and weak-member” design criteria, exhibiting a mixed failure mechanisms consisting of both the beam hinge mechanism and column hinge mechanism. The former was the predominant failure mechanism and was fully developed after reaching the peak load point, while the latter was the inevitable result in the final failure of the LWAC frame. The fatter hysteretic loop and the displacement ductility factor Δu/Δy of 3.49 observed from LWAC frame indicate excellent energy dissipation and reliable displacement ductility capability, which are comparable to those of NWC frames. The test data observed in this study can provide theoretical guidance for the application of LWAC frames in seismic regions.

Study of Beam-Column Junction based on Variations in Concrete Grade at Junction

Objectives: A beam-column joint has to transfer the shear forces, bending moments and other related structural response parameters efficiently. The present paper aims at studying the behavior of beam-column junction based on variations in concrete grade at junction. Analysis: To increase the load carrying capacity of a joint, a higher grade of concrete is used at a joint and also up to 1.5D in the direction of beam from face of column, to shift or relocate the plastic hinge from the interface towards the beam. The different specimens were prepared in a T-shaped mould by changing the grade of concrete at beam-column joint and these samples were tested after 7 and 28 days. Findings: Study reveals that use of M20 or M25 grade of concrete at joint and up to 1.5D (D is the depth of beam) of length of beam (M15 grade of concrete in rest of mould) increases the load carrying capacity approximately to about 20% when compared with M20 or M25 grade of concrete at junction and M15 grade in the remaining mould. The most important finding is that the use of higher grade of concrete at a joint and up to 1.5D of length of beam, shifts the failure away from the beam-column interface Thus, a beam hinging mechanism is achieved which is a ductile type of failure compared to beam-column brittle interface failure and there is approximately 15-30% increase in load carrying capacity, in comparison with higher concrete grade only at a joint core. This is a simple and efficient method of preventing the beam-column joint failure. Improvement/Applications: Based on the test results there is remarkable increase in the load carrying capacity of beam-column joint which enhances the rigidity of beam column joint in terms of strength and stiffness.

Genetic Algorithm Based Optimal Seismic Design Method for Inducing the Beam-Hinge Mechanism of Steel Moment Frames

Genetic Algorithm Based Optimal Seismic Design Method for Inducing the Beam-Hinge Mechanism of Steel Moment Frames

Numerical study on seismic behaviours of ConXL biaxial moment connection

The ConXL connection is a standardized and cost-efficient biaxial moment frame connection. It could provide higher construction efficiency if the filled concrete in a steel box column could be eliminated. To determine the seismic behaviours of this connection economically, this study developed a complex nonlinear finite element model (FEM) using the ABAQUS software. After verifying the FEM, four different representative FEMs of joint configurations without concrete filling in the column, including a 2D interior, a 3D interior, a 3D exterior, and a 3D corner joint, were established and loaded with unidirectional and bidirectional cyclic loads. The hysteresis behaviour under different axial load levels in the column was analysed. In addition, to compare the seismic performance of different joint forms more intuitively, the vertical load–displacement relationships at beam ends were equivalently expressed as the storey shear force versus the storey drift of one column according to the energy equivalence principle. The results show that various ConXL connection joint configurations without concrete filling in the column show beam hinge mechanism failure mode when the axial load level in the column is not too high (~0.4). However, the failure mode becomes beam–column hinge hybrid failure mechanism or even column hinge mechanism with an increase in the axial load level. The seismic behaviours are acceptable according to AISC 341, and the panel zone does not show yielding, making it suitable for application as a beam–column connection in steel moment frame structures.

Minimum column-to-beam strength ratios for beam–hinge mechanisms based on multi-objective seismic design

The current strong-column weak-beam design criterion presents a single value as the acceptance limit of strength ratios for Special Moment Resisting Frames (SMRFs). However, previous research efforts have shown that the required column–beam flexural strength ratios of joints in SMRFs vary with the factors such as the height of frames. Therefore, in this paper, the multi-objective seismic design method based on nonlinear static analysis is proposed and applied to find optimal column-to-beam strength ratios required for ensuring the beam–hinge mechanism. In this formulation, the optimal method is to minimize the two objective functions of the structural weight as well as the column-to-beam strength ratio while satisfying the constraints. Based on multiple Pareto-optimal solutions with beam–hinge mechanisms, the relationship between the structural weights and optimal strength ratios is provided. Using the well-known two moment resisting example structures, instead of suggesting a specific single value as a limit for the column–beam flexural strength ratio, a common tendency is identified through investigating the relationships between optimal strength ratios and structural weights.

Development of steel beam-to-column connections using SFRCC slabs

A steel beam-to-column connection with steel fiber reinforced cementitious composites (SFRCCs) slab is proposed. In the proposed connection, the SFRCC slab is designed as an exterior diaphragm to transfer the beam flange load to the column face. The headed studs are densely arranged on the beam flange to connect the SFRCC slabs and steel beams. The push-out test results suggest that the application of SFRCC promises larger shear forces transferred through studs arrayed in a small region in the slab. The seismic performance and failure mechanism of the beam-to-column connection with SFRCC slab are examined based on a series of cyclic loading tests. The beam hinging mechanism can be achieved at the end of the SFRCC slab by the arrangement of a sufficient number of studs and rebars in the SFRCC slab. Numerical models are employed to enhance understanding of the behavior of the proposed beam-to-column connection. Parametric numerical study is also conducted to investigate the effect of the number of studs, slab size, and the amount of rebar on the elastic stiffness and strength of the proposed connection. Design considerations are presented in the last section together with the subjects that require further studies.