Column Hinges Research Articles

Column-to-beam flexural strength ratio for rigorous strong-column–weak-beam design for steel–concrete composite frames

This study addresses the limited research and unclear principles surrounding the strong-column–weak-beam (S-C–W-B) criterion in steel–concrete composite frames, a critical aspect of structural engineering. Despite its widespread application in steel frames, the S-C–W-B criterion's adaptation to steel-concrete composite frames remains underexplored. The research aims to clarify and establish consistent guidelines for preventing column hinge formation at the joint, a key concern in S-C–W-B design. Beginning by analysing the definitions of ultimate flexural strength and flexural yielding strength of a section, essential components of the S-C–W-B criterion, the minimum column-to-beam flexural strength ratio (ηc, min) required for a robust S-C–W-B design was deduced. The methodology involves a novel parametric analysis using a fibre beam–column model. This model is used to derive a closed-form equation for ηc, min, which was then verified through time-history analysis using the finite-element software MSC.Marc. The findings indicate that the established ηc, min provides a stringent, nonetheless, reliable criterion for S-C–W-B design in steel-concrete composite frames. This research not only bridges a significant gap in existing structural engineering knowledge but also proposes a practical approach for safer and more efficient design in real-world applications.

Elastic-plastic analysis of a novel prefabricated SRC column-steel beam composite frame structure

The objective of this study is to examine the mechanical behavior of a novel PSRCS (Prefabricated SRC Column-Steel Beam) frame structure under static and dynamic loads. To this end, a PSRCS frame structure with PSRCS joints has been constructed using the OpenSees software, and an elastoplastic analysis has been conducted. The principal findings of the study are as follows: Firstly, a comparison of the test results for the PSRCS joints with the FE (finite element) simulation results demonstrated that the FE model based on OpenSees is an effective means of simulating the load-bearing and deformation performance of the PSRCS joints. Subsequently, a PSRCS frame structure was constructed using OpenSees, and static and dynamic elastoplastic analyses were performed. Compared to the more conventional SRC column-steel beam frame structures, the PSRCS frame structure displays superior deformation capacity when subjected to static pushover action. The PSRCS frame structure exhibits a 'beam hinge' failure mode due to the plastic deformation of the flange connection plates, whereas the failure location of the conventional frame tends to be at the column ends, resulting in a 'column hinge' failure mode. In the context of dynamic analysis, an increase in the number of stories results in an augmented hysteresis of the vertex displacement-time history curve at the upper level of the PSRCS framework. The fundamental natural period T1 of the PSRCS frame is approximately 27.6 % to 34.0 % larger than that of the common frame, contributing to the maintenance of structural stability. In conclusion, a series of design objectives and methodologies based on performance were put forth for the PSRCS frame structure.

Experimental study on seismic performance of two-story two-bay. Precast concrete frame with UHPC-based connections

The UHPC-based connections, utilizing Ultra-high performance concrete (UHPC) to connect rebars within precast concrete structures, present the advantages of short splice length, simplified construction, and low cost due to the excellent bond property between UHPC and rebars. This investigation focuses on seismic performance of precast concrete frame (PCF) with UHPC-based connections. The UHPC-based connections were arranged strategically to the beam-column joints and column bases in PCF to connect longitudinal rebars of beams and columns, respectively. Two half-scale, two-story, two-bay reinforced concrete frames, including PCF and a monolithic concrete frame (MCF) for reference, were tested under cycle loading with axial compression ratios of 0.33 in the middle columns and 0.22 in the side columns. The results revealed that PCF exhibited a beam sway mechanism, with all beam hinges developed prior to column hinges, while MCF displayed a mixed sway mechanism, with part of beam hinges developed prior to column hinges. The hysteresis curves of the two frames were globally stable with minimal pinching, and PCF displayed greater energy dissipation compared to MCF. The load-carrying capacity of PCF was 9 % higher than that of MCF. The displacement ductility of PCF was 4.14, exceeding that of MCF by 10 %. The two frames showed similar laws of stiffness degradation. Overall, the precast concrete frame with the UHPC-based connections exhibited better seismic performance in comparison with the monolithic counterpart.

Investigation on Seismic Performance of Reinforced Concrete Frame Retrofitted by Carbon Fiber-Reinforced Polymer

In order to improve the seismic performance of reinforced concrete (RC) frames, carbon fiber-reinforced polymer (CFRP) was used to retrofit reinforced concrete frame structures. The comparison pseudo-static test results show that the peak load, initial stiffness and ductility of the CFRP retrofitted model were increased by 43.89%, 39.27% and 30.1%, respectively. Based on the parametric study of the finite element model, the contribution of CFRP to the seismic upgrading effect of RC columns was quantitatively revealed, and an optimized design of retrofitted CFRP was proposed. The results show that the peak load, ductility and energy dissipation capacity of the whole structure are improved by using CFRP full-wrap reinforcement and strip reinforcement models with different coverage areas. The damage degree of the column decreases, the damage degree of the beam increases, and the failure mode changes from “column hinge” to “beam hinge”. Simultaneously, different CFRP reinforcement areas and the distance between strip CFRP have different reinforcement effects on concrete structures. Based on the investigation results, the recommended ratio of CFRP strip to spacing is 1 to 1.25.

Seismic performance of precast columns strengthened with prestressed CFRP

To address the issue of poor seismic performance in precast columns compared to cast-in-place columns during service, a wedge-type anchor was designed to apply prestress to multi-layer carbon fiber reinforced polymer (CFRP) and strengthen the precast columns. Eight specimens were designed and fabricated to validate the strengthening effect of the proposed method. The seismic performance indicators, including ductility, energy dissipation, and load-bearing capacity of each specimen, were analyzed based on parameters such as the use of strengthening, axial compression ratio, and longitudinal reinforcement diameter (equivalent reinforcement ratio). The results showed that the ductility coefficient and energy dissipation of the strengthened specimens increased by up to 240% and 640% respectively, and the ultimate bearing capacity increased by up to 34.5%. With the increase in axial compression ratio, the ductility coefficient and energy dissipation capacity of the specimens decreased, but the load-bearing capacity increased. Increasing the diameter of the longitudinal reinforcement at an equivalent reinforcement ratio resulted in a decrease in the ductility and energy dissipation capacity of the specimens, but improved their load-bearing capacity and stiffness. This is because there is a stiffness transition in the connection area between the grouting sleeve and the top, and plastic hinges form at the upper part of the sleeve, resulting in a reduction in the effective height of the specimen. However, prestressed CFRP provides sufficient lateral active confinement stress to the specimen, greatly reducing the bond slip between the longitudinal reinforcement and concrete, and improving the stiffness transition in the grouting sleeve area of the precast column, thereby enhancing the seismic performance and overall integrity of the precast column. Finally, a calculation method for the flexural capacity of strengthened specimens considering the constraint effect of CFRP on concrete was proposed, and the effective height of the specimens was calculated based on the upward mechanism of plastic hinges in precast columns. The final calculation results had small errors, indicating that the proposed method has high accuracy and good applicability.

Seismic collapse assessment of archetype frames with ductile concrete beam hinges

Highly ductile cement-based materials have emerged as alternatives to conventional concrete materials to improve the seismic resistance of reinforced concrete (RC) structures. While experimental and numerical research on the behavior of individual components has provided significant knowledge on element-level response, relatively little is known about how ductile cement-based materials influence system-level behavior in seismic applications. This study uses recently developed lumped-plasticity models to simulate the unique failure characteristics and ductility of reinforced ductile-cement-based materials in beam hinges and applies them in the assessment of archetype frame structures. Numerous story heights (four, eight, and twelve), frame configurations (perimeter vs. space), materials (conventional vs. ductile concrete), and replacement mechanisms within the beam hinges are considered in the seismic analysis of the archetype structures. Results and comparisons are made in terms of the probability of collapse at 2% in 50-year ground motion, mean annual frequency of collapse, and adjusted collapse margin ratio (ACMR) across archetype structures. The results show that engineered HPFRCCs in beam plastic-hinge regions can improve the seismic safety of moment frame buildings with higher collapse margin ratios, lower probability of collapse, and the ability to withstand large deformations. Data is also reported on how ductile concrete materials can reduce concrete volume and longitudinal reinforcement tonnage across frame configurations and story heights while maintaining or improving seismic resistance of the structural system. Results demonstrate future research needs to assess life-cycle costs, predict column hinge behavior, and develop code-based design methods for structural systems using highly ductile concrete materials.

A Multidimensional Elastic–Plastic Calculation Model of the Frame Structure with Magnetorheological Damper

To analyze the multidimensional elastic–plastic response of the frame structure with magnetorheological (MR) dampers under strong seismic excitations, the test of the MRD was performed, the location matrix of the MRD in the frame structure was derived, and the multidimensional elastic–plastic calculation models of the frame structure with and without an MRD were established based on the three-segment variable stiffness beam. Taking a five-story reinforced concrete (RC) frame structure as an example, the multidimensional elastic–plastic calculation models were developed by MATLAB software and the dynamic time history analyses were performed under strong seismic excitations. The results show that under the seismic wave, after the MRD is installed in the structure, the maximum horizontal displacements of the top-story node of the structure in X and Y directions is reduced by 51.87% and 39.59%, respectively, and the maximum horizontal accelerations are reduced by 36.67% and 47.86%. The maximum displacements and the story drift ratios of each story of the structure are significantly reduced, and the reduction in the maximum accelerations of each story is small relatively. In the frame structure without an MRD, plastic hinges appear at the ends of most columns, and the structure is characterized by a column hinge yield mechanism. The maximum residual displacement angles of the column end in X and Y directions which reach 1.628 × 10−3 rad and 2.101 × 10−3 rad, respectively. After setting the MRD, the number of plastic hinges in X and Y directions at the column end are both reduced by 37.5%, and the residual displacement angle at some column ends are reduced to 0. The results show that the complied calculation model programs of the frame structure can effectively simulate the multi-dimensional seismic response of the structure with and without MRD.

Research on Dynamic Characteristics of Canopy and Column of Hydraulic Support under Impact Load

In the process of coal mining, the canopy and column play an important role in the safety support of hydraulic support. However, due to the complex and changeable coal seam conditions, the hydraulic support is significantly affected by the impact load. This paper aims to reveal the dynamic characteristics of canopy and column under impact load. Firstly, the dynamic model of hydraulic support is established, and the impact response of each hinge point of the canopy is analyzed. Secondly, based on the fluid–structure interaction (FSI) theory, the two-way FSI model of the column is established, and the structural change of the column and the flow field characteristics in the cylinder under the impact load are analyzed. The results show that the front column hinge is more prone to impact failure under impact load. The impact load has a significant impact on the two-level cylinder, the pressure in the cylinder increases, and an eddy current occurs on both sides of the bottom of the cylinder. The research results can provide references for the structural optimization of the hydraulic support with anti-impact load and the strength design of the column.

Evaluation of strong column-weak beam criterion in spliced columns of steel moment frames

In the seismic design of steel special moment frames, it is necessary to ensure that columns are generally stronger than beams. This reduces the probability of a weak story failure mechanism of the frame and ensures the formation of beams' plastic hinges earlier than the columns'. This criterion is known as strong column-weak beam (SCWB) in seismic design codes and is checked by a formula in the form of a ratio of total flexural strengths of columns to beams framing at each joint. It is common practice to ignore the column section change at the splice location and to use the flexural strength of the larger column section in evaluating this ratio. In this paper, several steel special moment frames were optimally designed by the genetic algorithm, using constraints on the SCWB ratios and controlling the amount of sectional change in the columns of a certain story. Then, the specified story's behavior and the sequence of plastic hinge formations in the beams and columns were examined using nonlinear time history analyses. The results indicate that satisfying the SCWB ratio with the larger column section results in the earlier formation of plastic hinges in columns and using the smaller column section's flexural strength prevents this phenomenon. Moreover, a significant column section change adversely affects the nonlinear behavior of the frame. It is recommended to limit the amount of column section change at splices and to use the properties of the smaller column section in the SCWB formula.

Consistent Software-Specific Nonlinear Dynamic Response of Highway Bridges

Compared to linear analysis approaches, nonlinear analysis of bridge models under large seismic demands has enabled more realistic prediction of global and local responses. However, the sensitivity to modeling assumptions, element and material formulations, software-dependent implementations, and parameter selection may lead to variable results between nonlinear analysis software packages. While previous work has led to a better understanding of how to model nonlinear static response of bridge components and systems, seismic loads and the corresponding material hysteresis introduce additional sources of variability in the nonlinear response. Two ordinary standard bridges in California were analyzed using simplified steel and concrete constitutive models in concentrated plasticity elements for the columns and nonlinear gap-link springs for the abutments. The models were implemented in SAP2000 and OpenSees and calibrated to achieve common material, section, and element-level nonlinear static responses. Subsequently, the models were extended to seismic excitation with common unloading-reloading rules for the material models as well as common definitions for damping and mass. Analysis results showed consistent drift, base shear, and moment-curvature response histories between the software packages. However, the nonlinear seismic response sensitivity for alternative column hinge formulations and abutment models should be investigated in future studies.

Seismic fragility estimates of steel diagrid structure with performance-based tests for high-rise buildings

During seismic performance-based design for building structures, the accuracy of limit states criteria is directly related to its real damage state and retrofitting measures after the earthquake. As a new type of structures, diagrid structure has a special way of bearing force. Firstly, in order to accurately estimate the deformation capacity and energy dissipation mechanism under horizontal loads, four plane specimens of steel diagrid structure are designed and seismic performance-based tests under horizontal quasi-static cyclic load are carried out. Secondly, according to the yield strength and horizontal ultimate deformation capacity of diagrid structure, combined with pushover method, the limit state values of four performance levels of diagrid structure are determined. Finally, the seismic fragility of a diagrid structure for high-rise building is analyzed. The results suggest that the bottom tilted columns have obvious deformation visible to the naked eye before failure, and some failure warnings can be given in advance. It is difficult to realize the “beam hinge” mechanism in diagrid structure, and the cumulative damage of “column hinge” is its main failure mode. The bottom tilted column is the first place where plastic hinge occurs. In addition, the recommended value of inter-story drift ratio for judging the yield of steel diagrid structure is 1/128 by these experimental results, and the recommended value of inter-story drift ratio for collapse resistance is 1/85. Based on these experimental results, the probability of diagrid structure in each performance state can be estimated reasonably and effectively.

Optimization of an RC frame structure based on a plastic analysis and direct search of a section database

For the optimum design of RC frame structures, a simplified but effective discrete optimization algorithm is introduced in this paper. To determine the member force to be based on the design procedure, a plastic analysis considering the sequential development of plastic hinges in beams and columns up to the point of collapse is conducted, with the subsequent optimum design then devised via a direct search method. The construction of a database for predetermined discrete RC sections and interconnections of all design variables in an RC section with a single design variable associated with the section identification number makes it possible to adopt the direct search method instead of a sophisticated mathematical approach that includes many complicated descriptive functions pertaining to RC beams and columns. The use of the plastic analysis also reduces the maximum member force through moment redistribution, and the direct search method makes it possible to find a true optimum section regardless of the assumed initial section. The efficiency and applicability of the introduced algorithm are verified through correlation studies for typical frame structures. In particular, given that all design criteria in design codes and practical limitations required when undertaking the actual design are already considered while determining RC sections in the section database, the obtained results can be directly applied to the creation of designs. In advance, the use of the obtained optimum design results as initial sections in the preliminary design stage will greatly reduce the number of design steps for the determination of RC sections.

Numerical Study on the bending behavior of Reinforced Concrete Beams with kinked rebar

During the past earthquakes, the formation of plastic hinges in columns has given rise to global structural damage in moment resisting frame structures. If the plastic hinges are formed in the beams, the most suitable energy dissipating mechanism in structure will happen. The kinked rebar has locally curved regions (usually near the inflection points in beams) which can be gradually straightened under tension. Due to lower initial yielding flexural capacity compared with that of a cross section reinforced with traditional straight bars, the beam section reinforced with kinked rebars will yield first when the RC frame is subjected to seismic loading, and thus, the strong column-weak beam hierarchy can be realized. In this study, first the load-deflection behavior of a reinforced concrete beam was numerically simulated by ABAQUS software, and the reliability of the finite element model was verified by comparing with the experimental results of other researchers. Then, the load-deflection response of the RC beams with kinked bars which has two-step behavior were investigated and described in steps by using finite element modeling results. Finally, the control beam was used for further analyses to investigate the effect of important parameters including: concrete compressive strength, reinforcement ratio, and the ratio of beam span to depth on load-deflection curve of beams. Results showed that the ultimate bearing capacity of RC beam increases as the reinforcement ratio increases, however, it doesn’t have an important effect on the first yielding point. The increase of concrete compressive strength also contributes to greater initial yielding. In addition, the increase of beam span can have negative effects on the flexural behavior of RC beams with kinked bars, and reduce initial strength and stiffness of beams.Finally, the behavior of an internal connection including a beam with kinked rebar to the column was evaluated.

Strong-column–weak-beam criterion for reinforced concrete frames subjected to biaxial seismic excitation

In several earthquakes, numerous reinforced concrete (RC) frames subjected to seismic excitation exhibit a collapse pattern characterised by column hinges, although these frames are designed according to the strong-column–weak-beam (S-C–W-B) criterion. The effect of biaxial seismic excitation on the disparity between the design and the actual performance of RC frames is investigated in this study. First, a modified load contour method was proposed to derive a closed-form equation of the biaxial bending moment strength, which was verified based on numerical and experimental results. Subsequently, a group of time-history analyses of a simple frame modelled using fibre beam-column elements subjected to biaxial seismic excitation were conducted to verify that the current S-C–W-B criterion is inadequate for preventing the occurrence of column hinges. A biaxial overstrength factor was developed based on the proposed equation, and the reinforcement of columns was appropriately amplified using this factor to prevent the occurrence of column hinges under biaxial excitation; this approach was proved to be effective through another group of time-history analyses. Thus, the findings of this study can serve as a basis for improving the seismic design of RC frames, which will enable the construction of safer engineering structures.

Numerical Study on Cyclic Response of End-Plate Biaxial Moment Connection in Box Columns

The 2008 Wenchuan-China earthquake showed the importance of considering the bidirectional seismic action as a cause of failure in column hinge mechanisms. Subsequently, the large 2011 Tohoku-Japan earthquake revealed that Special Moment Frames buildings, made of tubular columns (Hollow Structural Section or Built-up Box Section) and rigid connections with I-beams, did not suffer serious damage. However, only the ConXtech® ConXL™ moment connection has been prequalified according to the (American Institute of Construction) AISC Seismic Provisions for use with tubular columns and the rest of connections do not consider biaxial resistance. The research reported herein investigated the cyclic response of box-columns joints, connected to I beams using the four-bolt extended endplate connection, subjected to bidirectional bending and axial load on the column. To conduct the study, complex nonlinear finite element models (FEMs) of several I beam to box column joint configurations were constructed and analyzed under cyclic loading using the ANSYS software. The results reveal that the failure is concentrated in the beams of all joint configurations except for the columns with axial load equal to 75% of the column capacity, where a combined failure mechanism is achieved. The energy dissipation capacity of joints with a greater number of beams is lower than joints with fewer beams. The bidirectional effect of the seismic action and the level of axial load must be considered to avoid the formation of a column-hinge fragile failure mechanism also the behavior exhibited by 3D joints is more realistic than 2D joints according to real structures.

The effects of steel X-brace retrofitting of RC frames on the seismic performance of frames and their elements

Steel X braces are used extensively to retrofit RC frames. When steel braces are added to an existing RC frame, the load paths through which the lateral forces are transferred change considerably, resulting in changes in demand on the frame and its elements. The present study attempts to examine the possible side effects of retrofitting RC frames with steel X braces, regarding their overall seismic performance such as global displacements, drifts and base shears, as well as, their individual members, including beams and joints. To this end, a large number of nonlinear time history seismic analyses are performed on retrofitted 2D, RC frames, being 4, 8 and 12 storeys high. It is found that, retrofitting an RC frame with steel X braces improves its global seismic response by reducing the maximum displacement, inter-storey drifts and demand base shear. However, the effectiveness of the bracing system in improving global responses is generally reduced as the height of the frame increases. Regarding the local effects on beams and joints, it is noted that although retrofitting, in general, reduces ductility demand in beams, and shear demand in joints, the reductions are not substantial in taller frames and in some beams and joints retrofitting may even have an adverse effect. Also, the connections between the steel X brace system and the RC frame cause the plastic hinges in beams and columns to relocate further away from the joint, resulting in a reduction in the effective length and possible increase in the level of plastic shear in these members. The local adverse effects of retrofitting an RC frame by steel X-braces may necessitate prior local strengthening of some members.

Performance Assessment of Steel Moment Connections Retrofitted with Various Reduced Section Patterns

It is of high importance in seismic retrofitting of lateral load-bearing systems to increase the connections performance. The crucial point in the steel frame retrofitting process is to create plastic hinges in these types of frames. The formation of plastic hinges in beams and near columns generates large strains on column flanges as well as welding metal and heated surroundings, which can lead to brittle failure. The connection should be designed in such a way as to allow plastic hinge formation at certain points of the beam. One such method suggested for retrofit connections is to reduce the beam section locally away from the connection zone. There are various patterns available to locally reduce the beam section, such as circular, elliptical, and symmetric/asymmetric. In recent years, different proposals have been presented to design these connections which vary from older instructions. For this study, radiused cuts in the flange and slotted holes in the web of connection beams were selected for retrofitting analysis. Cyclic behavior, energy damping levels, and ductility of these connections were studied and compared before and after the retrofit by using nonlinear dynamic analysis. The results showed that the symmetrical circular hole pattern in the beam flanges demonstrated reliable performance.

Seismic Repair of Circular Reinforced Concrete Bridge Columns by Plastic Hinge Relocation with Grouted Annular Ring

ABSTRACT Modern seismic design practice for bridge structures involves the implementation of capacity design principles which localize plastic hinges in columns, while protecting against other modes of failure. The resulting structures are capable of reliably sustaining far greater deformations than their predecessors; however, despite their initial resilience, the formation of plastic hinges can result in buckling and rupture of longitudinal steel, typically leading to the structure’s demolition and reconstruction. Replacement is deemed necessary since the inelastic strain capacity of reinforcing bars severely diminishes once buckling occurs, rendering the structure vulnerable to collapse in future earthquakes. Recent research demonstrates the feasibility of a repair technique in which the previously damaged region is strengthened such that future inelastic action occurs at a new location, although there are presently a limited number of tests on which to base reliable design recommendations. Results of an experimental program are presented in this paper, in which six extensively damaged columns are repaired using the plastic hinge relocation technique and retested. The proposed repair strategy consists of a grouted annular ring composed of conventional materials (i.e. steel rebar, a steel sleeve, and concrete or grout). The results substantiate plastic hinge relocation as a viable repair option for columns with buckled and fractured longitudinal bars and serve to expand the existing data set considerably. A novel analytical model which accurately predicts the behavior of the repaired column is also presented.

Effect of Common U.S. Ground Motion Selection Methods on the Structural Response of Steel Moment Frame Buildings

This study quantifies the impact of two common ground motion (GM) selection methods, included in U.S. standards, on the seismic performance evaluation of steel special moment frames. The methods investigated are a “traditional” approach, herein referred to as the target maximum considered earthquake (TMCE) method, and a newer approach known as the conditional mean spectrum (CMS) method. The TMCE method selects GMs using the risk-based maximum considered earthquake (MCER) spectrum as the target spectrum, while the CMS method uses the CMS that anchors the MCER at multiple conditioning periods. Three special steel moment frames of 4, 8, and 16 stories are designed in accordance with ASCE/SEI 7-10, and their seismic performance is assessed with the nonlinear dynamic procedure prescribed in ASCE/SEI 41-13 using GMs selected and scaled in accordance with the aforementioned methods. A comparison of statistical parameters for the reduced beam sections and column hinges is conducted using the normalized demand-to-capacity ratio ( DCR), as the output parameter. The buildings are evaluated at the collapse prevention performance level for a far-field site located in Los Angeles, CA. In general, the CMS method results in lower DCRs of the frame components and smaller output parameter dispersion. In addition to the spectral shape, the demands are largely influenced by the spectral accelerations prescribed for each evaluated method. The consideration of collapse realizations is also documented as well as the existing and proposed statistical methods to account for these realizations. The study shows that the GM selection process can cause significant differences in structural response that may lead to different retrofitting decisions.

Seismic Performance of a Corroded Reinforce Concrete Frame Structure Using Pushover Method

SAP2000 software was used to build the finite element model of a six‐storey‐three‐span reinforced concrete (RC) frame structure. The numerical simulation of the seismic performance of the RC frame structure incorporating different levels of rebar corrosion was conducted using pushover analysis method. The degradation characteristics of the seismic performance of the corroded structure under severe earthquake were also analyzed. The results show that the seismic performance of the RC frame decreased significantly due to corrosion of the longitudinal rebars. And the interstory drift ratios increase dramatically with the increasing of the corrosion rate. At the same time, the formation and development of plastic hinges (beam hinges or column hinges) will accelerate, which leads to a more aggravated deformation of the structure under rare earthquake action, resulting in a negative effect to the seismic bearing capacity of the structure.