Hybrid simulation with model updating utilizes the test data to identify the parameters of the experimental substructure and updates the model of the numerical substructure, effectively avoiding the errors induced by the inaccurate parameters of the numerical substructure in traditional hybrid simulation. To ensure the accuracy of parameter identification, the selected constitutive parameters must be observable and highly sensitive. The existing local parameter sensitivity analysis method belongs to qualitative analysis and cannot specifically and quantitatively evaluate the sensitivity of the parameters. Therefore a parameter sensitivity analysis method based on correlation analysis is put forward. This method quantitatively evaluates the parameter sensitivity of constitutive parameters by calculating the correlation coefficient between constitutive parameters and restoring force, and the calculation is simple. The parameter sensitivity analysis of concrete employing the Kent-Scott-Park constitutive model and the composite damper using the trilinear constitutive model is conducted respectively, and the results are compared with those obtained by the local parameter sensitivity analysis method. The results show that the higher sensitivity parameters selected by the two methods for the constitutive parameters of concrete are consistent, while the local parameter sensitivity analysis method is not suitable for the composite damper. The proposed method can determine the parameter sensitivity of the constitutive parameters of the composite damper. A six-story steel frame structure equipped with a composite damper was subjected to a hybrid simulation with model updating numerical simulation using different model update methods. The effects of parameter identification were compared and it was found that the constitutive parameters selected by the proposed method were easier to identify, and the hybrid simulation with model updating numerical simulation had higher accuracy and efficiency, which verified the correctness and effectiveness of the method.

Reinforced concrete (RC) columns are exposed to serious seismic disaster risks due to corrosion damage of the internal rebar during the service period caused by environmental corrosion, causing the seismic performance of RC columns to deteriorate and thus be exposed to severe seismic hazard risks. This paper reviews the existing research on the seismic properties of corroded RC columns from four aspects: test methods, degradation law, failure mode prediction and bearing capacity calculation. The corrosion and loading methods used in seismic tests of corroded RC columns are elaborated. The effects of corrosion degree and main design parameters on the deterioration of seismic performance indexes such as ductility, stiffness and energy dissipation capacity of corroded RC columns are statistically analyzed. Based on the seismic test dataset of 290 corroded RC columns, the accuracy of three parametric delineation methods including shear span ratio, ductility coefficient, and shear demand ratio and the extreme gradient boosting (XGBoost) machine learning algorithm for failure mode recognition of corroded RC columns is compared. The influence of the degree of corroded and main design parameters on the failure modes of corroded RC columns is revealed by shapley additive explanations (SHAP) method. The calculation method of residual flexural and shear strength of corroded RC columns are summarized and the prediction effect are discussed. The results show that there are differences in corrosion shape, corrosion rate and corrosion accuracy under different corrosion methods. The bidirectional quasi-static loading mechanism can reflect the degradation law of seismic performance of corroded RC columns better than unidirectional loading. With the increase of the corrosion rate of the rebar, the ductility, stiffness and energy dissipation capacity of RC columns deteriorate significantly. The machine learning model combined with SHAP method can effectively balance the accuracy and interpretability of the failure mode prediction of corroded RC columns. This kind of data-driven prediction method provides a new way to solve the performance evaluation problem of corroded RC columns. Corrosion of rebar will degrade the flexural and shear capacity of RC columns, and the accuracy of the calculation model for the capacity of corroded RC columns proposed at this stage still requires further improvement so as to provide a reasonable basis for assessment of corroded components.

In this paper, a kind of embedded bolt connector was proposed. The utilization of embedded steel blocks and bolt taper sleeves can reduce the damage to concrete and steel beams under load, and enable the removal and replacement of the composite beam. Eight groups of specimens were designed and manufactured. After the push-out test, the specimens were removed and reassembled. Subsequently, a reloading test was conducted and the demountable ability were analyzed. The influence of bolt diameter, bolt strength, T-shaped steel block and external diameter of the embedded steel block were discussed. The results showed that when the specimen was damaged, the bolt was cut or the concrete was crushed. Eight groups of specimens could be quickly disassembled after loading. The dismantled steel beam and T-shaped steel block could be reused for many times. After loading, the concrete slab in undamaged and slightly damaged state could be reused for more than twice, and the shear performance of the specimen remained basically unchanged. The concrete slab in a damaged condition can be reused once, but its shear resistance will be reduced. The concrete slab in a severely damaged condition is not to be reused. In addition, the embedded bolt connector has good anti-lift performance. With an increase of bolt diameter or strength, the bearing capacity of specimen and the damage of concrete slab increased. With an increase in the outer diameter of the embedded rigid block, the bearing capacity of the specimen remained unchanged, while the damage to the concrete slab decreased. The presence or absence of T-shaped rigid block had little impact on the bearing capacity of the specimen, but could enhance the demountable performance. Finally, the local damage coefficient η of concrete slab was proposed as the control index for demountable performance, and when η is about 0.5, it is in a good demountable state.

To study the mechanical behavior of panel zone of complex joints between concrete filled steel tubular (CFST) column and steel truss beam, this paper generates a three-dimensional model based on experimental results using ABAQUS and validates the validity of the model. Subsequently, several sets of models of “strong member and weak joint” models are designed on the basis of the test specimen through structural measures. The influence of the steel truss beam inclination angle, the axial pressure ratio of CFST column and the width-to-thickness ratio of steel tube is studied. The results indicate that the failure mode of panel zone in CFST column-steel truss complex joint is the failure of panel zone within the range of bottom chord, accompanied by the failure of truss girder end. The influence of steel truss beam inclination angle on mechanical behavior and failure mode of panel zone is small. When the axial compression ratio is large, the shear capacity and ductility coefficient of the panel zone decrease obviously. Therefore, it is suggested that axial compression ratio of CFST column should not exceed 0.3. Width-to-thickness ratio of steel tube is a sensitive parameter, and the shear capacity, initial stiffness, and ductility coefficient of panel zone change significantly with the decrease of width-to-thickness ratio of steel tube.

Earthquake magnitude estimation is one of the important tasks in earthquake early warning. Accurate earthquake magnitude estimation is critical to quick judgment of earthquake influence areas and timely release of earthquake warning information. Existing methods usually extract the characteristic information based on the acceleration time history of a single station to estimate the magnitude, and then obtain the result by the multi-station averaging method. In this paper, an end-to-end magnitude estimation model (GAT_M) is constructed using a multi-input graph attention network algorithm. The time history of multi-station seismic acceleration within 3 s after the first P-wave is triggered is input into the GAT_M model. The multi-station seismic acceleration waveforms within 3 s after the first P-wave are used as the input of the GAT_M model. In this study, the strong earthquake data from of the K-NET strong earthquake observation network of Japan Institute of Disaster Prevention Science and Technology were used for model training and test experiments. Within 3 s after the first P-wave triggers, the mean error and standard deviation of magnitude estimation are -0.077 and 0.40 respectively, and R² is 0.72. The effects of magnitude, time window and number of stations on the performance of GAT_M model are also analyzed. Simultaneously, within 3 s after the initial P-wave triggers, the GAT_M model demonstrates a reduced magnitude estimation error compared to the traditional Pd method. In the case of complex sample data, the GAT_M model has a greater advantage and can be better applied to magnitude estimation.

The beam-column joint with replaceable energy dissipators has the advantages of convenient and economical repair after an earthquake. For a bending shear replaceable component with simple structure, easy construction, stable energy consumption capacity, and consistent tensile and compressive mechanical properties, a refined finite element model of flexural-shear replaceable energy dissipators was established. Then, the failure mode, hysteresis curve, skeleton curve and stress distribution state of the component were analyzed. The influence of parameters such as height-width ratio, width-thickness ratio of limb columns for replaceable energy dissipators, and overall slenderness ratio of energy dissipation zone was considered, and the effects on skeleton curves, stiffness and equivalent viscous damping coefficient of energy dissipators were systematically discussed. The analysis results showed that when the height-width ratio of limb columns in energy dissipators was greater than 4.0, the limb columns were prone to buckling behavior, and the recommended threshold value of the height-width ratio is 1.3~4.0. Increasing the width-thickness ratio of the energy dissipators decreases the initial stiffness and bearing capacity of the specimen, and it was recommended that the width-thickness ratio of limb columns should be no more than 2.5. When the slenderness ratio of the energy dissipation zone was large, its out-of-plane stability and energy dissipation capacity would be weakened, it is suggested the slenderness ratio of the energy dissipation zone not exceed 48. When height-width ratio of limb columns were less than 1.0 and greater than 2.5, the error between the theoretical prediction and the finite element calculation of the yield strength for flexural-shear replaceable energy dissipators was large, the latter was about 35% and 32% higher than the former respectively, so further research on the theoretical strength prediction model is needed to improve its prediction accuracy. The research results can provide reference for the seismic design of the flexural-shear energy dissipators.

Due to the influence of topography and traffic routes, small radius curved bridges with eccentrically support piers and variable pier heights are widely used. Due to the irregularity of the bridge caused by the difference in pier heights and the eccentric supports, a complex stress form of pressure-bending-shearing-torsion coupling in the eccentrically support pier will occur. Taking an interchange ramp bridge as the engineering background, a centralized hinge-fiber model based on nonlinear finite element software was constructed. The seismic vulnerability of eccentrically compressed piers in two models was compared by adopting the incremental dynamic analysis method. These two models include a model with the concave-type variable height piers (the CTVHP curved bridge) and a model with gradient variable height piers (the GVHP curved bridge). The results show that: in the small radius bridge with eccentrically support pier and variable pier heights, the probability of torsional damage of the intermediate pier is higher. When the pier torsional damage occurs, the exceeding probability of each pier damage level in the CTVHP curved bridge is greater than that in the GVHP curved bridge, which will lead to more serious torsional damage. Therefore the arrangement of the CTVHP curved bridge should be avoided in seismic design, at the same time, the seismic capacity of the intermediate pier should be enhanced. The research results of this paper can provide a basis for similar bridges.

To introduce the quasi-isolation concept in the transverse earthquake-resisting system of small-to-medium-span girder bridges, first the basic connotation of the quasi-isolation concept was elaborated based on the typical seismic damage statistical characteristics, and the performance roles of the critical elements (i.e. bearing, retainer and pier) were defined in the bridge earthquake-resisting system. Then, nonlinear analytical models were established for the bearing-retainer-pier systems considering the parameters of pier height and retainer capacity. Finally, the fragility analysis method based on the Copula functions was applied to investigating the coupling characteristics of the damage states of bearing, retainer and pier under earthquake actions, and the reasonable design capacity of retainer was explored according to the system-level deterministic fragility curves to satisfy the requirements of the quasi-isolation concept. The results showed that significant coupling relationships exist among the bearing, retainer and pier under seismic actions. The capacity of retainer has a notable impact on the damage states of bearing and pier. When the retainer capacity increases from 0 to 30% of the superstructural dead load reaction force, the damage probability of bearing decreases continuously, and a maximum decrease of 27.2% can be achieved at the complete damage state, while the damage probability of pier increases steadily with the maximum increase of 61. 6% at the complete damage state. The damage sequence gradually changes from the retainer, bearing, pier to the pier, bearing and then the retainer. When the retainer capacity is designed as 15%~20% of the superstructural dead load reaction force, the bearing sliding isolation and the pier plastic energy dissipation can be fully mobilized, and the severe damage probability of the bearing-retainer-pier systems under the seismic actions is the lowest and reduced by 16.3% when compared to that of the case without retainers.

Previous seismic damage investigations have shown that the seismic damage of engineering structures is closely related to the site seismic response. Therefore, studying the site seismic response has significant theoretical and practical value for the earthquake fortification of engineering structures. The geotechnical vertical array is an important platform for conducting site seismic response studies. As one of the main methods of obtaining strong ground motion records of the surface and underlying strata, it provides data support for the study of site seismic response. Based on the distribution of most of the existing geotechnical vertical arrays in the world, this paper introduces the basic information of the Garner Valley downhole array and the Treasure Island geotechnical array in the United States, the Port Island downhole array in Japan and the seismic monitoring array of site and structure of the China Institute of Disaster Prevention in detail from four aspects: geographical location, soil layer lithology, instrument layout, and velocity structure. Combined with a large number of relevant literatures, this paper summarizes the research progress on soil nonlinear dynamic characteristics, site amplification effect, and seismic response analysis methods of soil layers utilizing geotechnical vertical array. It looks forward to the problems that urgently need to be improved in the follow-up research, which has a certain reference value for the in-depth study of the dynamic response mechanism of soil at different depths and the site seismic response with deep soil layers.

The urban lifeline engineering system, serving as a key infrastructure that ensures the daily lives of residents, the functional operation of the city, the healthy development of the economy, and the long-term stability of society, is the cornerstone of resilient city construction. Research on seismic resilience assessment methods for urban lifeline engineering systems has achieved certain progress both domestically and internationally. However, the seismic resilience design methods for urban lifeline engineering systems remain underdeveloped. This paper expounds on the concept of seismic resilience design for urban lifeline engineering systems and delineates the differences between seismic resilience design for urban lifeline engineering systems and traditional seismic design for individual urban lifeline facilities. The basic framework of seismic resilience design, characterized by the “two dimensions”, is put forward, which ensures the structural seismic safety of individual facilities through the structural safety design of individual facilities, and guarantees the post-earthquake functionality and rapid recovery of the engineering system through the resilience coordinated design among individual facilities. The basic requirements for seismic resilience design, characterized by the “three objectives”, are established, ensuring structural seismic safety of individual facilities, meeting predetermined functionality of individual facilities and the engineering system, and enabling rapid recovery of the engineering system. The key steps of seismic resilience design, characterized by the “four components” are proposed, which include determining the seismic resilience goals for the engineering system, structural safety design for individual facilities, post-earthquake functionality verification for the engineering system, and identification of technologies and strategies for the rapid recovery of the engineering system. A unified seismic resilience design approach for urban lifeline engineering systems is established. This paper takes a road transportation system as an example to conduct seismic resilience design. The preliminary results validated the rationality and feasibility of the proposed seismic resilience design approach. The design approach enables the transition of seismic design for urban lifeline engineering systems from structural seismic design, which ensures the structural seismic safety of individual facilities, to seismic resilience design, which ensures post-earthquake functionality and rapid recovery of the engineering system. The proposed approach can also provide a practical solution to improve their seismic resilience.