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.

Based on the actual damage and the mechanical characteristics of the component, a dumbbell-shaped component is proposed by dividing the wall units along the midline of the span. To verify the phenomenon of internal force and deformation concentration during the loading process of dumbbell-shaped components, quasi-static tests of rectangular and dumbbell-shaped components with equal initial stiffness were designed. Wall shear strains and relative displacements at different positions were tested. The analysis results show that the dumbbell-shaped components undergo shear failure first, with damage concentrated between windows, causing the floor to collapse vertically along the side of the dumbbell-shaped component. Shear strains on the cross-section of dumbbell-shaped components are significantly higher than those of rectangular components, and the strain ratio gradually increases with displacement. Relative displacements on the upper and lower sides of the wall between windows indicate that as the loading displacement increases, the ratio of the upper wall to the wall between windows gradually decreases, while the displacement ratio between the wall between windows and the lower wall gradually increases. Both strain and displacement indicate that during the deformation process, internal forces and deformations gradually concentrate towards the wall between windows. Based on the analysis results, the collapse mechanisms of masonry structures and masonry-frame hybrid structures are discussed.

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 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.

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.

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.

Based on the database of the Pacific Earthquake Engineering Research Center, the collected seismic records were classified according to the fault distance of the seismic stations, and the amplitude, spectrum and time characteristics of the ground motions under different site conditions were studied and quantitatively analyzed. Taking the Huangdeng gravity dam as the research object, based on the three response quantities of downstream displacement at the upstream dam face, principal tensile stress at the upstream dam face and principal compressive stress at the downstream dam face, the influence of near-fault earthquake pulse characteristics on seismic response of gravity dams was investigated. The results show that the relative displacement of the toe of the top dam of Huangdeng gravity dam under pulse earthquake is 44% larger than that under non-pulse earthquake. The principal tensile stress at the dam heel is 30% larger than that of the non-pulse type. The principal compressive stress at the toe of the dam is 31% greater than the response value of non-pulsed earthquake. The impact of pulse earthquakes on the structure is not negligible compared with non-pulsed earthquakes, and the response values of the structure were significantly larger. Therefore, it is necessary to consider the impulsive action of near-fault earthquakes in seismic fortification.

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 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.

Soil dynamic parameters are crucial calculation parameters for the seismic response of soil. However, there is currently insufficient theoretical research on soil dynamic characteristics in Heilongjiang Province. To address this, we analyzed data on the dynamic shear modulus ratio and damping ratio of 286 groups of clay, clayey soil, and sandy soil at different burial depths in the region. We derived the characteristic parameters of each group of soil dynamic parameters and statistically obtained a fitting formula for the variation of these parameters with soil burial depth. Using this formula, we calculated the dynamic shear modulus ratio and damping ratio data of different soil types at different burial depths and verified the rationality of the fitting formula. We established six soil seismic response models using soil types with abundant data and input typical seismic motions in Heilongjiang Province. We calculated the fitting parameters a₁, a₂, E(λ_max), E(M), etc. of the fitting formula and studied the influence of the variability of characteristic parameters on peak ground acceleration, characteristic period, and plateau value of ground response spectrum by scaling the fitting parameters. Results show that with the increase of a₁ and E(λ_max) the damping ratio increases, resulting in a decrease in the site amplification factor F_PGA and an increase in the characteristic period T_g. The increase of a₂ and E(M) will lead to a decrease in the damping ratio, resulting in an increase in F_PGA and a decrease in T_g. The plateau value β has a large variability, fluctuating within a certain range without a definite increasing or decreasing trend. Variability has the greatest impact on F_PGA, followed by its impact on T_g, and then on β. The soil seismic response is the most sensitive to the variability of a₁. As the intensity of the input seismic motion increases, the error increases. Overall, this study provides necessary supplements to the research on soil dynamic parameters in Heilongjiang Province.