The isolation structure is equipped with isolation devices to extend the natural vibration period and reduce the seismic response. However, improper construction causes the infill wall to be built around the isolation device, which restricted the free movement of the superstructure, thus affecting the actual isolation performance of the structure. In order to quantify the impact of the above unfavorable factors on the seismic isolation performance of the structure, this paper takes a certain reinforced concrete(RC) frame as the research object, uses a method of combining in-situ testing and numerical simulation, and compares and analyzes in the OpenSees considering whether the constraint effect of the infill wall is taken into account. Seismic response of isolation structures under different types of earthquake motions. The research results show that compared with unconstrained seismic isolation structure, the maximum acceleration of the upper floors, the maximum inter-story drift and the maximum base shear force of structures with seismic isolation layers constrained by peripheral infill walls increase by 20.4%, 38.7%, 35.7% under frequent earthquakes. The displacement of the isolation layer is reduced by 79.4%. Under the action of seismic precautionary earthquakes, they increase by 21.6%, 59.8%, 86.5%, respectively, and the displacement of the isolation layer is reduced by 37.8%. Under the action of rare earthquakes they increased by 17.7%, 19.4%, and 14.9% respectively, and the displacement of the isolation layer decreased by 10.3%. As the peak acceleration of the input ground motion increases, the lead rubber bearing will play a greater role only after the infill wall is damaged. Under rarely occurred earthquake, the seismic isolation layer breaks through the constraints of the surrounding filling walls and can basically achieve the seismic isolation effect.

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.

The fixed connection between the piers and the superstructure of rigid-frame bridges with high piers exhibits limitations in seismic design. Cracking of the cross-section and prestressing tendon stress loss can be found in the main girder subjected to seismic loads. The inertialr system ( i. e. tuned mass-damper-inerter, TMDI) contains an inertial container and a traditional tuned mass damper (TMD). It is a new method for structural seismic control in recent years. This study focuses a high-pier, long-span continuous rigid-frame bridge, considering the construction process and combining Midas Civil and the OpenSees to establish a nonlinear seismic response numerical model. Using 10 near-fault pulse-like ground motion records as input, this study investigates the seismic control behavior of a distributed configuration of multiple TMDIs. The results show that when the ground motion excites the bridge along the longitudinal direction, TMDIs can effectively prevent the cracking of the top and bottom slabs of the main girder, although the internal forces of the web of the main girder increase slightly. When the ground motion excites the bridge along the transverse direction, TMDIs significantly reduce the internal forces on the web of the main span. When ground motions are input in both horizontal directions, TMDIs can effectively mitigate the stress on the top slab, bottom slab, and web of the main span. Regarding the pier response, the average seismic reduction proportions of the maximum displacement at the pier top are 52% in the longitudinal direction and 21% in the transverse direction, respectively. The seismic reduction proportions of the maximum bending moment in the longitudinal direction is 31%. Although TMDIs increase the bottom bending moment of the pier by approximately 10% in the transverse direction, they effectively control the residual displacement of the bridge pier.

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.

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.

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.

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.

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.

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.

In the seismic response analysis of locally irregular sites such as basins under plane wave incidence, it is usually assumed that the input seismic motion is of a single wave type, i.e., SV wave, SH wave, or P wave. However, the actual incident motion is generally a multi-dimensional coupled shaking case. Based on the spectral element method, the ground motion response of a three-dimensional semi-ellipsoidal sedimentary basin under the vertical incidence of plane waves is simulated. By analyzing the distributions of peak ground acceleration (PGA) and the corresponding amplification factor, the seismograms along the surface point profile, and the response spectrum ratio distribution at the characteristic frequencies, the ground motion amplification features of the sedimentary basin under multi-dimensional ground motion input are investigated through comparisons with the results of single wave type incidence. The results show that compared with the unidirectional horizontal seismic excitation, the bidirectional horizontal seismic input has a significant amplification effect on ground motion in the basin, and the maximum amplification factor can reach 1.87. Considering the influence of simultaneous input of bidirectional horizontal ground motion, the distribution characteristics of the peak ground acceleration will change significantly. The superposition and interference of waves propagating in different directions result in an asymmetrical PGA distributions. The bidirectional ground motion input makes the wave propagation characteristics more complex, and the location of the strongest ground shaking changes. In addition to the amplification of the response spectrum value, the bidirectional input also has a certain influence on the distribution of the predominant period.