Based on the seismic performance test of one common shear wall and four ultra-high performance concrete (UHPC) prefabricated composite shear walls, the hysteretic properties, bearing capacity, ductility, stiffness, and energy dissipation capacity were studied. The effects of width-to-height ratio, replacement by expanded polystyrene (EPS) and vertical reinforcement connection on the seismic performance were analyzed. The results show that compared with the common shear wall, the UHPC composite wall has excellent seismic performance and the maximum bending capacity increases. The UHPC prefabricated slab and steel truss can work well with the concrete in the cavity. The hysteretic curve, skeleton curve and stiffness degradation curve of UHPC composite wall are basically consistent with the trend of common shear wall. In the range of the ratio of height to width, the smaller the ratio of height to width, the greater the flexural capacity and stiffness of the composite wall of UHPC, and the worse the energy dissipation. Replacement by EPS can improve the energy dissipation capacity of composite shear wall after yield, but reduce the ductility of UHPC composite wall. Only using the vertical reinforcement of the concealed column to connect with the base has little effect on the flexural capacity and energy dissipation of the UHPC composite wall, but it can facilitate the construction greatly.

In order to clarify the differences of wind vibration response of base-isolated buildings calculated by three commonly used biaxial restoring force models of MSS, Casciati and Harvey and Gavin, three models were used to simulate the restoring force of lead-rubber bearing under horizontal uniaxial and biaxial displacement. Comparing the differences of tests or finite element results. The differences in base displacement, top displacement and top acceleration for a numerical example were analyzed using three models. The results show the trends that the restoring forces of three models simulate the lead-rubber bearing in uniaxial cyclic displacement, square and offset square displacement are basically the same. While simulating circular and offset circular displacements, the biaxial restoring force shape of MSS model is different from the finite element results, which cannot simulate the coupling behavior of the bearing accurately, and the error of Casciati model is slightly smaller than that of Harvey and Gavin model. The Casciati model and the Harvey and Gavin model are basically the same in calculating the wind vibration response. For the root-mean-square of the cross-wind response, the differences between the three models are not significant. For the root-mean-square of the along-wind base displacement, top displacement and top acceleration, the MSS model is slightly smaller, while for the peak factors of base displacement in along-wind and cross-wind, the MSS model is slightly larger. For the variation of the peak factor of top acceleration and the ratio of the maximum top acceleration of bidirection to unidirection with wind speed in along-wind and cross-wind, the MSS model differs from others. With the consideration of the simulation of biaxial coupling effect and the difference of wind vibration response, the Casciati model is suggested to consider the influence of biaxial restoring force model on wind vibration response of base-isolated buildings.

Efficient detection of apparent cracks in reinforced concrete (RC) structures can provide evidence for rapid assessment of earthquake-damaged structures. Such work exhibits large and repetitive characteristics in both earthquake sites and laboratory environments, therefore, it is suitable to adopt the computer vision technology to make up the inefficiency and uncertainty of manual methods. Using images from consumer-grade cameras as data sources, a convolutional neural network (CNN) model suitable for concrete apparent crack detection is constructed by integrating U-Net and VGG-16, and the model training and testing are completed based on a multi-type RC component crack image database. Morphological operations and Otsu threshold segmentation are used to further optimize the crack detection results as input data for width measurement. To reduce the measurement error of crack width caused by the non-perpendicularity of the camera axis to the crack plane, perspective error correction is performed on the original image using specific targets. After verification, the average deviation of the crack width measurement after perspective error correction can be reduced up to 25%.

By reviewing literature in the field of earthquake engineering, the pulse-component models of earthquake ground motions are collected and organized. The characteristics of various pulse models are compared and discussed. The research significance of these pulse-component models is concluded and organized to form a systematic research framework. According to the existing research results, it is pointed out that the seismic hazard analysis considering the pulse effects in earthquake ground motions is the core in the research framework. Although the pulse models use different mathematical expressions to describe the same pulse characteristics, their performance is similar in structural dynamics. There are similarities between the pulse models with the forward directivity effect and those with the fling-step effect. At last, the details on considering the pulse effects in ground-motion selections for seismic design of structures are discussed.

In order to solve the rail corrugation in the curve section of steel spring floating slab track in a metro, firstly, the characteristics of rail corrugation were tested on site. Secondly, according to the characteristics of rail corrugation, the precise tuning and development of wide-frequency tuned mass damper (WTMD) were carried out. Then, the parameters such as mass, stiffness and damping of WTMD were input to the established Vehicle-WTMD-Steel spring floating slab coupled dynamic model. The floating slab and foundation were considered as flexible bodies in the model. The wheel-rail contact was solved by the Kik-Piotrowski model, a multi-point non-Hertzian contact model. The 5th grade power spectral destiny formula from USA superimposed on the measured corrugation irregularity spectrum were used as excitation. The finite element software ANSYS and the multi-body dynamics simulation software UM were used to carry out the coupled dynamics analysis, and the WTMD parameters were optimized iteratively. At the same time, the rail vibration accelerations obtained by simulation analysis with or without WTMD were compared with the field measured data, and the influence of WTMD on rail vibration was studied. Finally, the total rail vibration level, track decay rate and three times corrugation tracking tests, with or without WTMD, were carried out to study the influence of WTMD on the rail vibration, the track decay rate and the corrugation development. The results show that: The first three dominant frequencies of the designed WTMD are 518 Hz, 700 Hz and 759 Hz, which are consistent with the vehicle passing frequency (520~830 Hz). The simulation and measured data are in good agreement, and the rail vertical vibration acceleration RMS is reduced from 200 g to 20 g after the installation of WTMD, and the vibration reduction effect is 8.1 dB. The WTMD can improve the vertical and lateral track decay rate and suppress the vertical and lateral rail pinned-pinned resonance. The three times corrugation tracking tests find that the rail corrugation develops slowly after the installation of WTMD, the rail corrugation is invisible.

The floor acceleration amplification (FAA) reflects the amplification effect of the main structure on the ground acceleration, but the current specification and research mostly rely on historical floor records or finite element analysis results. When complex building structures are involved, the results of calculation analysis and actual earthquake damage are often different. Based on the recorded data of the shaking table test of the scaled model of the integral structure, the FAA distribution of prototype structures along the height are obtained by fitting analysis. Using the shape model of quasi seismic response spectrum, the FAA distribution surface with a certain guarantee rate is obtained, and the corresponding calculation formulas for different structural types are proposed respectively. It can better reflect the FAA distribution characteristics of complex building structures compared with the specification. Finally, the influence of site predominant period change on FAA distribution characteristics of this type of building structure is qualitatively explored.

The pervious conditions of seabed sediments can directly affect their dynamic response characteristics during earthquakes, but most existing theoretical studies directly assume that the bottom of the sediments was an impermeable boundary. Therefore, based on Biot’s saturated porous media theory, through the analytical and semi-analytical solutions of the seabed transient response or steady-state response, the influence of the bottom water permeability conditions of the sedimentary layer on its dynamic response characteristics in earthquakes is studied. It is found that under the condition of bottom displacement excitation, fast wave or slow wave will generate the same type of compression wave when passing through the impermeable boundary of the sediment layer, and two types of compression waves will be generated when passing through the completely permeable boundary of the sediment layer. Even under the same excitation conditions, the vibration amplitudes of the two types of compression waves generated in the sediment layers with different permeabilities are significantly different. Permeable conditions at the bottom of the sediment layer also affect the frequency response characteristics of the seabed, and the displacement amplification coefficient of the bottom permeable sediment layer is large at low frequency. On the contrary, at high frequency, the displacement amplification coefficient of the bottom impermeable sediment layer is large.

In order to get rid of the problems of inaccurate instantaneous frequency (IF) estimation and energy dissipation inside the local maximum synchrosqueezing transform algorithm, an improved method is proposed and named as local maximum synchrosqueezing transform (ILMSST). Firstly, multiple iterations are performed on the obtained IF positions to get more precise IF positions. Secondly, the IF positions where maximum values of STFT coefficients appear are searched and then moved up and down to pre-estimate IF bands. After that, the STFT coefficients outside the pre-determined IF bands are totally assigned to zero. Finally, the IF positions that correspond to local maximum values of STFT coefficients are found out and subsequently an operation of reassignment is performed on the obtained IF positions to get refined IF bands. To verify the effectiveness of the proposed method, two numerical cases and two tests on a seven-story reinforced concrete shear wall structure and a steel cable with time-varying tension forces are investigated. The results demonstrate that the proposed ILMSST method behaves better than current local maximum synchrosqueezing transform. Moreover, it not only enhances the accuracy of IF estimation but also improves time-frequency energy concentration.

Jishishan earthquake caused serious damages to buildings in some areas of Gansu Province and Qinghai Province. The seismic damages of rural buildings at 11 survey points were investigated in areas with seismic intensities of 7 and 8 degrees. The seismic damage investigation shows that the earthquake disaster regions are mainly areas of towns and villages, and the main types of house structures are civil structure, brick and wood structure and unfortified brick concrete structure. In areas with intensity 8 degree, houses of civil structure mainly perform as severely damaged or collapsed. Brick wood structure and unfortified brick concrete structure houses were mainly damaged moderately and severely. Fortified brick concrete and reinforced concrete frame structure houses were damaged slightly and moderately. In areas with intensity 7 degree, civil structure houses were mainly damage moderately. Brick wood structure and unfortified brick concrete structure houses mainly damage slightly and moderately. Fortified brick concrete and reinforced concrete frame structure houses were mainly damaged slightly and basically intact. The seismic damage caused by the earthquake is more severe than that of earthquakes with the same magnitude, which is related to factors such as the amplification effect of ground-motion peak values of complex terrain in the earthquake area, poor quality of building masonry, and unreasonable structural stress of buildings. It is recommended to carry out further research on site amplification effect and spectrum impact of complex terrain, and attach importance to the earthquake resistance promotion and practical technology development of non-structural components of buildings.

Flexural performance tests on 11 beams of full-scale reinforced concrete (RC) with HRB635 high-strength reinforcement were carried out to investigate their damage mechanism, failure mode as well as strength and ductility. The feasibility of the Chinese code formulae for calculating the ultimate flexural load bearing capacity and the maximum crack width of flexural components was also assessed for RC beams with high-strength reinforcement. The results indicate that the mechanical behavior and damage mechanism of the RC beams with HRB635 high-strength reinforcement are basically identical to those of RC beams with common reinforcement. The tensile high-strength reinforcements yielded first, then the compressive concrete crushed, and the tensile strength of the high-strength reinforcements can be fully utilized. The ultimate flexural moments of the test specimens calculated by the Chinese code were close to those of the test values, indicating that the flexural load bearing capacity of the beams with high-strength reinforcement can still be calculated according to the current Chinese code. The tested maximum crack widths of the specimens under serviceability limit state all exceeded the limit value of flexural structural components under short-term load, indicating that the design of RC beams with high-strength reinforcements may be controlled by the serviceability limit state rather than ultimate limit state. The calculated maximum crack widths were close to the tested ones, while the calculated results were slightly larger.