In order to solve the problem that it is difficult to fully consider the dynamic characteristics （amplitude-phase frequency characteristics） requirements in the PID parameter design of electromechanical servo system，a PID design method for dynamic characteristics is proposed. The 9-order Transfer Function （TF） model of electromechanical servo system is established based on dynamic equation. The relationship between Routh criterion and TF coefficient is used to supplement the stability constraint of the system and the compatibility constraint of TF coefficient to ensure the stability of the system and the compatibility of TF coefficient in the PID design process. On this basis，based on the idea of parameter identification，the rational fraction orthogonal polynomial method is used to identify the coefficients in the TF model，so that the PID parameters are quickly determined，which improving the design efficiency，and multiple groups of controller parameters that meet the original index can be identified by adjusting the index data. The simulation results show that the designed PID parameters not only meet the requirements of dynamic characteristics，but also take into account the compatibility of system stability and TF coefficient. The design results are in good agreement with the simulation experiments.

The fatigue failure of the structure under vibration conditions has brought hidden dangers to its own service life and the personal safety of the user. At present，there are solutions for the structural vibration fatigue such as adding reinforcement bars and laying a large amount of damping materials，but the efficiency is often low and the additional mass is excessive. In order to solve the above problems，an additional acoustic black hole （ABH） is installed on the structure to reduce the stress amplitude and extend the service life by reducing the structural response. Using a cantilever plate as the reference structure，the steady state dynamics analysis is carried out by the finite element method. The results show that the stress response at the gap of cantilever plate is significantly reduced after the addition of rectangular acoustic black hole （RABH）. Through stress and fatigue experiments，it is verified that additional RABH can reduce the stress response at the dangerous point of the structure and extend the vibration fatigue life of cantilever plate structure.

At present，the big aviation countries already have mature gust wind tunnel test technology，but which is relatively backward in China，especially the gust wind tunnel tests equipment and technology of full aircraft model are lack. In this paper，a gust generator，a five-degree-of-freedom suspension system and a full elastic aircraft model are developed，and the wind tunnel tests of the whole model are carried out. The test results show that the gust field is stable，and the deviation of the gust velocity between the two ends and the center of the wind tunnel is less than 25%. The support stiffness of the model suspension system is small and the stability is good，which can meet the requirements of the gust wind tunnel test. The simulation results of the non-uniform gust field are close to those of the wind tunnel test，and the error of the moment of the wing root is less than 15%，and the error of wing tip overload is less than 0.2g.

Stochastic subspace identification （SSI） generates spurious modes in the process of identifying the dynamic characteristics of high-rise structures，which interferes with the automatic tracking of dynamic characteristics. This article has proved that the non-white noise excitation is one of the causes of spurious modes，and further proposed a signal reconstruction method based on multivariate variational mode decomposition （MVMD） for non-white noise excitation，which removes the influence of non-white noise excitation in signals and eliminates spurious modes. A Single-Pass clustering algorithm is proposed to eliminate discrete spurious poles. The above algorithm has been applied to on-site monitoring data of super high-rise structures，achieving long-term automatic identification and tracking of dynamic characteristics.

In the realm of stochastic nonlinear response analysis for large and intricate structures，the Monte Carlo simulation method stands out as a pivotal approach. However，its widespread practicality is hampered by its exorbitant computational costs. To surmount this challenge，researchers have endeavored to develop the active learning-based Gaussian process surrogate model algorithm. Despite its promise in reducing computational expenses，the optimization strategy associated with active learning necessitates further refinement to meet the exacting demands of engineering applications. For this purpose，we introduce a search function endowed with ‘intelligent’ attention capabilities. This function is meticulously crafted to concentrate on exceedingly high-risk one-sided tail events in engineering scenarios. By incorporating this search function，we have engineered an algorithm that surpasses existing methodologies. Our algorithm finds successful application in the analysis of complex adhesive anchoring structures within subway tunnel rings and linings. Compared to conventional methodologies，our algorithm exhibits a remarkable 30% reduction in the estimation error of single-tailed probabilities. This advancement facilitates a more precise estimation of the one-tailed probability distribution governing the stochastic response of complex structures. Consequently，it enhances the precision of assessing the occurrence probability of extreme events. These findings yield invaluable insights for decision-making processes in pertinent engineering domains and insurance sectors.

There are two kinds of stochastic seismic ground motion simulation methods： frequency-domain methods and time-domain methods. Based on the time-domain model of single filtered white noise，this paper proposes the time-domain representation for simulating stationary and non-stationary seismic ground motion processes. In essence，the time-domain representation can be regarded as linear superposition of deterministic functions modulated by a series of standard orthogonal random variables，and the set of orthogonal random variables is defined as the form of random orthogonal functions to achieve efficient dimension-reduction. Therefore，by introducing three kinds of random orthogonal functions，i.e.，Legendre orthogonal polynomial of non-Gaussian type，Hartley orthogonal basis and Hartley orthogonal elementary of Gaussian type，the acceleration process of seismic ground motion can be accurately represented in the time-domain model with only one elementary random variable. Numerical examples of seismic stationary ground motion process show the effectiveness of the proposed method，which is superior to the Monte Carlo method. The analysis of fully nonstationary seismic ground motion shows the engineering applicability of the proposed method.

The durability issue of multi-age masonry structures subjected to acid rain has become increasingly prominent，but a complete time-varying model of structural durability has not been formed at home and abroad. To study the relationship between the evolution of material properties and masonry properties，accelerated corrosion tests were carried out on mortar with different mix ratios，bricks，and masonry，and a compressive strength model of masonry components considering the number of acid rain erosion cycles was established. Based on the sample data of masonry in natural environment，the mathematical relationship between the degradation degree of mechanical properties of in-service masonry structures and their service life under the action of acid rain erosion was established. The typical structure method was used to analyze the seismic fragility of a two-story constrained masonry structure，and the influence of different parameters on the fragility curve and failure probability of constrained masonry structures under acid rain erosion was discussed. The results show that the probability of severe damage and collapse of restrained masonry structures under the action of acid rain erosion increases gradually with the increase of service life under the condition that other factors remain unchanged and the intensity of local vibration is higher.

In order to improve the climbing ability of rack vehicles，the gear-rack system is added to the traditional rail vehicles. Aiming at the problem that there are many kinds of gear-rack systems in the world at present，and the diversity of gear-rack systems equipped with them leading to the dynamic characteristics difference of rack vehicles，this paper considers the impact of gear-rack meshing on the basis of analyzing the generation mechanism of gear-rack meshing excitation，the rack vehicle coupled dynamic models with two kinds of Strub system，double row teeth Abt system and Locher system are established，and experimental verification on the model are carried out； Based on the model，the gear-rack meshing behavior of rack vehicle running at different speeds on the engagement section of the ramp is analyzed，and the influence of track irregularities on the gear-rack meshing center distance error is explored； On this basis，the wheel/rail action and car body acceleration of the rack vehicle are studied，and the rack vehicle safety are analyzed as well as stabitity. The results show that there are significant differences in the dynamic characteristics of rack vehicles with different gear-rack systems，and the Locher system has the best dynamic characteristics； The gear-rack meshing behavior of coaxial Strub system and double row teeth Abt system is poor and affected by the track irregularity obviously. The maximum impact value of the gear-rack contact force is 20.3 kN，and the meshing center distance error is 3.73 cm； The safety of coaxial Strub system and double row teeth Abt system is poor，and the maximum wheel/rail vertical force of double row teeth Abt system is 51.7 kN； The car body stability of the differential shaft Strub system is the worst. The maximum car body acceleration is 0.033 m/s²，and the stability index is 1.27. The conclusions offer theoretical support for the design，safe operation，and maintenance of mountain rack railways in China.

Vortex shedding and drift are key characteristics around the bridge girders during VIVs，and therefore it is necessary to reveal VIVs mechanisms of bridge girders from the perspective of vortex dynamics. A simplified vortex model was constructed from the perspective of aerodynamic work. Taking a typical streamlined-closed box girder as an example，a simplified wortex model was constructed from the perspective of aerodynamic work. Combined with the aerodynamic time-frequency characteristics of the bridge girder from wind tunnel experiments and the flow field characteristics around the girder based on numerical simulation method，the above model was verified and then the multi-order VIVs lock-in range mechanisms of the girder were revealed. The results indicate that the Strouhal number of the separation vortex characterizes energy effects of the vortex aerodynamics，which can be expressed as a positive integer multiple of the ratio of vortex-drift velocity to oncoming flow velocity，implying that a separation point can excite multiple VIVs lock-in ranges. There were 3 order lock-in ranges of vertical VIVs for the girder. Both the 2nd and 3rd lock-in ranges are excited and sustained by the large-scale separated vortexes separating at the leading edge and periodic drift in the drift distance between the separation point and the trailing edge. Especially，it takes about 2 and 1 vibration cycle for the separation vortexes to traverse the drift distance in the 2nd and 3rd order VIVs lock-in ranges，respectively. Therefore，they are dominated by the 2nd and 1st order simplified-vortex modes originating from the leading edge，respectively. This study verifies the rationality of the simplified-vortex model to deduce the vortices evolutionary characteristics around the bridge girder and provides a new methodology for VIVs mechanism of the bridge girders.

The key to damage pattern recognition lies in digging and classifying damage features from the response data of civil structures. To this end，a stack auto-encoder network with several auto-encoder hidden layers and a Softmax classification layer is built for analyzing frame structures. A hybrid learning mechanism is adopted to combining unsupervised and supervised learning strategies. Finite element analysis is used to generate the transmissibility function samples corresponding to different scenarios of a frame structure. The transmissibility samples are then divided into training，validation，and test sets. The parameters of the auto-encoder hidden layers，such as the weights and bias，are determined by a pre-training strategy in order to avoid the phenomenon of network over fitting. A fine-tuning step is employed to adjust the pre-trained network parameters，and the network hyper parameters are further adjusted based on the validation set. The measured transmissibility data are input into the network to evaluate the damage of the frame structure. The analysis results show that the proposed method can effectively extract and classify the damage features. Both the single and double damage scenarios at the frame joints were identified with higher accuracy and better anti-noise ability than the traditional shallow neural network.