H.-N. Li’s research while affiliated with Dalian University of Technology and other places

A large-scale radio astronomical telescope is a typical complex coupled system, consisting of a feed cabin, cables, and supporting structures. The system is extremely sensitive to wind loads, especially the feed cabin, which has high requirements for vibration displacement during operation, and excessive vibration may affect normal operation. To investigate the wind-induced vibration characteristics of such coupled systems, this study takes the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) as an example to conduct research. First, a refined finite element model of FAST is established, and a dynamic analysis using simulated random wind loads is conducted. The influence of the cable boundary on the time–frequency domain responses of the feed cabin is particularly considered. Then, the gust response factor (GRF) for different structural components within the coupled system is calculated. Finally, the evolution law of the GRF under various wind speeds and directions is revealed by parametric analysis. The parameter analysis only considers the wind directions ranging from 0° to 60°, because FAST is a symmetric structure. The results indicate that obvious differences are observed in both the rotational and translational displacements of the feed cabin under northward wind, especially the results along the east–west axis. When the supporting towers are considered, there is no change in the power spectral density (PSD) of the feed cabin in the low-frequency range. However, in the high-frequency range, taking the supporting towers into account leads to an increase in PSD and a resonance near the first-order natural frequency of the supporting tower. The GRF based on the dynamic response exhibits substantial deviations compared to those obtained from design codes, highlighting the need for an independent analysis when determining GRF for such coupled systems.

Probabilistic seismic hazard analysis (PSHA) is recognized as a reasonable method for quantifying seismic threats. Traditionally, the method ignores the effect of focal depth and in which the ground motion prediction equations (GMPEs) are applied to estimate the probability distribution associated with the possible motion levels induced by the site earthquakes, but it is limited by the unclear geological conditions, which makes it difficult to give a uniform equation, and the equation cannot express the nonlinear relationship in geological conditions. Hence, this paper proposes a method to consider the seismic focal depth for the PSHA with the example of California, and use a back propagation neural network (BPNN) to predict peak ground acceleration (PGA) instead of the GMPEs. Firstly, the measured PGA and unknown PGA seismic data applicable to this method are collected separately. Secondly, the unknown PGA data are supplemented by applying the BPNN based on the measured PGA data. Lastly, based on the full-probability equation PSHA considering the focal depth is completed and compared with the current California seismic zoning results. The results show that using the BPNN in the PSHA can ensure computational accuracy and universality, making it more suitable for regions with the unclear geological structures and providing the possibility of adding other parameters to be considered for the influence of PSHA.

Antenna mast structures are usually set on top of modern super high-rising structures to meet the requirements of communication and aesthetics, and such buildings are highly sensitive to horizontal loads that can greatly increase the acceleration and displacement responses during their life-cycles owing to the inherent high flexibility and low damping. As a result, the antenna masts with small mass and stiffness may suffer serious whiplash effect under the earthquake or wind excitations. In this paper, a multi-hazard protective system with hybrid isolated and energy-dissipated devices of isolation bearing, viscous damper and mild steel damper is presented for the typical inserted antenna mast structures on super high-rising structures. To determine the optimum parameters of the hybrid system that maximize the structural control efficiency under a single hazard of earthquake or wind load, as well as the coupled conditions of these two hazards, an optimization method based on the genetic algorithm is developed for the presented hybrid control system to resist various hazard scenarios. Objective functions are further proposed to penalize the accelerations and relative displacements at the top of the antenna mast structure. Taking a super-tall TV tower as an example, the OpenSeesPy platform is employed to establish the finite element (FE) model. The numerical results show that the optimization scheme for the hybrid energy-dissipated antenna mast system under a single hazard is not suitable for the other hazard condition, while the optimized results for the multi-hazard condition can give consideration to the effects of both earthquake and wind. Moreover, the sensitive analysis is performed to investigate the effects of each parameter of the hybrid system on the objective functions. It can be concluded that the proposed hybrid system performs well under earthquake, wind and coupled multi-hazards, which is of practical significance for the vibration control of antenna masts on super high-rising structures.

Although infilled walls are designed to serve as nonstructural components in frame buildings, their out-of-plane (OP) collapse during earthquake events may trigger additional damage to other structural components and inflict heavy casualties. Taking advantages of the metal tailing porous concrete (MTPC) and light-gauge steel studs, a new cast-in-situ composite wall with MTPC (CCWM) can be developed and regarded as a potential substitute for traditional masonry infilled walls. This paper experimentally investigates the OP mechanical behavior of a full-scaled CCWM via airbag loading test. A CCWM specimen with dimension of 2.4 m × 1.2 m × 0.2 m is fabricated by pouring MTPC into the cavity formed by panels and light-gauge steel stud system. The specimen is placed vertically in an elaborate loading system composed of steel frame, reaction brace, horizontal beams and a polyethylene airbag. Under the uniform OP force provided by the slowly inflated airbag, the failure pattern, load-displacement curves and strains of light gauge steel studs of the CCWM are observed and recorded during the test. Moreover, the finite element model of the specimen is developed in ABAQUS platform and the effects of slenderness ratio and aspect ratio on the OP mechanical behavior of the CCWM are numerically investigated. The results indicate that the specimen cracked vertically along the central line of the upper half part of the wall, and the connections between the support plates and vertical lattice studs are vulnerable locations for the CCWM. Owing to the special constitution of the CCWM, the arching action is short-term, and the crack strength can be adopted as the OP bearing capacity of the CCWM since it is quite close to the ultimate strength. Moreover, numerical results reveal that the OP strength and stiffness of the CCWM decrease when the slenderness ratio increases, but enhance with increasing aspect ratio.

Currently, the construction process of large offshore platforms worldwide involves building the topside and hull separately and then having them integrated. The jacking closure scheme by overlapped support tower bearing the topside is a new integration method, which has a great advantage over other traditional methods in vertical bearing capacity. But its weak bearing capacity to lateral forces like wind load limits the jacking height. Moreover, few engineering examples and academic researches also cause insufficient understanding of it. Therefore, this paper, based on the first deep-water semi-submersible platform with the10,000-ton oil storage worldwide, i.e. “Deep Sea No. 1” energy station, aims to evaluate the wind-resistant performance during the jacking closure process. Firstly, the background and the jacking closure scheme of this project are introduced in detail. Secondly, the finite element models (FEMs) of the jacking system are established according to the overlapped characteristics of jacking towers and the corresponding failure criteria. Then, the wind-induced vibration response is simulated, and the static pushover is conducted to evaluate the ultimate bearing capacity and its influencing factors. The failure criteria are checked using ANSYS parameter design language. It is found that “the occurrence of tensile stress on the contact surface” is the first and main failure mode of the structure. Additionally, the results also reveal that the strand cables can not only improve the ultimate bearing capacity of the structure but also change its weak direction. However, the improvement is gradually weakened with the increase of jacking height. In contrast, the contribution of the bracing pipes to the structural bearing capacity is always significant. These findings can be used to develop a more reasonable closure plan.

High-rise structures are normally tall and slender with a large height-width ratio. Under the strong seismic action, such a structure may experience violent vibrations and large deformation. In this paper, a spring pendulum pounding tuned mass damper (SPPTMD) system is developed to reduce the seismic response of high-rise structures. This SPPTMD system consists of a barrel limiter with the built-in viscoelastic material and a spring pendulum (SP). This novel type of tuned mass damper (TMD) relies on the internal resonance feature of the spring pendulum and the collision between the added mass and barrel limiter to consume the energy of the main structure. Based on the Hertz-damper model, the motion equation of the structure-SPPTMD system is derived. Furthermore, a power transmission tower is selected to evaluate the vibration reduction performance of the SPPTMD system. Numerical results revealed that the SPPTMD system can effectively reduce structural vibrations; the reduction ratio is greater than that of the spring pendulum. Finally, the influence of the key parameters on the vibration control performance is conducted for future applications.