During long-duration dynamic loads, such as wind loads or seismic effects, the internal temperature and pressure of a damping cylinder escalate rapidly, which induce shifts in the mechanical attributes of viscous fluid dampers (VFDs). This study investigated the mechanical performance of VFD considering the coupling effects of temperature and pressure under long-duration loads. First, we analyzed the mechanical and energy-dissipation performances of the dampers based on the dynamic mechanical tests considering different loading frequencies, displacement amplitude, and loading cycles. The experimental results indicated that both temperature and pressure influenced the output of the dampers, and in the sealed environment of the damper pip, temperature and pressure exerted mutual influence. Furthermore, the relationship between the damping coefficient and temperature–pressure coupling effects was obtained. Subsequently, an improved mathematical model for the mechanical performance of a gap-type VFD was proposed by considering the macroscopic energy balance of the entire fluid within the damper. Finally, the accuracy of the mathematical model for VFD under long-duration dynamic loads was validated by comparing the computational results with the experimental data.

This article presents a Lyapunov precise integral-based analysis method for seismic structures with added viscous fluid dampers. This study uses the full stress algorithm as the optimization method, considering the mean square of interstory drifts as the optimization objective, the position of the damper as the optimization object, and the random vibration analysis method as the calculation method to optimize seismic frame structures with viscous dampers. A precise integral solution is derived for the Lyapunov equation based on the general expression of the Lyapunov differential equation for the damping system under the excitation of a nonstationary stochastic process using two types of modulation functions: $g(t)=1$ and $g(t)=\sqrt{t}$. Finally, the optimal damping arrangement is achieved using this method with a six-layer non-eccentric planar frame. In addition, the optimization results of this study are verified with those in the literature using time-history analysis, which verifies the feasibility and effectiveness of the proposed method. This study provides a method for the optimal configuration of dampers for seismic response of structures, which is beneficial for engineering applications and the protection of seismic structures.

Seismic isolation technology has been extensively used in long-span spatial structures to alleviate losses caused by earthquake disasters. However, limited experimental studies have been conducted to examine the impact of horizontal and vertical vibrations in long-span roof structures with rubber bearings as isolation layers on the isolation effect. This paper presents a study that carried out shaking table experiments on 1/40 scale long-span steel frames, both with and without base isolation. It explores the interplay of horizontal and vertical vibrations in long-span roof structures equipped with rubber bearings, and its influence on the isolation effect. Three ground motions, including horizontal bidirectional (2D) and bidirectional-plus-vertical (3D) components were used as the seismic excitations. The whole structural dynamic responses of the base-isolation (BI) model and fixed-base (FB) model, the local responses of the grids and isolation bearings were measured. Under 2D seismic excitation, the grid layer in the FB model exhibits a substantial vertical acceleration response. When exposed to 3D seismic activity, the isolation system successfully delivers its expected isolation outcome. Although the isolation bearings could not attenuate the vertical seismic acceleration response induced by vertical ground motion, they effectively reduced the vertical dynamic response generated by the coupling by suppressing the horizontal seismic response.