As a semi-active control device, the magnetorheological (MR) damper has received much praise for its great controllability, quick response, and lower input power. However, the problem of liquid leakage arises after its long-term service, severely affecting its performance and service life. To solve this problem, this paper proposes fully vulcanizing and consolidating viscoelastic material, the cylinder barrel and the piston rod, which replaces the traditional dynamic seal with a static seal, and developing a new leak-proof MR damper. Considering that viscoelastic material has a certain energy dissipation and fluid-structure interaction with MR fluid, the correction factor of the pressure gradient is introduced to establish the mechanical model of the leak-proof MR damper which is to be tested. The testing result shows that warpage deformation of viscoelastic material weakens the damping force of the MR damper and the weakening effect increases with current intensity. Given the influence of current intensity on the correction factor, the complete mechanical model of the leak-proof MR damper is obtained on the basis of the verified model. Through the comparison between the theoretical calculation curve and the test curve, the revised mechanical model is found to well reflect the mechanical properties of the leak-proof MR damper.

This paper presents the results of a series of pullout tests that were performed on Glass-fiber-reinforced polymer (GFRP) bars embedded in concrete, while providing a detailed report on the influence of various variables that impinge upon bond behavior, such as the surface characteristics and diameter of the bars, concrete strength, as well as the confined effect of stirrups. The Bertero-Popov-Eligehausen (BPE) and Cosenza-Manfredi-Realfonzo (CMR) models analyzed the bond stress (τ)–slip (s) relationship between GFRP bar and stirrups-confined concrete. The tests results indicate that when the bond failure interface only occurs on the surface of a GFRP bar, the bond strength is not dependent upon the concrete strength. Moreover, the results indicate that in comparison to specimens without stirrups, their stirrup-containing counterparts are more prone to pullout failure with greater ductility and higher bond strength and corresponding slip. The BPE and CMR models are able to investigate the τ-s relationship between GFRP bars and the stirrups-confined concrete with accuracy. With the experimental data, the specific parameters in the models classified by surface characteristics have been suggested.

A conventional method to study the durability of Glass Fiber Reinforced Polymer (GFRP) rebars is to carry out tensile tests on the corroded GFRP bars. The degree of corrosion of the GFRP bars could be quantified based on the measured ultimate tensile strength and the calculated strength reduction. However, it is difficult to directly monitor the reduction in tensile strength of the GFRP rebars that are embedded in concrete; therefore, this method cannot be implemented in real engineering practices. This study presents the reduction in elastic modulus of the GFPR rebars by real-time monitoring of the strain of the GFRP rebars, and then establishes the degradation model of the elastic modulus for the GFRP rebars in an alkaline corrosion environment. Therefore, the relationship between tensile strength and elastic modulus of GFRP rebars is proposed and verified by the experimental data obtained from the literature. The results show that it is feasible to use the Arrhenius equation to simulate the degradation model of the elastic modulus of the GFRP rebars. Thus, the tensile strength of the GFPR rebars can be related to its elastic modulus. Using the proposed relationship, the durability of GFRP rebars can be predicted by real-time monitoring of the elastic modulus of the GFRP rebars.

Macro fiber composite (MFC) is a new type of high-performance smart piezoelectric material with an ultrathin section, which is used to decrease vibration and the noise of plate and shell structures due to high output and good flexibility. At present, the classical plate theory (CPT) has been adopted to study actuation performance of MFC. It does not consider shear deformation of an MFC integrated plate structure and cannot obtain the actuation force distribution of MFC, so that the accurate exerting position of the actuation force cannot be obtained. To solve this problem, this paper proposes that the third order shear deformation theory (TSDT) should be used to deduce the MFC actuation force formula which considers shear deformation of the MFC integrated plate structure and introduces a local displacement distribution function to ensure that the adhered interface between the MFC and the plate satisfy deformation compatibility and stress balance. Consider the end displacement calculation of an MFC integrated beam structure, for example. The comparison among the MFC actuation force formula based on TSDT, the MFC actuation force formula based on CPT, and the MFC integrated beam experiment indicates that the first can obtain higher calculation accuracy. On the basis of studying the MFC actuation force formula, the actuation simulation calculation of the plate by MFC is performed through making MFC equivalent to the actuation force and bending moment acting on plate structure to carry out the actuation experiment of an MFC integrated plate structure under the actuation of harmonic voltage of different amplitude values. The result shows that the experiment well matches the acceleration time history of simulation.

Presently, most of the common placement methods of actuators are based on the structural response and system energy to select the optimal locations. In these methods, the contribution of controllability and the energy of seismic excitations to each mode of the structure are not considered, and a large number of cases need to be calculated. To solve this problem, the Clough–Penzien spectral model is combined with the Luenberger observable normal form of the system to calculate the energy of each state. The modal disturbance degree, considering modal energy and controllability, is defined by using the controllability gramian matrix and PBH system controllability index, and the modes are divided into the main disturbance modes (MDMs) and the secondary disturbance modes (SDMs). A novel optimal placement method of actuators based on modal controllability degree is proposed, which uses MDMs as the main control modes. The optimal placement of actuators and the vibration control simulation of a 20-story building model are carried out. The results show that the vibration reduction effect of the proposed placement method is significantly better than that of the method of uniformly distributed actuators (Uniform method) and the classical placement method of actuators based on the system controllability gramian matrix (Classical method).