This paper presents the results of experimental testing a novel dual-tube self-centering buckling-restrained brace (SC-BRB) with pretensioned basalt fiber-reinforced polymer (BFRP) composite tendons. Cyclic tensile experiments are first conducted on two sets of BFRP tendons with different diameters. The results confirm that the BFRP tendons have a stable cyclic elastic modulus and sufficient elongation capacity, making them suitable for use as the self-centering tendons in SC-BRBs. Quasi-static experiments are performed using two dual-tube SC-BRB specimens with different core plate areas. Before the failure of the self-centering system, both specimens stably exhibit the expected flag-shaped hysteresis response, with a relatively small residual deformation. The internal forces in the BFRP tendons and the gaps between the tubes and the end plates are measured to validate the performance of the self-centering system. Both specimens meet the requirements for ultimate ductility and cumulative ductility in braces. For a similar initial pretension, a greater core plate area results in greater residual deformation; however, the cumulative energy dissipation and the equivalent viscous damping are also greater.

This paper presents a seismic response evaluation of self-centering prestressed concrete frames with infill walls (SCPC-IW frames). Three types of infill walls with different load capacity were selected to be installed in a bare self-centering prestressed concrete frame (SCPC-Bare frame). Beam web friction devices are included in the beam-column connections to provide energy dissipation capacity. Numerical models of the SCPC frame, and the three SCPC-IW frames were established and analyzed in a finite element software, OpenSees. Firstly, the nonlinear static analyses and nonlinear dynamic analyses under 44 ground motions were performed. Secondly, the incremental dynamic analyses (IDAs), seismic fragility analyses, and collapse resistance capacity evaluation were conducted. The results showed that the initial stiffness, energy dissipating capacity of SCPC-IW frames are increased in comparison to SCPC frames. After adding infill walls, the lateral displacement of the SCPC-IW frames decreases. However, the residual deformation and axial compression ratio of the SCPC-IW frame increases. As the infill walls strength increases, the increased amplitude of residual displacement becomes much larger than the decreased amplitude of the drift. It is concluded that when the load capacity of infill walls ranges from 37% to 79% of the web friction force, the SCPC-IW frames can achieve a good balance in terms of stiffness, energy dissipation, and self-centering capability as well as collapse resistance capability.

The dual-tube self-centering buckling-restrained brace (SC-BRB) with pretensioned basalt fiber-reinforced polymer (BFRP) composite tendons is a novel bracing system that consists of an energy-dissipative BRB and self-centering system that is used to overcome the residual drift. In this study, a finite-element model of the dual-tube SC-BRB is constructed to analyze its hysteretic characteristics. By analyzing and comparing the model of the BRB and the self-centering system, respectively, the accuracy of the model parameters, such as material, contact, and constraint, was verified. The tube length tolerance was introduced to the model of the SC-BRB, which effectively reduced the initial stiffness of the brace and corresponded with the test results. Based on the finite-element model of the SC-BRB, the influence of four parameters, including the material of the pretension tendons, initial pretension force, area of the pretension tendons, and core plates, on the hysteretic performance of the brace is discussed. This paper improved the configuration of the SC-BRB by adding a rubber cushion between the end plate and tubes. The finite-element analysis results indicated that the rubber cushion could not only decrease the initial stiffness of the brace but also reduce the influence of the tube length tolerance on the initial stiffness of the brace.

A tunnel is a symmetric structure working under uncertain load. In the traditional method of monitoring and measurement of tunnel deformation, only a small number of symmetric measuring point displacements are engaged to represent the overall deformation of the tunnel, and it is difficult to fully reflect the displacement changes of the tunnel during the construction process. In this paper, a deformation monitoring method is proposed for the tunnel construction process based on 3D laser scanning technology. Initially, 3D laser scanning was used to obtain scattered clouds of irregular structures considering the New Austrian Tunneling Method (NATM). Afterward, the modified B-spline interpolation and greedy triangulation were used to fit the surfaces. Moreover, the normal vector matrix was innovatively applied to express the deformation of the tunnel fitting surface, which solved the problem of scattered point clouds in 3D laser scanning. A normal vector was obtained by the intersection of the normal of one fitted surface with the other. Subsequently, the maximum entropy method was introduced to form the probability density function of the normal vector, and the 1% and 5% probability eigenvalues were used to analyze the overall deformation trend of the tunnel. Finally, the eigenvalue of 5% probability, which was less affected by construction uncertainties, was selected for analysis. This way, the analysis and prediction method for overall tunnel deformation was established.