At present, precast buildings have become the focus of the building industrialization, and the precast concrete frame structure has been widely used in the construction industry. On this background, a novel precast concrete frame with a bolt connection joint was proposed in this paper. The novel connections include connection steel plates, bolts and rubber layers. To investigate the seismic performance of the precast structure, two full-scale, precast, cruciform, reinforced concrete specimens, and a monolithic counterpart, are tested under reversed cyclic loading. For the precast specimens, two different thickness rubber layers are applied in the connection region, respectively. Seismic behavior was evaluated based on failure mode, hysteretic behavior, stiffness degeneration, ductility and energy dissipation. The results indicated that precast specimens had almost the same ultimate bearing capacity as the cast-in-place ones, and the failure mode is also the same. The precast specimens satisfied the strong column-weak beam design concept. Additionally, the initial stiffness is obviously decreased by adding rubber washers at the joint region, showing a semi-rigid characteristic. At the end of this paper, an equivalent stiffness computation method of the precast joint is discussed.

Based on the particularity of underwater concrete structure, a temperature tracer method based on heat transfer theory for crack detection was proposed. The basic way to identify cracks is to change the thermodynamic boundary conditions around cracks after cracking, which will lead to the change of cooling rate of the heat source near cracks. Based on this idea, a set of crack monitoring system composed of a temperature sensing system, a heating system, a monitoring tube and multiple casing tubes was designed. By using this system, a series of crack monitoring tests were carried out on two kinds of concrete specimens. The results show that the monitoring scheme with casing tube can detect the crack position in still water, and this monitoring scheme can detect both crack position and width in flowing water. The sensitivity of it is higher than that of the monitoring scheme without casing tube.

A new detection device was designed by integrating fiber Bragg grating (FBG) and polyvinyl chloride (PVC) tube in order to monitor the slip surface of a landslide. Using this new FBG-based device, a corresponding slope model with a pre-set slip surface was designed, and seven tests with different soil properties were carried out in laboratory conditions. The FBG sensing fibers were fixed on the PVC tube to measure strain distributions of PVC tube at different elevation. Test results indicated that the PVC tube could keep deformation compatible with soil mass. The new device was able to monitor slip surface location before sliding occurrence, and the location of monitored slip surface was about 1–2 cm above the pre-set slip surface, which basically agreed with presupposition results. The monitoring results are expected to be used to pre-estimate landslide volume and provide a beneficial option for evaluating the potential impact of landslides on shipping safety in the Three Gorges area.

Seepage monitoring is an important issue in the health monitoring and performance evaluation of geotechnical engineering, and one of the effective ways to monitor seepage is the thermal method. Based on the coupling effects between the seepage field and the temperature field, a point heat source (PHS) method is presented in this paper. The PHS seepage monitoring system was composed of a monitoring tube, multiple sensing–heating elements, a regulated power supply and a demodulator. The sensing element, a fibre Bragg grating (FBG) sensor, is integrated with the heating element (a ceramic heating tube). To optimise the monitoring scheme of this system, the influence of sensitivity-related factors on the identification effects of seepage is studied. The implementation pattern of the sensing–heating element, dimensions of the monitoring tube, heating voltage and heating period were used as factors for calibration experiments at different seepage velocities. The results reveal the following: (a) both implementation patterns, with heat conduction glue or a copper tube filled in the gap between the FBG sensor and the ceramic heating tube, obtained good monitoring results; (b) the dimensions of the monitoring tube significantly influenced the effects of seepage identification, where the larger the gap was between the monitoring tube and the sensing–heating element, the worse were the results of monitoring; (c) within the relevant ranges, the heating voltage and period had nearly no effect on the monitoring results. Based on these conclusions, a monitoring scheme that combines the sensing–heating element with heat conduction glue filled in the gap and monitoring tube of 20 mm dia. was chosen for a leakage monitoring experiment. Three patterns of the leakage passage were tested in the experiment, and each was tested with three values of leakage intensity. The results show that leakage was accurately determined by the PHS seepage monitoring system, and its estimates of flow flux agreed well with empirical values.