Cracks have a serious impact on the safety of concrete structures, and the tensile behavior of concrete is the key to control generation and propagation of crack. To improve the safety of concrete structures, it is crucial to understand the mechanical properties of cracked concrete under uniaxial tensile load. In this article, dynamic tensile test and tensile test after different fatigue damage were conducted to investigate the mechanical properties of cracked concrete. First, the damage evolution law of cracked concrete under dynamic tensile load was investigated by means of [ ] ([ ]: crack mouth opening displacement) control mode whereupon the relationship of stress– d _CMOD considering rates effect was obtained. Then, the change law of cracked concrete under uniaxial tensile load after fatigue damage was studied by analyzing four mechanical parameters including tensile strength, elastic modulus, critical displacement, and fracture toughness. The empirical formulas of the four parameters with numbers of fatigue cycles are given. Furthermore, acoustic emission technology was applied additionally.

Accurately predicting chloride concentration is crucial for the durability assessment of reinforced concrete structures. This study evaluates the direction-dependent applicability of four grey forecasting models, including conventional GM (1,1), Markov residual-corrected GM (1,1), GM (1,1) with full order time power terms (FOTP-GM (1,1)), and improved metabolic GM (1,1), for temporal and spatial chloride concentration prediction. Temporal sequences were constructed at fixed depths of 10 and 14 mm, while spatial sequences were obtained at exposure times of 280 and 320 d. Holdout, rolling one-step, and rolling two-step forecasting were employed, and model performance was assessed using statistical accuracy, numerical stability, and physical admissibility. The results showed that the temporal sequences exhibited quasi-linear growth, whereas the spatial profiles showed approximately exponential-like attenuation. Among the four grey models, FOTP-GM showed the most consistent temporal forecasting performance, with holdout MAPEs of only 2.1–2.3% and a pooled rolling one-step WAPE of 7.49%. Comparison with reference benchmarks further showed that simple linear and Fick-based models remained competitive for temporal forecasting, while the Fick-based model provided the highest accuracy for spatial extrapolation. In contrast, no single model was consistently superior for spatial prediction; although Markov-GM and FOTP-GM reduced overall statistical errors, both produced nonphysical negative concentrations in the deep low-concentration region. The optimal FOTP order was also generally higher for temporal sequences than for spatial sequences, further demonstrating the dependence of model complexity on forecasting direction. These findings reveal that under the investigated 28-d curing and exposure conditions, the grey forecasting models exhibited clear direction-dependent applicability associated with the distinct characteristics of temporal and spatial chloride sequences, owing to the distinct sequence characteristics of temporal accumulation and spatial attenuation. The proposed framework provides a rational basis for grey-model selection in spatiotemporal chloride concentration prediction and offers a practical small-sample approach for concrete durability assessment.

Buried PVC water pipeline is prone to deformation due to the influence of unfavorable factors such as external load and soil collapse. Once the deformation exceeds the critical threshold, serious consequences such as leakage and pipeline burst may occur. In response to the crucial issue of monitoring PVC pipeline deformation, the feasibility of utilizing FBG (fiber Bragg grating) sensing technology to monitor the deformation of acrylate polymer blended with poly resin (ABR) pipe subjected to external pressure and soil collapse is explored in this study. To assess the monitoring performance of FBG on the ABR pipe’s surface, an analysis method for package failure and pasted failure of FBG is introduced, along with the calculation formula for strain attenuation based on the Goodman model and the method for calculating the minimum adhesion length. A total of 20 ABR pipes with two cross‐sectional forms and different calibers are arranged with external pressure tests or soil collapse tests in this investigation. In the two tests, the circumferential strain measured by FBG is used to analyze the deformation of the ABR pipe and the bending strength. To validate the precision of FBG, a comparison between the strain curve measured by the strain gauge and that measured by the FBG sensors is conducted. The results of the two tests indicate that the deformation of the ABR pipe can be well monitored and the method can be applied to the field applications.

The metrological performance of FBG strain sensing systems is a critical premise for the precision of plastics water support pipeline structural deformation measurement, but the strain transfer loss of FBG attached on the plastics pipe subjected by dynamic force is unclear. This paper presents the first study on the effects of strain transfer between FBG, and acrylate polymer blended with poly resin (ABR)pipe sheets loaded by static and dynamic force. Theoretical methods of dynamic strain transfer theory combine with the exponentially decaying sinusoidal shock force time course is deduced and various dynamic parameters sensitivities studies are carried out, as well as that of the geometric parameters. The result of the dynamic theory is compared with the calibration test outcomes, while the ASTR of FBG attached on ABR sheet is compared with distributed optical fiber sensors (DOFS) and other pipe materials such as PVC, concrete, and steel. Results show that the ASTR of FBG is more accurate than that of the DOFS, and the grows of ASTR depending on the paste length of FBG, the Young's modulus of the middle materials, the thickness of the middle materials and attenuation coefficient. Paste length produced the largest increase, yet the magnitude and loading speed of the external force has unexpectedly little effect on ASTR. FBG seem low error, insensitive with dynamic force and independent with the material of matrix, and this demonstrates benefits that are stronger across the board than DOFS. This is not currently recognized by standards or by most reported studies.