In practical engineering applications, the use of low-carbon concrete materials is in line with the principles of sustainable development and helps to reduce the impact on the environment. Creep effects are particularly critical in the research on such materials. However, traditional characterization methods are time-consuming and often fail to account for the interactions of multiple factors. This study constructs a time-series database capturing the behavioral characteristics of low-carbon concrete materials over time. Three temporal prediction models—Artificial Neural Network (ANN), Random Forest (RF), and Long Short-Term Memory (LSTM) networks—were retrained for creep prediction. To address limitations in model architecture and algorithmic frameworks, an enhanced Adaptive Crowned Porcupine Optimization algorithm (ACCPO) was implemented. The improved performance of the ACCPO was validated using four diverse benchmark test functions. Post-optimization results showed remarkable improvements. For ANN, RF, and LSTM, single-metric accuracies increased by 20%, 19%, and 6%, reaching final values of 95.9%, 93.9%, and 97.8%, respectively. Comprehensive evaluation metrics revealed error reductions of 22.6%, 7.9%, and 8% across the respective models. These results confirm the rationality of the proposed temporal modeling framework and the effectiveness of the ACCPO algorithm. Among them, the ACCPO-LSTM time series model is the best choice.

Non-uniform corrosion cracking in reinforced concrete buildings constitutes a fundamental difficulty resulting in durability failure. This work develops a microscopic-scale multi-species electrochemical phase field model to tackle this issue. The model comprehensively examines the spatiotemporal coupling mechanisms of the full “corrosion-rust swelling-cracking” process by integrating electrochemical reaction kinetics, multi-ion transport processes, and a unified phase field fracture theory. The model uses local corrosion current density as the primary variable to accurately measure the dynamic interactions among electrochemical processes, ion transport, and rust product precipitation. It incorporates phase field method simulations of fracture initiation and propagation in concrete, establishing a bidirectional link between rust swelling stress and crack development. Experimental validation confirms that the model’s predictions about cracking duration, crack shape, and ion concentration distribution align well with empirical data, substantiating the efficacy of local corrosion current density as an indicator of electrochemical reaction rate. Parametric studies were performed to examine the effects of interface transition zone strength, oxygen diffusion coefficient, protective layer thickness, reinforcing bar diameter, and reinforcing bar configuration on cracking patterns. This model’s multi-physics field coupling framework, influenced by dynamic corrosion current density, facilitates cross-field interactions, offering sophisticated theoretical tools and technical support for the quantitative analysis, durability evaluation, and protective design of corrosion-induced cracking in reinforced concrete structures.

Fully graded concrete exhibits significantly enhanced mechanical properties due to optimized aggregate gradation. However, the effects of coarse aggregate morphological characteristics at the microscale—such as axial ratio (Ar) and angularity coefficient (Ac)—on fracture behavior remain insufficiently understood and require further investigation. This study investigates the fracture behavior of fully graded concrete using a peridynamic approach. First, a multilinear constitutive model of concrete considering nonlocal effects and damage evolution is constructed. Second, aggregate modeling via the Tensile-Concave Synthesis Method in peridynamics, and different property bonds and random bond parameters are introduced to characterize the heterogeneity and initial defects of concrete. Finally, the effects of loading rate, aggregate randomness, and the parameters Ar and Ac on the uniaxial tensile properties of concrete are systematically studied. The results demonstrate that peridynamics accurately captures the entire process of crack initiation and propagation in fully graded concrete. Uniaxial tensile behavior exhibits strong rate dependence. Different random aggregate models result in variations in the peak tensile strength of concrete. With the increase in Ar, the peak tensile stress gradually decreased by 4.15%, whereas the elastic modulus increased by 14.31%. As Ac increased, the peak stress exhibited an overall trend of first increasing by 5.14%, followed by a decrease of 3.8%. Therefore, in numerical simulations, the influences of loading rate and aggregate randomness should not be overlooked. Moreover, to enhance the strength of fully graded concrete, the proportion of aggregates with large Ar and Ac values should be minimized.

To overcome the inherent drawbacks of cast-in-place reinforced concrete bracing—such as long construction periods and difficult demolition—as well as the relatively high construction cost of steel structure bracing, while fully incorporating the respective technical advantages of these two traditional support systems, this paper proposes a novel hybrid prefabricated reinforced concrete (RC)–steel structure foundation pit bracing system. In order to investigate the overall bearing capacity variation in the standard components of this structure under complex external forces in foundation pits, a numerical model was established using the finite element software ABAQUS. The study examines the trend of the axial compressive bearing capacity of a single standard beam segment as the steel thickness of its external stiffening sleeve varies, as well as the effects of eccentric loading, oblique loading, and the presence or absence of auxiliary supports on the structural bearing capacity of multi-segment beam assemblies. The numerical analysis results show that the bearing capacity of a single beam segment exhibits a strong correlation with the variation in sleeve thickness, and a fitting curve of compressive strength as a function of thickness was derived. For the multi-segment assembly, an increase of 1 mm in the load eccentricity in the Y and Z directions reduces the ultimate peak load by approximately 20.95 kN and 23.94 kN, respectively; in the XY and XZ planes, an increase of 1° in the eccentric angle of the oblique load reduces the peak ultimate bearing capacity by about 6.02 kN and 9.67 kN, respectively. Auxiliary supports have a relatively minor influence on the structural bearing capacity. This research thoroughly explores the bearing capacity of the prefabricated steel–concrete composite and steel structure foundation pit bracing under complex working loads, providing strong support for engineering design and demonstrating broad application prospects.