A statistical damage model (SDM) of fully-graded concrete was created using statistical damage theory, based on the mechanical properties of axial tension and axial compression of the material. The SDM considers two damage modes, fracture and yield, and explains the intrinsic connection between the mesoscopic damage evolution mechanism and the macroscopic nonlinear mechanical behavior of fully-graded concrete. The artificial bee colony (ABC) algorithm was used to obtain the optimal parameter combination through an intelligent search of parameters ${\epsilon }_a$, ${\epsilon }_h$, ${\epsilon }_b$ and $H$ in the constitutive model by taking the test data as the target value, and the sum of the squares of the differences between the target value and the predicted value as the objective function. The SDM numerical simulation model of fully-graded concrete is proposed by compiling subroutines in FORTRAN by constructing two modules of data model and damage analysis. The numerical results under uniaxial and biaxial forces are in agreement with the experimental results, which verifies the accuracy of the program. The model also analyzes the characteristics of mesoscopic damage evolution and predicts the mechanical properties under triaxial forces. The results show that the proposed numerical simulation model can reflect the salient features for fully-graded concrete under uniaxial, biaxial and triaxial loading conditions, and the evolution law of mesoscopic parameters. Therefore, the proposed model serves as a basis for the refined finite element analysis of hydraulic fully-graded concrete structures and reveals the mesoscopic damage mechanism of concrete under different load environments.

In order to investigate the effect of a baseline control system (BCS) on dynamic and fatigue characteristics of modern wind turbines, the simulation results of a 5-MW wind turbine subjected to wind loading without and with considering BCS (No. 1 and No. 2, respectively) were compared. The displacement and moment of tower and blades were compared, and the rainflow counting algorithm was used to analyze the fatigue load expressed in damage equivalent load (DEL). The results indicate that the mean and maximum values of structural dynamic responses in No. 2 have a great reduction with wind speed exceeding the rated speed comparing to No. 1; the 3P (3-times the frequency of rotor speed) of the wind turbine rotor speed will be close to the tower fore-aft (FA) natural frequency with the wind velocity around the cut-in speed in No. 2, which caused larger dynamic responses, number of load cycles, and DELs for the tower compared with No. 1; when wind velocity exceeds the rated wind speed, the BCS caused higher fluctuation of loads, increasing the related DELs. It is concluded that when analyzing the dynamic responses and designing wind turbine tower and blades, taking the BCS into account during analysis is significant.

While a large diameter is critical for maintaining water delivery efficiency in prestressed concrete cylinder pipes (PCCPs), excessive weight fundamentally limits their practical application. This study proposes a weight reduction strategy through material optimization and structural redesign. A full-scale experimental model of 2.8 m inner diameter PCCP was used to validate the finite element analysis method. Comparative numerical models were established to analyze strain/stress distribution in mortar coatings when using ultra-high-performance concrete (UHPC) versus conventional concrete cores. The key findings reveal that UHPC implementation reduces maximum coating strain by 20–30% compared to its conventional concrete counterparts. Multivariate linear regression analysis yielded a predictive formula that explicitly correlates the elastic modulus of the concrete core, core thickness, and mortar stress. This relationship permits the direct optimization of core thickness reductions according to the elastic modulus characteristics of UHPC materials. Verification through two case studies demonstrated a 25–35% core thickness reduction compared to the Chinese standard specifications while maintaining structural integrity, corresponding to an 18–22% total weight reduction. The proposed methodology successfully resolves the inherent weight limitation of conventional PCCPs while achieving equivalent hydraulic capacity, providing an effective pathway for sustainable infrastructure development through material-efficient design.

A simplified analysis method based on three-dimensional finite element analysis is proposed for the dynamic response of pile foundations under the action of vertically propagating SV waves. This method considers the impact of upper structure inertia force and free field deformation on the internal force of the pile separately. The former is considered using the Equivalent Base Shear Method, while the latter is analyzed using a finite element response acceleration method for underground structures. This study selected three seismic waves and their average values as loads to calculate the dynamic response of pile raft foundations. Through trial calculations, the seismic effect reduction coefficient range (0.35–0.4) of the representative values of the horizontal seismic inertia force corresponding to the upper structure was obtained. The error between the peak shear stress of the pile top obtained by the quasi-static method and the time history analysis results was less than 10%. The research results indicate that the proposed simplified analysis method can accurately obtain the peak shear stress and its distribution pattern of the pile body under horizontal seismic action while significantly improving the analysis efficiency. This method has high accuracy and efficiency in conducting seismic design comparison and analysis of multiple foundation schemes.

Uniaxial compression tests were conducted on fly ash-based geopolymer concrete (FAG) with varying alkali-binder ratios (0.25, 0.35, 0.45, 0.55, 0.65) and curing ages (7 d, 28 d) to ascertain its mechanical performance parameters and stress–strain relationship curves. The formation mechanism of FAG multiscale strength is revealed through a systematic process that integrates statistical damage theory with microscopic testing techniques. This process involves the progression of microstructural state and the evolution of mesoscopic damage, providing a comprehensive understanding of the multiscale strength formation process. The results indicate that as the alkali-binder ratio increased, there was an initial rise and subsequent decline in microstructure density. At an alkali-binder ratio of 0.45, the alkaline activator can fully stimulate the fly ash to undergo depolymerization and polycondensation reactions. The result of this process is the formation of a continuous and dense cementitious matrix, thereby achieving the optimal improvement in macroscopic initial mechanical properties. Concurrent microstructural alterations further modify the morphology and path of microcrack initiation and propagation during uniaxial compression, as well as the effective force skeleton adjustment process. The characteristic parameters that are indicative of the evolution of microfracture and yield damage demonstrate regular changes in accordance with the alkali-binder ratio. The joint effect of these two factors determines the evolution characteristics of the macroscopic nonlinear stress–strain behavior of FAG, ultimately resulting in an increasing and then decreasing trend of FAG strength with the increase of alkali-binder ratio, while ductility shows a trend of decreasing first and then increasing. At an equivalent alkali-binder ratio, the porosity of the 7 d sample exhibited a decrease of 1.13% to 17.13%. Conversely, the strength of the 7 d sample increased by 39% to 312%. However, the deformation capacity of the 7 d sample decreased, with a peak strain reduction of 21% to 52% at 28 d. This research achievement has the potential to provide significant theoretical support for the practical engineering promotion and application of FAG.

Coral aggregate seawater concrete (CASC) capitalizes on locally sourced aggregates in marine and reef engineering, enabling in situ material utilization and conferring marked benefits in curbing conventional resource consumption and construction expenditures—a combination that underpins its considerable promise for reef infrastructure development. To date, research efforts have largely been confined to macroscopic mechanical characterization and qualitative microstructural inspections, and quantitative assessments of mesoscopic damage evolution across the full loading-to-failure process remain relatively scarce. In response, to quantitatively characterize the mesoscopic damage evolution mechanism of CASC with different natural aggregates, the present study draws upon statistical damage theory and incorporates uniaxial compressive stress–strain responses from CASC mixtures formulated with four replacement ratios (0%, 33%, 67%, and 100%) of natural coarse and fine aggregates, thereby establishing a statistical damage constitutive model. The model is intentionally structured to decipher the intricate interplay that translates progressive mesoscopic deterioration into the eventual macroscopic mechanical signature, rather than merely describing phenomenological curves. The outcomes reveal favorable concordance between model-generated predictions and experimental measurements. Introducing natural aggregates appreciably modulates the cumulative damage trajectory at the mesoscale; with rising replacement ratios, the macroscopic mechanical performance of CASC is systematically fortified, concomitant with orderly shifts in characteristic damage indices (ε_a, ε_b, ε_h and H). Specifically, when the replacement ratio of natural fine aggregate is fixed at 0%, as the replacement ratio of natural coarse aggregate increases from 0% to 100%, the values of ε_a, ε_b, ε_h, and H increase by 35.8%, 36.9%, 32.2%, and 66.5%, respectively. Additionally, both the fracture damage variable D_R and the integrated transverse strain area derived from digital image correlation (DIC) exhibit monotonic ascending trends as loading advances. Collectively, these contributions offer a theoretical foundation for performance optimization and a deeper mechanistic understanding of damage behavior in CASC.