Yunhe Liu

Developing cascade water energy storage potential is an effective way to enhance hydro–wind–solar flexibility and promote the accommodation of variable renewable energy. This study proposes an optimization method for developing cascade water energy storage potential that considers reservoir dredging, energy storage pump station, and reversible pumped-storage unit. Firstly, the characteristics of various measures for developing water energy storage potential are analyzed, and the operating boundaries and constraints of the cascade water energy storage system are determined. Secondly, considering the volatility of grid-connected large-scale green energy, a short-term multi-objective cascade water energy storage system optimization scheduling model is established with the goal of renewable energy generation and peak-shaving benefits. Finally, a multi-objective fuzzy evaluation method is adopted to quantitatively analyze the impact of different measures on the green energy generation and peak-shaving of the cascade water energy storage system. The cascade hydropower system of Gansu section of the Yellow River basin is selected as a case study, and the results indicate that (1) at matched average daily cascade hydropower output, reservoir 2 dredging reduces the residual-load standard deviation by 27.8% on average, whereas the composite evaluation of generation and peak shaving improves it by 18.0%; (2) deployment of energy storage pump station and reversible pumped-storage unit can improve the overall operational performance of the cascade water energy storage system by 11.3% and 41.0%, respectively; (3) Among the schemes evaluated at the specified capacities, reservoir dredging combined with reversible-unit expansion performs best for the modeled generation and peak-shaving objectives.

To address the challenges encountered during the in situ welding reinforcement process of hollow spherical joints, including complex construction, limited quality control, and low efficiency, this study proposed a prefabricated reinforced hollow spherical joint. A three-dimensional finite element (FE) model was developed and validated against experimental results to quantify the effects of T-rib web width (b), web thickness (t₁), ferrule thickness (t₂), hollow-sphere diameter (D), and bolt pretension (f_v) on the bearing capacity of the prefabricated joint. Based on these analyses, a predictive model was established for the axial compressive bearing capacity of the prefabricated joint. The results showed that, under compression, the reinforcing components primarily provided a supporting role to the hollow sphere, thereby improving the buckling resistance of the prefabricated joint under compression. The reinforcement mechanism primarily relied on friction between the ferrule and the steel stub for load transfer, with the available frictional resistance governed primarily by bolt pretension and the stiffness of the reinforcing components. When sufficient friction existed between the ferrule and the steel tube, increasing the T-rib web width from 0 mm to 80 mm improved the bearing capacity of the prefabricated joint by 33%. At a T-rib flange height (h)-to-web width ratio of h/b = 1.0, the T-rib satisfied the reinforcement requirement through its inherent strength and stiffness. As the hollow-sphere diameter-to-thickness ratio decreased, the incremental gain in bearing capacity diminished. A predictive model was proposed for compressive bearing capacity by accounting for the support provided by the reinforcing components and the effects of hollow-sphere diameter, steel-tube diameter, and the tube-to-sphere diameter ratio. The proposed model predicted the FE results with errors within ±10%, and the findings can provide a practical reference for designing the compressive bearing capacity of prefabricated reinforced hollow spherical joints.

Current dynamic response analyses of arch dams under an oblique incidence of seismic waves have overlooked the effects of canyon contraction deformation. This study investigated the influence of the incident direction and incident angle of seismic waves on the comprehensive displacements, as well as the damage, of arch dams under canyon contraction conditions. When SV waves are incident obliquely along the river direction, the peak displacements of the dam crest and arch crown beam increase with increasing canyon contraction. The displacement of the dam reaches its maximum when the incident angle is 0°, indicating that the SV wave vertical incidence is the most unfavourable incidence mode affecting the displacement. Dam damage cracking is most severe in the case of a canyon contraction of 60 mm and an incidence angle of 0°. The dam damage cracking index in this case increases only by 7.6% compared to a canyon contraction of 0 mm and an angle of incidence of 0°. However, the change in canyon contraction when a seismic wave is incident obliquely can cause serious damage cracking to the dam. When the SV wave is incident obliquely along the cross-river direction, the dam damage cracking index in this case increases by 110% compared to the case where the canyon contraction is 0 mm, and the incidence angle is 0°. Therefore, it is necessary to comprehensively consider the influences of canyon contraction and the oblique incidence of seismic waves in the seismic design and safety review of arch dams.

With the increase in demand for the construction of high proportion new energy base, the power transmission scale of Ultra-High Voltage Direct Current(UHVDC) is growing rapidly, and the characteristics of inter-provincial and inter-regional power transmission are affected by multiple factors, such as the randomness and volatility of new energy in the sending province, the peaks and valleys of the loads, the process of power shortages, and the new time-of use electricity pricing policy in the receiving province. Uncertainty issues are more prominent, and it has changed significantly compared with the traditional UHVDC power transmission methods. It is urgent to study the UHVDC transmission curve planning method in new period. Taking a new energy base in Northwest China as a typical example, a UHVDC power transmission system optimization model is constructed. A UHVDC power transmission curve optimization method that takes into account the power shortages process and the time-of use electricity pricing is proposed, and the Cplex12.6 Solver is used to carry out the 8760 h time series power production simulation. The results show that the obtained 12 curves by the new method can cope with the price-based response demand. Compared with the traditional method, the total cost present value is reduced by RMB 6.10 billion, the power shortage rate is reduced to 0.56%, and the proportion of new energy power is increased to 88.58%. Especially, the power output of pumped storage can track the transmission curve well, and alleviate the requirements for peak regulation flexibility of thermal power units. The power configuration scheme is technically feasible and economical, which verifies the effectiveness of the proposed method. It is suitable for the planning of large-scale UHVDC power transmission schemes. In the meantime, it plays an important role in promoting the level of new energy consumption and helping the low-carbon energy transformation.

Asphalt concrete is widely used in hydraulic structure facilities as an impermeable structure in alpine cold regions, and its dynamic mechanical properties are influenced by the strain rate and specimen size. However, the specimen size has an important effect on mechanical properties; few systematic studies have investigated on the size effect of hydraulic asphalt concrete (HAC) under dynamic or static loading rates. In the present study, four sizes of cylindrical roller-compacted hydraulic asphalt concrete (RCHAC) specimens with heights of 50 mm, 100 mm, 150 mm, and 200 mm were prepared and tested under different loading rates ranging from 10⁻⁵ s⁻¹ to 10⁻² s⁻¹ to investigate the size effects of mechanical properties and failure modes at the temperature of 5 °C. The effect of strain rate on the size effects of the compressive strength and the elastic modulus of RCHAC have also been explored. These tests indicate that when the specimen size increases, the compressive strength and failure degree decrease, while the elastic modulus increases. When the height increases from 50 mm to 200 mm, the compressive strength at different strain rates decreased by more than 50%. Furthermore, the elastic modulus increased by about 211.8% from 0.51 GPa to 1.59 GPa at a strain rate of 10⁻⁵ s⁻¹, and increased by 150% from 5.08 GPa to 12.71 GPa at a strain rate of 10⁻² s⁻¹. As the strain rate increases, the variation trends with the size of the compressive strength, elastic modulus, and failure degree are distinctly intensified. A modified dynamic size effect law, which incorporates both the specimen size and strain rate, is proposed and verified to illustrate the dynamic size effect for the RCHAC under different loading rates.

Compliance checking is a very important step in engineering construction. With the development of information technology, automated compliance checking (ACC) has been paid more and more attention by researchers. One of the most important steps in automated compliance checking is the representation of the code information. However, the relationship constraint is often ignored in the code information and spatial geometric relationship is challenging to represent. The general code representation method does not have enough ability to identify the situation that does not meet the checking conditions because it is easy to cause semantic ambiguity in the checking results. This paper proposes a code representation method, and the building code information is represented in five parts. Relationships in the engineering domain and spatial relationships can be represented in constraint mode; different spatial relationship constraint-checking methods are also explicated. Constraint subject and constraint item can distinguish checking conditions and requirements, which supports semantic checking results. The mapping between the building information ontology and the code concepts is established, which can be used to automatically generate reasoning rules for compliance checking. Finally, the proposed method is verified by the representation of the China Metro Design Code and the application of the actual Metro model.

The safety operation of dams after extreme load is an important frontier research topic in the field of dam engineering. The dam health monitoring provides a reliable data basis for a safety evaluation after extreme loads. This study proposes a novel data-driven fusion model for a dam safety evaluation after extreme load based on monitoring data derived by sensors. First, the relationship between dam environmental quantity and effect quantity is deeply excavated based on bidirectional long short-term memory (BiLSTM) network, which is a deeply improved LSTM model. Aiming at the parameter optimization problem of BiLSTM model, sparrow search algorithm (SSA), which is an advanced optimization algorithm, is integrated. Second, conducting the constructed SSA-BiLSTM model to estimate the change law of dam effect quantity after the extreme load. Finally, the Mann–Whitney U-test theory is introduced to establish the evaluation criterion of the dam safety state. Project case shows that the multiple quantitative prediction accuracy evaluation indicators of the proposed method are significantly superior to the comparison method, with mean absolute percentage error (MAPE) and mean absolute error (MAE) values decreasing by 30.5% and 27.8%, respectively, on average. The proposed model can accurately diagnose the dam safety state after the extreme load compared with on-site inspection results of the engineering department, which provides a new method for dam safety evaluation.

The PBL (Perfobond Leiste) shear connector has the advantages of high bearing capacity and strong constraint ability; however, the traditional PBL shear connector has strong and weak axis problems, and its stiffness is large, resulting in weak deformation ability. To this end, this paper proposes a new type of flange triple-web shear key and obtains the new shear key’s mechanical properties and failure mechanism through the push-out test. The results show that the failure mode of the new shear key is the deformation of the steel plate on the web and the edge of the opening, which has a high bearing capacity, outstanding deformation ability, and good integrity with concrete, showing obvious semi-rigid characteristics. Through numerical analysis, the effects of flange width, web height, and steel plate thickness on the mechanical properties of shear keys are obtained. Based on the fitting analysis method, the calculation formula of shear key bearing capacity is proposed. Finally, the horizontal seismic performance of the shear key is numerically simulated. It is found that the hysteretic curve of the shear key is full and shows good energy dissipation capacity.