The increasing use of cable-stayed bridges with steel box girders necessitates more sophisticated design approaches, as the diverse environments of bridge locations place higher demands on the design process. Determining a reasonable finished state is a critical aspect of bridge design, yet the current methods are significantly constrained. A new approach to optimizing the finished state is proposed. This method’s practicality and efficiency are verified through a case study, analyzing how constraints on vertical girder deflection, horizontal pylon displacement, cable forces, and cable force uniformity affect the optimization outcome. The results show that convergence of the mixed-constraint quadratic programming model is achieved within 30 iterations, yielding an optimized finished state that meets the design criteria. The chosen constraint ranges are deemed appropriate, and the optimization method for the construction stage is thus demonstrably feasible and efficient. The multiplier path following optimization algorithm is computationally efficient, exhibiting good convergence and insensitivity to the problem size. Being easy to program, it avoids the arbitrariness of manual cable adjustment, enabling straightforward determination of a reasonable finished state for the cable-stayed bridge with a steel box girder. The vertical displacement of the main girder, the positive and negative bending moments, and the normal stresses at the top and bottom edges, as well as the positive and negative bending moments in the towers, are significantly influenced by the constraint ranges. The horizontal displacement of the pylon roof is significantly affected by the constraint ranges of both the main girder’s vertical displacement and the pylon’s horizontal displacement, while the remaining constraint ranges have a limited impact.

Variable and complex marine environmental loads combined with wave resistance and the insufficient controllability of large caisson structures pose serious challenges during maritime towing. Cable breakage events are common, and improper behaviors could give rise to a variety of accidents. This work explored the dynamic responses of large caisson structures following towing cable breakage under irregular waves combined with harsh currents. Two types of cable breakage, i.e., main bridle and towing bridle breakage, were taken into account. Four potential wave–current combinations were assumed for each situation according to direction. The obtained results show that drag rope breakage could give rise to lateral shifts in the structure, which can become a serious condition when exposed to angled waves. Additionally, following breakage, significant force fluctuations took place in the remaining intact cables. For main cable breakage, both lateral and backward displacements were observed in the structure, which gradually entered a ‘flowing with the wave’ state. Furthermore, under the two abovementioned cable breakage conditions, the structure air gap consistently exceeded 2.3 m, ignoring the possibility of a wave slamming event.

As energy demand continues to grow and environmental issues become more severe, the development and utilization of clean energy natural gas are becoming increasingly important. This paper focuses on the impact mechanism of landslide disasters on pipelines, analyzing how landslide displacement, width, pipeline wall thickness, and internal pressure affect pipeline stress and displacement. The study finds that landslides cause stress concentration at the middle and boundary positions of pipelines. As landslide displacement increases, pipeline stress also increases. For example, when landslide displacement is 1.2 meters, pipeline stress is approximately doubled compared to when the displacement is 0.6 meters. This research aims to explore the impact mechanism of landslide disasters on the stress response of natural gas X80 pipelines, with the goal of providing technical support for their stability and reliability.

Ballast-water management has largely focused on biological invasion, while physicochemical pollutant signals have received less attention in port-level discharge planning. This study develops a hydrodynamically informed, receiving-water-constrained screening approach for ballast-water discharge risks in a bulk-cargo port in northern China. The framework combines three evidence layers: pollutant pressure in ballast water, environmental headroom in receiving waters, and source-to-receptor hydrodynamic exposure derived from conservative-tracer simulations. It was demonstrated using ballast-water samples from ten vessels, monitoring data from 24 receiving-water stations and ten representative release scenarios.,Inorganic nitrogen was the dominant source-pressure signal among the matched indicators. Low-salinity ballast water contained a higher mean inorganic-nitrogen concentration than saline ballast water (0.712 versus 0.336 mg/L). In receiving waters, inorganic nitrogen was also the only matched indicator with depleted environmental headroom, occurring at three stations. However, MIKE21 simulations showed negligible exposure at these stations. The strongest exposure pathways were associated with inner-channel and port-mouth releases reaching stations where inorganic-nitrogen headroom remained positive.,The overlay therefore revealed spatial separation among source pressure, receiving-water capacity constraints and hydrodynamic connectivity. Elevated inorganic-nitrogen pressure, depleted headroom and strong exposure occurred in different parts of the port system, indicating distinct priorities for source monitoring, receiving-water management and release-zone evaluation. The framework provides a practical approach for port environmental management in data-limited coastal regions, supporting targeted monitoring and discharge-area planning where detailed discharge records are unavailable.

A coupled WRF–ROMS–SWAN framework is used to investigate the long-term wave characteristics of the Bohai Sea through a 20-year hindcast from 2002 to 2022. The model results are validated against CMEMS current data, field wave measurements, and CCMP wind products, showing good agreement with the reference datasets. Three spatial interpolation methods are compared for reconstructing the wave time series at discrete locations, and distance-squared weighted interpolation (DSWI) provides the best overall performance for the present dataset. The reconstructed records show clear seasonal and interannual variations in the significant wave height, average wavelength, and spectral peak period. Spatially, larger mean and extreme wave parameters occur mainly in the central and eastern offshore areas, while the enclosed inner bays are generally calmer. Weibull, Gumbel, Pearson Type III, and Exponential distributions are further applied to estimate wave conditions for return periods of 1–100 years. The Exponential distribution gives the highest long-period estimates, whereas the Weibull distribution gives the lowest. Wave roses also show clear differences in prevailing wave directions among stations. The results provide long-term wave information for offshore engineering and marine hazard assessment in the Bohai Sea.