Computational models are increasingly being used for the dynamic analysis of structures with nonlinear or uncertain behavior, such as cables in stayed bridges, which nowadays are progressively more used as an alternative for long span and slim structures. In this work, a 3D nonlinear model is described to evaluate the wind dynamic effects on cables for this type of bridges under different scenarios, but also for health monitoring and structural simulation to guarantee performance, evaluate load capacity and estimate life prediction. Fatigue is one of the most relevant and complex failure causes in highway bridges, particularly on the anchorage elements of the cables in stayed bridges; where dampers may be used to minimize the dynamic behavior of the structure and reduce fatigue damage. With this nonlinear simulation model, different damper locations and configurations are evaluated to find the optimal position. A feasibility function is used as a weighting function to take into account the damper's size and design. Analysis is particularly focused for a real cable stayed bridge in the state of Veracruz in México.Although the geometry, the forces and the stresses on cable structures are a challenge, even for structural specialists, the results from this work using the proposed 3D nonlinear model showed to be accurate for the simulation of many different wind scenarios, and damper's location and orientations. Finally, the feasibility weighting function enabled the geometrical limitations to estimate the best location of a damper system to minimize the risk for fatigue failure.

PurposeThe purpose of this paper is to introduce a novel methodology that has the capability of finding symmetrical and nonsymmetrical solutions in complex design domains without additional tuning when changing the design domain. These go from an academic design domain to a practical one.Design/methodology/approachVarious crossovers operators are applied over the same representation using a genetic algorithm for truss structural optimization cases where literature solutions have a tendency to forced symmetry in order to find an optimal design with fewer iterations. Continuous‐discrete representations were cross‐bred by a uniform‐sbx simultaneous crossover, called zygote crossover. Specialized mutations operations are proposed to generate localized changes to improve the solution according with the design domain.FindingsDesign solutions found were lighter and stiffer when comparing against cases reported in current literature and in engineering practice. Also these solutions were found in fewer iterations.Practical implicationsThe cases solved herein are complex and are a challenge for any optimization routine however practical design limitations are observed in the sense of out plane stability. Further comparisons cases are required in order to generate a less adjusted design, this is because the greenhouse solution had to be stiffened with out of plane bars to give it enough lateral stability.Originality/valueContinuous‐discrete representations were cross‐bred by a uniform‐sbx simultaneous crossover, called natural crossover. Specialized mutations operations are proposed to generate localized changes to improve the solution according with the design domain. This scheme along with a less restrictive environment allows a wider exploration of search space.

After an extensive analysis, the Río Papaloapan Bridge in the state of Veracruz, Mexico, was scheduled for maintenance to replace the upper anchorage element of 20 cables that were identified as structurally deficient. For this rehabilitation, an extensive monitoring was implemented to ensure the integrity of the bridge. As a result, abnormal vibration levels were detected in one cable (cable 9 in semi-harp 1), particularly for winds over 50 km/h. To determine the origin of this behavior, additional vibration measurements were implemented to evaluate the dynamic vibrations of the different elements involved.Comparison of the frequency spectrum of different cables with same characteristics and tensions, it was found that the abnormal cable had high vibration levels within the range of 10 to 20 Hz. At the same time, the frequency spectrum for their corresponding upper anchorage of the cable also showed significant differences for the same range of frequencies and higher levels were detected for the same atypical cable in the semi-harp plane (xy plane).Analysis from the vibration data concluded that the tension of the cable was within specifications and the abnormal behavior was not due to distension. Simulation studies confirmed that reduction in the structural stiffness for the anchorage element induced high vibration levels in the range within 20 Hz and the dynamic coupling with the higher vibration modes of the cable was the most probable cause for the extensive vibration in the cable. Also, simulation analysis showed that a damping system could minimize significantly the vibration levels between 8 and 25 Hz.The foregoing gave us the opportunity to conclude that the cable # 9 o semi-harp 1, is under an abnormal conditions due to a dynamic vibration coupling to its upper anchorage element and the higher vibration in the xy plane in this anchorage element was most probably to stiffness reduction. Based on the previous, monitoring and detailed inspection of the anchorage element was recommended, and at the same time, consideration of a damping system is highly recommended to reduce vibration damage.

The dynamic analysis using computational models is an important tool to simulate the dynamic of structures that have specific uncertain behavior like the cable stayed bridges which nowadays is an alternative to solve long span bridges with a slim structure. In this work we developed a 3D non linear model of a cable in order to evaluate the wind effect on the Papaloapan cable stayed bridge located on Veracruz Mexico, under different scenarios. The health of the structure is an important factor to analyze and there are many different fail causes, one of them is the fatigue fall that is relevant in the anchorage elements of the cable stayed bridges. It is possible to modify the behavior of the structure using dampers to minimize that effect. The geometry and all the forces and stress on the structures are a challenge also for the specialists of the structures, in this work the developed methodology resulted very successful to analyze the behavior of a cable on a cable stayed bridge using damping.