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The Guadalquivir bridge is a large-scale twin steel truss bridge located in Spain that opened to traffic in 1929. Since the bridge has come into operation for a long time, structural health monitoring (SHM) is strictly necessary to guarantee safety and avoid serious incidents. This paper proposes a novel approach to model updating for the Guadalquivir bridge based on the vibration measurements combined with a hybrid metaheuristic search algorithm. Cuckoo Search (CS) is an evolutionary algorithm derived from global search techniques to look for the best solution. Nevertheless, CS contains some fundamental defects that may reduce its effectiveness in dealing with optimization issues. A main drawback of CS arises in the low convergence level because CS applies fixed values for parameters when looking for the optimal solution. In addition, CS relies a lot on the quality of original populations and does not have the capability to enhance the quality of the next generations. If the position of the original particles is far from the optimal places, it may be challenging to look for the best solution. To remedy the shortcomings of CS, we propose a hybrid metaheuristic algorithm (HGAICS) employing the advantages of both Genetic Algorithm (GA) and Improved Cuckoo Search (ICS) to solve optimization problems. HGAICS contains two outstanding characteristics as follows: (1) GA is employed to create original particles with the best quality based on the capacity of crossover and mutation operators and (2) those particles are then applied to look for the global best derived from the flexible and global search ability of ICS. This paper also presents the application of wireless triaxial sensors (WTSs) taking the place of classical wired systems (CWSs) to the measurements. The use of WTSs increases dramatically the freedom in setting up experimental measurements. The results show that the performance of the proposed hybrid algorithm not only determines uncertain parameters of the Guadalquivir bridge properly, but also is more accurate than GA, CS, and improved CS (ICS). A MATLAB package of the proposed method (HGAICS) is available via GitHub: https://github.com/HoatranCH/HGAICS.

In an attempt to construct detailed kinetic mechanisms for biodiesel fuels on the fly, high-pressure rate rules for the concerted HO2elimination reaction class were derived using a comprehensive training reaction set of more than 60 reactions involving different alkyl methyl/ethyl ester peroxy radicals (RCOOR′)–OO•. Using the composite electronic structure method CBS-QB3 in combination with classical statistical mechanics and the transition state theory (TST) rate model, high-pressure rate constants for the reactions in the training set as well as thermodynamic properties for the species involved were calculated. The corrections from Eckart tunneling and hindered internal rotation (HIR) treatments were also included in the calculations. The results reveal that the ester group (−COO−) selectively promotes the reaction when compared with the traditional hydrocarbon fuels; thus it is recommended that the seven derived rate rules for the title reaction class (including the thermodynamic data of the species involved in the NASA format) should be used for construction of detailed kinetic mechanisms for real biodiesel molecules.