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In order to study the influence of reinforcement ratio on the ductile seismic performance of reinforced concrete bridges, the reasonable value of main reinforcement ratio was subdivided in different fortification intensity. Taking reinforced concrete bridge as the research object, the relationship between vertical reinforcement ratio and pier ductility was studied by means of quasi-static model test and finite element numerical analysis, and the quantitative index of multi-stage performance level of typical piers was put forward. And the influence of different reinforcement ratio on the seismic performance of bridges in the harsh environment of chloride erosion was also explored, so as to provide reference suggestions for the range of reinforcement ratio of small and medium-span bridge piers in the earthquake area under chloride erosion environment. The results show that the restoring force model under chloride erosion can better reflect the degradation characteristics of stiffness, and the range of the optimal reinforcement ratio of piers is 1. 11% ~ 2. 72% . When the acceleration is 0. 3g (g is the gravitational acceleration), the damage index of piers can not be satisfied only from the point of view of reinforcement ratio. It is suggested that seismic isolation system should be used for seismic design, such as ductility system, the reinforcement ratio should not be less than 2. 64% . The research results can provide reference for the revision of seismic code for small and medium-span continuous bridges. [ABSTRACT FROM AUTHOR]

Objectives: For the high-reliability and fast cycle slip detection and correction of high-samplingrate global navigation satellite system (GNSS) data, the quality control method for modified geometry-free (MGF) combination is proposed to improve the success rate of phase cycle slip correction. Methods: According to the MGF combination and its error characteristics, the error limits of the MGF method are derived, and the applicability in different navigation satellite systems and the influence of measurement noise on the detecting results are analyzed. Based on the above research, the quality control test of the MGF com ‑ bination is constructed and multi-GNSS experiments are carried out. Results: The experimental results show that the MGF method can be used to detect and correct small cycle slips (such as cycles below 5) rapidly with an accuracy rate of 99.90%. Besides, the quality control test of the MGF combination can identify 100%, 87.57% and 77.42% of the wrong correcting results of GPS, BDS and GLONASS respectively, which reduces the error rate of cycle slip correction to 0.01%.Conclusions: The MGF method is significantly influenced by the noise of phase observation, and the quality control test can identify wrong correcting results effectively, thereby improving the success rate of cycle slip correction. The ability of the quality control test to distinguish wrong detecting results and noise decreases with the increase of noise level. [ABSTRACT FROM AUTHOR]

Fatigue failure is the main problem affecting the safety of structural members. It is of great engineering significance to predict the fatigue life accurately. Based on the damage evolution model with mean stress correction, a numerical method for fatigue life prediction considering both crack initiation and propagation was established combined with finite element method. To verify this method, fatigue tests and numerical simulations of aluminum alloy plates with holes under different stress levels were carried out. The results show that the crack propagation process and the fatigue lives can be effectively predicted by the proposed fatigue numerical method, and the error band of the predicted lives is less than two times. [ABSTRACT FROM AUTHOR]

In the Global Positioning System (GPS), the receiver hardware-induced code and phase biases are important factors affecting precise timing, precise modeling of ionosphere and un-difference ambiguity resolution. In the estimation and modeling of ionospheric electron content, it is generally assumed that the GPS receiver hardware biases are constant amounts, without considering the possible fluctuations and influencing factors. Therefore, to analyze the time-varying characteristics of receiver hardware biases can help improve the accuracy and reliability of the ionospheric electron content estimation. In this paper, the time-varying characteristics of single-epoch and single-day solved GPS receiver differential code bias (DCB) and differential phase bias (DPB) are analyzed, and the correlation between the variation of receiver hard⁃ ware delay and the change of ambient temperature is explored experimentally. The results indicate that re⁃ ceiver DCB will mutate after a restart. And after restarting, the receiver DCB and DPB have a changing process, which takes about 25 min, afterwards they keep stabilized. Also, it’s worth noting that the receiv⁃ er DCB and DPB cannot be stable for a long time. The experimental results show that the change of receiv⁃ er DCB and DPB can reach about 0.8 m and 4 mm in 2-3 h. In addition, the fluctuation of receiver hard⁃ ware delay has a strong correlation with the change of the vicinity temperature. [ABSTRACT FROM AUTHOR]