In order to examine the effect of reinforced ring plate on seismic performance of concrete filled steel tubular (CFST) T-joints with spherical-cap gap in CFST chords, a series of hysteresis tests were carried out on 12 CFST T-joints with the chord under constant tensile load and the brace subjected to cyclic axial loading. The performance of CFST T-joints was experimentally investigated in terms of the failure mode, load-displacement hysteresis relationship and strain development. The effects of chord-to-brace diameter ratio and diameter-to-thickness ratio of the CFST chord on the hysteretic behaviour of joint specimens were compared and analyzed. It was found from the test results that the reinforced ring plate could restrain the development of plastic deformation of the CFST chord with spherical-cap gap, and counteract the unfavorable influence on the bearing capacity, stiffness, ductility and energy dissipation capacity of the CFST T-joints caused by the gap. The bearing capacity of the reinforced joint specimen was more than 12.6% higher than that of the specimen with gap but without reinforcement, and it was even more than 6.5% higher than that of the specimen without gap. It was evident that with reasonable design of the reinforced ring plate, the unfavorable influence on the seismic performance of CFST T-joints induced by spherical-cap gap might be fully compensated.
Heterogeneous multicore clusters are becoming more popular for high-performance computing due to their great computing power and cost-to-performance effectiveness nowadays. Nevertheless, parallel efficiency degradation is still a problem in large-scale structural analysis based on heterogeneous multicore clusters. To solve it, a hybrid hierarchical parallel algorithm (HHPA) is proposed on the basis of the conventional domain decomposition algorithm (CDDA) and the parallel sparse solver. In this new algorithm, a three-layer parallelization of the computational procedure is introduced to enable the separation of the communication of inter-nodes, heterogeneous-core-groups (HCGs) and inside-heterogeneous-core-groups through mapping computing tasks to various hardware layers. This approach can not only achieve load balancing at different layers efficiently but can also improve the communication rate significantly through hierarchical communication. Additionally, the proposed hybrid parallel approach in this article can reduce the interface equation size and further reduce the solution time, which can make up for the shortcoming of growing communication overheads with the increase of interface equation size when employing CDDA. Moreover, the distributed sparse storage of a large amount of data is introduced to improve memory access. By solving benchmark instances on the Shenwei-Taihuzhiguang supercomputer, the results show that the proposed method can obtain higher speedup and parallel efficiency compared with CDDA and more superior extensibility of parallel partition compared with the two-level parallel computing algorithm (TPCA).
To optimize the empirical constants in dynamic stall model and improve the prediction accuracy of airfoil aerodynamic performance when dynamic stall occurs,the influence of pressure lag and boundary layer lag time constant on the dynamic stall performance is explored,using the B-L dynamic stall model and the wind tunnel experiment in the Key Laboratory of Wind and Solar Energy Utilization Technology of the Ministry of Education at Inner Mongolia University of Technology.The main conclusions are as follows.The time constants of pressure lag and boundary layer lag have great influence on the dynamic lift coefficient,which is related to the average angle of attack.When the average angle of attack is relatively small and the flow is between the attached flow and the separated flow,appropriately reducing the time constant can make the calculated results of the dynamic stall model closer to the experimental values.When the average angle of attack is relatively large and the flow is in separated flow or completely separated flow,the time constant value can be appropriately increased.The influence of pressure lag and boundary layer lag time constant on the dynamic drag coefficient is not significant.The dynamic lift coefficient only decreases with the increase of boundary layer lag time constant in the completely separated flow process where the angle of attack decreases gradually.
Fragility functions for structural members play an important role in the FEMA P-58 methodology for the seismic performance assessment of structures. In this study, fragility functions were developed for aged reinforced columns with corroded reinforcing bars. To this end, an experimental database containing 120 specimens subjected to repeated cyclic loads was compiled from 20 previous studies. The experimental specimens were categorized into three groups: no corrosion damage (NCD), low corrosion damage (LCD), and high corrosion damage (HCD). These damage states were identified by experimental hysteretic responses in terms of the drift angle, which are linked to common methods of repair, including structural repair, structural enhancement, and component replacement. The obtained drift angles were used to fit the log-normal fragility functions of the NCD, LCD, and HCD columns. The effect of reinforcement corrosion was examined by comparing the fragility functions of uncorroded and corroded columns. According to the principles suggested by FEMA P-58, the developed fragility functions were mostly judged to have a high level of quality. The fragility medians of the corroded columns showed a clear decreasing trend along with an increasing degree of corrosion damage. However, the corrosion of the reinforcing bars had a limited effect on the fragility dispersion. The maximum differences in the exceedance probability were calculated by comparing the fragility curves for the LCD and NCD columns, which were greater than 20 % for all concerned damage states. For the HCD columns, the corrosion of the reinforcing bars led to the maximum difference in the exceedance probability, even beyond 50 %, compared to the results for the NCD columns. The above results reveal the significant effect of the corrosion of the reinforcing bars. The specific fragility functions developed for the corroded reinforced concrete columns will facilitate the seismic loss and resilience assessment of aging reinforced concrete building structures.
A series of undrained cyclic shear tests was carried out on saturated coral sands, with different initial physical states, as they were subjected to rotations of 90 degrees in the paths of cyclic stress with various initial orientations under isotropic conditions. An important finding is that the cumulative dissipated energy required for liquefaction (W-s) was significantly affected by their fines content (FC), relative density (D-r), and effective stress of consolidation (p ' 0), but was independent of the conditions of cyclic loading. W-s increased significantly with the increase in p ' 0. When FC was less than the threshold fines content, W-s increased with FC and decreased with an increase in D-r. The equivalent intergranular void ratio (e*) was introduced to reflect the effects of FC, physical states of the particles, and inter-particle contact on the physical properties of coral sand. The results revealed a unique relationship between e* and W-s at p ' 0 = 100 kPa. Furthermore, the unified model of the relation between the normalized cumulative dissipated energy and the ratio of excess pore water pressure (EPWP) followed an arc-tangent function. This model can be used to characterize the generation of EPWP with the cumulative dissipated energy of fine-grained sand under isotropic consolidation conditions.
