Advanced Materials and Techniques for Structural Monitoring, Analysis and Control

It is reported that the inclined pile could be either beneficial or detrimental for the abutment they support in the condition of liquefaction – induced lateral displacement. To clarify the effect of inclined pile on seismic response of bridge abutments undergoing liquefaction – induced lateral displacement, numerical analyses were carried out on the damaged abutment that was supported by inclined piles and that was displaced riverwards 100 mm ~ 150 mm due to soil liquefaction during 2011 Great East Japan earthquake. Accordingly, a fully coupled dynamic effective stress finite element model was developed for the soil – pile – superstructure system. It was found that the shear failure of the bridge abutment was initialized from the inclined piles and then followed by the middle vertical pile. Moreover, the earthquake – induced liquefaction caused substantial lateral displacement of soils around the piles and thus dominated the backward rotation of the abutments supported by inclined piles. Additionally, the exclusion of the deck pinning effect may lead to a marked increase in the lateral displacement and rotation of abutments. If the abutment were supported by vertical piles, a much larger lateral displacement was expected and the promotion of the earth pressure behind the abutment was the main cause of the forward rotation of the piled abutment.

Single piles are normally used to support the transmission tower in mountain areas. Uplift capacity of piles is a key factor in the engineering design to increase the stability of transmission tower foundation. This study numerically investigated the uplift capacity of single straight and belled piles in the sloping ground which consisted of clay layer underlain by medium weathered sandstone. A nonlinear 3D finite element model was proposed to describe the uplift behavior of single piles and was calibrated against a field test on single piles subjected to uplift loading. A parametric study was conducted to investigate the effect of the slope angle (θ) on the uplift behavior of single piles. The uplift capacity decreased as the θ increased for either straight piles or belled piles. Moreover, the range of the equivalent plastic strain was greatest for single piles in the level ground. For piles in the sloping ground, the range of equivalent plastic strain was wider at the position of the downstream slope than that at the position of the upstream slope when the uplift load of single piles reached the maximum. As the expansion angle increased to 30°and 45°, the uplift capacity of belled piles (Ru) was increased by 100% and 180% with respect to that of straight piles, respectively. The increase percentage in the Ru was independent on θ. A practical method was proposed to quantify the slope effect on Ru.

As a light and efficient large-span space structure, beam string structures have been widely used since the 1980s. Among them, cables are the main force-bearing components, their level of tension determines the overall stiffness, performance and structural safety of the beam string structures. Real-time monitoring of the cable force during the construction and service periods is an important and effective measure to ensure the safety of the cable structure. At present, vibration method is widely used in nearly all common engineering practice for cable force identification/monitoring because of its simplicity and efficiency. However, the vibration of the cable segment will be affected by the whole structure, so the cable force-frequency relationship based on the simple single cable model cannot meet the accuracy requirement of cable force identification of the beam string structure. Therefore, in this paper, through finite element simulation and theoretical analysis, a three-stage criterion is proposed to develop the method for obtaining the local modal information of the tensioned cable segment with the influence of the overall structure considered. The new method's performance was compared with the result extracted by the vibration method according to the single-cable model assumption, and the design values of the cable forces. The magnitude of the error in the identification of the tension force of the beam string structure according to the single-cable model was studied to provide a method of corrections, so that the single-cable model assumption can be used to improve the measuring efficiency and ensure the solution accuracy. The numerical results show the effectiveness of the proposed method. The work of this paper provides a new approach for improving the identification accuracy of the vibration method of the complex cable system such as the beam string structure, and is a useful discussion on the vibration method of the complex cable system.