Li G.,Tongji University |
Zhang C.,Tongji University |
Niu C.,Shanghai Municipal Engineering Design Institute Group Co.
Journal of Bridge Engineering | Year: 2013
Abstract External prestressing technology has achieved wide application in bridges. Although previous tests have made great progress in shear behavior of externally prestressed concrete beams, the research mainly focused on simply supported beams. To study the effects of joints and large negative moments on the shear behavior of segmental externally prestressed concrete continuous beams, a series of cantilever beam specimens were designed to simulate the negative moment regions in continuous beams. Then, the crack developing behavior, failure mode behavior, and mechanical behavior of specimens with different shear span to effective depth ratios, joint types, joint locations, and ratios of internal to external tendons were investigated in this experimental study. The test results show that failure cracks of segmental specimens are web shear cracks, whose locations and inclination angles are independent of joints. Eventually, both sides of the specimens move relatively along failure cracks and the specimens fail suddenly. The results also reveal that the deflections of segmental specimens after cracking develop very quickly, and the stress increments of prestressing tendons reach 20-24% of the tensile strength, which are larger than those of monolithic specimens. In addition, the shear strength provided by the concrete effects in regions near the interior supports of continuous beams is lower than that in regions near the supports of simply supported beams, and the contributions of the stirrup and prestressing tendon to the shear strength are 14-21 and 8-18%, respectively, in which the contribution of stirrup is greater than that of simply supported beams. © 2013 American Society of Civil Engineers. Source
Li Y.,Shanghai Municipal Engineering Design Institute Group Co.
Zhongguo Gonglu Xuebao/China Journal of Highway and Transport | Year: 2015
In order to further analyze the proper design parameters for cable clips of suspension bridges with carbon fiber reinforced polymer (CFRP) cables, the Tsai-Hill failure criterion of composite material was firstly introduced, and the formulas for cable moment at the clips was derived through analysis method, based on which calculation method for the clip design of CFRP suspension bridges was proposed. Then, parametric analysis on the mechanical indexes of clips on the CFRP cable was conducted, where the influences of diameter of cable wire, interval between clips, length of clips, tension of bolts, interval between bolts, friction factor between CFRP and steel, and friction factor of CFRP on force performance of cable clip were investigated. The results show that the mechanics behavior of clips can be improved significantly by reducing the cable wire diameter, increasing the clip length, increasing the tension of bolts, reducing the interval between bolts, and enhancing the friction factor between CFRP and steel. The interval between clips should be chosen within a reasonable range, otherwise negative effects could be brought about. ©, 2015, Xi'an Highway University. All right reserved. Source
Li F.-D.,Shanghai Municipal Engineering Design Institute Group Co.
Bridge Construction | Year: 2016
To study the characteristics of the separated and obliquely set steel anchor boxes in pylon of cable-stayed bridge, the structural characteristics of the anchor boxes and the force conditions of the anchorage zone in the pylon were analyzed. Because the anchor boxes were separated and obliquely set, the transverse horizontal component force could not be self-balanced and in comparison to the rigidity of the anchor boxes, the rigidity of the concrete pylon columns increased and at the same time, the pylon columns bore the whole of the transverse horizontal force and much of the longitudinal horizontal force. By way of example of the diamond-shape pylon of a single-pylon cable-stayed bridge, the software ANSYS was used to establish the spatial finite element model for the anchor boxes in the pylon, the influences of the obliquely setting of the anchor boxes on the stress distribution of the anchor boxes and pylon walls as well as the ratios of the horizontal force distribution of the stay cables between the anchor boxes and pylon walls were analyzed. The results of the analysis show that as compared to the integral steel anchor box, the ratios of the horizontal force distribution of the stay cables of the separated and obliquely set steel anchor boxes decrease and the pylon columns bear much of the horizontal component force. The force conditions of the components and shear studs of the anchor boxes are not symmetric, the stress levels are low and are not uniform. © 2016, Wuhan Bridge Research Institute. All right reserved. Source
Wang H.,Shanghai Municipal Engineering Design Institute Group Co.
Yantu Lixue/Rock and Soil Mechanics | Year: 2012
Using numerical simulation by PFC 2D (particle flow code in two dimensions), the group piles effect of pile tip resistance of under-reamed piles on uplift loading is studied. The increase of tip resistance with uplift displacement and the variations of soil displacement around pile tip are observed in the simulation. The differences between single pile (pier) and group piles (piers) in uplift loading are shown and the development of tip resistance with uplift displacement for group piers in different spaces is compared. It is shown that the uplift characteristics are similar for single pile (pier) and group piles (piers) when the normalized uplift displacement s/D is smaller than 0.1. With the development of uplift displacement, the tip resistance of single pile (pier) is larger than that in group piles (piers) and the interaction of soil particles around tip emerges. When the normalized uplift displacement s/D is smaller than 0.5, the tip resistance of central pile (pier) is larger than that of side pile (pier) in the group piles (piers). When the normalized uplift displacement s/D is larger than 0.5, the tip resistance of side pile is larger than that of center pile in the group piles and that is reverse in the group piers, which embodied the effects of side restriction of pile shaft on the mobilization of tip resistance. The characteristics of group piers had obvious difference with single pier only in larger displacement with the increase of pier distance. Source
Lin F.,Shanghai Municipal Engineering Design Institute Group Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2014
The increase of embedded depth of retaining wall, reinforcement of foundation soil and set-up of partition wall between foundation pits and buildings are widely-used techniques to protect the surrounding facilities. The problems of budget and construction period can be possibly reduced by optimization design. Currently, the optimization design of the foundation pits focuses mainly on types of retaining wall and structural members and not on the whole retaining system. Based on a deep foundation pit close to a metro station in operation and a large-diameter water pipe, a 3D finite element model is proposed. The behaviors of soils are assumed to conform to Drucker-Prager model, and three different construction sequences are simulated. Considering the distinct stress states of soils during construction, loading and unloading modulis of each soil type are adopted. The results show that the implementation of the temporary partition wall can be canceled, and the basement floor No.1 and No.2 can be excavated downward simultaneously. The design of retaining system is optimized, and the settlement-sensitive municipal facilities are safe. Source