Papers by Keyword: External Tendon

Abstract: Aiming to Ronggui Bridge (RGB) on Guangzhou-Zhuhai Intercity Rapid Rail Transit (GZIRRT), long term deformation control of long-span pre-stressed concrete continuous rigid frame bridge with ballastless track was studied. Comparing with the non-controlled deformation, extend track laying six months later after bridge construction, reserve 48 post-tensioned cables in middle spans and tension 12 external tendons after tracking laying were all effective in decreasing the long term deformation of RGB with individual application. Taking bridge construction and railway service in consideration, applying the foregoing three measures in combination, deformation of RGB 20 years later after track laying was effectively controlled within 12.8mm in the side spans and 21.9mm in the middle spans, which is less than the deformation limitation of bridges with ballastless track. The combined measure has been adopted in the actual construction of RGB.

Abstract: Based on Miyamoto’s method, the natural frequency of prestressed box girder with corrugated steel webs considering the impact of external tendons was obtained. And the result was modified based on the finite element model. It shows that: the external tendons will reduce the natural frequency of bridge with reduced range of about 3%. Beneficial references were provided to the layout of external tendons in order to avoid the resonance between the box girder with corrugated steel webs and the external tendons.

Abstract: Jiamusi highway prestressed concrete bridge is located in the Jiamusi City within Heilongjiang province in the east north of China. The strengthening and repairing of the bridge structure can be provided an effective and economic solution in appropriate situation. The objective of this study are to monitor the construction process of external prestressing tendons for strengthening of Jiamusi highway prestressed concrete bridge. Monitoring process includes measurement of external prestressing tendons natural frequency, monitoring of tensile forces values of external prestressing tendons, monitoring of development of anchor beams cracks, and monitoring of anchor beam deformation. The results of monitoring process show that the box girder No. 11 has the largest values of proportional coefficient (K) and the maximum value is 327.8. Box girder No. 8 has the largest values of frequency, the maximum value is 3.499. Five levels of tension are used in the application of tensile force in the tension process of external prestressing tendons. These levels are level 1=248.2kN, level 2=496.4kN, level 3=744.6kN, level 4=992.8kN, and level 5=1241kN. The measured tendons elongation values of left box girder No.8 are more than the theoretical values. For left and right box girder No. 9, side external tendons of left box No. 10, and left and right box girder No. 11, the measured values are less than theoretical values of elongation. After tension process, there are no new cracks in the top, web, and bottom of anchor beam and a small number of cracks developed slightly. These cracks are found around ducts of external tendons. The length of cracks rang from 0.03m to 0.5m and width rang from 0.05 mm and 0.25mm. The longitudinal deformation of the interface and top of anchor beam is very small, ranging from 0.001mm to0.115mm, which averaged 0.026mm. The overall state of anchor beams and box girders during strengthening is good.

Abstract: To assess the behavior of concrete beams partially prestressed with external unbonded carbon fiber-reinforced polymer (CFRP) tendons, three specimens prestressed with CFRP tendons and one reference specimen prestressed with external steel tendons were tested to failure under third point loading. It was found that the load-deflection curve of all specimens exhibited three stages, namely, elastic, cracked-elastic and plastic. The transition from the elastic to the cracked-elastic stage was caused by the development of cracks at the bottom of the beam, while the transition from the cracked-elastic to the plastic stage was caused by yielding of the non-prestressed steel. For beams prestressed with external CFRP tendons and that with external steel tendons, the relationships between the stress increment in external tendons and the mid-span deflection of specimens were linear or approximately linear. Although CFRP materials are brittle in nature and behave linearly elastically until failure, proper combination of external CFRP prestress tendons with internal steel reinforcing bars can impart ductility to the beams.

Abstract: The purpose of present paper is to study the flexural behaviors of concrete T-beams prestressed with external carbon fiber reinforced polymer(CFRP) tendons. Tests were carried out on 5 beams under four-point load, of which four beams were reinforced with hybrid both external CFRP tendons and internal steel rebars and another one only reinforced with internal steel rebars. Such parameters as the different initial loading states at external CFRP tendon jacking and different jacking stress in tendon were considered in experiment. A program was developed to predict the behaviors of those beams prestressed with externally prestressed tendons and the parametric study was conducted using the program. The predicted results from the program were in good agreement with the test results. Such parameters as jacking stress, elastic modulus of external tendons, configuration of deviators and ratio of span to effective depth of beam were chosen as primary analytical factors for the study on the flexural behaviors of beams prestressed with external tendons. The initial loading state on the beam before tendon jacking has no significant influence on the ultimate loading capacity and deflection.