Experimental Study On The Nantie Bridge By Dynamic And Static Load

As an important part of railway and highway, bridge is the control engineering of time limit for a project or technology difficulty in the construction, and becomes the fauces of transportation. Dynamic and static loads test on existing bridge are usually needed, in order to checkout whether the structural characteristic and all states of bridge accord with design standards and ensure safe in use. Dynamic and static loads test are of great significance in bridge construction, since they can provide reference for design and offer gist for acceptance of works.The Nantie bridge in this paper is 3 to 6 metre high and 288.36 metre long. It is a double-line bridge and the space between two lines length is 5 to 5.3 metre, with pile foundation and post-tensioned prestressing reinforced beam. The designing load increases from 140t to 220t in the construction, therefore, we increase the number of reinforced bar in site-pour beam, and reinforce the precast beam, in order to ensure safety and avoid waste. Since the construction loads are variable in the reinforcement construction, there are no relate technologies and techniques use for reference, actual measured dates are needed to verify whether the construction quality is satisfied the design demand. To research the dynamic and static loads test on the bridge is the main task of this paper.In the tests, the static load test includes crack checking, intensity checkout, beam span and the piers shaft deformation, and the dynamic load test includes the natural vibration characteristic of bridge, the dynamic response and displacement of bridge when the automobile traveling or braking. There are 4 grider span and 3 pier shaft selected for the test in the paper.Based on plenty of basic dates, the load test scheme is set down, and it is introduced that the test apparatus, the disposing of strain point and deflection point, the loading scheme, the controlling condition of stop load on static load test, and the test scheme of natural vibration characteristic measurement and the dynamic response when the automobile traveling or braking on dynamic load test.Based on actual measured dates, it is calculated that the test load efficiency, the deflection and moment of the beam, and it is tested that the positive stress of section, impact coefficient, natural vibration frequency, and the maximum displacement when braking on the top of piers. Furthermore, the experimental results are compared with theoretical values in the paper.Several conclusions are educed as follows, on the basis of actual measured dates and computational analysis. Firstly, the tension and compressing stresses of concrete on the controlling section and the deflection on the midspan are less than theoretical calculation value. The beam is working on elastic behavior, and the structural strength and stiffness are able to reach the design demand, on the action of 140t. Secondly, the bridge is of excellent quality and on the safe side. The reinforcement is economic and reasonable, and the technique is proper. Thirdly, this test can provide some reference for reinforcement of similar bridge, moreover, it is of great reference value for bridge test.