Search

This paper proposes a test method to evaluate the operability of railway vehicles crossing floating bridges. To inspect the dynamic response of the floating bridge to the railway vehicle, the test setup was separated into wave tank and shake table tests. A scaled-down model representing a unit length of the floating bridge span was manufactured for the wave tank test. Several harmonic waves were artificially created and the displacement at the center above the top surface was measured using an optical position sensor. The response of the floating structure was analyzed to extract the relative amplitude versus the input wave for sway, heave, and roll. The harmonic motions using these responses were simultaneously used as input signals for a six-degree-of-freedom shake table. The scaled-down bogie model ran back and forth repeatedly on the railway placed on the shake table. The acceleration measured from the railway vehicle was analyzed to evaluate the running safety and behavior. All tests were performed without allowing derailment and showed sufficient margin to satisfy the running safety and behavior standards. The proposed test method was successfully conducted and showed a remarkable potential to evaluate the operation of railway vehicles on floating bridges under various wave conditions.

Numerical analyses of the coupled vibrations of vehicle-bridge system and the effects of different types of cable stayed bridges on the coupled vibration responses have been presented in this paper using ANSYS. The bridge model and vehicle model were independently built which have no internal relationship in the ANSYS. The vehicle-bridge coupled vibration relationship was obtained by using the APDL program which subsequently imposed on the vehicle and bridge models during the numerical analysis. The proposed model was validated through a field measurements and literature data. The judging method, possibility, and criterion of the vehicle-bridge resonance (coupled vibrations) of cable stayed bridges (both the floating system and half floating system) under traffic flows were presented. The results indicated that the interval time between vehicles is the main influence factor on the resonance excitation frequency under the condition of equally spaced traffic flows. Compared to other types of cable stayed bridges, the floating bridge system has relatively high possibility to cause vehicle-bridge resonance.

A mathematical model of a ribbon pontoon bridge subjected to moving loads was formulated using the theory of simply supported beams. Two types of moving load models were used, the first a moving-constant-force model and the second a moving-mass model. Using both types of loads, the dynamic behavior of a ribbon pontoon bridge was simulated while subjected to a single moving load and then multiple moving loads. Modeling was done with the Simulink package in MATLAB software. Results indicated that the model is correct. The two types of moving load models made little difference to the response ranges when loads moved on the bridge, but made some difference to the response phases. When loads left, the amplitude of the dynamic responses induced by the moving-constant-force model load were larger than those induced by the moving-mass model. There was a great deal more difference when there were more loads.

For the design and operation of a floating bridge, the understanding of its hydroelastic behavior in waves is of great importance. This paper investigated the hydroelastic performances of a ribbon bridge under wave action. A brief introduction on the estimation of dynamic responses of the floating bridge and the comparisons between the experiments and estimation were presented. Based on the 3D hydroelasticity theory, the hydroelastic behavior of the ribbon bridge modeled by finite element method (FEM) was analyzed by employing the mode superposition method. And the relevant comparisons between the numerical results and experimental data obtained from one tenth scale elastic model test in the ocean basin were made. It is found that the present method is applicable and adaptable for predicting the hydroelastic response of the floating bridge in waves.

There are two types of floating bridge such as discrete-pontoon floating bridges and continuous-pontoon floating bridges. Analytical models of both floating bridges subjected by moving loads are presented to study the dynamic responses with hydrodynamic influence coefficients for different water depths. The beam theory and potential theory are introduced to produce the models. The hydrodynamic coefficients and dynamic responses of bridges are evaluated by the boundary element method and by the Galerkin method of weighted residuals, respectively. Considering causal relationship between the frequencies of the oscillation of floating bridges and the added mass coefficients, an iteration method is introduced to compute hydrodynamic frequencies. The results indicate that water depth has little influence upon the dynamic responses of both types of floating bridges, so that the effect of water depth can be neglected during the course of designing floating bridges.

The paper briefly outlines current design philosophies for floating bridges, with special reference to aspects that are deemed to be of interest in the context of very large floating structures. Since the design of submerged floating tunnels is done by people in the same milieu and deals with many of the same problems as in the design of floating bridges, while being in some respects more critical, some of the design philosophy of that subject is also included. The design philosophy and methodology for floating and submerged tunnel bridges draws heavily on Norwegian experiences in two large fields: offshore structures and conventional bridges.

1. The experience here described confirmed the possibility of damming large rivers, without constructing embankments, at hydraulic developments, by placing fine-grained sands by hydraulic dredges. This method of damming river channels is especially convenient if in the project region the rock and rubble material are obtained from quarries located at great distances. 2. The method of damming river channels without using embankments permits closing off a narrow passage, within a short period, by constructing a hydraulic-fill dam by means of suction dredges, without employing floating cranes, pontoon bridges, or other auxiliary equipment. 3. When damming a river channel without constructing embankments, a discharge channel with a small drop should be constructed and a sufficient volume of sand capable of being adequately handled by suction dredges should be supplied. 4. For the construction of river-channel earth dams with very wide bases (and gentle slopes on the downstream side), the method of damming the channel without constructing embankments by placing local soils can save large volumes of rock and rubble. 5. The damming of the Dnepr River at the site of the Kanevsk hydroelectric plant permitted saving 54,000 m3 of rock and 17,000 m3 of rubble; the total economy resulting from the damming of this river without constructing an embankment was 750,000 rubles.

1. Bees were trained to a feeding station, where they obtained a 2-mol sucrose solution. The course of flight led across water and covered a distance of 247 m. The speed of the bees and their path of flight were observed. 2. When the water surface was mirror smooth, a great number of bees plunged into the water. They continually lost altitude until they crashed headlong into the water, wich thereby flipped them onto their backs. We were unable to observe this phenomenon when the water was rippled or, during smooth water, when the course was marked with a bridge of floating boards. 3. The bees always flew slower and lower over rippled water then over solid land or the floating bridge of boards. We measured without wind a flight-speed over water of 6.34 m/s (43 observations), over the floating bridge a flight-speed of 7.93 m/s (11 observations). The difference is significant. 4. The bees compensated for the velocity of the wind when flying over rippled water as well as over the bridge, so that their air-speed was greater when they were flying against the wind and less when they were flying with the wind. 5. The flight across water was disturbed to a great extent by crosswinds. The bees could maintain the correct angle to the cross-wind only near the banks. When they were farther than approximately 20 meters from the bank, they drifted in the wind. Even the presence of the floating bridge did not help them to hold the correct angle to the wind. The bees were driven across the bridge and followed it in a garland-like track on the lee-side. 6. A bee, wich was forced to make a detour to the feeding station did not return by the same route, but chose instead the most direct path to the hive. 7. The reasons for a bee flying slowly when close to the surface of the water are discussed.

1. During the years of the first 5-year plan a hydraulic theory of damming channels of large rivers by dumping stone and blocks into the stream was developed in our country. The theory of damming was utilized and was well confirmed in hydrotechnical practice of erection of dams and of coffer dams. 2. On this basis the flood plain location of Upper Volga and of other hydrocenters on plain rivers was worked out in the pre war period. The channels of these rivers were then dammed up by frontal fills with high hydraulic and production indices. 3. The frontal method of damming with the use of floating bridges and automotive transport of fill material rock, outsize blocks, massifs, and frames found wide application in postwar years. With this method important dammings were sucdessfully and dependably accomplished on erodible river channels of the Svir', Dnepr, and Volga (in several sections) in the construction of a number of the largest hydroelectric stations. Simultaneously the theory of damming channels with the frontal, pioneer and combined methods was further refined and developed. 4. The last decade is characterized by the mass application of the pioneer method of damming rocky channels on high planning and production levels. Directed explosions, seepage through the fills and silting with sand have also been utilized. At the present time, new ways are being worked our for further technical-economic improvement of damming of river channels of our country which are based on hydraulic theory and practice.

1. When performing hydraulic engineering surveys, surveys of bridge sites, constructing floating bridges, and determining the main hydrologic characteristics it is recommended to use G. V. Zheleznyakov's equation (4). 2. Equation (4) gives satisfactory results using data of full-scale and laboratory investigations. 3. The deviation of the measured and calculated values is related to errors when measuring the main characteristics of the flow by instruments.