| Flood disaster is one of the most serious natural disasters in China or other countries. According to the United States' statistics in 1970, flood disaster accounted for one-third of nine natural disasters' losses. On the basis of statistics by UN, flood and water-logging disasters' losses accounted for 45% of the whole natural disasters' in the world, being the biggest scale and the most serious. Moreover, the losses of natural disasters are increasing constantly. Therefore, 155 Member States of UN cosponsored a UN Resolution which declared 1999-2000 as the "International Decade For Natural Disaster Reduction" in 1989. Flood disasters were very serious in Chinese history, and there is a common saying that "To control flood disasters means to lead the nation". Flood disasters' losses in China approximately accounted for 40% of all the natural disasters'. Considering Seven Big Rivers which are the Yangtze River, the Yellow River, the Pearl River, the Huai River, the Hai River, the Liao River and the Songhua River, there is about 50% of the population and 70% of the assets concentrating in flood plains. Once flood overflows the dike, losses must be very serious. For example, the direct economic losses reached 48.4 billion Yuan those of Jiangsu and Anhui provinces caused by flood disasters of the Yangtze River and the Huai River in 1991, and approached to 50.1 billion Yuan investments for the Three Gorges Dam Project, however, there was no way to calculate the indirect economic losses and social impacts. In 1994, 1995, 1998 and 2003, there were frequent flood disasters in the South, the Central and the Northeast China. Flood disasters occurred year by year. The Communist Party of China and the Chinese government paid more attention to controlling flood and preventing disasters. There have 8.4 ×104 reservoirs been built, and aggregate storage capacity is about 460 billion m3. More than 100 detention flood zones and diversion basinswhich can diverge and store 120 billion m3, 2.6 × 104 sluices and 2.1 × 105 km dikes had been built, and instituted a basic flood control system to play their roles in flood control gradually. However, many detention flood zones were occupied by people year by year with the rapid development of national economy and construction in recent years so that more frequent flood disasters and more serious losses have kept in increasing. It is the most direct and basic flood control measure that is to build dikes in China, but their safety problems are also most. Most of flood disasters are caused by the failure of dikes.There is more population and concentrated wealth in cities, which are also centers of state and regions in economy, science and technology, culture and politics. Most cities in our country are located along mountains and rivers, near rivers, lakes or seas, so it is hard for these cities to avoid flood threat. Flood and water-logging disasters, typhoons and storm tides are natural disasters that threaten many cities. It is the key to protect cities from flood for basin flood control. With the rapid economic development and population growth, the amount and scale of cities is enlarged continuously, and flood control task will get more and more hard. It is necessary for many cities to survive and develop that urban flood control projects ensure the cities safe. The cities have developed rapidly since the reform and opening up policy being carried out in China. Buildings and gardens along both banks of rivers have been constructed to a certain scale, and beautiful scenery of the cities has been made, which are good places for the citizens and tourists to amuse and relax. Therefore, construction of flood control projects should not only satisfy urban developing plans, but also comply with appreciating the scenery both on the rivers and banks, closing to water for the citizens and tourists. It must destroy existing scenery, occupy the limited precious land, and have high costs to enhance dikes and raise flood control standards by the traditional methods building dike with earth and constructing reinforcement concrete or mason flood control wall, and it is very hard to solve the conflicts among flood control, urban construction plan, scenery appreciating on the rivers and banks, and closing to water requirements.The main contents in this paper include combining flood control requirements with existing flood control situation to study a new type of urban dike for the city flood control, and includes making waves in the 2-D numerical flume and analysis of numerical wavesfeature, dynamic analysis of the steel cantilever sheet's response to wave and wind load, and use the analysis software of FLUENT and ANSYS to study the numerical simulation with wave factors and wave load, experimental study of the ratio in 1:1 between static test and installation test on board performances of composite flood control wall with fabricated steel sheet. The main results are as follows:1. City Flood Control is a new branch of water conservancy engineering with social economic development at home and abroad. The design of city rivers' scenery involves many comprehensive subjects of which Hydraulics, Hydro-ecosystem, Landscape Design, Aesthetics, and Environmental Psychics. This paper carried out advanced research on the design of urban river landscape in combination with the Harbin flood control.2. It must destroy existing scenery, occupy the, limited precious land, and have high costs to enhance the dike and raise the flood control standard by the traditional methods building dike with earth and constructing reinforcement concrete or mason flood control wall, and it is very hard to solve the conflict between flood control and urban construction. Studied flood control of large and medium size cities and Harbin City, the author created a new ideal type of flood control dike with composite flood control wall with fabricated steel sheet, which is suitable for enhancing and raising urban dikes and raising further flood control standards. The type is especially suitable for the dike sections needing good scenery. It can not only meet the safety of flood control and the city development planning, but also satisfy people appreciate the scenery both on rivers and banks, and closing to water for the citizens and tourists.3. The study on interaction between wave and hydraulic structure basically depends on physical model test to solve problems at present in our country, and the regular software of CFD cannot provide the conditions of wave to solve wave problems. In the paper, the author founded the analysis and research theory of fluid-solid coupled system to use the concept of system which considering fluid and solid as a uniform system. With the numerical simulation method, using the software of ANSYS and FLUENT to analyze and calculate the dynamic response of the steel cantilever sheet to wave and wind load firstly. A new method was brought forward by using the step-by-step iterative process to solve the fluid—solid coupledproblems with complex structure, i.e. fixed the boundary position of fluid and solid firstly, then to take the movement speed of solid boundary as the boundary condition of the coupled surface to conduct the simulation calculation of fluid area, and then, taking the calculated result as the load on the solid to do the dynamic finite element calculation. Thus, we can obtain the displacement and speed of the solid boundary at this time. The new boundary place and speeds may be used to calculate the next interval of fluid area, the time duration of fluid and solid coupled system movement and its load distribution will be obtained through the iterative calculation in the end.4. On the basis of the wave generator theory, this paper firstly put forward a method using the software of FLUENT, simulating the physical wave generation in the water tank on computer to research the relationship between the wave generator plate movement rules and parameters of the wave, so as to determine the special wave environment effectively to calculate the space distribution and time duration of the wave load acting on the cantilever steel sheet. This method saved more time and labors and costs less than physical model test.The results of calculation showed that the spot of maximum instantaneous wave load occurred on 0.427m high from the bottom of steel sheets, and the maximum intensity of pressure was 2.76×104Pa under 100-year flood. During a whole wave periodicity, the steel sheets were under pressure during partial time, and there were two peak values which the front peak value was bigger than the back one during the pressure period, therefore, it showed that the steel sheet's pressure belonged to impact load.5. The calculation results of simulating mode analysis showed that the natural frequency value of steel sheet together with the accessory water body reduced 70%, and the water level in front of the sheet continued changing, so the quantity of the accessory water body also continued changing, moreover, the natural frequency of the steel sheet continued changing. The maximum natural frequency value was that of the dry simulating mode when the quantity of accessory water body was 0. The minimum natural frequency value was that of steel sheet met the 300-year flood when the quantity of the accessory water body was the maximum. When the 2 m high steel sheet met below 300-year flood, its natural frequency was between 7.7 Hz to 21.15 Hz; and when 2.6 m high steel sheet met below 300-year flood,its natural frequency was between 6.82 Hz to 24.13 Hz.6. The software of ANSYS was used to found and compared the solid model with board model when analyzing the dynamic response of the sheet in the paper, respectively. Both models could satisfy the basic requirements of the analysis fully, and their calculated results were very closed. The displacement of the board model was more than the actual, but the thickness factors needed to be considered in dividing into the net of solid model unit, it must be divided into very small, not only to waste more computer resources and calculation time, but also there would be more unfavorable factors between the compatibility and coordination and the units. Therefore, the board model was used in calculations and drawing a conclusion that board model was more suitable for actual project welded structures by the steel sheet.7. The paper used the software of ANSYS and FLUENT to analyze and calculate the cantilever steel sheet's dynamic response to the wave and wind load. Due to the small deformation and displacement of the steel sheet, there was no effect on the wave load basically. Therefore, the coupling action on the steel sheet boundary might be omitted for the numerical simulation of wave load, the analysis and calculation of the finite elements could take the time graph of the wave load as the external load, using the step-by-step iterative method to find the answer in several time intervals.The results of calculation showed that the spot of maximum amplitude with wave live load occurred on the top edge of the steel sheet. At the same level, maximum amplitudes of every spot were almost equal. There were two situations with 300-year flood and 100-year flood wave live load respectively for the steel sheets with the height of 2.6m and 2.0m, in which the steel sheet with the height of 2.6m responded very strongly under 300-year flood wave live load and the maximum amplitude was 0.55mm. The frequencies of wave load, which were 0.344Hz of 300-year flood and 0.283Hz of 100-year flood, is largely different from the natural frequency of steel sheets which were 19.1 Hz of 2.6m high sheet and 19.24Hz of 2.0m high sheet, and vibration response would be weak and there was not any resonant vibration phenomenon during a periodicity.8. The physical model test results showed that deformation played a controlling role when the upstream face boards of two kinds of sheets were acted by the load increasedgradually, and neither strain nor stress was big, being within the scope of elasticity. At the same time, it was found that the deformation increases gradually when the load exceeded 300-year flood, but two-ladder effect caused by the deformation was not large. That meant the ultimate bearing capability might be regarded as the safe reservation of the structure due to the unobvious action of the geometric non-linearity. The installation test of two steel sheets on the spot certified that it was convenient for this kind of composite flood control wall.9 When the 2m high steel sheet was acted by 100-year flood, the actual displacement value was 3.419 mm of the sheet top and the ratio between the displacement and the height of the sheet was 1/585 in the physical static test, but the displacement value was 3.1 mm of the sheet top and the ratio between the displacement and the height of the sheet was 1/645 by the calculation in static finite element analysis, and the difference was 0.319 mm. The displacement of static finite element analysis was less 9.33% than that of the physical static test. However, the response laws of stress, strain and displacement were the same by the two methods for fabricated cantilever sheet under the same wave loads. The deflection values by the two methods were also less than 1/350 that of the specification allowable value, and the rigidities met the requirement of the specification.As mentioned above, this composite flood control wall with assembled steel sheet is a new kind of ideal dike type, which is helpful for the urban flood control dikes to be heightened and raise the further flood control standards, especially suit the dike sections at the city landscape places. It could satisfy not only the requirements of flood control and municipal development planning, but also comply with appreciating the scenery both on the rivers and banks and closing to water for the citizens and tourists. The results of the numerical static analysis, dynamic response analysis and the overall model static test in the ratio 1:1 indicate that its working function is dependable. The overall model installation test on the spot certifies that it is convenient to install and may be applied widely at home and abroad.
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