Дисертації з теми "Foundation scour"
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1
Kermani, Behnoud. "Application of P-wave Reflection Imaging to Unknown Bridge Foundations and Comparison with Other Non-Destructive Test Methods." Master's thesis, Temple University Libraries, 2013. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/234113.
Повний текст джерелаАнотація:
Civil EngineeringM.S.C.E.
Proper design of bridge structures requires an appreciation for the possible failure mechanisms that can develop over the lifetime of the bridge, many of which are related to natural hazards. For example, scour is one of the most common causes of bridge failures. Scour occurs due to the erosion of soil and sediment within a channel with flowing water. During a flood event, the extent of scour can be so great that it can destabilize an existing bridge structure. In order to evaluate the scour potential of a bridge, it is necessary to have information regarding the substructure, particularly the bridge foundations. However, as of 2011 there are more than 40,000 bridges across United States with unknown foundations. Generally for these bridges there are no design or as-built plans available to show the type, depth, geometry, or materials incorporated into the foundations. Several non-destructive testing (NDT) methods have been developed to evaluate these unknown foundations. The primary objective of this research is to identify the most current and widely used NDT methods for determining the embedment depth of unknown bridge foundations and to compare these methods to an ultrasonic P-wave reflection imaging system. The ultrasonic P-wave reflection system has tremendous potential to provide more information and address several short-comings of other NDT methods. A laboratory study was initiated to explore various aspects related to the P-wave system performance, in order to characterize the limitations of the system in evaluation of unknown foundations prior to deployment in field studies. Moreover, field testing was performed using the P-wave system and a number of the current NDT methods at two selected bridge foundations to allow comparison between the results.
Temple University--Theses
2
Tavouktsoglou, N. S. "Scour and scour protection around offshore gravity based foundations." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10044922/.
Повний текст джерелаАнотація:
The prediction of seabed scour around offshore gravity based foundations with complex geometries is currently a significant barrier to optimising and providing cost effective foundation designs. A significant aspect that has the potential to reduce the uncertainty and costs related to the design of these foundations is the understanding of the effect the structural geometry of the foundation has on scour. This thesis focuses on an experimental investigation of the scour and scour protection around complex structure geometries. The first part of this research considers scour under clear water conditions. During this study different foundation geometries were subjected to a range of different hydrodynamic forcings which enabled a better understanding of the scour process for these foundations. The second part of the research encompasses the design and execution of a series of experiments which investigated stability of the scour protection around such structures. The structures were tested against different combinations of wave and current conditions to determine the bed shear stress required to initiate sediment motion around each structure. This research has led to a number of novel results. The experimental investigation on scour around complex geometries showed that the scour depth around cylindrical structures (with both uniform and complex cross-sections) is linked to the depth averaged pressure gradient. Following a dimensional analysis, the controlling parameters were found to be the depth averaged Euler number, pile Reynolds number, Froude number, sediment mobility number and the non-dimensional flow depth. Based on this finding a new scour prediction equation was developed which shows good agreement with experimental and prototype scour measurements. The scour protection tests indicated that under wave dominated conditions the amplification of the bed shear stress around these structures does not exceed the value of 2. In the case of current dominated flow conditions the amplification of the bed shear stress is a function of the structure type and the Keulegan–Carpenter number. The results of these experiments were used to develop a “Shields type” diagram that can guide designers to select the appropriate rock armour size that will be stable for a certain set of flow conditions. The study also revealed that the long term persistence of flow conditions that just lead to incipient motion of the scour protection material can eventually lead to complete failure of the scour protection. The study provides a set of new design techniques that can allow designers to predict the scour depth around cylindrical and complex foundation geometries and also select the appropriate stone size for their scour protection system. Together, these techniques may allow for the reduction of costs associated with the scour protection of offshore and coastal structures.
3
Hobson, Paul Myron. "Rheologic and flume erosion characteristics of georgia sediments from bridge foundations." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26660.
Повний текст джерелаАнотація:
Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009.Committee Chair: Sturm, Terry; Committee Member: Burns, Susan; Committee Member: Webster, Donald. Part of the SMARTech Electronic Thesis and Dissertation Collection.
4
Pacheco, Gómez Rodolfo 1956. "CONTROLLING BRIDGE PIER SCOUR BY RIP-RAPPING." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276478.
Повний текст джерелаАнотація:
This thesis is a contribution to the existing knowledge of the nature of the scour hole around bridge piers. The analysis is based on the fictitious, long contraction concept developed by Dr. Emmett M. Laursen. This concept and its equation has been used herein to determine the size of rip-rap particles which will reduce the local scour at bridge piers. Evaluation of the parameters involved in it is required for sizing the rocks in a prototype. Values such as approach velocity, water depth, average diameter of the rip-rap particles in the scour, and geometry of the pier are among the values to be known. Both a graphic and an analytical procedure are proposed as a means to find the size of particles to be used as protection. The discussion and conclusions derived from this investigation will be of great help to civil engineers working in the field of river engineering.
5
Florkowski, Ronald W. "Evaluation of Unknown Foundations." Scholar Commons, 2007. http://scholarcommons.usf.edu/etd/3812.
Повний текст джерелаАнотація:
In recent years, bridge foundations have been in the spotlight throughout the nation. Bridges built over running water are susceptible to erosion or scour around their foundations. The reduction in load capacity to piers and abutments pose a safety risk to highway motorists. It has become necessary for engineers to examine and monitor these "scour critical" bridges. The difficulty arises with subsurface foundations of which very little is known about their construction. Hence, the methods applied to analyzing "Unknown Foundations" have become a necessary topic of research.
This thesis explores a method to determine foundation lengths. Similar to Sonic Echo / Impulse Response, this procedure measures reflected shock waves sent through concrete pilings. The technique is non-destructive in nature and is performed near the surface of the foundation. The test is performed on the side of the exposed piling. Current methods are limited by the fact that the tops of most pilings are inaccessible due to pilecaps or beams. Often times, pilings are embedded in stiff soils, which have a dampening effect on the stress waves. This thesis employs a method of analysis that will overcome such limitations and provide engineers with another tool to determine subsurface foundation lengths.
6
Collins, Carl. "Development and application of a computational model for scour around offshore wind turbine foundations." Thesis, University of Hull, 2017. http://hydra.hull.ac.uk/resources/hull:16530.
Повний текст джерелаАнотація:
There is a constant requirement to understand scour especially regarding its prevention, due to the potential impact and disastrous consequences. The installation of offshore wind turbines is haunted by scour mitigation and at the start of the offshore wind turbine boom in the early 2000’s this was achieved using overzealous amounts of rock armour. However, as investment and cost efficiency has increased, protection methods have been refined, but, there remains significant room for improvement. Research into offshore sediment dynamics has benefited greatly by computational advancements providing a greater understanding of processes and the driving mechanisms; leading to protection method improvements and reductions in environmental impact. The premise of this study is to push this knowledge further, by developing and validating a novel scour model within CFD software that can be used to simulate and analyse offshore scour; specifically, the scour around complex, new offshore wind turbine foundation geometries.
7
Marei, Khaled Mohammed Said. "The stability of riprap for bridge abutments or embankments." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276676.
Повний текст джерелаАнотація:
The main objective of this research is to estimate the sizes of riprap (loose rock) on highway or railroad embankments approaching bridges, that would be stable in major floods. Two assumptions about the flow direction were made: one horizontal to the bridge abutment and the other normal to the projection of the bridge abutment. Three dynamic conditions of stability of riprap were observed and classified as shaking, some movement, and large movement (washing out). Shaking is the most conservative criteria for design because it indicates more stability than is necessary, requires larger rock, and is less cost efficient. Some movement suggests a conservative design criteria and is the most desirable because it requires smaller riprap and is therefore less expensive. Large movement or washing out means the least stable condition; it may leave the structure as well as human lives exposed to danger.
8
Navarro, Hernan Ricardo. "Flume Measurements of Erosion Characterstics of Soil at Bridge Foundations in Georgia." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7267.
Повний текст джерелаАнотація:
Shelby tube sediment samples collected from the foundations of ten (10) bridges located in the state of Georgia were tested in the laboratory to find their erosional behavior and the correlation of erosion parameters with sediment properties in order to improve the prediction of scour around bridge foundations. These sites were spatially distributed in order to fall into different major river basins and in different physiographic regions. A description of the Valley and Ridge, Blue Ridge, Piedmont, and Coastal Plain physiographic regions of Georgia is included, and the erosion parameters found from flume measurements are associated with their respective regions. Flume measurements were performed using a rectangular, tilting, recirculating flume located in the hydraulics lab in the School of Civil and Environmental Engineering at Georgia Tech. Velocities up to 1.7 m/s and bed shear stresses up to 21 Pa can be achieved in the flume. Regression analysis was performed on erosion rates as a function of applied shear stress to determine the parameters of the erosion function. The resulting parameters, the critical shear stress and the erosion rate constant, were correlated with soil properties and physiographic regions.
Experimental methodology was chosen to approach this problem because the involvement of interparticle forces for fine-grained materials makes it difficult to deal with the erosion phenomenon through other means. Nevertheless, analytical description of the erosion phenomenon was included in order to provide a better understanding of it.
Linear, exponential and power regression mathematical models for erosion rate were compared, and the two best-fit regression models of erosion rate as a function of shear stress are proposed to formulate a methodology intended to characterize the behavior of a soil exposed to erosive flow conditions. One of them is a linear model to calculate critical shear stresses and low erosion rates. The second model, which is exponential, has the advantage of describing the erosion rate response for a wider range of shear stress values. It is shown that one of the most relevant predictors for the critical shear stress and erosion rate constant in the regression models is the fine material content present in the sample, which is an indirect indicator of the contribution of interparticle forces to the erosion process. Applying the described methodology, a more case-specific calculation of the erosion at bridge foundations can be performed taking into account the actual material in situ.
9
Michalis, Panagiotis A. "Real-time monitoring of scour and sediment deposition evolution at bridges and offshore wind turbine foundations based on soil electromagnetic properties." Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25704.
Повний текст джерела
10
Hesten, Peder. "Scour around wind turbine foundations, marine pipelines and short cylinders due to long-crested and short-crested nonlinear random waves plus currents." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-15740.
Повний текст джерелаАнотація:
This report presents a stochastic method for predicting scour depth around vertical circular slender piles, including various cross sections and group arrangements, marine pipelines and the burial and scour hole geometry around short cylinders due to long-crested (3D) and shortcrested (2D) nonlinear random waves plus current. The waves are assumed to be stationary narrowbanded and the Forristall (2000) distribution of wave crest heights representing 2D and 3D random waves is employed including both sum-frequency and difference-frequency effects. The wave crests are assumed to be responsible for the scour response. The results for scour and burial around the various structure types are presented graphically versus a measure of the wave action evaluated at the seabed relative to the characteristic diameter of the structure and versus a measure of the current velocity relative to the maximum horizontal fluid particle velocity at the seabed. The ratios between the scour depth predicted by 3D, 2D and linear waves are also investigated. Examples of calculation based on typical field conditions are provided. Due to the distinctive character of the Forristall distribution, all the results are specifically given by the seastate and the characteristic structure diameter. There are several similarities in the ratios of the scour depth for the various structures. Overall, 3D and 2D waves will produce more scour and burial than linear waves. This is due to higher fluid particla velocity under the wave crests for 3D and 2D waves compared to linear waves. In deep water, the scour depth from 2D waves is largest and in finite water depth the scour depth from 3D waves is largest. This is due to larger sum-frequency effects for 2D waves compared to 3D waves in deep water and smaller difference-frequency effects for 3D waves compared to 2D waves in finite water depth.
11
Lu, Shou-Ji, and 呂紹吉. "Dynamic Measuring Techniques of Levee Foundation Scour." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/27191142587329055987.
Повний текст джерелаАнотація:
碩士逢甲大學
水利工程與資源保育學系
104
Recently, the extreme climate types occur frequently under the effect of climate change. The high intensity rainfalls usually concentrate during the summer typhoon seasons in Taiwan. In addition, rivers are steep with rapid flows in Taiwan due to the geographical reasons. The degradation of the riverbed may seriously affect the safety and stability of flood protection works such as levees. The riverbed elevation difference may be insignificant before and after a flood. However significant scour usually occurs around the flood peak near the levee foundation due to the high flow discharge per unit width, causing the failure of a levee foundation. Therefore, how to monitor the dynamic variation of riverbed during a typhoon event to prevent levee foundation destruction becomes a very important issue. The main objective of this study is to improve the measuring technique of levee foundation scour depth by using the “water and soil interface monitoring instrument”. It is hoped that the levee foundation scour depth measuring system and estimation formulas can be developed based on these field data and the analysis with SPSS software to serve as a reference of planning and designing for relevant engineers. A series of experiments were conducted in the laboratory and field for the “water and soil interface instrument” in order to assess the feasibility of the real time dynamic scour depth measurements. There are four major tasks in this test, including water level, riverbed elevation, water-proof, and wireless data transmission. The results show that the water level and riverbed elevation can be accurately detected under different types of flows in all the tests. In addition, the “water and soil interface instrument” is fully water-proof and wireless transmission data are stable and accurate. The field study area of this project is near the Ke-Zhuang levee of the Da-Jia River. The monitoring station of the real time dynamic scour depth was established by using the “water and soil interface instrument” and the wireless tracer brick columns. Furthermore, a levee foundation scour depth estimation formula is developed by using the traditional nonlinear regression analysis method with the observed field data. The accuracy of the results for the formula developed in this project is the best among all of the estimation formulas compared. As the observed data is still limited, more data should be collected during typhoons in the future for further verification.
12
Yi-ChunLin and 林怡君. "Identification of foundation scour depth using bridge natural frequencies." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/11555419750730909364.
Повний текст джерелаАнотація:
碩士國立成功大學
土木工程學系碩博士班
101
Bridges have an important contribution to traffic, and most of bridges are across the river. However, typhoons every year could scour the foundation of bridges, and the bridge damages caused by foundation exposing in the rivers may create shortage of the foundation carrying capacity that bring bridge to collapse. There are many of dangerous bridges in Taiwan because of scour in rivers. Since the bridge foundation damage always underwater and cannot be observed directly, the bridge-monitor-system is made to find the bridge natural frequency and estimate the pile exposure level in this thesis. In the beginning, the bridge models for the several foundation scour depth with the different pier length, soil strengths and the different style of the pile foundations are created, then use three-dimensional continuous elements (called finite element analysis) and spring elements (called simple element analysis) to solve the soil-bridge problem and determine the bridge natural frequency . Afterward, the bridge natural frequency and the foundation scour depth interaction can be obtained to predict the exposure of pile foundation. Finally, comparing the simple element analysis and finite element analysis results indicates that the two methods obtain similar results.
13
Nguyen, Huong-Duong, and 阮向陽. "EFFECTS OF DEBRIS AND SCOUR DEPTH ON PILE FOUNDATION BRIDGE." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/43468731119359781065.
Повний текст джерелаАнотація:
碩士臺灣大學
土木工程學研究所
98
Typhoon Morakot (or typhoon No 8) of August 8, 2009, destroyed a total of 90 bridges around Taiwan. Water levels have traditionally been the sole criteria for bridge closure amid flooding in Taiwan., Under current guidelines, many bridges were not closed off before they collapsed this time. Take, for instance, the 2,083-meter Shuang Yuan Bridge, which was actually two separate bridges, one for each direction long of traffic. This bridge is expected in good conditions when the northbound bridge''s No. 2-15 piers and the southbound bridge''s No. 2-16 piers were washed away by raging currents. In current time, the velocity of water flow, the geological condition of each bridge needs to be considered. In this study, the capacity of Shuang Yuan Bridge was investigated under different levels of scoured depth. The pile axial capacity based on soil parameters, the bending, shear capacity and buckling instability of piles was analyzed. Scoured group pile foundations were modeled by Sap 2000. Debris load was also computed based on various water velocities, debris geometry and hydraulic parameters assumption. The pushover analysis is carried out with water and debris load to find the capacity curve of the bridge with different scoured depth, then the maximum applied floodwater force acting on a pier, and the performance water velocity is determined. The possible causes of Shuang Yuan Bridge failure are also pointed out.
14
Kuo, Huan-Wei, and 郭桓瑋. "Numerical simulation of scour around foundation of offshore wind turbine." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/69f3b6.
Повний текст джерелаАнотація:
碩士國立臺灣大學
應用力學研究所
105
In this study, we employ large eddy simulation (LES) along with ghost cell immersed boundary method (GCIBM) and arbitrary Lagrangian-Eulerian scheme (ALE) to simulate local scour induced by flow over a wall-mounted structure. In order to simulate the instantaneous evolution of the bed form, we use LES to resolve the detailed flow features. The GCIBM is used to model the geometry associated with the complex solid boundaries without much computational effort. Moreover, the ALE scheme incorporates the grid velocity such that the domain boundary is able to follow the time-dependent bed form geometry. The numerical study comprises four parts. The first part presents the steady current passing an idealized structure with the different shape. Our simulation results show that the sharp-nosed body effectively reduces the bed erosion. In the second part, simulations of the bed scour under field conditions are presented, by means of the law of similarity. The main erosion mechanism within the range of the field Keulegan-Carpenter number (KC) is due to lee-wake vortices. The third part considers the bed scour around a cylinder with the riprap protection. Results show that due to asymmetric motion of lee-wake vortices, scour is more vigorous at the left side of the riprap. The fourth part presents the simulation of scour during a long-wave period. When the wave period increases, the formation of horseshoe vortices around the cylinder is evident. As a result, the scour pattern is different from that in the small KC case. In the latter case, erosion mainly occurs at the left and right sides of the cylinder. In the former case, the scour hole forms around the cylinder, which appears to be a feature similar to the case of the steady current.
15
Jian-WeiLi and 李建緯. "Scour around the offshore wind turbine foundation with the composite protection." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/50450361433789004799.
Повний текст джерелаАнотація:
碩士國立成功大學
水利及海洋工程學系碩博士班
101
This paper aims to study the use of experimental base of offshore wind turbine casing underwater influenced by waves and stream suffered erosion around the base case . And with the use of offshore aquaculture structures , Cage structure, on the surface facing the stream and wave , compare the difference of the surrounding base of the topography be scoured for cage. Test at National Cheng Kung University Hydraulics Laboratory plane tanks. First , the test carried out hydrodynamic tests discussing the different positions and length of cage netting, effecting of stream mitigation and reduction of wave height , find the optimum conditions for cage. Then fixed rule wave height and different wave periods, the experiments of wave attenuation were conducted. According to the above experimental results, two cases were taken the best cage condition to test for terrain erosion, and the situation of the topography scouring were investigated. According to wave attenuation and slow down on test results, after placed cages in facing wave side, the wave attenuation was little affect. When the cage is placed in facing stream surface, stream rate has been significantly decreased. under low stream rate , cage placement closer , netting the longer the length , the better the effect of slowing down the stream rate. Experimental results in terms movable bed for pure stream, it is found that in the absence of cages the erosion affect large regions are mainly located in the surface facing the stream. The greater the rate the greater the depth of maximum scour will be, the greater the impact of scour range and due to the base effect the flow field the larger the range of deposition will be. After using cages , each of the stream rate has improved maximum scour depth and greater depth range is reduced erosion and other effects. Due to the base and the cage effect the flow field and the formation of sediment range is larger than those without cages , especially under the high rate, the deposition ranges formed by the base and the cage effect is larger. In wave-current interaction system, the scour affect large regions are mainly located facing the wave side and the facing stream side. After using cages in facing the stream, has decreased maximum scour depth and range of larger scour depth on the base of the pile facing the stream ,and in the back wave side there are siltation because the stream field affected by cage resulting. When using cage facing the wave side and the stream side, the cage of facing the wave side the maximum scour depth and greater depth of scour range has also improved.
16
Wen-YenChou and 周文彥. "Investigation of the Relationship between Bridge Natural Frequencies and Foundation Scour Depth." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/91930059754228560280.
Повний текст джерелаАнотація:
碩士國立成功大學
土木工程學系碩博士班
100
Most bridges in Taiwan are built across the river, so the stability of the bridge foundation is an important issue. As the bridge is burst, it may cause the damage for the human life, the interruption of the traffic, and the economic loss. When the typhoon invades, the bridge foundation may be scoured and cause the bridge collapse. Therefore, the bridge foundation scour depth can be applied to judge whether the bridge are in danger or not. However, it is difficult to measure the bridge foundation scour depth directly because most bridge foundations in Taiwan are under water, especially when the floods come. To overcome the problem, this thesis provides the bridge natural frequency to estimate the foundation scour depth. In the beginning, the bridge models for the various scour depths with the different soil strengths and the different style of the pile foundations are created, and the finite element method will be applied to determine the bridge natural frequency with the soil-bridge interaction problem. Then, the relationship between the bridge natural frequency and the foundation scour depth can be obtained to estimate the pile exposure level. Moreover, a general Gaussian function is applied to fit the curve of the frequency data. The formula of the curve fitting obtained in this study is acceptable to find the relationship between the bridge natural frequency and the foundation scour depth. A field experiment was performed in this thesis. By measuring the frequencies of the Sih-tsau Bridge, the random decrement method, Fast Fourier Transform method, and the Ibrahim time domain method are applied to identify the true natural frequency of the bridge.
17
Diau, Jikun, and 刁繼堃. "Effect of Scour on Lateral Response of Deep Foundation for Bridge Pier." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/23064546844170611368.
Повний текст джерелаАнотація:
碩士國立暨南國際大學
土木工程學系
101
The reduction in capacity and increase in deflection of the foundation system as a result of scouring are factors affecting safety of bridges encountering flood current. Understanding the effect of scour on lateral capacity of foundation is an essential element in addressing mitigation of this adverse effect. In this study, the effect of scour on a single pile is investigated systematically through results of model pile tests. It is founded that the reduction ratio R (of the lateral capacity) and the amplification ratio A (of the maximum bending moment) are useful indexes to quantify the scour effect. Effect of soil stiffness, pile slenderness ratio, and scour depth ratio on the value of R and A are examined. Simple yet rational correlations between R and scour depth ratio as well as A and scour depth ratio are established. Used of the developed correlation in design and disaster prevention also are discussed.
18
Fong-TingLin and 林奉廷. "Dynamic Behavior of Bridge Foundation under Scour-A case study on Shin-Fa Bridge." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/q7j7fa.
Повний текст джерелаАнотація:
碩士國立成功大學
土木工程學系碩博士班
101
Due to the special geologically conditions, rivers in Taiwan are relatively short and steep. Therefore the foundations of the cross-river bridge are common suffered from scouring; foundations would be exposed and lose their bearing capacity; even collapse. Therefore, it is necessary to prevent the erosion of the foundation of the river in advance. However, the erosion usually occurred during typhoon attacked, it is difficult to observe the erosion condition under the condition of rainstorm just by visual eyes. Therefore, it is necessary to develop the instrument to measure the scouring and erosion condition during under the condition of rainstorm. In this study, the instruments were installed at the Shin-Fa bridge that located in Kaohsiung Liou-geui Distinct. The instruments were proposed to be monitored the long term characteristics of vibration and to evaluate stability of the bridge. Before long term monitoring, the initial conditions of the structures of the bridge which including geometric conditions, characteristics of bridge vibration obtained from field test were collected. Then the bridge model was established by the software that formulated by finite element method. Simulation of soil-structure interaction system was conducted by bridge modal analysis. Then calibration of the modal shape of the bridge by measuring the field vibration test. Finally three failure modes of the bridge foundation which including overturning, sliding and bearing capacity were checked by using limit equilibrium method. For considering the stability of the moment-resisting of bridge foundation under different flow velocities, water levels and the depths of scouring, the pushover analysis by using numerical model was performed. Based on the results of those analyses, an early warning system can be established and provide the reference as a policy for bridge closing during rainstorm and typhoon season.
19
Shen, Ming-Yi, and 沈明毅. "Experimental Study on Developing Scour Fragility Curves- A Case Study of Bridge Pile Foundation." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/39579605510962554552.
Повний текст джерелаАнотація:
碩士國立臺灣大學
土木工程學研究所
101
The escalating scale of natural disasters associated with global climate change and the growing world population increasingly threatens civil infrastructure. In particular, floods accelerate process of local scour around bridge piers resulting in damage to or failure of cross-water bridge structures. This study proposed a procedure for constructing scour fragility curves from flume experimental data for piled bridge pier. By a series of single-pile bridge pushover tests, the relationship between scour depth and capacity loss can be derived from the results. In addition, several flume experiments with a pier model scouring under controlled conditions were conducted and the scour process variation was observed. The scour depth observed from flume experiments were used to develop scour fragility curve which could be applied to evaluate the scour vulnerabilities of piled bridge pier for preliminary studies. A methodology to construct the scour fragility curve from flume experimental data was presented in this study; the main purpose of this paper is to show how the experimental data were used to build the scour fragility curves which are defined as a function of scour depth ratio or capacity loss ratio. The measured trend of the curves consists with the general scour process and the realistic behavior of piled bridge pier damage sequence. This paper has shown a feasible and practical methodology to construct the scour fragility curves from experiments.
20
Wei-ChenTseng and 曾韋禎. "Effect of Scour on the Dynamic Response of Offshore Wind Turbine with Monopile Foundation." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/345958.
Повний текст джерелаАнотація:
博士國立成功大學
土木工程學系
106
Severe foundation scour may occur around monopile foundations of offshore wind turbines due to currents and waves. The p–y curve method recommended in the current offshore foundation design codes does not account for the local scour around the pile foundation; it overestimates the lateral pile deformation and underestimates the foundation stiffness. This study presents a method to correct the initial modulus of subgrade reaction and modify the ultimate lateral resistance caused by the local scour. The natural frequency of the met mast structure is also determined by a numerical model and verified with the measured data in situ. A comprehensive parameter study is performed to analyze the effect of scour on the dynamic responses of the met mast. Furthermore, the scour exerted significant effects on certain modes of the vibration responses. The natural frequencies of the met mast structure can be reduced by approximately 14% due to scour, particularly in the horizontal bending modes. This study also provides a preliminary strategy for structural monitoring and analysis to detect scour damage on offshore wind turbines with monopile foundations. And the numerical model of the reference offshore wind turbine with monopile unprotected against scour at Chang-Bin offshore wind farm in Taiwan Strait is established. The results showed that when the p-y curve suggested by existing design regulation was used to calculate the load-deformation response, the foundation stiffness was underestimated where the scour depth was greater than the pile diameter, but the foundation stiffness was overestimated when the scour depth was less than the pile diameter.
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CHANG, YI-HSIN, and 張藝馨. "Local Scour aroung Nonuniform Piers and Pile Foundations." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/44218843847065938388.
Повний текст джерелаАнотація:
碩士國立中央大學
土木工程研究所
88
Most rivers in Taiwan are severely degrading during last two decades due to fast growing in-stream sand mining and construction of water supply or diversion works. Consequently, the exposure of bridge foundations, such as caissons and piles of bridge piers , is one of the most critical issue for the design and maintenance of river-crossing bridges. Inadequate design of countermeasures at bridge crossings may incur further local and contraction scours. The scouring process, such as maximum scour depth and scour dept and scour depth and scour range, around non-uniform piers and pile foundations are examined in this study by employing laboratory experiments . The suitable countermeasures for those foundations will is also investigated
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Lin, Yunjie. "Scour effects on lateral behavior of pile foundations." Thesis, 2019. http://hdl.handle.net/1828/11123.
Повний текст джерелаАнотація:
Scour is a phenomenon of soil erosion around foundations under currents and waves. It is a major cause for the disruption to water-borne structures such as bridges and marine structures. Pile foundations supporting these structures are required to be designed against the scour damage. However, at present, there is no accepted method for the design of piles in scoured conditions probably due to an inadequate understanding of scour effects on foundations.
Although numerous efforts have been made to evaluate the scour effects on single piles using numerical simulations and centrifuges tests, the scour susceptibility of piles in different soil properties is still not well understood. Furthermore, there is no study concerning scour effects on the lateral responses of pile groups. Therefore, a series of three-dimensional finite element (FE) parametric analyses were conducted to investigate scour effects on lateral behavior of both single piles and free-head pile groups by varying scour-hole dimensions, soil properties, pile properties, and pile group configurations. Moreover, to facilitate the routine design, a modified p-y method that was modified based on the widely used p-y method was proposed for both scoured single piles and pile groups, and was validated against the results from the FE analyses. The results show that scour induced lateral capacity loss to both single piles and pile groups, which was approximately 10% more in dense sands than that in loose sands. Simplification of local scour as a general scour that has been commonly used in general design practice resulted in a maximum of 17% underestimate of lateral capacity of pile foundations. Pile groups were more susceptible to scour than single piles under equivalent scour conditions. A pile group with smaller pile spacing or larger pile numbers tended to experience less lateral capacity loss due to scour.Graduate
2020-08-19
23
Leão, Israel Neto dos Santos Ribeiro. "Reliability-based assessment of scour protections in offshore fixed foundations." Master's thesis, 2016. https://repositorio-aberto.up.pt/handle/10216/100388.
Повний текст джерела
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Leão, Israel Neto dos Santos Ribeiro. "Reliability-based assessment of scour protections in offshore fixed foundations." Dissertação, 2016. https://repositorio-aberto.up.pt/handle/10216/100388.
Повний текст джерела
25
Yao, Congpu. "LRFD Calibration of Bridge Foundations Subjected to Scour and Risk Analysis." Thesis, 2013. http://hdl.handle.net/1969.1/149453.
Повний текст джерелаАнотація:
Bridge scour is the loss of soil by erosion due to water flowing around bridge supports. Scour has been the number one cause of bridge collapse in the United States with an average rate of 22 bridges collapsing each year. This dissertation addresses three topics related to bridge scour. First, three sets of databases are used to quantify the statistical parameters associated with the scatter between the predicted and measured scour depth as well as the probability that a deterministically predicted scour depth will be exceeded. The analysis results from these databases will also be used to provide the bias factors in the scour depth predictions in practice. In the second part of the dissertation, these statistical parameters are used to develop a reliability-based Load and Resistance Factor Design (LRFD) for shallow and deep foundations subjected to scour. The goal is to provide a design procedure for the bridge foundations, where the reliability of the foundation is the same with or without scour. For shallow foundations, the key of the design issue is the location of the foundation depth and the probability that the scour depth will exceed the foundation depth. Therefore, for shallow foundations, the proposed LRFD calibration is based on the probability of exceedance of the predicted scour depth. However for deep foundations, the key of the design issue is the resistance factor associated with the axial capacity of a pile. Hence, the proposed LRFD calibration for deep foundations is based on a reliability analysis using First-Order Reliability Method (FORM). The dissertation is broadened in the third part by analyzing he risk associated with bridge scour, where the risk is defined as the probability of failure times the value of the consequences. In the third part, the risk associated with bridge scour is compared to risks associated with other engineering structures as well. Target values of acceptable risk are recommended as part of the conclusions.
The outcome of the research will modify the current “AASHTO LRFD Bridge Design Specifications” developed by the American Association of State Highway and Transportation Officials (AASHTO) and help the practitioners design foundations of bridges over rivers for a uniform probability of failure in the case of scour. The risk of bridge scour is also quantified in the dissertation, and compared with common societal risks and civil engineering risks. It will help engineers understand the risk level associated with bridge scour.
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Ferradosa, Tiago João Fazeres Marques. "Reliability Analysis Applied to the Optimization of Dynamic Scour Protections for Offshore Windfarm Foundations." Doctoral thesis, 2018. https://hdl.handle.net/10216/115848.
Повний текст джерела
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Ferradosa, Tiago João Fazeres Marques. "Reliability Analysis Applied to the Optimization of Dynamic Scour Protections for Offshore Windfarm Foundations." Tese, 2018. https://hdl.handle.net/10216/115848.
Повний текст джерела
28
Chang-KengWu and 吳長庚. "Effect of Scour Depth on The Deformation Response of Pile Foundations under Axial Loads." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/76502872198902311645.
Повний текст джерела
29
Yousefpour, Negin. "Comparative Deterministic and Probabilistic Modeling in Geotechnics: Applications to Stabilization of Organic Soils, Determination of Unknown Foundations for Bridge Scour, and One-Dimensional Diffusion Processes." Thesis, 2013. http://hdl.handle.net/1969.1/151268.
Повний текст джерелаАнотація:
This study presents different aspects on the use of deterministic methods including Artificial Neural Networks (ANNs), and linear and nonlinear regression, as well as probabilistic methods including Bayesian inference and Monte Carlo methods to develop reliable solutions for challenging problems in geotechnics. This study addresses the theoretical and computational advantages and limitations of these methods in application to: 1) prediction of the stiffness and strength of stabilized organic soils, 2) determination of unknown foundations for bridges vulnerable to scour, and 3) uncertainty quantification for one-dimensional diffusion processes.
ANNs were successfully implemented in this study to develop nonlinear models for the mechanical properties of stabilized organic soils. ANN models were able to learn from the training examples and then generalize the trend to make predictions for the stiffness and strength of stabilized organic soils. A stepwise parameter selection and a sensitivity analysis method were implemented to identify the most relevant factors for the prediction of the stiffness and strength. Also, the variations of the stiffness and strength with respect to each factor were investigated.
A deterministic and a probabilistic approach were proposed to evaluate the characteristics of unknown foundations of bridges subjected to scour. The proposed methods were successfully implemented and validated by collecting data for bridges in the Bryan District. ANN models were developed and trained using the database of bridges to predict the foundation type and embedment depth. The probabilistic Bayesian approach generated probability distributions for the foundation and soil characteristics and was able to capture the uncertainty in the predictions.
The parametric and numerical uncertainties in the one-dimensional diffusion process were evaluated under varying observation conditions. The inverse problem was solved using Bayesian inference formulated by both the analytical and numerical solutions of the ordinary differential equation of diffusion. The numerical uncertainty was evaluated by comparing the mean and standard deviation of the posterior realizations of the process corresponding to the analytical and numerical solutions of the forward problem. It was shown that higher correlation in the structure of the observations increased both parametric and numerical uncertainties, whereas increasing the number of data dramatically decreased the uncertainties in the diffusion process.