Multilevel Performance Classifications of Tall RC Bridge Columns toward Postearthquake Rehabilitation Requirements
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This study aims at developing appropriate multilevel performance classification of tall RC bridge piers for seismic design. A new performance classification toward postearthquake rehabilitation requirements is presented. It considers damage states of the local environmental conditions and accessibility of the potentially damaged part. To reduce postearthquake rehabilitation requirements, higher performance levels allowing only minor and moderate damages are advised for tall bridge piers. Two RC columns with high aspect ratios were designed, fabricated, and tested under static cyclic loading, focusing primarily on minor and moderate damage states such as residual concrete cracking and onset of visible concrete crushing. The experimental results show that the zero-tip-displacement crack width measured after the column returned to zero tip displacement significantly underestimated residual-cracking damage, while the zero-lateral-force crack width can be taken as an approximate estimation for the residual cracking on the safe side. An improved model is proposed to evaluate the cracking behavior beyond steel yielding. In this model, the expected residual-crack width is expressed as a function of the maximum crack width. The results obtained using the model show good agreement with the experimental results. For the onset of concrete crushing, 24 cantilever test columns in total were analyzed, with aspect ratios equal to or greater than 3.0 and axial-load ratios ranging from 0.05 to 0.25. The results indicate that a higher aspect ratio and lower axial-load ratio lead to a higher drift ratio corresponding to the onset of visible concrete crushing.Keywords:
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Laboratory data, showing the effect of simulated floating debris accumulation at bridge piers on the local scour depth, are presented. The experiments are conducted using idealized impermeable cylindrical debris shapes attached concentrically to a cylindrical pier. The maximum scour depth recorded is 3.6 times the pier diameter. The design method proposed by Melville and Sutherland in 1988 is shown to predict the maximum possible local scour for a pier with simulated floating debris accumulation provided that an effective pier width is substituted for the actual pier width. The effective pier width is calculated as a weighted average of lengths (vertical dimension) of the debris and exposed pier.
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Abstract In order to study the influence of pier anti-collision pontoon on the vortex behind pier tail and horse-shoe vortex around pier, taking circular pier as an example, Reynolds stress (RSM) turbulence model is used to numerically simulate the flow around pier with anti-collision pontoon. Firstly, the rationality of the numerical simulation method and the accuracy of the results are verified by comparing with the cylindrical flow model test. Then, the bare pier is equipped with an anti-collision pontoon to calculate the flow around the pier under different water depths. The results show that the installation of anti-collision pontoon will change the vortex structure of the flow around the pier; the vortex in the pier tail will fuse obviously due to the interference of the floating tank, resulting in the non-stationary characteristics. When the water depth becomes shallow, the position of horse-shoe vortex in front of the pier will gradually close to the pier, and the bed erosion caused by horse-shoe vortex on both sides of the pier will be more serious.
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In order to assess the residual strength of damaged warships reasonably,based on the reliability method,a method for analyzing the damaged warship’s residual strength is presented by considering the un-certainties of residual capability and loads.A warship is taken as an example to compute its residual strength by using this method and the certainty method recommend by LR naval ship rules.The conclusions of reli-ability assessment are quite tally with the results of the certainty method.Moreover,the reliability method presented in this paper can reflect the residual condition of damaged warship more clearly through calcu-lating its failure probability and this method makes quantitative analysis about the effects of sea conditions,damaged degree,sea direction and ship speed,etc.At the same time,the sizes of broken holes which may evidently affect the residual strength are investigated.
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Previous experimental research on utilizing pier modifications as countermeasures against local scour has focused primarily on circular pier. It is of utmost importance to further investigate the most suitable pier shape for pier modification countermeasure separately and in combination. This experimental study aims to reduce the stagnation of the flow and vortex formation in front of the bridge pier by providing a collar, a hooked collar, a cable, and openings separately and in combination around a suitable pier shape. Therefore, six different pier shapes were utilized to find out the influence of pier shape on local scouring for a length–width ratio smaller than or equal to 3. A plain octagonal shape was shown as having more satisfactory results in reducing scour compared to other pier shapes. Furthermore, the efficiency of pier modification was then evaluated by testing different combinations of collar, hooked collar, cable, and openings within the octagonal bridge pier, which was compared to an unprotected octagonal pier without any modification. The results show that by applying such modifications, the scour depth reduced significantly. The best combination was found to be a hooked collar with cable and openings around an octagonal pier. It was revealed that the best combination reduced almost 53% of scour depth, as compared to an unprotected octagonal pier.
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Flow Characteristics and Scour Depth in Lenticular Shaped Pier: Case Study at Ciujung Bridge, Banten
Abstract Pier is part of the structure under the bridge. The existence of a pier in the river flow causes changes in river flow patterns. Changes in the flow pattern will result in local scouring around the pier. This study aims to determine the effect of the shape of the pier on the potential for local scour that occurs around the pier, and the flow characteristics around the pier. This studymodelled the existing conditions of the Ciujung Bridge, where the Ciujung Bridge uses an oblong pier shape, and the shape will be replaced with a lenticular model pier. FLOW-3D (CFD) software will be used to modelled flow characteristics and the depth of scour that occurs.
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Unsafe Ship-handling model (US-model) is known as an evaluation method which analyzes the potential risk of marine accidents. In previous paper, this model was improved for evaluating small obstacles, definitely. This research aims to evaluate the influence of the pier arrangement by applying the improved US-model to the bridge design on a straight channel and a curved channel. In ship-handling simulator, a bridge with the various pier-pier distances was set on the straight channel. The potential collision risk to the pier decreases when the pier-pier distance is wide enough, such as 2000m by the experiment results. In the traffic simulation, pier-pier distances, pier arrangement types and curved angles were set on the curved channel. The potential collision risk extremely increases at the following conditions. (1) The pier-pier distance is less than 1500m. (2) The curved angle becomes severe at the pier-pier distance is 1000m. (3) The arranged pair of pier is set on the backward side from the curved corner. In conclusion, it can be said that the improved US-model could evaluate the influence of the pier arrangement on a straight and a curved channel clearly.
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There are many kinds of commonly-used bridge pier types. This paper researches the selection principle and optimal type of the bridge pier types from the perspective of reducing backwater. This paper also tests and analyzes the high resistance water for different types of bridge pier under different flow velocities and conditions of water resistance ratio through establishment of a physical model of wide water channel. The result shows that, the bridge pier has an optimal profile curve, and the characteristic parameter (b’/L) is from 0.071 to 0.083; three kinds of commonly-used pier types – square pier, streamline pier and bicircular pier have different strength angles. If the angle between the axis of bridge pier and the water flow direction is less than 36°, it should give priority to the streamline pier; if the angle is greater than 36°, then it should give priority to the bicircular pier.
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Bridge pier is a crucial part for the transportation in marine structures. Scouring is a major cause for the failure of the pier. slot among the other countermeasures increases the efficiency of scour reduction and minimizes the failure due to scour.as we provide the slot; the strength of the pier reduces compared to the conventional pier. change in reinforcement pattern in slotted bridge pier changes the behavior of the pier under similar loading conditions. blast occurrence has increased in recent times and rehabilitation of a structure and improvement of strength against explosion is necessary in structure. this paper studies the behavior of slotted bridge pier under blast loading and compares theoretical and analytical aspects for the same. Design criteria for blast load according to NCHRP 12-72 are followed to carry out theoretical load response of the pier under blast loading. Analytically the behavior of pier is checked using coupled eulerian lagrangian approach using ABAQUS software. a detailed eulerian domain and slotted pier with reinforcement is assembled in ABAQUS to analyze the behavior of pier under explosion using TNT of 100kg at a scaled distance of 4ft for the period of 0.02seconds. this design gave better result in terms of mitigating effects of blast on slotted bridge pier.
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