Bridge failures are generally resulted from scour of the bed material around bridge piers and abutments during severe floods. In this study, scour phenomenon around bridge abutments and collars, located at abutments as scour countermeasures, were experimentally studied. The experimental study was carried out under clear-water scour conditions with uniform non-cohesive sediment (having a grain size diameter of d50=0.90 mm). The experimental flume is a rectangular channel of 30 m long and 1.5 m wide filled with this erodible bed material. Based on the results of 97 experiments conducted during the study, the efficiency of various sizes of collars, which were used to reduce the local scour depth, located at different elevations around the abutments was determined. The results obtained were compared with previous studies, and the effect of the sediment grain size on the performance of abutment collars was emphasized. It was noticed that when the collar width was increased and placed at or below the bed level, the reduction in scour depth increases considerably. It was also found out that the change of the sediment size did not affect the optimum location of the collar at the abutment, which yields the maximum scour reduction around the abutment.

During severe floods, bed material around bridge piers and abutments are scoured by the flow and as a result, bridges are subject to damages. These damages are mostly unrepairable and can result in loss of lives and property. In this thesis study, abutment scour under clear-water condition was investigated and collars were tested as scour countermeasures around the abutments. The experimental study was carried out in a rectangular channel with an almost uniform cohesionless bed material of d50=1.50 mm for a test period of 3-hours. The channel was 28.5 m long and 1.5 m wide. The erodible bed material was placed into the test section that was 5.8 m long and 0.48 m deep. For this thesis study, 60 experiments were carried out with and without various collars placed at different elevations around the abutments. The scour formation around the abutments with collars was observed and scour reduction efficiencies of the collars were studied. Experiment results were compared with the previous studies of Dogan (2008) and Kayat&uuml / rk (2005) in terms of sediment size, abutment shape and flow depth, and the effects of these factors on collar&#039 / s scour reduction efficiency were studied. Based on the results of the experimental studies, it was observed that scour depths decreased as the collar width increased and the collar placed deeper into the sediment bed for a given abutment length. When the present study and the previous studies were compared, it was observed that sediment size and flow depth had no significant effect on the scour reduction performances of the collars.

The major damage to bridges occurs due to scour of the bed materials around piers and abutments during severe floods. This study involves the experimental investigations of the various scour patterns forming around abutment models tested with and without collars as scour countermeasures. The experiments were conducted in a rectangular channel under clear-water scour conditions. In the first part of this study, 34 experiments were conducted with semi-circular end abutment models with and without a collar for a period of 3 hours. Collars of various sizes were placed at different elevations on the abutment models, and the scour reduction efficiencies of collars were investigated for the different flow depths. Based on the results of the experimental studies, the optimum locations of collars on the abutments, which result in minimum scour depth around the abutments, are obtained at the bed level and below the bed level depending on the flow intensity values. In the second part of this study, the effects of flow depth and abutment length on the temporal development of local scour at bridge abutments were studied. 20 experiments were performed without collars for a time period of 8 hours. It was observed that at the upstream of the abutment, the depth of the local scour increases rapidly within the first three hours of the experiment for the different flow depths.

ABSTRACT SCOUR AND SCOUR PROTECTION AT BRIDGE ABUTMENTS Kayat&uuml / rk, Serife Yurdag&uuml / l Ph. D., Department of Civil Engineering Supervisor: Prof. Dr. Mustafa G&ouml / g&uuml / S Co-Supervisor: Dr. Mehmet Ali K&ouml / kpinar January 2005, 213 pages Bridge failures are mainly caused by scouring the bed material around bridge foundations during flood. In this study, scour phenomenon around bridge abutments is experimentally studied. Effect of abutment size, location and size of the collars placed around the abutments, time evaluation of scour hole around the abutment, scour characteristics of abutment and pier interaction were experimentally investigated. Scour measurements were conducted in a rectangular channel of 30 m long and 1.5 m wide filled with erodable uniform sediment. In the first part of the study, in order to investigate the size effect of the abutment on the maximum scour depth, abutments of nine different sizes were tested for three different water depths. It was found that the length of the abutment is more important parameter than the width of it. Secondly, efficiency of various sizes of collars, which are used to reduce the local scour depth, located at different elevations around the abutments was determined. It was noticed that when the collar width was increased and placed at or below the bed level, the reduction in scour depth increases considerably. Some tests for partial-collar arrangements around the abutments were conducted and it was shown that instead of full-collar one can use partial-collar arrangements around the abutments to achieve the same efficiency as the full-collar. Time development of scour holes around the abutments with and without collar cases were recorded. It was observed considerable reductions in scour depths around the abutments can be obtained with collars compared to the cases in which there are no collars over the same time period. Finally, a series of experiments were carried out to investigate the interaction between bridge abutments and piers related to the local scour around them. Based on the experiments conducted with two different abutment lengths and pier diameters varying the lateral distances between them it was observed that scour depth reduction capacities of collars vary significantly while comparing a single abutment or pier.

Thesis (Ph. D.)--Indiana University School of Dentistry, 1999. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--Indiana University School of Dentistry, 1999. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Made available in DSpace on 2014-06-11T19:26:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-04Bitstream added on 2014-06-13T20:55:06Z : No. of bitstreams: 1 silva_ef_me_araca.pdf: 1411679 bytes, checksum: 3651a9f6c293e68c27d8e79e890167d0 (MD5) / Fundação para o Desenvolvimento da UNESP (FUNDUNESP) / A união dente-implante ainda gera divergências de opiniões. A proposta deste estudo foi avaliar pelo método da fotoelasticidade a distribuição do stress entre implantes e dentes, nas próteses parciais fixas, comparando conectores rígidos e semi-rígidos e implantes de hexágono interno e externo. Para isto, foram confeccionados dois modelos com resina fotoelástica PL-2, um com implante de hexágono interno (3i - Palm Beach Gardens, Fla. - 4,00 x 13 mm) e outro com implante de hexágono externo (3i - Palm Beach Gardens, Fla. - 4,00 x 13 mm). Três desenhos de próteses foram fabricados para cada modelo de implante, incorporando cada uma um tipo de conexão para unir implantes e dentes: 1) conexão rígida soldada; 2) conexão semi-rígida; 3) conexão rígida com parafuso oclusal. Os modelos foram colocados no polariscópio e cargas axiais de 100N foram aplicadas em pontos fixos na superfície oclusal das próteses. Os resultados mostraram tendência a uma menor intensidade nas tensões nas conexões semi-rígida e rígida soldada no modelo com implante de hexágono externo e maior intensidade nas tensões na conexão semi-rígida do hexágono interno. Dentro das limitações deste estudo, as seguintes conclusões foram obtidas: houve uma tendência a menor intensidade nas tensões na conexão semi-rígida e na conexão rígida soldada, no modelo com implante de hexágono externo; entre os três tipos de conexões no modelo com implante de hexágono interno, a conexão semi-rígida foi a mais desfavorável; na associação dente-implante é preferível a utilização do implante de hexágono externo. / The union tooth-implant still generate divergences of opinions. The purpose of this study was to examine for the photoelastic metod, the distribution of stress among implants and teeth, in the fixed partial prostheses, comparing rigid and semi-rigid connectors and internal and external hexagon implants. For this, two models were made with photoelastic resin PL-2, one with internal hexagon implant (3i - Palm Beach Gardens, Fla. - 4,00 x 13 mm) and other with external hexagon implant (3i - Palm Beach Gardens, Fla. - 4,00 x 13 mm). Three drawings of prostheses were manufactured for each implants model, incorporating each an the connection type to unite implants and teeth: 1) rigid welded connection; 2) semi-rigid connection; 3) rigid connection with screw oclusal. The models were placed in the polariscope and axial loads of 100N were applied in fixed points in the surface oclusal of the prostheses. The results showed tendency to smaller intensity in tensions in the connections semi-rigid and rigid welded in the model with external hexagon implants and larger intensity in the connection semi-rigid of the model internal hexagon implant. The following conclusions were draw: there was tendency the smallest intensity in tensions in the semi-rigid connection and in the rigid welded connection in the model with external hexagon; among the three types of connections in the model with internal hexagon implants the connection semi-rigid was the most unfavorable; in the association tooth-implants it is preferable the use of external hexagon implants.

Integral bridges are designed without expansion joints or bearings to eliminate the maintenance and repair costs associated with them. Thus, the expansion and contraction due to daily and seasonal temperature variations of the deck of the bridge are restricted by the abutments, causing the abutments to move cyclically towards and away from the granular material used as backfill. This movement results in a stress accumulation in the backfill retained by the abutments. The Discrete Element Method (DEM) was used was used to perform a numerical sensitivity analysis, investigating the effect of granular particle shape on the response of backfill material retained by integral bridge abutments.   Two DEM software suites were used to perform the simulations, namely STAR-CCM+, a commercial code, and Blaze-DEM, a research code under development at the University of Pretoria. Blaze-DEM makes use of Graphics Processing Unit (GPU) computing as opposed to traditional Central Processing Unit (CPU) computing. Blaze-DEM delivered computational times over 150 times faster than the equivalent simulation in STAR-CCM+. The results from the numerical sensitivity analysis showed that the particles with lower sphericities (higher angularities) experienced larger accumulations of stresses on the abutment as opposed to the more spherical particles. This was suggested to be a result of particle interlocking and reorientation. / Dissertation (MEng)--University of Pretoria, 2018. / Civil Engineering / MEng / Unrestricted

Full-scale lateral load tests were performed on a pile cap with five backfill conditions: no backfill, densely compacted fine gravel, loosely compacted fine gravel, densely compacted coarse gravel, and loosely compacted coarse gravel. Static loads, applied by hydraulic load actuators, were followed by low-frequency, actuator-driven cyclic loads as well as higher frequency dynamic loads from an eccentric mass shaker. Passive resistance from the backfill significantly increased the lateral capacity of the pile cap. Densely compacted backfill materials contributed about 70% of the total system resistance, whereas loosely compacted backfill materials contributed about 40%. The mobilized passive resistance occurred at displacement-to-height ratios of about 0.04 for the densely compacted gravels, whereas passive resistance in the loosely compacted materials does not fully mobilize until greater displacements are reached. Three methods were used to model the passive resistance of the backfill. Comparisons between calculated and measured responses for the densely compacted backfills indicate that in-situ shear strength test parameters provide reasonable agreement when a log-spiral method is used. Reasonable agreement for the loosely compacted backfills was obtained by either significantly reducing the interface friction angle to near zero or reducing the soil's frictional strength by a factor ranging from 0.65 to 0.85. Cracking, elevation changes, and horizontal strains in the backfill indicate that the looser materials fail differently than their densely compacted counterparts. Under both low frequency cyclic loading and higher frequency shaker loading, the backfill significantly increased the stiffness of the system. Loosely compacted soils approximately doubled the stiffness of the pile cap without backfill and densely compacted materials roughly quadrupled the stiffness of the pile cap. The backfill also affected the damping of the system in both the cyclic and the dynamic cases, with a typical damping ratio of at least 15% being observed for the foundation system.

Large scale static lateral load tests were completed on a pile cap with wingwalls under several different sand backfill configurations: no backfill, loosely compacted unconfined, loosely compacted slip plane wall confined, loosely compacted MSE wingwall confined, and densely compacted MSE wingwall confined. The relative compaction of the backfill was varied during each test to observe the change in passive resistance provided by the backfill. The wall types were varied to observe the force placed on the walls and the wall displacement as a result of the laterally loaded pile cap and backfill relative compaction. Passive force-displacement curves were generated from each test. It was found that the densely compacted material provided a much greater passive resistance than the loosely compacted material by 43% (251 kips) when confined by MSE walls. The outward displacement of the MSE walls decreased noticeably for the dense MSE test relative to the loose MSE test. Backfill cracking and heave severity also increased as the relative compaction level of the backfill increased. As the maximum passive force was reached, the reinforcement reached their peak pullout resistance. Correlations were developed between the passive pressure acting on the pile cap and the pressure measured on the MSE wingwalls as a function of distance from the pile cap for both loose and dense backfills. The pressure measured on the wingwalls was approximately 3 to 9% of the pressure acting on the pile cap. As the distance from the pile cap increased, the pressure ratio decreased. This result helps predict the capacity of the wingwalls in abutment design and the amount of allowable wall deflection before pullout of the backfill reinforcement occurs. Three methods were used to model the measured passive force-displacement curves of each test. Overall, the computed curves were in good agreement with the measured curves. However, the triaxial soil friction angle needed to be increased to the plane strain friction angle to accurately model both the loose and dense sand MSE and slip plane wall confined tests. The plane strain friction angle was found to be between 9 to 17% greater than the triaxial friction angle.