Every year many bridges around the world fail most of them due to scouring at their piers and abutments. Collapse of bridges cause heavy damage, and therefore, study on the control of scouring at the bridge site plays an important rule in bridge design.In this study application of half collar on rectangular piers is proposed as a simple method to control scouring. Experiments show that installation of a small half collar with a width equal to half of the pier width, at 10% of flow depth under the streambed level could reduce depth of scour hole by 40%. Experiments also show that a larger collar with a width equal to the pier width when installed at streambed level reduces the scour hole by 80%. Double collar was also tested. It was found that a small collar at 10% of depth above another small collar at the bed level increases its efficiency by more than 16%.

In this study, bridge pier riprap sizing has been derived using new data mining techniques. Classification and regression tree (CART) and multivariate adaptive regression splines (MARS) were used to design a stable riprap size around bridge piers. The dimensionless parameters of pier shape factor (Ks), Froude number (Fr), pier width to flow depth ratio (b/y), specific gravity (1-Sg), riprap layers (n) and placement of riprap mattress to original sediment bed level (1-d/y) as input data and the riprap diameter to flow depth ratio (DR/y) as output one, were employed for training and testing the models. The applied models had similar performances in the training phase, while the results of testing phase showed better performance for the CART model. Some of the riprap stability equations and statistical criteria were used to investigate the performance of the applied models. The statistical analysis showed that the CART model had a better performance than the other equations, so that its sum of squares error value reduced to one-third, with respect to the Hec- 18 equation. In addition, the accuracy of the CART model was 88% which was 15% more than that of the Hec-18 equation. Sensitivity analysis on the CART model indicated that the Froude number and pier width to flow depth ratio had the highest effects on riprap stability.

In previous studies, sizing riprap layer around bridge pier as scour countermeasure was for 100% protection against scouring. However, in many cases limited scour depth around a pier maybe accepted if only smaller riprap sizes are available. In the present work the effects of smaller size of riprap stones than the stable size on the scour depth is studied. Circular and oval shapes for riprap extent as well as both round and angular stone shape were tested. All tests were conducted at the threshold of bed sediment motion and the maximum scour depth was measured. The results of these experiments showed that with stone sizes closer to stable riprap, the efficiency of both round and angular stone shape was identical. As, size of riprap was reduced, deeper scour holes were observed with both round and angular shape material. The results also indicated that increasing the extent of the riprap layer from circular to oval with 5 times more riprap volume had insignificant effects on scour hole for angular shape riprap meanwhile reduced the scour depth with round shape material. Based on experimental data a method was developed to calculate a smaller riprap size based on an accepted limited scour hole.

Accelerated construction methods are extensively used worldwide to reduce the negative impacts of bridge construction on urban traffic. These methods usually require prefabricating parts of the bridge off-site, which reduces on-site construction time and improves the quality and safety of construction. While the use of precast elements for bridge decks is relatively common, using precast elements for bridge piers is a recent development, especially in high-seismicity regions. Prefabrication of bridge piers can further expedite the construction of bridges. Moreover, the use of precast elements can be combined with a self-centering capability, through which the earthquake-induced damage and cost of post-earthquake repairs are greatly reduced. Despite a number of previous numerical and experimental studies on the behavior of precast, self-centering bridge piers, limited information is available on the selection of design parameters for such piers, and important decisions such as the prestressing force needed to achieve suitable seismic behavior remains to a large extent uncertain. This study aims to investigate the seismic behavior of concrete bridges consisting of precast self-centering piers, in which unbonded, post-tensioned tendons are used for self-centering and reinforcing steel is used to dissipate earthquake energy. A two-dimensional numerical model was developed in OpenSees to simulate the behavior of concrete bridges consisting of precast self-centering piers. The model consisted of fiber elements to model concrete and mild steel, as well as truss elements to model unbonded post-tensioning steel. The model also involved the use of zero-length sections to model the bond-slip behavior of mild steel bars. The modeling approach was validated based on experimental results available in the literature on cyclic loading of four bridge piers. To evaluate the effects of various design parameters on the behavior of precast segmental bridge piers, 9 segmental piers with different percentages of prestressing force and reinforcing steel were designed according to 2017 AASHTO LRFD Bridge Design Specifications. All piers were designed to possess similar nominal flexural capacities. The piers were then subjected to monotonic, cyclic, and dynamic time history analyses. The results showed the positive effects of prestressing in delaying cracking and reducing the residual drifts of precast bridge piers. Increasing the prestressing force ratio up to 10 percent of compressive strength of the pier cross section was observed to improve the overall seismic behavior of the structure, above which a further increase in the prestressing level may result in a diminished performance. The optimal value for the prestressing force ratio, which resulted in the most desirable behavior for cyclic and dynamic loadings was therefore found between 0.1 and 0.15. In piers with a prestressing ratio above 0.15, a decrease was observed in the area of hysteresis loops, which was accompanied by negative stiffness of the base shear versus drift curve. Moreover, the residual drift of the pier increased when prestressing ratios greater than 0.15 were used. The maximum drift of the structure was found to be insensitive to the prestressing force ratio. The results of this study are of great value for optimal design of precast, self-centering bridge piers in high-seismicity regions.

Flow pattern around bridge pier and its effects is one of the interest of hydraulic engineers. Since numerical models are progressing as a tool to analyses flow fields, in this paper numerical simulation of flow pattern around bridge pier is studied and its consequent effects on backwater is investigated. Fluent model (version 6) is used and water surface is simulated using volume of fraction (VOF) method. Comparison of numerical and experimental results show good agreement.

The use of a variety of bridge improvement and reinforcement methods has made significant progress in recent decades. Before strengthening, a study of the bridge should be done on how and in what way the useful life of the bridge can be extended. In this study, the seismic behavior of reinforced reinforced concrete columns was evaluated and compared with the distance of metal jacket and concrete jacket with dimensions of 3. 5 x 3. 5 m with reinforcement network. Models for estimating its seismic parameters were analyzed non-linearly geometric and materials. Use of concrete jacket box with dimensions of 3. 5 x 3. 5, increase energy absorption, final strength and ductility by 38, 14, 13 percent. Therefore, it can be concluded that by using a concrete jacket, the amount of items mentioned in the concrete column system can be increased.

The scour around the bridge piers causes instability of them, and without applying an appropriate solution, it eventually leads to demolition of the structure. Therefore, study on the mechanism of the occurrence of the scour and effective parameters on the amount of scour are important. This study was preformed to find the effect of bridge pier’s dimension on the scour depth. Therefore, the tests were carried out for cylindrical bridge piers with diameters of 10, 20, 30, 40, 50 and 60 mm in clear water condition with relative velocities (water velocity over scour critical velocity) of 0.95, 0.86, 0.76 and 0.67 in a laboratory flume. The mean size of bed particles was equal to 0.51 mm. The results showed that with an increase of 13.15 percent in relative velocity of the flow from 0.76 to 0.86 for pier with diameter of 40 mm, also with an increase of 20 percent in the pier diameter from 50 to 60 mm at the flow relative velocity of 0.95, the scour depth increased 38.8 and 10.34 percent, respectively. In addition, by analysis of the experimental results, the pier with diameter of 40 mm was an appropriate one with suitable diameter so it was proposed for the other similar experiments.

Estimating maximum scour depth is normally required in order to determine the depth of bridge piles.The present paper uses the SSIIM Software which considers flow and sediment equations in a three dimensional manner. The software models flow field around circular bridge pile by resolving Navier-Stokes three-dimensional equations and k-e method, and by temporary solution of flow field and continuity equations variations of bottom levels around bridge pile was determined. In order to verify the results of the simulated model, they were compared with those of laboratory experiments. The results indicate that the model can be used with high accuracy to simulate scour and estimating scour depth around bridge piles.

The existence of bridge pier in streamflow causes a complex 3D flow formation, which also causes the scouring around bridge pier. Since rivers are usually curved, it is necessary to investigate the impact of change in flow patterns caused by passage of flow through the curve on the scouring around bridge pier. By developing Computational Fluid Dynamics (CFD), there is a possibility to simulate the flow pattern around the bridge piers. Therefore, the purpose of this research is modeled a 3D flow stream near the bridge piers in a curved channel. For this purpose a fluent model software was employed, and solved by stream equations using finite volume method of centralism. For discretization of Navier Stocks equation, three turbulence models of K-e, K-w, and RSM were used. In order to consider free surface, Fluid Volume Method was applied. The numerical model was validated with measured experimental data around the bridge piers in the meandering flume with 5 sequential curve paths. The results showed that the RSM turbulence model performed well compared to the other two models. When comparing the flow of upstream to downstream of bridge piers it can be observed that the placement of bridge piers in the middle of curved shape channel may lead secondary flow towards the inner curve of a channel. Also, the resulted vortex continues with a 150 degree curve.