Effect on Super Structure of Integral Abutment Bridge under Fixed and Pinned Pile Head Connections

Integral bridges are recommended as one of the best alternative in the construction of bridges. They are constructed without joints in superstructure and these bridges can be of single span or multi span. Typically integral bridges have stub-type abutments supported on piles and a continuous bridge deck from one embankment to the other. Failure of proper functioning of the expansion joints and abutment bearings due to various reasons leads to highly critical and serious problems. Failure to move properly due to unanticipated movements results in overstress and subsequent structural damage to the bridge elements via split and rupture of abutment bearings, abutment-rotation and abutment-overturning.An attempt is being made in this study to analyse the effect of pile head connection with abutment on super structure under DL, LL and temperature effects on integral abutment bridge by FEM analysis using SAP 2000. The study considers integral abutment bridge with pile head having fixed and pinned connection with single, two and three spans. The variation of different design parameters such as BM, SF, axial force and longitudinal fibre stresses in deck slab and BM and SF in girder bridges have been analysed and compared. It is found that, in integral abutment bridge the design parameters are affected by the pile head to abutment connection. It is found that, in case of only DL, the negative maximum end BM is reduced by 10.5% in case of single span, 28.5% in two spans integral abutment bridge and no change in three spans integral abutment bridge. However the positive BM shows an increasing trend. It is also observed that the all design parameters are reduced with increase in span numbers. On the other hand, the temperature rise enhances negative BM and decreases positive BM. Furthermore, SF in deck slab is increased by 5.9% in two spans integral abutment bridge having pile head with pinned connection but there is no change in SF is observed in single and three spans, similarly in central girder decrease and in external girder increase in SF is observed in single and two spans bridge and there is no change in three spans bridge. Also DL + temperature and DL + LL+ temperature combination with different spans in comparison with single span and in comparison with DL is studied. Keywords: Abutment, Deck, Integral Abutment Bridge, piles, pile head, Finite element method, Abutment pile head connection

End depth computation in inverted semicircular channels using ANNs

Thepaper prerfT the application ofarJ[[f6fl neur[ networ (ANN) todeter6;fl theend-depth-r;;; (EDR)for a smooth inverhfl semicirfifi-[ channel in all flowrwflJ[x (subcrxflbf[ andsuper6;flbf[[;; Theexperfi6flbf[ data wer used totrfi6 and validate thenetwor[ Insubcrfiflbf6 flow, the end depth isrflT-;- to thecrflf;-J depth, and the value of EDR is found to be 0.705for a cr7;;flb depth--diameter rpth up to 0.40, which agrhfl closely with the value of 0.695 given by Dey [Flow Meas.Instrfi6 12 (4) (2001) 253]. On theother hand, insuper;flbfxxJ flow, theempir;f6 rir;f6flbfxx for EDR and non-dimensionaldischare with the non-dimensionalstrimensi slope of the channelar established

Characteristics of Recirculation Zone Structure behind an Impulsively Started Circular Cylinder

The characteristics of the recirculation zone structure behind an impulsively started circular cylinder for Reynolds number R-e ranging from 500 to 2,000 and nondimensional time T ranging from 0.5 to 5.0 are investigated experimentally using particle image velocimetry (PIV) and flow visualization techniques. On the basis of the flow visualization pictures and velocity maps, both obtained by a reference frame with a moving coordinate system, the evolution of the recirculation zone structure is studied with special emphasis on the negative velocity subzone. The negative velocity subzone is enveloped by the boundary consisting of the zero-velocity points inside the recirculation zone, and the streamwise velocity profile inside and near the negative velocity subzone is characterized by a jetlike flow moving toward the cylinder. During the evolution of the recirculation zone, the representative dimensions of the vortical structure both in the streamwise and vertical directions, including the recirculation zone length and the center-to-center distance between two primary vortex cores, are found to increase rapidly with time. Characteristic length and velocity scales are proposed first in the literature not only to demonstrate the similarity profile for streamwise velocity within and near the negative velocity subzone, but also to exhibit the similarity for geometric shape of the negative velocity subzone via the ratio of the width of the negative velocity subzone (i.e., the vertical distance between two zero-velocity points) to the center-to-center distance between two primary vortex cores. The very important observation is that the similarities of velocity profile and geometric shape represent promising self-preservation for the jetlike flow enclosed by the zero-velocity points forming the boundary of the negative velocity subzone. In addition, time variation of the nondimensional circulation of two primary vortices in the recirculation zone is studied and found to increase with an increase in the nondimensional time. DOI: 10.1061/(ASCE)EM.1943-7889.0000314. (C) 2012 American Society of Civil Engineers

ON THE FLOW STRUCTURES UNDER A PARTIALLY INUNDATED BRIDGE DECK

This paper presents the flow structure under a partially inundated bridge deck measured by using particle image velocimetry (PIV) and flow visualization techniques. The approaching flow was subcritical having Froude number Fin the range 0.12 similar to 0.55. The proximity ratio P-r(= ratio of clearance below the bridge deck h to the total depth of deck D) was varied from 0.57 to 2. Depending upon the Froude number F and proximity ratio P-r, four types of flow structures under the bridge deck were recognized. In flow Type I, the water surface elevation on the downstream side of bridge deck is slightly lower than the counterpart on the upstream side, and the shear layer formed at the bottom of upstream girder continuously fluctuates and touches soffit of all girders. In the case of flow Type II, the water surface on downstream side of bridge deck is lower than that on the upstream side and the shear layer originating from the upstream girder impinges near the third cavity between girders. However, in both the cases, the cavities between the girders are completely occupied by vortices. On the contrary, in the cases of flow Type III and flow Type IV, the flow is separated from the upstream girder edge. However, in flow Type III, the separated flow impinges on successive girders and cavities are partially filled by water; while in flow Type IV, the flow is totally separated from the deck bottom like orifice flow. The phenomena of vortex formation within the cavities are discussed for the cases of flow Type I and flow Type II. Also, for the vertical distribution of mean streamwise velocity in the shear layer below bridge deck, the nonlinear regression equations are developed. Using the distributions of measured mean streamwise velocity within the shear layer below the bridge deck at different streamwise distances, the similarity profile is obtained. The mean velocity deficit (u(sl) - u(su)) and representative thickness b(s) are considered as the appropriate characteristic velocity and length scales for developing similarity profile. The proposed characteristic scales provided unique similarity profiles having promising regression coefficient. The similarity profile proposed is suitable for more general case of bridge deck having different bridge girders and even for rectangular block without girder. Further, the turbulence characteristics for the flow below the bridge deck are also presented

Characteristics of Shear Layer Structure in Skimming Flow over a Vertical Drop Pool

The characteristics of shear layer structure between the sliding jet and the pool for skimming flows over a vertical drop pool were investigated experimentally, using flow visualization technique and high speed particle image velocimetry. Four series of experiments having different end sill ratios (h/H=0.12, 0.43, 0.71 and 1.0, where h=end sill height and H=drop height) with various approaching flow discharges were performed to measure the detailed quantitative velocity fields of the shear layer. The mean velocities and turbulence properties were obtained by ensemble averaging the repeated measurements. From the velocity profiles, it is found that the growth of the shear layer in the downward direction as the jet slides down the pool represents the momentum exchange. Analyzing the distribution of measured velocity, the similarity profile of the mean velocity at different cross sections along the shear layer was obtained. The proposed characteristic scales provided unique similarity profiles having promising regression coefficient. The selection of these characteristic scales is also discussed. Further, the spatial variations of mean velocity profiles, turbulence intensities, in-plane turbulent kinetic energy, and Reynolds shear stress were also elucidated in detail. The imperative observation is that the Reynolds shear stress dominates the major part along the shear layer as compared to the viscous shear stress. The study also provides an insight into the flow phenomena through the velocity and turbulent characteristics