Pier Spacing Research Articles

Clear-water local scouring around three piers in a tandem arrangement

Experiments of local scouring around three piers were carried out under steady clear-water conditions. We investigated the role of pier spacing and flow rate in scour depth and progression. The scour-hole depth around the upstream pier was the same as that for single piers and independent of pier spacing. The scour behavior of the middle and downstream piers progressed through a synchronous scouring region, a transition region, and a radical deviation region as the fluid velocity increased. The critical velocity from the synchronous scouring region to the transition region for the middle and downstream piers was the same, which linearly increased with pier spacing. The degree of deviation in the radical deviation region for the middle and downstream piers was dependent on the pier spacing. The critical velocity from the transition region to the radical deviation region for the middle pier increased with the pier spacing. When the spacing was larger than 11 times the diameter of a pier, the scour depths of the three-pier configuration were the same as for the single piers, which indicates the limit of inter-pier fluid–structure interaction. Finally, the data from this study are used to derive adjustment factors to predict the local scour depth around three piers.

Scour hole characteristics of two unequal size bridge piers in tandem arrangement

The work reported herein is concerned with a carefully controlled extensive experimental investigation of the effect of mutual interference of a group of two bridge piers of unequal sizes placed in tandem arrangement at varied pier spacing under steady, uniform flow clear water scour conditions on scour hole characteristics. The data on various characteristics of scour holes developed around the piers are collected and analyzed. Present study reveals considerable mutual interference effect on scour hole characteristics which may lead to bridge failure, if pier group effect is ignored and bridge piers are designed merely as an isolated pier.

SCOUR INVESTIGATION AROUND SINGLE AND TWO PIERS SIDEBYSIDE ARRANGEMENT

Laboratory experiments concerning scour development around single and two piers side by side arrangeme nt have been conducted in order to provide a comparison of scour depths and p atterns. The experiments are carried out under unid irectional currents of clearwater scour conditions. A variety of conditions inc luding different flow depths, pier diameters and pi er spacing are considered to have significant influence on the development of the pot ential scour hole. The research on local scour arou nd single and two piers side by side arrangement are studied by using a 15.24 m lon g, 0.46 m wide and 0.4 m deep flume in the Hydrauli cs and Hydrology Laboratory, Universiti Teknologi Malaysia (UTM).Exp erimental results describing the scour-hole depths and patterns are discussed. The results show that the magnitude and extent of t he scour depth depends directly on pier size, pier spacing and flow condition. Piers, which are larger in diameter, produced great er scour depth. It also shows that by increasing th e pier spacing, the scour depth around two piers decreases and closes to values of single pier. The two piers act as an obstruction wh ich disturbed the flow field and caused large turbulence levels to be generated. The reby, a further increase in the scouring velocity iproduced giving relatively higher scour depth values. The prime factors govern ing the local scouring process associated with pier s are pier spacing, horseshoe vortex, reinforcing and sheltering. The results sho w that good agreement with previous study where the down flow causes of increased scour for a single pier case. Meanwhile, the horses hoe vortex appears to be the main cause of scour in the case of two piers side by side arrangement.

Flow Field Around Single and Tandem Piers

The present study provides a comparison between the flow pattern around two circular piers in tandem and a single pier set up on a moderately rough flat bed in a laboratory flume. Velocities are measured by an Acoustic Doppler Velocimeter (ADV). The contours of the time-averaged velocity components, Reynolds shear stresses, turbulence intensities and turbulence kinetic energy at different planes are presented. Streamlines and vectors are used to study the flow features. The analysis of power spectra around the piers is also presented. The results show that the presence of downstream pier changes the flow structure to a great extent, particularly in the near-wake region. Within the gap between the two piers, a stronger and substantial upflow is shaped. However, a weaker transverse-deflection is formed in comparison with that in the single pier. Near the bed, the velocity of flow approaching the downstream pier decreases to 0.2–0.3 times of the approach mean velocity (U 0) due to the sheltering effect of the upstream pier. In the wake of downstream pier, the flow structure is completely different from the one in the wake of single pier. In comparison with the single pier, the values of turbulence kinetic energy and turbulence intensities show a considerable decrease around the tandem piers. In tandem piers, the high values of turbulence characteristics are found near the downstream pier. There is a recirculation zones just upstream of the sheltered pier close to the bed and another behind that pier near the free surface. The results show a decrease in the strength of vortical structure in the wake of tandem piers in comparison with single pier. It is shown that the formation of flow with different Reynolds number along the flow depth due to the effect of bed roughness, as well as pier spacing, can influence the type of flow regime of tandem case. In addition to enhancing the flow structure indulgence, the present detailed measurements can also be used for verification of numerical models.

Review: New Approaches to Medieval Architecture, by Robert Bork, William Clark, and Abby McGehee

Robert Bork, William Clark, and Abby McGehee, editors. New Approaches to Medieval Architecture AVISTA Studies in the History of Medieval Technology, Science, and Art, Volume 8. Farnham, England, and Burlington, VT: Ashgate, 2011, 258 pp., 66 b/w illus. $119.95 (cloth), ISBN 9781409422280. New Approaches to Medieval Architecture bears a somewhat misleading title, as the methodologies employed by the authors are not new in the broad sense of the term; most papers included in this collection—drawn from conference presentations at the International Medieval Congress between 2007 and 2009—could be described as positivist, relying on site-oriented, object-based examination. But if the methods themselves are not entirely new, the problems to which they are applied—and the means by which they are applied—stretch the boundaries of the field, questioning standard truths and opening exciting directions of exploration. The authors, who include both emerging and senior scholars, demonstrate how fresh eyes and new technology can upend even the most deeply-entrenched conclusions. The editors organized the papers under four headings: master narratives of the field, patronage and institutional context, workshop practices, and new technology. Nicola Camerlenghi begins part one with “The Longue Duree and the Life of Buildings,” questioning our emphasis on a building’s moment of conception as the moment deserving study. He instead introduces the idea of four-dimensional study to medieval buildings, noting that time-based study can reveal changing attitudes about the past, the effects of the past on the present, and the lasting significance of sites or structures. His work is followed by that of Vasileios Marinis, who challenges the notion that liturgical function determined form in the ground plans of Byzantine churches, suggesting instead a more complex scenario accounting not only for function but for convenience, aesthetics, practicality, and change at each site. Next, Ellen Shortell convincingly reinterprets documentary sources for the construction of Saint-Quentin’s Gothic choir and supports her position with an analysis of the stained glass, concluding that Saint-Quentin, usually described as an imitative offshoot of Chartres, is instead its contemporary. Along the way, Shortell highlights the difficulty of using assumptions about an …

Effect of Pier Spacing on Scour Around Bridge Piers

Small scale experiments were designed to investigate effects of lateral spacing between bridge piers on scour depth. The scouring process is effected by two processes: (1) The interaction of the horseshoe vortices around the bases of the piers; and (2) the acceleration of flow between the piers. Equations are derived for clear water scour, for one set of pier geometrics, one water depth and one sediment type.

The Effect of Elevated Guideway Construction Tolerances on Vehicle Ride Quality

In this paper the ride quality of a vehicle traversing an elevated guideway is related directly to guideway construction tolerances and design parameters. Moreover, the construction tolerances are modeled in terms familiar to a guideway contractor. The tolerances modeled for an elevated, two-span semicontinuous, concrete guideway are: surface finish, camber deviations, pier survey errors, and pier settlement. The major design parameters relating to live-load deflection, stiffness (material and cross-section), and pier spacing are included. A general technique is presented for relating these tolerances to vehicle ride quality by means of a digital computer simulation. Various ride quality criteria are considered, including rms acceleration, acceleration spectral density, acceleration frequency decomposition, and a deterministic state space boundary. Numerical results are presented for a particular vehicle-guideway configuration and as such are valid only for the system considered. It is shown that for this system, equivalent ride quality can be maintained while adjusting the various construction tolerances. This trade-off capability allows the contractor to choose the least costly combination of tolerance parameters.