Effect of Skew on Seismic Performance of Bridges with Seat-type Abutments

Effect of Skew on Seismic Performance of Bridges with Seat-type Abutments
Author: Suiwen Wu
Publisher:
Total Pages: 790
Release: 2016
Genre: Electronic books
ISBN:

It is well known that skewed bridges with seat-type abutments are more vulnerable to unseating during strong earthquakes than straight bridges of the same length, due to excessive in-plane rotation. This rotation is believed to be due to the eccentricity between centers of mass and stiffness, and abutment pounding. Despite the common occurrence of this type of damage, little experimental research on the interaction between a bridge deck and abutment has been conducted to confirm this behavior, quantify its effect, and validate numerical models. As a consequence, many design codes specify the minimum support length for skewed bridges based on engineering judgment and not on rigorous analysis. In this study, an unseating mechanism is proposed after examining the behavior of skew bridges in recent earthquakes. It is hypothesized that the obtuse corner of superstructure engages the adjacent back wall during lateral loading and the superstructure then rotates about this corner, causing large displacement at the acute corner at the other end of the span. These displacements can be large enough to unseat the deck, especially in bridges with small seats.

Modeling the Coupled Cyclic Translational and Rotational Responses of Skew Bridge Abutment Backfills

Modeling the Coupled Cyclic Translational and Rotational Responses of Skew Bridge Abutment Backfills
Author: Seyedali Nojoumi
Publisher:
Total Pages: 114
Release: 2016
Genre:
ISBN:

Abutments are bridge-supporting structures at the interface of the bridge deck and the soil embankment. During strong seismic events, longitudinal motion of the bridge causes a collision between the deck and the abutment backwall--which is lightly reinforced and is designed to break--and plastic deformations are induced in the backfill. This mechanism is intended to dissipate energy, and concentrate or limit the seismic damage to the abutments (Caltrans SDC, 2010). Reversals of inertial forces can cause the deck to unseat from the abutment, and thus, sufficient seat length is required. Seat type abutments also feature exterior shear keys that are used to counter possible transverse deck movements. They are proportioned and detailed to act as fuses that will break off under the design earthquake (Kaviani et al., 2014).

Passive Force on Skewed Bridge Abutments with Reinforced Concrete Wingwalls Based on Large-scale Tests

Passive Force on Skewed Bridge Abutments with Reinforced Concrete Wingwalls Based on Large-scale Tests
Author: Kyle M. Smith
Publisher:
Total Pages: 186
Release: 2014
Genre: Electronic Dissertations
ISBN:

A comparison of passive force per unit width suggests that MSE wall abutments provide 60% more passive resistance per unit width compared to reinforced concrete wingwall and unconfined abutment geometries at zero skew. These findings suggest that changes should be made to current codes and practices to properly account for skew angle in bridge design.

Evaluation of Passive Force on Skewed Bridge Abutments with Large-scale Tests

Evaluation of Passive Force on Skewed Bridge Abutments with Large-scale Tests
Author: Aaron Kirt Marsh
Publisher:
Total Pages: 176
Release: 2013
Genre: Electronic dissertations
ISBN:

Accounting for seismic forces and thermal expansion in bridge design requires an accurate passive force versus backwall deflection relationship. Current design codes make no allowances for skew effects on the development of the passive force. However, small-scale experimental results and available numerical models indicate that there is a significant reduction in peak passive force as skew angle increases for plane-strain cases. To further explore this issue large-scale field tests were conducted at skew angles of 0°, 15°, and 30° with unconfined backfill geometry. The abutment backwall was 11 feet (3.35-m) wide by 5.5 feet (1.68-m) high, and backfill material consisted of dense compacted sand. The peak passive force for the 15° and 30° tests was found to be 73% and 58%, respectively, of the peak passive force for the 0° test which is in good agreement with the small-scale laboratory tests and numerical model results. However, the small differences may suggest that backfill properties (e.g. geometry and density) may have some slight effect on the reduction in peak passive force with respect to skew angle. Longitudinal displacement of the backfill at the peak passive force was found to be approximately 3% of the backfill height for all field tests and is consistent with previously reported values for large-scale passive force-deflection tests, though skew angle may slightly reduce the deflection necessary to reach backfill failure. The backfill failure mechanism appears to transition from a log spiral type failure mechanism where Prandtl and Rankine failure zones develop at low skew angles, to a failure mechanism where a Prandtl failure zone does not develop as skew angle increases.

Seismic Design and Retrofit of Bridges

Seismic Design and Retrofit of Bridges
Author: M. J. N. Priestley
Publisher: John Wiley & Sons
Total Pages: 704
Release: 1996-04-12
Genre: Technology & Engineering
ISBN: 9780471579984

Because of their structural simplicity, bridges tend to beparticularly vulnerable to damage and even collapse when subjectedto earthquakes or other forms of seismic activity. Recentearthquakes, such as the ones in Kobe, Japan, and Oakland,California, have led to a heightened awareness of seismic risk andhave revolutionized bridge design and retrofit philosophies. In Seismic Design and Retrofit of Bridges, three of the world's topauthorities on the subject have collaborated to produce the mostexhaustive reference on seismic bridge design currently available.Following a detailed examination of the seismic effects of actualearthquakes on local area bridges, the authors demonstrate designstrategies that will make these and similar structures optimallyresistant to the damaging effects of future seismicdisturbances. Relying heavily on worldwide research associated with recentquakes, Seismic Design and Retrofit of Bridges begins with anin-depth treatment of seismic design philosophy as it applies tobridges. The authors then describe the various geotechnicalconsiderations specific to bridge design, such as soil-structureinteraction and traveling wave effects. Subsequent chapters coverconceptual and actual design of various bridge superstructures, andmodeling and analysis of these structures. As the basis for their design strategies, the authors' focus is onthe widely accepted capacity design approach, in which particularlyvulnerable locations of potentially inelastic flexural deformationare identified and strengthened to accommodate a greater degree ofstress. The text illustrates how accurate application of thecapacity design philosophy to the design of new bridges results instructures that can be expected to survive most earthquakes withonly minor, repairable damage. Because the majority of today's bridges were built before thecapacity design approach was understood, the authors also devoteseveral chapters to the seismic assessment of existing bridges,with the aim of designing and implementing retrofit measures toprotect them against the damaging effects of future earthquakes.These retrofitting techniques, though not considered appropriate inthe design of new bridges, are given considerable emphasis, sincethey currently offer the best solution for the preservation ofthese vital and often historically valued thoroughfares. Practical and applications-oriented, Seismic Design and Retrofit ofBridges is enhanced with over 300 photos and line drawings toillustrate key concepts and detailed design procedures. As the onlytext currently available on the vital topic of seismic bridgedesign, it provides an indispensable reference for civil,structural, and geotechnical engineers, as well as students inrelated engineering courses. A state-of-the-art text on earthquake-proof design and retrofit ofbridges Seismic Design and Retrofit of Bridges fills the urgent need for acomprehensive and up-to-date text on seismic-ally resistant bridgedesign. The authors, all recognized leaders in the field,systematically cover all aspects of bridge design related toseismic resistance for both new and existing bridges. * A complete overview of current design philosophy for bridges,with related seismic and geotechnical considerations * Coverage of conceptual design constraints and their relationshipto current design alternatives * Modeling and analysis of bridge structures * An exhaustive look at common building materials and theirresponse to seismic activity * A hands-on approach to the capacity design process * Use of isolation and dissipation devices in bridge design * Important coverage of seismic assessment and retrofit design ofexisting bridges

High Skew Link Slab Bridge System with Deck Sliding Over Backwall Or Backwall Sliding Over Abutments

High Skew Link Slab Bridge System with Deck Sliding Over Backwall Or Backwall Sliding Over Abutments
Author: Haluk Aktan
Publisher:
Total Pages: 0
Release: 2011
Genre: Concrete bridges
ISBN:

A new bridge design and construction trend to help improve durability and rideability is to remove expansion joints over piers and abutments. One approach to achieve this is to make the deck continuous over the piers by means of a link slab while the girders remain simply supported. The need to implement link slabs is indicated by AASHTO LRFD section 2.5.2.4 which requires using a minimum number of expansion joints to improve rideability. Further, due to durability concerns associated with bridge deck joints, it is preferred to have a least number of joints or develop jointless decks. The expansion joints over the abutments can be removed by one of three methods: deck sliding over back wall, semi-integral abutments, and integral abutments. This results in expansion joints at either or both ends of the approaches. The design concerns other than link slab include backwall and wing-wall design and bearing movement. The behavior of a jointless bridge brings about many challenges to bridge designers. The complexity is augmented when skew is involved. This report complements an earlier report based on previous research on Combining Link Slab, Deck Sliding Over Backwall and Revising Bearings (Aktan et al., 2008) where the behavior of straight and moderately skew (skew 200) link slab bridges were investigated and design recommendations were developed. This report describes the behavior and performance of high skew (skew 200) jointless bridges with link slabs and two abutment configurations. These abutment configurations are deck sliding over backwall and backwall sliding over abutments (i.e. semi-integral abutments). Four tasks were performed in this project. The first task was to review and synthesize information related to the behavior, performance, design, and analysis of skew bridges. The second task was field assessment of skew bridge behavior under static truck loads and thermal loads. The third task was analytical and numerical analysis of skew link slabs. The final task was analytical and numerical analysis of skew sliding deck over backwall systems and semi-integral abutments. Design recommendations are developed based on literature, field assessment data analysis, finite element modeling, and subsequent simulations of the numerous models developed in this project. One recommendation deals with the skew link slab design and the remaining recommendations are for bearing selection and selection and design of a transverse restraint system at abutments of skew link slab bridges.