Analysis of the large deformation stability of elastomeric bearings. Implementation of lrfd geotechnical design for bridge. Bearing technologies pot bearings in most concrete and steel structures accommodation must be made for relative movement between structural members in order to avoid the buildup of dangerous. A tapered bearing plate is almost always required between the upper surface of the bearing and the underside of the flange so that the bearing remains horizontal. Chapter 9 embankments washington state department of. Two levels of stability criteria, for normal conditions and for extraordinary temporary conditions, are presented. The former permits both translational and rotational movements whereas the latter allow rotational and limited translational movements. Kansas department of transportation bridge construction manual version 107 kdot bridge section 11. Introduction elastomeric bearings introduced nearly 60 years ago, laminated steelelastomer bearing pads are now in service in tens of thousands of bridges and similar structures throughout the world. This website and documents are provided for use by persons outside of the kansas department of transportation as. Possible causes of movement are thermal expansion and contraction, creep, shrinkage, or fatigue due to the properties of the material used for the bearing.
Case study of long span steel bridge stability during design and construction keywords stability, analysis, overstress, deflection, bracing, diaphragm, cross frames, shoring tower, holding crane abstract replacement of a bridge over the lehigh river in jim thorpe, pa required long spans 335 ft maximum and. Design step 6 design of bearings prestressed concrete. Table 61 design forces on bearings of interior girders at the intermediate pier. Global stability settlement amounts and rates spreads versus deep foundations lateral resistances special provisionsmaterials specifications construction considerations water control surface preparation temporary walls vibrations geotechnical instrumentation needed. The latest design software and fea is used to optimise bearing design for efficiency and cost. The improved stability may also reduce the need for support trestles. The proportion of horizontal to vertical load is increasing due to the current trend toward continuous, joint.
Course title engineering for structural stability in. The information included is intended to permit efficient fabrication, installation, and maintenance of these bearings. Bridge bearings types of bearings for bridge structures. General in the majority of steel bridges it is convenient to. It is noted that stability is a part of bridge bearing design, and that bearings must be designed and detailed to meet required vertical and horizotal load capacities, rotation limits, and anchor bolt clearances. For stability, the total thickness of the rectangular pad must not exceed onethird of the. Pot bearings for bridges and structures plain bearing products.
Bearing used in the construction of bridge structure is divided into two major categories namely expansion bearings and fixed bearings. However, bridge bearings could create more problems for the bridge structure than it solves if not properly understood, especially. The purpose of a bearing is to allow controlled movement and thereby reduce the stresses involved. Two electronic surveys were used to garner knowledge and expertise from bridge engineers, bearing manufacturers and other stake holders in the course of this study, also practical knowledge concerning various types and problems of bridge bearings, maintenance, repair and replacement, life cycle costing. A bridge bearing is a component of a bridge which typically provides a resting surface between bridge piers and the bridge deck. If tests that are accurate and essential predictors of. Bridge bearings types of bearings for bridge structures and.
Global stability problems have occurred primarily on bridge widening projects where a few girders are added to an existing bridge system. The selection of the target reliability assumes a significant amount of redundancy in the foundation system is present, which is typical for pile groups containing at least five piles in the. Steel bridge bearing design and detailing guidelines section 1 elastomeric bearings 1. Rp05 01 report of task 1 appraisal of stateoftheart of bridge condition assessment prepared for georgia department of transportation by naiyu wang bruce r. Information on the attachment of bearings is given in gn 2. Information on bridge articulation is given in gn 1. The goal of this training course is to assist dots in the successful development of lrfd design guidance for bridge foundations basedthe 2010 on aashto lrfd bridge design specifications and with. Check global stability at the service limit state determine the nominal geotechnical bearing resistance at the service limit state. Therefore, the geotechnical designer should perform a detailed site reconnaissance. The obstacle to be crossed may be a river, a road, railway or a valley. Steel bridge design handbook bearing design volume 15. This module provides practical information for efficient bearing design and.
The footing and bridge seat are solidly founded and the bridge superstructureend diaphragm expands and contracts over the bridge seat. Van lund, washington state department of transportation the washington state department of transportation wsdot has removed and replaced nonfunctioning bridge bearings to extend the service lives of existing bridges. Stability of existing bridges improved by structural. Sole plate the sole plate is a steel plate that is attached to the bottom of girders or beams or truss chords. Three major types of bridge bearings are presented. Condition assessment of existing bridge structures gdot project no. Engineering for structural stability in bridge construction 2. As all the loads from the superstructure are transferred through the bearing and the movement is also controlled, albeit being a small item in the overall bridge. The bearing reaction at different limit states is equal to the shear at the end of span 1 as shown in tables 5.
Bridge articulation and bearing specification from articulation is the term for the configuration of bridge supports and choice of structural bearings that provides the necessary restraints to the superstructure whilst at the same time providing freedom to some displacements and rotations in order to avoid unnecessary. To insure stability, total bearing thickness should not exceed the smaller of l3, b3 or. A bridge bearing is a superstructure element that provides an interface between the. Introduction elastomeric bearings introduced nearly 60 years ago, laminated steelelastomer bearing pads are now in. Steel bridge bearings may be divided into three general types. Unit can recommend the scope of soil exploration needed and providerecommend bearing resistance, overall stability, and.
Before going into specific topics related to beam bracing, some important concepts developed for column bracing. There are several types of bridge bearings which have been employed in. Under nchrp project 1051, the university of texas at austin addressed these concerns. A steel rocker bearing consists of a pinned joint to accommodate rotation and a rocker to accommodate longitudinal movement at the expansion end of the structure. At the fixed end, there is no rocker, as the bearing is rigidly attached to a masonry plate. Pdf analysis of the large deformation stability of. Trbs second strategic highway research program shrp 2 report s2r19arw2.
Bridge bearing fuse systems home northeastern university. Bridge engineers today usually do not design bearings. Ccls quality management system complies with en iso 9001. Latest developments and applications for bridge bearings summary. Fhwa bridge inspection manual section 9 bridge bearings.
A bridge bearing is a component of a bridge transmitting the loads received from the deck on to the substructure and to allow controlled movement due to temperature variation or seismic activity and thereby reduce the stresses involved. Steel bridge bearing design and detailing guidelines introduction the purpose of this guide is to present steel bridge bearing details that are cost effective, functional, and durable. Steel bridge bearing selection and design guide steel building. Analysis of bridge bearings and stability international journal of. The buckling modals and critical buckling load of truss. To examine whether and how the seismic stability of existing bridges can be substantially improved by integrating the girder, the abutments and the backfill, a series of shaking table tests were performed in 1 g. Inoperable roller nests and seismically vulnerable. The usual arrangement is for the bridge girder to be placed with the bottom flange seated on top of the bearing and the stiffeners concentrically above the bearing.
In addition, they are easily installed and maintenancefree. W plan dimension of the bearing parallel to the axis of rotation under consideration generally parallel to the. The girders in the widening are usually isolated from the existing bridge and the unbalanced load from the overhang can cause excessive twist that intensifies the global stability of the girder system. A sole plate may also be embedded into the bottom flange of a prestressed concrete girder. Possible causes of movement are thermal expansion and contraction, creep, shrinkage, or fatigue due to the properties. Under nchrp project 1051, the university of texas at austin addressed these. W, stability shall be investigated by interchanging l and w in eqs.
Definition of design requirements define the direction and magnitude of the applied loads, translations and rotations using the aashto lrfd bridge design specifications. Dec 28, 2015 in the current study, weight bearing on the affected side in standing and the forward and backward movement range in limit of stability in a standing position were compared, and the results showed a significant effect in the unilateral bridge exercise group and statistically significant differences between the three groups. Implementation of lrfd geotechnical design for bridge foundations. Bridge bearings are used to transfer forces from the superstructure to the substructure, allowing the following types of movements of the superstructure. Delivering quality at every stage, all bridge bearings are designed individually to exacting standards using high specification materials from approved sources. This website and documents are provided for use by persons outside of the kansas department of transportation as information only. Bridge bearings and stability journal of structural. Stage 4 completed structure once the deck has hardened, the steel bridge girders are composite with the deck and stability of. Examples of this sort of direction are axial ball and roller bearings. They support vertical loads with minimal compression, allow expansion and contraction of. Bearing a bridge bearing consists of four basic elements.
It is noted that stability is a part of bridge bearing design, and that bearings must be designed and detailed to meet required vertical and horizotal load capacities. The designer must determine which bearing type is best suited to cost effectively accommodate the design requirements. Bridge bearings and stability transportation research board. The most common way to improve stability is to assemble girders into braced pairs which makes them more stable during lifting and when in place compared to a single girder. Fhwa bridge inspection manual section 9 bridge bearings 2012 instructor. Care should be taken to ensure that the pier is designed for the resulting. Bridge bearings are small integral parts of the entire bridge structure serving several purposes, such as connection, transfer of forces, allowing movements, force damping etc. Factors that affect bracing requirements will be discussed and design methods proposed which are illustrated by design examples. Wisdot bridge manual chapter 27 bearings wisconsin dot. These horizontal forces require that bearing stability be investigated. The required passage may be for a road, a railway, pedestrians, a canal or a pipeline.
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