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. Bridge bearings types of bearings for bridge structures. The purpose of a bearing is to allow controlled movement and thereby reduce the stresses involved. Before going into specific topics related to beam bracing, some important concepts developed for column bracing. Under nchrp project 1051, the university of texas at austin addressed these concerns.
Definition of design requirements define the direction and magnitude of the applied loads, translations and rotations using the aashto lrfd bridge design specifications. 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. Steel bridge bearing design and detailing guidelines section 1 elastomeric bearings 1. The buckling modals and critical buckling load of truss. Implementation of lrfd geotechnical design for bridge. If tests that are accurate and essential predictors of.
This website and documents are provided for use by persons outside of the kansas department of transportation as. 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. Sole plate the sole plate is a steel plate that is attached to the bottom of girders or beams or truss chords. 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. Ccls quality management system complies with en iso 9001. Information on bridge articulation is given in gn 1. Stability of existing bridges improved by structural. Bridge bearings and stability journal of structural.
Delivering quality at every stage, all bridge bearings are designed individually to exacting standards using high specification materials from approved sources. 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. Introduction elastomeric bearings introduced nearly 60 years ago, laminated steelelastomer bearing pads are now in. At the fixed end, there is no rocker, as the bearing is rigidly attached to a masonry plate. Steel bridge bearing selection and design guide steel building. Condition assessment of existing bridge structures gdot project no. A bridge bearing is a superstructure element that provides an interface between the. 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. General in the majority of steel bridges it is convenient to. To insure stability, total bearing thickness should not exceed the smaller of l3, b3 or. The obstacle to be crossed may be a river, a road, railway or a valley. 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.
Three major types of bridge bearings are presented. The latest design software and fea is used to optimise bearing design for efficiency and cost. Course title engineering for structural stability in. Inoperable roller nests and seismically vulnerable. Analysis of bridge bearings and stability international journal of. Bearing a bridge bearing consists of four basic elements. 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. This module provides practical information for efficient bearing design and. Bridge bearings types of bearings for bridge structures and.
Steel bridge bearings may be divided into three general types. Chapter 9 embankments washington state department of. Bearing used in the construction of bridge structure is divided into two major categories namely expansion bearings and fixed bearings. Stage 4 completed structure once the deck has hardened, the steel bridge girders are composite with the deck and stability of. 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. Under nchrp project 1051, the university of texas at austin addressed these. W, stability shall be investigated by interchanging l and w in eqs. Pdf analysis of the large deformation stability of. The proportion of horizontal to vertical load is increasing due to the current trend toward continuous, joint.
Fhwa bridge inspection manual section 9 bridge bearings. Care should be taken to ensure that the pier is designed for the resulting. Global stability problems have occurred primarily on bridge widening projects where a few girders are added to an existing bridge system. 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. The former permits both translational and rotational movements whereas the latter allow rotational and limited translational movements. This website and documents are provided for use by persons outside of the kansas department of transportation as information only. Trbs second strategic highway research program shrp 2 report s2r19arw2. 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. Kansas department of transportation bridge construction manual version 107 kdot bridge section 11. In addition, they are easily installed and maintenancefree.
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. The required passage may be for a road, a railway, pedestrians, a canal or a pipeline. The footing and bridge seat are solidly founded and the bridge superstructureend diaphragm expands and contracts over the bridge seat. 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. Latest developments and applications for bridge bearings summary. 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. Engineering for structural stability in bridge construction 2. Bridge bearings and stability transportation research board. Table 61 design forces on bearings of interior girders at the intermediate pier. Fhwa bridge inspection manual section 9 bridge bearings 2012 instructor. Pot bearings for bridges and structures plain bearing products.
Bridge bearing fuse systems home northeastern university. 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. Information on the attachment of bearings is given in gn 2. Rp05 01 report of task 1 appraisal of stateoftheart of bridge condition assessment prepared for georgia department of transportation by naiyu wang bruce r. Design step 6 design of bearings prestressed concrete. Factors that affect bracing requirements will be discussed and design methods proposed which are illustrated by design examples. Check global stability at the service limit state determine the nominal geotechnical bearing resistance at the service limit state. W plan dimension of the bearing parallel to the axis of rotation under consideration generally parallel to the. However, bridge bearings could create more problems for the bridge structure than it solves if not properly understood, especially. These horizontal forces require that bearing stability be investigated. 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. Examples of this sort of direction are axial ball and roller 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.
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. The designer must determine which bearing type is best suited to cost effectively accommodate the design requirements. Furthermore, if the horizontal shear force is greater than onefifth of the minimum permanent dead load, the bearing is subject to slip and must be secured against. The information included is intended to permit efficient fabrication, installation, and maintenance of these bearings. 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. Unit can recommend the scope of soil exploration needed and providerecommend bearing resistance, overall stability, and. A sole plate may also be embedded into the bottom flange of a prestressed concrete girder. For stability, the total thickness of the rectangular pad must not exceed onethird of the.
Possible causes of movement are thermal expansion and contraction, creep, shrinkage, or fatigue due to the properties. Analysis of the large deformation stability of elastomeric bearings. Therefore, the geotechnical designer should perform a detailed site reconnaissance. 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. There are several types of bridge bearings which have been employed in.
A bridge bearing is a component of a bridge which typically provides a resting surface between bridge piers and the bridge deck. Bridge bearings are used to transfer forces from the superstructure to the substructure, allowing the following types of movements of the superstructure. The bearing reaction at different limit states is equal to the shear at the end of span 1 as shown in tables 5. 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.
Steel bridge design handbook bearing design volume 15. The improved stability may also reduce the need for support trestles. Wisdot bridge manual chapter 27 bearings wisconsin dot. Bridge engineers today usually do not design bearings. Implementation of lrfd geotechnical design for bridge foundations. 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. Possible causes of movement are thermal expansion and contraction, creep, shrinkage, or fatigue due to the properties of the material used for the bearing. They support vertical loads with minimal compression, allow expansion and contraction of. Two levels of stability criteria, for normal conditions and for extraordinary temporary conditions, are presented.
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