Seismic Retrofitting of Bridge Abutments -Methods and Details

In bridge building, there are two types of abutments: monolithic (shown in) and seat type. The former is commonly used in the construction of short span bridges, whereas the latter is used in the construction of large span bridges. Because the backwall in the latter kind could be constructed to operate as a fuser and limit bridge pile earthquake damages, the probability of severe seismic damage is significantly higher in the monolithic type than in the seat type. The backwall damage caused by seismic loads is bearable because it will not cause the bridge to collapse completely and will protect the bridge piles from severe seismic damage.

Seismic Retrofitting of Bridge Abutments Methods

Bridge abutments can have a variety of problems during earthquakes, including insufficient seat length in seat type abutments, a large gap between the end diaphragm of the bridge superstructure and the backwall, inadequate transverse and/or longitudinal shear strength, and a vulnerable end diaphragm in monolithic abutments. As a result, the bridge must be retrofitted to eliminate these seismic hazards. The following sections go over several seismic retrofit techniques.Seismic Retrofitting of Bridge Abutments Methods Seat catchers and extenders Fill the gap between the backwall and the end diaphragm of the bridge superstructure with concrete, steel, or wood. L bracket on the superstructure soffit Vertical Pipes, Shear Keys, Large CIDH Piles, Anchor Slabs, and Shear Keys Retrofitting Bridge Abutments with Seat Extenders and Catchers.

Seat extenders are generally made of concrete or steel brackets and affixed to the existing face of abutments or caped beams to prevent bridge girders from becoming unseated during earthquakes.Concrete Seat Extender Specifications Concrete Seat Extender Details Steel Bracket Extender Specifications Steel Bracket Extender Details Extender Seat. Seat Extender Seat extender design is similar to corbel design, and there are numerous factors to consider when designing the steel that joins the seat extender to the face of the cap beam or abutment. Shear friction for vertical loads and tensile forces produced by shear forces when a bridge girder travels longitudinally, for example.

Soffit Superstructure L Bracket

To ensure an acceptable bond between existing concrete and seat extender, it is recommended to intentionally rough up the concrete face of the abutment or cap beam. If the bridge superstructure settles more than 150mm after bearing failure, a seat catcher should be installed. The goal of the catcher provision is to keep superstructure settling to a minimum of 50mm while also increasing seat width.In Missouri, USA, a Catcher is Provided for a Vulnerable Bearing.In Missouri, USA, a Catcher is Provided for a Vulnerable Bearing. Steel Girder with Catcher Beam Steel Girder Catcher Beam Seat catcher is a device that is attached to the top of the cap beam’s abutment and looks similar to a seat extender. Finally, it’s important to keep in mind that.

Filling the Gap Between the Backwall and the End Diaphragm of the Bridge Superstructure with Concrete, Steel, or Timber On rare occasions, a significant gap exists between the bridge’s backwall and end diaphragm. Because the bridge column must deflect in order to activate the back-fill soil, this could be a weak point for the bridge during earthquakes. So, because it requires the backwall and the backfill material to contribute to the reduction of seismic damages, filling this gap with concrete, steel, or timber is regarded to be a seismic retrofit approach. While this is being filled with acceptable material, it is recommended that you pay attention to the thermal motions. Blocking Abutment Abutment Blocking Soffit Superstructure L BracketIt’s the inclusion of L-shaped furniture.

Vertical Pipes, Shear Keys, Large CIDH Piles, Anchor Slabs, and Shear Keys

Driving seismic loads away from columns and footing to the abutments is the best retrofit technique for a short span bridge. This can be accomplished by strengthening or anchoring the abutment and preventing its movement during earthquakes, and as a result, abutments will be affected by the majority of loads. Seismic anchor slabs, anchor piles, vertical pipes, and shear keys are some of the techniques that can be used to modify or anchor bridge abutments. Because of the complex geometry of the bridge, it is recommended to employ either anchor piles or vertical pipes if the bridge is severely curved or skewed. There would be no force to resist this movement as the bridge rotates away from the abutment, for example.

The study discusses the development and implementation of a process for seismic retrofitting an existing multispan prestressed concrete girder bridge that calls for the employment of friction pendulum devices as an isolation system between the piers’ tops and the deck. First, the results of the current bridge’s seismic risk assessment, which was carried out using an incremental noniterative Nonlinear Static Procedure based on the Capacity Spectrum Method and Inelastic Demand Response Spectra, are explained and reviewed. The FPD devices are then dimensioned using a multilevel design method based on a suitable application of the hierarchy of strength concerns and the Direct Displacement-Based Design technique. In addition, to determine the impact of FPD nonlinear behaviour on bridge seismic response.

Seismic Retrofitting of Bridge Abutments

The vulnerability of bridges to collapse due to excessive movement at intermediate hinges and abutments has been highlighted by recent earthquakes in the United States and Japan. The efficiency of shape memory alloy restrainer bars in reducing bridge seismic vulnerability is investigated in this study. Shape memory alloy (SMA) restrainer bars are put through full-scale tests to determine their force-deformation and energy dissipation properties. With minimal residual deformation, the 25.4 mm diameter bars are subjected to cycle strains up to 8%. Nonlinear analyses of a typical multi-span simply supported bridge are used to evaluate the efficiency of SMA restrainer bars in bridges. The SMA restrainer bars work well to keep relative movement at the piers and abutments to a minimum. Furthermore, the bars are depicted to be.

There are a number of bridges that are built to code but do not take seismic considerations into account. The majority of these bridges are deemed to be poor and may require seismic upgrading. Bridges erected prior to the 1970s, whether in the United States, Japan, or Europe, were built with little or no regard for seismic needs. The majority of these bridges are supported at the abutments and pier walls by reinforced concrete bents that lack the flexibility and strength to withstand earthquakes. Aside from that, the majority of these bridges have short (6–18 m) to medium (18–90 m) spans. A short-span bridge may be constructed with timber girders or a concrete slab superstructure, but a medium-span bridge is frequently constructed with steel girders.

Methods and Details

The use of a seismic isolation device to seismically adapt an existing cable-stayed bridge was studied in this research. The bridge is located in a seismically active area. One of the bridge supports’ anchorage plates broke after the Saguenay earthquake of 1988. Several seismic isolation system configurations were examined in order to find an effective solution for seismic retrofitting the bridge in both longitudinal and transverse orientations. The bridge’s seismic behaviour was investigated using a three-dimensional model and nonlinear dynamic time-history analysis. The partial seismic isolation of the bridge resulted in an enhancement of the bridge’s seismic response in one direction only, according to the comparative performance evaluation of the five retrofitting configurations. However, the overall picture is positive.

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