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Application of Adhesives in Steel Bridges

Description:

The potential use of adhesives in new construction in both in the shop and in the field is to be investigated. The possible benefits include reduced number of mechanical fasteners and prevention of crevice corrosion at the edges of the connection. Adhesives are widely used in other industries including aerospace, wind turbine blades, and light metal products. High strength bolts would be used in predrilled holes to clamp the pieces together after application of the adhesive. Epoxy adhesives with a shear strength of 3 ksi are available which can provide the friction shear strength of an A325 bolt. These hybrid bolt and adhesive joints could be readily used for shop connections and provide a slip capacity equal to a fully pretension bolt without the concern for proper bolt tensioning. Curing time of the adhesive and the effect of temperature upon the rate of curing rate are important parameters upon the ability of the adhesive to be used in the uncontrolled temperature of a fabricating shop or in the field.

Objective:

Evaluation of the use of structural adhesives in structural steel connections. The research should evaluate the shear strength of the adhesives, their creep behavior at expected steel temperatures in the bridge, curing of adhesives after joint assembly, and surface finish of the steel required to develop the shear performance. In addition, the long term performance of the adhesives under freeze-thaw conditions and exposure to deicing chemicals needs to be evaluated.

Benefits:

This initial project will provide the basis for the introduction of structural adhesives in bridge structures. Structural adhesives have been implemented in other industries due to their high strength and durability. A hybrid joint using bolts and adhesives will provide increased slip resistance, prevention of crevice corrosion at the edges of the connected material, and elimination of bolts added to the connection to satisfy maximum bolt spacing for corrosion protection.

Related Research:

Current research in this area is predominantly related to lighter construction and structural composites. The proposed research will utilize the knowledge gained in other industries and evaluate the adhesives in our construction and exposure environment.

Tasks:
  1. Literature Survey and Selection of Candidate Adhesives for Evaluation

  2. Short term shear tests to determine shear strength of adhesives with and without a tightened bolt.

  3. Creep and exposure testing to determine the long term performance of the connection.

  4. Design guides for prototype structural applications.
Implementation:

The results of the study will provide the knowledge to begin the use of adhesives in steel bridge connections. It is expected that the initial use will be in shop connection of bracing and cross frame members. Further studies to develop design guides to predict the strength of large size bridge hybrid bolt-adhesive connections will be required.

Relevance:

This work would be relevant to the entire bridge design community.

Sponsoring Committee:AKB20, Steel Bridges
Research Period:12 - 24 months
Research Priority:High
RNS Developer:Karl Frank, Consultant to NSBA
Source Info:The aerospace, wind turbine, and automotive industries are active users of adhesives. The research performed and the products developed for these industries are a valuable source of information.
Date Posted:07/16/2019
Date Modified:04/09/2020
Index Terms:Adhesives, Steel bridges, Structural connection, Shear strength, Creep, Finishes, Freeze thaw durability, Deicing chemicals,
Cosponsoring Committees: 
Subjects    
Construction
Design
Materials
Bridges and other structures

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