State of Practice for the Design of Bridge Fender Systems with Polymeric Materials
Andrew J Bechtel, College of New JerseyShow Abstract
Pile supported bridge fender systems protect bridge piers located in navigable waters. Due to their resistance to the environment, polymer materials are being used to construct these fender systems. This paper evaluates the design of polymer fender systems using the AASHTO LRFD Bridge Design Specifications and other relevant national specifications. The results have shown that in the case where deflection governs the design of the fender system, shear deformations must be considered. When codes for the structural capacity of the fender materials were evaluated, the results showed that many of the materials being produced fall outside the scope of existing standards. The main breakdowns in the existing specifications occur when implementing ASTM standard tests. Namely, the AASHTO LRFD Guide Specifications for Concrete Filled FRP Tubes, and the ASCE Pre-standard for Load & Resistance Factor Design (LRFD) of Pultruded Fiber Reinforced Polymer (FRP) Structures cannot be applied to fiber reinforced polymer tubes with circular cross-sections. This occurs because flat balanced and symmetric coupons cannot be sampled from a round tube. ASTM D7258-14 Standard Specification for Polymeric Piles is based on maximum flexural stress which cannot be reliably determined for the available pile products due to their failure modes. Ultimately, a design procedure implementing tests of full-scale pile sections was presented.
Development of FRP Design Guidelines for the Wisconsin Department of Transportation
Rita Lederle, Minnesota Department of TransportationShow Abstract
Micah Brooks, Wisconsin Department of Transportation
The Wisconsin Department of Transportation (WisDOT) has begun using fiber reinforced
polymers (FRP) for repair and retrofitting of pier caps, columns, and prestressed concrete
girders. As WisDOT plans to make FRP a more common structural repair tool, formal policy
relating to FRP design needed to be developed. To determine which of the available FRP design
guidelines to adopt, a comparison of the AASHTO and ACI FRP Design Guidelines was
conducted for all common girder shapes and several material types found in Wisconsin. It was
determined that the AASHTO guide produced more conservative results in shear but the ACI
guide produced more conservative results in flexure. Based on a literature review, the
experiences of other states as determined through a survey, and the results of the design guide
comparison, recommendations for future policy are provided.
Performance Evaluation of a Reinforced Concrete Slab Bridge Retrofitted With CFRP Laminate System
Arturo Regalado, New Mexico State UniversityShow Abstract
David Jauregui, New Mexico State University
Brad Weldon, New Mexico State University
Due to a drawing oversight, a nine-span continuous reinforced concrete slab bridge on westbound Interstate I-10 near Lordsburg, New Mexico was built with only half of the required positive moment steel reinforcement. Bridge 9367, constructed in April 2006, was retrofitted with a carbon fiber reinforcement polymer (CFRP) laminate system in November 2006 to correct for this error. Diagnostic load tests were conducted before and immediately after the retrofitting of the bridge. A finite element analysis of the bridge was also conducted to evaluate the strength and serviceability of the slab bridge and to determine if the addition of the CFRP system effectively met these limit states. The addition of the CFRP to the bridge increased the rating factors to greater than the legal load limit. Before the bridge retrofit, stresses in the steel reinforcement exceeded the limits set to control excessive concrete cracking and inelastic deformations. Inclusion of the CFRP reduced these stresses but only slightly below the limits. Creep-rupture and fatigue of the CFRP were a non-issue. Two additional load tests were conducted 8 months and approximately 9 years after the retrofit. The evaluation showed that in the short-term the slab stiffness was increased with a decrease in measured strains immediately after the installation of the CFRP. However, comparison of the strains from the load tests conducted later showed that the magnitudes had greatly increased and were approximately equal to the pre-retrofit strains. Ultimately, Bridge 9367 was replaced due to the excessive cracking and large measured strains.
Tensile Behavior of Pultruded FRP Laminates with Bonded-and-Bolted Splice Joints
Hai Nguyen, Marshall UniversityShow Abstract
Wael Zatar, Marshall University
This paper presents experimental investigation on double-lap joints of grit-blasted-surface-finish FRP splice plates bonded and bolted to FRP laminates. Eighteen coupon joint specimens were tested under tensile loading with varying types of the FRP splice plates and the FRP laminates. Four types of bolts were evaluated including FRP bolts, high corrosion-resistant steel (HCRS) bolts, stainless steel (SS) bolts, and SS bolts wrapped with glass FRP (referred to as “SF” bolts). The test results indicated that the double-lap splice joints, which incorporated the HCRS bolts, epoxy adhesive, and the grit-blasted-surface-finish FRP splice plates, provided strong bonds with the FRP laminates. The grit-blasted surface finish of the FRP splice plates and the epoxy adhesive contributed to improving the joint stiffness and strength. The specimens with the FRP bolts showed brittle behavior and failed at relatively low ultimate load. The failure of these specimens were debonding of epoxy layers following by shearing of the FRP bolts. On the other hand, the specimens with the steel bolts (i.e. HCRS, SS, and SF bolts) exhibited ductile behavior and failed at much higher ultimate load than the FRP-bolt specimens. Typical failure modes of the steel-bolt specimens were fracture of the FRP laminate (resulting from fiber rupture/kink, shear-out and delamination failure of the GFRP plies, and bearing failure of FRP materials near the edge of bolt holes in the load direction), bearing failure of the FRP splice plates, epoxy debonding, and yielding of bolts. Although the FRP wraps may enhance durability of the SS bolts, the use of the SF bolts may significantly affect the failure mode of the splice joints.