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The structural design of the bolted fiber reinforced polymer elements is typically governed by the capacity of the joint rather than the fiber reinforced polymer member, while the joint capacity is typically governed by the shear strength of the fiber reinforced polymer. Here, the possibility of improving the shear strength of bolted joints is investigated in the unidirectional glass fiber reinforced polymer plates by incorporating the multiwalled carbon nanotubes during glass fiber reinforced polymer fabrication. Glass fiber reinforced polymer double-shear bolted lap joints were fabricated using up to 1.0 wt% multiwalled carbon nanotubes–-epoxy nanocomposites. Finite element modeling using multicontinuum theory and element deletion techniques was performed to explain the joint behavior. The experimental investigations show that incorporating multiwalled carbon nanotubes improved the shear strength, ductility, and energy absorption significantly. Microstructural analysis proves that a chemical reaction between multiwalled carbon nanotubes and epoxy improves the shear strength of the matrix.

Glass fiber-reinforced polymer (GFRP) reinforcing bars have relatively low shear strength, which limits their possible use in civil infrastructure applications with high shear demand, such as concrete reinforcing dowels. We suggest that the horizontal shear strength of GFRP bars can be significantly improved by nanomodification of the vinyl ester resin prior to pultrusion. The optimal content of functionalized multiwalled carbon nanotubes (MWCNTs) well dispersed into the vinyl ester resin was determined using viscosity measurements and scanning electron micrographs. Longitudinal tension and short beam shear tests were conducted to determine the horizontal shear strength of the nanomodified GFRP reinforcing bars. While the tensile strength of the GFRP reinforcing bars was improved by 20%, the horizontal shear strength of the bars was improved by 111% compared with the shear strength of neat GFRP bars pultruded using the same settings. Of special interest is the absence of the typical broom failure observed in GFRP when MWCNTs were used. Differential scanning calorimetry measurements and fiber volume fraction confirmed the quality of the new pultruded GFRP bars. Fourier-transform infrared (FTIR) measurements demonstrated the formation of carboxyl stretching in nanomodified GFRP bars, indicating the formation of a new chemical bond. The new pultrusion process using nanomodified vinyl ester enables expanding the use of GFRP reinforcing bars in civil infrastructure applications.

Prefabricated concrete bridge deck panels are utilized in Accelerated Bridge Construction (ABC) to simplify bridge deck construction. Concrete with good bond and shear strength as well as excellent flowability is required to fill bridge deck closure joints. This paper discusses the use of polymer concrete (PC) for bridge deck closure joints in ABC. PC produced using poly methyl methacrylate and standard aggregate was tested. Test results of PC are compared to Ultra-High Performance Concrete (UHPC). Development length, lap splice length and shear strength of unreinforced PC were tested. It is shown that PC has a development length of 3.6 to 4.1 times the reinforcing bar diameter that is close to one-half the development length of 6 to 8 times the bar diameter required with UHPC. PC also showed a shorter splice length compared with that reported for UHPC. Finally, unreinforced PC showed shear strength that is twice that of UHPC. It is evident that using PC in bridge deck closure joints in ABC can improve constructability and provide cost-savings and eliminate reinforcing bar congestion.

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