Open-hole tension capacity of pultruded GFRP having staggered hole arrangement

• 140 open-hole tension tests on pultruded GFRP plate were conducted.
• A reduction factor, beyond the net section effect was demonstrated.
• Inclusion of s2/4g term in staggered hole capacity shown to be inappropriate.
• Maximum pitch that results in staggered behavior identified.
• Stress intensity factors experimentally determined.

The technique of using staggered bolt holes for connections is common practice in steel design since the method allows for greater design strengths from more compact connections. Steel however is a ductile isotropic material. Pultruded glass fiber reinforced polymer (GFRP), on the other hand, is a relatively brittle, often highly anisotropic material requiring different design formulations to assess its open-hole tension capacity. This study considers the development of open-hole capacity provisions and experimentally investigates the net section rupture limit state of GFRP plates having both a single gage line and staggered-hole arrangements in order to assess the open-hole capacity of pultruded GFRP plates. Tension testing of GFRP plates, having varying thickness, number of holes and hole-spacing arrangements (both staggered and non-staggered) were conducted. A significant strength reduction (beyond the net cross section area) results from the presence of a circular hole in the material, although additional holes do not compound this effect. The test results demonstrate that, unlike in isotropic materials, there is no capacity benefit from using staggered hole arrangements in GFRP plates.