Experimental and numerical analysis of preload in Extended Hollo-Bolt blind bolts

Adequate initial bolt preload is necessary to ensure the strength and stiffness of bolted connections. In this study, an experimental torque control method was used determine relationship between tightening nine Extended Hollo-Bolt (EHB) blind connections Concrete-Filled Steel Hollow Sections (CFSHS). order obtain EHB nut factors, which allow calculate level for any value applied torque, versus curves were drawn based on results curve fitting carried out. Bolt relaxation also recorded a period 7 days while concrete hardening occurred. Additionally, detailed 3D Finite Element (FE) model stage established. The numerical show that factor higher than standard bolts not affected by presence during stage. friction coefficients proposed as well equation calculating residual EHB.