Fatigue life of an anchored blind-bolt loaded in tension

This paper investigates and reports on the fatigue behaviour of a novel blind-bolt system termed the Extended Hollo-bolt (EHB). The new blind-bolt is a modified version of the standard Lindapter Hollo-bolt, and its application relates to the construction of bolted, moment-resisting connections between open profile beams and concrete-filled tubular columns. The fatigue behaviour of the system is studied on the basis of constant amplitude loading tests, with a total of 56 experiments being reported. The specimens were subjected to tensile loading for various stress ranges, with the repeated load being selected relative to the design yield stress of the blind-bolt's internal shank. The influence of testing frequency and strength of concrete infill is also examined. An analysis of the results indicates that an increase in the concrete strength can increase the fatigue life of the EHB system. Within the tested range, the failure mode of the EHB under repeated loading was found to be due to internal bolt shank fracture, a mode which is consistent with its monotonic behaviour and also comparable with standard bolt–nut–washer system behaviour. The experimental results (S–N data) were further compared with the Eurocode 3 Part 1-9 guidelines. The fatigue design strength of the anchored EHB blind-bolt is found to be adequately represented by the current specification detail Category 50 that is provided for standard bolting systems

Thermal behaviour of blind-bolted connections to hollow and concrete-filled steel tubular columns

This paper reports on the thermal analysis of blind-bolts connected to concrete filled steel tube (CFST) and hollow steel section (HSS) columns. The aim is therefore the investigation of the temperature distribution in the connected sections and the evaluation of the effects due to concrete filling and anchored bolt extension. For this purpose, experimental and numerical work was carried out. The test programme involved twelve small- scale unloaded specimens where the variables were: tube section dimensions, type of blind-bolt, and hollow or concrete filled steel tubes. Results from the experiments revealed the noteworthy effect of concrete on bolt temperature reduction, the insignificant influence of tube section dimensions, and the limited impact of embedded bolt extension. Finite element models (FEM) of connections were developed to simulate the behaviour of tested pieces. Comparison with tests allowed the calibration of thermal material properties and characteristics of heat flux in interactions. Furthermore, assessments of heat transfer problem on the simulation of small-scale pieces extended to the numerical model of the whole endplate connection between an I-beam and a tubular column. Finally, the suitability of simple methods from Eurocode 3 Part 1.2 and other references to obtain the temperature on the connection was evaluated

Advanced materials for concrete-filled tubular columns and connections

[EN] The advantages of concrete-filled steel tubular (CFST) columns are well known at room and elevated temperatures, however, beyond a certain slenderness their load-bearing capacity starts to decrease. Besides, blind-bolts represent a proper system to allow endplate bolted connections to hollow steel tubular columns and CFST, although the resistance of the bolt shank conditions affects the performance of the connection. In this paper, the use of innovative materials is proposed as a method of enhancing of the load-bearing capacity for both CFST columns and connections. In this line, a first approach of the benefits using high strength steel, fire-resistant steel and geopolymer concrete applied for CFST columns in the fire situation is developed, obtaining better fire results although depending on the columns cross-sections configuration and the part where the advanced material is applied. Related to blind-bolts connections under fire conditions, the use of fire-resistant bolts is assessed. Their higher strength retention in fire could avoid the use of protection, but only in limited cases. Furthermore, a preliminary study on shape memory alloys in the blind-bolts is performed at room temperature and supporting cyclic pull-out loading.The authors would like to express their sincere gratitude to the Spanish Ministry of Economy and Competitivity through the project BIA2012-33144 and to the European Union for the FEDER funds.Espinós Capilla, A.; Romero García, ML.; Hospitaler Pérez, A.; Pascual Pastor, AM.; Albero Gabarda, V. (2015). Advanced materials for concrete-filled tubular columns and connections. Structures. 4:105-113. https://doi.org/10.1016/j.istruc.2015.08.006S105113