Ali Shrih, Adeeb Rahman and Mustafa Mahamid
Nuts and bolts have been used as fasteners of steel structures for many years. However, these structures remain susceptible to fire damage. While conducting fire experiments on…
Abstract
Purpose
Nuts and bolts have been used as fasteners of steel structures for many years. However, these structures remain susceptible to fire damage. While conducting fire experiments on steel structures is sometimes necessary, to better understand their behavior, such experiments remain costly and require specialized equipment and testing facilities. This paper aims to present a highly accurate three-dimensional (3D) finite element (FE) model of ASTM A325 bolt subjected to tension loading under simulated fire conditions. The FE model is compared to the results of experimental testing for verification purposes and is proven to predict the response of similar bolts up to certain temperatures without the need for repeated testing.
Design/methodology/approach
A parametric 3D FE model simulating tested specimens was constructed in the ANSYS Workbench environment. The model included the intricate details of the bolt and nut threads, as well as all the other components of the specimens. A pretension load, a tension force and a heat profile were applied to the model, and a nonlinear analysis was performed to simulate the experiments.
Findings
The results of the FE model were in good agreement with the experimental results, deviations of results between experimental and FE results were within acceptable range. This should allow studying the behavior of structural bolts without the need for expensive testing.
Originality/value
Detailed 3D FE models have been created by the authors have been created to study the behavior of structural bolts and compared with experiments conducted by the authors.
Details
Keywords
Ali Shrih, Adeeb Rahman and Mustafa Mahamid
Heavy hex structural bolts have been used in a wide range of steel structures for many years. However, these structures remain susceptible to fire damage. Conducting fire…
Abstract
Purpose
Heavy hex structural bolts have been used in a wide range of steel structures for many years. However, these structures remain susceptible to fire damage. Conducting fire experiments on full-scale steel structures is costly and requires specialized equipment. The main purpose of this research is to test, analyze and predict the behavior of ASTM A325 bolts under tension loading in simulated fire conditions and develop a reliable finite element model that can predict the response of similar bolts without the need for repeated testing.
Design/methodology/approach
The experimental work was conducted at the University of Wisconsin-Milwaukee, where an electric furnace was custom-built to test a bolted specimen in tension under elevated temperatures. A transient-state testing method was adopted to perform a group of tests on 12.7 mm (½”) – diameter A325 bolts. The tests were divided into two groups: the first one was used to calibrate the equipment and choose a final testing arrangement and the second group, consisting of four identical tests, was used to validate a finite element model.
Findings
The temperature-displacement and load-displacement response was recorded. The tested bolts exhibited a ductile fracture in which a cup-and-cone shaped failure surface was formed in the threaded section at the root of the nut. ASTM A325 bolts are widely used by engineers in building and bridge construction, the results of this research enable engineers to determine the behavior and strength of ASTM A325 bolts when such bolts when exposed to fire event.
Research limitations/implications
Structural bolts are used to connect structural members, and they are part of structural assembly. To study the behavior of the bolts, the bolts only were investigated in a fire simulated in a furnace. The bolts studied were not part of a structural assembly.
Practical implications
The results of this study enable engineers to evaluate the condition of ASTM A325 bolts when subjected to fire loading.
Originality value
Tests were conducted at the University of Wisconsin – Milwaukee’s structures laboratory to study the effect of fire on an ASTM A325 bolts. Many tests under fire loading have been performed by researchers on different components of steel structures, this study focuses on studying the behavior of ASTM A325 bolts which are widely used in the USA.
Details
Keywords
Karim Al Khatib, Elie Hantouche and Mohammed Ali Morovat
This study aims to investigate the thermal creep behavior of steel frame assemblies with shear tab connections subjected to transient-state fire temperatures. Different key…
Abstract
Purpose
This study aims to investigate the thermal creep behavior of steel frame assemblies with shear tab connections subjected to transient-state fire temperatures. Different key parameters are investigated to study their effect on the global response of the steel frames in fire.
Design/methodology/approach
Finite element (FE) models of connection assemblies are first analyzed using Abaqus under transient-state temperature conditions and validated against experimental work available in the literature. Upon acquiring the validated conditions, parametric studies are carried out to study the effect of key geometric and heating parameters on the overall response of the frame assembly to fire temperatures. Thermal creep material is also incorporated in the analyses through a user-defined subroutine, and a comparison between including and excluding creep material is illustrated to show the effect of thermal creep on the structural behavior.
Findings
The results reported herein indicate that having a rigid column increases the thermal-induced axial forces, thus increasing the development of thermal creep strains. Slow heating rates can cause axial stress relaxation in the restrained beam and increase the mid-span deflection and consequently the development of beam catenary action. The results also show that reaching higher initial cooling temperatures and having longer cooling phase durations result in more tensile forces at the end of the cooling phase.
Originality/value
Previous studies were limited to isolated steel connections under steady-state conditions. This study investigates the creep behavior of shear tab connection assemblies under transient-state conditions of fire when creep effects are explicitly considered. This can provide a rational and realistic assessment of the steel behavior in fire events.