CFRP-wrapped hollow steel tubes under axial impact loading

Thin-Walled Structures, 2018

Steel hollow sections used in structures such as bridges, buildings and space structures involve different strengthening techniques according to their structural purpose and shape of the structural member. One such technique is external bonding of CFRP sheets to steel tubes. The performance of CFRP strengthening for steel structures has been proven under static loading while limited studies have been conducted on their behaviour under impact loading. In this study, a comprehensive numerical investigation is carried out to evaluate the response of CFRP strengthened steel tubes under dynamic axial impact loading. Impact force, axial deformation impact velocities are studied. The results of the numerical investigations are validated by experimental results. Based on the developed finite element (FE) model several output parameters are discussed. The results show that CFRP wrapping is an effective strengthening technique to increase the axial dynamic load bearing capacity by increasing the stiffness of the steel tube.

Engineering Structures, 2018

Application of fibre reinforced polymer (FRP) composites has steadily gained popularity in rehabilitation of steelwork over the last decade or so. This popularity is based on the inherent advantages of FRP and the considerable amount of research conducted on the response of FRP strengthened steelwork members under static loads. However, over the course of their service life, steel structures can be subjected to impact loads induced by a variety of sources. This necessitates the requirement for a comprehensive study that can shed light on the behaviour of FRP strengthened steelwork under various loading rates. This paper discusses the experimental results of carbon fibre reinforced polymer (CFRP) strengthened square hollow sections (SHS) under different loading rates. The experiments comprised a series of SHS columns tested under two loading rates: quasi-static (0.05 mm/sec) and impact (4.43 m/sec). Some of these columns were strengthened with different CFRP configurations comprising fibres oriented in the longitudinal direction, transverse direction and in both directions. The effect of coexisting axial compression applied prior and during the application of the transverse load (impact or quasi-static) was also examined. The axial load was introduced in the experimental program to simulate the normal service load that exists on columns in multi-storey frame buildings. Generally, it was found that the effectiveness of CFRP strengthening was increased at a higher loading rate to different degrees depending on the CFRP configuration.

2021

Compared to conventional steel sections, the Steel Hollow Sections have better structural performance due to excellent properties of the tubular shape with regard to loading in compression, torsion and bending in all directions. In many structural engineering applications Hollow Sections are widely used such as airport terminal buildings, railway stations, industrial structures, etc. Carbon Fibre Reinforced Polymer (CFRP) strengthening of structures has been with success applied to concrete structures, and additionally it applied to steel structures recently. In hollow section, Steel-CFRP composite combine the benefits of the high strength to weight ratio and more ductile. This paper presents an experimental investigation carried out with two different matrix layouts of carbon fibres on the axial capacity and crushing behaviour of CFRP strengthened Circular Hollow Section (CHS). With and without CFRP wrapping the experiments were conducted on short steel columns

This paper presents a nonlinear finite element (FE) model for the analysis of very high strength (VHS) steel hollow sections wrapped by high modulus carbon fibre reinforced polymer (CFRP) sheets. The bond strength of CFRP wrapped VHS circular steel hollow section under tension is investigated using the FE model. The three dimensional FE model by Nonlinear static analysis has been carried out by Strand 7 finite element software. The model is validated by the experimental data obtained from Fawzia et al [1]. A detail parametric study has been performed to examine the effect of number of CFRP layers, different diameters of VHS steel tube and different bond lengths of CFRP sheet. The analytical model developed by Fawzia et al. [1] has been used to determine the load carrying capacity of different diameters of CFRP strengthened VHS steel tube by using the capacity from each layer of CFRP sheet. The results from FE model have found in reasonable agreement with the analytical model developed by Fawzia et al [1]. This validation was necessary because the analytical model by Fawzia et al [1] was developed by using only one diameter of VHS steel tube and fixed (five) number of CFRP layers. It can be concluded that the developed analytical model is valid for CFRP strengthened VHS steel tubes with diameter range of 38mm to 100mm and CFRP layer range of 3 to 5 layers. Based on the results it can also be concluded that the effective bond length is consistent for different diameters of steel tubes and different layers of CFRP. Three layers of CFRP is considered most effective wrapping scheme due to the cost effectiveness. Finally the distribution of longitudinal and hoop stress has been determined by the finite element model for different diameters of CFRP strengthened VHS steel tube.

Compared to conventional steel sections, the Steel Hollow Sections have better structural performance due to excellent properties of the tubular shape with regard to loading in compression, torsion and bending in all directions. In many structural engineering applications Hollow Sections are widely used such as airport terminal buildings, railway stations, industrial structures, etc. Carbon Fibre Reinforced Polymer (CFRP) strengthening of structures has been with success applied to concrete structures, and additionally it applied to steel structures recently. In hollow section, Steel-CFRP composite combine the benefits of the high strength to weight ratio and more ductile. This paper presents an experimental investigation carried out with two different matrix layouts of carbon fibres on the axial capacity and crushing behaviour of CFRP strengthened Circular Hollow Section (CHS). With and without CFRP wrapping the experiments were conducted on short steel columns. From the experimental studies It has been inferred that the application of CFRP to short column sections increases ductility of the section and also increases axial load carrying capacity of the section. To improve the performance of existing structures, Carbon fibre could also be with success externally bonded to metal CHS, and such application could also be provided.

Thin-Walled Structures, 2019

In recent years, externally bonded fibre reinforced polymer (FRP) material has gained popularity as an efficient means of strengthening existing civil engineering infrastructure. In the case of steel structures, FRP has frequently been deployed to strengthen against static and fatigue loads. However, the understanding of the effect of impact load on strengthened structures is still in its early stages. In parallel with this, most of the existing studies on impact have concentrated on small scale elements. Thus, the study presented here is aimed at examining the effectiveness of carbon fibre reinforced polymer (CFRP) in strengthening full-scale steel I-section columns against impact load. To achieve this aim, a non-linear finite element model built using ABAQUS was validated against experimental tests and then used to simulate the strengthening technique. The model included failure criteria of all investigated materials (steel, CFRP and adhesive material). Various parameters including boundary conditions, preloading level, kinetic energy, impact location and impact direction were examined. The CFRP strengthening technique was found to be highly effective in preventing column failure whether by global buckling failure or transverse shear failure. In addition the strengthened columns exhibited a reduced axial and transverse displacement by more than 70% in many cases.

Composites Part B: Engineering, 2010

This paper investigates the residual torsional strength of cylindrical T300-carbon/epoxy tubular specimens damaged by low-velocity impacts. A total of 24 specimens were subjected to a 7 J transverse impact under various torsional preloads. First, the torsional strength of four different lamination sequences is studied. Later it is compared with the residual torsional strength (RTS) of tubes impacted under different torsional preloads. FEM models were developed to investigate the effect of the impact-induced delaminations on the torsion-after-impact strength. The Acoustic Emission (AE) technique was used to study the damage propagation during the torsional loading. Results show that, even if the absorbed energy during impacts is the same, the residual torsional strength of the laminates is highly affected by the torsional preload.

Thin-Walled Structures, 2015

In order to prevent vehicle access to a protected area, vehicle barriers can be installed around the perimeter of the area. Bollards are commonly used as vehicle barriers. This is due to the fact that they can be readily blended with other architectural features and present fewer disturbances to a building's functionality when compared to other barrier systems. Hollow steel tubes are used in a variety of barrier system applications where they are required to absorb deformation energy. Varying methods, such as finite element analysis or experimental observation, can be used to determine the collapse behaviour and energy absorption of these steel structures under lateral impact load. These methods have high accuracy but demand a significant amount of time and computational resources. Apart from experimental and numerical analyses, Yield Line Mechanism (YLM) is an approach that can provide the collapse response of sections. This is when a section fails and the YLM of failure forms at its localised plastic hinge point. The YLM analysis approach is commonly used to investigate the performance of thinwall structures that have local failure mechanisms. This paper investigates the collapse behaviour and energy absorption capability of hollow steel tubes under large deformation due to lateral impact load. The YLM technique is applied using the energy method, and is based upon measured spatial plastic collapse mechanisms from experiments. Analytical solutions for the collapse curve and in-plane rotation capacity are developed, and are used to model the large deformation behaviour and energy absorption. The analytical results are shown to compare well with the experimental values. The YLM model is then used to verify the finite element model (FEM), and then the failure behaviour and energy absorption of hollow steel tubes under lateral impact load is investigated in more detail.

and key members are potentially exposed to accidental loads due to extreme situations such as collisions, impacts, and terrorist bombings. Consequently, the current design concept requires that the structures or key members possess adequate capacities to resist accidental loads. To understand the mechanical response of concrete-filled steel tube (CFT) beams subjected to impact loads, this paper presents numerical simulations on the CFT beam tests in an instrumented drop-weight impact facility using finite element code LS-DYNA. The adequacy of finite element modeling (FEM)

Experimental and FEM analysis of AFRP strengthened short and long steel tube under axial compression, 2019

This paper presents the results of an experimental and numerical study of the behavior of circular hollow section (CHS) steel tubes strengthened by Aramid fiber-reinforced polymer (AFRP). The aramid fiber used for this experiment is available under the trade name of Kevlar 49. In this study, thin-walled circular steel tubes externally bonded with fiber in the hoop direction were tested under axial compression to examine the effects of the AFRP thickness, on their axial load carrying and shortening capacity. The three-dimensional finite element models (FEM) of AFRP strengthened circular hollow section (CHS) was developed using ANSYS Workbench Ver. 19.0 and ACP (ANSYS Composite Prep/Post) tool considering both geometric and material nonlinearities. The effects combined of AFRP damage and interlaminar failures for the bonded interface are modeled within FEM using “Hashin” failure criteria and Cohesive Zone Model (CZM), respectively, to provide an accurate simulation. The results involving the failure modes, load vs. axial shortening curve and ultimate load capacity, were obtained from the experimental and numerical simulation and compared for validation. Both the experimental and numerical results are consistent, demonstrating that AFRP external strengthening can considerably enhance the strength of steel tube columns by 96% for short tubes and 23% for long tubes using 3 mm thickness of AFRP.