Bimetallic Steel Research Articles

Resistance Capacity of a Hybrid Titanium–Clad Bimetallic Steel Plate Girder under Patch Loading

Resistance Capacity of a Hybrid Titanium–Clad Bimetallic Steel Plate Girder under Patch Loading

A transfer learning-based approach to fatigue life prediction of corroded bimetallic steel bars using small samples

The low-cycle fatigue life of reinforced steel bars is usually determined by time-consuming tests. To investigate the fatigue behaviour of corroded steel bars, corrosion tests need to be conducted before low-cycle fatigue tests, which further increases time and costs. Although typical machine learning can provide an efficient solution to fatigue life prediction, the inherent need for sufficient training data remains unaddressed. By leveraging the existing test data of other metallic bars, a cost-saving transfer learning-based framework that was able to predict the fatigue life of corroded steel bars made of new types of metallic material using small samples was proposed in this study. A source dataset of eleven types of metallic bars with 450 samples and a target dataset of bimetallic steel bars (BSBs) with 54 samples were collected. Convolutional neural networks (CNN) and backpropagation (BP) neural networks were employed and compared for fatigue life prediction. Two case studies were conducted to validate the proposed framework. Compared with baseline models directly built using the target dataset without transferring the deep features learned by source models, transfer models performed better in predicting the fatigue life of BSBs with much higher accuracy. To be specific, the value of coefficient of determination (R2) for fatigue life prediction of the baseline model was negative, indicating that the target dataset was insufficient to train an isolated model with good accuracy. In contrast, by transferring deep features extracted from the source dataset and stored in source models, an R2 value of 0.883 on the testing set of the target dataset was achieved by transfer models. Additionally, the constructed CNN models offered overall better fatigue life predictions for both the source and target datasets compared with the constructed two-layered BP models. Precisely, for the CNN models, the values of R2 on the target testing sets in Cases I and II were 0.883 and 0.866, respectively, both of which were higher than the corresponding values of 0.812 and 0.798 achieved by the BP models. Furthermore, based on the constructed models, the effects of slenderness ratios, corrosion ratios, and fatigue amplitudes on the fatigue life of BSBs were investigated. The proposed transfer learning-based framework could be used to efficiently predict the fatigue life of BSBs while considering the effects of corrosion.

Patch Loading Design Recommendations for Titanium–Clad Bimetallic Steel Plate Girder

For steel structures service in corrosive environments, corrosion reduces the mechanical properties and effective thickness of the structural steel, which has a significant effect on the durability of steel structures. Titanium–clad bimetallic steel (TCBS), a bimetallic material composed of titanium alloy and carbon steel with excellent corrosion resistance has been suggested to solve the corrosion issue. The TCBS consisting of the TA1 titanium cladding and Q235 carbon steel substrate was introduced in the plate girder as the web to improve durability in this study. The stress–strain properties and failure performance of TCBS and Q235 carbon steel were discussed. Notably, the separation between the cladding and the substrate in the TCBS was observed during the necking stage in the tensile coupon test. Welding method between TCBS web and Q235 carbon steel flange was suggested for processing the plate girder, which was validated to be appropriate according to the experimental results. No crack in welding and TCBS web of plate girder was observed during the patch loading test. A numerical parametric study on the ultimate resistance of TCBS plate girder subjected to patch loading was conducted using the finite element software ABAQUS, in which three different key parameters were included. A comparison between the numerical and predicted results indicated that the design equations suggested in EN 1993–1–5 were too conservative to be directly used for predicting the ultimate resistance of the TCBS plate girder under patch loading, which was caused by the strain–hardening effect and yield plateau of the structural steel. The current design equations were modified to effectively predict the resistance properties of TCBS plate girders.

Cyclic behavior of hot-rolled titanium-clad bimetallic steel under large plastic strain reversals

Titanium-clad (TC) bimetallic steel is a versatile and high-performance material that offers a unique combination of different service properties, making it ideal for various engineering applications where both durability and strength are critical. Existing studies are exploring the application possibility of TC bimetallic steel in seismic zones. The severe seismic action tends to induce large-strain cyclic reversals in structural members. Thus, it is necessary to clarify the cyclic behavior of TC bimetallic steel under large-magnitude cyclic strains, whose strain range exceeds the strain level of conventional low-cycle fatigue tests. This paper has performed 7 large-strain cyclic coupon experiments on hot-rolled TA2 + Q355B TC bimetallic steel. The influences of different loading protocol on cyclic behaviors are clarified. All hysteretic stress-strain relations of TC bimetallic steel exhibit favorable plumpness under large-strain reversals. The increase in maximum strain and accumulation of plastic strain both induce apparent deterioration on elastic modulus. Based upon the experimental stress-strain relations, the Chaboche combined isotropic/kinematic hardening model parameters are calibrated and validated. The flow stresses of most tests exhibit little change over the full-range plasticity, illustrating that the isotropic hardening behavior is negligible. The cyclic behavior of TC bimetallic steel under large-strain reversals can be precisely simulated by a pure kinematic hardening constitutive model rather than a combined isotropic/kinematic hardening model. The Chaboche parameters calibrated from small-strain and mediate-strain cyclic loading tests tend to overestimate the hysteretic energy dissipation ability under large-strain reversals. In addition, the stress-strain relations of TC bimetallic steel are compared with those of low yield point steels, mild steels and high strength steels. The hysteretic energy dissipation ability of TA2 + Q355B TC bimetallic steel is greater than that of low yield point steels, but less than those of mild steels and high strength steels.

Patch-loading resistance performance of stainless-clad bimetallic steel plate girders: Numerical investigations and design methods

Compared with stainless steel, stainless-clad bimetallic steel (SCBS), which comprises a stainless steel cladding layer and a carbon steel base layer, requires a lower project cost and can maintain the same corrosion resistance, thus allowing the corrosion weakening of steel structures to be solved effectively. Investigations regarding SCBS plate girders, which can be widely used in bridge and industrial structure servicing in corrosive environments, are few. In this study, the patch-loading resistance performance of SCBS plate girders is investigated systematically, and the effects of cladding ratios are considered. A finite element modelling method is proposed to predict the patch-loading resistance performance of SCBS plate girders, which is validated using 33 experimental results regarding conventional structural steel and bimetallic steel plate girders. A comparison of the ultimate strength, load–deflection curve, and failure mode shows that the proposed finite element modelling method can be used to effectively clarify the patch-loading resistance performance of SCBS plate girders. A comprehensive parameter study involving 288 numerical models is conducted. Based on numerical results, the basis for design recommendations is presented. The relationship among the ultimate strength of the plate girders corresponding to SCBS, stainless steel (cladding layer), and HSS (base layer) is determined, and a linear equation is proposed. The applicability of Chinese, American, and European codes in determining the ultimate strength of SCBS plate girders is verified. The verification results show that the existing codes cannot be directly used to determine the ultimate strength of SCBS plate girders. Therefore, two strength reduction functions are proposed to modify the design equations in European codes. The undetermined constants in the proposed strength reduction functions for SCBS plate girders with different cladding ratios are statistically calibrated. Additionally, a predictive equation for determining the undetermined constants in function-I is proposed. When these proposed strength reduction functions are employed, the calculation accuracy of the European codes is significantly improved. The basis for design recommendations presented in this study is valid for the SCBS plate girders with specific geometric dimensions and material properties included in the parametric study.

Dynamic compressive behaviours of stainless-clad bimetallic steel under high temperatures

To study the dynamic performance of stainless-clad (SC) bimetallic steel under coupling actions of high temperature and strain rate, a total of 72 compression experiments were designed and conducted at four strain rates (0.001, 1000, 2000 and 3000 s−1) and four temperatures varying from 20 °C to 600 °C. The deformation patterns, stress versus strain responses, as well as strain rate and temperature effects were obtained and analyzed. Experimental results indicated that the dynamic compression performances of SC bimetallic steel were sensitive to both temperature and strain rate. The dynamic yield strength at 3000 s−1 was approximately 1.7 times than that under quasi-static conditions, while reduced by 24–35%, 37–50% and 52–62% when temperatures rose from 20 °C to 200 °C, 400 °C and 600 °C, respectively. Moreover, the strain rate sensitivity increased with the growing strain rate and temperature. The observation of microstructures showed that the grain dimensions declined with increase in strain rate or a decreased temperature. According to test data, a modified Johnson-Cook model was developed for predicting the stress versus strain response of the SC bimetallic steel subjected to combined actions of high strain rate and elevated temperature (20–600 °C), in which the influences of temperature softening, strain-rate strengthening and strain hardening were considered.

Local buckling and axial compressive behavior of stainless-clad bimetallic steel-plate composite walls

This study investigated the local buckling and axial compressive behavior of stainless-clad bimetallic steel-plate composite (SC) walls. Stainless-clad bimetallic steel is a high-performance steel that combines the merits of both the substrate and cladding materials, showing good mechanical properties. An experimental database was compiled to evaluate the effect of normalized faceplate slenderness ratio on the local buckling and axial compressive behavior of SC walls. Experimental investigations were conducted on six stainless-clad bimetallic steel-plate composite walls with parameter of normalized faceplate slenderness ratios. Finite element models were developed and benchmarked for parametric studies. Test results and finite element analysis results were incorporated into the database. The enhanced database were utilized to evaluate the application of the current design provisions in calculating the axial compressive strength. It was found that CECS:546–2018, Eurocode 4, and AISC 360–22 cannot provide reasonable estimation of axial compression strength. Finally, a simplified equation was suggested for estimating the axial compressive strength of SC walls. The design method was conservative for both non-slender and slender steel faceplates.

Post-fire constitutive model on explosively welded stainless-clad bimetallic steel after cold-forming process

This study conducted an experiment on corner stainless-clad bimetallic steel (SBS) specimens to clarify the coupling effects of the cold-forming process and fire exposure on the monotonic mechanical properties of SBS, where different exposure temperatures and cooling methods were considered. The SBS produced through the explosive welding method was used to obtain cold-formed specimens. After the cold-forming process and fire exposure, no obvious cracking was observed in the stainless-steel cladding and metallurgical bonding layer. Based on the tensile coupon test results, the yield plateau in the stress–strain curve of the virgin SBS specimen disappeared because of the cold-forming process. The effects of the exposure temperature and cooling method on the stress–strain curves of the corner SBS specimen were clarified. The variation trends of the key mechanical parameters were discussed. Predictive equations were proposed for the key mechanical parameters of corner SBS specimen after fire exposure. Two constitutive models were suggested for the corner SBS stress–strain curves with and without the yield plateau, which could be used in the numerical and theoretical investigations on the post-fire-resistant performance of cold-formed SBS components. Comparing the experimental and predicted results indicated that the residual monotonic stress–strain curves of the corner SBS could be accurately described using the proposed constitutive models.

Low-cycle fatigue behaviour of hot-rolled titanium-clad bimetallic steel

Titanium-clad (TC) bimetallic steel is able to integrate the superior corrosion resistance of titanium alloy into traditional corrosion-susceptible structural steels, producing prominent life-cycle safety, serviceability and durability. Nevertheless, the relevant seismic performance and fatigue behaviour reported in existing literature are still limited and insufficient to support the codification for structural design of such advanced steel. In order to develop proper plastic/seismic design methodology for TC bimetallic steel structure, the cyclic behaviours and low-cycle fatigue life prediction of such metal must be thoroughly investigated. This paper aims to study the low-cycle fatigue behaviour of hot-rolled bonded TC bimetallic steel manufactured from TA2 titanium alloy and Q355B structural steel. The strain amplitude of low-cycle fatigue (LCF) test ranges from 0.5% to 2.5%, and the strain ratio applied herein includes 0 and -1. The experimental phenomenon, LCF failure mechanism, cyclic stress-strain relationship of different tests are thoroughly compared and discussed. Besides, the influence of strain rate and bond strength are simultaneously demonstrated. The LCF life are fitted and validated through Basquin-Coffin-Manson model, Kuroda model and energy method, respectively. The research outcomes demonstrate that the LCF cracks of TC bimetallic steel tend to be initiated at the cladding layer and propagated into the substrate layer due to a coupled buckling-fatigue failure mechanism. Several representative fatigue behaviour of conventional mild (CM) steels including the three-stage cyclic softening and mean stress relaxation have not been observed in this experimental study. The strain rate exhibits distinct influence on the LCF life and failure mechanism. Both Basquin-Coffin-Manson model and energy method can provide more favourable prediction accuracy for LCF life of TC bimetallic steel than the Kuroda model. Generally the LCF life of TC bimetallic steel is shorter than that of structural steels, stainless steels, titanium alloys and stainless-clad (SC) bimetallic steels. The test records and fatigue-life model parameters obtained can lay a solid foundation for seismic analysis and damage evaluation of TC bimetallic steel structure.

Tensile Behavior of Titanium-Clad Bimetallic Steel Butt-Welded Joints

Because of the promising corrosion resistance and load-bearing capacity, titanium-clad (TC) bimetallic steel has gained increasing attention in ocean/coastal civil and structural engineering. Due to the double-layer nature of TC bimetallic steel, the characteristics of the structural member’s geometry and weld details are considerably different from that of conventional steel members. Even though previous studies have conducted systematical clarifications on parent material of TC bimetallic steels, the mechanical behaviors of weld joints are still vague. This paper firstly describes the manufacture features of TC bimetallic steel welded joints and welded members. Subsequently, the type II and type III butt-welded joints provided by GB/T 13149-2009 are selected to study the corresponding tensile mechanical behavior. Two butt-welded TC bimetallic steel plates were fabricated from hot-rolled bonding TA2 + Q355B TC bimetallic steel and welding wire of ER55-Ni1 and ERTA2ELI. Eight tensile coupons were then extracted from the two welded plates and loaded to failure monotonically. The failure mechanism, stress–strain curves and key mechanical properties are studied and compared with that of parent material. It is found that both types of welded joints possess two fracture points. The first one refers to the fracture of weld joint between the clad layer and titanium cover plate, whilst the second one is the eventual fracture of substrate metal. When the first fracture point is reached, the stress–strain relation exhibits a sharp drop in stress value. Thereafter, a strain-hardening behavior can still be observed prior to the ultimate strength point. The first fracture-induced stress drop of type II joint is less than that of type III joint, whilst the strain-hardening amount of type II joint is more outstanding than that of type III joint. The fracture elongations of type II joint and type III joint are respectively 37% and 57% that of the parent material, whilst the proportions between the ultimate strengths of welded joints and parent material are, respectively, 90% and 93%. In general, the two types of TC bimetallic steel weld joints investigated herein exhibit favorable load-bearing capacity but unfavorable ductility and deformability. Based upon the experimental results, the structural design methodology of welded TC bimetallic steel structure is discussed. The investigations conducted in this paper can provide reference for development of structural design theory of welded TC bimetallic steel structure.

High-Cycle Fatigue Properties of Titanium-Clad Bimetallic Steel with Different Interfacial Conditions

Titanium-clad (TC) bimetallic steel is an advanced composite steel consisting of metallurgically bonded titanium alloy and structural steel. This paper compared the high-cycle fatigue properties of three types of TC bimetallic steels, including two hot-rolled bonding types with different bonding strengths and an explosion-bonded type. The three types of TC bimetallic steels were all manufactured from TA2 titanium alloy as the cladding metal and Q355B structural steel as the substrate metal, of which the thicknesses are 2 mm and 8 mm, respectively. Based on the comparison results, the qualitative relationship between the bonding interface strength and the manufacturing methods with the basic mechanical and high-cycle fatigue properties was obtained. It was found that the different manufacturing methods and the bonding degree of the two component metals resulted in the different nonlinear yield plateau in the TC bimetallic steel. The high bonding strength seems to affect the failure mode of the tensile coupons. The bonding interface shear strength only slightly affects the tensile performance, which exhibits visible effects only when the test strain reaches the fractured state. In addition, three failure modes in total were found in the high-cycle fatigue tests for the three types of TC bimetallic steel. The manufacturing methods and the bonding interface strength significantly affect the fatigue phenomena of the TC bimetallic steel. The hot-rolled bonding TC bimetallic steel with high bonding strength has a 10% improvement in fatigue performance than the one with low bonding strength. Despite this, the manufacturing methods significantly affect the fatigue ratio, while the influence of the bonding strength on the high cycle fatigue performance is limited. The research outcomes can provide reference for the selection of different manufacturing methods and interfacial conditions for the use of TC bimetallic steel in structural engineering.

Experimental and numerical investigation on patch loading capacity of longitudinally stiffened hybrid titanium-clad bimetallic steel plate girder

Plate girders are important load-bearing components of bridge and industrial structures. Corrosion significantly affects durability and service life of plate girders. Bimetallic steel consisting of corrosion-resistance metal and metal with superior mechanical properties provides an engineering solution for the mitigation of corrosion. The titanium-clad bimetallic steel (TCBS) was innovatively introduced into the plate girder as the web to solve the corrosion issue, where the nonlinear resistance performance and failure mode of a longitudinally stiffened hybrid TCBS plate girder under patch loading were investigated experimentally. The test results prove that the longitudinally stiffened hybrid TCBS plate girder has stable load-bearing performance, which is similar to that of the conventional mild steel plate girder. Effects of the shape and magnitude of the initial geometric imperfection on the resistance behavior of the longitudinally stiffened hybrid TCBS plate girder were investigate numerically. A parametric study on the effects of the material properties, longitudinal stiffener location, relative flexural rigidity of the longitudinal stiffener, web panel aspect ratio, and web height-to-thickness ratio on the resistance and critical buckling behaviors of a longitudinally stiffened hybrid TCBS plate girder was performed. Considering the strain strengthening properties of TCBS, the ultimate resistance and ductility of longitudinally stiffened hybrid TCBS plate girders can be significantly improved without affecting the buckling performance. The effect of key parameters on the longitudinally stiffened hybrid TCBS plate girder is consistent with that of the conventionally stiffened mild steel plate girder. Therefore, it is a feasible solution to apply TCBS to the plate girder web, which performs a beneficial effect on the durability of the plate girder.

High-cycle fatigue properties of explosion bonded titanium-clad bimetallic steel

Titanium-clad (TC) bimetallic steel is a new type of high-performance laminated structural steel, of which the high-cycle fatigue properties were experimentally studied in this paper. The test coupons were manufactured from explosion bonded TA2 + Q355B TC bimetallic steel plate, and their fracture features after fatigue failure were analysed through a sets of scanning electron microscope (SEM) micrographs. Besides, their basic mechanical properties were obtained by the tensile coupon tests and bonding interface shear tests. Based on the test results, the fatigue stress-life curve (S–N curve) of the explosion bonded TC bimetallic steel was obtained, and it was subsequently compared with that of the uniform material law estimates as well as the codified S–N curves provided by four national standards for steel structure design. It demonstrates that the fatigue performance of TC bimetallic steel studied in this paper is much higher than that of standard single-metal structural steel (by over 20 % compared with the low-alloyed steels with similar tensile strength), and the fatigue design curves for conventional structural steel are conservative in predicting the fatigue life of the TC bimetallic steel herein. In addition, fatigue cracks tend to initiate from the bonding interface and exhibit considerably different propagation phenomena in the cladding titanium alloy and substrate structural steel regions.

Low-Cycle Fatigue Behaviour of Hot-Rolled Titanium-Clad Bimetallic Steel

Low-Cycle Fatigue Behaviour of Hot-Rolled Titanium-Clad Bimetallic Steel

A Transfer Learning-Based Approach to Fatigue Life Prediction of Corroded Bimetallic Steel Bars Using Small Samples

A Transfer Learning-Based Approach to Fatigue Life Prediction of Corroded Bimetallic Steel Bars Using Small Samples

Design recommendations on longitudinally stiffened titanium-clad bimetallic steel plate girder

In this study, titanium-clad bimetallic steel (TCBS) was innovatively introduced into the plate girder as a web, which enhanced the durability. The ultimate strength of a longitudinally stiffened TCBS plate girder under patch loading was investigated. There were clear differences in the nonlinear properties of the stress–strain curves of Q235 carbon steel, TA1 titanium, and TCBS. The numerical modeling method was verified via an experiment on a TCBS plate girder. A parametric study was performed on the ultimate strength of a longitudinally stiffened TCBS plate girder. The key parameters selected in this study included the position of the longitudinal stiffener, web aspect ratio, web slenderness, and relative load length. The variations in the ultimate strength and the buckling reduction coefficient were examined. The results indicated that the effects of the key parameters on the ultimate strength were clearly different from those on the buckling reduction coefficient. Additionally, the design equations in EN 1993–1–5 were too conservative to be suitable to predict the ultimate strength of the TCBS plate girders subjected to patch loading. Based on the numerical results, a predictive equation for the buckling reduction coefficient of a longitudinally stiffened TCBS plate girder under patch loading was devised. Compared with design equations in EN 1993–1–5, the proposed equation showed better accuracy.

Nonlinear patch resistance performance of hybrid titanium-clad bimetallic steel plate girder with web opening

Titanium-clad bimetallic steel (TCBS) is a new type of structural steel, which consists of TA1 cladding with outstanding corrosion resistance and Q235 mild steel base with good mechanical properties. Corrosion weakens the thickness of plates in steel members, which reduces the resistance capacity. The web thickness of the plate girder is relatively thin. Hence, the web is more prone to be weakened due to corrosion. To resolve the above issue, an innovative configuration of introducing TCBS into the plate girder as the web was proposed. The monotonic tensile coupon test results stated that TCBS has no evident yield plateau in its stress-strain curve. An experiment was conducted to investigate the nonlinear resistance performance of the hybrid TCBS girder under patch loading. After the experiment, the wave bending deformation of the web exhibited an axisymmetric distribution, where a tensile field was formed. The plastic hinge was formed in the loading area on the flange. No delamination or cracking in the TCBS was observed. A numerical modeling method for the hybrid TCBS plate girder under patch loading was established. Subsequently, a parametric study of the hybrid TCBS plate girder under patch loading was conducted using the proposed numerical modeling method. The effects of the material model, web opening location, web aspect ratio, height–thickness ratio, and loading location on the resistance behavior of the hybrid TCBS plate girder were thoroughly investigated.

Post–fire properties of stainless–clad bimetallic steel produced by explosive welding process

To evaluate residual resistance performance of stainless–clad bimetallic steel (SBS) structures after a fire, it is necessary to determine post–fire performance of SBS. After heating treatment, no cracks were observed in stainless steel cladding of the SBS produced by the explosive welding process. After fire exposure, separation along metallurgical bonding interface was observed in the SBS produced through the hot rolling process. The results of tensile coupon test were used to clarify effects of exposure temperature and cooling method on stress–strain curves of the SBS. The variation trends followed by key mechanical parameters of SBS with different cooling methods and exposure temperatures were investigated. After tensile coupon test, the SBS produced through different processes exhibited different failure modes. In general, although the cladding and substrate metals were the same, different processes yielded evident differences in the stress–strain properties and failure performance of SBSs after exposure to elevated temperatures.

Experimental cyclic behaviour and constitutive modelling of hot-rolled titanium-clad bimetallic steel

Titanium-clad (TC) bimetallic steel exhibits distinct application potential in coastal building and ocean civil and infrastructure engineering due to its promising corrosion resistance and load-bearing capacity. However, understanding on seismic performance and relevant design methodology of TC bimetallic steel structure is still limited and insufficient to support further engineering application in seismic zones. This paper is intended to clarify the experimental cyclic behaviour and suitable constitutive models of hot-rolled TC bimetallic steel. To this end, a total of 19 cyclic coupon tests are conducted on TC bimetallic steel coupons with the raw surface and polished surface. The important mechanical properties, including the hysteretic stress–strain relationship, cyclic backbones, evolutionary law with regard to the cumulative plastic strain, are thoroughly recorded and compared. The cyclic backbones are fitted through the Ramberg-Osgood model. The influences of cyclic loading protocol type on cyclic behaviour are discussed. Based upon the experimental results, material-dependent parameters of Chaboche isotropic/kinematic hardening model and Giuffre-Menegotto-Pinto constitutive model are calibrated. The fitting performances of such two constitutive models are validated through comparison between experimental results and simulation results. All simulation stress–strain relations show a favourable agreement with the experimental counterparts. The relative errors between most simulation peak stress values and experimental peak stress values are lower than 5.0%. Moreover, the cyclic behaviour of TC bimetallic steel is compared with that of mild structural steels and stainless-clad (SC) bimetallic steel. The experimental results revealed herein and constitutive models calibrated in this paper can lay a solid foundation on subsequent numerical simulation.

Local buckling behaviour of stainless-clad bimetallic steel built-up square hollow section stub columns

The local buckling behaviour and design of built-up square hollow section (SHS) stub columns made of the stainless-clad (SC) bimetallic steel is addressed in this paper by experimental and numerical investigations. A total of seven stub column specimens fabricated from hot-rolling bonded SC bimetallic steel plates with nominal thicknesses of 8 mm and 13 mm were tested and analysed.​ Precise measurements of dimensions and geometrical imperfections of the specimens were conducted with the assistance of a non-contact 3D laser scanner. The scanned data was processed by a novel approach to provide a more accurate analysis of imperfections. Finite-element (FE) models with geometric imperfections obtained from 3D-scanned data were developed and validated against the dependent test results herein and independent ones. Comprehensive parametric studies considering various clad ratios, normalized plate slendernesses and steel grades were carried out by using the verified FE models. The applicability of current codified design methods to the SC bimetallic steel SHS stub columns was evaluated through comparisons with the numerical results. A normalized slenderness limit as well as an effective width formula were proposed based on the parametric studies and the evaluation of existing design methods. With improved efficiency and consistency, the design methods proposed herein can be utilized in the future application of the SC bimetallic steel structures.