Moment Strength Research Articles

Hysteretic energy distribution model of CFDST composite frame with metallic dampers using coupled shear-flexural beam model

Novel steel–concrete composite structures have drawn increasingly attention in recent years especially in high-rise buildings owing to its superior structural performance over conventional concrete and steel structures. Moreover, energy dissipation devices such as metallic dampers and buckling-restrained braces (BRB) were necessarily added in this type of structure to resist seismic loads. However, the existing research regarding to the dual system consisting of composite frame and energy dissipation was limited. In this paper, the dual system consisting of concrete-filled double skin steel tubular (CFDST) composite frame and metallic damper was set as the research subject, especially focusing on the analysis of hysteretic energy distribution along the height. The 10- and 20-story dual systems were designed with different parameters revealing the influence of semi-rigid connection and metallic damper. Nonlinear models of structures established by Opensees software were validated by the test results. Afterwards, the energy distributions of all stories were discussed. It demonstrated that the metallic damper could absorb considerable energy under seismic loads while a semi-rigid connection with relatively high moment strength had a detrimental effect on the column. Moreover, the semi-rigid connection in the span without metallic damper in high story exhibited significantly larger rotation than that in the span with metallic damper. Finally, the method to estimate the energy distribution estimation of the dual system was developed, in which the lateral displacement pattern was observed by the coupled shear-flexural beam model to fully consider the flexural deformation of the dual system. An equivalent distribution of the shear and bending stiffness was also proposed considering the effect of the semi-rigid in the span without metallic damper. The predicted results from the model were validated by the analysis results derived from the nonlinear model. The theoretical and analytical results of the paper could activate the application of the dual system and provide a reasonable method to estimate the hysteretic energy distribution of the dual system.

Development of lightweight CFS composite built-up beams: Tests and flexural response

Although previous attempts for enhancing the buckling resistance of cold-formed steel (CFS) built-up beams through intermittent stiffening, external stiffening and adoption of concrete as composite sections were successful, they may compromise the lightweight constructional feature of these elements. This paper presents a test program aimed at developing CFS composite built-up beams with superior buckling performance and low self-weight for ensuring lightweight construction. Unlike concrete, lightweight stiff boards of timber and glass fibre reinforced polymer (GFRP) were sandwiched between the CFS channels in the web and flange region to construct the lightweight composite beams. All of the beam specimens were subjected to four-point bending with simply supported boundary conditions. Peak strength, load-deformation curves, initial stiffness, strength-to-weight ratios, failure modes and the normalized yield and plastic moment strengths were compared. This study established the structural feasibility of developing lightweight CFS composite built-up beams from timber and GFRP boards, indicating that the flexural strength and stiffness are significantly improved by 150% and 80%, respectively, as compared to the unstiffened CFS built-up beams. Moreover, the studied composite beams were shown to attain their full yield moment capacities, and in some cases more than 90% of their plastic moment capacity, resulting in built-up members with a higher structural efficiency.

The behavior of cold‐formed steel geopolimeric composites

AbstractGeopolymer concrete‐filled cold formed steel composite beams can exhibit high durability and adequate strength. The geopolymer concrete is used to manufacture the cold‐formed steel tubular composite beam due to the significant advantages, such as greater in strength resisting capacity, higher‐energy dissipation capacity, and more stiffness than the regular one. This paper reports an experimental investigation on the behavior of rectangular geopolymer concrete‐filled cold‐formed steel composite beams. In order to investigate the mechanical behavior (such as flexural, shear, and torsion) of geopolymer concrete‐filled cold‐formed steel tubular composite beams (GCFTBs), 48 beam samples were tested. The 16‐GCFTBs and another 16‐GCFTBs were tested under flexural and overhanging, respectively, which the 16‐GCFTBs were tested under pure torsion. The relationships for load–displacement, torsional moment‐rotation angle, energy dissipation capacity, ductility, and failure mode were analyzed. The test results showed that the increase in cross‐sectional area and curing temperature had a significant effect on bending, shear and torsion behavior. Although the increase in the cross‐section ratio (height/width) increased the bending moment capacity, it decreased the displacement capacity and caused a decrease in ductility. Curing conditions and cross‐section ratio affected strength, displacement capacity, and experimental modulus of elasticity in both bending and shear tests. Increasing the cross‐section ratio and curing temperature resulted in an increase in ductility. Contrary to bending test and shear test, curing temperature, and cross‐section ratio increased both torsional moment strength and rotation angle in torsional moment tests.

Structural Performance of Prefabricated Composite Girders for Railway Bridges along with Girder-to-Deck Interface Connections for Mechanical Injection

Recently, to resolve a growing need for durable and resilient railway bridge construction/reconstruction systems, a great amount of research has been carried out in many countries. As a part of such studies, prefabricated composite girders with an innovative girder-to-deck connection have been proposed that facilitate construction by eliminating interference during on-site processes. In this study, a railway bridge prototype of prefabricated composite girders with girder-to-deck connections was designed to facilitate future application enhancement of off-site construction. Then, prefabricated composite girders were developed by deploying different girder-to-deck connections through geometric detailing of reinforcement, headed stud connectors, and precast decks. Based on the calculation theory of interface shear transfer, the detailed design of different girder-to-deck connections was carried out, in particular the reinforcement spacing. Furthermore, finite element analysis of prefabricated composite girders was conducted to determine the flexural moment strength of prefabricated composite girders. Parametric studies were carried out to consider the factors affecting the detailed design of the connection, ensuring that the connection is correctly designed, thereby ensuring the structural performance of prefabricated composite girders. From the results, conclusions were drawn. The developed cases satisfied the interface shear criteria according to both conventional and plastic approaches. There was no significant difference in flexural moment strength between the developed cases since all cases were designed with the full shear connection. In all cases, the flexural performance was ensured and can be used for railway bridges. The most optimum case of prefabricated composite girders is selected in specific design situations.

Simple Truss Model to estimate the shear strength of short links in the Eccentrically Braced Frame (EBF) steel system

The measured-to-estimated shear force ratio (Overstrength ratio) is an important metric for the capacity design of a shear link’s adjacent elements and connections. However, some investigations found that short links had an abnormally high overstrength ratio if the shear strength of short links is estimated by the provisions of the American Institute of Steel Construction (AISC 341-16). This study assesses the AISC 341-16 equation’s precision in estimating the shear strength of short links and suggests a Simple Truss Model (STM) for this purpose. The proposed STM considers the strain hardening of flanges and the web due to cyclic loading, where the STM was derived from the end links to reach the plastic moment strength (Mp). An experimental database of 109 specimens from the literature was gathered, screened, and preprocessed to assess the performance of these models. This research found that the overstrength ratio for built-up and rolled W-shape short links is underestimated by the AISC 341-16 provisions; only 4% and 13% of built-up and rolled W-shape specimens, respectively, meet the suggested AISC overstrength value of 1.25. The proposed STM model beat the AISC equation in predicting the overstrength values, with mean values of 1.21 and 1.15 for the built-up and rolled W-shape specimens, respectively. Additionally, for the built-up and W-shape specimens, respectively, 58% and 73% of the overstrength determined by STM conform with the recommended AISC overstrength value of 1.25. Since the STM considers the link length and cross-sectional area, contrary to what the AISC predicted, the calculated overstrength values are less susceptible to the link length ratio, flange width-to-thickness ratio, and the ratio of the flange-to-web areas. This study recommends switching from the current AISC equation to the STM because the STM predictions have statistical metrics that are noticeably better than the AISC equation, with Root Mean Square Error (RMSE) and Mean Absolute Percentage Error (MAPE) of 0.27 and 18.6%, 0.22 and 14.6%, and built-up and rolled W-shape links, respectively.

Quadratic Zeeman spectral diffusion of thulium ion population in an yttrium gallium garnet crystal

The creation of well understood structures using spectral hole burning is an important task in the use of technologies based on rare earth ion doped crystals. We apply a series of different techniques to model and improve the frequency dependent population change in the atomic level structure of Thulium Yttrium Gallium Garnet (Tm:YGG). In particular we demonstrate that at zero applied magnetic field, numerical solutions to frequency dependent three-level rate equations show good agreement with spectral hole burning results. This allows predicting spectral structures given a specific hole burning sequence, the underpinning spectroscopic material properties, and the relevant laser parameters. This enables us to largely eliminate power dependent hole broadening through the use of adiabatic hole-burning pulses. Though this system of rate equations shows good agreement at zero field, the addition of a magnetic field results in unexpected spectral diffusion proportional to the induced Tm ion magnetic dipole moment and average magnetic field strength, which, through the quadratic Zeeman effect, dominates the optical spectrum over long time scales. Our results allow optimization of the preparation process for spectral structures in a large variety of rare earth ion doped materials for quantum memories and other applications.

Experimental study on cyclic flexural behaviour of GFRP-reinforced seawater sea-sand concrete slabs with synthetic fibres

Seawater and sea-sand (SWSS) concrete is a new type of concrete with many economic and environmental benefits. However, chloride-induced corrosion of steel reinforcement is a major problem associated with this type of concrete. Due to its excellent resistance in chloride environments glass fibre reinforced polymer (GFRP) reinforcement could be utilized in SWSS concrete as an alternative to steel Adding fibres can also improve the concrete properties reinforced with GFRP bars. Fibres can affect the post-crack response and failure mode of GFRP reinforced concrete and also improve the bond between rebar and concrete. This study focused on the flexural behaviour of GFRP reinforced SWSS concrete slabs with or without fibre incorporation which has not yet been fully addressed in the literature. Polypropylene (PP) and polyvinyl alcohol (PVA) fibres were used for the concrete reinforcement. Under-reinforced (ρ < ρb) and over-reinforced (ρ > ρb) GFRP reinforced concrete (RC) slabs were prepared and subjected to four-point cyclic bending loads. The results show that GFRP bar is a promising alternative to steel for SWSS concrete reinforcement. The GFRP RC slabs with plain SWSS concrete had a cracking moment which was 13% lower than the values predicted by the ACI 440.1R-15 provisions. However, adding fibres, particularly PP fibres, could successfully compensate for this reduction. Variation in GFRP reinforcement ratio had almost no effect on cracking moment. With the addition of fibres, the cracking moment and ultimate strength of the slabs were both improved. Crack width and crack spacing were reduced in fibre-reinforced SWSS concrete slabs compared with the plain concrete counterparts. Fibres reduced the residual deflection of the slabs at the end of each cycle. Comparing experimental deflection results with the values predicted by different models revealed that there is no available model could satisfactorily predict deflection for all the GFRP reinforced SWSS slabs.

Seismic response of slender MDOF structures with self‐centering base shear and moment mechanisms

AbstractAs the amplification of seismic force demands due to higher‐mode effects on tall buildings is increasingly recognized as a design challenge, a number of high‐performance systems have been proposed to limit such effects through combined base shear‐limiting and moment‐limiting dual mechanisms. To better understand the influence of these dual base systems on the overall seismic behavior of tall buildings, this paper presents a study on the seismic response of Multi‐Degree‐of‐Freedom (MDOF) systems incorporating combined base shear‐limiting and moment‐limiting mechanisms. For an MDOF system with a given initial period and base strength level, the base shear‐limiting mechanism is defined by a shear strength factor, an inelastic stiffness parameter, and an energy‐dissipation parameter, while the base moment‐limiting mechanism is defined by a moment strength factor. To determine the influence of these parameters on the overall seismic responses of MDOF structures, a comprehensive parametric study was conducted, and the results were presented and discussed in terms of base displacement and rotation demands, seismic force demand amplification at the base and along the height, peak floor acceleration, peak roof drift, and absorbed energy. The numerical modeling methodology used in the parametric study was validated against 200 small‐scale shaking table tests of a scaled MDOF specimen with a base shear and moment dual‐mechanism system and was used to model MDOF structures that are representative of tall buildings with initial periods ranging from 1.0 to 10 s and having various base‐mechanism properties. The parametric study was then conducted using an ensemble of 20 Ground Motions (GM) scaled to three code‐specified seismic hazard levels for Los Angeles, California. The results of this study can be used to facilitate the design of base shear and moment dual‐mechanism systems for mitigating higher‐mode effects and enhancing the seismic resilience of tall buildings.

Stair-climbing wheelchair proven to maintain user's body stability based on AnyBody musculoskeletal model and finite element analysis.

The electric stair-climbing wheelchair is a beneficial mobile assistance device for older adults and disabled persons with poor walking ability, as it reduces the daily walking and climbing burden. In this paper, 11 older adults were tested when using a stair-climbing wheelchair in three environments: flat ground, slopes, and stairs. The kinematic and dynamic parameters of the lower limb joints were simulated by AnyBody 7.2 human model simulation software using Vicon 3D infrared motion capture, a 3D force table, and analyzed by ANSYS 19.2 Workbench. The joint force, joint moment, and muscle strength did not change significantly under the three environments when using the wheelchair. Through finite element analysis of the mechanical properties of the human body, when using the wheelchair, no significant differences in the overall stress distributions of the fifth lumbar spine, hip bone, or femur were found among the three environments, no significant differences in deformation and displacement were found, and the stress distribution was relatively stable. Therefore, the human body is stable enough to use the electric stair-climbing wheelchair in the three test environments, all of which will be commonly encountered in daily life.

Supporting optimization of thick seam roadway with top coal based on orthogonal matrix analysis

Aiming at the problem of large deformation and difficulty in surrounding rock control of the top coal roadway in thick seam, theoretical analysis, theoretical analysis, numerical simulation, orthogonal matrix analysis and other methods were used to study the roof deformation and support parameter optimization of the top coal roadway in thick seam. Firstly, the structural model and roof mechanical model of the top coal roadway in thick seam were established, and the deformation coefficient TK was defined based on the relationship between curvature radius and bending moment, maximum bending moment and ultimate tensile strength of beam. According to the ratio of deformation rate between TK and beam to determine the roof deformation mode of top coal roadway, the discriminant conditions of roadway roof stability under two deformation conditions are obtained. Due to the characteristics of serious coal-rock fragmentation, large roof deformation, and integration of top coal and side coal. Therefore, the combined support method of “high prestressed long and short anchor cables” is proposed by double arch bearing structure control technology. Finally, based on the orthogonal matrix analysis method of supporting parameters optimization of the top coal roadway in thick seam, the analysis amount of supporting scheme is significantly reduced, the comprehensive evaluation of multi-factor and multi-supporting effect of roadway support is realized, and the optimal supporting scheme is obtained. Compared with the surrounding rock of the roadway without support, the deformation of the roof is reduced by 27.27%, the deformation of the two sides is reduced by 45.24%, and the tensile failure volume is reduced by 54.66%. The top coal roadway in thick seam has been effectively controlled, which provides guarantee for high yield and high efficiency of the mine.

A Design Process for Preventing Brittle Failure in Strengthening RC Slabs with Hybrid FRP-HPC Retrofit Systems.

The retrofitting of existing RC slabs with an innovative system comprising FRP and HPC has been demonstrated to be effective in strengthening and overcoming the logistical challenges of installation. Nonetheless, the excessive improvement of flexural strength over shear strength would cause the sudden failure of rehabilitated flexural members. The literature has previously recommended failure limits to determine the additional moment strength compared with the shear strength to prevent brittle shear failure of strengthened, continuous RC slabs. This study suggests a design process for preventing shear failure and inducing the ductile-failure mode to improve the safety and applicability of retrofitted RC slabs based on the proposed failure limits. The effectiveness of the procedure in brittle-failure prevention for the end and interior spans of retrofitted RC slabs is illustrated via a case study. The outcomes showed that the retrofit system with 0.53-mm-thick-CFRP prevented brittle failure and significantly enhanced the design-factored load and ultimate failure load by up to 2.07 times and 2.13 times, respectively.

Seismic performance of a ductile rod exterior connection system for precast concrete industrial buildings

The seismic performance of a ductile rod system for exterior precast concrete beam-to-column connections was experimentally evaluated. Five full-scale precast concrete beam-to-column subassemblies connected with ductile rods were fabricated, considering various aspects (ductile rod size, prestressing, and flexural/shear capacities). Lateral cyclic loading tests were conducted for the precast concrete connections along with two monolithic reinforced concrete connections. Despite their relatively lower lateral stiffness, most precast concrete connections showed sufficient moment capacities with peak moments at approximately 3% to 4% interstory drifts. The prestressing tendons were effective at enhancing moment and shear strengths of the precast concrete connections, as well as in reducing slip of the ductile rods. The precast concrete specimens generally showed satisfactory seismic performance, fulfilling acceptance criteria specified by the American Concrete Institute. The test results demonstrated that careful considerations are required in the design of ductile rods and high-strength threaded bars to induce stable flexural responses of the precast concrete connections.

Seismic performance of RWS moment connections to steel box-columns and H-beams with general sections

In this study, full-scale seismic testing and 3D finite element analysis were carried out on reduced web section (RWS) connections. A steel H-beam-to-box-column connection was designed to have two parallel long openings in the beam web. The opening was rectangular with semicircles at both ends. The design used the adjacent beam flanges to take shear forces with the beam web with openings, which made it possible to apply RWS connections with general sections. The design parameters were then selected to delay the occurrence of local plate buckling in the beam flanges near the beam web with openings, which ensured that the connections developed sufficient plastic deformation before reaching the maximum strength. The results showed that the refined design could move the plastic hinges of the connections away from the column faces. Moreover, after a complete loading cycle with a drift angle of 4% rad, the connections still had a moment strength of >80% of the beam plastic moment strength. The connection performance met the AISC seismic requirement. This design refinement makes it possible to further apply RWS connections to steel moment frames in building retrofits.

Titanium dioxide surface energy levels tuning by self-assembled monolayers

Tailoring the work function of functional layers in an optoelectronic device is an important means for performance improvement, as it results in changes in charge extraction or recombination. One way to proceed is to adsorb molecules with varying dipole moment strengths and signs. In this communication, the surface of anatase TiO2 is modified using different self-assembled monolayers (4-chlorobenzoic acid, 4-nitrobenzoic acid, 4-methoxybenzoic acid, and β-alanine) and the energetics at the interface is determined using a series of photoelectron spectroscopy techniques, namely, ultraviolet photoelectron spectroscopy, x-ray photoelectron spectroscopy, and inverse photoemission spectroscopy. The observed changes in work function are correlated with the dipole moments of the respective acids, calculated by density functional theory. Finally, the relevance of this interfacial engineering for controlling the charge extraction from an optoelectronic device is illustrated.

Seismic research on column base joint of L-shaped CFST columns under cyclic loading

The newly exposed column base (ECB) for L-shaped concrete-filled steel tube (CFST) columns investigated in this study consists of an outer base plate, a concrete cushion, and anchor bolts. Three ECB specimens of the L-shaped CFST column were tested under constant axial loading and cyclic horizontal loading to investigate their seismic behavior. The failure mode, moment versus rotation relationship, hysteretic behavior, and ultimate moment strength were analyzed. The test results indicated that the failure mode of ECB is the failure of the concrete cushion and yielding of the base plate and anchor bolts. Furthermore, a parametric analysis based on a verified finite element model was performed to investigate the influence of various parameters on the ultimate moment strength. Finally, a simplified strength model of ECB for L-shaped CFST based on the composite yielding method was proposed.

Experimental and Numerical Investigation on Seismic Performance of RC Exterior Beam-Column Joints with Slabs

The effect of a cast-in-place slab on the beam-column joint at beam ends in reinforced concrete (RC) structures under earthquake attacks has not been fully understood, and therefore, it is not manifestly addressed to some of the design criteria or specifications. Consequently, the contribution of slab to the seismic resistance of structures is often ignored or just included in an approximate manner. In this study, the experiment of two 1/2-scaled exterior beam-column joints without slabs and three 1/2-scaled joints with slabs under the combination of quasi-static repeated cyclic loading and constant axial force was carried out to investigate the effect of the cast-in-place slab on the seismic performance of exterior beam-column joints. The results show that for specimens EBCJ1 and EBCJ2 without slab, the decline was approximately 5%, while for specimens EBCSJ1 and EBCSJ3, the decline in the load is obvious and approximately more than 10%. For specimen EBCSJ2, which exhibited a slightly different behavior in the hysteresis curves, the maximum carrying capacity reached at the displacement of 70 mm during the first cycle. The cast-in-place slab has different effects on the failure mechanism and load transfer mechanism of the exterior beam-column joint, which depends on the column-beam moment strength ratio in the loading protocol. The slab has a positive effect on the energy dissipation capacity of the joint but has a negative effect on the load carrying capacity. In addition, finite element (FE) analysis of the tested specimens was conducted. The FE numerical models were established based on the construction information and loading conditions from the experiment and then validated by comparing them with the experimental observation.

Cyclic behavior of reinforced concrete columns with five-spiral reinforcement

Multi-spiral transverse reinforcement has been shown to provide superior seismic performance than conventional rectilinear tie reinforcement. This research intends to investigate the flexural behavior of the five-spiral transverse reinforcement configuration for square concrete columns. Large-scale flexure-critical five-spiral columns and counterpart conventional tied columns were tested under low (0.1fca′Ag) and high (0.3fca′Ag) constant axial load and subjected to double-curvature lateral cyclic loading. Test results showed that with 16%–29% less transverse reinforcement, the five-spiral columns displayed superior flexural strength, higher ductility, and larger drift capacities than the counterpart conventional tied columns. The five-spiral columns also showed improvements in the seismic capacity of the column in terms of energy dissipation. Furthermore, it was determined that the nominal moment strength could conservatively compute the actual moment strength of five-spiral columns. However, the five-spiral columns showed a higher flexural overstrength from the nominal moment than the counterpart tied columns. From the existing code methods examined in calculating the expected maximum moment, the Caltrans SDC 2019 method provided the best prediction of the maximum flexural strength of the columns, followed by the AASHTO 2017 method, then the ACI318-19 method. All three methods, however, could not fully capture the superior confinement effect of the five-spiral reinforcement.

Corrosion effect on the flexural behaviour of concrete filled steel tubulars with single and double skins using engineered cementitious composite

Concrete filled double skin tubular (CFDST) members are considered one of the most advanced construction composite forms, consisting of inner and outer tubes with concrete sandwiched between them. This paper presents an experimental study and theoretical analysis of the flexural performance of corroded concrete filled steel tubular (CFST), compared to CFDST beams with engineered cementitious composite (ECC) and normal concrete (NC). ECC is characterised by excellent tensile and flexural behaviour with crack control capacity, which shows great potential for enhancing the flexural behaviour of CFDST, especially in aggressive marine environments. In this study, a 500 µA/cm2 current density was implemented for 170 and 250 h to produce accelerated corrosion with mass losses of 6 % and 9 %, respectively, to investigate the effect of corrosion on the flexural behaviour of regular CFDST and CFDST with different types of infill material. Moreover, due to the shortcomings of normal concrete in preventing both the outward and inward buckling of steel plates, in this study an ECC was incorporated as the infill material between steel tubulars. The experimental results of all samples, including CFST and CFDST, showed that corrosion affects the flexural stiffness, ductility index, and energy absorption more than the ultimate moment strength. In addition, the highest impact of corrosion was for CFST with NC (CFST-NC), whereas the lowest effect was observed in CFDST with ECC (CFDST-ECC). Moreover, there is a lack of consideration regarding the impact of corrosion on the predicted flexural stiffness provided by existing codes. Hence, in this study, a theoretical flexural stiffness analysis was conducted and compared with various codes such as EC4, AIJ, BS5400, and AISC.

Experimental investigation of concrete-filled double-skin stainless steel tubular beam-columns

This paper presents an experimental investigation of the hysteretic behavior of concrete-filled double-skin stainless steel tubular (CFDSST) beam-columns with circular hollow section (CHS) outer and inner. A total of 18 specimens were designed and tested under constant axial compressive load and cyclically increasing flexural load to investigate the structural performance of the composite beam-columns and evaluate the effects of varied design parameters, including the thicknesses of the CHS outer and inner and concrete strength, on the performance of the hysteretic behavior of the CFDSST beam-columns. Both of the lateral load (P) versus lateral displacement (Δ) hysteresis response and moment (M) versus drift angel (θ) hysteresis response were obtained. Based on which, the failure mechanism, ductility, energy dissipation capacity, stiffness degradation, and ultimate strength of the specimens were investigated. The results show that the specimens failed in a ductile mechanism features bulge and rupture at the bottom of the CHS outer, unimpaired CHS inner, and local concrete crush, demonstrating the combined effect of the stainless tubes with the concrete. All of the specimens showed high level of ductility and energy dissipation capacity. Finally, comparisons of ultimate bending moments of the beam-columns between the test results and predictions from the existing design codes and design method demonstrate the deign codes underestimates bending moment strength of the CFDSST beam-columns.

Bending-strength evaluation of wide-flange steel beams subjected to local buckling at elevated temperatures

PurposeThe main purpose of this study was to propose theoretical calculation models to evaluate the theoretical bending strengths of welded wide-flange section steel beams with local buckling at elevated temperatures.Design/methodology/approachSteady-state tests using various test parameters, including width-thickness ratios (Class 2–4) and specimen temperatures (ambient temperature, 400, 500, 600, 700, and 800°C), were performed on 18 steel beam specimens using roller supports to examine the maximum bending moment and bending strength after local buckling. A detailed calculation model (DCM) based on the equilibrium of the axial force in the cross-section and a simple calculation model (SCM) for a practical fire-resistant design were proposed. The validity of the calculation models was verified using the bending test results.FindingsThe strain concentration at the local buckling cross-section was mitigated in the elevated-temperature region, resulting in a small bending moment degradation after local buckling. The theoretical bending strengths after local buckling, evaluated from the calculation models, were in good agreement with the test results at elevated temperatures.Originality/valueThe effect of local buckling on the bending behaviour after the maximum bending strength in high-temperature regions was quantified. Two types of calculation models were proposed to evaluate the theoretical bending strength after local buckling.