Steel Design Codes Research Articles

Mechanical properties of corner material in cold-formed steel structure: From normal strength to high strength

Cold-forming effect varies from normal strength steel to high strength steel due to the different chemical compositions and mechanical properties of parent materials. To date, research studies on material characterisation of cold–formed steels have been mainly focusing on the normal strength structural steel, while systematic research on high strength structural steel remains scarce. In this paper, an experimental investigation into changes in mechanical properties of high strength steel undergoing various levels of plastic deformation is firstly presented. The test results have been combined with other available high strength steel data, and compared to the normal strength steel data. Of the analysis results indicated, unified predictive equations, modified from Karren’s model in 1967 can predict the strength enhancement behaviours of normal strength and high strength steel, utilising the ultimate-to-yield strength ratio of parent materials fu,f/fy,f and inner radius-to-thickness ratio after cold–forming ri/t. Moreover, the decreases in the Young’s modulus, ultimate strain and elongation at fracture of normal strength and high strength steel after cold-forming can be predicted with no further grouping required. Statistical evaluation results confirm the accuracy of the proposed predictive expressions. This paper extends the scope of the strength enhancement equation in current north American cold-formed steel design code AISI S100–16 to high strength steels with grade up to 960 MPa, and provides key predictive material equations that can be further used in the design or numerical modelling of cold-formed steel structures.

Buckling performance of thin-walled filled steel columns

Concrete-filled composite elements have recently gained popularity as beams and columns all over the world. They have advantages similar to reinforced concrete elements, such as the moulding process and the lack of maintenance of the filled concrete, as well as advantages similar to hollow steel elements, such as enhancing compressive strength and bending capacity by using smaller sections. In this paper, the buckling behaviour of thin-walled steel columns with circular cross-section and different filling materials was investigated under uniaxial load. Six different materials (concrete produced using normal aggregate, concrete produced using waste aggregate, waste fine aggregate, waste coarse aggregate, waste iron dust and polyurethane) were used as filling. Filled columns were compared experimentally with hollow thin-walled steel columns that had the same height and diameter. All specimens had the same length (750 mm), same diameter (60.3mm) and the same wall thickness (3mm). Experimental results were compared with analytical results obtained from a calculation done using the national steel design code, Design, Calculation and Construction Principles of Steel Structures 2016. Additionally, columns specimens were modelled in Abaqus software. Conservative and consistent results were obtained from comparing experimental, analytical, and numerical results.

Comparative Analysis of Structure for Calamity by using Midas Gen, ETABS and STAAD pro

Abstract: During the past few years the earthquakes have dealt a lot of damage to life and property in India. To overcome this, the need for advancement in construction is necessary. With Scarcity of area and overgrowing population the need of constructing High Rise building has been increasing. Traditional high rise structures are tend to be weak against additional load pressure or earthquakes. To counter such situations and to reduce the effect of such calamity with the help of structural analysis and use of methods like Base Isolation, X bracing and Shear Wall, the intensity of such problem can be reduced to a wide extent. This paper represents the comparison of various methods on normal high rise building with the use of Midas Gen ,ETABS and STAAD pro..We took the case for Seismic zone 2 with medium soil category. Structural engineering software has progressed significantly in recent years. MIDAS GEN, ETABS and STAAD pro conducts structural design and analysis packages that support multiple types of concrete, steel, aluminum and timber international design codes.

A parametric study on shear deflection performance of open web steel joist

This paper focuses on doing a parametric analysis to ascertain the shear deflection of an open web steel joist under non-uniform bending utilizing theoretical and numerical studies. The goal of this work is to determine the significance of taking shear deflection into account when dealing with open web steel joists as well as how it interacts with changes in beam parameter variations. Using ABAQUS software, a total of forty finite element models were created. The differences between these models may be seen in the flange and web slenderness ratios, which are derived from the three standard steel design codes. Theoretical shear deflection was calculated using Timoshenko and Gere's equations, and flexural deflection for the point load case was calculated using conventional formulae. Since theoretical equations up to the elastic limit are known, the elastic behaviour of the joists is the focus of the whole research. The result compares the load to the maximum elastic deflection obtained by theoretical and finite element analysis and demonstrates strong collaboration, validating the numerical investigation. Additionally, a plot of load versus deflections was made for fewer models, with and without taking into account shear deflection, demonstrating the significance of this factor. Finally, the variance in shear deflection was shown by plotting the total elastic deflections versus the load for all the models with various values. The study's findings suggest that it is significant to take the impact of shear and determine the shear deflection in the case of structural components such open web steel joists. The analysis further reveals that an open web steel joist's shear deflection is greatly impacted by the parametric variation.

Novel Apex Connection for Light Wood Frame Panelized Roof.

Panelized fabrication of light-frame wood buildings has higher productivity than the traditional stick-built method. However, the roof production process is not very efficient due to the structural system and construction method. This study proposes a novel apex connection that allows for a folding mechanism in a panelized light wood frame roof system. Proof of concept of the proposed connection assembly is presented by a 3D printout of the developed connection. Following the steel design code and timber code, the initial estimation of different parameters, such as the pinhole diameter and number screws, were established. A detailed finite element analysis (FEA) was performed to determine the connection strength requirement for different load case scenarios. The results of the FEA and 3D printout of the assembly show that the proposed connection can provide the required folding mechanism before roof installation and can withstand the load in the unfolding state at service.

Experimental investigations on material properties and stub column behaviour of high strength steel irregular hexagonal hollow sections

Comprehensive experimental investigations into the material properties and stub column behaviour of cold-formed high strength steel (HSS) irregular hexagonal hollow sections (IHexHS) are presented in this paper. Apart from the tensile coupons taken from the parent plates, tensile coupons extracted from the flat and corner portions from the cross-sections were also tested in order to measure the effect of the fabrication process on material properties. The strength enhancement predictive models proposed by previous studies were compared with the obtained test results from corner coupons with increased strength due to the cold-forming effect. A total of 20 HSS IHexHS stub column specimens were tested under axial compression and the cross-section classification from the existing structural steel design codes of EN 1993-1-12, ANSI/AISC 360–16, AS 4100, AISI S100–16 and design approaches of DSM and CSM were compared and assessed against the obtained results. It was found that the design provisions of cross-section classification in current design codes cannot be extended to the HSS IHexHS stub columns. Based on current codified yield slenderness limits, the strength predictions from design codes exhibit conservatism without the consideration of strain hardening and beneficial effect of element interaction whereas cross-sections with intermediate slenderness values were over-predicted.

Experimental and numerical investigations of hybrid high strength steel welded T-section stub columns with Q690 flange and Q460 web

Comprehensive experimental and numerical investigations on mechanical properties of Q690 and Q460 high strength steel (HSS) sections and stub column behaviour of the 14 hybrid HSS welded T-section stub column specimens are presented in this paper. A total of six coupon specimens were longitudinally and transversely machined from HSS Q690 and Q460 steel parent plates respectively. Furthermore, initial local geometric imperfections measurements were also carried out. In parallel with the experimental investigation on stub column behaviour, extensive numerical studies were carried out by developing finite element (FE) models to replicate the experimental tests results. The validation of the FE models was confirmed against the obtained experimental data. To supplement the experimental data, validated FE models were used in the parametric studies, by which numerical specimens with a larger range of cross-section dimensions can be generated. Subsequently, cross-section classification slenderness limits for outstand plate elements under compressive load set out in structural steel design codes of EN 1993-1-12, ANSI/AISC 360-16, AS 4100 were evaluated against the experimental and numerical data. In addition to the design codes, design methods such as direct strength method (DSM) and continuous strength method (CSM) were also assessed to evaluate the applicability and suitability for hybrid HSS welded T-section stub columns. It was found that the current codified slenderness limits in EN 1993-1-12, ANSI/AISC 360-16 as well as AS 4100 for slender/non-slender outstand flat elements can generally be adopted for hybrid HSS welded T-section under compression. CSM provide under-estimated compressive resistance in comparison to the design codes and DSM for slender sections.

Design criteria for pin-ended hot-rolled and laser-welded stainless steel equal-leg angle columns

This paper explores an attempt to investigate the structural behaviour and design of equal-leg stainless steel angle columns fabricated by the laser-welding of individual hot-rolled plates and by hot-rolling process. The studies cover columns with pin-ended boundary conditions exposed to pure axial compression. An advanced and realistic finite element model able to replicate the buckling features of stainless steel angle columns is developed and validated against available experiments collected in the literature. Employing the validated finite element model, quantitative numerical parametric studies, considering minor-axis flexural buckling, as well as flexural–torsional buckling, are performed. Based on comprehensive benchmark data, the accuracy, safety and applicability of the existing column design procedures provided in the European and North American structural stainless steel codes are assessed. The evaluation results reveal that the North American codified design procedures lead to conservative and scattered resistance predictions, thereby demonstrating a need for their improvement. As a result of conducted studies, the new criteria for design of pin-ended hot-rolled and laser-welded stainless steel equal-leg angle columns are proposed. Their suitability for inclusion in the European structural stainless steel design code is confirmed by statistical reliability analyses in accordance with EN 1990.

The influence of structural and geometric imperfections on the LDB strength of steel–concrete composite beams

The behavior of structural steel frames is significantly influenced by the presence of structural and geometric imperfections. The structural imperfections, namely, the residual stresses, are generated during most manufacturing processes involving material deformation, heat treatment, machining or processing operations. As the residual stresses, the geometric imperfections are fundamental in the analysis of critical buckling and post-buckling behavior of thin-walled structures. These initial imperfections can be captured using the second order inelastic analysis, also known as advanced analysis. In the modern steel design codes, e.g., European code EC3, Australian code AS4100, North American Code AISC360-16 and Chinese code GB50017 the development of advanced numerical analyses is allowed to predict the behavior of steel and composite frames. However, the random nature of the shapes and magnitudes of the initial imperfections results in difficulties in developing these analyses. Therefore, this paper presents an assessment of the influence of structural imperfections, namely, the residual stresses, and geometric imperfections on the Lateral Distortional Buckling (LDB) strength of steel–concrete Composite Beams (SCCB). The basis of the research is a thorough comparison between numerical and experimental results. Several residual stress patterns found in the literature have been implemented in numerical simulations of four different tests on SCCB subjected to uniform hogging moment. In addition, a sensitive analysis of the geometric imperfection values, namely, the initial bending, was developed. The post buckling numerical analyses were developed with the ABAQUS software. The analysis shown in this work shall help the choice of the initial imperfections on future numerical simulations on SCCB.

Ramifications of blind adoption of load and resistance factors in building codes: reliability-based assessment

This paper presents a probabilistic approach to reveal the negative consequences of overlooking code calibration when adopting the provisions of nonindigenous building codes in design. A taxonomy of the national building codes of various countries whose provisions are adopted from one or more original standards is first presented. Next, the reliability-based approach to quantify the lack of safety that may arise due to the absence of code calibration is presented. This approach is then applied to the case study of the National Building Code of Iran, whose load and resistance factors are directly adopted from ASCE/SEI 7. To this end, seven steel building archetypes with various structural systems at various regions with different seismicity levels and site classes are designed according to the Iranian loading and steel design codes. Subsequently, 2510 structural elements, including beams, columns, and braces, from these archetypes are subjected to reliability analysis to compute their reliabilities. In this analysis, the uncertainty of material properties are quantified using local laboratory test data and the uncertainties associated with manufacturing tolerances of steel elements are quantified through extensive field surveys. The analysis results in reliability indices that are markedly smaller than the targets set by the original standards the Iranian code has adopted from, which exposes the notable lack of safety in the ensuing designs. Subsequently, the load and resistance factors are calibrated to achieve the target reliabilities. Among other changes, the results indicate the need for a 25% increase in the earthquake load factor, which reveals the lack of safety that is implicit in the current practice. Reliability sensitivity analysis is then employed to determine the sources of uncertainty that are most influential on the resulting reliabilities. The presented approach is immediately applicable to the assessment of the building codes of other countries.

The trends and practical look of advanced steel frame structures

The aim of the work is to present the trend of the advancement of steel design code and practical approach of steel frame design from the current AISC-LFDR to the advanced analysis. As the trend of steel frame analysis method is from first-order elastic analysis to second-order inelastic analysis which is an advanced analysis. Methods. In this paper the comparison between the load - displacement curves of several structural analysis methods is presented. Case studies are considered to analyze by different methods and comparison of practical advanced analysis method with PROKON software. The case studies includes a two-story one bay steel frame and four bays of twelve-stories steel frame. The results of first-order elastic, elastic buckling, second-order and nonlinear analyses of an unbraced frame are compared and their difference is presents. The proposed software for advanced methods demonstrates the accuracy and the computational efficiency in predicting the nonlinear analysis response of steel frame structures.

Design of fixed-ended octagonal shaped steel hollow sections in compression

In recent years, octagonal steel hollow sections (OctHSs) have attracted significant interests from researchers and engineers, and OctHSs have been employed in civil engineering applications. However, designs of OctHSs are not included in structural steel design codes. This paper therefore presents comprehensive numerical analyses on the stub column behaviour of OctHSs. A database of 46 stub column tests reported in 6 sources were collected. Different fabrication routes, steel grades and cross-sectional slenderness were covered. Finite element (FE) modelling was carried out to replicate the test observations. The validated FE models were subsequently adopted to conduct an extensive parametric study to supplement the test database. Existing design methods in North American specifications, ASCE standard, Eurocode, Australian code and recently published literature were thoroughly discussed and evaluated. It was found that existing design methods are not applicable to the design of OctHSs. New cross-sectional slenderness limits and modifications to the existing design methods were then proposed. The cross-sectional resistance obtained from different design methods were compared with test and FE results. The applicability of the modified design methods was confirmed by statistical analyses. The reliability of the modified design methods was finally verified through reliability analyses. Results indicate that the modified design methods can be used to accurately predict the resistance of OctHSs with accepted safety levels.

Dual assessment criterion and its programmed application of collapse failure of pressure vessels

Design standards of preventing “plastic collapse” and “excessive overall plastic deformation” for pressure vessels are given in the ASME BPVC Section VIII Division 2 and EN 13445, respectively. These two aspects are both taken into account in the dual criterion, which could avoid the two failure modes at the same time. And the dual criterion has been adopted as Appendix B in the forthcoming revised version of Chinese JB-4732-1995 “Steel Pressure Vessel-Analysis and Design Code”. In order to realize engineering application for the dual criterion, two feasible schemes to determine quasi-limit load is proposed in this paper, and the APDL (ANSYS Parametric Design Language) is used for the programming. A dual assessment criterion module is embedded in ANSYS finite element software. On this basis, a design example of the dual assessment criterion program is analyzed. The ANSYS dual criterion assessment module is used to conduct the assessment of different material models, different quasi-limit load determination methods and different levels of design loads. The results show that the dual assessment criterion module is effective for engineering practice.

Flexural-torsional buckling of austenitic stainless steel I-section beam-columns: Testing, numerical modelling and design

Abstract The flexural-torsional buckling response and design of stainless steel I-section beam-columns are investigated in this paper. First, a series of laboratory tests on laser-welded stainless steel I-section beam-columns susceptible to flexural-torsional buckling is presented. The results obtained are supplemented by further data generated by means of numerical parametric studies on both conventionally arc-welded and laser-welded stainless steel members covering a wide range of member slenderness and combinations of loading. Existing provisions for the design of welded stainless steel I-section elements against flexural-torsional buckling are then assessed and found to require improvement. Finally, new formulae for the design of stainless steel I-section beam-columns susceptible to flexural-torsional buckling are proposed. The new proposals yield improved accuracy and consistency over existing provisions and their suitability for inclusion in the upcoming version of the European structural stainless steel design code EN 1993-1-4 is confirmed by reliability analysis in accordance with EN 1990.

Review of Nonlinear Analysis and Modeling of Steel and Composite Structures

Structural steel frames exhibit significantly geometric and material nonlinearities which can be captured using the second-order inelastic analysis, also known as advanced analysis. Current specifications of most modern steel design codes, e.g. American code AISC360, European code EC3, Chinese code GB50017 and Australian code AS4100 permit the use of advanced analysis methods for the direct design of steel structures to avoid tedious member capacity checks. In the past three decades, a huge number of advanced analysis and modeling methods have been developed to predict the behavior of steel and composite frames. This paper presents a comprehensive review of their developments, which focus on beam-column elements with close attention to the way to capture geometric and material nonlinearity effects. A brief outline of analysis methods and analysis tools for frames was presented in the initial part of the paper. This was followed by a discussion on the development of displacement-based, force-based and mixed beam elements with distributed plasticity and concentrated plasticity models. The modeling of frames subjected to fire and explosion was also discussed. Finally, a review of the beam-column models for composite structures including concrete-filled steel tubular (CFST) columns, composite beams and composite frames was presented.

A refined approach to lateral-torsional buckling of overhang beams

The current South African Steel design code, SANS 10162-1, has a set of effective length factors for overhang beams which is independent of the geometrical properties of the beam and the lengths of the backspan and cantilever. This simple approach is consistent with several other international steel design codes and design guidelines. These effective length factors make no allowance for the stiffness of the adjacent span, but in reality warping at the supports allows interaction buckling between the cantilever and beam segments. In the research presented in this paper the backspan-to-overhang-segment ratio was investigated with the view of refining the calculations for determining the critical buckling moment of overhang beams. The scope was limited to beams with lateral and torsional restraints at the supports, and to shear centre and top flange loading applied at the free overhang end. Physical experiments and finite solid element analyses were used to determine the relationship between the critical moments and the beam buckling parameters. A simplified design calculation procedure was formulated, which includes a buckling parameter to include warping at the supports and allows interaction buckling between the beam segments. The buckling parameter is dependent on the size of the beam, the length of the overhanging segment and the ratio of backspan-to-overhang length.

Numerical study of two low rise eccentrically braced steel frames under Indonesia seismic load using ELM and DAM

Indonesia steel design code 2002 was revised in 2015. The latest version refers to AISC 360-10 which convert steel stability analysis to direct analysis method (DAM). DAM is an elastic analysis which includes second-order effect where P-delta and geometric imperfection are directly calculated during the analysis. Imperfection is modelled as notional load applied horizontally which is determined as 0.002 of gravity load. Numerical study using SAP software had been conducted to compare DAM and the previous method ELM on eccentrically braced frames (EBFs) under seismic load. It is known that EBF is one of earthquake resistant structural systems of steel structure. Numerical study was validated against experimental results performed by other researchers. Similar EBF frames used in the experiment were reanalyzed by ELM and DAM and coefficient of notional load is varied as 0.002 and 0.003. Seismic load applied in the analysis were varied based on three different seismic zones and soil conditions.

Time-dependent reliability analysis of railway overhead structures

Overhead structures play a vital role in the operation of electrified rail networks. They support overhead electrical wires that provide the necessary power to the operation of trains. Overhead structures are simple steel structures that lack redundancies and failure in a single location may cause significant deformation or complete collapse. Failures of these simple structures have substantial consequences which usually interrupt train service. These steel structures are exposed to the environment and gradual deterioration of steel due to corrosion jeopardizes their strength and serviceability. This paper presents a reliability-based method for strength assessment of portal overhead structures using the first order reliability method. In the resistance formulation, a modified corrosion decay model proposed in this article predicts the thickness loss of wide flange structural steel sections. Meanwhile, load effect formulation follows a structural steel design code and an industry standard. It is found that the bridge-mast connection and the attachment point to drop vertical on the bridge are the most critical parts during the service life of the structure. The reliability analysis presented in this work is an efficient mean for structural engineers to identify critical locations of overhead structure and facilitate asset managers to prioritize inspection and maintenance works for deteriorated overhead structures.

On the influence of the rounded corners on the local stability of RHS members under axial force and biaxial bending

This paper presents the results of an investigation concerning the influence of corners with standard radii in the local buckling behaviour of thin-walled rectangular hollow section (RHS) members subjected to combinations of axial force and biaxial bending. The calculation of the half-wave length leading to the minimum critical bifurcation load is performed by means of a Generalized Beam Theory (GBT) specialization, developed taking advantage of the assumption that the stress resultants are uniform along the member length. This assumption makes it possible to obtain semi-analytical solutions, adopting half-wave sinusoidal amplitude functions for the GBT cross-section deformation modes, and leads to a numerical implementation that (i) is able to quickly solve a large number of problems and (ii) provides physical insight into the critical buckling mode mechanics, through a shell-like stress resultant-based energy criterion, as well as the modal decomposition features of the GBT semi-analytical solutions. Members with cross-sections belonging to the EN10219-2 database are analysed and their critical buckling coefficients are compared with those provided by available analytical expressions and/or currently included in steel design codes, namely Eurocode 3 and the North American Specification for Cold-Formed Steel Members. Analytical expressions are developed to take into account the (usually) beneficial influence of the rounded corners to the RHS member critical buckling stress.

Optimal design of steel skeletal structures using the enhanced genetic algorithm methodology

This study concerns with the design optimization of steel skeletal structures thereby utilizing both a real-life specification provisions and ready steel profiles named hot-rolled I sections. For this purpose, the enhanced genetic algorithm methodology named EGAwMP is utilized as an optimization tool. The evolutionary search mechanism of EGAwMP is constituted on the basis of generational genetic algorithm (GGA). The exploration capacity of EGAwMP is improved in a way of dividing an entire population into sub-populations and using of a radial basis neural network for dynamically adjustment of EGAwMP’s genetic operator parameters. In order to improve the exploitation capability of EGAwMP, the proposed neural network implementation is also utilized for prediction of more accurate design variables associating with a new design strategy, design codes of which are based on the provisions of LRFD_AISC V3 specification. EGAwMP is applied to determine the real-life ready steel profiles for the optimal design of skeletal structures with 105, 200, 444, and 942 members. EGAwMP accomplishes to increase the quality degrees of optimum designations Furthermore, the importance of using the real-life steel profiles and design codes is also demonstrated. Consequently, EGAwMP is suggested as a design optimization tool for the real-life steel skeletal structures.