Cellular Steel Research Articles

Numerical investigation on effective spans ranges of perforated steel beams

Perforated steel beams (PSBs) have become very common because of their beneficial implementations in the construction of buildings. In this research a finite element model (FEM) is developed for analyzing the load bearing capacity of PSBs compared to the parent beams. An extensive parametric study is used to investigate the effects of web opening shapes, cutting length and load configurations to obtain the minimum span to depth ratio (L/D) of PSBs that have more failure capacity relative to the native steel beams. Moreover, a localized axial-bending (P-M) interaction curves involving nonlinear response in both geometry and material configurations are established in order to evaluate vierendeel and flexural mechanisms. The P-M curves emphasis that PSBs with sinusoidal web openings has a higher load bearing capacity than those with traditional circular or hexagonal openings. Finally, practical design method is proposed to help the designers to overcome the uncovered parts of ASCE specifications for design of other castellated and cellular steel beams (CSBs) which have sinusoidal and elongated circular web opening shapes.

Finite Element Analysis of Coated (Intumescent Coating Protection) Cellular Steel Beam (CSB) Expose to Fire

Traditionally, standard composite steel beam section acts as a load bearing structural element to sustain an external load. However, in the event of fire, an additional fire load acts on the composite steel beam section. The combined action of the former and latter would accelerate the vertical deformation of the beam. In the case of cellular steel beam (CSB), the vertical deformation predicted to be higher. Due to these circumstances, the structural behaviour of the composite CSB were compromised leading to the critical failure mode of web-post buckling and Vierendeel bending failure. Therefore, it is crucial to evaluate the behaviour of the composite CSB at elevated temperature under both loading action. In this research work, validation process was initiated between the numerical simulation analysis of CSB exposed to the fire with the readily available experimental data work. The validated model was then used to simulate the composite CSB with newly added fire protection material of intumescent coating. From the finite element simulation, the predicted vertical deformation slightly decreased for thicker intumescent coating application onto the beam surface. In conclusion, by applying the intumescent coating, further improvements were predicted for the vertical deformation and subsequently maintains the strength of the composite CSB at elevated temperature.

Development of Hybrid Machine Learning Models for Predicting the Critical Buckling Load of I-Shaped Cellular Beams

The principal purpose of this work is to develop three hybrid machine learning (ML) algorithms, namely ANFIS-RCSA, ANFIS-CA, and ANFIS-SFLA which are a combination of adaptive neuro-fuzzy inference system (ANFIS) with metaheuristic optimization techniques such as real-coded simulated annealing (RCSA), cultural algorithm (CA) and shuffled frog leaping algorithm (SFLA), respectively, to predict the critical buckling load of I-shaped cellular steel beams with circular openings. For this purpose, the existing database of buckling tests on I-shaped steel beams were extracted from the available literature and used to generate the datasets for modeling. Eight inputs, considered as independent variables, including the beam length, beam end-opening distance, opening diameter, inter-opening distance, section height, web thickness, flange width, and flange thickness, as well as one output of the critical buckling load of cellular steel beams considered as a dependent variable, were used in the datasets. Three quality assessment criteria, namely correlation coefficient (R), root mean squared error (RMSE) and mean absolute error (MAE) were employed for assessment of three developed hybrid ML models. The obtained results indicate that all three hybrid ML models have a strong ability to predict the buckling load of steel beams with circular openings, but ANFIS-SFLA (R = 0.960, RMSE = 0.040 and MAE = 0.017) exhibits the best effectiveness as compared with other hybrid models. In addition, sensitivity analysis was investigated and compared with linear statistical correlation between inputs and output to validate the importance of input variables in the models. The sensitivity results show that the most influenced variable affecting beam buckling capacity is the beam length, following by the flange width, the flange thickness, and the web thickness, respectively. This study shows that the hybrid ML techniques could help in establishing a robust numerical tool for beam buckling analysis. The proposed methodology is also promising to predict other types of failure, as well as other types of perforated beams.

Predicted temperature development on protected cellular steel beam (CSB) under fire exposure

Purpose This paper aims to investigate the predicted temperature behaviour of the protected cellular steel beam (CSB) with circular web openings at elevated temperature through finite element simulation. Design/methodology/approach Temperature development along the CSB were analysed and used for parametric investigation. In addition, this research paper investigates the novelty application of various intumescent coating thicknesses covering the whole CSB to cut down the temperature development along the beam section. Findings From the simulation outcomes, it shows that intumescent coating has a significant effect in reducing the temperature development along the CSB section. Thicker intumescent coating contributes to a higher temperature drop at the bottom tee section than the upper tee section. Originality/value The use of structural CSB has gained popularity among engineers and architects. This type of beam allows serviceability ducts and pipes to pass through the main steel web section under the flooring system, thus providing larger headroom for designers. Nevertheless, in any structural steel building, it is highly risky for CSB to be exposed to fire hazard if it were triggered accidentally. To mitigate and reduce fire exposure risk which might compromise the strength and stiffness of CSB, a passive fire protection is proposed to minimise the risk. One of the common passive fire protection materials used for steel beam section is intumescent coating. Intumescent coating is by far the cheapest solution to protect CSB as compared to other passive fire protection system. Intumescent coating can absorb some portion of heat exposure which subsequently translates a lower temperature development along the CSB section.

Comparing the embodied carbon and energy of a mass timber structure system to typical steel and concrete alternatives for parking garages

As operational energy use is minimized through high-performance design, construction and systems, the embodied carbon and energy from building materials and construction will play larger roles in the environmental impact of buildings. Consequently, the structural system should be a primary target for reducing the embodied carbon and energy of a building. Parking garages offer an ideal case study for comparing the embodied carbon and energy of different structural systems. As parking garages have little operational energy use and have few materials or systems, the embodied carbon and energy of the structure comprises a majority of the environmental impacts during its life-cycle. This study uses manual material take-offs from construction documents of four parking garages with one-way spans; one pre-cast concrete, one post-tensioned concrete, one cellular steel and one mass timber. The resulting comparison shows that there is little difference in the embodied carbon and energy of structural systems used for parking garages under best material practices. Mass timber, while more viable in a worst-practices scenario, loses its advantages when cement replacement and high recycled content steel are utilized.

Study of Neural Network Models for the Ultimate Capacities of Cellular Steel Beams

Artificial neural network (ANN) models were applied for simulating and predicting the ultimate capacities of cellular steel beams. To do this, at the first, different neural networks by various learning algorithms and number of neurons in the hidden layer were simulated. The required data for networks in training, validating, and testing state were obtained from a reliable database. Next, the best network according to its predictive performance was chosen, and a new formula was derived to predict the failure loads of cellular steel beams subjected to LTB. The attempt was done to evaluate the most exact practical formula using different algorithm and method for LTB strength assessment of cellular beams. Next, a comparison was made between the ANN-based formula and a formula based on the stepwise regression (SR) to show the predictive power of the ANN model. The results provided some evidence that ANN model obtained more accurate predictions than SR model. At the end, a sensitivity analysis was developed using Garson’s algorithm to determine the importance of each input parameter which was used in the proposed ANN formulation.

Practical Design Methods for Fire Resistance of Restrained Cellular Steel Beams

Thermal responses of steel beams under fire can be intricate, considering the coupling effects between material thermal-expansion, mechanical property degradation, and constraints by surrounding structural members. While research efforts have focused on catenary action of structural members without initial imperfections, few accurate and efficient methods are found to reveal the fire resistance of restrained cellular steel beams (RCSBs). In this paper, parametric and regression analysis are applied to investigate the thermal behavior of RCSBs with initial imperfections. Eight groups of RCSBs are set up to demonstrate how various design parameters may affect structural responses at elevated temperatures. The results indicate that axial restraint stiffness ratio, load ratio, and opening diameter-to-height ratio significantly affect the structural responses of RCSBs in fire, followed by the rotational restraint stiffness ratio and span-to-depth ratio as secondary effects. Through the orthogonal and regression analysis, simplified formulas for four characteristic temperatures and four characteristic internal forces are defined, which agree with finite element results to a certain extent. Meanwhile, reasonable range of each design parameter is put forward for a more efficient and applicable calculation of thermo-mechanical responses of RCSBs. The proposed formulas are practical, convenient and accurate enough to be applied for engineering design.

Performance Based Approach of Cellular Steel Beam (CSB) Exposed to Fire

This paper presents a numerical analysis of simply supported cellular steel beam (CSB) at elevated temperatures. Currently, CSB is increasingly used as the main structural element in multi-storey buildings, warehouses and any steel structures. Typical steel beams are mainly used as a dwelling load bearing capacity. CSB is one of the options to replace the former steel beam. Several advantages can be gained when adopting CSB as the main structural element in structures. However, several drawbacks have restricted the structural performance of CSB under applied load, especially under fire exposure. Fire is one of the major catastrophe that may endanger any structural steel member in a steel frame building under certain duration. It is important to reduce the member temperature induce by fire exposure to prolong the time before the CSB failed. Experimental data available in the literature review will be used to validate with numerical simulation in this research.

Neural networks for lateral torsional buckling strength assessment of cellular steel I-beams

An artificial neural network model was developed as a reliable modeling method for simulating and predicting the ultimate force capacities of cellular steel beams. The required data in training, validating, and testing states were obtained from a reliable database. A new formula based on the artificial neural network was proposed to predict the failure loads of cellular steel beams subjected to lateral torsional buckling. The attempt was done to evaluate a practical formula considering all parameters which may affect the lateral torsional buckling strength. Then, a comparison was made between the proposed formula and the predictions obtained from Australian Standard (AS4100). The results provided some evidence that proposed formula obtained more accurate predictions than AS4100 design guides. Finally, a sensitivity analysis was developed using Garson’s algorithm to determine the importance of each input parameters.

Study of Strategies for Forming Stainless Steel Objects with Cellular Structures by Selective Laser Melting

Selective laser melting (SLM) technology, which exhibits high printing resolution capacity, in used in order to prepare objects with cellular structures corrosion-resistant steel (316L). Cellular structures are considered as promising elements for topological optimization with the aim of reducing weight and giving an object special properties. The effect is studied in this work of strategies for laser beam scanning on an object being formed with a cellular BCC structure of steel 03Kh16N15MZ during SLM in an SLM280 unit. It is shown that depending on production regimes for object preparation with these structures there are changes in cellular structure strut minimum diameter, nature and distribution of defects, and mechanical properties.

Finite Element Modelling of the Structural Behaviour of a Novel Cellular Beam Non-composite Steel Structure in Fire

A novel cellular beam structure (CBS) intended for two to ten storey office buildings has been developed by the Southern African Institute of Steel Construction (SAISC) which consists of prefabricated modules comprising of cellular steel beams encased in a multi-layered flooring system, which yields an innovative structure with many benefits, including reduced construction time and cost. However, a major obstacle to commercialisation is the unknown fire resistance. Thus, this paper presents a series of non-linear finite element models that simulate the structural behaviour of the CBS under standard and parametric fire conditions. The simulations include single structural elements in isolation and global structure models. Overall, it was found that the CBS performs satisfactorily in a fire, provided that the integrity of the ceiling system can be maintained. However, significant lateral deflections up to 185 mm are predicted in a standard fire, which threatens the integrity of the ceiling. Under parametric fire conditions, a cooling phase suggests that there is negligible permanent deformation after a fire, due to the flexibility of the structure. Ultimately the results are used to make recommendations that: (a) steel end connections are designed to provide negligible moment restraint (b) slotted bolt holes are provided to allow free thermal expansion, and (c) the ceiling system is carefully detailed to accommodate the predicted lateral deflections, thereby safeguarding the integrity.

On Mechanical Properties of Cellular Steel Solids With Shell-Like Periodic Architectures Fabricated by Selective Laser Sintering

Historically, the approach in material selection was to find the proper material that serves a specific application. Recently, a new approach is implemented such that materials are being architected and topologically tailored to deliver a specific functionality. Periodic cellular materials are increasingly gaining interest due to their tunable structure-related properties. However, the concept of structure–property relationship is not fully employed due to limitations in manufacturing capabilities. Nowadays, additive manufacturing (AM) techniques are facilitating the fabrication of complex structures with high control over the topology. In this work, the mechanical properties of additively manufactured periodic metallic cellular materials are investigated. The presented cellular materials comprise a shell-like topology based on the mathematically known triply periodic minimal surfaces (TPMS). Maraging steel samples with different topologies and relative densities have been fabricated using the powder bed fusion selective laser sintering (SLS) technique, and three-dimensional printing quality was assessed by means of electron microscopy. Samples were tested in compression and the compressive mechanical properties have been deduced. Effects of changing layer thickness and postprocessing such as heat treatment are discussed. Results showed that the diamond TPMS lattice has shown superior mechanical properties among the examined topologies.

Numerical study of inelastic buckling behavior of rectangular steel plates with circular openings under shear forces

Cellular steel beam is flanged steel beam with circular openings of uniform diameter and distance between each opening. The main benefit of such beam is to reduce the structural weight without reducing the strength significantly. A rectangular steel plate with circular opening is frequently used as a model of a web panel of such beam with vertical web stiffeners. The dimension of the plate is the dimension of the web bounded by top and bottom flanges and two adjacent vertical stiffeners. In this research, finite element method is utilized to perform inelastic buckling analyses of rectangular steel plates with circular openings under shear forces along all four edges assuming steel as elastic-perfectly-plastic material with yield stress of 250 MPa. Both nonlinear geometry and nonlinear material are considered in the analyses. The objective of this research is to study buckling behavior of the plate in terms of buckling mode, critical load, and Von Mises (effective) stress distribution. The buckling shear loads of the plates of various length-to-width ratios of the plate (1.0, 1.25, and 1.50) and various opening-diameter-to-plate-width ratios (0.00, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50) have been obtained from the analyses. The deformation and Von Mises stress distribution at every load level have been obtained as well from the finite element analyses. Equation to predict inelastic buckling shear force of a rectangular steel plates with circular opening under shear forces is proposed in this study. Verification of the method has been performed by comparing shear buckling loads resulted from finite element analyses with the analytical results in the elastic range.

Strength and Axial Behavior of Cellular Lightweight Concrete-Filled Steel Rectangular Tube Columns under Axial Compression

This paper presents the experimental results on the strength and axial behavior of rectangular steel tube columns filled with cellular lightweight concrete (CLC) under axial compression. A total of 24 specimens, including 6 reinforced cellular lightweight concrete (RCLC) columns and 18 cellular lightweight concrete-filled steel tube (CLCFT) columns are investigated. The nominal dimension of the rectangular columns are 150×75 mm in cross-section and 750 mm in height. The parameter used in all tests are the ultimate compressive strengths of the CLC, which are 15 MPa, 20 MPa and 25 MPa, and the wall thicknesses of steel tubes, which are 3.0 mm, 4.5 mm and 6.0 mm. All specimens are prepared and loaded concentrically in axial compression to failure. The results of these tests demonstrated that the CLCFT columns have a linear behavior up to the approximately 80-90% of their maximum compressive load. Then, the behavior of the columns is nonlinear. The nonlinear behaviors are due to the crushing of the concrete core and local wall buckling of the steel hollow tube. In addition, it is found that the CLCFT columns have high axial deformability at the failure when compared to the reference RCLC columns. Finally, by comparing the maximum compressive load of the test results with those obtained from the ACI composite design equation, the comparison results show that calculation formula in ACI code can be applied to compute the axial capacity of CLCFT columns under axial compression.

Neural Network-Based Formula for the Buckling Load Prediction of I-Section Cellular Steel Beams

Cellular beams are an attractive option for the steel construction industry due to their versatility in terms of strength, size, and weight. Further benefits are the integration of services thereby reducing ceiling-to-floor depth (thus, building’s height), which has a great economic impact. Moreover, the complex localized and global failures characterizing those members have led several scientists to focus their research on the development of more efficient design guidelines. This paper aims to propose an artificial neural network (ANN)-based formula to precisely compute the critical elastic buckling load of simply supported cellular beams under uniformly distributed vertical loads. The 3645-point dataset used in ANN design was obtained from an extensive parametric finite element analysis performed in ABAQUS. The independent variables adopted as ANN inputs are the following: beam’s length, opening diameter, web-post width, cross-section height, web thickness, flange width, flange thickness, and the distance between the last opening edge and the end support. The proposed model shows a strong potential as an effective design tool. The maximum and average relative errors among the 3645 data points were found to be 3.7% and 0.4%, respectively, whereas the average computing time per data point is smaller than a millisecond for any current personal computer.

A Finite Element (FE) simulation of naked solid steel beam at elevated temperature

This paper presents the numerical analysis of temperature distribution of a simply supported naked solid steel beam under fire exposure. Prescriptive based approach particularly is the safest and easiest approach to determine the level of strength of structural member when expose to elevated temperature. However, this method assuming uniform fire exposure through the overall cross section of the structural member which may leads to over design. The outcome of the design may not reflect the real fire scenario. Performance based approach is a realistic approach which can predict the structural steel behavior. In this method, three main components were considered, namely fire exposure behavior, heat transfer analysis and mechanical reaction. Fire exposure behavior dealing with types or severity fire load exposed to structural member. There are few options available to determine the fire extent, namely nominal fire models, compartment fires, localized fires, zone models and computational fluid dynamics (CFD) models. Meanwhile, heat transfer analysis estimates the energy dissipation (initiate from fire) between structural elements due to temperature variation. Structural response incorporates finite element modeling that predicts the structural element behavior, namely stresses and deformation. This method considers the prime factors such as shadow effect, support condition, loading condition, boundary conditions and interaction properties between different structural elements which can optimize the structural behavior analysis. However, there are still lack of research that consider those factors that might jeopardize the behavior of steel beam. Owing to this, a performance based approach method was introduced in this research. Experimental investigation was retrieved from the readily available data of Compendium of UK Standard Fire Test Data. One sample of naked solid steel beam was selected from the wide range of naked solid beam available from the Compendium. Standard fire curve of ISO 834 was used during numerical simulation to correlate with the experimental investigation. From the results of the finite element simulation, the predicted member temperature agrees well with the experimental investigations. Hence, future works of cellular steel beam (CSB) with various web opening shapes can be initiate due to its limited researches related to CSB at elevated temperatures

Lateral-torsional buckling of cellular beams according to the possible updating of EC3

Researchers have not yet reached a consensus on which buckling curve to use for the calculation of the lateral torsional buckling (LTB) resistance of cellular steel beams in the current version of EC3. In addition, there is a new proposal for the future update of EC3, in which the imperfection factor is a function of the elastic section modulus, as well as material imperfections. The aim of this study is to investigate the LTB resistance of cellular steel beams by modifying the distribution of residual stresses after the manufacturing process. Geometrical and material nonlinear analysis are performed using the software ABAQUS 6.12. The cellular steel beams are simply supported, with fork-supports at the end, and subjected to uniform bending, mid-span concentrated load and uniformly distributed loads. In the latter two cases, neutral and destabilizing effects of loading are considered. The results are compared to analytical procedures, international standards, and also, with the possible EC3 updating. It was concluded that the calculation prescription of the new proposal, considering the imperfection factor that meets the magnitude of the residual stresses after the manufacturing process of cellular steel beams, is effective, accurate and conservative for LTB resistance in inelastic and elastic behavior. However, for the case of stocky cellular steel beams, whose shear stress is preponderant, ultimate limit states, such as Vierendeel mechanism and web post buckling, must be verified first.

Analysis of the stability bearing capacity of biaxial bending cellular steel column with circular hole

In order to promote the application and promotion of the cellular steel columns in practical engineering. Considering the geometric initial defect, geometric nonlinearity, material nonlinearity and residual stress. Using ABAQUS to analyze the effect of parameters of axial pressure, hole spacing, member length, hole size and flange width-thickness ratio on the stability bearing capacity of the cellular steel column, and get the influence of various parameters. The results show that with the increase of the axial pressure, member length and hole size, the stability bearing capacity of the cellular steel column decreases. With the increase of the hole spacing and flange width-thickness ratio, the stability bearing capacity of the cellular steel column increases. It is found that axial pressure, member length and flange width-thickness ratio have a great influence on the stability bearing capacity of cellular steel columns.

Influence of transverse rebars on bond between steel reinforcement and cellular concrete with very low compressive strength

Abstract Cellular concrete is a lightweight concrete obtained by aerating agent, which produces air-voids into the mixture. This work deals with bond between cellular concrete and steel rebars. Pull-out tests of 4,2 mm diameter rebars partly immersed into concrete cylinders were made. Concrete unit weight variation and setting of a transverse rebar into the concrete cylinder center constitute the variables of the work. Three types of mixture were prepared: one without aerating agent (with a dry unit weight of 2255 kg/m3), and two with different aerating agent rates (with a dry unit weight equal to 1565 and 1510 kg/m3). The study revealed the large decrease of bond stress between 4,2 diameter rebars and cellular concrete, due to concrete unit weight reduction. Transverse rebar introduced into concrete cylinder center increased the ultimate pull-out force of the test: the gain of bond produced by the transverse rebar grew up when the cellular concrete unit weight had been reduced. Therefore, special anchorages (not exclusively straight), permitting bond improvement between cellular concrete and rebars could be a solution to improve the mechanical performance of cellular concrete.

A Numerical Investigation into the Ultimate Strength of Steel Cellular Beams with Semi-Rigid Connections

Over the past several years, extensive theoretical, numerical and experimental research has been carried out on the structural behavior of steel beams with web openings of various shapes. However, in all these studies, cellular beams have always been treated or designed as simply supported at their ends. In other words, the beam to column connections are assumed as nominally pinned. The main aim of the present paper is to perform numerical simulations to determine whether the use of end plate connections, instead of simple connections, could enhance the global bending and/or shear capacity of cellular beams with circular and sinusoidal web openings.Interaction between a circular or sinusoidal opening in the beam web and endplate connection has also been studied. Data obtained from a number of experimental research programs on steel solid beam to column connections and simply supported cellular beams, available in the literature, were utilized to validate the numerical models developed in this paper. The numerical simulations using ABAQUS software were performed on full scale cellular steel beams connected to the columns with seven types of endplate connections. The results were compared with those obtained for similar simply cellular beams.