Mid-span Concentrated Load Research Articles

Numerical investigation of elastic-plastic buckling performance of circular arched cellular steel beam using nonlinear finite element analysis method

This study presents a numerical investigation of the in-plane elastic-plastic performance, post-buckling mode, and arched web-post shear resistance of a pinned end circular arched cellular steel beam using ABAQUS nonlinear finite element analysis package. The trustworthiness of the finite element analysis results was confirmed by comparing them to the existing experimental investigation results. The main study parameters, such as the effect of a rise-to-span ratio, the radius of curvature, the impact of opening, the types of loading on elastic-plastic performance, and the buckling mode of an arched cellular steel beam, were investigated. Furthermore, the arched web-post finite element model was proposed and the shear resistance of the arched web-post was investigated. Also, the appropriateness of the currently existing different web-post shear resistance analysis approaches was reviewed and evaluated in determining the shear resistance of arched web-posts. The results showed that the web post-structural stiffness of a circular arched cellular steel beam was improved as the rise-to-span ratio increased under the mid-span concentrated load regardless of the rise-to-span ratio. However, under uniformly distributed vertical load, increasing a rise-to-span ratio beyond 0.35 or 140° subtended angles reduces the stiffness of circular arched cellular steel beams. The web post shear resistance analyzing approaches proposed by Panedpojaman et al. and SCI P-100 overestimate and yield unsafe results in determining the web-post shear resistance of arched web post cellular steel of low rise-to-span ratio.

Effect of Web Post Width on Strength Capacity of Steel Beams with Web Openings: Experimental and Analytical Investigation

Day by day, technology has been changing progressively because of the remarkable hastening of research and development activities. Perforated beams are one such example of advancement in construction technology. Steel beams with web openings are those that have regularly spaced web openings along the length of the beam. The web openings are created in various ways such as wire cutting and welding. Castellated and cellular beams differ in the creation of web openings. Studies addressing the effect of web post width of steel beams with web openings on the strength capacity of beams are rare. Therefore, the objective of the present work was to examine the influence of web post width on the strength capacity of beams with web openings. First, experimental tests were carried out on three full-scale specimens of a steel beam with oval-shaped web openings, cellular beam, and solid web beam. The same beam was modeled using finite-element software ANSYS and the behavior was compared in terms of load–displacement curve and failure modes. Later, a detailed parametric study was carried out to study the behavior of beams with web openings having variation in web post width using nonlinear finite-element analysis. The simply supported steel beams with web openings subjected to midspan concentrated load with varying web post width and shape of openings were modeled and analyzed. From the analysis results, it was found that the shape of web openings and the web post width play an important role in the strength capacity of the perforated beams. The maximum strength reduction capacity was found to be 51.78% for hexagonal openings of depth 150 mm and having a web post width of 50 mm. The minimum strength reduction capacity was found to be 8.93% for hexagonal openings of depth 100 mm having a web post width of 500 mm. Web post width plays a significant role in the ultimate strength capacity of beams. Web post buckling is a predominant failure mode in steel beams with web openings and it can be prevented by maintaining sufficient web post width.

A Semi-Empirical Equation based on the Strut-and-Tie Model for the Shear Strength Prediction of Deep Beams with Multiple Large Web Openings

The behavior and shear strength of full-scale (T-section) reinforced concrete deep beams, designed according to the strut-and-tie approach of ACI Code-19 specifications, with various large web openings were investigated in this paper. A total of 7 deep beam specimens with identical shear span-to-depth ratios have been tested under mid-span concentrated load applied monotonically until beam failure. The main variables studied were the effects of width and depth of the web openings on deep beam performance. Experimental data results were calibrated with the strut-and-tie approach, adopted by ACI 318-19 code for the design of deep beams. The provided strut-and-tie design model in ACI 318-19 code provision was assessed and found to be unsatisfactory for deep beams with large web openings. A simplified empirical equation to estimate the shear strength for deep T-beams with large web openings based on the strut-and-tie model was proposed and verified with numerical analysis. The numerical study considered three-dimensional finite element models, in ABAQUS software, that have been developed to simulate and predict the performance of deep beams. The results of numerical simulations were in good agreement and exhibited close correlation with the experimental data. The test results showed that the enlargement in the size of web openings substantially reduces the elements' shear capacity. The experiments revealed that increasing the width of the openings has more effect than the depth at reducing the load-carrying capacity.

Experimental study of the behaviour and failure modes of tapered castellated steel beams

Abstract This article discusses the experimental testing of tapered castellated beams (TCBs) under mid-span concentrated load. These beams are created by cutting the webs of standard I-sections in a particular zigzag pattern and rejoining the two parts by placing variable expansion plates between web posts and welding them together. Generally, the depth of the mid-span will be increased. A standard I-section (IPE140) was selected as a parent beam to fabricate three TCB specimens and one prismatic castellated beam. The experimental results showed that the ultimate load capacity of the TCBs could be increased up to 140% of the ultimate load capacity of the parent section. Fabricating a TCB is an effective way of increasing the allowable load of a long-span member while remaining within International Building Code-defined deflection limits. The experimental results showed that the allowable load at deflection (L/360) increased up to 183% of the allowable load for the control specimen at the same deflection. Finally, the experimental results showed that web-post buckling and joint-weld rupture failure modes occurred in TCBs due to the formation of high shear forces that tried to twist the web posts.

Prestressing Effects on Full Scale Deep Beams with Large Web Openings¨: An Experimental and Numerical Study

Most studies on deep beams have been made with reinforced concrete deep beams, only a few studies investigate the response of prestressed deep beams, while, to the best of our knowledge, there is not a study that investigates the response of full scale (T-section) prestressed deep beams with large web openings. An experimental and numerical study was conducted in order to investigate the shear strength of ordinary reinforced and partially prestressed full scale (T-section) deep beams that contain large web openings in order to investigate the prestressing existence effects on the deep beam responses and to better understand the effects of prestressing locations and opening depth to beam depth ratio on the deep beam performance and behavior. A total of seven deep beam specimens with identical shear span-to-depth ratio, compressive strength of concrete, and amount of horizontal and vertical web reinforcement ratios have been tested under mid-span concentrated load applied monotonically until failure. The main variables studied were the effects of depth of the web openings and the prestressing location on deep beam performance. The test results showed that the enlargement in the size of web openings substantially reduces the element’s shear capacities while prestressing strands location above the web openings has more effect at increasing the element’s shear capacities. The numerical study considered three-dimensional finite element models that have been developed in Abaqus software to simulate and predict the performance of prestressed deep beams. The results of numerical simulations were in good agreement with the experimental ones.

Lateral-torsional buckling resistance of cellular steel beams at room temperature and fire situation

This research deals with the structural behavior of cellular steel beams, focusing on the lateral-torsional buckling limit state at room temperature and fire situation. First, a finite element model was proposed using ABAQUS and validated with experimental results available in the literature. The numerical model was used to perform a parametric study of cellular beams simply supported and subjected to uniform bending. The parametric study assessed twenty hot-rolled parent sections, six groups of diameter and spacing of openings, different values of slenderness, two structural steels, the room temperature case, and seven more target temperatures between 200 °C and 800 °C, totaling 12,306 analyses. Based on the parametric study, a unified procedure was proposed in order to evaluate the lateral-torsional buckling resistance of cellular steel beams at room temperature and fire situation. The proposed resistance curves were also evaluated with the results of 2001 additional analyses of cellular beams subjected to uniformly distributed loads, and mid-span concentrated loads. Compared to other procedures available in the literature, the new proposals presented a better agreement with all ranges of geometries, steel grades, temperatures, and loads investigated.

Reassesment of lateral torsional buckling in hot-holled I-beams

Lateral torsional buckling (LTB) of I-beams is characterized by simultaneous lateral deflection and twist. In this paper the influence of destabilizing and neutral effects of loadings and the possibility of the occurrence of web distortion, which characterizes the lateral distortional buckling (LDB), is numerically investigated. Recent research has shown divergences between the standard procedures of the American Institute of Steel Construction, Australian Standards and Eurocode with LTB numerical results. In addition, some procedures have recently been proposed for correcting possible deviations between the results of numerical analysis and standard procedures. In order to investigate this situation, elastic stability and physical and geometrical nonlinear analyzes are performed, using GBTul and ABAQUS softwares, respectively. The numerical model is calibrated considering experimental tests. The beams are simply supported, with fork supports at the ends, and subject to neutral and destabilizing effects of loading. The beams are subject to uniform bending, mid-span concentrated load and uniformly distributed loads. The parametric study is performed by varying the geometric cross section parameters. The results are compared with international standards and analytical procedures. It is concluded that the influence of destabilizing and neutral effects of loadings is responsible for providing non-conservative results when compared to the American Institute of Steel Construction procedure. The occurrence of LDB in hot-holled I sections influences the lateral stability strength of I-beams, but it is not predominant. With the possibility of using the elastic critical moment obtained by the elastic stability analysis, the conservative situation of EC3 is verified. The Australian Standards procedure is in agreement with all the situations analyzed.

Application of precast foamed concrete panels for the structural deck of green roof system

Rapid development in urban areas has caused many environmental problems, one of which is the phenomenon of urban heat island (UHI) which results in excessive energy usage. The building sector is the most responsible for energy use, which accounts for 40% of total energy consumption. A green roof is a sustainable solution to solve the problems related to urban heat islands. To reduce more structural self-weight, lightweight foamed concrete could be applied as a roof construction material. This paper presents experimental results on the structural behavior of a U-shape precast panel made of lightweight foamed. Three foamed concrete panels in the U-shaped form having different width dimensions of 200mm, 400mm and 600mm with a clear span of 1800 mm were cast and tested until failure under a double mid-span concentrated load. The panels were considered as a simple U-shaped beam filled with a growing medium for a green roof system. This result shows a potential use of foamed concrete for roof deck structure integrated with a green roof system. The U-shaped panel with a width of 400mm is the optimal form of the three tested specimens for the structural roof deck of the green roof system.

Assessment of lateral distortional buckling resistance in welded I-beams

Lateral distortional buckling (LDB) of I-beams is characterized by simultaneous lateral deflection, twist and cross section change due to web distortion. The present study investigates the effect of web distortion in LDB resistance of doubly-symmetric welded I-beams. Elastic stability and physical and geometrical nonlinear analyses are performed, using GBTul and ABAQUS softwares, respectively. The numerical model is calibrated considering experimental tests. The beams are simply supported, with fork supports at the ends, and subject to neutral and destabilizing effects of loading. The beams are subject to uniform bending, mid-span concentrated load and uniformly distributed loads. The parametric study is performed by varying the geometric cross section parameters. The results are compared with international standards and analytical procedures. It is concluded that the occurrence of LDB is responsible for the resistance reduction, especially for the slender web sections. With the elastic stability analysis, it is possible to estimate the critical moment for the calculation of the ultimate moment considering the LDB. It is found that there is no need to propose a new solution for the determination of LDB resistance, since some procedures allow the use of the elastic stability analysis response for the calculation of the ultimate moment, such as EC3. However, some adjustments can be made to the ANSI/AISC 360–16 and AS 4100: 1998 standards, since the results compared to these procedures are not conservative.

LRFD for Lateral-Torsional Buckling Resistance of Cellular Beams

Cellular beams are those that present sequential web openings along the span, and are produced by thermal cutting and welding. Studies addressing the lateral-torsional buckling resistance curve of cellular beams according to the American standard are scarce. The objective of the present study is to investigate the lateral-torsional resistance in cellular beams, considering the Load and Resistance Factor Design. To this end, geometrical and material nonlinear analyses are conducted. The cellular beams are simply supported, with fork supports at the ends, and subjected to three types of loading: uniform bending, mid-span concentrated load and uniformly distributed loads. The geometric parameters of cross section and unrestrained length are varied. Results are compared with the nominal and design flexural strength. Failure modes are associated with non-dimensional lateral-torsional stiffness. Considering the application of uniform bending moment, failure modes such as LTB and WDB + LTB occurred. In contrast, considering the presence of shear stress, failure modes such as the Vierendeel mechanism, WPB, and WPB + LTB occurred. It was concluded that when compared with the numerical model results, the design flexural strength was ineffective under inelastic buckling regime, a situation in which interaction of modes of failure can occur. When considering only the pure lateral-torsional bucking, the Load Resistance Factor Design variation was observed. This variation presented an average value equal to 0.83, differing from the procedure in question by approximately 7.8%.

Experimentally Comparative Study on Different Strengthening Methods of Reinforced Concrete Deep Beams

The aim of this study is to investigate the effect of strengthening reinforced concrete deep beams. An experimental study was done using six reinforced concrete deep beams have the same dimensions of 1150×800×150 mm, and subjected to mid-span concentrated load up to failure. Beams were different in the type, Location of strengthening and the ratio of reinforcement. Beams were divided into three groups. The first group included beams strengthened internally by single strut and either vertical or horizontal additional reinforcement. The second group included beams strengthened using double embedded strut or using CFRP as external strengthening. The third group included one beam strengthened using inclined stirrups. One of the specimens was tested without any strengthening and one specimen was strengthened by external CFRP sheets for comparison purposes the results of the experimental study shown remarkable improvement for using each type of strengthening. Results shown that using the mechanism of increasing stirrups by double rate and using single strut reinforcing is the optimum choice. This is due to the fact that this type of strengthening provides significant increase in the beam capacity in additional to the enhanced behavior of the beam. By this study comparison between each type of strengthening was done and the optimum type to be used in accordance with parameters of gained load capacity of tested deep beams.

Composite concrete beam with multi-web cold-formed steel section

Lately, structural engineers use cold-formed steel sections (CFS) in buildings due to its light-weight and easy shaping. Encasing the cold-formed steel sections by concrete avoiding the structure elements some of its disadvantages especially buckling. This paper reports an experimental test program for beams with a multi-web cold-formed steel section encased by reinforced concrete. Eleven (full-scale) specimens have tested under mid-span concentrated load, the experimental test program designed to cover many cold-formed steel section variables such as (web number, web height, and the steel section length). Comparison between the experimental results for specimens with encased steel cold-formed section and that for reference beam have presented. The experimental results show that the cold-formed steel webs number has a noticeable influence on the structural behaviour of the beam, such as increasing the beam load capacity. The beam load capacity, failure mode and the beam ductility have analysed, and some preparatory criteria for a sufficient outline have presented.

The moment-gradient factor in lateral– torsional buckling of castellated steel beams under mid-span concentrated load

The moment-gradient factor in lateral– torsional buckling of castellated steel beams under mid-span concentrated load

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.

Flexural characteristics of lightweight ferrocement beams with various types of core materials and mesh reinforcement

Sixteen reinforced concrete beams having the cross-sectional dimensions of 100 × 200 × 2000 mm and clear span of 1800 mm were cast and tested until failure under a single mid-span concentrated load. Ferrocement beams in this research contained either an Autoclaved Aerated lightweight brick Core (AAC), Extruded Foam Core (EFC), or a Lightweight Concrete Core (LWC); and were reinforced with either Expanded Metal Mesh (EMM), Welded Wire Mesh (WWM) or Fibre Glass Mesh (FGM). Structural behaviour of studied beams, including first crack, ultimate load, deflection, ductility index, strain characteristics, crack pattern and failure mode were investigated. Experimental work results showed that ferrocement beams exhibited higher ductility indices than those of the control normal and lightweight test beams to different degrees. Ferrocement beams made of EFC core generally gave the lowest ductility index while the highest ductility index was found for beams made of AAC and LWC cores. Ferrocement beams demonstrated better crack control and did not undergo spalling as opposed to the conventional beams. Specimens reinforced by EMM showed better ductility than those reinforced by WWM and even after increasing the reinforcement ratio of WWM, the situation did not change. Specimens reinforced by FGM had the lowest ductility compared to specimens reinforced by steel mesh. Cracks were found to develop more rapidly in beams reinforced by EMM, while beams reinforced by FGM exhibited the least amount of cracks. The results of this research showed that ferrocement beams of light weight cores may be promising as an alternative to conventional beams and may be viable alternatives especially for low cost residential buildings.

Lateral torsional buckling of anisotropic laminated thin-walled simply supported beams subjected to mid-span concentrated load

In this paper, a generalized semi-analytical approach for lateral-torsional buckling of simply supported anisotropic, thin-walled, rectangular cross-section beams under concentrated load at mid-span/mid-height was developed using the classical laminated plate theory as a basis for the constitutive equations. A closed form buckling expression was derived in terms of the lateral, torsional and coupling stiffness coefficients of the overall composite. These coefficients were obtained through dimensional reduction by static condensation of the general 6x6 constitutive matrix mapped into an effective 2 × 2 coupled weak axis bending-twisting relationship. The resulting two coupled stability differential equations are manipulated to yield a single governing differential equation in terms of the twisting angle. This differential equation with variable coefficients, subjected to applicable boundary conditions, was solved numerically using Mathematica. The resulting solution was found to correlate with the effective lateral-flexure, torsional and coupling stiffness coefficients to yield a general semi-analytical solution. An analytical formula was possible to extract, which was verified against finite element buckling solutions using ABAQUS for a wide range of lamination orientations showing excellent accuracy. The stability of the beam under different geometric and material parameters, like length/height ratio, layer thickness, and ply orientation, was investigated.

Reduced stiffness of composite beams considering slip and shear deformation of steel

In this paper, a theory is developed for analysis of steel-concrete composite beams with interfacial slip and shear deformation in steel considered. Closed-form solutions are derived for simply supported composite beam under uniform and mid-span concentrated load respectively. Examples are given to compute various quantities of beams. Comparing the results calculated by closed-form solutions with those by ANSYS, good agreements are found. Finally, an explicit formula for the equivalent bending stiffness of the composite beams is found by which the deflections of the composite beams can be calculated as if they were common Bernoulli beams.

Analytical and numerical assessment of the strengthening effect of structural sealant joints for the prediction of the LTB critical moment in laterally restrained glass beams

Glass beams and fins are frequently used in practice as stiffeners for roof and facade panels, and the mechanical interaction between them is often given by continuous silicone sealant joints. As a result, differing from traditional steel–concrete or timber–concrete sections, the so assembled systems behave as coupled laterally restrained (LR) assemblies with intermediate flexible joints, whose LTB structural contributions depend on a combination of multiple aspects. Since for design purposes a proper estimation of the theoretical LTB resistance of LR glass beams is a priority for a first assessment of the expected buckling response, as well as for the development of standardized design methods (e.g. design buckling curves, etc.), in this paper the strengthening effect of structural silicone joints on the LTB response of monolithic glass beams under constant bending moment is first investigated, based on analytical models derived from literature and extended finite element-numerical calculations. The validity and accuracy of existing closed-form solutions is verified for a wide set of geometrical and mechanical configurations of practical interest for structural glass applications. The effects of combined joint shear stiffnesses, beam slenderness and aspect ratios, load distributions and point of applications are emphasized both in terms of critical buckling moments and corresponding fundamental modal shapes. Correction coefficients are then also properly calibrated and proposed for a suitable calculation of the Euler’s critical buckling resistance of fork end restrained LR glass beams with shear flexible sealant joints and subjected to distributed loads or mid-span concentrated loads applied at both the top or bottom edges.

Interfacial Slip Calculation of RC Beams Strengthened with FRP Plate under Mid-Span Concentrated Loads

The collaborative work between fiber reinforced polymer (FRP) and concrete is achieved through the binder, so the interface of them is the weak links. The interfacial slip between FRP and concrete beam is one of the key factors to affect the behaviors of RC beams strengthened with FRP plate. According to elasticity theory, this study analyzes the theoretical analysis of interfacial slip of RC beams strengthened with FRP plate under mid-span concentrated loads. The analytical model is established, and the differential equation of interfacial slip of RC beams strengthened with FRP plate is established. Using the boundary conditions, the calculated formula of interfacial slip is deduced under mid-span concentrated loads.

Flexural strength of hollow tubular flange plate girders with slender stiffened webs under mid-span concentrated loads

A three-dimensional elastic finite element (FE) model, considering merely the geometric nonlinearity, is used in the first part of this paper to study the overall buckling resistance of hollow tubular flange plate girders (HTFPGs). Modeling is conducted using the general-purpose FE software package ABAQUS under mid-span concentrated loads. The developed model consists of the type and number of elements that allows capturing the different possible buckling mode patterns including local, interactive and lateral-torsional buckling. Finite element results revealed that, unlike the case of conventional beams with solid webs, the moment-gradient factor Cb is significantly influenced by the girder geometry and slenderness. Hence, an equation representing the Cb factor for the case of HTFPGs with slender stiffened webs is proposed. The paper extends to investigate the nonlinear flexural strengths of such girders. The results are compared to the AISC predictions. The original AISC predictions are found to be highly conservative using the code recommended Cb value as well as the current proposed value. However, the suggested AISC strength (found in Hassanein et al., 2013 [1]) using Cb=1.35 is found to be the best among other values but it suffers from the discontinuity in the flexural strength-unbraced length relationship. Accordingly, a line representing the middle part of this relationship is currently assumed. Comparisons with FE results indicate that the currently proposed AISC method can fairly predict the flexural strength of the HTFPGs with slender stiffened webs.