Journal of Constructional Steel Research

Published by Elsevier
Print ISSN: 0143-974X
The results of recently completed shear tests indicate that the current connection provisions set out in the AS/NZS 4600, AISI and Eurocode cold formed steel design standards cannot be used to accurately predict the failure mode of bolted connections that are fabricated from thin G550 and G300 sheet steels. Furthermore, these design standards cannot be used to accurately determine the bearing resistance of bolted specimens based on a failure criterion for predicted loads. The measured variation in bearing resistance between thin 0.42 mm G550 sheet steels and typical 1.0 mm and thicker sheet steels has been used to develop a gradated bearing coefficient method, which is dependent on the thickness of the connected materials and the size of the bolt(s) used in the connection. It is recommended that the gradated bearing coefficient formulation, the unreduced net section resistance, and the Eurocode design method for end pull-out be used in the design of bolted connections.
Part 1.2 of Eurocode 4 deals with the fire resistance of composite structures. A simple calculation method is given for assessing the fire resistance of composite beams. This paper explains the state of progress of this calculation method (in 1993) and covers both the heat transfer and mechanical response.
The paper describes the test results of an ongoing major European research project which is concerned with the further development and refinement of structural design guidance for stainless steel. The paper concentrates on the work carried out to date on the design of beams, columns and beam–columns and compares the test results with resistances predicted by the design pre-standard for structural stainless steel, ENV 1993-1-4. In general, the design guidance is conservative. The tests on CHS beams indicate that the limiting diameter-to-thickness ratios for section classification can be considerably increased. For welded I-section beams, the ENV 1993-1-4 lateral torsional buckling curve appears very conservative and the less conservative curve adopted in ENV 1993-1-1 for carbon steel appears to give a better fit to the data.
The paper presents an experimental investigation on 1.83 m wide, 2.44 m high cold-formed steel (CFS) stud framed shear walls using steel sheet sheathing. Four wall configurations were studied through monotonic and cyclic tests. The test results indicated that besides the sheet buckling and screw pull out, the buckling of interior studs might occur for the 1.83 m CFS walls. To prevent the failure in the studs, special detailing was developed in this research. It was discovered that the special detailing could increase both the shear strength and the ductility of the shear walls. The research also found that the codified nominal shear strengths can be conservatively used for walls with an aspect ratio of 3:2. Based on the test results, the nominal seismic shear strength for 1.83 m wide CFS shear walls was established for design purposes.
The development of an interactive computer program for modeling biaxial bending of encased composite steel-concrete columns and its application to design are presented. Included is a description of an analytical procedure for modeling inelastic behavior based on the fiber element method. Results of fiber element analyses are used to evaluate nominal uni- and biaxial bending strengths of composite columns calculated according to the ACI-318 and AISC-LRFD specifications. Slender column behavior and the effect of residual stresses and built-in forces (resulting from the construction sequence) in the steel sections are included. In addition to providing insight into behavior and assessing current design provisions for composite columns, the implementation of the fiber element method demonstrates the feasibility of using inelastic simulation programs in design.
This study presents an approach for refined parametric three-dimensional (3D) analysis of partially-restrained (PR) bolted steel beam-column connections. The models include the effects of slip by utilizing a general contact scheme. Non-linear 3D continuum elements are used for all parts of the connection and the contact conditions between all the components are explicitly recognized. A method for applying pretension in the bolts is introduced and verified. The effect of several geometrical and material parameters on the overall moment–rotation response of two connection configurations subject to static loading is studied. Models with parameters drawn from a previous experimental study of top and bottom seat angle connections are generated in order to compare the analyses with test results, with good prediction shown by the 3D refined models. The proposed 3D modeling approach is general and can be applied for accurate modeling of a wide range of other types of PR connections. A pronounced effect of slip and friction, between the connection components is shown with connections having thicker (stiffer) seat angles. This study demonstrates the effects of clamping through the bolts and contact between the components on the overall non-linear moment–rotation response. Equivalent moment–rotation responses of pull-test simulations are compared to FE model responses of full connections without web angles. The moment–rotation from the pull test is shown to be equivalent to that of the full FE model for small rotations. As the rotation increases a softer response is shown by the pull tests.
This paper reviews the histories of the development and use of high strength and high performance steels for bridge structures in Japan.
Full component tests on high-strength Grade 8·8 bolts in tension and double shear at temperatures up to 800°C have shown the present UK guidelines for designing at the Fire Limit State, BS5950: Part 8, are, for the most part, conservative. New guidelines are proposed.The tests in tension, in combination with Grade 8·8 nuts, have highlighted the possible premature failure due to thread stripping. This mechanism was found to be controlled by the degree of fit between the two components. Practical measures are suggested to enable the full capacity of the bolts to be utilised.Conventional hot tensile tests were carried out using machined specimens from bolts produced by different manufacturing processes. These were found to exhibit similar values of 0·2% proof stress over the temperature region where the normal design stresses coincide with the onset of plastic deformation. The data are also compared with those given for structural steel in the draft Eurocodes.For post-fire evaluation, the influence of the temperatures attained on the residual hardness of high-strength bolts has highlighted the sensitivity of their mechanical properties to overheating. Use has been made of the metallurgical changes to develop a technique for identifying the maximum temperature bolts may have achieved in a fire. This information can assist in the investigation of fire-damaged buildings.
A new type of Reduced Beam Section (RBS) connection, “Accordion Web RBS (AW-RBS)”, is presented in this research. RBS connections are commonly known as connections with reduced flange width within a limited area near the column face. However, the AW-RBS decreases the web contribution in moment strength and a reduced section is developed in the beam. In an AW-RBS, the flat web is replaced by corrugated plates (L-shape folded plates, used here) at the expected location of the beam’s plastic hinge. While the corrugated web has adequate shear strength, its provided moment strength and flexural stiffness are negligible. Two relatively identical specimens including AW-RBS connections have been tested under cyclic loading. Both specimens provide at least 8% story drift, without any significant strength loss, which is more than current requirements for qualifying connections in special moment frames. The accordion effect of the corrugated web and the cyclic performance of the connection are verified by analytical results. According to the analytical and experimental results, the inelastic rotations of the connection are mostly provided by reliable and ductile rotation at the reduced region rather than in the connection plates or panel zone.
In this paper, a refined plastic-hinge analysis is improved to account for the effect of lateral torsional buckling. This analysis accounts for material and geometric nonlinearities of the structural system and its component members. Moreover, the problem associated with conventional refined plastic-hinge analyses in that no consideration is given to the degradation of the flexural strength caused by the lateral torsional buckling is overcome. Efficient ways of assessing steel frame behavior including gradual yielding associated with residual stresses and flexure, second-order effect, and geometric imperfections are presented. In this study, a model consisting of the unbraced length and cross-section shape is used to account for the lateral torsional buckling. The proposed analysis is verified by the comparison of the plastic-zone and LRFD results. Case studies show that lateral torsional buckling is a very crucial element to be considered in refined plastic hinge analysis. The proposed analysis is shown to be an efficient, reliable tool ready to be implemented into design practice.
During a severe earthquake, most moment-resisting steel framed structures are designed and detailed to resist the earthquake through a combination of strength and damage, where the damage occurs in specific, controlled locations in the beams. Contrary to prior opinion and practice, the Northridge and Kobe earthquakes of the mid 1990s showed that the ability of steel structures to deliver this behaviour is not a given, but is dependant on careful design and detailing, and on how the material behaves under the accumulation of damage.This paper focuses on the latter topic and develops a simple and powerful damage parameter to predict failure in the flange of a beam undergoing inelastic action under any loading history. This can be used to illustrate the influence of different loading regimes and to determine element failure in a finite element model.
The effects of construction procedures on the stresses and deformations in a large radius, horizontally curved, plate girder, bridge were examined along with the accuracy with which grillage models predicted the construction behavior. The examination included a study of the stresses and deformations during construction and a comparison of those quantities to the grillage model predictions. Results from the study indicated that, for the structure that was examined: (1) appreciable warping stresses were generated during girder erection; (2) the classical grillage model predictions were less accurate during girder erection while the “modified” model predictions were more accurate during deck placement; and (3) the predicted grillage model deflections were smaller for an exterior-to-interior girder erection procedure than an interior-to-exterior procedure.
This paper provides a detailed evaluation and comparison of five specific procedures for elastic analysis and stability design of steel frames. The strength predictions of these methods are compared to one another and to the results of rigorous plastic zone solutions. Three of the approaches involve story- or system-buckling calculations using methods detailed in a companion paper. The fourth procedure is based on a simple approximate formula for story-buckling effective length factors. The fifth approach does not utilize column-buckling loads or effective lengths, but rather accounts for the stability behavior through the application of ‘notional’ horizontal loads at each of the floor levels of a building frame. The paper focuses on the fundamental characteristics and accuracy of each of the methods, and on the relative simplicity of their associated calculations. Two case study examples are presented that highlight issues pertinent to redundant framing systems. These frames collectively include many of the behavioral phenomena that can influence the accuracy and simplicity of the design calculations.
The use of the acoustic emission technique to monitor fatigue crack propagation in steel compact tension specimens and T-section girders is described. Based on the correlations between crack propagation rates, acoustic emission count rates and stress intensity factor range procedures are suggested for predicting remaining fatigue life. It is anticipated that the experimental techniques and theoretical procedures developed will eventually be incorporated in a scientifically based methodology for the inspection, monitoring, assessment and repair of fatigue damaged structures.
The monitoring of fatigue crack propagation in steel and welded steel compact tension and T-section girder test specimens, using an advanced acoustic emission system with accurate source location, is described. The compact tension test specimens were subjected to load ratios of 0.1, 0.3, 0.5 and 0.7 while the T-section girders were subjected to a load ratio of 0.3. Located acoustic emission events were filtered for a narrow band containing the fatigue crack, and separated for different regions of the applied load range. The test results indicate that acoustic emission count rates, for small percentages of the applied load range close to the peak load, show reasonable correlation with crack propagation rates. Based on these correlations it may be possible to predict the remaining service life of fatigue damaged structures from the results of short term acoustic emission monitoring.
Many steel buildings suffered from fracturing of beam-to-column connections in the Northridge earthquake and Kobe earthquake. It was also found that most of the connections which failed were due to fracturing at the weld between the bottom flange of the beam and the column flange plate. The stiffness and strength contributed from floor slabs may cause the fracture on the bottom flanges of the connecting beams. In this study, the effect of composite action on the ductility performance of the connections are examined through a series of large size experimental studies of beam-to-column subassemblies which include floor slabs. The beam strength around the connection was reduced according to the seismic strength demand, and it was found that an enlarged plastic zone can be achieved and the deformation capacity can be increased substantially. From experimental studies, it was found that the ratio of positive moment to negative moment strength may be as high as 1.18 which is mainly from the contribution of floor slabs. It was also found that the floor slabs cause the beam sections to become unsymmetrical and induce higher strain on the bottom flanges. Owing to these effects, the fractures of the specimens tested were on the bottom flanges which resembled the failure mode which occurred during the Northridge earthquake.
The need for consistency between representation of joint behaviour and the approach of overall frame analysis and design, as emphasised by EC3, is discussed. A thorough examination of the ability of a simplified technique—currently permitted by EC3, but not previously fully validated—to provide acceptable solutions with significantly reduced computational effort is reported. It is found that the half initial secant stiffness method represents an attractive practical approach.
In recent years important research activity has been undertaken in order to evaluate the earthquake performance of light-gauge steel-framed house structures. Almost all studies approach the problem of seismic response of these structures by characterising, experimentally and numerically, the performance of wall panels. Usually, the overall behavior of wall panels is mainly addressed. However, according to experimental evidences, the performance of the wall panels, as a whole, is governed by the performance of the connectors e.g.: sheeting-to-sheeting connectors, and sheeting-to-framing connectors. On the other hand the global behavior of the 3D structure of the house is significantly influenced by non-structural elements, traditionally not considered in the design procedures. The present paper summarizes the research activity carried out in the last few years at the Politehnica University of Timisoara, under the coordination of the author, with the aim to evaluate the performance and to characterise for design purpose the specific features of these structures. Monotonic and cyclic tests on full-scale shear panels, tests on connection details, and in situ ambiental vibration tests on a house under construction are reviewed and concluded in the following paper.
The results of a series of fatigue tests on four full-scale slender plate-girders with medium to large panel aspect ratios (α=1.5 and 3) subjected to repeated combined action of bending and shear, are presented herein. The plate girders (span: 7.5 m, depth: 1200 mm, web thickness: 5 mm) were tested under constant amplitude fatigue loading up to failure. The main purpose of these laboratory tests was to gain information about the fatigue behaviour, with regard to web breathing, of full-scale specimens subjected to a type of loading similar to that encountered in actual bridge girders. Numerical analyses by means of the finite element method (FEM) were also performed. The results show that parameters such as levels of minimum and maximum load used during fatigue testing, weld quality, shape and magnitude of the initial imperfections, etc., have a large influence on the fatigue performance of slender I-girders subjected to web breathing.
Adhesives are used in very different applications. Up to now, the technique of structural adhesive bonding is not applied to steel constructions. This article shows adhesives to be efficient. The application of adhesives in steel constructions is possible and can be an alternative on its own to common techniques like bolts and welds as well as in combination with bolts.
A technique that may be used to augment most in-plane advanced analysis procedures to account for inelastic out-of-plane flexural–torsional buckling in the design of planar steel frames is presented. The linear stability theory is adopted and the finite element analysis method is used to derive the second-order stiffness matrix. The effects of material nonlinearities and geometric imperfections on out-of-plane buckling strength are accounted for by substituting the elastic rigidities (EIy, ECw and GJ) with their effective values, which are determined from calibrations against specification equations for member strength. Based on a set of attributes found in typical building frames, it is demonstrated that out-of-plane buckling is likely to govern the strength of nonsway frames and may control the strength of sway frames. Thus, the proposed advanced analysis technique is recommended for the design of both types of planar steel frames.
A new design method of three-dimensional truss bridges using practical advanced analysis is presented. Separate member capacity checks encompassed by the code specifications are not required, because the stability of separate members and the structure as a whole can be rigorously treated in determing the maximum strength of the structures. The geometric nonlinearity is considered using the updated Lagrangian formulation. The material nonlinearity is implemented using Column Research Council (CRC) tangent modulus. Result verifications are performed by comparison with the results from a step by step analysis. The load–deflection behavior of the truss shows a good agreement with the step by step analysis results. A case study is performed on a truss bridge. The analysis results show that the proposed method is suitable for adoption in practice.
Modern limit-state design codes are based on limits of structural resistance. To determine the ‘true’ ultimate load-carrying capacity of spatial structures, an advanced analysis method which considers the interaction of actual behaviour of individual members with that of the structure is required. In the present work, a large-displacement inelastic analysis technique has been adopted to compute the maximum strength of spatial structures considering both member and structure instability. The actual behaviour of individual members in a spatial structure is depicted in the form of an inelastic strut model considering member initial imperfections as ‘enlarged’ out-of-straightness. The maximum strength of the strut is computed based on a member with ‘equivalent out-of-straightness’ so as to achieve the specification's strength for an axially loaded column. The results obtained by the strut model are shown to agree well with those determined using plastic-zone analysis. The nonlinear equilibrium equations resulting from geometrical and material nonlinearities are solved using an incremental-iterative numerical scheme based on generalised displacement control method. The effectiveness of the proposed advanced analysis over the conventional analysis/design approach is demonstrated by application to several space truss problems. The design implications associated with the use of the advanced analysis are discussed.
This paper provides a state-of-the-art summary of recent advances in inelastic analysis of space frame structures. Particular attentions are devoted to inelastic modelling of framework components for accurate representation of frame behaviour and the applications of plastic hinge analysis for large-scale framework. Issues related to inelastic buckling and post-buckling unloading of struts, modelling of gradual yielding in steel beam-columns, inelastic modelling of composite floor beams subject to sagging and hogging moments, modelling of building core walls and semi-rigid beam-to-column connections in three-dimensional frameworks are discussed. Numerical examples are provided to illustrate the acceptability of the use of the inelastic models in predicting the ultimate strength and inelastic behaviour of spatial frameworks.
The lateral postbuckling response of thin-walled structures such as bars and frames with members having steel rolled shapes as well as circular cylindrical shells under axial compression is thoroughly reconsidered. More specifically via a simple and very efficient technique it is found that beams with rolled shapes (symmetric or non symmetric) under uniform bending and axial compression exhibit a stable lateral–torsional secondary path with limited margins of postbuckling strength. New findings for the static and dynamic stability of frames with crooked steel members–due to the presence of residual stresses–are also reported. It is comprehensively established that the coupling effect due to initial crookedness and loading eccentricity may have a beneficial effect on the load-carrying capacity of the frames. Moreover, simple mechanical models are proposed for simulating the buckling mechanism of axially compressed circular cylindrical shells. Very recently Bodner and Rubin proposed an 1-DOF mechanical model whose buckling parameters correlated to those of the shells by using an empirical formula based on experimentally observed shell buckling loads. In the present analysis a new 2-DOF model for the static and dynamic buckling of axially compressed circular cylindrical shells, which can include mode coupling, is presented.
Recent developments in the practical utilisation of cold-formed sections in building construction have taken place on three related fronts. There have been significant developments in the technology which result in more complex shapes with a higher yield stress so that cold-formed sections represent a particularly high-tech form of constructional steelwork. Developments in technology would be of little consequence unless there were parallel developments in practical applications and this is illustrated by the continual increase in the market share of cold-formed sections. This, in turn, makes demands on design procedures and requires parallel development in calculation models and design codes. In particular, sections have tended to become more highly stiffened and this necessitates a more sophisticated treatment of local buckling, distortional buckling and the interactions between them. The latest trend is to move from simplified design models to design procedures based on “whole section” analysis. In this paper, recent developments in technology and application are outlined and this is followed by more detailed consideration of the related design procedures.
Using evidence from research over varying periods of time from four separate subject areas, the interplay between theory and experiment is examined. Real gains in understanding of the sort necessary to underpin improvements to design methods that combine the benefits of economic gains (as measured by savings in both material and design effort) with greater affinity to the true situation, are shown to depend on this. It is recognised that ‘theory’ may well embrace numerical work and that, providing work is well done and, equally importantly, well reported, both parts need not necessarily be the responsibility of the same team.
Basic aerodynamic principles underlying the response to wind of cable-supported bridges are outlined. Their links to aeronautical methodology as well as their important differences of detail are mentioned. The problems treated are the basic oscillatory stability under wind and the response to turbulence. The treatment, originating in the time domain, is transformed to the frequency domain; the response is then calculated by power spectral methods. In particular, the interrelated roles of indicial aerodynamic response functions, flutter derivatives and aerodynamic admittances are reviewed. The theory outlined is representative of methodology currently applied in the design studies of numerous long-span cable-supported bridges.
The suspen-dome system is a new structural form that has become popular in the construction of long-span roof structures. These domes are very slender and lightweight, their configuration is complicated, and hence sequential consideration in the structural design is needed. This paper focuses on these considerations, which include the method for designing cable prestress force, a simplified analysis method, and the estimation of buckling capacity. Buckling is one of the most important problems for dome structures. This paper presents the findings of an intensive buckling study of the Lamella suspen-dome system that takes geometric imperfection, asymmetric loading, rise-to-span ratio, and connection rigidity into consideration. Finally, suggested design and construction guidelines are given in the conclusion of this paper.
This paper describes a series of tests on steel tubular columns of circular and square section filled with normal concrete and recycled aggregate concrete. Thirty specimens, including 24 recycled aggregate concrete filled steel tubular (RACFST) columns and 6 normal concrete filled steel tubular (CFST) columns, were tested to investigate the influence of variations in the tube shape, circular or square, concrete type, normal concrete and recycled aggregate concrete, and load eccentricity ratio, from 0 to 0.53 on the performance of such composite columns. The test results show that both types of filled columns failed due to overall buckling. Comparisons are made with predicted ultimate strengths of RACFST columns using the existing codes, such as ACI 318-1999, AIJ-1997, AISC-LRFD-1999, BS5400-1979, DBJ13-51-2003 and EC4-1994. A theoretical model for normal CFST columns is adopted in this paper for RACFST columns. The predicted load versus deformation relationships are in good agreement with test results.
Grillage systems are widely used in structures to cover large areas in bridge decks, ship hulls and floors. In this paper, the charged system search (CSS) algorithm is utilized to obtain the optimum design of grillage systems. This algorithm is inspired by the Coulomb and Gauss laws of electrostatics in physics and the governing laws of motion from Newtonian mechanics. The cross-sectional properties of beams are considered as the design variables. Comparison of the results with those of some previous studies shows the robustness of the new algorithm.
The paper describes a column curve formulation capable of producing accurate strength curves for cold-formed stainless steel columns. The formulation uses a non-linear expression for the imperfection parameter but is otherwise identical to the Perry–Robertson equation used in Eurocode3, Parts 1.1, 1.3 and 1.4. It is shown that several column curves are necessary for accurately describing the strength of austenitic and austenitic–ferritic stainless steel alloy columns and two curves are proposed. One of these is close to the curve for cold-formed sections currently used in the draft Eurocode3, Part 1.4. A new column curve is also proposed for ferritic alloys and 12% chromium weldable structural steels.
In this paper a direct displacement-based design (DDBD) method for seismic design of steel frames equipped with dissipative braces is proposed. Attention is focused on concentric braced steel frames with pinned beam-to-column joints in which the bracing system (with viscoelastic or elastoplastic dissipative devices) is the main seismic resistant component. The proposed design method uses an equivalent continuous model where flexural deformability and shear deformability are related respectively to columns and diagonals of the bracing system. In this way, analytical expressions of the required flexural and shear stiffness distributions are obtained. These expressions are quite simple and can be conveniently used in preliminary design of dissipative diagonal braces and columns. Examples are shown for steel frames with dissipative braces based on elastomeric dampers (viscoelastic devices) and steel frames with buckling-restrained braces (elastoplastic devices). Results of time history analyses are illustrated and discussed in order to evaluate the effectiveness of the proposed DDBD procedure.
The behaviour of composite beams under hogging bending has been successfully simulated using an analytical model derived previously. This paper describes the extension of the work to study the behaviour of composite joints incorporating semi-rigid flush end plate connections. With proper inclusion of the joint characteristics, the model was found to be equally capable of modelling the structural behaviour including the effects of partial shear connection. Experimental results of a novel series of composite joint tests detailed in the accompanying companion paper were compared, in addition to those published in the literature. The analysis results provided close agreement with the various test behaviour. Using the model that has been properly calibrated against experimental results, a systematic parametric study was also undertaken. The outcomes are described herein. In addition, existing design models to predict the strength, stiffness, and ductility of composite joints were also reviewed and compared against the test results. The results emanating from this paper contribute as a total package apart from experimental undertakings to further understand the complex behaviour of the composite joints. This is very beneficial in a design perspective.
At ambient temperature, researchers [Comput. Struct. 2 (1972) 253; AISC Engng J. (1984) 161; J. Construct. Steel Res. 45 (1998) 1] have focused on producing simplified models in order to predict the ultimate capacity of a column web subjected to transverse compressive forces and thereby assist engineers to design steel joints efficiently. Another reason for producing these models was to eliminate the use of column web stiffeners, which are expensive to install and interfere with the weak-axis framing of beams into the column. The resistance to concentrated forces is a very complex problem in which it is almost impossible to derive closed theoretical solutions. Therefore, studies aiming at predicting the ultimate resistance of column webs to concentrated forces tend towards empirical solutions. The problem becomes more complicated when another variable, such as temperature, is introduced. This paper reports how existing empirical models at ambient temperature, contained in design codes and standards, may be modified for application at elevated temperatures.
Many complicated analytical methods have been proposed to predict the effects of the geometric nonlinearity of a single-story multi-bay steel frame and the material nonlinearity of its steel members. However, some structural engineers have difficulty in understanding the complicated methods and applying them in designing steel structures. Therefore, this study has been performed to provide a simplified analytical model that is only applicable in the preliminary design stage. Using the simplified analytical model, structural engineers can easily predict the storey drift, maximum allowable loads, and bracing stiffness of a single-storey multi-bay steel frame. The application feasibility of the simplified model is verified by performing a two-dimensional finite element analysis.
The experimental results of composite beam-to-column joints subject to reversal of moments have been reported in the companion paper [J. Construct. Steel Res. 2003 Doi: 10.1016/j.jcsr.2003.08.010]. This paper presents the analytical assessment of moment capacity and initial rotational stiffness of the beam-to-column joints. The predicted results are compared with those obtained from the tests. The component method extracts from Eurocodes 3 and 4 and its companion document was used to determine the negative moment capacity and initial rotational stiffness. Based on the same principles, the method was extended to calculate the properties of joints subjected to positive moment. Comparison of results shows reasonable correlation except, however, the Eurocode method is found to overestimate the rotational stiffness of joint specimens subjected to negative moment.
Fatigue in steel structures subjected to stochastic loading is studied. Of special interest is the problem of fatigue damage accumulation and in this connection, a comparison between experimental results and results obtained using fracture mechanics. Fatigue test results obtained for welded plate test specimens are compared with fatigue life predictions using a fracture mechanics approach. In the calculation of the fatigue life, the influence of the welding residual stresses and crack closure on the fatigue crack growth is considered. A description of the crack closure model for analytical determination of the fatigue life is included. Furthermore, the results obtained in studies of the various parameters that have an influence on the fatigue life, are given. A very good agreement between experimental and analytical results is obtained, when the crack closure model is used in determination of the analytical fatigue lives. Both the analytical and experimental results obtained show that the Miner rule may give quite unconservative predictions of the fatigue life for the types of stochastic loading studied.
The observations and results from an experimental investigation of the seismic resistance of partially encased beam-columns given in the companion paper are used to assemble and verify analytical models incorporating the salient behavioural features of the test specimens. The analytical models, which employ either the commonly used bilinear kinematic hardening constitutive relationship for structural steel or the more advanced multi-surface plasticity model, are shown to achieve good agreement with the experimental results, while remaining sufficiently economical for application to larger structures. The relative performances of both material models are compared, the seismic resistance of partially encased beam-columns as identified by the experimental investigations is evaluated and the implications of the use of such structural elements in the earthquake-resistant design of multi-storey structures is discussed.
Steel scaffolds collapse quite often in many places with a considerable number of reported casualties, but their behaviour has not been studied to the extent of many other permanent structures. This paper investigates the effect of eccentric loads on steel scaffolding systems used in construction sites. The type of scaffold considered here is the door-shaped steel scaffold with an inner reinforced gable sub-frame. The single-side cross-brace scaffolding systems with various eccentric loads are mainly focused on two issues, namely, the unrestrained boundary and the removal of cross-braces at the access location. This study shows that regardless of the lowest layer of cross-brace in a scaffold being removed or not, the critical load of a scaffolding system under an eccentric load is the lowest, whereas that of scaffolding system under a concentric load is the maximum. If the bottom jack base of a scaffolding system in construction sites is strengthened to a fixed end, the critical load of this scaffolding system will be greatly increased. If a scaffolding system is erected more than 8 stories high, the critical load of the scaffolding system with the fixed end base can be increased to 2.4 times that with the hinged base. However, whether the cross-braces at the lowest story of a scaffolding system are removed or not, the simulated scaffolding test indicates that the critical load of a used scaffolding system under the eccentric load is the lowest and its load reduction also appears significant.
This paper presents the results of further development of a new analytical approach for the evaluation of shear strength and cracking patterns of infill panels. This method is based on the minimum evaluated strength with reference to the failure surfaces. This paper also presents the results of an experimental investigation of small and medium scale masonry and concrete infilled frames. Eleven specimens, with and without horizontal reinforcement and bond beams, were subjected to static cyclic loads. The tests are categorized in two groups, based on their surrounding frames and scale. In the first group a small scale factor is used, and the frames have pinned connections with very stiff beams and columns representing the lower stories of tall buildings. In the second group a medium scale factor is used, and the frames have rigid connections.Both experiments and analysis have confirmed that the efficiency of horizontal reinforcement and bond beams depends on the dominant pattern of cracking. The results also indicate that as opposed to masonry infills, the corner crushing is the dominant mode of failure in concrete infills.
We investigate dynamic buckling of aboveground steel tanks with conical roofs and anchored to the foundation, subjected to horizontal components of real earthquake records. The study attempts to estimate the critical horizontal peak ground acceleration (Critical PGA), which induces elastic buckling at the top of the cylindrical shell, for the impulsive hydrodynamic response of the tank–liquid system. Finite elements models of three cone roof tanks with height to diameter ratios (H/D) of 0.40, 0.63 and 0.95 and with a liquid level of 90% of the height of the cylinder were used in this study. The tank models were subjected to accelerograms recorded during the 1986 El Salvador and 1966 Parkfield earthquakes, and dynamic buckling computations (including material and geometric non-linearity) were carried out using the finite element package ABAQUS. For the El Salvador accelerogram, the critical PGA for buckling at the top of the cylindrical shell decreased with the H/D ratio of the tank, while similar critical PGAs regardless of the H/D ratio were obtained for the tanks subjected to the Parkfield accelerogram. The elastic buckling at the top occurred as a critical state for the medium height and tallest models regardless of the accelerogram considered, because plasticity was reached for a PGA larger than the critical PGA. For the shortest model (H/D=0.40), depending on the accelerogram considered, plasticity was reached at the shell before buckling at the top of the shell.
The formula in the 2005 American Institute of Steel Construction Specification to compute the strength of headed steel stud anchors (shear connectors) in composite steel/concrete structures has been used in the United States since 1993, after being proposed based primarily on the results of push-out tests. In the past several decades, the range of members used in composite structures has increased significantly, as has the number of tests in the literature on the monotonic and cyclic behavior of headed studs in composite construction. This paper reviews 391 monotonic and cyclic tests from the literature on experiments of headed stud anchors and proposes formulas for the limit states of steel failure and concrete failure of headed stud anchors subjected to shear force without the use of a metal deck. Detailing provisions to prevent premature pryout failure are also discussed. This paper also reviews proposals from several authors and provides recommended shear strength values for the seismic behavior of headed studs. The limit state formulas are proposed within the context of the 2005 AISC Specification, and comparisons are made to the provisions in the ACI 318-08 Building Code, the PCI Handbook, 6th Edition, and Eurocode 4. The scope of this research includes composite beam–columns [typically concrete-encased steel shapes (SRCs) or concrete-filled steel tubes (CFTs)], concrete-encased and concrete-filled beams, boundary elements of composite wall systems, composite connections, composite column base conditions, and related forms of composite construction.
Results of tests on 13 double-angle beams bending about the geometric axis are presented. Nine regular size and two ultra-large size angles were included in the investigation. The test failure moments were 2–32% greater than the plastic moments of resistance and 55–95% greater than the nominal flexural strengths calculated as per the American Institute of Steel Construction ‘Specification for Load and Resistance Factor Design of Single-angle Members’ issued in 1993. For the angles tested, the deflections at 1.5 times the yield moment were only 1.53–1.74 times the deflections at first yield. Failure strains in compression exceeded the yield strain even for a specimen with a width-to-thickness ratio of 19.0. It is concluded that the nominal resistances for angle members bending about the geometric axis computed using the current AISC-LRFD Specification for Single Angles are highly conservative and there is need to revise the pertinent clauses in the specification in the interest of design economy.
The ends of a coped beam are commonly connected to the web of a girder by double clip angles. The clip angles may either be bolted or welded to the web of the beam. One of the potential modes for the failure of the clip angle connection is the block shear of the beam web material. To investigate the strength and the behavior of the block shear of coped beams with welded end connections, ten full-scale coped beam tests were conducted. The test parameters included the aspect ratio of the clip angles, the web shear and tension area around the clip angles, the web thickness, beam section depth, cope length, and connection position. The test results indicated that the specimens failed, developing either tension fractures of the web near the bottom of the clip angles or local web buckling near the end of the cope. Although the final failure mode of the six specimens was local web buckling, it was observed during the tests that these specimens exhibited a significant deformation of the block shear type prior to reaching their final failure mode. No shear fracture was observed in all of the tests. A comparison between the ultimate loads in the test and the predictions using the current design equations indicates that the current design standards such as the AISC-LRFD, CSA-S16-01, Eurocode 3, BS5950-1:2000, AIJ and GB50017, are inconsistent in predicting the block shear strength of coped beams with welded end connections. The analytical study of the strength of the test specimens using the finite element method, a parametric study, and a proposed design model for designing block shears for coped beams with welded clip angles are included in a companion paper.
This paper investigates the influences that non-homogeneous material properties and residual stress distributions have on the structural ductility of single angle beams bent about the minor principal axis. Such non-homogeneity in material response, and initial stress distribution results from manufacturing processes and varies substantially on a case-by-case basis. The investigation reported herein is based on experimentally verified nonlinear finite element modeling techniques. Mild carbon steel single angles with three distinct material property stratification scenarios are studied within the context of minor principal axis flexure. These cases are also examined both with and without the presence of residual stresses. Both plastic hinge rotation capacity and severity of unloading within the moment–rotation response are studied; in this way it is possible to quantify the structural ductility of single angle beams. In addition, differing definitions for plastic section properties are examined to ascertain their impact on the values of the above ductility response measures.
The present study employs experimentally verified nonlinear finite element analysis techniques to study the ultimate response of single angle beams bent about the major principal axis. The results of the finite element studies show that the current American steel specification predicts nominal moment capacities well below those achieved in the numerical tests. Similarly, the American code does not allow for the design of single angle beams using plastic analysis and design techniques. The work reported herein demonstrates that single angles bent about the major principal axis are indeed suitable for proportioning by plastic design methodologies. Minimum cross-sectional compactness values are given, as is a design equation relating single angle plate slenderness, beam slenderness, yield stress, and rotation capacity. Imperfection sensitivity is also studied through the use of an out-of-plane load, of varying magnitude, imposed at the single angle mid-span shear center. The results show that single angle beams, bent about the major principal axis, enjoy a high degree of imperfection insensitivity.
This paper presents a study of the shear lag effects on the behaviour and strength of welded steel single angle tension members. A total of thirteen single angles with welded end connections were tested in tension. The test parameters included long and short leg connections, balanced and unbalanced weld arrangements and longitudinal fillet weld lengths. Out of the thirteen specimens, nine failed by fracture of the gross section and four failed in the welds. The efficiency of the specimens, which is defined as the ratio of the test ultimate load () to the tensile capacity (a product of the gross sectional area and the tensile strength of the material) of the specimens varied from 0.82 to 1.02. It can be observed from the test results that both the ultimate loads sustained by the short leg connected angles and the ductility of all the angle specimens were greater when the balanced weld arrangement was used in the connections than when the specimens were connected using the unbalanced welded arrangement. Finite element analyses of the specimens were conducted and the analysis results compared well with the test results. The capacities of the test specimens were also evaluated using various design approaches. In general the design specifications (AISC-LRFD, BS5950-1:2000, and CSA-S16-01) provided good predictions of the tensile capacity of the single angle specimens with a reasonable degree of conservatism. However, the design specifications underestimated the tensile capacity of specimens which were connected by the short leg and with a balanced weld arrangement.
Current design specifications do not address issues of compactness and bracing requirements for use in the plastic analysis and design of single angle flexural members. The research described herein employs experimentally verified nonlinear finite element analysis techniques, implemented on super-computer hardware platforms, for the development of equal leg single angle compactness and bracing requirements. Four common flexural orientations are investigated. Geometric and material nonlinearities are considered in the models, as are the effects of residual stresses.
Top-cited authors
Lin-Hai Han
  • Tsinghua University
Leroy Gardner
  • Imperial College London
Brian Uy
  • UNSW Sydney
Professor Zhong Tao
  • Western Sydney University
D.A. Nethercot
  • Imperial College London