Standardisation of partial strength connections of extended end-plate connections for trapezoid web profiled steel sections

Traditionally, connections are usually classified as pinned or rigid although the actual behaviour is known to fall between these two extreme cases. The use of partial strength or semi-rigid connections has been encouraged by codes and studies on the matter known as semi-continuous construction have proven that substantial savings in steel weight of the overall construction. The objective of this paper is to develop a series of standardised partial strength connections tables of extended end-plate connections for trapezoidal web profiled steel (TWP) sections. The range of standard connections presented in tabulated form is limited to eight tables comprised of different geometrical aspects of the connections. These tables could enhance the design of semi-continuous construction of multi-storey braced steel frames. The connections are presented in the form of standardised tables which include moment capacity and shear capacity after considering all possible failure modes. A method proposed by Steel Construction Institute (SCI) which take into account the requirements in Eurocode 3 and BS 5950:2000 Part 1 were adopted to predict the moment capacity and shear capacity in developing the tables. A series of tests have been carried out to validate the results of the standardised tables. The test results showed good agreement between theoretical and experimental values. It can be concluded that the proposed standardised tables for TWP sections is suitable to be used in the design of semi-continuous construction

Stainless steel plate girders subjected to shear buckling at normal and elevated temperatures

The final publication is available at Springer via http://dx.doi.org/10.1007/s10694-016-0602-6Numerical simulations have been widely applied, for the determination of the resistance of steel structural elements, when experimental analysis are not possible (due to cost or size limitations) or when parametric studies with high number of variables are needed. However, the numerical models must be properly validated with experimental tests in order to deliver reliable studies. With the purpose of studying the behaviour of stainless steel plate girders in fire situation, a total of 34 experimental tests from the literature have been numerically modelled. The tested girders had different configurations: rigid and non-rigid end posts, 2 and 4 panels, and transversal and longitudinal stiffeners were considered. Comparative analyses between those experimental and numerical results have been done. Good approximations to the experimental results at normal temperatures have been achieved with differences on average lower than 5%. Afterwards, the developed numerical model has been used to perform a sensitivity analysis on the influence of the initial geometric imperfections at both normal and elevated temperatures, considering different values for its maximum amplitudes, concluding that 10% of the web thickness is an appropriate value for the maximum amplitude of the geometric imperfections when modelling experimental tests. The effect of the residual stresses has also been analysed, being obtained differences lower than 2%. Finally, comparisons between the numerical results and the Eurocode 3 design procedures have been performed considering different uniform elevated temperatures.Peer ReviewedPostprint (author's final draft

Design and Behavior of Steel Delta Girders

In steel structures, I-sections are commonly used for beams and columns. These cross-sections usually lack lateral rigidity and torsional stiffness. An effective method to improve their lateral rigidity and overall flexural resistance is to weld two inclined rectangular plates to the compression flange and the compression portion of the web of hot-rolled or welded I-section to form what is known as a Delta girder. This mixed cross-section, i.e., cross-section composed of an open profile attached to a closed profile, can provide enhanced torsional stiffness and hence noticeably higher lateral-torsional buckling (LTB) capacity for the beam. While Delta girders can be used for any beams, their main applications are the design of crane runway and bridge beams and strengthening of existing beams. The main objectives of this dissertation are to study the static behavior of these girders and to provide a set of design equations for their nominal flexural and shear capacities. The research includes deriving closed-form equations for the cross-section properties of Delta girders. These equations are then verified against solutions obtained numerically. Using these cross-section properties, the theoretical lateral-torsional buckling capacity of Delta girders are determined and compared against results obtained from a finite element (FE) analysis. The results show that the theoretical LTB equation derived for general monosymmetric sections can be applied to these Delta girders. Additionally, it is shown that a simplified expression for the coefficient of monosymmetry βx derived for I-sections can be used in the computation of the elastic LTB capacity of Delta girders. A parametric study is then performed based on elastic LTB capacity to demonstrate the effectiveness of Delta girders in achieving a favorable capacity-to-weight ratio when compared to standard I-section members. A refined three-dimensional (3D) nonlinear inelastic FE models are then developed to examine the capacity of simply-supported Delta girders under uniform bending and pure shear. The models take into considerations the effects of initial geometrical imperfections and residual stresses on the behavior of Delta girders. The FE model and the modeling techniques used are verified against the experimental result of a test beam that failed by inelastic LTB. The analysis covers a comprehensive range of Delta girder dimensions based on the dimensions of standard hot-rolled European H- and I-sections. A sensitivity study on the effects of using reduced imperfections magnitudes shows up to 18.2% increase in the LTB capacity of the girder. Based on the FE LTB simulation results, it is shown that the buckling curve in the AISC (2016a) specifications overestimates the buckling capacity of Delta girders by an average of 9% and a maximum value of 21%. On the other hand, buckling curves “a” and “b” for rolled sections or equivalent welded sections case in the EuroCode 3 (2005) for Delta girders with d⁄bc ≤2 and d⁄bc \u3e2, respectively, provide an average difference of only 2% and a maximum difference of 7% in comparison to the FE results. Hence, these two curves are recommended for the LTB design of Class 1 (compact) Delta girders. Additionally, design recommendations are provided for selecting the proper delta stiffeners dimensions based on the cross-section geometries of the corresponding I-sections. Shear capacity equations for Class 1 (compact) Delta girders are proposed based on FE simulation results. The equations provide the option of selecting a conservative value that ignores strain hardening in the cross-section or a value that allows for some strain hardening to occur. In comparison to I-sections, the Delta girders analyzed in this study show an increase in shear capacity in the range of 41% to 89%. Furthermore, it is shown that in contrast to I-sections, yielding is a gradual process in Delta girders due to the presence of a non-uniform elastic shear stress distribution in the cross-section

Decision Table Formulation of The 1969 Aisc Specification

The American Institute of Steel Constructio

Experimental investigation of retrofitting techniques for steel bridge girders subject to fatigue failure

Fatigue failure is major concern for infrastructure due to the increasing number of steel structures reaching the end of their design life each year. Increased loadings, deterioration due to weathering, climate change and human error also negatively impact the design life. Rehabilitating steel bridge girders rather than replacing the existing structure can provide an option for an economical and sustainable future. This paper presents the results of an experimental study which implements a simple retrofitting technique to combat fatigue failure. The retrofitting technique is applied to girders which have incurred fatigue cracking within the bottom flange. Experimental tests are performed on a riveted tapered 120-year-old girder and a new prefabricated hot rolled girder. The results from the experimental tests showed that fatigue cracking within the bottom flange of girders can be easily rehabilitated to increase the girder’s capacity to that of their original design. By utilising this simple designed retrofitting technique, existing structures do not need to be replaced. The technique shown herein is a viable method for increasing the service life of steel girders providing for a sustainable future

Finite Element Analysis and Lightweight Optimization Design on Main Frame Structure of Large Electrostatic Precipitator

The geometric modeling and finite element modeling of the whole structure of an electrostatic precipitator and its main components consisting of top beam, column, bottom beam, and bracket were finished. The strength calculation was completed. As a result, the design of the whole structure of the electrostatic precipitator and the main components were reasonable, the structure was in a balance state, its working condition was safe and reliable, its stress variation was even, and the stress distribution was regular. The maximum von Mises stress of the whole structure is 20.14 MPa. The safety factor was large, resulting in a waste of material. An optimization mathematical model is established. Using the ANSYS first-order method, the dimension parameters of the main frame structure of the electrostatic precipitator were optimized. After optimization, more reasonable structural design parameters were obtained. The model weight is 72,344.11 kg, the optimal weight is 49,239.35 kg, and the revised weight is 53,645.68 kg. Compared with the model weight, the optimal weight decreased by 23,104.76 kg and the objective function decreased by 31.94%, while the revised weight decreased by 18,698.43 kg and the objective function decreased by 25.84%

Towards the Development of Efficient and Economical Short Span Modular Bridges

The Federal Highway Administration\u27s National Bridge Index consists of over 600,000 bridges. Of these bridges, over 25% are considered either structurally deficient or functionally obsolete. While several state bridge departments have standard designs for bridge components in order to speed up the design process in replacing these bridges, few have standard designs for the bridge superstructure.;This work investigates current practices and trends in the design of short span bridges through the use of a survey. The survey was presented to the bridge department of every state in the country and responses were collected from 86% of these states. Based on the responses to these surveys, two courses were pursued in this work: the research and grading of both existing and developing modular bridge technologies that have application in short span steel bridges and the development of standard short span steel bridge superstructures using conventional design approaches.;In collaboration with the American Iron and Steel Institute\u27s Short Span Steel Bridge Alliance and other professionals in the bridge industry, a collection of modular bridge systems and elements were compiled and researched. Based on the Federal Highway Administration\u27s Highways for LIFE initiative, which promotes the development of Long-lasting highway infrastructure using Innovations to accomplish Fast construction of Efficient and safe highways and bridges, a grading system was developed for professionals in the industry to grade the major modular bridge systems researched. Based on the grading of these systems, a system will be further developed into a set of standardized short span bridge designs.;Second, standard short span steel bridge designs were developed to create a design aid for bridge engineers. In these designs, bridges with spans ranging from 40 feet to 140 feet in 5 foot increments were developed for rolled steel sections, homogeneous steel plate girder sections and hybrid steel plate girder sections. The rolled sections were designed using two design approaches: the lightest weight possible and the lightest weight possible with a limited section depth. Based on these designs, a suite of rolled sections were selected to be efficient sections of larger span ranges. This limited suite provides the opportunity for stock piling common rolled steel girder sections. Without needing to order the fabrication of the rolled girder sections, a more efficient transition from design to construction can be achieved. The plate girder sections were designed with a limited depth and utilizing a set of limited plate sizes to allow for the stock piling of common steel plate sizes. These designs will also act as a framework for future design plans using a modular bridge system

Are Reinforced Concrete Girder Bridges More Economical Than Structural Steel Girder Bridges ? A South African Perspective

This study investigated the cost-effectiveness of steel girders compared with conventional reinforced concrete girders used in bridge construction in South Africa. The investigation considered an existing bridge which required widening as a result of increased traffic flow. The consulting engineers chose two 10 m reinforced concrete girders for the end spans, while two 22 m post-tensioned reinforced concrete girders were used for the central spans. To determine the cost-effectiveness of the consulting engineer’s choice, steel girders were designed for the 10 m and 22m beams based on the relevant South African design codes of practice. The analysis was conducted for both non-composite and composite action between the steel girders and the reinforced concrete bridge deck. Based on the design calculations, a cost comparison was performed. The investigation revealed that steel girders are an economically viable option when off-the-shelf steel sections up to 10m in length are considered. For the 10 m girders, a significant cost saving was achieved for both noncomposite and composite construction compared with reinforced concrete. However, for the 22m spans, the post-tensioned reinforced concrete girders are significantly more cost-effective compared with steel plate girders. Thus, bridge design engineers should consider steel girders as an option during the conceptual design stage for end spans. A survey was also conducted among senior engineering professionals to determine the reason(s) for the apathy towards using structural steel sections as girders in bridge construction in South Africa

Seismic design of steel beam-to-column joints with reduced beam section using European hotrolled

The design rules on Reduced Beam Sections (RBS) are covered in the Eurocodes in EN1998-3 as a possible solution to improve rotation capacity of beams for the retrofit of existing structures. The design rules are very similar to those in AISC358 provisions, although European cross-sections and steel grades are different. Research pieces on RBS in a European environment are few and do not study this matter with an extensive parametric study to assess their behaviour. Moreover, the design rules in EN1998-3 only show how to design the weakened section of the beam, but they do not provide any additional information on whether further action is needed on the structure for the design of other members such as braces or if special considerations need to be made for connection detailing. The current state of the Eurocodes does not consider the design of a new structure with RBS, while AISC358 provisions do allow for new RBS designs. The aim of this PhD thesis is to study the behaviour of the RBS and find the most relevant design parameters affecting its response in a beam-to-column assembly level and to study the benefits of incorporating RBS as a solution for the design of new structures in seismic areas. In order to fulfill the first goal, a numerical model has been developed in Abaqus in order to assess the behaviour of RBS and to discuss the results obtained from them. Hot-rolled European sections have been studied from the HEA and IPE cross-section families, as well as a built-up slender girder and an American Jumbo section. Several different cutouts (or trimmed flange widths) are investigated, as well as S235 and S355 steel grades with their cyclic hardening properties. The influence on the column web panel strength is also considered in the parametric study. The results obtained are then examined to compare degradation ratios, overstrength ratios, lateral-torsional buckling development, dissipated plastic work and plastic damage by means of equivalent plastic strains (PEEQ). In order to fulfill the second goal, two different studies have been performed to assess the influence of the RBS in a structure subjected to seismic load. The behaviour of a structure provided with RBS is compared to that of a control structure without RBS. The results have been obtained and the differences found have been quantified in order to objectively report the benefits found when adopting RBS After having studied the behaviour of the RBS both locally (at a beam-to-column level) and globally, the main conclusions have been derived. Also, design recommendations to take into consideration for the design of new RBS are provided in order to ensure a proper behaviour of the RBS when subjected to seismic loads and to guarantee overall good structural behaviour.Les regles de disseny de les bigues de secció reduïda (RBS) es cobreixen als eurocodis en la norma EN1998-3 com a possible solució per millorar la capacitat de rotació de bigues per a la rehabilitació de les estructures existents. Les normes de disseny són molt similars a les de les disposicions de l'AISC358, tot i que les seccions transversals europees i els graus d'acer són diferents. Les investigacions sobre RBS en un entorn europeu són poques i no estudien aquest tema amb un ampli estudi paramètric per avaluar el seu comportament. A més, les regles de disseny de la norma EN1998-3 només mostren com dissenyar la secció reduïda de la biga, però no proporcionen informació addicional sobre si cal fer més accions a l'estructura per al disseny d'altres elements o si calen altres consideracions especials en el detallat de la connexió. L'estat actual dels eurocodis no contempla el disseny d'una nova estructura amb RBS, mentre que les disposicions AISC358 permeten nous dissenys de RBS. L'objectiu d'aquesta tesi doctoral és estudiar el comportament de les RBS i trobar els paràmetres de disseny més rellevants que afecten la seva resposta a nivell local de biga a columna i estudiar els avantatges d'incorporar RBS com a solució per al disseny de noves estructures en zones sísmiques. Per complir el primer objectiu, s'ha desenvolupat un model numèric amb Abaqus per avaluar el comportament de RBS i discutir els resultats obtinguts d'ells. S'han estudiat seccions europees laminades en calent pertanyents a les famílies de seccions transversals HEA i IPE, així com una biga esvelta armada i una secció Jumbo americana. S'investiguen divers os retalls (o amplades d'ales de biga retallades), així com els graus d’acer S235 i S355 amb les seves propietats d'enduriment cíclic. La influència de la resistència relativa de la zona de l'anima de la columna també es considera en l’estudi paramètric. A continuació, s'examinen els resultats obtinguts per comparar les ràtios de degradació, les ratios de sobrerresistència, el desenvolupament de vinclament lateral-torsional, l'energia dissipada per deformació plàstica i el dany plàstic mitjançant deformacions plàstiques equivalents (PEEQ). Per tal de complir el segon objectiu, s'han dut a terme dos estudis diferents per avaluar la influència de la RBS en una estructura sotmesa a càrrega sísmica. El comportament d'una estructura proveïda de RBS es compara amb el d'una estructura de control sense RBS. S'han obtingut els resultats i s'han quantificat les diferències trobades per tal d'informar objectivament dels beneficis trobats en adoptar RBS. Després d'haver estudiat el comportament de la RBS tant a nivell local (a nivell de biga a columna) com a nivell global, s'han extret les principals conclusions. A més, es proporcionen recomanacions de disseny a tenir en compte per al disseny de nous RBS per tal de garantir un comportament correcte de l'RBS quan està sotmès a càrregues sísmiques i per garantir un bon comportament estructural en general.Postprint (published version

Design and construction of highway bridge over Etowah River near Cartersville, Georgia

M.S.F. C. Snow and J. M. Smit