bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of End Restraint on Column Strength - Practical Applications
Authors: Bjorhovde Reidar
Published: April 2024

The behavior, strength and design of columns constitute a subject area that probably has received more study and discussion than most structural engineering problems. As a result, a large number of increasingly more accurate solutions have been developed, and the design approaches are legion. The basic column is a centrally loaded, pinned-end member. The original solution for the elastic case was provided by Euler in 1759, and advances over the years have incorporated the influences of residual stresses, initial crookedness and load eccentricity, to mention some of the primary factors. Recognizing that columns are rarely, if ever, pinned-end in actual structures, but rather connected to the other components of the structure by a variety of connection types, recent studies have developed solutions that also take into account the effect of end restraint. As can be expected, there is good agreement between theoretically determined column strengths and those obtained in column tests. This has been facilitated by the use of computer programs that can take into account the many column strength parameters, including their random characteristics.
Bracing Connections for Heavy Construction
Authors: Thornton William A.
Published: April 2024

The design of complex connections is not an exact science. Over the years, an intuitive approach to connection design has become widely accepted. This approach is based on the idea the structure (and parts thereof) will behave as the designer dictates, if he provides a path of adequate strength for the load (or loads) to follow. This "adequate strength path" is determined from the principles of statics and strength of materials. About 30 years ago, this intuitive load path method of design was put on a rigorous basis with the development of the Theorem of Limit Analysis—specifically the Lower Bound Theorem of Limit Analysis, which states: if a distribution of forces in the structure can be found which is in equilibrium with the applied loads, and if these forces everywhere within the structure are of such a magnitude that the yield stress (or yield criterion) is nowhere exceeded, then the applied loads are less than, or at most equal to, the loads required for collapse (unbounded yield deformations) to occur. Thus, if a load path is provided, the elements of which are in equilibrium with the applied loads, and if the stresses in these elements nowhere exceed the yield stress, a safe design will have been achieved. Also, the relative stiffness of the various connection elements should be considered in order to minimize the possibility of fracture.
Nonlinear Analysis of Eccentric Bolted Connections
Authors: Rutenberg Avigdor
Published: April 2024

A simple approximate step-by-step method is proposed for the nonlinear analysis of fastener groups subject to eccentric shear. The procedure replaces the traditional trial and error solution by a series of incremental linear elastic analyses. Rigid plate-piecewise linear bolt model is assumed. Conservative, yet sufficiently accurate results may generally be expected. With this approach it is possible to trace the development of plastification and the migration of the incremental instantaneous center of rotation with increasing loading.
Prying Action- A General Treatment
Authors: Thornton William A.
Published: April 2024

The 8th Edition AISC Manual uses a model for predicting the prying force which was recommended in the book by Fisher and Struik. Unlike the approach taken in the 7th Edition Manual, this method is not restricted to specific bolt-plate combinations, since all major parameters which influence the prying action are included in the model. The Q denotes the prying force per bolt and is assumed to act as a line load at the edge of the flange. Test results have shown this to be a reasonable assumption for conditions near ultimate, as long as the edge distance a is within certain limits. The tensile load in the fastener is Bc, and the corresponding applied load per bolt is equal to T. The bending moment at the interface between the web and the flange is taken as Mc, and the moment at the bolt line due to prying force Q is taken equal to daMc where d is equal to the ratio of the net area (at the bolt line section bb)and the gross are a (at the web face section aa) of the flange. The a represents the ratio between the moment per unit width at the centerline of the bolt line and the flange moment at the web face. When a = 0, it corresponds to the case of single curvature bending, i.e., no prying action, and a = 1 corresponds to double curvature bending and maximum prying action. Note that, from physical considerations, 0
A Design Aid for Connection Angle Welds Subjected to Combined Shear and Axial Loads
Authors: Loomis Kenneth M. , Thornton William A , Kane Thomas
Published: April 2024

The Eighth Edition AISC Manual of Steel Construction contains tables to assist in the analysis and design of various weld groups under eccentric loads. These are Tables XIX through XXVI and specialized Tables III and IV for connection angle welds. In all of these tables, although the load is eccentric to the weld group, it is aligned with one of the principal axes of the weld group. It is common in actual connections for the load to have an arbitrary alignment with the weld group principal axes in addition to being eccentric. There are no tables in the Eighth Edition AISC Manual covering these cases. The designer or detailer, therefore, has two options to treat these cases: the elastic method (AISC Manual pp. 4-71, 4-72) or the inelastic method (Manual pp. 4-72, 4-73). Both these options involve extensive calculations for the analysis and design of each connection. In the case of the inelastic method, a computer program is almost a necessity. Such a program is available. The elastic method calculations, while extremely tedious, can be done manually, or with a programmable calculator. The use of this method, however, will produce a connection with a higher degree of conservatism (and therefore, more expensive) than the same connection designed by the inelastic method. The purpose of this paper is to provide a design aid, in the form of a set of charts, that permits the routine use of the inelastic method in the design of commonly used weld groups subjected to loads of arbitrary orientation. These are C-shaped, L-shaped and line welds which occur in shop-welded, framed-beam connections and in similar clip angle to gusset plate welds.
Effective Length Factor for the Design of X-bracing Systems
Authors: El-Tayem Adel A. , Goel Subhash C.
Published: April 2024

X-bracing systems made with single angles are quite common in steel structures. In current practice, the design of X-bracing members may be performed in one of two ways. The first method is to ignore the strength of the compression diagonal in resisting the imposed loads. Conversely, the second method recognizes the contribution of the compression diagonal. This method requires overall buckling of the full diagonal in the out-of-plane direction as well as buckling of one half diagonal about the weak principal axis to be investigated in calculating the effective slenderness ratio. However, for all the hot-rolled single equal leg angles (listed in Ref. 4), the radius of gyration about the weak axis, Z-axis, is greater than half of that in the out-of-plane direction. Accordingly, buckling of full diagonal in the outof- plane direction governs the strength of single-angle compression diagonals. The purpose of this paper is to provide designers with some recommendations regarding the effective length factor to be considered in the design of X-bracing systems. The recommendations were drawn from experimental and theoretical study of full-scale X-bracing specimens. For more details, refer to the original report by the authors.
A Modified Tube Concept for Tall Buildings
Authors: Nair R. Shankar
Published: April 2024

Framed tubes (beam-column frames on the perimeter) are among the most widely used structural systems for providing lateral stability and resistance to lateral loading in tall buildings. This system has been used successfully in many of the worlds tallest structures. This paper will present andexamine a different method of improving the efficiency of framed tubes for tall buildings. As in the techniques mentioned before, the basic concept is to concentrate a large part of the column area and gravity load at the corners of the tube. This is achieved by assignment of strength and stiffness among the members on the perimeter of the building to create a structure that could be labeled a softsided tube.
Viscoelastic Damping Devices Proving Effective in Tall Buildings
Authors: Caldwell D.B.
Published: April 2024

When the World Trade Center in New York City opened its doors as the tallest building in the world in 1972, it gained instant public attention. But a design first in the 110-story twin towers was, and still is, little noticed outside the group of engineers and scientists that were close to the project. That design feature is the 20,000 viscoelastic dampers in the structural system that absorb the punch of unusual as well as average winds. The dampers reduce perceived sway and acceleration in the upper floors. They do this job by absorbing and dissipating vibrational energy transmitted by the wind to structural members. Although that application was 14 years ago, viscoelastic vibration damping devices are relatively new in the sense they have presently been used in only two tall buildings. Nevertheless, the devices offer a number of advantages, and for that reason were selected to be incorporated in the second structure, Seattles 76-story Columbia Center. The effect of damping, or the dissipation of energy from a vibrating system, is well known to every structural engineer. When wind meets the face of a tall building, air spins off around the structure in vortices that push the building back and forth, transverse to the direction of the wind. This movement is damped by air resistance, friction at joints and internal friction in the building materials. In almost all cases, engineers rely on methods such as the structural systems, mass and shape of the building, to provide damping effect.
Lateral Load Distribution in Multi-girder Bridges
Authors: Walker William H.
Published: April 2024

This study of the distribution of internal forces in bridge structures is motivated in part by the sense that simple formulations may be perhaps inaccurate, restrictive and uneconomical in the design process. In the age of computerized structural analysis, the differences between the results of so-called exact, and now less costly, analyses and simplified load distribution rules are apparent. The availability of a variety of structural analysis systems programs greatly expands the options available to the bridge engineer. For slab and longitudinal girder bridges, a structural solver which will handle a three-dimensional frame combined with plate and shell finite elements can produce an "exact" analysis. SAP, NASTRAN, FINITE, ANSYS and SAP80 are examples of this type of program. These systems are implemented on machines ranging from supercomputers to desktop microcomputers. Programs such as SAP80 are accessible to the individual engineer on a personal, not corporate basis. However, the size of the problem and the range of analytical refinement available to the PC is restricted at present. Some level of simplification is needed, but even so considerable refinement over the present distribution rules can be achieved. Application of the analysis system does not involve the development of new computer programs—rather an application of an input "language" to the task of describing the loads and structure for analysis. Important also is a clear understanding of the idealization and specific structural theory underlying the system to be used. Once a paradigm input is written, the solution for a family of bridge types is usually simple. This paper provides an overview of insights gained on idealization and simplification for analysis and selected illustrative results developed on AISI Project 332, "Lateral Load Distribution for Multigirder Bridges." Detailed information will become available in the project final report. Discussed are structural idealizations of the bridge and deck systems accomplished by use of (1) the "exact" idealization of a shell bending element (RFSHELL) with axial membrane forces placed eccentric to the girders and diaphragm elements, (2) the grid with plate bending elements (RPB12) and (3) the simple grid for which both the transverse effect of the deck and composite action are taken into account (GRID). Selected results will be used representing simple and continuous bridges with a variety of span lengths, widths, number of girders and slab thicknesses.
The AASHTO Guide Specification for Alternate Load-factor Design Procedures for Steel Beam Bridges
Authors: Grubb Michael A.
Published: April 2024

The 13th Edition of the AASHTO Standard Specifications for Highway Bridges includes provisions for Load Factor Design (LFD) of steel bridges by the strength design method. Limit-state criteria are provided in LFD that ensure that specified structural performance requirements are satisfied. In LFD, shear and moment envelopes are determined by elastic analysis with limited distribution for the effects of local yielding. Therefore, sections are proportioned for strength equal to or greater than required by the envelopes. After 10 years of AISI-sponsored research, Autostressdesign procedures are now included in the AASHTO Guide Specification for Alternate Load-Factor Design Procedures for Steel Beam Bridges Using Braced Compact Sections. Autostress is a procedure that extends the existing LFD rules by introducing improved limit-state criteria. These criteria permit inelastic load redistribution in continuous-beam bridges under heavy loads while satisfying the same structural performance requirements as LFD.
The Economies of LRFD in Composite Floor Beams
Authors: Zahn Mark C.
Published: April 2024

The AISC Load and Resistance Factor Design (LRFD) Specification represents the state-of-the-art approach in the U.S. for routine structural steel design. Based on a reliability, ultimate strength theory, use of the LRFD Specification may have an economic advantage over the current 8th Edition AISC Manual of Steel Construction, Allowable Stress Design (ASD) Specification. An economic advantage of reduced weight of building elements, while meeting all strength and serviceability requirements, is sure to exist. One major building element where the full economy of LRFD could be realized is in composite floor beam construction. A comprehensive study is thus warranted. The purpose of this paper is to report the findings of an in-depth comparative design study between the recently published LRFD and the established ASD Specifications for simply supported composite floor beams. The results are based on a direct beam weight comparison of over 2,500 composite beam designs and shear stud requirements using A36 steel.
Jointless Bridge Decks
Authors: Wasserman Edward P.
Published: April 2024

Todays bridge designer is striving essentially to achieve the same goals as his counterparts were 50 years ago: long term serviceability, low maintenance characteristics and economy of construction. While we have mastered new techniques such as welding, composite decks, hybrid girders, load factor and autostress designs, we still cling to many of the old ideas that lessen the potential for achieving our goals. One of the more important aspects of design, the reduction or elimination of roadway expansion devices and associated expansion bearings is overlooked consistently, or avoided. Contractors, engineers, producers and fabricators of steel bridges should examine the possibilities for minimum or no joint structures to provide your clients the most durable and cost-effective product, as well as to remain competitive, as an industry, with alternate design materials.
Design of 8-bolt Stiffened Moment End Plates
Authors: Murray Thomas M. , Kukreti Anant R.
Published: April 2024

This paper presents two design procedures for the 8-tension bolt, stiffened, extended, moment end plate shown in Fig. 1. The resulting end-plate design will be satisfactory for use in Type 1 construction (rigid-frame) as defined in Ref. 1 or, with appropriate modifications, as a FR type (fully restrained) connection as defined in the LRFD design notation.2 With bolt size limited to a maximum of 1½ in. dia., the configuration is capable of developing the full moment capacity of most available hotrolled beam sections. The two design procedures are limited to use with A36 steel and A325 bolts.
Effect of Connector Spacing and Flexural-torsional Buckling on Double-angle Compressive Strength
Authors: Zahn Cynthia J. , Haaijer Geerhard
Published: April 2024

The 1986 AISC Load and Resistance Factor Design (LRFD) Specification for Structural Steel Buildings includes new rules affecting the design of built-up members composed of rolled shapes. These rules are based on the result of recent studies which indicate connector spacing has a direct effect on the strength of a built-up member buckling out of the plane separating the individual members; for example, about the Y-Y axis for two back-to-back angles. Various test results have provided the necessary information to develop a formula for a "modified" slenderness ratio. The application of the slenderness ratio is straightforward, as illustrated in the 1st Edition of the Load and Resistance Factor Design Manual of Steel Construction where new design aids are available to assist in determining the number of connectors and the accompanying design strength for double angles. The LRFD Specification also includes formulas for flexural-torsional buckling, which are used to determine the final design strength.
Design of Diagonal Cross-Bracings: Part 2 Experimental Study
Authors: Picard A. , Beaulieu D.
Published: April 2024

The theoretical study reported in the first part of the paper (AISC Engineering Journal, 3rd Qtr., 1987, pp. 122-126) showed the transverse stiffness offered by the tension diagonal in cross-bracing systems is sufficient for assuming that, for out-of-plane buckling, the effective length of the compression diagonal is 0.5 times the diagonal length, when the diagonals are continuous and attached at the intersection point. Two series of tests were performed to demonstrate the validity of the theoretical study. Seven transverse stiffness tests were carried out to demonstrate the validity of the equations used to determine the transverse stiffness provided by the tension diagonal. Fifteen buckling tests were carried out to demonstrate the validity of the equation used to determine the effective length factor. Both series of tests are reported in this second part of the paper.
A New Approach to Floor Vibration Analysis
Authors: Tolaymat Raed A.
Published: April 2024

Floor vibrations analysis is one of few structural engineering topics that combine static and dynamic analyses, which makes it more interesting as well as more complicated. The subject is becoming increasingly familiar to structural designers as more and more lightweight floors exhibit varying degrees of vibration susceptibility. In the past, literature on this problem and ways to predict and prevent it were lacking. During the last 20 years, however, several methods have been developed to predict the susceptibility of floors to annoying transient and steady-state vibrations. To date, methods developed have dealt independently with either the transient or the steady-state response of a floor system. The most popular methods of analysis have been: (1) Wiss and Parmelee rating factor R, (2) Modified Reiher-Meister frequency-amplitude scale and (3) Murrays acceptability criterion.3 Prior to discussing the validity of these three methods, it is believed that introducing a brief description of floor behavior under transient and steady-state conditions is warranted.
Performance of Large Seismic Steel Moment Connections Under Cyclic Loads
Authors: Popov Egor P. , Tsai K.C.
Published: April 2024

Cyclic behavior of recently completed 18 tests in full-size beam-to-column steel moment connections is described. Main emphasis is placed on moment connections of beams to column flanges having plastic moduli of the flanges alone less than 70 percent of the respective plastic moduli of the total beam section. Also considered, cyclic behavior of improved beam-to-column web moment connections as well as some unconventional beam-to-column flange moment connections.
Design Aid for Required Moment of Inertia of Simple Beams
Authors: Eisenman Mark L.
Published: April 2024

The AISC Manual of Steel Construction and other publications include tables which permit calculation of beam deflections for simple loading cases after a preliminary section has been selected. To design for a specific deflection criterion, these tables may be used in iterative fashion for a series of trial sections, or the formulas may be inverted to solve for a required moment of inertia when the limiting deflection is known. In either case, use of the formulas is cumbersome and prone to error, especially in converting to consistent units. Presented here is a table of formulas which permit direct solution for required moment of inertia for several simple loading cases, for the two most common deflection criteria, L/240 and L/360. The author has found these formulas much simpler and quicker to use, because the constants in the formulas already incorporate the conversion factors for commonly used units.
Selecting Laterally Unsupported Beams of Least Weight
Authors: Brandt G. Donald
Published: April 2024

Selecting Laterally Unsupported Beams of Least Weight
Unbraced Frames with Semi-Rigid Composite Connections
Authors: Ammerman Douglas , Leon Roberto T.
Published: April 2024

The benefits of semi-rigid connections are well known and much has been written about their use in braced frames and in Type 2 construction. One of the reasons these methods are not being used frequently by designers is that most semi-rigid connections are highly nonlinear, and analysis of the behavior of frames using them is difficult. One type of connection which may be able to overcome this difficulty is the semi-rigid composite connection. This is a connection made from a typical pinned end connection (e.g., seat angle and web clips or double web angles) and continuous slab reinforcement across the connection. Tests on the connection with seat angle (Fig. 1) by the authors have shown this connection type has a high degree of linearity in the service load region and that its ultimate capacity is easy to predict. This paper describes a design procedure for unbraced frames utilizing semi-rigid composite connections such as those described above. Two design examples, one for a four-story structure and one for a ten-story structure, and comparisons of their behavior with that of rigidly designed frames are included.
Design of Small Base Plates for Wide Flange Columns
Authors: Thornton William A.
Published: April 2024

The 9th Edition of the AISC Manual of Steel Construction uses the Murray-Stockwell method for analysis of small base plates, i.e., plates that are only slightly larger than the column depth d and width bf. It combines this method with the cantilever method of the 8th and earlier editions for large base plates. The Murray-Stockwell method assumes a bearing pressure of Fp, the maximum permitted, over an Hshaped contact area under the column cross-section between the plate and the concrete. The cantilever method, on the other hand, assumes a uniform bearing pressure, fp
Hardness Testing of Thermal Cut Edges of Steel
Authors: Wilson Alexander D.
Published: April 2024

Recent concerns for the quality of thermal cut edges (TCE) of steels used in bridge construction led to a research program funded by the American Iron and Steel Institute. The results of this program are reviewed. The program found that the hardness of the TCE was the most important variable influencing the quality of a TCE as measured by a bend test. Plate chemistry (carbon content), Charpy V-notch toughness, thermal cutting speed and plate temperature were also found important. A suggested technique for minimizing the variability in testing for TCE hardness, which utilizes localized grinding of the TCE location to be tested, is presented.
High-Strength Bolts for Bridges
Authors: Verma Krishna K. , Beckmann Fred R.
Published: April 2024

The use of substandard and mismatched bolts continues to be a major concern to bridge owners in the United States. Based on FHWA-sponsored research at the University of Texas, supplemental specifications were developed and issued modifying fastener manufacturing, testing, and installation procedures. Nearly all bridge bolts are designed for dynamic loading. They are designed to resist either tension forces and/or shear forces. Fatigue concerns govern bolts designed for cyclic tension forces. Cyclic shear forces require slip critical connections. Both loading conditions require bolts to be installed to a minimum preload. The FHWA recommendations were developed in order to assure the ability of bolts to achieve this preload. Minimum nut strength is increased, maximum bolt strength is reduced, thread fit tolerance is reduced, additional rotational-capacity testing is required, and additional testing, documentation, handling and shipping requirements are imposed. The rationale for these new FHWA provisions are discussed. Finally, slip critical joints depend upon friction between faying surfaces to develop strength. Values of slip resistance or coefficient of friction for various paints and coatings must be determined by testing. Bolt design parameters depend upon minimum values of tested coatings.
An Experimental Study of Block Shear Failure of Angles in Tension
Authors: Epstein Howard I.
Published: April 2024

Structural tension members are designed to resist yielding of the gross section or rupture of the minimum net section, taking into account the effects of stagger and shear lag. The shear lag effect must be considered when all the components of a tension member are not transmitting the load to the connection. For short connections, an angle connected by one leg may fail in a combination of tension perpendicular to and shear parallel to the loaded axis. This type of failure has been termed block shear when investigated for beam web connections. Most of the international codes for steel design have not considered this type of failure. The current AISC ASD and LRFD specifications do incorporate formulae, in their respective commentaries, to calculate block shear failure capacities. This paper reports on the results of full-scale testing of double-row, staggered, and unstaggered bolted connections of structural steel angles. The effect of the variation of several parameters are presented. The current code provisions are found to be less conservative for block shear failure than net section tensile failure in angles and a revised treatment is suggested.
Load and Resistance Factor Design of Welded Box Section Trusses
Authors: Packer Jeffery A. , Henderson J.E. , Wardenier Jaap
Published: April 2024

After the advent of Hollow Structural Sections (HSS) in Britain, experimental and theoretical studies on welded connections with square and round members took place at Sheffield University, leading to the design recommendations of Eastwood and Wood. These were quickly implemented in Canada and publicized by Stelco in the worlds first HSS connections manual. Shortly thereafter they were available to U.S. engineers in an AISI Guide. The more well known reference document in the U.S. for the design of tubular connections is Chapter 10 of AWS D1.1.5 These AWS recommendations originally evolved from a background of practices and experience with fixed offshore steel platforms of welded tubular construction. The connection capacities therefore were expressed with much greater confidence for circular tubes than for box tubes (square or rectangular hollow sections). During the 1970s and 1980s a large amount of experimental and theoretical research on connections between manufactured HSS has taken place in many countries, but almost exclusively outside the U.S. Much of it has been coordinated and synthesized by technical committees of CIDECT (ComitÃ International pour le DÃveloppement et lEtude de la Construction Tubulaire) and IIW (International Institute of Welding). An excellent appreciation of the behavior of welded connections in HSS trusses has evolved and comprehensive design recommendations have consequently been issued by IIW, Kurobane, Wardenier, CIDECT and Dutta and Wurker. Very recently an international consensus has been obtained for LRFD design of statically-loaded, welded connections involving hollow section members in planar trusses.
Design Aid-Anchor Bolt Interaction of Shear and Tension Loads
Authors: Scacco Mario N.
Published: April 2024

A common practice among structural engineers involved in industrial building design is to specify either ASTM A36 threaded rod bolts or A307 headed bolts for use as cast-inplace anchors to carry combined shear and tension forces to the foundation. It is also fairly common to specify ASTM A325 or equivalent strength material for anchor bolts which must carry higher forces than can be accommodated by ordinary carbon steel bolts. Several articles have been written in the past ten years which have addressed the problem of anchor bolt design for combined loadings. By consolidating and summarizing the available data, the problem can be simplified for most situations encountered in normal practice. A conservative design approach is warranted, as suggested by Marsh and Burdette since test data is limited and consequences of bolt failures are quite unacceptable for steel structures which must carry expensive industrial equipment.
Live Load Deflections in a Prestressed Steel Beam Bridge
Authors: Welden Neil
Published: April 2024

The subject of this investigation is a 240 ft by 30 ft three span continuous prestressed steel beam bridge, skewed 30 degrees clockwise, over Silver Creek on U. S. Highway No. 6 in Pottawattamie County, Iowa. The spans are 73 ft, 3 in.—93 ft, 6 in.—73 ft, 3 in. The slab is supported by four lines of beams, spaced 9 ft, 8 in. center to center, spliced 22 ft, 0 in. each side of each interior support, near the point of dead load contra-flexure. The exterior beams are 30 WF 108, and the interior beams are 33 WF 130. All beams are ASTM A36 steel, and all have high strength steel cover plates. The design live load is AASHO H20-S16-44. Live load moments causing tension in the bottom flange and compression in the top flange of the beams are resisted by composite action of the beam and slab. The structure will hereafter be referred to as the Silver Creek Bridge.
Column Stability under Elastic Support
Authors: Higgins T.R.
Published: April 2024

Professor Galambos has shown that the amount of diagonal bracing or masonry wall needed to prevent sidesway of a steel building frame under gravity loading is relatively small. The approach which he used can provide useful stability solutions for (a) frames that depend entirely upon their own bending stiffness for lateral support yet include columns without rigid connections and (b) columns with flexible lateral support. It has been shown that, in elastic frames, the value of the critical gravity load producing incipient sidesway in a rectangular frame is not greatly influenced by concurrent bending stress resulting from moment at the ends of the columns. Hence presence of such stresses will be ignored in the following procedures for designing to prevent premature joint translation.
Method of Combining Mechanisms in Plastic Analysis
Authors: Pincus George
Published: April 2024

Given the collapse load for the independent mechanisms of a structure, the failure load of the combined mechnisms can be obtained by superposition if hinge cancellations are noted. Although this method has been presented previously, a modified type of solution is presented herein and an example is given. This simplified method gives a better understanding of the actual process of combining independent mechanisms and the resulting combined mechanism thereof. Superposition is valid for any number of component independent mechanisms. In the simplification presented, an equation is written for each location of desired plastic hinge cancellation in the combined mechanism. In this "consistent deformation" type of solution, each independent mechanism will bemultiplied by a suitable factor which is obtained from the equations. The collapse load of a combined mechanism composed of four independent mechanisms is found as an illustration of the method.
The Warping Constant for the W-Section with a Channel Cap
Authors: Lue Tony , Ellifritt Duane S.
Published: April 2024

It is common practice in crane runway beams to place a channel, open-side down, over the top flange of a W-section to increase its lateral stability. This is done because it is not always convenient to brace the compression flange between columns. The lateral-torsional buckling capacity of a singly symmetric section may be determined by the formulas without knowing the warping section constant. However, these formulas were developed from research on three-plate mono-symmetric sections. If one is to develop a similar equation for the case of the W-section with a channel cap, it is necessary to return to the basic theory of lateral-torsional buckling and that means that one must calculate the warping constant (Cwc) for the cross-section. It is not a difficult matter to do this with a computer, but since the program may not be available to everyone, it would be useful to develop a simple empirical equation for preliminary design, making use of the section properties already given in the AISC steel manual.
Design Strength of Concentrically Loaded Single Angle Struts
Authors: Zureick A.
Published: April 2024

In practice, the majority of single angle struts are eccentrically loaded, and an attempt to calculate exactly the strength of such members is a task of formidable complexity. Therefore, the designer often relies on approximate methods and guidelines, in which the key ingredient is the value of the design strength when the strut is loaded concentrically (AISC 1986, ASCE 1988, and Adluri and Madugula 1992). In this brief note, a step-by-step solution and load tables are presented for the determination of the design strength of concentrically loaded single angle struts according to the AISC 1986 LRFD Specification. Equation A-E3-7, of Appendix E of the LRFD Specification requires the computation of the torsional-flexural buckling stress as the smallest of the three roots of a cubic equation.
Design of I-Beam to Box-Column Connections Stiffened Externally
Authors: Ting Lia-Choon , Shanmugam Nandivaram E. , Lee Seng-Lip
Published: April 2024

This paper is concerned with I-beam to box-column connections stiffened externally. A design method to determine the dimensions of T-stiffeners is proposed. Connections of I-beams and box columns for a wide range of dimensions were studied by the finite-element method and found to satisfy the basic design criteria for a moment connection. The Ramberg-Osgood function was used to curve-fit the moment-rotation curves based on the geometric parameters of the connections and the results are found to agree well with those from the finite-element analyses. Finally, the design procedure and the curve-fitting parameters were compared with the experimental results of a four-way connection tested to failure.
LRFD Analysis for Semi-Rigid Frame Design
Authors: King Won Sun , Chen Wai-Fah
Published: April 2024

A practical LRFD-based analysis method for the design of semi-rigid frames is proposed. The proposed method uses first-order elastic analysis with a notional lateral load for the second-order effects. In the proposed method, a simplified three-parameter model describing the tangent rotational stiffness of semi-rigid connections is used.
Discussion: Design of Pipe Column Base Plates Under Gravity Load
Authors: Valley Michael
Published: April 2024

Discussion
Steel Frame Stability Design
Authors: Visser Mike
Published: April 2024

Many stability evaluation methods have been proposed over the last thirty years. The SSRC lists five specific methods of analyzing steel frames for stability: the effective-length concept; second-order, inelastic analysis; the PD method; the Merchant-Rankine formula; and the moment amplification method. The SSRC recommends evaluating frame stability separately from individual member analysis, while the AISC includes stability evaluation in the individual member selection process. The AISC requires that second-order effects be considered in the design of frames and that in unbraced frames the effective length factor, K, be not less than unity. The frame stability provisions of the AISC Specifications are based on the effective length concept, using the moment amplification method to account for second-order effects. It should be noted that the AISC does not prohibit the use of methods other than the effective length concept. The effective length concept typically is implemented through the determination of column effective length factors, K, using an alignment chart. The sidesway uninhibited alignment chart provides K factors for use in evaluating the lateral stability of the frame at the individual member level. The alignment chart is based on the assumption all columns in a story are equally critical and equally add to the lateral resistance of the frame. A method for evaluating frames in which all members do not equally contribute to a frame's lateral resistance has been proposed by Yura. However, it has been shown Yura's method is overconservative in frames in which the stability is provided by columns carrying a small portion of the story gravity load. One reason for this conservatism is the application of inelastic buckling allowable stresses where elastic buckling is clearly applicable.
A Rational Approach to Design of Tee Shear Connections
Authors: Thornton William A.
Published: April 2024

A tee shear connection is similar to a shear tab in that there is a perceived lack of ductility in the connection which could cause premature fracture in the shop weld or shop bolts, i.e., fracture before the connection is able to absorb the self-limited beam end rotation in a ductile manner. This problem is resolved with a shear tab by two ductility requirements
Correction: Strength and Serviceability of Hanger Connections
Authors: Thornton William A.
Published: April 2024

Correction
Block Shear of Structural Tees in Tension- Alternate Paths
Authors: Epstein Howard I.
Published: April 2024

There is little in the way of test results for structural tees used in tension. This is especially true when it comes to results for block shear failures. By varying only the depth of the web, a limited experimental program was designed to produce failures ranging from net section to block shear for tees connected by bolts through their flanges. As the depth increased, block shear failures did result, but not along the paths anticipated. This alternate block shear path is the focus of this paper.
Closure: Comparative Effectiveness of Tightening Techniques for A490 1 1/4- in. Diameter Bolts
Authors: Dahl Joan S. , Lu Le-Wu , Fisher John W. , Abruzzo John
Published: April 2024

Closure
Rational Basis for Increased Fillet Weld Strength
Authors: Iwankiw Nestor R.
Published: April 2024

The fillet weld strength increase occurs because of sensitivity to the direction of loading. At a loading perpendicular to the longitudinal axis of the weld, the weld has been shown to be on the order of 50 percent stronger than the lower bound for parallel loading. A full range of strength variation exists for intermediate force angles of 0-90 degrees. In the past, this effect had been conservatively and conveniently ignored for design but has now been recognized. While the detailed experimental justification reported in the literature is convincing by itself, the objective of this paper is to also demonstrate this increased strength with a simple rational model derived from first principles.
Closure: Specifying Bolt Length for High-Strength Bolts
Authors: Carter Charles J.
Published: April 2024

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Integrity of Structural Steel After Exposure to Fire
Authors: Tide Raymond H.R.
Published: April 2024

Perceptions of fire vary depending on the circumstance to which the individual is exposed. Controlled fires are rarely given much thought in our daily experiences. Uncontrolled fires, with the specter of buildings collapsing, the implied damage, potential injury and loss of life have created a very negative image. A negative connotation often exists that anything exposed to fire and heated to a high temperature must be damaged, regardless of the appearance of the structural members. Exposure to fire will subject structural steel to thermally induced environmental conditions that may alter its properties. Assessing these altered properties requires a combined knowledge of metallurgical and structural behavior as the fire raises the steel temperature and the steel later cools. Knowledge of steel properties and behavior developed from basic steel production, thermal cutting, thermal or mechanical straightening (or curving), heat-treating and welding provides the requisite information.
Live Load Distribution in Integral Composite Steel Bridges
Authors: Tabsh Sami W. , Mourad Shehab
Published: April 2024

In recent years, there has been an increased interest in integral bridges for highway applications due to their inherent economy, serviceability, and strength. This study deals with the live load distribution of integral composite steel bridges near the abutments. Girder distribution factors for shear and bending moment in interior as well as in exterior beams are determined. A comparison between the response of integral bridges and their jointed counterpart is also included. Single and continuous spans are considered in the investigation. The applied loading is composed of several side-by-side HS20 trucks. Linearly elastic finite element analysis is used to analyze the three-dimensional bridge systems. The results of the study indicated that shear in the interior beams and the corresponding girder distribution factor are lower in integral bridges than in simply supported bridges. As the pile length to fixity increases, the shear and moment in the beams near the integral abutment decrease. Further, as the length of the wingwalls in integral bridges increases, the shear and moment in the interior beams increase.
Closure: A Summary of Changes and Derivation of LRFD Bolt Design Provisions
Authors: Carter Charles J. , Tide Raymond H.R. , Yura Joseph A.
Published: April 2024

Closure
A Comparison of General Design and Load Requirements in Building Codes in Canada, Mexico, and the United States
Authors: Ellingwood Bruce R.
Published: April 2024

Safety and serviceability requirements for limit states design (LSD) have been implemented in codes of structural engineering practice in North America during the past 25 years. The load and resistance criteria in LSD take into account inherent variability in strengths, loads and uncertainties due to approximations and lack of information. The framework of structural reliability theory facilitates the treatment and analysis of uncertainties, and yields criteria that are consistent with a performance objective expressed in terms of reliability. Despite the consistency provided by this conceptual framework, the implementation of LSD in structural engineering practice in Canada, Mexico and the United States has taken somewhat different routes. With recent political developments in North America, the time is opportune to initiate work to remove these differences and to achieve consistency, both in concept and application, of LSD structural codes.
A Comparison of Canadian, Mexican, and United States Steel Design Standards
Authors: Galambos Theodore V.
Published: April 2024

The steel design standards for buildings of the three countries of Canada, Mexico and the United States are compared in this paper. The special emphasis is on the criteria for the stability design of plates, columns, beams and beam-columns. It is shown that while the theoretical and experimental basis for all three codes is common, the final form of the criteria is not the same: different formulas are used for column, beams and beam-columns. Other differences arise from the fact that all three countries use different units. However, the designed proportions of the structural elements and structures are often not significantly different in final execution. Each code has advantage and disadvantages in its details of design. However, there appears to be no major obstacles to arriving at mutually satisfactory codes which are essentially interchangeable among countries.
Closure: The Effects of Over-Compressing ASTM F959 Direct Tension Indicators on A325 Bolts Used in Shear Connections
Authors: Schmeckpeper Edwin R. , Nielsen Richard J. , Gentry Guy
Published: April 2024

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Design of Concrete-Filled Hollow Structural Steel Columns for Fire Endurance
Authors: Kodur Venkatesh K.R. , MacKinnon David H.
Published: April 2024

The benefits of steel hollow structural sections (HSS) from an aesthetic and structural point of view have long been recognized by architects and engineers in Canada, and more recently in the United States. However, when building codes require structural fire protection, the cost of providing such protection can be expensive for exposed members. Filling an HSS column with concrete not only improves the capacity of the member through composite action at ambient temperatures but also provides fire endurance periods of up to 3 hours depending on the load level, section size, concrete strength and reinforcing characteristics. Physical tests and parametric studies recently completed at the National Fire Laboratory in Ottawa have resulted in design equations which predict the load carrying capacity and fire endurance period of concentrically loaded HSS columns filled with plain concrete, barrein forced concrete and steel fiber-reinforced concrete. The design method is presented, case studies are used to illustrate potential applications, and practical suggestions are made regarding construction techniques.
Inelastic Design and Testing of Steel Bridges Comprising Noncompact Sections
Authors: Hartnagel Bryan A. , Barker Michael G.
Published: April 2024

Inelastic design procedures allow the designer flexibility and the possibility of more economical designs by decreasing member sizes and eliminating cover plates and flange transitions at negative moment regions. Previous experimental results show that compact girders designed by these procedures perform satisfactorily when subject to design load levels. Current provisions, however, apply only to compact steel bridges. Expanding inelastic design provisions to include noncompact sections is desirable because of the wide use of plate girders with thinner webs. General inelastic provisions applicable to compact and noncompact sections will create designs that are more consistent over the steel bridge inventory. Previous research has shown that noncompact girders have predictable moment-rotation behavior that can be incorporated into inelastic design provisions. However, although the analytical tools exist, large-scale testing is necessary to validate theoretical engineering practice. Inelastic steel bridge design procedures account for the reserve strength inherent in multiple-span steel girder bridges by allowing redistribution of negative pier region elastic moments to adjacent positive moment regions. The redistribution causes a slight inelastic rotation at the interior pier sections, residual moments in the beam, and some permanent residual deflection. After the redistribution, the structure achieves shakedown: deformations stabilize and future loads are resisted elastically.