bluuebunny/crossref_metadata_2025 huggingface dataset:
An Introduction to Load and Resistance Factor Design for Steel Buildings
Authors: Pinkham C.W. , Hansell W.C.
Published: April 2024

Load and Resistance Factor Design (LRFD) is a major advance toward a simple, rational design of steel-framed buildings. It combines limit states of strength and serviceability with a modern probability-based approach to structural reliability. The essence of LRFD is the assignment of resistance and load factors on the basis of consistent reliability. Developed by T. V. Galambos and his associates at Washington University, St. Louis, LRFD is based on a project sponsored by the American Iron and Steel Institute Committees of Structural Steel Producers and Steel Plate Producers. This paper introduces LRFD, illustrating the treatment of loads and resistance and describing how the numerical values of load and resistance factors were established. Two companion papers also appear in this issue of the Engineering Journal: one describes the proposed LRFD Criteria and Commentary for steel buildings, which are the end product of the research project; the other summarizes design office studies conducted by two consultants during the projects evaluation phase.
A Fresh Look at Bolted End- Plate Behavior and Design
Authors: Krishnamurthy N.
Published: April 2024

End-plate connections of the typical configuration are increasingly used as moment resistant connections in framed structures. However, end plates designed by the prying force formulas in the AISC Manual of Steel Construction may be unrealistically thick. The prying force formulas were proposed by Nair et al., based on their work on tee hangers. Previously, Douty and McGuire and later Agerskov have presented other versions of the same basic model, and/or suggested adjusted coefficients to reflect test results. The research in the U.S.A. and abroad on this topic has been summarized by Fisher and Struik. In the prying force method, the end-plate region around the beam tension flange is considered analogous to a tee hanger. Hence, the terms "tee flange" and "plate" or "end plate" will be used interchangeably in this paper; "tee stem" will likewise correspond to the "beam flange". Figure 3 illustrates the dimensions and forces involved in the application of the prying force method. The section at or near the face of the tee stem at which the applied force is transferred to the tee flange will be designated the "load line"..
Strength Design in Steel Using Programmable Calculators
Authors: Anderson James C.
Published: April 2024

During the past ten years, a gap has developed between large digital computers and manual computing methods. This is particularly true with regard to the analyses and design of structural members. The increasing availability of large computer systems and their associated software, coupled with a dramatic reduction in cost, has placed computer analysis capability well within reach of most structural engineering offices. Member forces can be readily determined using either special frame analysis programs or general purpose programs which are available on commercial computer systems. However, once the member design forces are determined, the engineer must revert to hand calculations for determining and checking the design of the individual members. These calculations can become monotonous and time consuming for a structure of even modest size. Furthermore, such calculations tend to become inaccurate and insufficient. For example, a designer may accept a given section as adequate without trying other possibilities which may lead to a more efficient design. This paper has illustrated the use of a hand-held programmable calculator for the strength design of steel frames. Although the process is only semi-automatic, it still saves the designer from having to perform the rather mundane calculations involved with member selection and checking. Its main attraction is the low cost and ready availability of the calculators, plus the fact that the calculation can be done at the designers desk without extensive data preparation. The procedures assume that the design forces are known. Therefore, a force analysis will have to be done on a larger computer system. It should also be noted that the use of this type of design procedure allows complete interaction of the engineer with this design process. Therefore, engineering judgment decisions can be made and incorporated in the design as it progresses.
A Cautionary Note on Beam Copes
Authors: Milek Jr.
Published: April 2024

Routinely in steel construction it is necessary for many beams to be coped, at either the top or bottom flange, in order to provide clearance around the flanges of the beams which provide support. In by far the majority of cases, hot-rolled laterally supported beams with span-depth ratios in the range of 20 to 24 are involved. Generally shear capacity of the beam web is not a critical factor, the size of the copes are of reasonable proportions, and no particular problems are involved in providing adequate strength for the beam end reaction.
Load and Resistance Factor Design (T.R. Higgins Award)
Authors: Galambos Theodore V.
Published: April 2024

Load and Resistance Factor Design, abbreviated as LRFD, is a scheme of designing steel structures and structural components which is different from the traditionally used allowable stress format, as can be seen by comparing two inequalities. An attempt has been made here to summarize briefly the existing development of the AISC LRFD Specification. Emphasis was placed on the numerous sources on which this document stands. It is one of the several new LRFD-type specifications which are now (1981) appearing throughout the world. These specifications employ several resistance factors and load factors to account for the various types of uncertainties which underlie design. The reliability is to be interpreted as being "notional," i.e., it is a comparative concept. It should not be confused with actual structural failures, which are the result of errors and omissions. Only the natural statistical variation of the parameters is included, and, as in other traditional specifications, human errors must be guarded against by other control measures.
The Bridge Delta Girder: Single-Webbed and Double-Webbed
Authors: Hadley Homer M.
Published: April 2024

The specifications of the American Association of State Highway Officials (AASHO) govern the construction of the great majority of highway bridges in the United States. These specifications determine the dimensions and general relationship of parts in steel girders. Since compliance with these specifications is the sine-qua-non condition upon which allotment of Federal participating construction funds is based, deviations from these requirements are rare. Yet it is a fact that the standard plate girder as produced by the AASHO specifications is not satisfactory in all respects. It is too flexible, too limber, too lacking in lateral stiffness. The 1959 AISC National Engineering Conference paper presented by Mr. E. L. Durkee of the Bethlehem Steel Company, dealing with bridge erection problems, is an earnest plea for providing lateral stiffness in steel members. Of course, after installation of cross-bracing, bottom lateral bracing and a top roadway slab, the plate girder serves admirably, but it can not be said to do so in the early stages of bridge construction.
Steel Shear Walls for Existing Buildings
Authors: Baldelli Jr.
Published: April 2024

After the 1971 San Fernando earthquake in which two Veterans Administration hospitals collapsed, killing 46 people, the VA initiated an extensive program for evaluating and, if necessary, strengthening all VA hospital buildings in earthquake-troubled areas. One of the facilities that required strengthening was the VA Medical Center in Charleston, South Carolina. Because of the complexity of the project, URS/John A. Blume & Associates, Engineers, San Francisco, was selected to serve as structural consultant to Lafaye Associates, Architects, Columbia, South Carolina. Built in 1963, the center is a complex made up of several buildings having from one to five stories. The three main buildings are separated from one another by 2-in. expansion joints. The total floor area of the five-story complex is 350,000 sq ft. Each building uses reinforced concrete flat slab construction with columns at 20 ft on center each way. The structures were originally designed to resist lateral loads caused by wind only. The lateral forces were carried by isolated stair walls and frame action. Whereas the design base shear caused by wind forces was approximately 3% of the total dead load, the new VA earthquake code requires the strengthened structure to handle a base shear of 15%. The existing reinforced columns would be severely overstressed with a base shear of 15%; thus, the building had to be strengthened.
Safe Load for Laterally Unsupported Angles
Authors: Leigh J.M. , Thomas B.F. , Lay M.G.
Published: April 2024

The tables are based theoretically on the constant moment case and use a maximum permissible stress of 0.66Fy, where Fy is the material yield stress. However, for short spans the loads are reduced where necessary to ensure that the maximum permissible shear stresses given in Ref. 1 are not exceeded. The safe loads are applicable for applied loads within half a leg length on either side of the shear centre. The method by which this load is obtained is described under "Calculation of Safe Loads." The safe load shown in the tables is the uniformly distributed load which causes a maximum bending moment equal to the critical constant moment.
Design and Optimization of Plate Girders and Weld-fabricated Beams for Building Construction
Authors: Fleischer Walter H.
Published: April 2024

Currently, design of plate girders and weld-fabricated beams necessitates an iteration of trial designs to establish the web-buckling range used in analysis. The material presented here illustrates an expeditious mathematical and nomo-graphic design method for bisymmetric plate girders and weld-fabricated beams, as well as material-optimization for any given moment-shear combination. The method shown is based on the web-buckling theory (no tension-field action), and on the assumption of flange configurations that do not necessitate bending-stress reductions in the compression flange. Design examples are given numerically and shown on nomo-graphs.
Effective Width Criteria for Composite Beams
Authors: Vallenilla Cesar R. , Bjorhovde Reidar
Published: April 2024

A key factor in the analysis and design of composite flexural members is the effective width of the slab, i.e., that part of the slab that can be relied upon to act compositely with the steel beam. The current design specification for steel building structures in the United States3 gives detailed criteria, as do others. However, these have mostly been developed on the basis of analyses and tests of composite beams without steel deck. It is the purpose of this paper to evaluate the performance of some of the current effective width criteria, and to recommend practical improvements for use in future specifications. Some of the current design criteria that are used to determine the effective width of the slab of composite beams will be evaluated. The results include an examination of the deflection characteristics of composite beams with formed steel deck, including a comparison of theoretical and experimental data. Since only service load deflections have any practical, design-oriented value, the study has been limited to that range of response. For all practical purposes, composite members behave elastically under these conditions. The investigation also examines the influence of the various parts of the steel deck and makes recommendations for design usage.
Tension Butt Joints with Bolts and Welds in Combination
Authors: Jarosch K.H. , Bowman Mark D.
Published: April 2024

Combination joints, also known as load-sharing joints, are connections that use a combination of high-strength bolts and structural welds. Two different types of combination joints are used occasionally in the fabrication of steel structures: shear splices where the bolts and welds share the load on a common shear plane, and connections where the bolts and welds are used on shear planes that are not common. The former type of connection is used sometimes when repairing or modifying a connection; the welds are compact and can be easily added to an existing high-strength bolted connection to provide additional strength. The latter connection type is commonly used in steel beam-column joints. Tests described in this paper provide information on the strength and load interaction characteristics of combination joints for a variety of weld and bolt configurations. The studies include an evaluation of methods currently available for predicting the ultimate tensile strength of combination joints. The combination joints examined in the study are limited to butt joints which use bolts and welds on a common shear plane.
Use of High-strength Steel for Simply Supported Beams
Authors: Wechsler Marius B.
Published: April 2024

As stated by AISC, high-strength steels have proven to be economical choices where lighter members, resulting from use of higher allowable stresses, are not penalized because of instability, local buckling, deflection or other similar reasons. The reduction of dead load and associated savings in shipping costs can be significant factors. However, higher strength steels are not to be used indiscriminately. Effective use of all steels depends on thorough cost and engineering analysis. The purpose of this paper is to find out the cases when high-strength steel, simply supported beams may be economical. The paper refers to High-strength, Low-alloy Steel A572-Gr. 50 only, and assumes its cost is 10% higher than Carbon Steel A36.
Earthquake-resistant Design of Double-angle Bracings
Authors: Astaneh-Asl Abolhassan , Goel Subhash C. , Hanson Robert D.
Published: April 2024

Behavior of steel-braced frames during an earthquake strongly depends on the behavior of bracing members and their connections. In recent years, considerable research has been done on behavior of bracing members under cyclic loading. However, studies on the behavior of their connections are almost nonexistent. A number of observers who have studied structures damaged by earthquakes have reported total or partial failures in the connections of bracing members. These observed failures clearly indicate a need for evaluation of current philosophies and procedures employed in design practice. Simplified design procedures are used in practice even though it is known connections have complex stress distributions. Most of these design procedures are based on the studies of monotonically loaded connections and were intended to be used in design of connections subjected to nonreversible loads. Thus, the cyclic forces and deformations induced in the bracing members and their connections during a strong ground motion earthquake are not considered in such procedures.
Semi-rigid Composite Steel Frames
Authors: Leon Roberto T. , Ammerman Douglas , Lin Jihshya , McCauley Robert D.
Published: April 2024

Semi-rigid, composite steel frames are a new type of structural system being developed to better utilize the composite floor slabs and flexible connections present in common AISC Type 2 frames. This new structural system extends the beneficial aspects of composite action to the negative moment region of continuous beams by providing slab reinforcement across column lines. The resultant system offers significant gains in stiffness and strength not only in the members themselves but also at the connections. Because the connections benefiting most from this action are the relatively flexible ones (not rigid), the name "semirigid composite frames" (SRCF) has been coined. The economies in materials and erection cost associated with composite and mixed construction are widely recognized.1 Composite construction generally results in (1) reductions of steel area needed to support a given load, (2) an increase of overload capacity over non-composite sections, (3) reductions of construction depths and (4) an increase on the safety of the system by providing redundant load paths. Typically, composite action is used to increase the capacity of beams designed as simple spans, but its effect on the overall frame strength and stability is ignored.
Simplified Frame Design of Type PR Construction
Authors: Ackroyd Michael H.
Published: April 2024

Design of unbraced building frames using simple connections between beams and columns has been based historically on Type 2 Construction assumptions. Extensive research on the performance of this type of frame has led to the recommendation that Type 2 Construction should be limited to frames less than 10 stories tall, when the lateral load is resisted entirely by the unbraced frame. Moreover, it was shown that the governing limit state in such frames is overall frame instability under combined wind and gravity loads, initiated by extensive plastification of the leeward column stack. Two common features of this limit state are that girders are loaded to about half their bending capacity and the exterior columns are heavily overloaded in bending. The reason for this inappropriate apportionment of steel to the girders and exterior columns is that the simple connections do possess rotational stiffness and tend to decrease the in-span girder gravity moments by developing a fraction of the fixed-end moments, referred to herein as flexible-end moments. This paper describes a more appropriate model for gravity analysis of frames with flexible beam-to-column connections that enables a simplified design procedure for Type PR Construction.
Reinforcing Loaded Steel Compression Members
Authors: Brown Jack H.
Published: April 2024

Theoretically, it does not seem plausible that a column which is reinforced under load will have the same ultimate capacity as a column reinforced in its unloaded state. Yet there is a tendency to use the allowable stresses for the geometry of the reinforced column for both cases. This question is examined in greater detail in this paper, where the analysis shows that both the geometry of the reinforcement and initial load can affect column capacity. The paper develops a method to determine the capacity of a column reinforced under load based on AISC requirements. The analysis is applicable to any kind of column and reinforcement, but has not been verified by testing. This paper would confirm this, but shows this is not necessarily true for larger L/r values of the same reinforced column. If the effects of residual stresses from welding are ignored, the following examples illustrate how the location of the new reinforcement influences capacity. If a column is already carrying its full dead and live load, only the live load can be removed during reinforcement. The dead load stresses will be frozen in the column core after welding and can influence its capability to carry additional load. The original column, hereafter is referred to as the core. The effects of residual stresses from welding have not been considered in this paper and the reader should consult other publications on the subject.
On Beam-Column Moment Amplification Factor
Authors: Duan Lian , Sohal Iqbal S. , Chen Wai-Fah
Published: April 2024

In designing beam-columns in a steel frame, the LRFD Specification uses two moment amplification factors (B1 and B2) to account for the second-order P—d (member instability) and P—D (frame instability) effects. For beam-columns with joint translation restricted and subjected to end moments only, the B1 factor usually underestimates the P—d effect. However, in some uncommon practical cases, under high axial compression ratio (P/Pe > 0.7) with double curvature bending, it is conservative to estimate the P—d effect. This is due mainly to the fact that, for simplicity, the LRFD Cm expression excludes the influence of the axial load ratio P/Pe. In this paper, an improved Cm expression, written in terms of both the axial load ratio P/Pe and the end moment ratio Ma/Mb, is proposed. The proposed moment amplification factor has been verified by an extensive comparison with the exact analytical solution. It is found that the P-d moment predicted by the proposed formula is more accurate than that predicted by the B1 factor in the present LRFD Specification.
The In-Plane Stability of a Frame Containing Pin-Based Stepped Columns
Authors: Fraser Donald J.
Published: April 2024

This paper presents five graphs and a simple formula from which the in-plane buckling load of a pin based stepped column, forming part of a rigid-jointed frame, can be calculated. These analytical aids were derived from a parametric study of the problem using a proven finite-element stability analysis program. They account for the rotational and translational restraints within the frame system, and enable the designer to readily determine the most critical disposition of the crane loads. The method is illustrated by an example.
Redundancy in Highway Bridges
Authors: Frangopol Dan M. , Nakib Rachid
Published: April 2024

The present study primarily reviews definitions of deterministic and probabilistic system redundancy measures which could be used in the design and evaluation of highway bridges. Some of these measures are used to evaluate the redundancy of an existing steel girder bridge. In this context, corrosion and accidental damages are simulated and the bridge redundancy is evaluated by using three-dimensional nonlinear finite element and probabilistic system analyses. The bridge damage-redundancy-reliability interaction is also studied.
Top-and-Seat-Angle Connections and End-Plate Connections: Snug vs. Fully Pretensioned Bolts
Authors: Fleischman Robert B. , Chasten Cameron P. , Lu Le-Wu , Driscoll Jr.
Published: April 2024

The effect of partially pretensioned bolts has been examined through research conducted at the ATLSS center of Lehigh University. Extended end-plate and top-and-seat-angle connections incorporating fully pretensioned and snugtight bolts were tested. Fully pretensioned bolts were tightened to 70% of their ultimate strength (as specified by AISC), and snug bolts were tightened to between 30% and 40% of their ultimate strength." A W27x94 beam section was connected to a W14x193 column section for the tests considered. All material was 50 ksi steel, and A325 1-in. and 1 1/8 -in. diameter bolts were used for all connections. Snug-tightened end-plate connections performed essentially the same as their fully pretensioned counterparts. Snug connections were nearly as stiff as the fully pretensioned connections at moderate loads, and the ultimate strength was the same for either case. Snug-tight connections actually behaved stiffer during the course of reversal loading. Top-and-seat-angle connections were designed to resist moment by using equally large angles attached at the top and bottom beam flanges. The snug-tight connection for multiple bolt rows behaved stiffer and stronger than its fully pretensioned counterpart. Two modes of behavior are proposed for these cases. The snug-tight connection also reacted less adversely to load reversal, and its load deformation response remained linear over a larger range of loading.
Analytical Criteria for Stitch Strength of Built-Up Compression Members
Authors: Aslani Farhang , Goel Subhash C.
Published: April 2024

In the buckled configuration of a built-up compression member, shear force is developed between individual components due to secondary moments caused by P-deffect. AISC-ASD1 requires that stitches be designed such that they have adequate strength to resist the shear force developed between individual components. AISC-LRFD also has a similar requirement (see Section E4, p. 6-40). However, neither specification gives a procedure to calculate the shear force developed between individual components in a buckled configuration. This paper presents a derivation of analytical equations to calculate the shear force developed between individual components of built-up struts in buckled configuration. The equations are presented for two cases. First, for the case in which only the first buckling load is of interest. Second, for the case in which, in addition to the first buckling load, post-buckling bending is involved such as in seismic-resistant design. The proposed equations are general enough so that they are applicable to any end condition including the two extreme cases of hinged-and fixed-end conditions. The proposed equations are verified analytically and experimentally. For analytical verification, the results from the proposed equations are examined for the extreme cases of end conditions and separation between the components. For experimental verification, test results by the authors are used. The stitch strength required for some test specimens are calculated according to the proposed equations. The results are compared with actual strength provided by the stitch welds of the corresponding specimens. It was found that specimens which suffered unsymmetrical buckling and/or post-buckling behavior did not have adequate stitch strength according to the proposed equations.
Strength of Three New Types of Composite Beams
Authors: Toprac A.A.
Published: April 2024

Although composite construction is not new, having been in use in this country since the late 1930s, it owes its current popularity in building construction to relatively recent developments. Since the advantages of composite construction—reduced weight of steel, smaller live load deflection, or decreased depth of members—are most pronounced in long spans and for heavy loads, most of the early work was done in the bridge field. However, neither the original nor the revised provisions on composite construction in the specifications of the American Association of State Highway Officials (AASHO), which were written specifically for bridges, were directly applicable to building construction because of the different nature of the problems involved.
Bending Under Seated Connections
Authors: Abolitz A. Leon , Warner Marvin
Published: April 2024

The seat, or bracket, is a common type of connection in structural steel. A bracket carried by a column or beam web or, in general, by a vertical plate, throws a bending moment into the supporting plate, and if the plate is relatively thin it may be overstressed. No data about this important effect are given in the AISC Manual of Steel Construction or in readily available reference works; yet this stress may be critical and govern the design of the connection. The problem of evaluating these stresses arose in the analysis of numerous heavily loaded brackets used in the Vertical Assembly Building at Cape Kennedy, designed by Urbahn-Roberts-Seelye-Moran (URSAM). A theoretical investigation of plate bending under brackets has been carried out by both an elastic method and a plastic method. This paper presents the results of these analyses, including a rule of thumb as well as more accurate methods of computation.
Closure: Simple Equations for Effective Length Factors
Authors: Dumonteil Pierre
Published: April 2024

Closure
Design Criterion for Vibrations Due to Walking
Authors: Allen D.E. , Murray Thomas M.
Published: April 2024

A design criterion for walking vibrations of broader application than previous criteria is proposed for steel floor or footbridge structures. The criterion is based on the dynamic response of steel structures to walking forces, as well as the sensitivity of occupants to vibration motion. The criterion is applicable to structures with natural frequencies below 9 Hz, where resonance can occur with a harmonic of the step frequency, but is extended beyond 9 Hz where footstep impulse response becomes important.
Removal of Yield Stress Limitation for Composite Tubular Columns
Authors: Kenny John R. , Bruce Donald A. , Bjorhovde Reidar
Published: April 2024

Composite action between different structural materials has been utilized in bridge and building construction for a number of years. Traditionally constructed of steel and concrete, composite structures take advantage of the strength characteristics of each material. For example, a composite bridge girder utilizes the properties of steel in the tension zone and the compressive strength of the concrete in the deck. Similarly, a column made of a steel tube filled with concrete maximizes the steel strength by restraining the primary failure mode, i.e., local buckling of the tube wall, while simultaneously improving the load sharing between steel and concrete. The tube also provides confinement for the concrete, preventing early spalling and effectively raising the available strength of the material. The two materials are thus mutually beneficial. Modifying the existing strength formulas for steel columns to address the unique characteristics of composite compression members, design criteria for composite columns were developed by Furlong and others.1,2 In essence, the procedures were based on the use of a modified yield stress, radius of gyration, and modulus of elasticity for the composite cross section, in combining the contributions of the steel and the concrete. In this fashion, composite columns were given design criteria that took advantage of the combined strength of steel and concrete.
Composite Semi-Rigid Construction
Authors: Leon Roberto T.
Published: April 2024

Over the past twenty years several hundred articles on analysis and behavior of semi-rigid steel frames have appeared in the technical literature.1 This body of knowledge indicates that semi-rigid or partially restrained (PR) frames possess many economical, constructional, and technical advantages over rigid frames and frame-shear wall systems. However, it is safe to say that only a small percentage of the literature on this subject addresses design issues directly.2—5 The result is that even though semi-rigid or partial-restraint (PR) connection behavior is recognized and allowed by most specifications, very few structural engineers have made explicit use of them in design.6 In general these few designers possess what are considered advanced analysis and design tools, consisting mostly of computer programs developed inhouse. This situation is beginning to change, however, because advanced analysis techniques7,8 are beginning to be widely discussed and disseminated and public-domain and commercial programs incorporating them will soon be available. This paper describes the development of a particular type of semi-rigid construction which the author and his coworkers have developed over the past 10 years. The paper is divided into three main parts. The first part presents some important considerations on semi-rigid behavior which apply irrespective of the connection type being used. They are included here to illustrate the differences between simple, fully rigid, and partially rigid structures and to highlight their impact on limit states. The second part of the paper deals with the design of semi-rigid structures utilizing the composite action of the floor system.
Low-Cycle Variable Amplitude Fatigue Modeling of Top-and-Seat Angle Connections
Authors: Mander John B. , Chen Stuart S. , Pekcan Gokhan
Published: April 2024

A set of variable amplitude tests was performed on a commonly used type of semi-rigid connection: the top-and seat angle. Variable amplitude tests included incremental decremental and step tests to investigate the sequence effects on cyclic and low-cycle fatigue behavior for this class of beam column connection. The concept of an effective equi-amplitude plastic rotation is introduced as the characteristic measure of rotation history. It is shown that effective rotation is independent of load path when compared to companion constant amplitude test results. An energy based cumulative damage model is characterized in terms of energy-life and energy-rotation relationships. The proposed damage model is employed in fatigue damage prediction analysis and compared with the classical Miner's linear damage accumulation model coupled with the rainflow cycle counting method. The proposed energy based damage model implicitly incorporates the memory effects of the previous loading history and precludes the necessity of performing explicit cycle counting, and it is easily implemented into non-linear time-history analysis for seismic design and evaluation purposes.
Block Shear Tests in High-Strength Steel Angles
Authors: Gross Jeremy M. , Orbison James G. , Ziemian Ronald D.
Published: April 2024

Full-scale tests of A588 Grade 50 single-angle tension members, with bolted connections designed to fail in block shear, were conducted. Maximum loads were compared with those predicted by the current American Institute of Steel Construction (AISC) Load and Resistance Factor Design (LRFD) and Allowable Stress Design (ASD) Specifications. It was found that both methods were very accurate in predicting the experimental load capacities. However, the procedure provided in the first edition of the LRFD Specification is shown to consistently, and in some cases significantly, overestimate the nominal failure loads. That procedure is adequate, however, when the resistance factor is applied and design resistance is compared.
Optimum Cost Design of Partially Composite Steel Beams Using LRFD
Authors: Bhatti M. Asghar
Published: April 2024

Design of composite steel beams is a trial and error process. The procedure recommended by the Manual of Steel Construction, Load and Resistance Factor Design (LRFD)1 is to first assume a depth for the steel beam and then compute a trial beam size. For a full composite action the number of shear studs is chosen with the assumption that the plastic neutral axis (PNA) is in the concrete slab. For partially composite design the number of shear studs is chosen rather arbitrarily by the designer. The flexural capacity of the composite section is then computed based on the ultimate stress distribution over the cross section. If the capacity is less than the required, the design is revised in one of several ways: by increasing the number of shear studs, by increasing the beam depth, or by choosing a heavier section. These decisions must be based on the designers judgment without any available guidelines. Shear and deflection considerations may force additional changes in the design. The resulting design is usually not the minimum cost design and at best is a feasible design. Several iterations of this entire process may be necessary if the goal is to minimize the cost. The optimum design can directly be obtained by formulating the problem as a nonlinear optimization problem. However conventional methods for solution of these nonlinear programming problems are iterative and require large computer resources.
Specifying Bolt Length for High-Strength Bolts
Authors: Carter Charles J.
Published: April 2024

Two tables that are useful in determining the proper bolt length for high-strength bolts are provided in the AISC Manual of Steel Construction: Table 8-2, which includes constants to be added to the grip and washer thickness (RCSC Specification Table C2 is the basis for these constants) and a table in Figure 8-3, which indicates the outer-ply thickness required to exclude the threads from the faying surface of the connection. While it is a simple operation to select bolt lengths using these tables, the repetitive calculation becomes somewhat tedious and could be simplified. In this paper, a design aid is presented for the selection of high-strength bolt lengths for bearing (snug-tightened and fully tensioned) and slip-critical connections. Nominal bolt lengths are tabulated based upon the grip in ASTM A325 and A490 bolts with zero, one, or two 5/32-in.-thick ASTM F436 flat washer(s) and an ASTM A563 nut; bevelled washers are not considered in this paper. Additionally, the outer-ply thickness required when it is desired to exclude the threads from the shear plane is tabulated.
Load and Resistance Factor Design and Analysis of Stepped Crane Columns in Industrial Buildings
Authors: MacCrimmon Robert A. , Kennedy D.J.L.
Published: April 2024

Load and Resistance Factor Design (LRFD), generally known as Limit States Design (LSD) outside of the United States of America, is replacing working stress design (WSD) worldwide for good reason. Not only does it provide much more uniform reliability with load and resistance factors based on the statistical variation of the relevant variables but also, by implicitly eliminating unnecessary conservatism at the same time, it can effect economies as well. A major advantage of LRFD over working stress design is inherent in the fact that the ultimate limit states, those associated with failure of all or part of the structure, are checked against factored load combinations, which are chosen to have the required low probability of being exceeded. This means that both the second-order geometric effects, resulting from the deformation of the structure and the non-linear effects due to material behavior can be taken into account in a straightforward manner at the load levels associated with failure. The load deformation response can be determined to whatever load level is desired. Herein this level is taken as that approaching the formation of the first plastic hinge. In working stress design the response is assumed to be linearly elastic but is not established beyond the working load level. Second-order effects cannot be included directly. The differences in the two analyses are demonstrated by White and Hajjar who show responses for various types of analyses.
Steel Built-up Girders with Trapezoidally Corrugated Webs
Authors: Elgaaly Mohamed , Seshadri Anand
Published: April 2024

The availability of high strength steels requires innovative designs, such as the use of corrugated webs, for efficient use of these steels. Economical design of steel girders normally requires thin webs; the conventional welding of stiffeners to allow the use of thin webs has two disadvantages. The first is high fabrication cost, and the second is a possible reduced life due to fatigue cracking which may initiate at the stiffeners weld. The use of corrugated plates in lieu of flat stiffened plates in the web of a girder can eliminate both disadvantages. With the advances in welding technology, automatic welding of corrugated webs can benefit from the joint tracking technology, and the web needs to be welded to the flanges only from one side. As a result, girders with corrugated webs can be very economical when compared with conventionally stiffened girders. Furthermore, the use of corrugated webs will increase the lateral stiffness of the girder, thus minimize lateral-torsional buckling bracing requirements, particularly during construction, and the use of corrugated webs in composite construction will minimize cracking of the slab.
Design Tables for Top- and Seat-Angle with Double Web-Angle Connections
Authors: Kim Yosuk , Chen Wai-Fah
Published: April 2024

This paper provides a set of design tables, based on the AISC/LRFD Specification (1994), for the selection of top and seat-angle with double web-angle connections given beam sections and applied loads. These tables enable the engineer to rapidly select proper angle sizes and configurations as well as determine the moment-rotation curve for the connection. Design procedures and a comprehensive case study are also presented.
Beam-Column Base Plate Design—LRFD Method
Authors: Drake Richard M. , Elkin Sharon J.
Published: April 2024

It is common design practice to design a building or structure beam-column with a moment-resisting or fixed base. Therefore the base plate and anchor rods must be capable of transferring shear loads, axial loads, and bending moments to the supporting foundation. Typically, these beam-column base plates have been designed and/or analyzed by using service loads or by approximating the stress relationship assuming the compression bearing location.The authors present another approach, using factored loads directly in a method consistent with the equations of static equilibrium and the LRFD Specification. The moment-resisting base plate must have design strengths in excess of the required strengths, flexural (MM), axial (Pu), and shear (Vu) for all load combinations.
Design of Welded Steel Moment Connections Using Truss Analogy
Authors: Goel Subhash C. , Lee Kyoung-Hyeog , Stojadinovic Bozidar
Published: April 2024

A new design procedure for fully-restrained welded beamto- column moment connections is presented in this paper. This procedure is based on truss analogy approach developed by the authors (Goel, Stojadinovic, and Lee 1996 and 1997). The truss analogy approach accounts for boundary effects occurring in the connection because the configuration of the connection restrains the deformation of the connected elements (Lee, Goel, and Stojadinovic, 1997). The resulting stress distribution, or "load path" can be modeled using a truss. The diagonals of the truss model represent the resultants of normal and shear stresses in the web of the beam that go through the regions near the beam flange welds. A new connection design is also presented in this paper. This connection configuration is designed by following the load path model using truss analogy. The idea behind the new connection design is to indirectly connect the beam to the column. The connection elements are to be placed near the top and bottom flanges of the beam to handle the forces in the truss chords and diagonals. Each flange connection comprises a horizontal flange plate and a set of vertical ribs designed to transfer the force in the truss members. The middle portion of the beam web need not be connected to the column except for field erection purposes because it is virtually stress-free. The combination of the new design procedure and new connection design is intended to ensure adequate ductility of the moment-resisting frame. To achieve this, it is desirable that plastic hinges form in the beams at a safe distance away from the beam-to-column connections.
The Ultimate Strength of Symmetric Beam Bolted Splices (Q2-2001)
Authors: Sheikh-Ibrahim Firas I. , Frank Karl H.
Published: April 2024

A beam splice must be designed to transfer the shear and moment of the beam at the location of the splice. However, the actual force distribution between the web and flange splices is unknown. Currently, design methods for beam splices are conflicting with one another. These methods result in a different number of bolts, and are difficult to interpret, especially when designing unsymmetric splices. This paper presents a summary of an analytical and experimental research program performed on unsymmetric beam bolted splices. Simplified recommendations are presented for the force distribution between the web and flange splices. The validity of these recommendations is verified by the experimental program. To demonstrate the application of the design recommendations, three design examples are presented.
Restrained Fire Resistance Ratings in Structural Steel Buildings
Authors: Gewain Richard G. , Troup Emile W.J.
Published: April 2024

Unique to North America is a dual classification for fire resistance of supporting members in floor and roof system in buildings, depending on whether these members are restrained or unrestrained at their ends. When this dual classification was first introduced in 1970, the ASTM E-5 Fire Test Committee clearly recognized that architects, engineers and building code administrators not familiar with the nuances of structural fire testing would have difficulty in properly applying restrained and unrestrained fire ratings in the design of real buildings. As a result, general guidance was added to ASTM E119 Standard Fire Test in the form of Appendix X3, reproduced in its entirety herein as Appendix A, with the permission of ASTM. The purpose of this paper is to eliminate the confusion that has persisted in some regions of the USA concerning the proper application of restrained and unrestrained fire resistance ratings for steel beam floor and roof assemblies. The ASTM E119 Standard Fire Test and fire test procedures are discussed. Current building code requirements are summarized and results of extensive fire research and analysis of steel beam and concrete floor constructions are reviewed. Recent studies that provide greater understanding of how steel beam and concrete floor systems endure the effects of uncontrolled fire events in real buildings are briefly referenced. The information in this paper will enable architects and engineers to satisfy code provisions requiring justification where fire resistance for steel beam floor and roof systems are based on restrained assembly ratings.
Ponding of Two-Way Roof Systems
Authors: Marino Frank J.
Published: April 2024

Several papers have been published analyzing roof beams subject to ponding. However, the scope of these papers has been limited to the one-directional action of beams. That is, the flexural members are considered supported by unyielding knife edges with no consideration given to surface deflection transverse to the beam span under study. The effect of interaction between members in a roof framing system can be considerable and should not be neglected. The present AISC Specification is cognizant of the ponding problem. Chinn points out that the Specification provision is arbitrary in nature and could be overly conservative. It is interesting to note here that in all the cases of collapse attributed to the ponding phenomenon that the author has reviewed, the members involved did violate the present Specification provision. However, the provision may actually be unconservative for very large spans. The purpose of this paper is to analyze the ponding of a roof system, accounting for the interaction of members and to develop a design aid suitable for office use. A restriction imposed on the analysis is that the structural system must consist essentially of two-way framing (i.e., main girders or primary members and secondary sub-members spanning perpendicular to the girders) with the deck contributing negligible deflection to the system. However, if in the absence of other sub-members the deck spans a substantial distance between main members, it should be treated as the secondary system.
Cyclic Behavior of Steel Moment-Resisting Connections Reinforced by Alternative Column Stiffener Details I
Authors: Lee Daeyong , Cotton Sean C. , Hajjar Jerome F. , Dexter Robert J. , Ye Yanqun
Published: April 2024

Experimental and corroborating computational research was performed to reassess the design and detailing of column reinforcement (in other words, continuity plates and doubler plates) according to U.S. specifications for both seismic and non-seismic design and to explore economical alternative stiffener details. The performance of six full-scale girder-to-column cruciform specimens that use the Welded Unreinforced Flange-Welded Web (WUF-W) connection detail was evaluated. The effects on the cyclic behavior of three different doubler plate details, including a back-beveled fillet-welded detail, a square-cut fillet-welded detail, and a box (offset) detail, were investigated. In addition, the performance of a continuity plate approximately half the thickness of the girder flange fillet-welded to both the column flanges and doubler plates was investigated. Current local flange bending and local web yielding design criteria were evaluated and the applicability of the suggested alternative column stiffener details was verified. A companion paper outlines findings with respect to panel zone behavior and design for seismic applications.
Fatigue Life Prediction and Variability of New and Existing Welded CHS Y-Joints
Authors: Foley Christopher M , Peronto John L. , Fournelle Raymond A.
Published: April 2024

An experimental program was undertaken to quantify fatigue life variability of the ET fatigue detail category for welded circular hollow shape (CHS) connections commonly found in sign support structures. The program included fatigue testing of existing and fabricated Y-joint specimens composed of CHS, detailed material characterization, and comparison of experimentally determined fatigue lives with a variety of analytical methodologies. The results of the research effort serve as the foundation for quantifying the expected service life for overhead sign support structures in relation to the fatigue limit state of the welded connections. The data has been used as the basis for a procedure for predicting the service lives of full-span overhead sign support trusses.