## Basic Column Strength

To determine a basic column strength, certain conditions may be assumed for the ideal column 6.7 . With regard to material, it may be assumed (1) there are the same compressive stress-strain properties throughout the section (2) no initial internal stresses exist such as those due to cooling after rolling and those due to welding. Regarding shape and end conditions, it may be assumed (3) the column is perfectly straight and prismatic (4) the load resultant acts through the centroidal axis of...

## Nominal Moment Strength Of Fully Composite Sections

The nominal strength M of a composite section having its slab in compression (positive moment) depends on the yield stress and section properties (including sleuderness A - ., for the web) for the steel beam, the concrete slab strength and the strength of shear connectors providing the interface shear transfer between slab and beam. The nominal strength (commonly called ultimate strength) concepts were first applied to design practice as recommended by the ASCF-ACI Joint Committee on Composite...

## Load and Resistance Factor Design Maximum

Equation 11.3.9 when rounded becomes h- 'FV (F 16.5) which is the LRFD-Appendix Gl general limitation (Fv in ksi). In the presence of transverse softeners, higher ratios are permitted. Based on the recommendations of the ASCE-AASHO Joint Committee, Subcommittee 1 on Hv-brid Girder Design 11.10 . LRFD-Appendix G1 gives the maximum hft,x. as when stiffener spacing a to web depth h does not exceed 1.5. Values for Eqs. 11.3.10 and 11.3.11 are given in Table 11.3.1.

## Framed Structures

Most typical building construction is in this category. The multistory building usually consists of beams and columns, either rigidly connected or having simple end connec- tions along with diagonal bracing to provide stability. Even though a multistory building is three-dimensional, it usually is designed to be much stiffer in one direction than the other thus it may reasonably be treated as a series of plane frames. However, if the framing is such that the behavior of the members in one plane...

## Size And Length Limitations For Fillet Welds 21

Figure 5.11.1 Effect of thickness on cooling rate. whereas the thinner plate is essentially limited to a horizontal dissipation. In other words, the thicker the plate, the faster heat is removed from the welding area, thereby lowering the temperature in the region of the weld. Since a minimum temperature is required to cause the base metal to become molten, it is therefore necessary to provide as a minimum, a weld of sufficient size (and heat content) to prevent the plate from removing the heat...

## W18 X

Repeat Prob. 8.10, considering the ends torsionally fixed. 8.12. Repeat Prob. 8.8, with the load applied in the plane of the y-axis of a channel, C15X50. 8.13. For the case (or cases) assigned by the instructor, select the lightest W14 section, using the (3 modified flexure analogy approach, to carry a concentrated load W at midspan, in addition to the weight of the beam. The ends of the simply supported span are assumed to have torsional simple support. Check the stresses in the section...

## Selected References

Standard Specification for Structural Steel (A36 A36M-94). Philadelphia, PA American Society for Testing and Materials, 1994. 2.2. ASTM. Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated Welded and Seamless (A53-93a). Philadelphia, PA American Society for Testing and Materials, 1993. 2.3. ASTM. Standard Specification for High-Strength Low-Alloy Structural Steel (A242 A242M-93). Philadelphia, PA American Society for Testing and Materials, 1993. 2.4. ASTM....

## Triangular Bracket Plates

When the Miflener ten- a bracket is cut into a triangular shape, as in Fig. 13.4.3b. the plate behaves in a different manner than when the free edge is parallel to the direction of applied load in the region where the greatest stress occurs, as in Fig. 13.4,5,. The triangular bracket plate arrangement and notation are shown in Fig. 13.5,1. The behavior of triangular bracket plates has been studied analytically by Salmon .13.45 and experimentally by Salmon, Buettncr. and 0'.Sheridan 13,46) and...

## Composite Flexural Members Containing Formed Steel Deck

Composite llexural members may be made using formed steel deck, as shown in Fig. 16.E2. The formed metal deck may be placed perpendicular to or parallel with the supporting beam. Furthermore, the beam may actually be an open web joist. Typically, the deck plate varies in thickness from 22 ga. (0.0336 in., 0.853 mm) to 12 ga, (0.1084 in 2.75 mm). The deck rib height typically is . 2. and 3 in. for spans oE say. 8. 10, and 15 ft. As shown in Fig, 16,1.2, the thickness of the concrete slab above...

## Bearing Criterion

In order to bring bearing stiffener plates tight against the flanges, one corner of each stiffener plate must be cut off so as to clear the flange-to-web fillet weld. The remaining area of direct bearing is less than the gross area of the stiffener plates. The strength in bearing under LRFD-J8.1 or the service load stress in bearing under ASD-J8.1 must be satisfactory. Load and Resistance Factor Design. The bearing requirement of LRFD-J8 is Rn nominal bearing strength 1.8FyAph (11.12.8) Apb...

## Load And Resistance Factor Design

The concepts relating to the nominal moment strength M* have been presented in Chapters 7 and 9, and reviewed in Sec. I l .2. Complexity in design arises using M, and L, expressed by Eqs. 9.6.5 and 9.6.6. respectively, for plate girders. For rolled beams, not only are the values of M, and L, available in the LRFD Manual but also all of the properties, including the torsion properties, are readily available. For plate girders all of the properties must be computed for each girder. Thus, while...

## Combined Bending And Axial Load

12.15 DESIGN PROCEDURES ALLOWABLE STRESS DESIGN To aid in selection of a beam-column section, it is usually advantageous to convert, in an approximate way, the resulting bending moment into an equivalent axial compression load and then to make use of column tables, as was done in Sec. 12.12 for LRFD. Occasionally, conversion of the axial load into equivalent moment will be helpful. The stability interaction equation, Eq. 12.14.3, may be written P M ( C l AgFa FhS - fjfj Multiplying by Ag Fa...

## Effective Laterally Unbraced Length

Design equations, such as those of LRFD and ASD-F1, are based on the assumption of torsional simple support (see Figs. 8.5.4 and 8.7.2) at the ends of the unbraced segment. This means that for torsional behavior only the effective laterally unbraced length KLh equals the actual laterally unbraced length Lh that is. the effective length factor K - 1.0. Nearly any type of lateral brace or end connection will prevent rotation (that is. keep the angle of twist equal to zero see Fig. 9.4.1c) about...

## Biaxial Bending Of Symmetric Sections

Flexural stresses on sections with at least one axis of symmetry and loaded through the centroid may be computed using Eq. 7.10.19, which when modified to give where Sx IJ(d 2) and Sv I, b 2) are the section modulus values. The nominal strength of a section subject to biaxial bending is not readily determined. Such strength will certainly depend on the proportions of the section and the relative magnitudes of the applied moments Mx and My. The use of an interaction equation such as used for...

## Holes In Beams

For tension members the effect of fastener holes has been discussed in Chapter 3, where holes are deducted and net section is used. For compression members, since the fasteners occupy most of the space in the hole, the fasteners are assumed in design to completely fill the holes and a deduction for holes is not made. When the nominal strength Mn reaches the plastic moment Mp, certainly tension flange holes reduce that strength however, there will be a shift in neutral axis associated with a...

## Hybrid Composite Girders

The general discussion of the hybrid plate girder appears in Sec. 11.7. The hybrid girder is one that has either the tension flange or both flanges of the steel section made with a higher strength grade of steel than used for the web. There are, particular economic advantages to the hybrid girder in composite construction where the concrete slab, provides a large compression capacity, The neutral axis will lie near the compression face of the composite section, causing the higher stressed...

## Service Load Stresses With And Without Shoring

The actual stresses lust result due to a given loading on a composite member arc dependent upon the maimer of construction. The simplest construction occurs when the steel beams are placed first and used to support the concrete slab formwork. In this case the steel beam acting noncom-positely (i,e,. by itself ) supports the weight of the forms, the wet concrete, and its own weight. Once forms are removed and concrete has cured, the section will act compos itely to resist all dead and live loads...

## Allowable Stress Design

The safety requirement for axially loaded columns in Allowable Stress Design (ASD) according to ASD-E2 may be stated where fa service load compression stress P Ag P service load axial compression force Ag gross cross-sectional area of column Fa allowable stress at service load Eqs. 6.7.9 or 6.7.10 Equations 6.7.9 and 6.7.10 are used for typical rolled W sections satisfying the local buckling limitations on width thickness ratios for plate compression elements given in ASD-B5.1. Table 6.8.1...

## Types Of Joints

The type of joint depends on factors such as the size and shape of the members coming into the joint, the type of loading, the amount of joint area available for welding, and the relative costs for various types of welds. There are five basic types of welded joints, although many variations and combinations are found in practice. The five basic types are the butt, lap, tee, corner, and edge joints, as shown in Fig. 5.4.1. The butt joint is used mainly to join the ends of flat plates of the same...

## Compression Members 276 Parti Columns 276

6.2 Euler Elastic Buckling and Historical Background 276 6.6 Development of Column Strength Curves Including Residual Stress 287 6.7 Structural Stability Research Council (SSRC) Strength Curves 295 6.8 Load and Resistance Factor Design 300 6.10 Load and Resistance Factor Design of Rolled Shapes (W, S, and M) Subject to Axial Compression 311 6.1 1 Allowable Stress Design 317 6.13 Design of Latticed Members 321 6.14 Introduction to Stability of Plates 327 6.15 Strength of Plates under Uniform...

## Loads Applied Eccentric To The Plane Of Welds

When an applied load is eccentric to the plane of the weld configuration, as in Fig. 5.19.1, the strength method of analysis may still be used as long as the plane of the welds is rigid. The weld plane is rigid in Fig. 5.19.1 because the welds are on each Figure 5.19.1 Welds in shear and bending. Figure 5.19.1 Welds in shear and bending. side of a plate i.e there is sufficient rigidity between the two lines of wreld such that there will be no bending of the material being welded in the plane of...

## Basic Processes

Welding is the process of joining materials (usually metals) by heating them to suitable temperatures such that the materials coalesce into one material. There may or may not be pressure, and there may or may not be filler material applied. Arc welding is the general term for the many processes that use electrical energy in the form of an electric arc to generate the heat necessary for welding. This section treats those processes used in arc welding carbon and low-alloy steel for buildings and...

## Muitiaxial Stress Induced by Welding

In general, welding creates a built-in restraint that gives rise to biaxial and triaxial stress and strain conditions, which result in brittle behavior. To illustrate, consider the loaded simply supported beam of Fig. 2.9.3, which in turn supports a plate in tension. Due to flexure, the bottom flange of the beam is in tension therefore, the stress at point A is uniaxial tension (neglecting the small effects of beam width and attachment of flange to web). Connecting the tension plate with angles...

## Factors Affecting The Quality Of Welded Connections

Obtaining a satisfactory welded connection requires the combination of many individual skills, beginning with the actual design of the weld and ending with the welding operation. The structural engineer needs to be aware of the factors that affect the quality of a weld and design the connections accordingly. Proper Electrodes, Welding Apparatus, and Procedures After the proper electrode material is specified to match the strength of the steel in the pieces being joined (see Sec. 5.13), the...

## Vertical Flange Buckling Limit State

The maximum limit on the web slenderness h tu. is based on the stiffness needed in the plane of the web to prevent the compression flange from buckling vertically (Fig. 11,3. lc). Note that h, the clear unsupported height of the web in a rolled section, is the depth h of the web plate in a welded I-shaped section. Furthermore, some flexural stiffness is needed from the web along the flange-to-web connection to preclude torsional buckling of the flange (Fig. 11.3.1b). Fiange aas KUkp ndeMh when...

## Comparison of LRFD with ASD for Tension Members

The comparison of safety obtained for tension members designed by the two AISC methods is indicative of the general result expected. Direct comparisons are more difficult in design of other types of members because the nominal strengths R are not necessarily the same in the two methods. For tension members acted upon by gravity dead and live loads, the resistance factor < j> 0.90, and using Eq. 1.8.3 gives for LRFD 1.2 D + 1.61 0.90 R 1.8.3 In ASD the factor of safety FS 1.67 for axial...

## Jjl

(a) Cross-section (b ) Elevation at end of span Figure 11.1.2 Typical components of a welded plate girder. Where practically all riveted girders were composed of plate and angle components having the same material yield strength, the tendency now with welded girders is to combine materials of different strength. By changing materials at various locations along the span so that higher strength materials are available at locations of high moment and or shear, or by using different strength...

## Types Of Connections

Steel construction is categorized by LRFD-A2.2 and ASD-A2.2 into various 'Types depending on the amount of restraint developed by the connections. Three types are identified Fully Restrained (also called Rigid Frame, or Continuous Frame). This situation occurs when full continuity is provided at the connection so that original angles between intersecting members are maintained essentially constant during loading of the structure i.e., with rotational restraint on the order of 90 or more of that...

## Compression Members Example 6104

Design column A of the unbraced frame of Fig. 6.10.4 as an axially loaded compression member carrying a dead load of 55 kips and a live load of 220 kips using A36 steel. In the plane perpendicular to the frame the system is braced, with supports at top and bottom of a 21-ft height. PH 1.2D + 1.6L 1.2(55) + 1.6(220) 418 kips (b) Select a preliminary size as a basis for evaluating the effective length factors K. While it is rare that a frame member would be designed as axially loaded, it may...

## Introduction And Historical Development

Plate girders, showing welded stiffeners in place, rocker bearings for vertical supports at the pier, transverse cross bracing between girders, and hinges to provide a simple support for the spans to the right of the hinges. (Photo by C. G. Salmon) Plate girders, showing welded stiffeners in place, rocker bearings for vertical supports at the pier, transverse cross bracing between girders, and hinges to provide a simple support for the spans to the right of the hinges. (Photo by C. G. Salmon)...

## Introduction And Historical Development 189

Thomas Fletcher 5.1 in 1887 used a blowpipe, burning hydrogen and oxygen and showed that he could successfully cut or melt metal. In 1901 -1903 Fouche and Picard developed torches that could be used with acetylene and, thus, the era of oxyacetylene welding and cutting began. The period between 1903 and 1918 saw the use of welding primarily as a method of repair, the greatest impetus occurring during World War I (1914-1918). Welding techniques proved to be especially adapted to repairing ships...

## Problems

All problems are to be done according to the ALSC Load and Resistance Factor Design or Allowable Stress Design, as indicated by the instructor. The requirement of W section is intended to include W. S, and M sections, All given loads are service loads unless otherwise indicated. If needed, assume service loads are 2 3 I factored loads unless otherwise indicated. Assume lateral support consists of transnational restraint but not moment i rotational) restraint, unless otherwise indicated. Assume...

## Analogy Between Torsion And Plane Bending

Because the differential equation solution is time consuming, and really suited only for analysis, design of a beam to include torsion is most conveniently done by making the analogy between torsion and ordinary bending. Consider that the applied torsional moment T of Fig. 8.6.1 can be converted into a couple PH times h. The force PH can then be treated as a lateral load acting on the flange of a beam. The substitute system will have constant shear over one-half the span, a diagram as given in...

## Exx

Fu tensile strength of base material Fexx tensile strength of electrode material 70 ksi for E70 electrodes Sections b-b and c-c will not be critical since two lines of weld transfer load across two sections, as shown in the equation for maximum effective weld size across those sections, lt M0.707 0.60FHXX lt M0.6Fji2 Considering the four fillet welds of Fig. 5.14.1b, sections d-d and e e are the same as section a a therefore, Eq. 5.14.9 applies. On sections - and g-g four fillet welds transfer...

## Info

F i , 58 0,400 i Cheek o - 0.707 - 0.707 n 2 lt liL x- 0.23 in. OK Mm a 2-in. from Table 5.10,1 Hor ,. 0.785 mo i.Oe hi. F70 fillet weld along length 4 gt both sides of girder vvebi. lt e Determine libel weld si e along length IK'. The connection of the ccd uiitn vseb to the bean's fkmge must cany the lorce re suiting from llevurc ami axial load combined with the shear. At the most highly stressed location there vol be tension and shear acting simultaneously on the weld. A...

## Torsion 424

8.2 Pure Torsion of Homogeneous Sections 425 8.3 Shear Stresses Due to Bending of Thin-Wall Open Cross-Sections 428 8.5 Torsional Stresses in LShaped Steel Sections 432 8.6 Analogy Between Torsion and Plane Bending 443 8.7 Practical Situations of Torsional Loading 447 8.8 Load and Resistance Factor Design for Torsion Laterally Stable Beams 452 8.9 Allowable Stress Design for Torsion Laterally Stable Beams 458 8.10 Torsion in Closed Thin-Wall Sections 458 8.11 Torsion in Sections with Open and...

## Torsion In Sections With Open And Closed Parts

Generally this problem is treated by combining the principles discussed separately for open and closed parts. The procedure to be used for determining resisting moment, stiffness, and shear center location for such sections is presented with examples by Chu and Longinow 8.33 , The following is a summary of pertinent equations Total resisting moment is where J X bt3 for open parts only. In addition, each of the closed cells must satisfy Eq. 8.10.14

## Example 3102

Design sag rods to support the purlins of the industrial building roof of Fig. 3.10.2. Sag rods are spaced at the third points between roof trusses, which are spaced 24 ft apart. Use 20 psf snow load, A36 steel, and AISC LRFD Specification. Solution, a Loads. Assume cold-formed steel roofing is used, weighing 3 psf, and that the purlins have already been designed. Their weight may be approximated as a 3.5 psf roof load. Snow load customarily is prescribed as having an intensity given in pounds...

## A490sc

For any of the cases solved in Prob. 4.1. determine the factor of safety against slip at service load. Do you expect slip to occur at service load If bolt strength had controlled would slip have been expected at service load 4.3. Determine the service load capacity T for the butt splice of Prob. 3.15 when Ji 52 2 in. and A325 bolts are used with no threads in the shear planes. Specify the end distances required and evaluate whether or not the given stagger of 2 in. is sufficient. If the 2...

## Historical Background Of Highstrength Bolts

The first experiments indicating the possibility of using high-strength bolts in steel-framed construction were reported by Batho and Bateman 4.1 in 1934. They concluded that bolts with a minimum yield strength of 54 ksi 370 MPa could be relied on to prevent slip between the connected parts. Follow-up tests by Wilson and Thomas 4.2 substantiated the earlier work by reporting that high-strength bolts smaller in diameter than the holes in which they were inserted had fatigue strengths equal to...

## Semi Rigid Connections

Wind Stresses in Semi-Rigid Connections of Steel Framework Transactions. ASCL. 115 i 10 gt 0 u 3S2 402. 13.6, Robert A. lieehtman and Bruce G, Johnston. Riveted Sard Rigid Beam-m- Cohami Building Connections, Progress Report Number F Chicago. IF American Institute of Steel Construction. November 047 pp.h 13.7. I,eo Schenker, Charles G. Salmon, and Bruce G. Johnston. Structural Steel Concatunx, Armed Forces Special Weapons Project. Report No, 752. Engineering Research...

## Practical Situations Of Torsional Loading

There are relatively few occasions in actual practice where the torsional load can cause significant twisting, and frequently these situations arise during construction. In most building construction the members are laterally restrained by attachments along the length of the member and therefore they are not free to twist. Even though torsional loading exists, it may be self-limiting because the rotation cannot exceed the end slope of the transverse attached members. Torsion exists on spandrel...

## Bearing Stiffener Design

Concentrated loads, such as at unframed end reactions, must be earned by stiffeners placed in pairs. Whenever concentrated loads, such as end reactions or columns supported by plate girders, exceed the local web yielding, web crippling, or side sway web buckling strengths, bearing stiffeners must be provided. Local web yielding and web crippling were discussed in Sec. 7.8 since they are also of concern on rolled beams. Local web yielding formerly called web crippling is provided for in LRFD and...

## Example 1061

Examine the effect of a shear splice at the point of contraflexure in the 40-ft span of the two-span continuous beam of Example 10.3.1. A36 steel. a Full dead load plus live load. If full continuity is maintained, partial loading in some spans to account for live load in various locations is unnecessary. Note that the moment Mp 445 ft-kips see Fig. 10.6.la can develop even when the adjacent span has a reduced load. In other words, each span may be treated separately, as long as continuity...

## W12x96 A36

P - 40 kips dead load 60 kips live load 12.6. Determine the service axial load P which the W12X45 may be permitted to carry. Lateral support is provided at ends and at midspan. Compare for A36 and A572 Grade 50 steels. 14 0.2 kips ft dead load 0.5 kips ft live load 12.7. Select the lightest W14 section to carry a service load P as shown in the accompanying figure, with an eccentricity e 12 in. with respect to the strong axis. Assume the member is part of a braced system, and conservatively...

## F7xx

Referring to Sec. 5.11, LRFD-J2.2b gives the following limits Maximum size in. Minimum size 5 in. Use -in. fillet weld, since that is about the maximum size that can be made in one pass by the SAW process. Since the fillet weld exceeds in., LRFD-J2.2a states that the effective throat te equals the theoretical throat 0.707a plus 0.11 in. From Table 5.13.1, use F7XX-EXXX flux electrode combination. The design strength of -in. fillet weld per inch of length, according to Eq. 5.14.6, is...

## Jfl

11111 lt r 28'-0 ---- peril T ' lt a Vertical support b Torsional support Figure 8.8.1 Conditions for Example 8.8.1. Solution a Compute factored loads eccentrically applied. w 1.2 0.4 1.6 1.5 - 2.88 kips ft b Compute factored moment M v. Estimating the beam weight as 0.13 kips ft, the moment M x is Ml X wL2 2.88 1.2 0.13 28 2 298 ft-kips c Consider the torsion effect. The factored uniformly distributed torsional moment is Consider mjh as the uniformly distributed lateral load acting on one...

## Example 4111

Investigate the tension member connection of Example 4.8.1 Fig. 4.8.1 to carry a total service load of 75 kips. The connection is a bearing-type connection, with threads excluded from the shear planes, using in.-diam A325 bolts in standard holes. The plates are A572 Grade 50 steel. Use the AISC ASD Specification. a Tension member capacity. The areas as computed in Example 4.8.1 are A A 2.50 sq in. A,, 3.75 sq in. fa j - 20 ksi lt 0.60Fy 30 ksi OK

## C 199

Table value 4 gt Pn CCXDL 1.99 1.0 4 14 111 kips where Cl coefficient for electrode Electrode used 70 D number of s of an inch in weld size L length of vertical weld in. Figure 5.17.4 Loading for Example 5.17.2. 5.18 ECCENTRIC SHEAR CONNECTIONS ELASTIC VECTOR ANALYSIS 251 c Summary. Compare the values of the design strength lt j gt Pn. 1. Strength analysis Pn after completing analysis 4 gt Pn 0.75 149 112 kips lt pP 111 kips d Compute the safe service load P using the factored gravity load...

## Traditional Elastic Vector Analysis

For many years eccentrically loaded fastener groups have been analyzed by considering the fastener group areas as an elastic cross-section subjected to direct shear and torsion. The stresses resulting are nominal in the sense that they have stress units say, psi and provide a guide to safety but are not real stresses because the service loads are actually carried by friction. This elastic analysis method has been used because it makes use of simple mechanics of materials concepts and has been...

## Longitudinal Web Stiffeners

Longitudinal stiffeners, as shown in Fig. 11.13.1, can increase the bending and shear strengths of a plate girder. In general, they are not as effective as transverse stiffeners however, they are frequently desired on highway bridge girders for esthetic reasons. Studies of longitudinal stiffener effectiveness, as related to stiffener size and location, have been made by Cooper 11.18, 11.19 and others at Lehigh University. These studies and others are summarized in the SSRC Guide 6.8, pp....

## Example 5192

Determine the length L required to carry the load indicated in Fig. 5.19.4, when 15 of the load is live load and 25 is dead load. The weld to be used is - -in. E70 fillet weld. Use AISC Load and Resistance Factor Design. Pu 1.2 0.25 40 1.6 0.75 40 - 60 kips b Estimate length of weld L required by using Eq. 5.19.2 lt f gt Rnw 0.75 a 0.707 0.60 70 22.3 kips in. 22.3 5 16 6.96 kips in. Mu 60 4 240 in.-kips per 2 lines of weld A reduced value of lt f gt R w has been used to account for the direct...

## Breitie Gilbert

For concrete-encased structural steel F K 29,000 J- 0.2 j rm r, gt 0.34,, , 16.2. Gottfried Brendel. Strength of the Compression Slab of T-Beams Subject to Simple Bending ' .4 7 Journai Proceedings, 6.1, January 1964. 57-76. 16.3. Conrad R Heins and Horn Ming Fan. Effective Composite Beam Width at Ultimate Load, Journai of the Structural Division, ASCE. .102, ST1 1 November 1978o 2163-2179. 16.4. Cesar R Vallenilla and Reidar Bjorhovde. Elective Width Criteria for Composite Beams Engineering...

## Shear Stresses Due To Bending Of Thinwall Open Crosssections

Before treating the computation of stresses due to torsion of thin-wall open sections restrained from warping, a review of shear stress resulting from general flexure will be developed. Recognition of a torsion situation precedes concern about calculation of resulting stresses. Extensive treatment of thin-wall members of open cross-section is given by Timoshenko 8.11 . Referring to the general thin-wall section of Fig. 8.3.1, where x and y are centroidal axes, consider equilibrium of the...

## Nominal Strength Of Welds

Since welds must transmit the entire load from one member to another, welds must be sized accordingly and be formed from the correct electrode material. For design purposes fillet welds are assumed to transmit loads through shear stress on the effective area no matter how the fillets are oriented on the structural connection. Groove welds transmit loads exactly as in the pieces they join. The electrode material used in welds should have properties of the base material. When properties are...

## Highway Live Loads

Highway vehicle loading in the United States has been standardized by the American Association of State Highway and Transportation Officials AASHTO 1.3 into standard truck loads and lane loads that approximate a series of trucks. There are two systems, designated H and HS. that are identified by the number of axles per truck. The H system has two axles, whereas the HS system has three axles per truck. There are several classes of loading however, the usual ones are known as H20 and HS20, shown...

## Fatigue Strength

Repeated loading and unloading, primarily in tension, may eventually result in failure even if the yield stress is never exceeded. The term fatigue means failure under cyclic loading. It is a progressive failure, the final stage of which is unstable crack propagation. The fatigue strength is governed by three variables 1 the number of cycles of loading, 2 the range of service load stress the difference between the maximum and minimum stress , and 3 the initial size of a flaw. A flaw is a...

## Causes Of Rivet Obsolescence

Riveting is a method of connecting members at a joint by inserting ductile metal pins into holes in the pieces being joined and forming a head at each end to prevent the joint from coming apart. Typical types of rivets are shown in Fig. 4.3.1 see also Fig. 4.1.1a . Riveting required a crew of four or five experienced persons. On the other hand, the crews required for high-strength bolt installation do not need to be highly skilled. Inspection was difficult, and cutting out and replacing bad...

## A618

Hot-formed welded and seamless square, rectangular, round, or special shape structural tubing for bolted and welded general structural purposes Grade II has corrosion resistance about twice that of carbon steel Grade I has corrosion resistance about four times that of carbon steel Grade III for enhanced corrosion resistance may have copper specified A709 Carbon high-strength low-alloy and quenched and tempered alloy Structural shapes, plates, and bars in Grades 36, 50, and 50W for use in...

## Allowable Stress Design Point Bracing

For ASD a factor of safety FS must be applied so that the service load P may be used instead of Pcr. If FS 2. the strength requirement may be expressed in term of service load P however, the stiffness required will be the same in ASD as in LRFD. Where the strength of the compression member being braced is controlled by an elastic limit state Fcr Fy, as would be the case for columns, the foregoing is applicable. When large plastic strain must be accommodated at bracing points, the design...