AISC curtis1989Q2.pdf
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1、Column Flange Strength at Moment End-Plate Connections LARRY E. CURTIS and THOMAS M. MURRAY INTRODUCTION Current American Institute of Steel Construction (AISC) design recommendations for moment end-plate connections are basically limited to the end-plate, bolts, and the compression region of the co
2、lumn side of the connection (AISC2,3.4). Although specific design procedures for column flange strength at the tension regions of the connection have not been included in AISC design manuals, much research on this topic has been conducted in Europe (Zoetemeijer,16 Packer and Morris,15 Mann and Morri
3、s,12 Kennedy, Vinnakota, and Sherbourne,8) and in the United States.4,7 (See Murray, Ref. 13, for a more complete list.) The purpose of this paper is to present design recommendations for required column flange strength at the tension region of the moment end-plate connection configurations shown in
4、 Figs. 1 and 2. The configuration shown in Fig. 1 will be referred to as the 4-bolt stiffened end-plate and that in Fig. 2 as the 8-bolt stiffened end-plate. A design procedure for the latter configuration has recently been published.14 BACKGROUND Limit states associated with the column flange at mo
5、ment end-plate connections include column flange flexural strength, connection stiffness, and the effect on tension bolt forces because of flange bending. Criteria to evaluate these limit states have typically been developed using a tee-stub analogy. In this analogy, a prescribed effective column fl
6、ange length is used for the length of the tee-stub flange as shown in Fig. 3. Procedures utilizing yield-line theory and finite element analysis have been used to analyze this teestub model. Yield-line based studies were performed by Zoetemeijer;16 Packer and Morris;15 Mann and Morris;12 and Kennedy
7、, Vinnakota, and Sherbourne,8 among others. All these studies utilize the concept of an effective column flange length and an assumed yield-line pattern over this length. The first three studies develop design methods based on experim- Larry E. Curtis is structural engineer, Frankfurt-Short-Bruza As
8、sociates P.C., Oklahoma City, Oklahoma. Thomas M. Murray is Montague-Betts Professor of Structural Steel Design, The Charles E. Via, Jr., Department of Civil Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia. entally tested beam-to-column moment end-plate connect
9、ions. The latter study utilizes two tee-stub tests to justify the results. Finite element studies, have been performed by Krish- namurthy,9,10 Ahuja,2 and Ghassemich.6 The first studies resulted in design procedure for 4-bolt, stiffened end-plates Fig. 1. 4-Bolt, Stiffened Moment End-Plate Connectio
10、n Fig. 2. 8-Bolt, Stiffened Moment End-Plate Connection SECOND QUARTER / 198941 (Fig. 1). The latter two studies used the tee-stub analogy to develop design procedures for the 8-bolt stiffened, end-plate configuration shown in Fig. 2. All of these studies resulted in design equations for end-plate s
11、trength that were developed using regression analyses techniques and finite element analysis results. The latter two studies also provide regression analysis based equations for predicting end-plate stiffness and bolt force including prying effects. Although these procedures are for end-plate design
12、, they can be adapted for the design of the column flange in the tension region of a beam-to-column moment end-plate connection if an effective column flange length is defined. Hendrick and Murry7 conducted a limited series of tests to evaluate several European design methods for use with North Amer
13、ican rolled sections. They concluded that the method Fig. 3. Tee-Stub Analogy and Effective Length of Column Flange Fig. 4. Test Configuration proposed by Man and Morris12 is the most suitable for the evaluation of unstiffened column flanges in the tension region of 4-bolt, unstiffened end-plate con
14、nections. They also modified the Krishnamurthy10 results by introducing an effective column flange length equal to 3.5 times the vertical bolt pitch at the beam tension flange to obtain the same results as found with the Mann and Morris12 equations. Finally, they developed a “rule of thumb,“ found i
15、n the AISC Engineering for Steel Construction,3 which states that, under certain limitations, the column flange is adequate if its thickness is greater than the required bolt diameter from the Krishnamurthy end-plate design procedure.11 Curtis5 conducted extensive analytical and experimental studies
16、 to determine column flange strength, connection stiffness, and bolt force predictions for the 4-bolt stiffened (Fig. 1) and the 8-bolt stiffened configuration (Fig. 2). Four 4-bolt stiffened and nine 8-bolt stiffened tests were conducted using the test setup shown in Fig. 4. Column, beam, and end-p
17、late data are identified in Tables 1, 2, and 3. The specimens were instrumented and monitored for separation at the intersection of the planes of the beam tension flange and the beam/column webs, between the outside edges of the beam and column flanges and between column flanges. Bolt force measurem
18、ents were also made. A typical result is shown in Fig. 5. The tests were stopped when either excessive flange deformation or high bolt forces occurred. Ultimate load predictions were made for column flange strength and bolt strength. In addition, load predictions were made for connection stiffness a
19、t 0.015 in. plate separation. Column flange strength predictions were calculated using the design procedure for unstiffened, extended end-plates found in the AISC manuals,2,3 with several modifications. That is, the column flange was treated as an unstiffened end- plate having a width equal to the e
20、ffective length of the colu- Fig. 5. Typical Test Results 42ENGINEERING JOURNAL / AMERICAN INSTITUTE OF STEEL CONSTRUCTION mn flange. The column flange flexural strength, Mef, was determined from () MFtb efycfcs = 167 0756 2 /(1) where tfc = column flange thickness, bs = effective column flange leng
21、th, and Fyc = column flange material yield strength. The constant 1.67 represents the implied factor of safety in the AISC procedure. The column flange strength is related to the applied test moment, Mbeam, as follows F M p f ef me = 4 (2) where Ff = beam flange force, m = constant depending on conn
22、ection geometry and material yield stresses, and pe = effective bolt distance. And Mbeam = Ff (d tfb)(3) where d = beam depth and tfb = beam flange thickness. In the AISC procedure m = CaCb(Af/Aw) 13 (pe/db)(4) where Ca = constant depending on the yield stress of the beam and end-plate material and
23、type of bolt, Cb = (bf/bp),bf = beam flange width, bp = end-plate width, Af = area of beam tension flange, Aw = area of beam web, db = the bolt diameter, and the effective bolt distance is given by pe = pf db/4 wt(5) where pf = distance from centerline of the tension bolts to the nearer surface of t
24、he beam tension flange and wt = fillet weld throat size or reinforcement of groove weld. Based on the recommendations of Hendrick and Murray,7 the following modifications were made in the basic AISC procedures: Cb = 1.0, Af/Aw = 1.0 and pe = pf db/4 rc(6) where, as shown in Figure 6, pf = (g twc)/2,
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