毕业论文外文翻译-受弯钢框架结点在变化轴向荷载和侧向位移的作用下的周期性行为

1、土木工程建筑外文文献及翻译cyclic behavior of steel moment frame connections under varying axial load and lateral displacementsabstractthis paper discusses the cyclic behavior of four steel moment connections tested under variable axial load and lateral displacements the beam specim- ens consisted of a reducedbea

2、m section, wing plates and longitudinal stiffeners the test specimens were subjected to varying axial forces and lateral displace ments to simulate the effects on beams in a coupled-girder moment-resisting framing system under lateral loading. the test results showed that the specim- ens responded i

3、n a ductile manner since the plastic rotations exceeded 0.03 rad without significant drop in the lateral capacity the presence of the longitudin- al stiffener assisted in transferring the axial forces and delayed the formation of web local buckling.i. 1 ntroductionaimed at evaluating the structural

4、performance of rcduccd-bcam section(rbs) connections under alternated axial loading and lateral displacement, four full-scale specimens were tested. these tests were intended to assess the performance of the moment connection design for the moscone center exp ansion under the design basis earthquake

5、 (dbe) and the maximum considered earthquake (mce). previous research conducted on rbs moment connections 1,2 showed that connections with rbs profiles can achieve rotations in excess of 0.03 rad. however, doubts have been cast on the quality of the seismic performance of these connections under com

6、bined axial and lateral loading.the moscone center expansion is a three-story, 71,814 m2 (773,000 ft2) structure with steel moment frames as its primary lateral force-resisting system. a three dimensional perspective illustration is shown in fig. l the overall height of the building, at the highest

7、point of the exhibition roof, is approxima- tely 35.36 m (116ft) above ground level. the ceiling height at the exhibition hall is 8.23 m (27 ft) , and the typical floor-to-floor height in the building isii. 43 m (37.5 ft). the building was designed as type i according to the requi- rements of the 19

8、97 uniform building code.the framing system consists of four moment frames in the east-west direct ion，one on either side of the stair towers, and four frames in the north-south direction, one on either side of the stair and elevator cores in the east end and two at the west end of the structure 4.

9、because of the story height, the con cept of the coupled-girder moment-resisting framing system (cgmrfs) was utilized.by coupling the girders, the lateral load-resisting behavior of the moment framing system changes to one where structural overturning moments are resisted partially by an axial compr

10、ession-tension couple across the girder system, rather than only by the individual flexural action of the girders. as a result, a stiffer lateral load resisting system is achieved. the vertical element that connects the girders is referred to as a coupling link coupling links arc analogous to and se

11、rve the same structural role as link beams in eccentrically braced frames coupling links are generally quite short, having a large shear- to-moment ratio under earthquake-type loading, the cgmrfs subjects its girders to wariab- ble axial forces in addition to their end moments. the axial forces in t

12、hefig. 1. moscone center expansion project in san francisco, ca girders result from the accumulated shear in the link.2. analytical model of cgmrfnonlinear static pushover analysis was conducted on a typical one-bay model of the cgmrf. fig. 2 shows the dimensions and the various sections of the 10 i

13、n) and the -254 mm (1 1/8 in model. the link flange plates were 28.5 mm 18 3/4 in). the sap 2000 computer -476 mm (3 /8 in web plate was 9.5 mm program was utilized in the pushover analysis 5. the frame was characterized as fully restrained(fr). fr moment frames are those frames for 1170 which no mo

14、re than 5% of the lateral deflections arise from connection deformation 6. the 5% value refers only to deflection due to beam-column deformation and not to frame deflections that result from column panel zone deformation 6, 9.the analysis was performed using an expected value of the yield stress and

15、 ultimate strength. these values were equal to 372 mpa (54 ksi) and 518 mpa (75 ksi), respectively. the plastic hinges' load-deformation behavior was approximated by the generalized curve suggested by nehrp guidelines for the seismic rehabilitation of buildings 6 as shown in fig 3 zy was calcu l

16、ated based on eqs. (5.1) and (5.2) from 6, as follows:p-m hinge load-deformation model points c, d and e are based on table 5.4 from 6 fory was taken as 0.01 rad per note 3 in 6, table 5.8. shear hinge load load-defbrmation model points c, d and e are based on table 5.8 6, link beam, item a. a strai

17、n hardening slope between points b and c of 3% of the clastic slope was assumed for both models.the following relationship was used to account for moment-axial load interaction 6:where mce is the expected moment strength, zrbs is the rbs plastic section modulus (in3), is the expected yield strength

18、of the material (ksi), p is the axial force in the girder (kips) and is the expected axial yield force of the rbs, equal to (kips) the ultimate flexural capacities of the beam and the link of the model are shown in table 1.fig. 4 shows qualitatively the distribution of the bending moment, shear forc

19、e, and axial force in the cgmrf under lateral load the shear and axial force in the beams are less significant to the response of the beams as compared with the bending moment, although they must be considered in design. the qualita- tive distribution of internal forces illustrated in fig. 5 is fund

20、amentally the same for both elastic and inelastic ranges of behavior the specific values of the internal forces will change as elements of the frame yield and internal for- ces are redistributed. the basic patterns illustrated in fig. 5, however, remain the same.inelastic static pushover analysis wa

21、s carried out by applying monotonically increasing lateral displacements, at the top of both columns, as shown in fig. 6. after the four rbs have yielded simultaneously, a uniform yielding in the web and at the ends of the flanges of the vertical link will fbnri. this is the yield mechanism for the

22、frame , with plastic hinges also forming at the base of the columns if they are fixed the base shear versus drift angle of the model is shown in fig. 7 the sequence of inelastic activity in the frame is shown on the figure an clastic component, a long transition (consequence of the beam plastic hing

23、es being formed simultaneously) and a narrow yield plateau characterize the pushover curve.the plastic rotation capacity, qp, is defined as the total plastic rotation beyond which the connection strength starts to degrade below 80% 7. this definition is different from that outlined in section 9 (app

24、endix s) of the aisc seismic provisions & 10. using eq. (2) derived by uang and fan 7, an estimate of the rbs plastic rotation capacity was found to be 0.037 rad:fyf was substituted for ryfy 8, where ry is used to account for the differ- ence between the nominal and the expected yield strengths

25、(grade 50 steel, fy=345 mpa and ry =1.1 are used).3. experimental programthe experimental set-up for studying the behavior of a connection was based on fig. 6(a). using the plastic displacement dp, plastic rotation gp, and plastic story drift angle qp shown in the figure, from geometry, it follows t

26、hat:and:in which d and g include the elastic components approximations as above are used for large inelastic beam deformations. the diagram in fig. 6(a) suggest that a sub assemblage with displacements controlled in the manner shown in fig. 6(b) can represent the inelastic behavior of a typical beam

27、 in a cgmrjf.the test set-up shown in fig. 8 was constructed to develop the mechanism shown in fig. 6(a) and (b). the axial actuators were attached to three 2438 mm x 1219 mm x 1219 mm (8 ft x 4 ft x 4 ft) rc blocks these blocks were tensioned to the laboratory floor by means of twenty32 mm diameter

28、 dywidag rods this arrangement permitted replacement of the specimen after each test.therefore, the force applied by the axial actuator, p, can be resolved into two or thogonal components, paxial and plateral since the inclination angle of the axial actuator does not exceed , therefore paxial is app

29、roximately equal to p 4. however, the lateral°3.0 component, plateral, causes an additional moment at the beam-to column joint. if the axial actuators compress the specimen, then the lateral components will be adding to the lateral actuator forces, while if the axial actuators pull the specimen

30、, the plateral will be an opposing force to the lateral actuators. when the axial actuators undergoaxial actuators undergo a lateral displacement they cause an additional moment at the beam-to-column joint (p-a effect) therefore, the moment at the beam-to column joint is equal to: where h is the lat

31、eral forces, l is the arm, p is the axial force and _ is the lateral displacement. four full-scale experiments of beam column connections were conducted the member sizes and the results of tensile coupon tests are listed in table 2all of the columns and beams were of a572 grade 50 steel (fy 344.5 mp

32、a). the actual measured beam flange yield stress value was equal to 372 mpa (54 ksi), while the ultimate strength ranged from 502 mpa (72.8 ksi) to 543 mpa (7&7 ksi).table 3 shows the values of the plastic moment for each specimen (based on measured tensile coupon data) at the full cross-section

33、 and at the reduced section at mid-length of the rbs cutout.the specimens were designated as specimen 1 through specimen 4. test specimens details arc shown in fig. 9 through fig. 12. the following features were utilized in the design of the beam-column connection:the use of rbs in beam flanges a ci

34、rcular cutout was provided, as illustr- ated in figs. 11 and 12. for all specimens, 30% of the beam flange width was removed. the cuts were made carefully, and then ground smooth in a direct- tion parallel to the beam flange to minimize notches use of a fully welded web connection. the connection be

35、tween the beam web and the column flange was made with a complete joint penetration groove weld (cjp). all cjp welds were performed according to aws dl.l structural welding codeuse of two side plates welded with cjp to exterior sides of top and bottom beam flan- ges, from the face of the column flan

36、ge to the beginning of the rbs, as shown in figs. 11 and 12. the end of the side plate was smoothed to meet the beginning of the rbs the side plates were welded with cjp with the column flanges the side plate was added to increase the flexural capacity at the joint location, while the smooth transit

37、ion was to reduce the stress raisers, which may initiate fracturetwo longitudinal stiffeners, 95 mm x 35 mm (3 3/4 in x 1 3/8 in), were welded with 12.7 mm (1/2 in) fillet weld at the middle height of the web as shown in figs. 9 and 10. the stiffeners were welded with cjp to column flangesremoval of

38、 weld tabs at both the top and bottom beam flange groove welds. the weld tabs were removed to eliminate any potential notches introduced by the tabs or by weld discontinuities in the groove weld run out regionsuse of continuity plates with a thickness approximately equal to the beam flange thickness

39、. one-inch thick continuity plates were used for all specimenswhile the rbs is the most distinguishing feature of these test specimens, the longitudinal stiffener played an important role in delaying the formation of web local buckling and developing reliable connection4. loading historyspecimens we

40、re tested by applying cycles of alternated load with tip displacement increments of _y as shown in table 4. the tip displacement of the beam was imposed by servo-controlled actuators 3 and 4. when the axial force was to be applied, actuators 1 and 2 were activated such that its force simulates the s

41、hear force in the link to be transferred to the beam. 05_y. after+the variable axial force was increased up to 2800 kn (630 kip) at that, this lo- ad was maintained constant through the maximum lateral displacement.maximum lateral displacement. as the specimen was pushed back the axial force remaine

42、d constant until 0.5 y and then started to decrease to zero as the specimen passed through the neutral position 4. according to the upper bound for beam axial force as discussed in section 2 of this paper, it was concluded that p =2800 kn (630 kip) is appropriate to investigate this case in rbs load

43、ing the tests were continued until failure of the specimen, or until limitations of the test set-up were reached5. test resultsthe hysteretic response of each specimen is shown in fig. 13 and fig. 16. these plots show beam moment versus plastic rotation. the beam moment is measured at the middle of

44、the rbs, and was computed by taking an equiva- lent beam-tip force multiplied by the distance between the centerline of the lateral actuator to the middle of the rbs (1792 mm for specimens 1 and 2, 3972 mm for specimens 3 and 4). the equivalent lateral force accounts for the additional moment due to

45、 p- effect the rotation angle was defined as the lateral displacement of the actuator divided by the length between the centerline of the lateral actuator to the mid length of the rbs. the plastic rotation was computed as follows 4: where v is the shear force, ke is the ratio of v/q in the elastic r

46、ange measurements and observations made during the tests indicated that all of the plastic rotation in specimen 1 to specimen 4 was developed within the beam. the connection panel zone and the column remained elastic as intended by design.5.1 specimens 1 and 2the responses of specimens 1 and 2 are s

47、hown in fig. 13. initial yielding occuited during cycles 7 and 8 at l_y with yielding observed in the bottom flange. for all test specimens, initial yielding was observed at this location and attributed to the moment at the base of the specimen 4. progressing through the loading history, yielding st

48、arted to propagate along the rbs bottom flange during cycle 3.5_y initiation of web buckling was noted adjacent to the yielded bottom flange yielding started to propagate along the top flange of the rbs and some minor yielding along the middle stiffener. during the cycle of 5_y with the increased ax

49、ial compression load to 3115 kn (700 kips) a severe web buckle developed along with flange local buckling the flange and the web local buckling became more pronounced with each successive loading cycle it should be noted here that the bottom flange and web local buckling was not accompanied by a sig

50、nificant deterioration in the hysteresis loopsa crack developed in specimen 1 bottom flange at the end of the rbs where it meets the side plate during the cycle 5.75_y upon progressing through the loading history, 7_y, the crack spread rapidly across the entire width of the bottom flange once the bo

51、ttom flange was completely fractured, the web began to fracture. this fracture appeared to initiate at the end of the rbs, then propagated through the web net section of the shear tab, through the middle stiffener and the through the web net section on the other side of the stiflcncr. the maximum be

52、nding moment achieved on specimen 1 during theduring the cycle 6.5 y, specimen 2 also showed a crack in the bottom flange at the end of the rbs where it meets the wing plate. upon progressing thogh the loading history, 15 y, the crack spread slowly across the bottom flan- ge. specimen 2 test was sto

53、pped at this point because the limitation of the test set-up was reached.the maximum force applied to specimens 1 and 2 was 890 kn (200 kip). the kink that is seen in the positive quadrant is due to the application of the varying axial tension force. the load-carrying capacity in this zone did not d

54、eteriorate as evidenced with the positive slope of the force-displacement curve however, the load-carrying capacity deteriorated slightly in the neg- ative zone due to the web and the flange local buckling.photographs of specimen 1 during the test are shown in figs. 14 and 15. severe local buckling

55、occurred in the bottom flange and portion of the web next to the bottom flange as shown in fig. 14. the length of this buckle extended over the entire length of the rbs. plastic hinges developed in the rbs with extensive yielding occurring in the beam flanges as well as the web. fig. 15 shows the cr

56、ack that initiated along the transition of the rbs to the side wing plate. ultimate fracture of specimen 1 was caused by a fracture in the bottom flange this fracture resulted in almost total loss of the beam- carrying capacity. specimen 1 developed 0.05 rad of plastic rotation and showed no sign of

57、 distress at the face of the column as shown in fig. 15.52 specimens 3 and 4the response of specimens 3 and 4 is shown in fig. 16. initial yielding occured during cycles 7 and 8 at l_y with significant yielding observed in the bottom flange. progressing through the loading history, yielding started

58、to propagate along the bottom flange on the rbs. during cycle 1.5_y initiation of web buckling was noted adjacent to the yielded bottom flange. yielding started to propagate along the top flange of the rbs and some minor yielding along the middle stiffener. during the cycle of 3.5_y a severe web buc

59、kle developed along with flange local buckling. the flange and the web local buckling bee ame more pronounced with each successive loading cycle.during the cycle 4.5 y, the axial load was increased to 3115 kn (700 kips) causing yielding to propagate to middle transverse stiffene匚 progressing through the loading history, the flange and the web local buckling became more severe. for both specimens, testing was stopped