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# ws 19 - MEEN 221 Summer 2009 Worksheet 8 Dr A Palazzolo(1...

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Unformatted text preview: MEEN 221 Summer 2009 - Worksheet 8 Dr. A. Palazzolo (1) HWSS (Due: Tues. 30.1mm): Ch 7 (7, 9, 16, 43, 59, 68) (2) Attendance Mandatory for 10:00 am — 12:45 pm, unless excused by instructor. Multiple Quizzes may be given anytime during this period. (3) Today’s Material: Truss Force Analysis By Joints and Sections, Sections 7.1 — 7.4 Analysis of Trusses for Member Forces and Support Reaction‘Forces . Trusses are load bearing structures which are composed of an assemblage of two force “members” connected by “joints”. Assumptions used in truss analyses are: ' "—" ' a) members are connected only at their ends b) members are connected only by frictionless pins 0) truss structure is loaded only at joints (1) weight of members are neglected Note that the loads in the truss members may .all be solved for only if: M = 2j - 3 p m = number of members a (1) j = number of joints ‘ A FBDwis made for each joint to solve for the member loads. Therefore - — ( Xi = 0 . . s . (2) applies at each joint. . In some instances it may simpliﬂ the procedure to augment eqs. 2 with , the eguilibrium egs. for the entire truss. structureI i.e. ~ : for Total Truss Static Equilibrium: 2F, =0 (3) gr, =0 (4) zr=0 (5) O When only two members form a non-collinear truss joint and no external load or support reaction is applied to the joint, then the members must be zero-force members. When three membertruss joint for which two of the members are collinear and the third forms an angle with the ‘ﬁrst two, then the non-collinear member is a zero-force member provided no external force or support reaction is applied to that ioint. The two collinear members carry equal loads (either bot-h tension or both compression). 0C . _ (b) 7-2.4 Example of a truss mum-members. 7-14* Determine the forces in members CD, DE, and DF of the truss shown in Fig. P7-14; State whether each member is in tension' or compression. Example 3 R 7-12 (Similar to R 7—16) -i7-12 @se the lethed 9f joints t9 determine the force-in eneh -member of the truss shown in Fig. P7-12. State whether each member is in tensidn ' ‘or compression, Fig. P7-12. as“: qua" — _‘ METHDD OF d‘EQ—CWMD (6) Truss Member Force Analysis by the Method of Sections. This approach yields the forces in a subset of the truss members without solving node by node, as in the method of joints. 7-44* Use the method of sections to determine the forces in members CD, DE, and EF of thele truss shown in Fig. P7-44. “3’ 3KN 4KN SKN ’1*ﬁﬂ¥'ﬁ§e the nathad sf ~é®¢t£ans ta ﬁatevniwa ‘ ﬁhé f6§Ee§.in-membérs CB, CE, and EF of the trusg shown in Fig. P7-53. 1% ms 25 mm" 7-67* Use the method of ' ‘ 1 sections to determine the forces in members DE, EG, FG, and FH of the truss Shown in Fig. P7-67. (20 ...
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