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Page 1 Table 10.3a Deflection due to external loading Member i L i i E A Forces in the released truss due to applied loading i P Forces in the released truss due to unit load ( ) i v P Forces in the released truss due to unit load ( ) i v Q () AE L P P i i v i () AE L Q P i i v i m ( ) 5 10 kN kN kN kN ( ) 4 10 - m ( ) 4 10 - m AB 4 3 40 +1 0 5.333 0.000 BC 4 3 60 +1 -0.8 8.000 -6.400 CD 4 3 60 +1 0 8.000 0.000 EF 4 3 -20 0 -0.8 0.000 2.133 EB 3 2 15 0 -0.6 0.000 -1.350 FC 3 2 0 0 -0.6 0.000 0.000 AE 5 4 -25 0 0 0.000 0.000 BF 5 4 -25 0 +1 0.000 -3.125 FD 5 4 -75 0 0 0.000 0.000 EC 5 4 0 0 +1 0.000 0.000 Total 21.333 -8.742 Deflection of the released structure along redundant and respectively are, 1 R 2 R () 4 1 21.33 10 m (towards right) L - ?= × () 4 2 8.742 10 m (shortening) L - ?=- × (1) In the next step, compute the flexibility coefficients (ref. Fig. 10.3c and Fig. 10.3d and the accompanying table) Page 2 Table 10.3a Deflection due to external loading Member i L i i E A Forces in the released truss due to applied loading i P Forces in the released truss due to unit load ( ) i v P Forces in the released truss due to unit load ( ) i v Q () AE L P P i i v i () AE L Q P i i v i m ( ) 5 10 kN kN kN kN ( ) 4 10 - m ( ) 4 10 - m AB 4 3 40 +1 0 5.333 0.000 BC 4 3 60 +1 -0.8 8.000 -6.400 CD 4 3 60 +1 0 8.000 0.000 EF 4 3 -20 0 -0.8 0.000 2.133 EB 3 2 15 0 -0.6 0.000 -1.350 FC 3 2 0 0 -0.6 0.000 0.000 AE 5 4 -25 0 0 0.000 0.000 BF 5 4 -25 0 +1 0.000 -3.125 FD 5 4 -75 0 0 0.000 0.000 EC 5 4 0 0 +1 0.000 0.000 Total 21.333 -8.742 Deflection of the released structure along redundant and respectively are, 1 R 2 R () 4 1 21.33 10 m (towards right) L - ?= × () 4 2 8.742 10 m (shortening) L - ?=- × (1) In the next step, compute the flexibility coefficients (ref. Fig. 10.3c and Fig. 10.3d and the accompanying table) Table 10.3b Computation of flexibility coefficients Member i L i i E A () i v P () i i i i v E A L P 2 ( ) i v Q () i i i i v E A L Q 2 ()( ) AE L Q P i i v i v m ( ) 5 10 kN kN ( ) 5 10 - m/kN kN ( ) 5 10 - m/kN ( ) 5 10 - m/kN AB 4 3 +1.00 1.333 0.000 0.000 0.000 BC 4 3 +1.00 1.333 -0.800 0.853 -1.067 CD 4 3 +1.00 1.333 0.000 0.000 0.000 EF 4 3 0 0.000 -0.800 0.853 0.000 EB 3 2 0 0.000 -0.600 0.540 0.000 FC 3 2 0 0.000 -0.600 0.540 0.000 AE 5 4 0 0.000 0.000 0.000 0.000 BF 5 4 0 0.000 1.000 1.250 0.000 FD 5 4 0 0.000 0.000 0.000 0.000 EC 5 4 0 0.000 1.000 1.250 0.000 Total 4.000 5.286 -1.064 Thus, 5 22 5 21 12 5 11 10 286 . 5 10 064 . 1 10 4 - - - × = × - = = × = a a a a (2) Analysis of truss when only external loads are acting The compatibility conditions of the problem may be written as, ( ) 0 2 12 1 11 1 = + + ? R a R a L ( ) 0 2 22 1 21 2 = + + ? R a R a L (3) Solving and 1 51.73 kN (towards left) R =- 2 6.136 kN (tensile) R = The actual member forces and reactions in the truss are shown in Fig 10.3c. Now, compute deflections corresponding to redundants due to rise in temperature in the member . Due to rise in temperature, the change in length of member is, FB FB Page 3 Table 10.3a Deflection due to external loading Member i L i i E A Forces in the released truss due to applied loading i P Forces in the released truss due to unit load ( ) i v P Forces in the released truss due to unit load ( ) i v Q () AE L P P i i v i () AE L Q P i i v i m ( ) 5 10 kN kN kN kN ( ) 4 10 - m ( ) 4 10 - m AB 4 3 40 +1 0 5.333 0.000 BC 4 3 60 +1 -0.8 8.000 -6.400 CD 4 3 60 +1 0 8.000 0.000 EF 4 3 -20 0 -0.8 0.000 2.133 EB 3 2 15 0 -0.6 0.000 -1.350 FC 3 2 0 0 -0.6 0.000 0.000 AE 5 4 -25 0 0 0.000 0.000 BF 5 4 -25 0 +1 0.000 -3.125 FD 5 4 -75 0 0 0.000 0.000 EC 5 4 0 0 +1 0.000 0.000 Total 21.333 -8.742 Deflection of the released structure along redundant and respectively are, 1 R 2 R () 4 1 21.33 10 m (towards right) L - ?= × () 4 2 8.742 10 m (shortening) L - ?=- × (1) In the next step, compute the flexibility coefficients (ref. Fig. 10.3c and Fig. 10.3d and the accompanying table) Table 10.3b Computation of flexibility coefficients Member i L i i E A () i v P () i i i i v E A L P 2 ( ) i v Q () i i i i v E A L Q 2 ()( ) AE L Q P i i v i v m ( ) 5 10 kN kN ( ) 5 10 - m/kN kN ( ) 5 10 - m/kN ( ) 5 10 - m/kN AB 4 3 +1.00 1.333 0.000 0.000 0.000 BC 4 3 +1.00 1.333 -0.800 0.853 -1.067 CD 4 3 +1.00 1.333 0.000 0.000 0.000 EF 4 3 0 0.000 -0.800 0.853 0.000 EB 3 2 0 0.000 -0.600 0.540 0.000 FC 3 2 0 0.000 -0.600 0.540 0.000 AE 5 4 0 0.000 0.000 0.000 0.000 BF 5 4 0 0.000 1.000 1.250 0.000 FD 5 4 0 0.000 0.000 0.000 0.000 EC 5 4 0 0.000 1.000 1.250 0.000 Total 4.000 5.286 -1.064 Thus, 5 22 5 21 12 5 11 10 286 . 5 10 064 . 1 10 4 - - - × = × - = = × = a a a a (2) Analysis of truss when only external loads are acting The compatibility conditions of the problem may be written as, ( ) 0 2 12 1 11 1 = + + ? R a R a L ( ) 0 2 22 1 21 2 = + + ? R a R a L (3) Solving and 1 51.73 kN (towards left) R =- 2 6.136 kN (tensile) R = The actual member forces and reactions in the truss are shown in Fig 10.3c. Now, compute deflections corresponding to redundants due to rise in temperature in the member . Due to rise in temperature, the change in length of member is, FB FB m L T T 3 10 67 . 2 5 40 75000 1 - × = × × = = ? a (4) Due to change in temperature, the deflections corresponding to redundants and are 1 R 2 R () ( ) ( ) () ( )() m Q P i T i v T i T i v T 3 2 1 10 67 . 2 0 - × = ? = ? = ? = ? ? ? (5) When both external loading and temperature loading are acting When both temperature loading and the external loading are considered, the compatibility equations can be written as, ()( ) 0 2 12 1 11 1 1 = + + ? + ? R a R a T L () ( ) 0 2 22 1 21 2 2 = + + ? + ? R a R a T L (6) Solving and 1 65.92 kN(towards left) R =- 2 47.26 kN (compressive) R = - The actual member forces and reactions are shown in Fig. 10.3f Page 4 Table 10.3a Deflection due to external loading Member i L i i E A Forces in the released truss due to applied loading i P Forces in the released truss due to unit load ( ) i v P Forces in the released truss due to unit load ( ) i v Q () AE L P P i i v i () AE L Q P i i v i m ( ) 5 10 kN kN kN kN ( ) 4 10 - m ( ) 4 10 - m AB 4 3 40 +1 0 5.333 0.000 BC 4 3 60 +1 -0.8 8.000 -6.400 CD 4 3 60 +1 0 8.000 0.000 EF 4 3 -20 0 -0.8 0.000 2.133 EB 3 2 15 0 -0.6 0.000 -1.350 FC 3 2 0 0 -0.6 0.000 0.000 AE 5 4 -25 0 0 0.000 0.000 BF 5 4 -25 0 +1 0.000 -3.125 FD 5 4 -75 0 0 0.000 0.000 EC 5 4 0 0 +1 0.000 0.000 Total 21.333 -8.742 Deflection of the released structure along redundant and respectively are, 1 R 2 R () 4 1 21.33 10 m (towards right) L - ?= × () 4 2 8.742 10 m (shortening) L - ?=- × (1) In the next step, compute the flexibility coefficients (ref. Fig. 10.3c and Fig. 10.3d and the accompanying table) Table 10.3b Computation of flexibility coefficients Member i L i i E A () i v P () i i i i v E A L P 2 ( ) i v Q () i i i i v E A L Q 2 ()( ) AE L Q P i i v i v m ( ) 5 10 kN kN ( ) 5 10 - m/kN kN ( ) 5 10 - m/kN ( ) 5 10 - m/kN AB 4 3 +1.00 1.333 0.000 0.000 0.000 BC 4 3 +1.00 1.333 -0.800 0.853 -1.067 CD 4 3 +1.00 1.333 0.000 0.000 0.000 EF 4 3 0 0.000 -0.800 0.853 0.000 EB 3 2 0 0.000 -0.600 0.540 0.000 FC 3 2 0 0.000 -0.600 0.540 0.000 AE 5 4 0 0.000 0.000 0.000 0.000 BF 5 4 0 0.000 1.000 1.250 0.000 FD 5 4 0 0.000 0.000 0.000 0.000 EC 5 4 0 0.000 1.000 1.250 0.000 Total 4.000 5.286 -1.064 Thus, 5 22 5 21 12 5 11 10 286 . 5 10 064 . 1 10 4 - - - × = × - = = × = a a a a (2) Analysis of truss when only external loads are acting The compatibility conditions of the problem may be written as, ( ) 0 2 12 1 11 1 = + + ? R a R a L ( ) 0 2 22 1 21 2 = + + ? R a R a L (3) Solving and 1 51.73 kN (towards left) R =- 2 6.136 kN (tensile) R = The actual member forces and reactions in the truss are shown in Fig 10.3c. Now, compute deflections corresponding to redundants due to rise in temperature in the member . Due to rise in temperature, the change in length of member is, FB FB m L T T 3 10 67 . 2 5 40 75000 1 - × = × × = = ? a (4) Due to change in temperature, the deflections corresponding to redundants and are 1 R 2 R () ( ) ( ) () ( )() m Q P i T i v T i T i v T 3 2 1 10 67 . 2 0 - × = ? = ? = ? = ? ? ? (5) When both external loading and temperature loading are acting When both temperature loading and the external loading are considered, the compatibility equations can be written as, ()( ) 0 2 12 1 11 1 1 = + + ? + ? R a R a T L () ( ) 0 2 22 1 21 2 2 = + + ? + ? R a R a T L (6) Solving and 1 65.92 kN(towards left) R =- 2 47.26 kN (compressive) R = - The actual member forces and reactions are shown in Fig. 10.3f Page 5 Table 10.3a Deflection due to external loading Member i L i i E A Forces in the released truss due to applied loading i P Forces in the released truss due to unit load ( ) i v P Forces in the released truss due to unit load ( ) i v Q () AE L P P i i v i () AE L Q P i i v i m ( ) 5 10 kN kN kN kN ( ) 4 10 - m ( ) 4 10 - m AB 4 3 40 +1 0 5.333 0.000 BC 4 3 60 +1 -0.8 8.000 -6.400 CD 4 3 60 +1 0 8.000 0.000 EF 4 3 -20 0 -0.8 0.000 2.133 EB 3 2 15 0 -0.6 0.000 -1.350 FC 3 2 0 0 -0.6 0.000 0.000 AE 5 4 -25 0 0 0.000 0.000 BF 5 4 -25 0 +1 0.000 -3.125 FD 5 4 -75 0 0 0.000 0.000 EC 5 4 0 0 +1 0.000 0.000 Total 21.333 -8.742 Deflection of the released structure along redundant and respectively are, 1 R 2 R () 4 1 21.33 10 m (towards right) L - ?= × () 4 2 8.742 10 m (shortening) L - ?=- × (1) In the next step, compute the flexibility coefficients (ref. Fig. 10.3c and Fig. 10.3d and the accompanying table) Table 10.3b Computation of flexibility coefficients Member i L i i E A () i v P () i i i i v E A L P 2 ( ) i v Q () i i i i v E A L Q 2 ()( ) AE L Q P i i v i v m ( ) 5 10 kN kN ( ) 5 10 - m/kN kN ( ) 5 10 - m/kN ( ) 5 10 - m/kN AB 4 3 +1.00 1.333 0.000 0.000 0.000 BC 4 3 +1.00 1.333 -0.800 0.853 -1.067 CD 4 3 +1.00 1.333 0.000 0.000 0.000 EF 4 3 0 0.000 -0.800 0.853 0.000 EB 3 2 0 0.000 -0.600 0.540 0.000 FC 3 2 0 0.000 -0.600 0.540 0.000 AE 5 4 0 0.000 0.000 0.000 0.000 BF 5 4 0 0.000 1.000 1.250 0.000 FD 5 4 0 0.000 0.000 0.000 0.000 EC 5 4 0 0.000 1.000 1.250 0.000 Total 4.000 5.286 -1.064 Thus, 5 22 5 21 12 5 11 10 286 . 5 10 064 . 1 10 4 - - - × = × - = = × = a a a a (2) Analysis of truss when only external loads are acting The compatibility conditions of the problem may be written as, ( ) 0 2 12 1 11 1 = + + ? R a R a L ( ) 0 2 22 1 21 2 = + + ? R a R a L (3) Solving and 1 51.73 kN (towards left) R =- 2 6.136 kN (tensile) R = The actual member forces and reactions in the truss are shown in Fig 10.3c. Now, compute deflections corresponding to redundants due to rise in temperature in the member . Due to rise in temperature, the change in length of member is, FB FB m L T T 3 10 67 . 2 5 40 75000 1 - × = × × = = ? a (4) Due to change in temperature, the deflections corresponding to redundants and are 1 R 2 R () ( ) ( ) () ( )() m Q P i T i v T i T i v T 3 2 1 10 67 . 2 0 - × = ? = ? = ? = ? ? ? (5) When both external loading and temperature loading are acting When both temperature loading and the external loading are considered, the compatibility equations can be written as, ()( ) 0 2 12 1 11 1 1 = + + ? + ? R a R a T L () ( ) 0 2 22 1 21 2 2 = + + ? + ? R a R a T L (6) Solving and 1 65.92 kN(towards left) R =- 2 47.26 kN (compressive) R = - The actual member forces and reactions are shown in Fig. 10.3f Summary In this lesson, the flexibility matrix method is used to analyse statically indeterminate planar trusses. The equation to calculate the degree of statical indeterminacy of a planar truss is derived. The forces induced in the members due to temperature loading and member lack of fit is also discussed in this lesson. Few examples are solved to illustrate the force method of analysis as applied to statically indeterminate planar trusses.Read More
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1. What is the Force Method of Analysis for trusses? |
2. How does the Force Method of Analysis work for trusses? |
3. What are the advantages of using the Force Method of Analysis for trusses? |
4. Are there any limitations or assumptions of the Force Method of Analysis for trusses? |
5. How can the Force Method of Analysis be applied in practical civil engineering projects? |
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