Problem Set No. 3
Problem Set No. 3
3
1. The structural frame shown has a rigid beam and is rigid jointed at both ends of the
three columns. The mass of the structure of 6000 kg is concentrated at the top. The
columns are 3.2 m long and each has an EI = 4.6 x 10 6 N-m2. The structure has a viscous
damping (h) of 5%. Model the structure as an SDOF shear building. A blast load F(t) is
applied as shown.
b. Determine the maximum displacement produced by the blast load and the resulting
shear force and bending moment in the columns.
2. If F(t) in Problem 1 is replaced by ground motion (ug), plot the acceleration data,
velocity data, and displacement data in time domain. Determine the maximum
acceleration, velocity and displacement. Use numerical integration by Newmark’s
constant acceleration method to complete the velocity and displacement data. Consider
the Taiwan ground motion data attached herewith.
Solution: ξ = 0.05
1. m = 6000 kg Stiffness, k:
EI = 4.6 x 106 N-m2
12 EI 12( 4.6 x 106 ) 12
k = 3 x 3= x 3=5.054 x 10 6 N /m at t=0 ¿ 0.25: F ¿i= t
L 3.23 0.25
12
Natural frequency, ⍵: at t=0.26 ¿ 0.50: F ¿i= (0.5−t)
0.25
c = ξ x 2m⍵n ů i+1 = ů i + ∆ů i
c = 0.05 (2 x 6,000 x 29.023) = 17413.8
ü i+1 = ü i + ∆ü i
Newmark’s Constant Acceleration ∆F
method:
i∗¿=∆ F i + ( 4∆mt +2 c ) ů +2 m ü ¿
i i
F
∆t ∆ t2 ∆t ∆=∆t 2 i∗¿ ¿
( m+ c +
2 4 ) ( ∆ u
k üi +1=f i+1−c u̇ i+ üi −k ui +∆ t u̇i+
2
i
) (
ü
4 ki i∗¿ ¿ )
u̇i +1=u̇i +
∆t
(ü + ü )
2 i i +1
∆ ů i= ( ∆2t ) ∆ u −2u i i
∆t 2 4
ui +1=ui +∆ t u̇ i+ ( üi+ üi+1 ) ∆ ü i= ( ∆ ui−∆ t ůi )−2üi
4 ∆ t2
Initial conditions:
u0 = 0 m
ů 0 = 0 m/s
ü 0 = 0 N/m2
F0 = 0 N
Δt = 0.01 s
k 2c 4m 2 x17413.8 4 x 6,000
i∗¿=k + + =5.054 x 10 6+ + ¿
∆ t ∆ t2 0.01 ¿¿
Displacement (m)
0
0
0.01 0.05 0.09 0.13 0.17 0.21 0.25 0.29 0.33 0.37 0.41 0.45 0.49 0.53 0.57 0.61 0.65 0.69 0.73 0.77 0.81 0.85 0.89 0.93 0.97 1.01
0
Time (s)
Velocity (m/s)
0
0
0.01 0.05 0.09 0.13 0.17 0.21 0.25 0.29 0.33 0.37 0.41 0.45 0.49 0.53 0.57 0.61 0.65 0.69 0.73 0.77 0.81 0.85 0.89 0.93 0.97 1.01
0
Time (s)
Acceleration (m/s2)
0
0
0.01 0.05 0.09 0.13 0.17 0.21 0.25 0.29 0.33 0.37 0.41 0.45 0.49 0.53 0.57 0.61 0.65 0.69 0.73 0.77 0.81 0.85 0.89 0.93 0.97 1.01
0
Time (s)
F = k δmax
F = (5.054 x 106)(2.36433 x 10-6)
F = 11.95 N
M = FL
M = (11.95)(3.2)
M = 38.24 N-m
2. If F(t) in Problem 1 is replaced by ground motion (ug), plot the acceleration data,
velocity data, and displacement data in time domain. Determine the maximum
acceleration, velocity and displacement. Use numerical integration by Newmark’s
constant acceleration method to complete the velocity and displacement data. Consider
the Taiwan ground motion data attached herewith.
m = 6000 kg
EI = 4.6 x 106 N-m2 Newmark’s Constant Acceleration
ξ = 0.05 method:
k = 5.054 x 106 N/m ∆t ∆ t2 ∆t ∆ t2
⍵ = 29.023 rad/s
c = 17413.8
(m+ c +
2 4 ) ( 2 ) (
k üi +1=f i+1−c u̇ i+ üi −k ui +∆ t u̇i+
4
u
[6000 + (0.005 x 17413.8) + (0.000025)(5.054 x
106)] ü i+1 = -94.5213 – 17413.8 [0 + 0.005(0)] –
(5.054 x 106) (0 + 0.001(0) + 0.000025(0)]
Initial conditions:
ü i+1 = -0.015212445 m/s2 u0 = 0 m
ů 0 = 0 m/s
∆t ü 0 = 0 N/m2
u̇i +1=u̇i + (ü + ü ) Δt = 0.01 s
2 i i +1
ui+1 = ui + ∆ui
∆t
2 ů i+1 = ů i + ∆ů i
ui +1=ui +∆ t u̇ i+ ( üi+ üi+1 ) ü i+1 = ü i + ∆ü i
4
F i∗¿
∆ u i=∆ ¿
ui+1 = 0 + 0.01(0) + (0.000025)(0- k i∗¿ ¿
0.015212445) 2
-7
( )
∆ ů i=
∆t
∆ ui−2ui
ui+1 = -3.80311125x10 m 4
∆ ü i= 2 ( ∆ ui−∆ t ůi )−2üi
∆t
tί üg m x üg x g uί ůί üί
0.00 0.00413052 243.1224072 0 0 0
0.01 0.00160587 94.5215082 -3.81E-07 -7.61E-05 -0.01522154
-
0.00149949 -1.84E-06 -0.01257915
0.02 88.2599814 0.000215111
-
0.0005037 -4.32E-06 -0.00057811
0.03 29.647782 0.000280897
-
-0.00220545 -6.46E-06 0.02737649
0.04 -129.812787 0.000146905
0.02724096
-0.00226284 -6.56E-06 0.000126182
0.05 -133.1907624 9
0.01459649
-0.00122895 -4.25E-06 0.000335369
0.06 -72.335997 5
0.07 0.00164611 96.8900346 -9.41E-07 0.000326796 -0.01631122
0.08 0.00449629 264.6516294 7.99E-07 2.11E-05 -0.04482729
-
0.00554503 -1.41E-06 -0.05190829
0.09 326.3804658 0.000462575
-
0.00555751 -8.45E-06 -0.04483772
0.10 327.1150386 0.000946305
-
0.00454784 -1.97E-05 -0.02470494
0.11 267.6858624 0.001294018
-
0.00181789 -3.29E-05 0.01314235
0.12 107.0010054 0.001351831
- 0.02395369
0.0017191 -4.55E-05
0.13 101.186226 0.001166351 8
- 0.03155532
0.0017261 -5.58E-05
0.14 101.598246 0.000888806 1
- 0.03633352
0.00174368 -6.29E-05
0.15 102.6330048 0.000549362 5
-
0.00176171 -6.66E-05 0.03808229
0.16 103.6942506 0.000177282
0.03675064
0.00177974 -6.65E-05 0.000196882
0.17 104.7554964 9
0.18 0.00178521 105.0774606 -6.28E-05 0.000543881 0.03264908
0.02618383
0.00177782 -5.59E-05 0.000838045
0.19 104.6424852 7
0.01793786
0.00175728 -4.64E-05 0.001058654
0.20 103.4335008 8
0.00855632
0.00173001 -3.51E-05 0.001191125
0.21 101.8283886 6
0.22 0.00169478 99.7547508 -2.30E-05 0.001228053 -0.00117076
0.23 0.00158536 93.3142896 -1.10E-05 0.001173041 -0.0098316
0.24 0.00064057 37.7039502 2.16E-07 0.001076126 -0.00955134
0.25 -0.00037119 -21.8482434 1.05E-05 0.000988952 -0.00788359
0.00223632
-0.00221332 2.03E-05 0.000960715
0.26 -130.2760152 3
0.27 -0.00228875 -134.715825 2.98E-05 0.000947655 -0.00484846
0.28 -0.00229308 -134.9706888 3.89E-05 0.000863289 -0.01202465
0.29 -0.00221927 -130.6262322 4.67E-05 0.00070924 -0.01878511
0.30 -0.00218191 -128.4272226 5.28E-05 0.00049773 -0.02351701
0.31 -0.00204203 -120.1938858 5.65E-05 0.000244059 -0.02721716
-
0.00069358 5.69E-05 -0.053252
0.32 40.8241188 0.000158287
-
0.00083051 5.28E-05 -0.04969289
0.33 48.8838186 0.000673011
-
0.00079674 4.38E-05 -0.04065823
0.34 46.8961164 0.001124767
-
-0.0010453 3.12E-05 -0.0114971
0.35 -61.526358 0.001385544
0.01870189
-0.00298559 1.75E-05 -0.00134952
0.36 -175.7318274 7
-
-0.0057354 5.88E-06 0.05424745
0.37 -337.585644 0.000984773
0.38 -0.00585696 -344.7406656 -1.12E-06 - 0.05957592
0.000415656 5
0.06710958
-0.00672716 -2.11E-06 0.000217771
0.39 -395.9606376 5
0.40 -0.00594191 -349.7408226 3.08E-06 0.000820319 0.05339992
0.04388228
-0.00600733 1.37E-05 0.00130673
0.41 -353.5914438 7
0.01482292
-0.00435184 2.82E-05 0.001600256
0.42 -256.1493024 2
0.43 -0.0035107 -206.639802 4.44E-05 0.001639913 -0.00689159
0.44 -0.00443973 -261.3225078 6.04E-05 0.001552074 -0.01067622
0.45 -0.00445348 -262.1318328 7.51E-05 0.001387785 -0.02218161
0.46 -0.00355272 -209.1130992 8.74E-05 0.001075525 -0.04027024
0.47 -0.00250799 -147.6202914 9.58E-05 0.000594096 -0.05601572
-
0.00026668 9.82E-05 -0.08326245
0.48 15.6967848 0.000102295
-
0.00139109 9.29E-05 -0.08748217
0.49 81.8795574 0.000956018
-
0.00413044 7.87E-05 -0.09992754
0.50 243.1176984 0.001893067
-
0.0041678 5.53E-05 -0.07846065
0.51 245.316708 0.002785008
-
0.00150489 2.48E-05 -0.02574744
0.52 88.5778254 0.003306048
- 0.00288477
0.00144453 -8.78E-06
0.53 85.0250358 0.003420362 2
- 0.02988321
0.00144852 -4.22E-05
0.54 85.2598872 0.003256522 2
-
0.00043981 -7.24E-05 0.06335285
0.55 25.8872166 0.002790341
-
-0.00316496 -9.58E-05 0.11545761
0.56 -186.2895456 0.001896289
- - 0.12413242
-0.00331012
0.57 -194.8336632 0.000108809 0.000698339 8
- 0.12100741
-0.00327841 0.00052736
0.58 -192.9672126 0.000109664 9
0.09946737
-0.00231116 -9.89E-05 0.001629734
0.59 -136.0348776 1
0.06217944
-0.00045495 -7.85E-05 0.002437968
0.60 -26.778357 3
0.02924164
0.00052917 -5.19E-05 0.002895074
0.61 31.1469462 4
0.62 0.00144204 84.8784744 -2.23E-05 0.003019106 -0.00443526
0.63 0.00145207 85.4688402 7.07E-06 0.002855593 -0.02826727
0.64 0.00141314 83.1774204 3.37E-05 0.002470638 -0.04872375
0.65 0.0013849 81.515214 5.56E-05 0.001902844 -0.06483509
0.66 0.0013447 79.149042 7.11E-05 0.001202546 -0.07522437
0.67 0.00134135 78.951861 7.92E-05 0.000427996 -0.07968576
-
0.00133968 7.96E-05 -0.07769523
0.68 78.8535648 0.000358909
-
0.00138184 7.23E-05 -0.06998957
0.69 81.3351024 0.001097333
-
0.00141334 5.82E-05 -0.05682449
0.70 83.1891924 0.001731404
-
0.00146303 3.84E-05 -0.0396729
0.71 86.1139458 0.002213891
-
0.00150743 1.48E-05 -0.01978824
0.72 88.7273298 0.002511196
- 0.00147902
0.00151398 -1.08E-05
0.73 89.1128628 0.002602742 2
- 0.02211301
0.00151269 -3.62E-05
0.74 89.0369334 0.002484782 9
- 0.04041582
0.00151123 -5.95E-05
0.75 88.9509978 0.002172138 7
- 0.05481671
0.0015284 -7.88E-05
0.76 89.961624 0.001695975 2
- 0.06463863
0.00152609 -9.28E-05
0.77 89.8256574 0.001098699 4
-
0.00146498 -0.00010042 0.06959923
0.78 86.2287228 0.000427509
0.07818965
0.00042183 -0.000101 0.000311435
0.79 24.8289138 5
0.09825357
-0.00251366 -9.35E-05 0.001193651
0.80 -147.9540276 9
0.11763424
-0.00626103 -7.61E-05 0.00227309
0.81 -368.5242258 6
0.07654955
-0.00467409 -4.86E-05 0.003244009
0.82 -275.1169374 6
0.04590855
-0.0047117 -1.31E-05 0.0038563
0.83 -277.330662 8
0.00392943
-0.00384908 2.68E-05 0.00410549
0.84 -226.5568488 2
0.85 -0.00293128 -172.5351408 6.70E-05 0.003936531 -0.03772131
0.86 -0.00016559 -9.7466274 0.000103069 0.003284278 -0.09272924
0.87 0.00080019 47.0991834 0.000130549 0.002211791 -0.12176812
0.88 0.0008375 49.29525 0.000146335 0.000945419 -0.13150632
-
0.0008564 0.000149244 -0.13033001
0.89 50.407704 0.000363763
-
0.00089296 0.000139373 -0.11897766
0.90 52.5596256 0.001610301
0.91 0.00107811 63.4575546 0.000117799 -0.00270457 -0.0998761
-
0.0047958 8.56E-05 -0.10683668
0.92 282.280788 0.003738134
0.93 0.00682995 402.010857 4.33E-05 -0.00471802 -0.08914062
-
0.00783108 -7.48E-06 -0.0550468
0.94 460.9373688 0.005438957
-
0.00779745 -6.34E-05 -0.00770791
0.95 458.957907 0.005752731
- - 0.06449895
0.00506648
0.96 298.2130128 0.000119546 0.005468776 8
- - 0.11430725
0.00394553
0.97 232.2338958 0.000169764 0.004574745 3
- - 0.16890935
0.00121298
0.98 71.3960028 0.000208431 0.003158662 2
- - 0.19181597
0.0002458
0.99 14.467788 0.000230999 0.001355035 2
- 0.18953817
0.00025741 0.000551736
1.00 15.1511526 0.000235016 5
DISPLACEMENT (m)
0.01
0
0
0
0
0
0
0
0
0
-0.01
0 5 10 15 20 25 30 35 40
0.1
0.05
-0.05
-0.1
0 5 10 15 20 25 30 35 40
ACCELERATION (m/s2)
2.5
2
1.5
1
0.5
0
-0.5
-1
-1.5
-2
-2.5
0 5 10 15 20 25 30 35 40