how do you overlap connections in staad?

Say I have an existing frame of angle bars and i want to attach an extension to the vertical members to raise its overall height. The connection appearance would be similar to an overlapping splice. How exactly can I model that so its considered as 1 (one) structure?

Here is the staad input. The members without assigned properties are the supposed extension.

STAAD SPACE
START JOB INFORMATION
ENGINEER DATE 22-Jun-16
JOB NAME CVT - Cadiz
END JOB INFORMATION
INPUT WIDTH 79
UNIT MMS KN
JOINT COORDINATES
1 0 0 0; 2 650 0 0; 3 0 0 -650; 4 650 0 -650; 5 0 445 0; 6 650 445 0;
7 0 445 -650; 8 650 445 -650; 9 0 850 0; 10 650 850 0; 11 0 850 -650;
12 650 850 -650; 13 0 1255 0; 14 650 1255 0; 15 0 1255 -650; 16 650 1255 -650;
17 0 1700 0; 18 650 1700 0; 19 0 1700 -650; 20 650 1700 -650; 21 0 788 0;
22 0 788 -650; 23 0 1368 0; 24 0 1368 -650; 25 0 788 107; 26 0 788 -757;
27 0 1368 107; 28 0 1368 -757; 29 0 1483 -650; 30 0 1483 0; 31 650 1483 0;
32 650 1483 -650; 33 0 1598 -650; 34 0 1598 0; 35 650 1598 0; 36 650 1598 -650;
37 0 2000 0; 38 650 2000 0; 39 0 2000 -650; 40 650 2000 -650; 41 0 1773 -650;
42 0 1773 0; 43 650 1773 0; 44 650 1773 -650; 45 0 1898 -650; 46 0 1898 0;
47 650 1898 0; 48 650 1898 -650; 49 -65 2000 65; 50 715 2000 65;
51 -65 2000 -715; 52 715 2000 -715;
MEMBER INCIDENCES
1 1 5; 2 5 21; 3 21 9; 4 9 13; 5 13 23; 6 23 30; 7 2 6; 8 6 10; 9 10 14;
10 14 31; 11 4 8; 12 8 12; 13 12 16; 14 16 32; 15 3 7; 16 7 22; 17 22 11;
18 11 15; 19 15 24; 20 24 29; 21 3 1; 22 1 2; 23 2 4; 24 4 3; 25 1 6; 26 3 5;
27 4 7; 28 2 8; 29 6 9; 30 5 11; 31 7 12; 32 8 10; 33 10 9; 34 9 11; 35 11 12;
36 12 10; 37 9 14; 50 22 21; 51 11 13; 52 12 15; 53 10 16; 58 24 23; 59 23 27;
60 24 28; 61 21 25; 62 22 26; 63 29 33; 64 30 34; 65 31 35; 66 32 36; 67 33 19;
68 34 17; 69 35 18; 70 36 20; 71 17 42; 72 19 41; 73 18 43; 74 20 44; 75 41 45;
76 42 46; 77 43 47; 78 44 48; 79 13 29; 80 14 30; 81 16 31; 83 29 42; 84 30 43;
85 31 44; 86 32 41; 87 45 39; 88 46 37; 89 47 38; 90 48 40; 91 42 45; 92 43 46;
93 44 47; 94 41 48; 95 39 37; 96 37 38; 97 38 40; 98 40 39; 104 15 32;
ELEMENT INCIDENCES SHELL
99 51 52 40 39; 100 51 39 37 49; 101 37 38 50 49; 102 38 40 52 50;
103 39 40 38 37;
ELEMENT PROPERTY
99 TO 103 THICKNESS 10
DEFINE MATERIAL START
ISOTROPIC STEEL
E 205
POISSON 0.3
DENSITY 7.68195e-008
ALPHA 1.2e-005
DAMP 0.03
TYPE STEEL
STRENGTH FY 0.2532 FU 0.4078 RY 1.5 RT 1.2
END DEFINE MATERIAL
CONSTANTS
MATERIAL STEEL MEMB 1 TO 37 50 TO 53 58 TO 70 79 TO 81 83 TO 86 91 TO 94 99 -
100 TO 104
MEMBER PROPERTY AMERICAN
1 TO 24 63 TO 70 TABLE ST L25253
25 TO 37 51 TO 53 79 TO 81 83 TO 86 91 TO 94 104 TABLE ST L20203
50 58 TO 62 TABLE ST C5X6
SUPPORTS
1 TO 4 PINNED
DEFINE WIND LOAD
TYPE 1 WIND 1
<! STAAD PRO GENERATED DATA DO NOT MODIFY !!!
ASCE-7-2010ARAMS 200.000 kmph 4 1 1 0 0.000 ft 0.000 ft 0.000 ft 1 -
0 2.000 m 0.650 m 0.000 m 0.600 2.000 0.010 -
0 0 0 0 0.575 1.000 1.000 0.850 0 -
0 0 0 0.906 1.600 -0.550
!> END GENERATED DATA BLOCK
INT 1.34108e-006 1.34108e-006 HEIG 0 4572
EXP 1 JOINT 1 TO 52
LOAD 1 LOADTYPE Wind TITLE W +X
WIND LOAD X 1 TYPE 1 YR 0 2000 OPEN
LOAD 2 LOADTYPE Wind TITLE W -X
WIND LOAD X -1 TYPE 1 YR 0 2000 OPEN
LOAD 3 LOADTYPE Wind TITLE W +Z
WIND LOAD Z 1 TYPE 1 YR 0 2000 OPEN
LOAD 4 LOADTYPE Wind TITLE W -Z
WIND LOAD Z -1 TYPE 1 YR 0 2000 OPEN
LOAD 5 LOADTYPE Dead TITLE DEAD LOAD
SELFWEIGHT Y -1
JOINT LOAD
17 TO 20 FY -1.075
21 TO 24 FY -0.295
LOAD COMB 6 COMBINATION LOAD CASE 6
5 1.4
LOAD COMB 7 1.2D +.8WX +.8WZ
5 1.2 1 0.8 3 0.8
LOAD COMB 8 1.2D +.8WX -.8WZ
5 1.2 1 0.8 4 -0.8
LOAD COMB 9 1.2D -.8WX +.8WZ
5 1.2 2 -0.8 3 0.8
LOAD COMB 10 1.2D -.8WX -.8WZ
5 1.2 2 -0.8 4 -0.8
PERFORM ANALYSIS
PARAMETER 1
CODE LRFD
CHECK CODE MEMB 1 TO 37 50 TO 53 58 TO 70
FINISH

Thank you in advance for any help you can provide.