problem description
title="Truss Sample Problem (Bridge)" nodes=12 elements=32 
analysis=spectral

analysis parameters
beta=0.25 gamma=0.5 
nodes=[4,5,6] dofs=[Ty] mass-mode=lumped
start=1.0   stop=20.0  step=1.0

nodes
1	x=0	y=0	z=0	constraint=pinned
2	x=70	y=18		constraint=free
3	x=140	y=0		constraint=roller
4	x=55	y=30		constraint=free		force=front_pallet
5	x=70						
6	x=85						force=front_pallet
7	x=0	y=0	z=48 	constraint=roller_z
8 	x=70	y=18		constraint=free
9 	x=140	y=0		constraint=roller_xz
10	x=55	y=30		constraint=free		force=rear_pallet
11	x=70					
12	x=85						force=rear_pallet

truss elements
1	nodes=[1,2]	material=flat
2	nodes=[1,4]	material=double
3	nodes=[2,4]     material=angle
4	nodes=[4,5]	material=angle
5	nodes=[2,5]	material=flat
6	nodes=[5,6]	material=angle
7	nodes=[2,6]	material=angle
8	nodes=[2,3]	material=flat 
9	nodes=[3,6]	material=double
10	nodes=[1,7]	material=flat
11	nodes=[3,9]	material=flat
12	nodes=[2,8]	material=flat
13	nodes=[4,10]    material=flat
14	nodes=[5,11]	material=flat
15	nodes=[6,12]	material=flat
16	nodes=[7,8]	material=angle 
17	nodes=[7,10]	material=angle 
18	nodes=[8,10]	material=flat 
19	nodes=[10,11]	material=angle 
20	nodes=[8,11]	material=flat 
21	nodes=[11,12]   material=angle
22	nodes=[8,12]	material=flat 
23	nodes=[8,9]	material=angle 
24	nodes=[12,9]	material=angle  

/*
 * The non-symmetric bracing ...
 */

25 	nodes=[1,5]	material=flat
26	nodes=[3,5]	material=flat
27	nodes=[1,3]	material=angle	
28	nodes=[7,9]	material=flat  
29	nodes=[4,7]	material=angle
30	nodes=[6,9]	
31	nodes=[4,11]	material=flat
32	nodes=[6,11]	         

material properties
flat	a=0.25		e=29e6	rho=3.4*0.25/12
angle	a=0.4375	e=29e6	rho=3.4*0.4375/12
triple	a=0.75		e=29e6	rho=3.4*0.75/12
built	a=0.875		e=29e6	rho=3.4*0.875/12
double	a=0.5		e=29e6	rho=3.4*0.5/12

/* 
 * based on an eccentric (6") load of 1000 lbs 
 * there will be 625 pounds going to the front truss
 * and 375 pounds going to the back truss
 */

forces
front_pallet fy=-625/2*cos(t) 
rear_pallet fy=-375/2*cos(t)

constraints
pinned    tx=c ty=c tz=c
roller    tx=u ty=c tz=c
roller_z  tx=c ty=c tz=u
roller_xz tx=u ty=c tz=u
free      tx=u ty=u tz=u

end