Abaqus help

Dear all,

I'm doing a dynamic analysis and optimization of high speed railway bridges. After developing the abaqus input file (*inp), the following errors have occured and I was unable to solve them. I have attached a picture showing the node number that I used to model the train. the car body and the bogies are model as a rigid body in which nodes 6001,6004 and 6501 are the reference nodes. 

1. An overconstraint problem. it says "Zero pivot when processing Node 6004 d.o.f 2, node 6004 d.o.f 6 and node 6001 d.o.f 6

2. I think due to this problem, the force and moment equlibriums did not converged. Sometimes the contact constraints did not converged

3. when I use the sprung mass model of the train, I clearly define the master and slave surfaces. the rail is the master surface the wheel nodes are slave nodes. the surface interaction, surface behaviour (no separation) and the contact pairs are defined as clearly as possible. But i don't know what's wrong with it, after moving some distance the wheel will get out of the rail.

Please have alook part of the input file for both cases and forward me your valuable comments. Thanks alot. 

 Case 1

 ***Train Wagon Model

*Node, Nset=WheelNodes

4001,-90,0

4002,-92.5,0

4003,-107.5,0

4004,-110,0

*Node, Nset=Bogie1Nodes

5001,-90,1

5002,-92.5,1

*Node, Nset=Bogie2Nodes

5003,-107.5,1

5004,-110,1

*Node, Nset=Carbody1Nodes

6002,-91.25,2

6003,-108.75,2

*Node

6001,-91.25,1

6004,-108.75,1

6501,-100,2

*Surface, type=ELEMENT, name=master

ExRail_Left,SPOS

Rail,SPOS

ExRail_Right,SPOS

*Surface, type=NODE, name=slave

WheelNodes, 1.

**INTERACTION PROPERTIES

**

*Surface Interaction, name=ContactProp

1. 

*Friction

0.1

*SURFACE BEHAVIOR, PRESSURE-OVERCLOSURE=HARD

**

*Element, type=Spring2, elset=SpringPrimary

7501, 4001, 5001

7502, 4002, 5002

7503, 4003, 5003

7504, 4004, 5004

*Element, type=Spring2, elset=SpringSecondary

7601, 6001, 6002

7602, 6004, 6003

*Element, type=Dashpot2, elset=DashpotPrimary

8001, 4001, 5001

8002, 4002, 5002

8003, 4003, 5003

8004, 4004, 5004

*Element, type=Dashpot2, elset=DashpotSecondary

8501, 6001, 6002

8502, 6004, 6003

*Element, type=Mass, elset=mWheel

10001,4001

10002,4002

10003,4003

10004,4004

*Element, type=Mass, elset=mbogie

10020, 6001

10021, 6004

*Element, type=Mass, elset=mcarbody

10030, 6501

*Spring, elset=SpringPrimary

2 ,2

1.17e+06

*Spring, elset=SpringSecondary

2 ,2

1.89e+05

*Dashpot, elset=DashpotPrimary

2 ,2

19600.

*Dashpot, elset=DashpotSecondary

2 ,2

40000

*MASS, elset=mWheel

2100

*MASS, elset=mbogie

2600

*MASS, elset=mcarbody

26100

*Element, Type=Rotaryi, ElSet=IBogie

10501,6001

10502,6004

*Element, Type=Rotaryi, ElSet=ICarbody

10509,6501

*Rotary Inertia, elset=IBogie

2106,1424,2600,0,0,0

*Rotary Inertia, elset=ICarbody

84.56e+03,1278.9e+03,1107.73e+03,0,0,0

*Element, type=RB2D2, elset=Bogie1

9001,5001,6001

9002,6001,5002

*Element, type=RB2D2, elset=Bogie2

9003,5003,6004

9004,6004,5004

*Rigid Body, Elset=Bogie1, Ref Node=6001, Position=Input, PIN Nset=Bogie1Nodes

*Rigid Body, Elset=Bogie2, Ref Node=6004, Position=Input, PIN Nset=Bogie2Nodes

*Element, type=RB2D2, elset=Car1

9501,6002,6501

9502,6501,6003

*Rigid Body, Elset=Car1, Ref Node=6501, Position=Input, PIN Nset=Carbody1Nodes

*BOUNDARY

AppGroundNodes_Left,Encastre

AppGroundNodes_Right,Encastre

401,2

433,PINNED

544,PINNED

576,2

2429,1

3204,1

WheelNodes,1,1

6001,1,1

6004,1,1

6501,1,1

** Interaction: ContactCondition

*Contact Pair, interaction=ContactProp

slave, master

**STEP:gravity

**

*Step, name=gravity

*Static

**

** LOADS

**

** Name: Gravity-1 Type:Gravity

*Dload

 , GRAV, 10., 0., -1.

**

** OUTPUT REQUESTS

**

** FIELD OUTPUT: F-Output-1

**

*Output, field, variable=PRESELECT

**

** HISTORY OUTPUT: H-Output-1

**

*Output, history, variable=PRESELECT

*End Step

**------------------------------------------------------------------

** 

**Step: Step-2-dynamic

**

*Step, name=Step-2-dynamic, inc=18896

*Dynamic, alpha=-0.05,direct

0.0005,9.198

** 

** BOUNDARY CONDITIONS

*Boundary

WheelNodes,1,1,511

6001,1,1,511

6004,1,1,511

6501,1,1,511

** 

** OUTPUT REQUESTS

** 

** 

** FIELD OUTPUT: F-Output-2

** 

*Output, field, variable=PRESELECT

** 

** HISTORY OUTPUT: H-Output-1

** 

*Output, history, variable=PRESELECT

*Node output, nset=BridgeNodes

A2,U2

*NODE PRINT, nset=BridgeNodes

A2,U2

*END STEP