MOVING LO LOAD AD This type of loading occurs occurs classically when the load-causing load-causing units move on the structure, as in the case of trucks on a bridge deck. The mobile loads are discretized into several individual immobile load cases at discrete positions. Defning the input data There are are 2 stages for specifying specifying these types of loads. Stage 1 is as shown in the eample below. DEFINE MOVING LOAD TYPE 1 LOAD 119.6 10.! 9".# DI$TAN%E DI$TAN%E 1.&& 1.# 1 .# 'IDT( 1. TYPE ) LOAD !".9 !".9 !".9 !".9 DI$TAN%E DI$TAN%E 1.! 1.! 1.! 'IDT( 1.& The above lines represent represent the !rst !rst out of two sets sets of data re"uired re"uired in moving load generation. The type number #1$ is a label for identi!cation of the load-causing unit, such as a truck. % ales # 11&.' 1().% &*.+$ are speci!ed with the / command. The spacing between the ales in the direction of movement #longitudinal direction$ is speci!ed after the /0ST3 command. Since there are % ales, there are 2 spacings between them. 40/T5 is the spacing in the transverse direction, that is, it is the distance between the 2 prongs of an ale of the truck. 6or the T783 2 truck, there are * ales and % spacings. LOAD 1 $ELF Y *1.0 oad case 1 is a static load case. LOAD GENE+ATION &# TYPE 1 *!.)& 0. ". ,IN% 1.# TYPE ) *!.9 0. 6. ,IN% 1.# This constitutes the second second of the two sets of data re"uired re"uired for moving moving load generation. 9+ load cases are generated using the Type 1 and Type 2 vehicles whose characteristics were described earlier. earlier. 6or the !rst of these
load cases, the :, 7 and ; location of the reference load have been speci!ed after ommand Type 1 Type 2 respectively. The : 0ncrement of 1.+ft denotes that the vehicle moves along the : direction and the individual positions which are 1.+ft apart will be used to generate the remaining 9* load cases. The basis for determining the number of load cases to generate, 9+ in the eample above, is as follows < s seen in the Technical =eference manual, the reference wheel is on the last ale. The !rst load case which is generated will be the one for which the !rst ale is >ust about to enter the bridge. The last load case should be the one for which the last ale is >ust about to eit the bridge. Thus, the total distance travelled by the reference load will be the length of the vehicle #distance from !rst ale to last ale$ plus the span of the bridge. et us call this term ?/?. 0f we want the vehicle to move forward in 1.+ feet increments #each 1.+ foot increment will create a discrete position of the truck on the bridge$, it would re"uired #/@1.+A1$ cases to be generated. PE+FO+M ANALY$I$ P+INT LOAD DATA The load generation commands are followed by the 83=6=B 7S0S command. The 8=0T / /T option is used to obtain a report in the output !le of the values and positions of the generated loads.
MOVING LOAD ANALY$I$ -----
Data
N N N N k k k k 0 0 0 0 3 3 3 3
0.50
0.50 0.50
0.3 x 0.6
10.00
/imensions are in metre Torsion is =eleased. 2( increments of oads. o. of oadsC1(.(@(.+(C2(
8rovide 2(A1C21.
oad increment in : incrementC(.+(m. fter veri!cation place the loads before #-$2.(m so that o. of oad DenerationC2+. 1.Ge/et2 3eati/n
New Project
Select Plane
Units:Length
Force=KN; File Name=Moving load Select
Add eam
Finish!
Front view! "lic# Sna$ Node%eam
&dit
Next
=meters;
'()
Plane
' *ight +,m s$acing +m ) *ight
,m
s$acing +m
"lic# -,.,/. -+,.,/ and Press &sc! Switch o00 the grid 1 closing Sna$% Nodal eam! "lic# dimension icon and veri01 the 2eometr1 created! 2. Member Property :
"lic# 2eneral 53=,!6,
Pro$ert1
Add
entire str8ct8re
3e0ine
*ectangle
)3=,!4,
"lose! 7ighlight )3=,!4, 53=,!6, and Select
Assign
to selected eam
Assign )es!
3. Supports :
"lic# S8$$ort
"reate Fixed Add!
7ighlight s8$$ort 9 and
select the nodes 1 windowing 8sing node c8rsor selected nodes
Assign )es "lose 3e
Assign
to
select the nodes and
change to eam c8rsor! 4.Loading :
Main men8
"ommands
Loading 3e0initions
ehicle Load!
6ig.1
Eehicle load ommand
6ig. 2 3ntering vehicle load
ehicle 1$e *e0! + +
Load 6,
width =, 3istance ,!<
9
6, ,!<
6
6, ,!<
6, ,!<
<
6,
"lic# Load case details
Add Add Load
No! o0 Load to e 2enerated=9,
"lose!
2eneration!
Add!
6ig. % o. of load to be generated
7ighlight Load itle 2enerate Load '=,
Load increment
)=,
' increment =,!<
5=, Add
"lose!
6ig.*
3nter /ata for oad generation
No
3e0ine
$rint
Add "lose!
commands Anal1sis res8lts Add "lose.
Note: Save the File and *8n the Program! 6. Analysis:
From Main Men8
>
Anal1sis
*8n
Anal1sis
Select the memer and do8le clic# on it
Shear
3one! ending
"lose!
7. Results :
2o to $ost $rocessing mode! Maximi?e screen! "lic# de0lections
0or vario8s load $osition!
6ig. + oad Deneration for starting case
6ig. ' oad generation for oad Deneration no. 2(
Similarl1 "lic# M? 0or vario8s load $osition!
6ig. 9 FB/ for 3nvelope
"lic# F1 0or vario8s load $osition! A0ter that 2o to Staad editor and edit the in$8t 0ile! Load 2eneration=9< "hange the next line as 0ollows: -@n order to start the 0irst $oint o0 load as 0o8rth load at ?ero starting $oint/
+ (9!, , , Save the 0ile!
6ig. 9 3diting ST/ 6ile for load generationC2+
"lic# Anal1sis
*8n
Anal1sis
3one!
First load to e started at eginning $oint! "lic# Load icon and $ress downward arrow #e1 to move the load 0rom Le0t to *ight! Now 1o8 can see that the last load sto$ e0ore the end o0 the eam! @n order to correct this. go to Staad editor and correct the No! o0 Load to e 2enerated=9< and save the 0ile! "lic# Anal1sis%$rint Anal1sis
*8n
No
Anal1sis
$rint
Add "lose!
done!
2o to $ost $rocessing Mode! Switch on Load icon and move the load 0rom le0t to right!
6ig.) oad position for load generation case o. 2(
)o8 can see the M3. SF 0or vario8s load $osition!
6ig. & =evised FB/ for envelope
