Moving Load Analysis Control

Select the material and the bridge type for the calculation of Dynamic factor as per the Russian Moving Load Code. Dynamic Factor can be defined in the Vehicles dialog box.

Select the bridge type as Rail Road Bridge, Subway, Tram or Rail Road Bridge, Subway, Tram ( Main Truss Only) or Rail Road Bridge, Subway, Tram ( Combined Bridge) for Steel and SRC type of material and Rail Road Bridge, Subway, Tram or Rail Road Bridge , Subway, Tram for RC.

Truck/Train Load Control Option

Set the method of performing moving load analysis using vehicular loads and the method of applying loads.

Analysis Method
Set the moving load analysis method.

Load Point Selection
Set the selection method for application location of vehicular loads.

Influence Line Dependent Point
This is a method which controls the vehicular loads in a moving load analysis according to the influence values.

Maximum value(+): From the locations of the applied loads only the loads that result in positive influence values are used in the computation.

Minimum value(-): From the locations of the applied loads, only the loads that result in negative(-) influence values are used in the computation.

This method is used for general vehicular loading and yields results larger than that from the All Points method because the loads are controlled according to the influence values.

All Points
This is a method which analyzes the structure for applied vehicular loads in the moving load analysis at all locations without controlling the influence values.

The method is used for train loading and yields results smaller than that from the Influence Dependent Point method because the loads are not controlled according to the influence values.

Number / Line Element
Assign the number of reference points on a line element for moving loads and drawing influence line in an influence line analysis. The accuracy of results increases with the increase in the number, but the analysis time may be excessive. If the length of beam element assigned with traffic line lane or plate elements assigned with traffic surface lane is large, then the "Influence Generating Point No. / Line Element" should be increased for more accurate analysis.

Distance between Points: Assign the distance between the consecutive reference points on a line element for moving loads. The accuracy of results will increase if the distance between the points decreases, but the analysis time will increase. The user can manage the time and accuracy by choosing the appropriate distance.

Analysis Results

Set the position of the elements for which the moving load analysis results are calculated.

Plate
For plate elements, member forces per unit length are calculated as a result of moving load analysis. The form of member force results is selected from below.

Center: Calculate the member forces per unit length with respect to the centers of the elements and the output results are produced for the entire elements.

Center + Nodal: Calculate the member forces per unit length with respect to the element centers and the nodes constituting the elements and produce the results accordingly.

Stress Calculation: Assign whether or not to calculate the stresses of plate elements.

Concurrent Force: Calculate the corresponding moments under the conditions where the maximum and minimum axial forces occur at each position. Similarly, calculate the corresponding axial forces under the conditions where the maximum and minimum moments occur at each position. The results are then produced.

Note 1
The following codes are provided for Plate Concurrent Force:
[AASHTO Standard, AASHTO LRFD, AASHTO LRFD (PENNDOT), Canada, BS, EUROCODE, Australia, Poland]
Also available are Japanese, Taiwanese and Korean Codes

Note 2
How to view Concurrent Force :
Menu - Results - Tables - Results Tables - Plate - Force&Stress - Plate Force(UL:Local & UCS)
- 'Click Right button on the mouse' - View by Max Value Item.

Frame
The moving load analysis results for Frame elements are produced in the form of member forces pertaining to 5 Points of each member. The form of member forces is selected from below.

Normal + Concurrent Force: Calculate the member forces at 5 Points of the beam elements. Calculate the corresponding moments under the conditions where the maximum and minimum axial forces occur at each position. Similarly, calculate the corresponding axial forces under the conditions where the maximum and minimum moments occur at each position. The results are then produced. To produce the results in a table format, go to Result Tables > Beam > Force, right-click and select View by Max Value Item.

Combined Stress Calculation: Assign whether or not calculate the combined stresses of frame.

Calculation Filters

Reactions
Select and enter the supports where the moving load analysis results related to reactions are to be obtained.

All: Select all supports.

Group: Use the Group identified in the model, and enter the supports in the Group.

Displacements
Select and enter the nodes where the moving load analysis results related to displacements are to be obtained.

Forces/Moments
Select and enter the elements where the moving load analysis results related to member forces are to be obtained.

Select the bridge type for the automatic calculation of the impact factor. When the user defines a Traffic Line Lane with an Impact Factor, midas Civil will ignore this option.

• For Class A, Class B or user-defined wheeled vehicle loading (Span between 3m and 45m)

Impact factor fraction for the RC bridge type =

Impact factor fraction for the Steel bridge type =

where L is length in metres of the span as specified in Clause 211.5 of IRC: 6-2000

• For Class AA, Class 70R, Class 40R or user-defined wheeled/tracked/bogie vehicle loading

(Spans less than 9m)

Impact percentage of tracked vehicles: 25% for spans up to 5m linearly reducing to 10% for spans of 9m

Impact percentage of wheeled vehicles: 25%

(Spans of 9m or more)

- RC bridge type

Impact percentage of tracked vehicles: 10% up to a span of 40m and in accordance with the curve in Fig.5 of IRC: 6-2000 for spans in excess of 40m

Impact percentage of wheeled vehicles: 25% for spans up to 12m and in accordance with the curve in Fig.5 of IRC: 6-2000 for spans in excess of 12m

- Steel bridge type

Impact percentage of tracked vehicles: 10% for all spans

Impact percentage of wheeled vehicles: 25% for spans up to 23m and in accordance with the curve indicated in Fig.5 of IRC: 6-2000 for spans in excess of 23m

Tracks: Select whether the bridge will carry single, double or multiple tracks. This detail is used in calculation of Coefficient of Dynamic Augmentation (CDA) as per IRS Bridge rules under clause 2.4.

Type 1: Classification as per IRS Bridge rules clause 2.3.4.2. Single sleeper under both rails at a location

Type 2: Classification as per IRS Bridge rules clause 2.3.4.2. Single sleeper sear under each individual rail at a location

Select the maximum number of successive vehicles considered for moving load analysis. A low number is suggested to decrease the Moving Load Analysis time.