Function
- Enter the traffic surface lanes for moving load analysis.
The moving load input is applied as a vertical load at the intersection points on the lane surface. Therefore, it is essential to ensure that there are intersection points within the lane surface. If there are no intersection points within the defined lane surface, the moving load will not be applied, and to obtain accurate analysis results, it is necessary to sufficiently divide the elements within the influence area.
- (Refer to "Moving Load Analysis for Bridge Structures" in the "Analysis for Civil Structures" manual)
Call
From main menu, select [Load] tab > [Type : Moving Load] > [Moving Load Analysis Data] group > [Traffic Surface Lane]
Input
To add or create a new lane surface, click the button and enter the required information. If you wish to modify an existing lane surface, select the target and click the
button. To delete a lane surface, click the
button. Clicking the
button will display the selected lane surface points on the screen.
To copy a lane surface, select the desired lane surface and click the button.
When KSCE-LSD15 is selected
Define Design Traffic Surface Lane dialog box
Lane Name
Enter the name of a traffic surface lane.
Traffic Lane Properties
Lane Width
Enter the width of a traffic surface lane.
Wheel Spacing
Enter the spacing between the wheels. For influence line analysis, the program automatically applies a load equal to "load ÷ of wheels" to each wheel.
| Truck load | Lane load |
In the case of Influence Line Analysis, the lane load is redistributed as segment loads along the wheel positions by dividing the unit load per unit length by 2, resulting in a distributed line load. In the case of Influence Surface Analysis, the lane load is redistributed as distributed surface load within the lane surface area, again by dividing the unit load per unit length by 2. Additionally, for the truck load considered in the lane load, the load magnitude is divided by 2 and applied at the wheel positions.
Offset Distance to lane center
Enter the distance from the line of traffic lane nodes to the center of the traffic surface lane. Viewing towards the moving direction of the traffic surface lane, a positive eccentricity (+) refers to an offset to the right from the traffic lane nodes and a negative eccentricity (-) refers to an offset to the left from the traffic lane nodes.
Skew
Enter the skewed angles at the start and end of the bridge referring to the diagram.
Traffic Lane Optimization
Traffic Lane Optimization is an option in midas Civil that allows for transverse optimization of the lane. When this option is selected, the software automatically redistributes the vehicle loads laterally within the lane width and determines the most unfavorable load application positions.
During the analysis, the software automatically applies loads at the center position of the lane width and at the left and right positions with lateral eccentricity. It then evaluates the transverse effects on each element that receives the load and identifies the most critical transverse effects.
The defined vehicle position is at the center of the lane width.
Additionally, the considered vehicle positions are on the left and right sides.
Moving Direction
Specify the direction of vehicle load consideration. In cases where the vehicle load differs between the front and rear wheels, such as with the DB load in bridge design standards, there may be differences in the results depending on the direction.
Forward : Consider the direction from the Start to End only.
Backward : Consider the direction from the End to Start only.
Both : Consider the direction from the End to Start only.
Selected by
Specify the method of defining a lane surface using a lane vertex sequence.
2 points
Beam elements in a line defined by 2 points are assigned as traffic surface lane elements. The first point becomes the Start point.
Picking / Number
Assign the traffic surface lane elements with the mouse. The location of the first-assigned element becomes the Start point.
A lane surface is determined by a lane vertex sequence, an offset distance, and a lane width. Specifically, the lane center is defined at a distance equal to the offset from the lane vertex sequence. From the lane center, the lane surface is defined by extending it half of the lane width in both directions along the direction of travel.
Operations
The data entry is reflected when Selection by Number is selected.
Add : Add the selected node to the lane vertex sequence.
Insert : Insert the selected node at an arbitrary position in the existing lane vertex sequence.
Delete : Delete the selected node from the lane vertex sequence.
In accordance with the Design Standard for Highway Bridges (Limit State Design Method), the impact factor and span start that were previously considered in the definition of lane loads are not relevant. Instead, the application of impact load coefficients varies based on the structural components of the elements, as specified in Section 3.7.1 of the Korean Design Specification for Highway Bridges.
In accordance with the Design Standard for Highway Bridges (Limit State Design Method), the impact factor and span start that were previously considered in the definition of lane loads are not relevant. Instead, the application of impact load coefficients varies based on the structural components of the elements, as specified in Section 3.7.1 of the Korean Design Specification for Highway Bridges.
When Korea is selected
Define Design Traffic Surface Lane dialog box
Lane Name
Enter the name of a traffic surface lane.
Traffic Lane Properties
Lane Width
Enter the width of a traffic surface lane.
Wheel Spacing
Enter the spacing between the wheels. For influence line analysis, the program automatically applies a load equal to "load ÷ of wheels" to each wheel.
| DB load | DL load |
In the case of influence line analysis, the distributed load of the dead load (DL) is divided by 2 per unit length and applied as segmental distributed load at the wheel positions. In the case of influence surface analysis, the DL is applied as a surface distributed load within the lane surface area.
The concentrated loads (Pm and Ps) included in the DL are divided by 2 and applied at the wheel positions. Ideally, the Pm and Ps loads should be applied as segmental distributed loads perpendicular to the lane. However, in influence line analysis using beam elements, it is not possible to consider the distribution of loads perpendicular to the influence line. In influence surface analysis using plate elements, the Pm and Ps loads are currently divided by 2 and applied at the wheel positions. The functionality of applying these loads as segmental distributed loads will be upgraded in future versions.
Offset Distance to lane center
Enter the distance from the line of traffic lane nodes to the center of the traffic surface lane. Viewing towards the moving direction of the traffic surface lane, a positive eccentricity (+) refers to an offset to the right from the traffic lane nodes and a negative eccentricity (-) refers to an offset to the left from the traffic lane nodes.
Impact Factor
Input the impact factor for the specified lane surface.
Skew
Enter the skewed angles at the start and end of the bridge referring to the diagram.
Moving Direction
Specify the direction of vehicle load consideration. In cases where the vehicle load differs between the front and rear wheels, such as with the DB load in bridge design standards, there may be differences in the results depending on the direction.
Forward : Consider the direction from the Start to End only.
Backward : Consider the direction from the End to Start only.
Both : Consider the direction from the End to Start only.
Selected by
Specify the method of defining a lane surface using a lane vertex sequence.
2 points
Beam elements in a line defined by 2 points are assigned as traffic surface lane elements. The first point becomes the Start point.
Picking / Number
Assign the traffic surface lane elements with the mouse. The location of the first-assigned element becomes the Start point.
A lane surface is determined by a lane vertex sequence, an offset distance, and a lane width. Specifically, the lane center is defined at a distance equal to the offset from the lane vertex sequence. From the lane center, the lane surface is defined by extending it half of the lane width in both directions along the direction of travel.
Operations
The data entry is reflected when Selection by Number is selected.
Add : Add the selected node to the lane vertex sequence.
Insert : Insert the selected node at an arbitrary position in the existing lane vertex sequence.
Delete : Delete the selected node from the lane vertex sequence.
Span Start
In the case of continuous bridges with multiple spans, the starting element for each span is selected to distinguish between spans. This functionality is used in the calculation of the maximum negative moment due to the dead load (DL) in continuous bridges.
Moving Load Optimization(AASHTO Standard, AASHTO-LRFD, PENNDOT, Canada, BS, Eurocode, Russia)
Transverse moving load optimization dialog box
To initially input or add a lane surface, click the button and enter the necessary information. If you want to modify an existing lane surface, select the target surface and click the
button. To delete a lane surface, click the
button. When you click the
buttons, the designated lane vertex sequence will be highlighted on the screen.
If you want to copy a lane surface, select the desired surface and click the button.
Define moving load optimization
Lane Name
Enter the name of a traffic surface lane.
Traffic Lane Optimization Properties
For each lane element, enter the eccentricity and impact factor.
Optimization Lane
Enter the lane width for applying transverse optimization.
Lane Width
Enter the width of the lane.
Anal. Lane Offset
Enter the offset distance to be increased from the vehicle centerline in the transverse direction.
Wheel Spacing
Enter the spacing between wheels. When analyzing the influence line, each wheel position is subjected to a load of 0.5P.
| Truck load | Lane load |
Margin
Enter the minimum distance between the lane boundary and the axle.
Offset Distance to Lane Center
Enter the eccentricity distance for the lane element. A negative (-) value indicates eccentricity in the left direction, while a positive (+) value indicates eccentricity in the right direction.
Moving Direction
Specify the direction of vehicle load consideration. In cases where the vehicle load differs between the front and rear wheels, such as with the DB load in bridge design standards, there may be differences in the results depending on the direction.
Forward : Consider the direction from the Start to End only.
Backward : Consider the direction from the End to Start only.
Both : Consider the direction from the End to Start only.
Selected by
2 Points : When two point coordinates are entered, the beam element on the line connecting the points is designated as the lane element. The first entered point is considered as the start point.
Picking : Use the mouse to select the elements corresponding to the lane. The initially selected element's position is considered as the start point.
Number : Enter the number of the element corresponding to the lane. The initially selected element's position is considered as the start point.
Operations
If Selection by Number is chosen, the entered information will be applied.
Add : Assign the eccentricity distance and impact factor to the selected lane element and input it as a lane element.
Insert : Insert the selected lane element in the middle of the already input lane elements.
Delete : Select and delete the lane element from the dialog box at the bottom.
Lane inputs should be entered sequentially along the vehicle's path. If elements are selected using 2 Points or Picking, there is no need to click the or
buttons.
Example