Construction Moving Load [STG]
The Construction Moving Load feature allows users to define the loads that occur during deck construction. It generates the moving construction live loads (finishing machine, construction live load on the deck and near the deck edge) and the static construction dead loads (removable deck formwork carried on overhang brackets) from a few parameters.
Users can specify the number of positions for the finishing machine, and loads will be generated automatically over the girders with even spacing. The envelope for these positions is created automatically, enabling users to view critical loading values for each girder without needing to define a result extraction case.
Construction DL / LL separation. Construction load combinations assign different load factors to construction dead and construction live loads, so the object keeps the two classes in separate stages and exposes three result cases:
Pick ConstructionDL and ConstructionLL as separate rows of a combination when the factors differ. Do not add MovingLoadEnvelope to the same combination row as the new cases — it already contains both classes, so combining them double-counts.
The moving loads are applied in the automatically generated per-position sub-stages (load type Const. Live). The static loads are applied once, in a dedicated StaticLoadStage (load type Const. Dead) that is created only while a static surface load is entered.
ConstructionLL
Critical envelope of the per-position moving loads (finishing machine, line and surface live loads)
ConstructionDL
The static formwork / overhang-bracket loads
MovingLoadEnvelope
Envelope of the per-position totals (moving + static) — the original, combined result
When modeling with sequential deck pouring, if the deck is poured in multiple stages over the selected girders, using a single construction live load is sufficient for the those girders. This can be accounted for during the result extraction process. For non-composite dead loads, critical loading must be identified using the Envelope option across all construction stages prior to reaching the composite state (Figure 1a). These loads are then combined in the limit state with the automatically generated result extraction from the construction live load (Figure 1b).
General
Stage: Choose the stage at which to apply the construction loads. Note that analysis results cannot be visualized within this stage after the analysis is complete. OpenBrIM automatically generates sub-stages and assigns the selected stage as the prior stage, so analysis results will be presented in these sub-stages.
Left Exterior Girder: Specify the left exterior girder in the direction of the PGL.
Right Exterior Girder: Specify the right exterior girder in the direction of the PGL.
Loadings will be generated between the left and right exterior girders.
Specify Position as [Number of Positions/Station List]: This parameter determines how the position is specified.
Number of Positions: Specify the number of load placements centered along the girder length for the finishing machine. The minimum number of positions allowed by the software is two. These loads are created as sub-stages by OpenBrIM and placed along the length of the girders.
Station List: This parameter is used to organize the list of stations. Please note that the station is measured along the PGL. The Moving Load is centered between the left and right exterior girder lines. Therefore, the station input must be entered accordingly, as shown in the image below.
Moving Loads
The moving loads are the construction live loads. They travel with the finishing machine position and are reported through the ConstructionLL envelope (and, combined with the static loads, through MovingLoadEnvelope).
Moving Point Load (Exterior Girders): Specify the magnitude of the point load to be applied to the exterior girders. This load can represent the loading in Section 2.13.1 Category A of the FDOT Structures Manual 2024 (Figure 3).
Point Load Distance to Exterior Girder: Specify the eccentricity of the point load from the center of the top flange of the nearest exterior girder.
For Steel I-Girders: Measure the distance from the centerline of the top flange to the line load.
For Tub Girders: Measure the distance from the centerline of the exterior flange to the line load.
Moving Line Load (Exterior Girders): Specify the magnitude of the line load to be applied to the exterior girders. This load can represent the loading in Section 2.13.1 Category D of the FDOT Structures Manual 2024 (Figure 4).
Line Load Distance to Exterior Girder: Specify the horizontal distance (eccentricity) between the line load and the exterior flange of the nearest exterior girder:
For Steel I-Girders: Measure the distance from the centerline of the top flange to the line load.
For Tub Girders: Measure the distance from the centerline of the exterior flange to the line load.
Line Load Length: Specify the length of the line load.
Moving Surface Load (All Girders): Specify the magnitude of the surface load applied to both the exterior girders and the interior girders. The load is centered between the selected two girders. This load can represent the loading in Section 2.13.1 Category B of the FDOT Structures Manual 2024 (Figure 4).
Surface Load Length (Longitudinal Direction): Specify the length of the surface along the PGL.
Surface Load Width (Transverse Direction): Specify the width of the surface, which is perpendicular to the PGL.
Static Loads
The static loads are the construction dead loads — the removable deck formwork and its overhang brackets. They do not move with the finishing machine: they are applied once, in a dedicated sub-stage typed Const. Dead that exists only while a static surface load is entered, and are reported through the ConstructionDL result case (and, combined with the moving loads, through MovingLoadEnvelope).
Static Surface Load (Exterior Girders): Specify the magnitude of the static surface load applied only to the exterior girders. This loading is not a moving load — it is applied once along the full girder length rather than per finishing-machine position. For tub girders, the load is applied to the exterior flanges of the selected girders. This load can represent the loading in Section 2.13.1 Category C of the FDOT Structures Manual 2024 (Figure 4).
Static Surface Load Width (Transverse Direction): Specify the width of the static surface load. Since the length of the static surface load is predefined along the girder, no input is necessary for the longitudinal direction.
Overhang Bracket Incline Angle from Vertical: Specify the incline of the overhang bracket measured from vertical. The horizontal component of the bracket reaction varies with the tangent of this angle, so the value must stay between -89 and +89 degrees (default: 0).
Distance from the Surface Load Center to the Exterior Girder: Specify the horizontal distance (eccentricity) between the center of the surface load and the exterior flange centerline of the nearest exterior girder:
For Steel I-Girders: Measure the distance from the centerline of the top flange to the center of the surface load.
For Tub Girders: Measure the distance from the centerline of the exterior flange to the center of the surface load.
This parameter is used to compute the moment generated by the surface load.
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