Stages [FEA]

Stage

Prior Stage: The continuity of stages is maintained using the prior stage parameter, which instructs the software on which stage to analyze next. For the first stage, the prior stage will be none. If users wish to apply temporary loads like wind or live load, they can select the final permanent load stage as the prior stage for all transient loads.

Construction Day: The construction day of the stage is utilized in conjunction with the casting day of the element to determine the age of the element. The age of the element is then employed in time-dependent codes such as CEB-FIP 1990.

Temperature: Temperature during curing.

Humidity (%): Relative humidity during curing.

Construction Method[none/equal/match]: Usually, node coordinates are utilized as user inputs without any modification. However, certain scenarios require adjustments to the node locations based on prior stage deflections. For example, during the construction of girders and the application of deck load, girder nodes experience displacement while deck nodes do not. In construction site scenarios, the deck formwork also undergoes deflection due to girder displacement. To address this, the node coordinates of the deck must be adjusted based on girder displacements. The "equal" parameter modifies the initial node coordinates of the deck shell elements by applying the top node displacements of the girder to the closest nodes. For a typical steel I-girder bridge, pier construction, steel I-girder construction, load application on deck, and transient load stages will typically be defined with the "none" parameter. However, the stage that represents the deck construction (the deck hardens stage) should be defined with the "equal" parameter. The match cast technique is typically not used in the construction of steel I-girder bridges and is generally applicable to segmental bridges.

Is Active[Yes/No]: Users can deactivate specific stages to expedite the model's runtime, especially if they are interested in something from the earlier stages. However, if the deactivated stages negatively affect the continuity of stages, the staged construction analysis will fail to run successfully. Therefore, when users deactivate certain stages, they must ensure that all active stages' prior stages are still active.

Load Type: Selecting the appropriate load types, such as dead load, wearing surface load, and wind load, for each stage is crucial, and different load types should not be combined in a single stage. In the following steps, users must combine the results of each stage based on their load type using AASHTO load factors before code checks. Combining results becomes more challenging if more than one load type is applied in one stage or if load types are not selected correctly. In summary, load type allows users to filter results according to its load type, providing a way to organize and analyze results more effectively.

Time Dependent

Time Dependent Code: At present, only the CEB-FIP 1990 code is supported. If any other code is required, please contact the support team, and it can be added to the OpenBrIM Library.

Time Dependent Elastic Modulus[Include/Ignore]: The time-dependent modulus of elasticity is a parameter used to account for the change in elastic modulus over time due to creep and shrinkage for concrete. When the time-dependent modulus of elasticity is included, the modulus of elasticity values entered under basic tab are overridden based on the computed values. According to CEB-FIP 1990, the following parameters are used to compute the time-dependent modulus of elasticity:

1. Concrete compressive strength at 28 days (fcm)

2. Cement hardening type

3. Relative humidity and temperature during curing

4. Age of concrete at time of loading (t)

These parameters are used to calculate the elastic modulus at different times during the life of the concrete member. In OpenBrIM, all calculations are based on the secant modulus of elasticity. However, CEB-FIP computes the tangent modulus. Once the tangent modulus is obtained using the CEB-FIP procedure, OpenBrIM divides the E value by 1.05 before utilizing it in finite element analysis (FEA). To ensure that this effect is included in the analysis, both the material and stage settings should be selected to include it.

Concrete Creep Effect[Include/Ignore]: Concrete creep is a time-dependent deformation of concrete under sustained load. The CEB-FIP model considers several parameters to determine the creep coefficient, which is used to calculate the time-dependent deformation of the concrete. These parameters include the concrete compressive strength at 28 days (fcm), maximum aggregate size (Dmax), cement type and percentage of cement content, relative humidity and temperature during curing, age of concrete at time of loading (t), and applied stress level (σ). OpenBrIM monitors stress changes at each stage and calculates creep accordingly by utilizing these parameters. To ensure that this effect is included in the analysis, both the material and stage settings should be selected to include it.

Concrete Shrinkage Effect[Include/Ignore]: Concrete shrinkage refers to the reduction in the volume or size of concrete over time due to the loss of moisture. When concrete is first poured, it contains a lot of water which evaporates gradually over time causing the concrete to shrink. This can result in cracks or deformations in the concrete which can affect its structural integrity. The parameters used in CEB-FIP for concrete shrinkage are the age at loading, the age at unloading, the duration of loading, the humidity of the environment, and the type and composition of the concrete mix. Additionally, CEB-FIP also considers the influence of creep on shrinkage. To ensure that this effect is included in the analysis, both the material and stage settings should be selected to include it.

Steel Relaxation Effect[Include/Ignore]: To account for relaxation effects in tendons, time-dependent material property definitions are assigned to the relevant materials. To ensure that this effect is included in the analysis, both the material and stage settings should be selected to include it.

PT Losses from Structure[Include/Ignore]: Elastic shortening losses refer to the reduction in the length of a prestressed concrete member caused by the initial stress generated during the pre-tensioning process or other external loads that could alter the length of the member. To account for this effect in the analysis, it is essential to select both the material and stage settings that include it.

Creep of Tensile Axial Force[Include/Ignore]: By default, creep phenomena is only applicable to compression. However, in situations where the compression force decreases due to tension at any stage, the creep effect should be reversed. Incorporating this can assist in addressing such cases.

Nonlinear

Nonlinear:

Maximum # of Iterations:

Force Tolerance: