Grasshopper Template : FCM Bridge

Download File

FCM Bridge.zip

0.Introduction

 The purpose of this chapter is to make the various features of MIDAS GH more accessible by structuring the content in a way similar to practical examples. This approach aims to help users who may have struggled to learn through manuals to intuitively understand the use of Grasshopper and CIVIL_NX APIs. The primary goal is to support users in learning more effectively and systematically.

 This template is designed to help practitioners efficiently and systematically execute their projects.

 In this example, we will learn how to input everything from the basic geometry to the Construction Stage using the FCM Bridge.

Result Preview

1. Overview

1-1 Recommended Versions

 The required versions of MIDAS GH and CIVIL NX for proper use of this template are as follows:

 If the versions do not match the ones listed above, some features may not function correctly.

 For proper functionality, if you are using lower versions, please update to the versions specified or higher.

1-2 Unit System Settings

 This template is configured with the following unit system:

1-3 Model Overview

• Material Properties and Allowable Stress
  • Pier properties
    fc' = 5.0ksi, ASTM(RC), Grade C5000
    
    
  • Main Girder properties
    fc' = 4.0ksi, ASTM(RC), Grade C4000
    
    
  • Tendon Properties
    Material: EN 05(S) Y1770S7
    P.C Strand: Φ15.2 mm (0.6˝strand)
    Duct Diameter: 100 mm
    Yield Strength: f_py = 1600 N/mm²
    Ultimate Strength: f_pu = 1850 N/mm²
    Cross Sectional area: A_p = 2635.3 mm²
    Modulus of Elasticity: E_ps = 2.00 X 10⁵ N/mm²
    Jacking Stress: f_pj = 0.7f_pu = 1295 N/mm²
    Curvature friction factor: μ = 0.2 /rad
    Wobble friction factor: k = 0.006 /m
    Anchorage Slip: Δs = 6 mm (At the Beginning and at the End)

• Load

   Self-weight : Input Self-Weight

   2nd Dead Load : w = 35 kN/m 

   Form Travelling Load : P = 800kN , e = 2.5m , M = P x e = 2,000 kN·m

  

   Curing Load : Non harden Concrete Weight

• Creep and Shrinkage

  Code: CEB-FIP(1990)
  Characteristic compressive strength of concrete at the age of 28 days: 35 N/mm2(Grade C5000). / 28 N/mm2(Grade C4000)
  Relative Humidity of ambient environment: 70%
  Type of cement: Normal or rapid hardening cement
  Age of concrete at the beginning of shrinkage: 3 days

• Construction Stage

The following outlines a general procedure for FCM construction

This example is a 3-span FCM bridge constructed with 4 Form Travelers (FT).  As such FT will not be relocated.

2. Execution

2-1 Setting

Before generating the model, Midas GH requires the following settings:

A. API Connection
B. Template Execution

A. API Connection

 MIDAS GH operates using the API of CIVIL NX.
 Therefore, the developed components will function correctly only when they are connected to CIVIL NX.
 The steps to connect to CIVIL NX are as follows:

  ① Run the Midas Setting component in Grasshopper.
  ② Double-click the Midas Setting component icon to open the Settings window.
  ③ Execute API Settings in CIVIL NX.
  ④ Copy the content of Base URL from CIVIL NX and paste it into the Base URL field in Grasshopper.
  ⑤ Copy the content of MAPI-Key from CIVIL NX and paste it into the MAPI-Key field in Grasshopper.
  ⑥ Click the Connect button in CIVIL NX.
  ⑦ Click the OK button in the Midas Setting window in Grasshopper.

B. Open Template File

 Once the settings are complete, open the downloaded template file.

Additionally, to create tendons, you need to run the downloaded Rhino file along with this template.

2-2 Work Flow

MIDAS GH creates modeling in CIVIL NX through the following process:

A. Generate Geometry in Grasshopper

B. Use MIDAS GH Components to Transfer Geometry to CIVIL NX

 MIDAS GH components are used to create geometry in CIVIL NX, each accepting various input variables.

① Create a line in Grasshopper, then use the Beam component in MIDAS GH to build the model.

② For sections, combine the Outer-Dimension of PSC Shape and Inner-Dimension of PSC Shape components to create a PSC shape. Then, connect these to the Tapered Shape component to generate a Tapered PSC Shape.

③ Connect the completed Section Property, Material Property, and Geometry to the Beam component to create the model in CIVIL NX.

④ To establish relationships with substructures and set constraints with the foundation, use the Get Property component from the created modeling component to extract Node and Element IDs for the input locations.

⑤ Similarly, for loads, input Node and Element IDs along with the load values.

⑥ To accommodate construction stages later, configure Structure Groups, Boundary Groups, and Load Groups and input them simultaneously.

⑦ For tendons, this template utilizes tendons imported from drawings into Rhino.

⑧ The imported tendons are transformed into coordinates suitable for the bridge using Grasshopper, and the corresponding elements are identified and assigned accordingly.

⑨ Once the input for the complete structure is finished, create construction stages and set durations for each stage.

⑩ Assign the groups configured in Step ⑥ to the respective construction stages to input the construction stage process.

For detailed instructions on how to use the components, please refer to the manual.
GrassHopper API Online Manual – MIDAS Support

C. Convert MIDAS GH Components to Data for CIVIL NX API

The input components are converted into data compatible with the CIVIL NX API.

D. Send API Data in Batch Using Merge and Builder Components

While each MIDAS GH component has its own API execution button, Merge and Builder components are used for efficient modeling to send API data in batches.

E. Run the Model in CIVIL NX

When the Run button is executed, the model is generated in CIVIL NX.

2-3 Run Component

A. Important Notes

a. API Connection When Running Grasshopper
 -> If the template is executed without API connection, components may not function properly, and the data in the Builder component could become disconnected.

In this case, press the Recalculating Button to re-execute all components.
If the Merge component and Builder component are still disconnected, reconnect them manually.

b. Geometry Modifications

 -> When the geometry is changed, discrepancies may arise between the modeling information generated in CIVIL NX and the data calculated within Grasshopper.

To ensure proper updates, press the C.Data Matching button to synchronize the modeling information.

c. Deactivating Intermediate Components

 -> For efficient work in Grasshopper, components that require long computation times are sometimes deactivated and reactivated after the task is completed.
 In such cases, components following the deactivated ones will not function, causing data to be missing in the Merge component, resulting in the API output disappearing.

In this case, the connection between the Merge component and the Builder component may become disconnected.

After reactivating the deactivated components, ensure to reconnect the Merge and Builder components.

B. Template Execution

3. Description

 This template consists of a total of seven sections:
① Modeling, ② Property, ③ Boundary, ④ Static Load, ⑤ Prestress, ⑥ Construction Stage, and ⑦ Update.

 Their locations are as follows:

Additionally, in this template, the data that users can modify is marked in purple on the overall component map.

 When the Parameter values in these areas are adjusted, the modeling information will be updated accordingly.

 Please refer to the following details for guidance.

3-1 Modeling

The following information is configured as part of the structural modeling details:

A. Arrangement

 Set the bridge path.

B. Pier Table

The following information is configured as part of the Pier Table details:

a. Pier Point

Specify the position of the bridge's substructure.

b. Pier Distance

Define the distance between the Pier Center and Pier Point.

c. Distance to End of Pier Table

Set the distance from the end of the Pier Table to the Pier Center.

C. FSM

The following information is configured as part of the FSM details:

a. FSM Length

Configure the length of the FSM section.

b. FSM Divide Count

Set the number of elements in the FSM section, excluding the Abutment Support section.

The S4 (Element Length) is determined based on the number of elements.

c. Abutment Support Length

Define the length of the Abutment Support section.

d. Abutment Divide Count

Specify the number of elements in the Abutment Support section.

D. Key Segment

The following information is configured as part of the Key Segment details:

a. Key Segment Length

Set the length of the Key Segment section.

E. Segment

The following information is configured as part of the Segment details:

a. Segment Length

Configure the length of a single segment.

b. Equal-interval Options

• True : Segments are divided into equal lengths, approximating the specified length.
• False : Segments are divided as per user-defined lengths. If the total length cannot be evenly divided, the last segment’s length is adjusted.

F. Pier

The following information is configured as part of the Pier details:

a. Pier Length

Set the total length of the pier.

b. Divide Count

Define the number of elements in the pier section.

G. Structure Group

Separate geometry into groups for Construction Stage settings.

The template automatically assigns element numbers to groups.

a. Name

Specify the name of the group.

Please refer to the diagram above for the currently configured Group Name.

3-2 Property

Adjust the material and section properties applied to the geometry.

A. Material

Generate the Material Property to be applied to the members.

Note

MIDAS GH utilizes the CIVIL NX database.
Please apply the appropriate database for your use case in each component.

a. Material ID

Assign an ID to each material.

b. Material Name 

Set the name for the material.

c. Modulus of Elasticity

Enter the elastic modulus of the material.

d. Thermal Coefficient

Specify the thermal expansion coefficient.

B. Time Dependent Material

Generate the Time Dependent Material Property to be applied to the members.

a. Relative Humidity

Configure the ambient relative humidity for concrete.

b. Concrete Age

Set the time for drying shrinkage to begin after casting.

c. Member Size

Input the geometric dimensions of the structure.

d. Compressive Strength

Define the 28-day compressive strength.

C. Section

Generate the Section Property to be applied to the members.

a. Section ID

Assign an ID to each section.

b. Section Name

Assign a Name the section.

c. Section Size

Input dimensions for the sections:

d. Section Shape

Choose the shape of the section.

3-3 Boundary

Configure boundary conditions for the bridge.

The template uses CIVIL NX boundary features, allowing users to adjust degrees of freedom and applied values.

A. Support

Apply constraints for the model.

B. Rigid Elastic Link

Apply a rigid connection between two nodes in the model.

C. Boundary Group

Group boundary cases for Construction Stage settings.

a. Name prefix

Specify the prefix for each boundary group.

3-4 Static Load

Apply static loads to the bridge.

A. Load Case

Set the Load Type to be applied during member design.

Enter the Load Case Name as shown below.

a. Name

Specify the name of the load case.

B. Self Weight

Set the factor for self-weight.

a. Self Weight Factor

Set the factor for self-weight.

C. 2nd Load

Input the loads for pavement, barriers, and additional attachments that are not explicitly modeled.

The regions where the loads will be applied are automatically assigned based on the previously defined areas.

a. Load Value

Define additional loads, such as pavement or barriers.

D. Form Travelling Load

Consider the load from construction equipment. For the form traveler, account for both the weight of the equipment itself and the eccentric load based on its working position.

a. Load Value

Specify construction equipment loads.

b. Form Traveller Position

Set the eccentric position of the form traveler.

E. CS Time Load

To reflect the time-dependent material properties caused by age differences between adjacent members, additional age differences are applied to specific members.

The age differences are automatically assigned based on the durations set in 3-6 Construction Stage.

F. Wet Concrete Load

Input the loads for Wet concrete during each construction stage.

The load is calculated by retrieving the cross-sectional information from CIVIL NX and multiplying it by the concrete's density.

Subsequently, the center of gravity of the entire cross-section is computed to account for eccentric loads.

G. Load Group

To set up the Construction Stage, group the same Load Cases into separate Load Groups.

Note

The Load Group Name is generated by combining the Name prefix and the Structure Group Name.

a. Name prefix

Enter the prefix for each Load Group.

b. Name

Input the Load Group Name.
This is used when the Structure Group Name is not referenced.

3-5 Prestress Load

Apply Prestress Load to the bridge.

A. Tendon Property

Input the material properties of the tendon.

The method for applying relaxation can be configured within the component.

a. Tendon ID

Assign an ID to the tendon property.

b. Tendon Name

Assign Name the tendon property.

c. Wire

Input wire details for the tendon.

d. Duct

Define duct size.

e. Friction Factor

Set the friction coefficient value to account for prestress losses.

f. Anchorage Slip

Input the slip amount at the anchorage.

B. Tendon Profile

Configure the shape and placement of the tendon.

 This template uses a method where tendon placement is first created in 3D using Rhino based on drawings, and then positioned appropriately in the model using Grasshopper.

 If the tendon path is curved, creating it in 3D can be challenging. In such cases, the straight path is used as a reference and later adjusted to fit the curved path. Even if the total length of the tendon and the model differ, they are proportionally adjusted to align correctly.

 Thus, as long as the position and length ratio of the tendon on the straight path match, the tendon will be generated correctly in the model.

a. Reference Line Position

Create a reference line based on the tendon’s length.

b. Import File

Import tendon placement data by layer.

c. Tendon Name

Automatically generate tendon names using prefixes and top/bottom settings.

C. Tendon Prestress

Input the Prestress Load for the tendon.

Refer to the diagram below for the direction of prestress application to the tendon.

To change the prestress application position, adjust the order of the values connected to the component.

a. Tendon Jaking Force

Input the prestress force to be applied to the tendon.

b. Grouting Stage

Define the timing for duct grouting after the tendon has been prestressed.

3-6 Construction Stage

Configure construction stages and assign actions for each step.

Construction Step

A. Construction Step

Configure construction stages.

a. Segment Construction Step

Define the total steps for segment construction.

This template automatically calculates and inputs the Max Segment Count.

b. After Segment Consturction Step

Set the number of remaining steps after the segment construction is completed.

B. Duration

 Set the duration for each construction stage.

a. Stage Date

Specify the duration of each stage.

b. Additional Data

Set the period for existing component influence.

This is applied when changing the load application timing or incorporating additional loads within a single construction stage.

In this template, the time required for tasks prior to concrete casting is specified.

c. Connection Date

Configure the period to consider creep effects.

d. Permanent Date

Set the duration to account for the effects of creep.

C. Start CS Step

Define the construction stage to be applied to each member.

For FSM and KeySeg, the stages are set to be applied sequentially after the completion of the segment construction.

D. Deactive Step Interval

Define the duration (steps) during which the loads are applied.

4. Used Components

Component Summary Table

5. Caution

5-1 Not Working Component

When components fail to function while using the template, check the following:

5-2 Modeling Error

If components fail to create a model correctly in CIVIL NX, follow these steps:

If issues persist, contact MIDAS technical support for further assistance.