📺Tutorial T01-5 - MasterFrame 3D Steel & Composite Design

Posted on September 15th, 2019 in Getting Started

Summary

The provided text details a step-by-step tutorial on converting an existing 2D steel frame into a comprehensive 3D structure for steel and composite design, adhering to Eurocode 3 and 4.

The tutorial covers preparation, duplication, geometric definition, loading application (gravity and wind), load case management, introduction of structural modifications, and final analysis and design checks.

I. Frame Preparation and 3D Duplication

The process begins by preparing the original 2D frame. This involved:

1. Removing existing loads using the "remove all" option under loads, member loading.
2. Restoring tension-only members that were removed accidentally, applying them to inclined members using filters.
3. Pinning members for a "full simple construction," specifically pinning all members on the lower floors using restraints and releases. Bracing members at the upper level were pinned, and three columns were pinned at the apex and midpoints.
4. Duplicating the frame into 3D by windowing the entire frame. Five copies were made with a shift of 6 meters along the Z axis, ensuring "connecting members" were included.
5. Setting releases and section sizes for the new 3D members. Horizontal members in the north-south direction were selected and set to be fully pinned (release expanded, double-clicked). Section sizes were updated, using a 178 UB for most members and a 125 PFC for the small canopies.
6. Deleting ground beams by looking at the frame on plan and then using the delete modification mode in the front view.

II. Defining Geometry: Grid Lines and Levels

The model's coordinate system was defined by adding grid lines and levels:

• Grid Lines (Horizontal Direction): Set one was defined starting from A.
• Grid Lines (Opposite Direction): Set two was defined using numbering (1, 2, 3, 4, 5, 6) and custom names for the external grid lines: 7 was set as 1A, 8 as 4A, and 9 as 6A.
• Levels: Default Level 1 was already at 3.5m. Level 2 was added at 7 meters. A third level was added, named Roof, with a Y value of 10 meters.
• Creating Views: Automatic generation of views (Level 1, Level 2, Roof) was performed using the geometry and grid lines.

III. Bracing and Geometry Modifications

Bracing members were introduced:

• Vertical Bracing: X bracing was added on grid lines one and six between C and D. They were specified as flats (100x10) of 275 steel, with released ends and tension only, and grouped as "sidewall bracing".
• Internal Bracing Removal: All internal bracing members were subsequently deleted using filters and windowing in the top and front views.
• Roof Bracing: General members were created for roof bracing on the roof plan. These were CHS sections (139x5), released at the ends, and not tension only (dealing with compression and tension). Smaller braces (89x3.6) were added to the canopy . The steel grade for the roof bracing was corrected to 355 steel .

Geometry was adjusted at Level 1 to manage spans :

• Beams were moved horizontally to equalize spans . One row was moved by minus one meter and the opposite side by plus one meter .
• Additional grid lines were added: 3A and 5A .
• New UB members (e.g., 406 by 39, grade 355) were added in the opposite direction on the composite side (Level 1) and copied four times with a shift of minus 6 meters .

IV. Loading Application (Area, Line, Patch, and Wind)

A. Area Loading (Default Gravity Loads)

Area loading parameters were set using floor and roof panels and default loads :

• General Settings: Area loading was applied to slope length, and composite design was enabled .
• Level 1: Slab thickness set to 175 mm, superimposed dead load 0, live load 4 kN (office loading) . Composite properties included a Multi-deck 80 profile .
• Level 2: Slab thickness set to 225 mm, superimposed dead load 0, live load 2.5 kN . It was set to not be profiled or composite .
• Roof: Slab thickness 0, superimposed dead load 0.3 kN, live load 0.6 kN .

Panel loads were defined :

• Level 1: The majority was defined as one-way spanning . A second group, Level 1 Storage, was created for specific areas, setting the live load to 6 kN .
• Level 2: Spanned directly in the Z direction .
• Roof: Spanned the Z-axis .

B. Line and Patch Loads

• First Floor Perimeter Load: Added as a dead load of 12 kN/m .
• Plant Load: Added to Level 1, defined as a dead load of 15 kN/m intensity in a specific area .
• Level 2 Perimeter Load: Added as a dead load of 6 kN/m .
• Patch Load (Level 2): Applied with an intensity of 7.5 kN/m² (on top of the default load) in a defined rectangular area .

C. Semi-Rigid Stiff Deck

To transmit lateral loads, semi-rigid stiff decks were applied to the floors (Level 1 and Level 2) :

• Level 1: Slab thickness 175 mm, modulus of 26 .
• Level 2: Slab thickness 225 mm, modulus of 26 .

D. Wind Loading

Wind loading was applied using Eurocode methodology :

• Settings: Wind loading was turned on, using four directions with internal suction and internal pressure, using the directional method . The angle to north was set to 30 degrees .
• Site Data: The location was set in Northern Ireland . The Irish Grid Reference Finder was used to input the coordinates . The EN standard method was selected .
• Applying Wind Panels: The auto function was used to apply all wind panels to the surfaces . Spanning directions were customized for walls, including setting one side to span vertically and another section to span two-way . The results allowed viewing actual pressures and coefficients .

V. Load Cases and Structural Modifications

A. Load Case Generation

The original 12 loading cases were deleted . New loading cases were auto-created using the Eurocode guidelines:

• Dead + Live: Ultimate state, using design approach 610, including characteristic values and equivalent horizontal notional forces .
• Dead + Live + Wind: Applied for all wind directions (W, P, and S), ultimate and service states, using design approach 610, resulting in a large number of cases .
• In total, 61 loading cases were generated .

B. Opening Creation (Staircase)

An opening was created at the first floor (Level 1, grid lines 1 to 2, B to C) :

1. The central member was deleted .
2. Four new members were drawn using 406 by 39 355 steel, releasing the ends . These were assigned to groups: "stair side" and "stair headers" .
3. The area loading panels were modified to adjust their spanning direction and remove the panel load from the opening area .
4. Stair Loading was added as a line load on the header beam: 16.5 kN dead load and 9 kN live load .
5. A partition wall load of 2.5 kN was drawn around the opening on the other three sides .
6. The diaphragm action for Level 1 was modified to exclude the four members binding the opening, creating a "big hole" .

VI. Design and Analysis

A. Design Group Definition

Extensive design groups were created for beams and ties to control the sizing process:

• Ties on Level 2 and the roof (internal/external) were defined as strut and tie with a slenderness limit of 250 .
• Numerous composite design groups (e.g., Edge Beams Gridline Six, East-West transfer beams) were established for the Level 1 floor, totaling around seven groups in one direction and six in the other, to manage design control .

B. Composite Design

1. Design Briefs: All composite design briefs were created automatically .
2. Global Editing: Global options were edited for all composite members. They were set to be propped . The concrete grade was changed globally to 35 . The metal deck contribution was set to 100%, and the basic mesh was specified as 142 . Crucially, the shear stud welded height was changed to 125 mm (19 by 125) .
3. Auto-Sizing: The composite beams (78 members) were auto-sized by weight order .
4. Failure Management: Failures found in certain beams (e.g., on grid line 3A) due to heavy loading (likely the patch load) were managed by moving them into a separate non-composite group ("Plant Room Beams") and specifying them as axially loaded with moment, fully restrained by slabs .

C. Steel Design and Second Order Analysis

1. Steel Member Design: After re-analyzing , all design checks were deleted . The steel members were auto-designed using the set design rules, sorting by weight order .
2. Stability Check: An elastic critical load factor check was performed . Since values were less than 15, a P-delta analysis was required .
3. P-Delta Analysis: Second order analysis settings were updated to include P-Delta using the Newton-Raphson method, applied to all ultimate cases . The structure was then re-analyzed .
4. Final Checks: After the P-delta analysis, the elastic critical load factor was confirmed as okay, and a final scan showed zero failures .

Summary with Timestamps

This is a summary of the tutorial detailing the conversion of a 2D steel frame into a 3D structure and performing steel and composite design checks according to Eurocode 3 and 4, presented in a chronological table format.