Sachpazis: Design of Steel Warehouse in ETABS

Sachpazis: Design of Steel Warehouse in ETABS


Summary
This Powerpoint Presentation tutorial focuses on designing a steel warehouse using the software ETABS. It explains the importance of portal frames and bracing structures for lateral stability in the building. The Powerpoint Presentation covers the concept of portal frame action and how bracing elements, like struts and fly braces, are used to resist wind loads and prevent buckling. It also provides practical tips on selecting appropriate sections, applying loads, and using ETABS to analyze the structure's stability.

1. Designing a Steel Warehouse with ETABS This guide covers the design of a steel warehouse using ETABS software, focusing on portal frames, wall and roof bracing, fly braces, and wind load considerations. We'll explore the structural elements and design principles for creating a stable and efficient warehouse structure, using a combination of portal frames, bracing systems, and strategic load distribution techniques. by Professor Costas Sachpazis

2. Understanding Portal Frames 1 Structure Portal frames consist of columns and rafters (beams) connected to form a rigid frame. 2 Function They provide lateral stability along the frame's direction, transferring loads to the foundation. 3 Spacing In this design, portal frames are spaced at 6.3m intervals.

3. Portal Frame Load Transfer Wind Load on Cladding Wind forces act on the exterior cladding of the warehouse. Transfer to Frame Loads are transferred from the cladding to the portal frame structure. Frame Action The portal frame distributes the loads through its members. Foundation Transfer Loads are ultimately transferred to the foundation.

4. Importance of Bracing Lateral Stability Bracing provides essential lateral stability, especially for loads perpendicular to the portal frame's strong axis. Load Distribution It helps distribute lateral loads effectively throughout the structure. Collapse Prevention Proper bracing prevents structural collapse under wind loads from various directions.

5. Types of Bracing in Warehouses 1 Wall Bracing Vertical bracing along walls to resist lateral loads. 2 Roof Bracing Horizontal bracing in the roof plane to distribute loads. 3 Fly Braces Additional bracing to support critical elements like rafters. 4 Struts Horizontal members that work with bracing to transfer loads.

6. Bracing Mechanics 1 Load Application Wind load is applied to the structure's face. 2 Deformation Structure deforms, activating bracing elements. 3 Tension in Bracing Bracing members go into tension, resisting deformation. 4 Load Transfer Forces are transferred through nodes and struts to the foundation.

7. Column Orientation in Portal Frames Strong Axis Alignment Columns are oriented with their strong axis (major axis) aligned with the portal frame direction. Maximizing Strength This orientation maximizes the frame's capacity to resist lateral loads in its primary direction. Efficient Design Proper orientation allows for more efficient use of material and smaller section sizes.

8. Strut Design Considerations 1 Combined Loading Struts experience both axial forces and bending moments. 2 Capacity Reduction Axial capacity is reduced due to bending moments. 3 Design Check Combined action of axial force and bending must be considered in design.

9. Mullions in Portal Frame Design Definition Mullions are vertical structural elements between main portal frames. Function They provide additional support and allow for reduced section sizes in main frames. Orientation Typically oriented with their strong axis perpendicular to the wind direction.

10. Advantages of Bracing in Portal Frames 1 Section Size Reduction Bracing allows for smaller column and beam sections. 2 Enhanced Stability Improves overall structural stability against lateral loads. 3 Cost Efficiency Reduces material costs through optimized design. 4 Flexibility in Design Allows for more architectural freedom in building layout.

11. Foundation Connection Design Horizontal Load Transfer Connections must be designed to transfer lateral loads to the foundation. Uplift Resistance Must resist vertical uplift forces from wind loads. Shear Capacity Connections should have sufficient shear capacity for horizontal forces. Bolt Design Bolts must be sized and arranged to handle combined forces.

12. ETABS Modeling: Grid Setup 1 Grid Definition Set up the grid system based on architectural drawings. 2 Story Heights Define story heights, including eave height (5500mm) and apex height (700mm above eave). 3 Material Selection Choose appropriate steel grade (e.g., F250 for Indian standards).

13. Defining Steel Sections in ETABS 1 Section Library Use built-in section libraries or import custom sections. 2 Initial Selection Start with ISMB 450 for columns and rafters (can be adjusted later). 3 Orientation Ensure correct orientation of sections (strong axis alignment). 4 Property Modification Adjust section properties as needed for design optimization.

14. Creating the Portal Frame Model 1 Draw Columns Place columns at grid intersections. 2 Add Rafters Connect columns with rafters to form the portal frame. 3 Replicate Frames Copy and paste frames to create the full warehouse structure. 4 Add Mullions Insert mullions between main portal frames.

15. Modeling Struts and Bracings Strut Placement Add horizontal struts at specified heights along the frame. Bracing Elements Model diagonal bracing members using appropriate sections (e.g., angle sections). Connection Definition Define end releases for bracing members to represent pin connections.

16. Applying Wind Loads in ETABS Load Calculation Calculate wind loads based on local codes and building geometry. Load Application Apply distributed loads to frame members representing wind pressure. Load Variation Consider different load intensities for central and end frames. Direction Apply loads in both principal directions to assess worst-case scenarios.

17. Defining Connection Types 1 Column Base Define pin connections at column bases. 2 Beam-Column Joints Model moment-resisting connections for portal frame joints. 3 Bracing Connections Set pin connections for bracing ends. 4 Strut Connections Model partial fixity for strut-to-column connections.

18. Running the Analysis 1 Model Check Perform a model check to ensure all elements are properly connected. 2 Analysis Type Run a linear static analysis for wind load cases. 3 Stability Check Verify overall structural stability after analysis. 4 Results Review Examine deformed shape and member forces for reasonableness.

19. Interpreting Analysis Results Member Forces Review axial forces, shear forces, and bending moments in frame elements. Deflections Check lateral and vertical deflections against allowable limits. Critical Sections Identify highly stressed areas for detailed design consideration.

20. Design Considerations for Hunches 1 Purpose Hunches increase moment resistance at high-stress areas. 2 Placement Typically located at beam-column joints of portal frames. 3 Sizing Length usually 10% of frame span. 4 Benefits Reduces required depth of rafters and increases frame stiffness.

21. Moment Connection Design Flange Connection Ensure flanges are properly connected to transfer bending moments. Web Connection Design web connections for shear transfer. Stiffener Plates Add stiffener plates to prevent local buckling and ensure moment transfer. Bolting/Welding Choose appropriate connection method based on design requirements.

22. Lateral-Torsional Buckling Considerations 1 Critical Flange Identify the compression flange under different load conditions. 2 Purlin Restraint Consider purlin placement for top flange restraint. 3 Fly Braces Implement fly braces to restrain the bottom flange where necessary. 4 Effective Length Calculate effective lengths for unrestrained segments.

23. Wind Load Coefficient Variation Coefficient Distribution Wind coefficients vary along the length of the building, typically higher at ends. Design Implications Central frames may be subjected to lower wind loads than end frames. Bracing Placement Optimal bracing locations can be determined based on wind coefficient distribution.

24. Frame Section Design in ETABS 1 Initial Check Run steel frame design check with initial section sizes. 2 Failure Analysis Identify members failing design criteria. 3 Section Optimization Iteratively adjust section sizes to meet design requirements. 4 Final Verification Confirm all members pass design checks with acceptable utilization ratios.

25. Final Section Sizes Element Initial Size Final Size End Columns ISMB 450 ISMB 450 Central Columns ISMB 450 ISMB 600 Rafters ISMB 450 ISMB 600 Braces Angle 100x100x4 Angle 100x100x4

26. Design Capacity Check Utilization Ratio Aim for utilization ratios close to but not exceeding 1.0. Critical Members Identify members with highest utilization for potential future upgrades. Safety Margin Ensure adequate safety margin in design (e.g., 1.025 utilization acceptable).

27. Additional Design Considerations 1 Serviceability Limits Check deflections against allowable limits for serviceability. 2 Fatigue Design Consider fatigue design for structures subject to cyclic loading. 3 Fire Protection Incorporate fire protection measures as required by local codes. 4 Corrosion Protection Specify appropriate coatings or treatments for corrosion resistance.

28. Documentation and Reporting 1 Design Calculations Compile detailed design calculations for all structural elements. 2 Drawing Production Create structural drawings including plans, elevations, and connection details. 3 Specifications Develop technical specifications for materials and construction methods. 4 Design Report Prepare a comprehensive design report summarizing analysis and design decisions.

29. Construction Considerations Erection Sequence Plan the erection sequence to ensure structural stability during construction. Temporary Bracing Design and specify temporary bracing requirements for the construction phase. Quality Control Establish quality control procedures for fabrication and erection of steel elements.

30. Final Design Review and Approval 1 Peer Review Conduct an independent peer review of the structural design. 2 Code Compliance Verify compliance with all applicable building codes and standards. 3 Client Approval Present final design to the client for review and approval. 4 Regulatory Submission Submit design documents to relevant authorities for permitting and approval.

31. Designing a Steel Warehouse with ETABS This guide covers the design of a steel warehouse using ETABS software, focusing on portal frames, wall and roof bracing, fly braces, and wind load considerations. We'll explore the structural elements and design principles for creating a stable and efficient warehouse structure, using a combination of portal frames, bracing systems, and strategic load distribution techniques. by Professor Costas Sachpazis