Design a built-up laced column with four angles_t6_support an axial lo...
• Design a built-up section using four angle section for
a column to support a design axial compressive load
of 500kN at desired distance. The channel sections
are effectively held at desired position using adequate
lacings. Assume that the effective length of the
column is 3m. Use S235 steel grade. Design also the
lacing system for built-up section.
105
• Soln.
Assume the following trial section with H=B
250mm
Design a built-up laced column with four angles_t6_support an axial lo...
Design of Built-Up Laced Column
The design of a built-up laced column to support an axial load involves several steps. Below is a structured approach to designing a built-up laced column with the given parameters.
Parameters
- Load (P): 900 kN
- Length (L): 12 m
- Material: Fe 410 Steel
- End Conditions: Held in position and restrained against rotation
Step 1: Column Sizing
- Select a suitable angle size for the column. A common choice is to use angles of equal size, such as 100 mm x 100 mm x 10 mm.
- Calculate the effective length (Le) using Le = L (for fixed ends, Le = L).
Step 2: Determine the Slenderness Ratio
- Calculate the radius of gyration (r) using the formula: r = √(I/A), where I is the moment of inertia and A is the cross-sectional area.
- Calculate the slenderness ratio (λ) using λ = Le/r.
Step 3: Load Carrying Capacity
- Determine the buckling load (Pcr) using the Euler's formula: Pcr = π²EI/Le².
- E is the modulus of elasticity for Fe 410, approximately 200 GPa.
Step 4: Design Lacing System
- Design the lacing system to ensure stability. The lacing can be done using flat bars at a specified angle (usually 45 degrees) to ensure effective load transfer.
- Use appropriate lacing spacing as per design codes.
Step 5: Check for Local Buckling
- Ensure that the design meets local buckling criteria based on the width-to-thickness ratios of the angles used.
Final Considerations
- Verify safety factors and consider factors of safety as per relevant design codes.
- Perform a detailed check for shear and bending stresses to ensure the column can safely support the axial load.
This structured approach should enable the effective design of a built-up laced column to support the specified axial load.