Structural Steel Design encompasses the quality standards, allowable unit stresses, and construction details for steel and iron components as defined in Chapter 27 of the 1935 miami dade building code. This concept integrates material specifications, stress calculations, and connection methodologies to ensure structural integrity.
Quality and Material Standards
The code mandates that structural steel conform to Standard Specifications for Structural Steel for Buildings, A. S. T. M., Designation A9-33, issued by the american society for testing materials (p. 206). Cast steel must meet ASTM Designation A27-24, and cast iron must meet Designation A48-32T (p. 206). All structural steel must be tested if deemed necessary by the building inspector, with results filed in their office (p. 207).
Later amendments updated the reference standards for design. Ordinance No. 3703 (1949) amended Chapter 27 to adopt the aisc steel construction manual 5th edition as the standard for allowable factors for structural steel requirements (p. 336). This replaced earlier specific stress tables with the comprehensive guidelines provided by the american institute of steel construction.
Allowable Unit Stresses
Designs must ensure that the sum of maximum static stresses does not exceed specified limits (p. 207). Key allowable stresses include:
- Tension: 18,000 psi for rolled steel on net section; 16,000 psi for cast steel (p. 207).
- Compression: 18,000 psi for rolled steel on short lengths; specific formulas apply for columns based on slenderness ratio (p. 207).
- Bending: 18,000 psi on extreme fibers of rolled shapes if lateral deflection is prevented (p. 208).
- Shear: 13,500 psi on power-driven rivets and pins; 12,000 psi on webs of beams and girders where height-to-thickness ratio is limited (p. 208).
Connections and Workmanship
Connections are critical to structural performance. Rivets are preferred for main members carrying live loads with impact or stress reversal (p. 213). welding may be used as an alternative to riveting, with allowable stresses of 13,000 psi for tension in butt welds and 11,300 psi for shear in fillet welds (p. 213). Welders must demonstrate competence, and electrodes must conform to american welding society specifications (p. 213-214).
The code specifies minimum distances for rivet holes and edges to prevent failure (p. 212). Workmanship requires that rivets be driven hot and tight, with proper heating temperatures monitored (p. 217). Gas cutting is permitted under strict conditions, such as for preparing base metal for welding, but not for replacing milling of bearing surfaces (p. 217-218).
Specific Components
- Beams and Girders: Plate girders must be proportioned by the moment of inertia of their net sections. Web stiffeners are required to prevent buckling, with spacing determined by specific formulas (p. 210-211).
- Steel Joists: These secondary members must be designed to carry all loads without exceeding deflection limits of 1/360 of the span. In buildings over eight stories, specific connection standards using power-driven rivets or bolts are required (p. 215-216).
- Cellular Steel Floors: Ordinance No. 3334 (1947) introduced specific standards for cellular steel floors, requiring steel equal to ASTM A24542T Grades A, B, or C, with a minimum thickness of U.S. Standard Gauge No. 18. Flexural stress values were limited to 60% of the yield point (p. 331-332).
- Corrosion Protection: All structural steel must be painted with chemically inert pigments. Steel in damp locations or under water must be encased in Portland cement concrete (p. 218).
This concept is closely related to structural-load-calculations and reinforced-concrete-design, as steel and concrete often interact in composite structures. See 1935-Miami-Dade-Building-Code_p205_224 for detailed regulatory text on general steel provisions, and 1935-Miami-Dade-Building-Code_p325_344 for amendments regarding steel joists and adopted manuals.