BASIC STRENGTH CONCRETE AND STEEL STRUCTURE ALLOWABLE STRESS AND BEARING CAPACITY

1.0      Concrete

Concrete design shall be strength design method using the appropriate load factor and load combination of AMERICAN CONCRETE INSTITUTE 318. The compressive strength of concrete at 28 days monitored by cylinder test shall be as follows unless otherwise specified:

Table 1

Concrete Compressive Strength

1.1      Reinforcing Steel Bar

Reinforcing steel bar shall be billet steel of grade 40 and 60 (ASTM A615) having minimum specified yield stresses of fy = 40,000 psi (276 N/mm² = 2814 kg/cm²) and  60,000 psi (414 N/mm² = 4222 kg/cm²). The modulus of elasticity for all non pre stressed steel may taken (ACI-8.5.2) as 29,000,000 psi (200,000 N/mm²). The steel used for Welded Wire Fabric (WWF) is that having minimum specified yield stress of 70,000 psi (4922 kg/cm).

1.2      Structural Steel or Pipe

The structural steel or pipe shall have minimum yield strength Fy = 2400 kg/cm²

1.3      Bolts, Rivets and Anchor bolts

Material for bolts, rivets, anchor bolts and tie rods shall be in accordance with AISC Tables below and for anchor and tie rods in accordance to AISC table.

Table 2

Bolt Strength

1.4      Allowable Bearing Capacity of Soil and Pile

As per soil investigation report

2.0          STRUCTURAL STEEL

2.1          Design Method

In design of steel structures, members shall be design in accordance with allowable Stress Design Method  in AISC  Specification.

Structural steel design, fabrication, and erection shall be according to the following materials, and general requirements :

2.1.1      Structural steel shall be of grade conforming to ASTM-A36

2.1.2      Shop connections normally shall be welded. Use welding electrodes with a tensile strength of 70 ksi.

2.1.3      Field connections shall normally be high strength bolted using bearing-type connections. Bolts shall be designed with threads included in the shear planes. However, major moment connections, where ductility is required, shall be field bolted for shear (and erection) and field welded for moment. Another exception will be secondary or lightly loaded members, such as girts, purlins, stairs, ladders, handrails, etc., where 5/8-inch diameter unfinished bolts (ASTM A307) shall be used.

2.1.4      All connections that are not detailed or otherwise noted on the design drawings shall be shop welded and field bolted AISC Framed Beam Connections, Tables II and III, as shown in AISC Manual of Steel Construction. Use the maximum number (n) rows of field bolts compatible with a beam T dimension and flange cope for each beam depth under consideration. Use a ¼ inch shop weld “A” shown in Table III for the required number of field bolts.

2.1.5      Welding shall be performed in accordance with AWS D1.1 - Structural Welding Code.

2.1.6   All structural steels shall be designed to tolerate corrosion or shall be protected against corrosion that impair the strength or serviceability of the structure. Galvanizing and/or painting on the structural steel shall be accomplished in accordance with General Company Specification.

2.1.7      Access platform and walkways shall be covered with serrated grating. The weight of removable flooring sections shall not exceed 50 kg (110 lb). Gratings and all associated fittings and fixtures shall have galvanized finish.

2.1.8      Structural tees are preferred in lieu of double angles for horizontal bracing members.

2.1.9      Gusset plate shall be 3/8-inch (9.5 mm) minimum thickness.

2.1.10    Guardrails shall conform to the safety regulation.

2.2          Allowable Deflection

Structural Member Deflection:

The deflection of any structural members shall not exceed the values as follows:

2.2.1      Beam Vertical Deflection

Purlins, girts, joists (due to dead load and imposed loads) : span / 200, Maximum deflection of grating and floor plate shall not exceed ¼ of an inch.

2.2.2      Horizontal Deflection:

Total horizontal displacements for columns steel structure shall not exceed 1/300 (permanent load) and 1/200 (temporary load) of the height structure as the conforming SNI-03-1729-2002 and 1/200 of the height of equipment supporting structures except for flare stack structure supporting.