Written by: Engr Sami Ullaht Stanikzai (www.civilglobal.com)
In this article today i want to understand you, what are the important points for civil engineers at the site. after reading this article you will be able all of those points which are important and using at side during construction works.
Minimum 1 inch spacing between bars in beams according to ACI code.
- Curtailment at ends in case of simply supported beams L/8 from face of support.
- For continuous beams curtailment at L/3.
- Maximum spacing for stirrups is 12 inch.
- If reinforcement is provided in two layers then 1 inch distance between bar layers must be maintained using spacer bars.
- If effective depth of beam is more than 36 inch than provide skin reinforcement up to d/2 maximum Ast/2. Use at least #6 bars.
- For simple houses 15ft or 20ft span beams can be supported on walls. Support beams by columns where span is more.
- Small foundation sizes i.e. 10ft or 12ft take them as hinge support.
- Take raft foundations as fixed support.
- Wall is idealized as hinge.
- Beam supported on girder idealized as roller. Tip of beam is fixed or glued to hinge while roller will move little bit.
- To avoid movement of negative structure assume one support as hinge and other as rollers.
- Negative reinforcement would be more at central support and positive reinforcement would be more for end spans.
- Total moment i.e. sums of positive and negative moment would always be wl2/8 between two supports.
- Minimum thickness for footing should be 12 inch. Lean concrete up to 3 inches. This will do leveling.
- Monolithic means continuity of negative reinforcement i.e. effect of one span is transferred to other span. Structure would become monolithic if you provide negative reinforcement. It would resist cracks otherwise it would become hinge support.
- Footing is designed only for axial loads, no need to consider moments.
- Beam-column joint is a rigid joint, not a fixed one.
- In Pakistan, we either provide stiff beams or no beams at all. Beams are thickened part of slab and are pseudo supports not true supports.
- Provide negative reinforcement equal to positive reinforcement of one way slab at joint between one way and two way slabs.
- It is routine practice to provide spacing multiple of each other.
- Average load on slabs is between 200 to 300 psf.
- Average positive moment on beams is between 1000 to 2000 kips-inch.
- If beam dimension is less than column then moment may arise if you not placed them concentrically on column. So same dimensions of beams and columns should be provided to flush them at joint and pass steel of beam from inner side of column core.
- 3000 psi is compressive strength of concrete. Flexural capacity of concrete would be 7.5 sqrt (fc). Modulus of Elasticity for concrete would be 57000 sqrt (fc) / 1000.
- In SAP, use centerline length of frame elements.
- Usual column sizes are 12 x 12 square inches,18 x18 square inches etc.
- maximum free fall of concrete is 1.5 meter.
- we have to use the diameter of steel for the slab 1/8 of the slab thickness.
- Compressive strength of Bricks is 3.5 N / mm2.
- Minimum thickness of slab is 125 mm.
These the very interesting and valuable note for civil engineers .
written by: Engr Sami Ullah (www.civilglobal.com)