Structural Analysis and Components

Structural Analysis

• The analysis of stress, strain, and deflection characteristics in structural behavior is structural analysis.

Structural Components

• Purlins are longitudinal beams resting on the top chord, preferably at truss joints.
• Rafters are inclined joists supporting sloping roofs.
• Girders are major horizontal supporting members in a floor system.

Thickness Requirements

• Minimum wall thickness for fireplace chimneys with flue lining per the National Building Code is 0.20.
• External wall thickness should be 150mm.
• Minimum thickness of front and side walls of a fireplace smoke chamber, as per the National Building Code, is 0.20.
• The minimum thickness of a reinforced concrete wall for masonry chimneys for residential-type appliances per the National Building Code is 0.10.

Loads and Forces

• Loads is the general term for all forces acting upon a structure, causing stress or deformation.
• Live Load refers to the occupancy load which may or may not be present.
• Bearing walls support weight from above, including their own dead weight.
• Factored load is the load multiplied by appropriate load factors.

Materials

• Concrete slab should have a minimum clearance of 40 mm from the top of formworks.
• Minimum size of a wood rafter is 2"x4".
• Class D concrete has a proportion of 1:3.5:7.
• 16mm diameter rebar is equivalent to 5/8".
• The smallest diameter of rebar for column stir-ups is 12mm.
• Fine aggregate should pass through a number 4 sieve.
• Concrete's standard weight is 2400 kg/cu.m.
• Steel weight is measured at 7850 kg/cu.m.

Structural Design and Standards

• Material product standards in the Philippines should conform to PNS.
• The current version of the National Structural Code of the Philippines being used is 2015.
• A concrete slab minimum thickness for cantilevered slabs should be L/10.
• ASTM grade 60 rebars is equivalent to PNS designation 415.
• Low-rise buildings, as per NSCP, have a mean roof height less than or equal to 18m.
• The minimum column section as per ACI is 200mm.

Clearances and Cover

• The amount of concrete to protect steel reinforcement from fire and corrosion is called cover.
• Minimum concrete covering for steel exposed to weather is 50mm.
• Minimum concrete cover for column pedestal exposed in underground soil is 50mm.

Reinforcement and Joints

• For column rebars 32mm and above, stir-ups should have a minimum diameter of 12mm, as required by the NSCP.
• End hooks of stir-ups should be bent 135 degrees.
• Bundled bars should have ties with a minimum diameter of 12mm.

Structural Behavior

• The deformation of a structural member due to loads is deflection.
• The section at which the moment changes from positive to negative is the inflection point.
• In a column, the ratio of effective length to least radius of gyration is the slenderness ratio.
• An open building has at least 50% of its walls open.
• Elasticity is the ability of a material to regain its original shape after a load is released.
• A fixed-end beam has both ends restrained against translation and rotation.
• Buckling is the sudden lateral or torsional instability of a slender structural member under compressive load.
• Fatigue is the weakening/failure of a material under repeated stress below the elastic limit.
• Camber is a slight convex curvature in a beam, girder, or truss to compensate for deflection.
• "Top bar" is any longitudinal bar that serves as tension reinforcement in the given section when a concrete beam or slab is subjected to negative movement.
• Slope of cut surfaces should be no steeper than 50%.

Earthquakes

• The measure of damage level of an earthquake, subjective to visual assessment, is intensity.
• Magnitude measures the energy released by an earthquake.

Structural Elements

• A flat slab is a type of concrete floor with no beams.
• Grade beam is a concrete beam placed directly on the ground to provide foundation for the superstructure.
• A dowel is a short steel bar extending from one concrete element to another.
• The distance between the inner faces of the supports of a span is the clear span.
• A construction joint is where two successive placements of concrete meet.
• A cold joint is formed when a concrete surface hardens before the next batch of concrete is placed.

Members and Columns

• The minimum number of vertical rebars in a rectangular column is 6.
• An intermediate column fails by both crushing and buckling.
• In columns, the distance between the inflection point at failure is called the effective length.
• As per NSCP, the minimum bar diameter bend of 10mm through 25mm bar is 6db.
• A short column fails by crushing.
• In Figure 1, fillet weld is to be applied on the spliced connection of the beam.

Walls

• A shear wall resists lateral forces parallel to the wall plane.
• A bearing wall supports vertical loads in addition to its weight without a complete vertical load-carrying space frame.
• A bearing wall system is a structural system without a complete vertical load-carrying space frame.

Loads

• Live load is the occupancy load that is either partially or fully in place or may not be present at all.

Failure

• A punching shear failure results when a heavily loaded column strikes a hole through the base.
• Overreinforced designs have more steel reinforcement than required for a balanced condition.

Design Conditions

• In concrete sections, overreinforcement occurs when concrete reaches ultimate strain before tension reinforcement reaches its yield strength.

Construction and Safety

• Ten days' notice in writing must be given to the owner of an adjoining building before commencing excavation work.
• All test of material samples shall be kept by the architect and engineer for 2 years.

Soil and Foundations

• Geotechnical reports must be dusky signed by a Geotechnical engineer.
• Underpinning is the art of placing a new foundation under an old foundation.
• A caisson is a watertight chamber used in underwater construction to protect workers from water pressure and soil collapse.

Volume

• Volume is measured in cubic units.

Hook Lengths

• The length required for a 135-degree hook is 4d.
• The length required for a 90-degree hook is 6d.

Aggregates

• For column rebars 32mm above, stirrups should have a minimum diameter of 12mm, as required by the NSCP.

NSCP Codes

• Group of parallel bars bundle together to ACT as one shall be limited to 4
• The choices which should not be bundle in beams is 32mm