BT5 FINALS_MOD 7 SHELL STRUCTURE

Shell Structures

- Thin, curved plate structures shaped to transmit applied forces by membrane stresses.
- Can sustain relatively large forces if uniformly applied
- low bending resistance and not best for concentrated loads

Translational surfaces

[TYPES OF SHELL STRUCTURE] generated by sliding a plane curve along a straight line or over another plane curve

Barrel shells

[TYPES OF SHELL STRUCTURE]

- cylindrical shell structures
- If long enough, it behaves as a deep beam with a curved section spanning in the longitudinal direction.
- If short, it exhibits arch-like action

Ruled surfaces

[TYPES OF SHELL STRUCTURE] generated by the motion of a straight line

Hyperbolic paraboloid (Hypar)

[TYPES OF SHELL STRUCTURE] a surface generated by sliding a parabola with
downward curvature along a parabola with upward curvature, or by sliding a
straight line segment with its ends on two skew lines

Saddle surfaces

[TYPES OF SHELL STRUCTURE] have an upward curvature in one direction and a
downward curvature in the perpendicular direction

Rotational surfaces

[TYPES OF SHELL STRUCTURE] generated by rotating a plane curve about an axis

Gridshells

[TYPES OF SHELL STRUCTURE] consist of discrete members connecting nodal points that lie on the surface of an imaginary shell

Dome

- a spherical surface structure having a circular plan.
- similar to a rotated arch except that circumferential forces are developed which are
compressive near the crown and tensile in the lower portion

Compressive; tensile

Hoop forces, are _____ in the upper zone and _____ in the lower zone.

tension ring

A ______ encircles the base of a dome to contain the outward components of the meridional forces; thickened and reinforced to handle the bending stresses.

proportioned

The thin shell's thickness and reinforcement must be _____ to satisfy the strength
provisions, so as to resist internal forces

3cm

Shell Thickness can start right from ____cm

High strength concrete mixtures

_______ can greatly reduce the thickness of concrete shells.

ribs

Long-span shells can be strengthened by _____ depending on the shape, size and concrete strength. This will reduce large deflections and will also add to the strength of the shell.

bidirectional rib networks

ribs placed on the inside face of the surface

concrete

[SHELL REINFORCEMENTS] Enhance the homogeneity of ________ throughout the entire shell surface and to take care of tensile stresses.

shrinkage and temperature stresses

[SHELL REINFORCEMENTS] • Reinforcement take care of _______ and ____, limiting crack width, and its spacing.

edge beams and ribs

[SHELL REINFORCEMENTS] Additional reinforcement is required in ________ and _____ and also around openings and at locations of load attachments.

Steel

[SHELL REINFORCEMENTS] ____ provided to resist the tensile stresses is assumed to act at the middle shell surface.

8cm

[SHELL REINFORCEMENTS] Shells with _cm thickness should be reinforced with two overlapped layers of steel bars, ensuring the needed concrete covering

two perpendicular directions

[SHELL REINFORCEMENTS] • In shells whose thickness is around 4 cm thick, the reinforcement can be provided in the middle surface in _____

Steel or carbon

[SHELL REINFORCEMENTS] ________ fiber reinforcement may be effective to reduce the concrete shrinkage, as well to improve its homogeneity and compactness.

no pockets or honey-combing

[SHELL CONCRETING] The concrete placing should produce a smooth dense solid texture on the undersurface of the shell with ____ or ____.

supporting; stiffening

[SHELL CONCRETING] Concreting should be done starting from the _____ beams and ____ beams working upwards from lower end to higher end

zones of compressive stresses

[SHELL CONCRETING] Construction joints should preferably be located in _____
and the concreting should be done in a symmetrical manner and treated with
bonding agents.

Plate Structures

- rigid, planar, often monolithic structures that disperse applied loads in a multidirectional pattern
- can be envisioned as a series of adjacent beam strips interconnected continuously along their lengths

lateral buckling

Plate structure composed of thin, deep elements joined rigidly along their boundaries and forming sharp angles to brace each other against _________.

Vertical diaphragms or rigid frames

stiffen a folded plate against deformation of the fold profile.

FALSE (could not carry)

[TRUE OR FALSE] In plate structures- theory, a piece of paper without any fold could carry its own weight.

TRUE

[TRUE OR FALSE] After being folded the paper can not only stand between the gap, but also carry some extra weight.

Edge plates

[PLATE STRUCTURE PARTS] stiffens the wide plate

Stiffeners

[PLATE STRUCTURE PARTS] - supports and holed the plates in line

Column

[PLATE STRUCTURE PARTS] and/or supports to transmit the load to the ground

- Linear Folded plate structure
- Radial Folded plate structure
- Spatial Folded plate structure

Plate Structures based on support

• Folded plate surfaces
• Folded plate frames
• Spatial folded plate

Plate Structures based on shapes

• 3-segment folded plate
• Z- shell
• Canopies
• Tapered
• Edge-supported
• Folded plate truss
• Folded plate rigid frame
• Continuous wall with shell

Plate Structures - Roof Form Types

1-way

[Reinforcing Plate Structures] A combination of ____ slab and longitudinal beam action.