17-05-2012, 02:54 PM
Deployable structures
[attachment=22260]
Introduction
Deployable structures:- capable of undergoing large configuration changes in an autonomous way.
Uses of Deployable structure:-
Easy Storage
Transportation
DTSS
Deployable Tension-Strut Structures(DTSSs) are:
Composed of struts
High strength tension element
Types of DTSS:
Pyramid-on-Pyramid structure (POP)
Pyramid-in-Pyramid structure (PIP)
Pyramid-Pantograph-Cable structure (PPC)
Pyramid-Pantograph-Pyramid structure (PPP)
POP
Composed of two pyramids attached to each other at their base.
“Pyramid” consists of four struts, connected in the centre by a pinned joint.
Disadvantage:-
Poor in resisting uplifts loads, which may require additional layer of cables in conditions where the uplift loads may exceed the self weight o
f the structure.
PIP
Composed of two pyramids attached at the base to each other but within each other.
“Pyramid” are formed by four pinned connected struts as in POP Structures.
The deployable of a PIP is achieved by sliding the central joint along the central rod and locking in its fina
l configuration.
POP Vs PIP
PIP Structure is in the central rod, which in the case of a POP structure is in tension and in the PIP is in compression.
If the central rod is made of cable(in POP) and struts(in PIP) then the variations in their modules and the higher cross sectional area of the compressive strut contribute to the higher stiffness of the PIP.
PPC
A new class of structures which consist of scissor-like elements (SLEs) and pyramidal elements.
The structure is stabilized into the deployed state by attaching the locking cables to the top pivot.
Under gravity loads the compressive forces are resisted by the top pyramid struts, the tensile forces are resisted by the network of cables at the bottom of the structure and the shear forces are resisted by the SLE system.
PPP
The Pyramid-Pantograph-Pyramid structure (PPP) is another SLE-based system.
The structure is deployed and stabilized by attaching and pre-stressing the central locking cable.
The PPP system can resist both gravity and uplift wind loads efficiently.
STRUCTURAL EFFICIENCY
Determining the suitability of any proposed structural system for practical implementation
Tension structures are highly flexible in nature, a nonlinear large displacement inelastic analysis is used to investigate their load–displacement behavior and to derive their optimum configurations to achieve maximum structural efficiency for design implementation.
DESIGN PROCEDURE
Elastic analysis
Factored loads
Service loads
Ultimate Limit State condition
Serviceability Limit State condition
COMPARATIVE STUDY
The least efficient of the DTSSs is chosen to explain structural efficiency
The effects on SEI, whi
ch increases by 75% on average when it changes from 0.15 to 0.08
DEPLOYMENT CHARACTERISTICS
The pantographs structures during deployment
The non-pantographic structures require manual coordination as each unit is not strongly linked to other units
Gravity loads are found to be sufficient to cause the deployment of these model structures
CONSTRUCTION OF JOINT IN DEPLOYABLE STRUCTURES
Joint must assure scissor-link bars rotating freely. So there is no larger friction and deformation of bending between the joints and bars.
Assuring bars packaged in a small volume for convenience in storage.
There should be enough strength for joint to bear axial force, also local shearing force, bending moment and bearing force.
Also, it should meet some special requirements in construction.
STRESS ANALYSIS FOR PLATE
The thickness of plates and diameter of hole their strength requirements
Forces inside the plane of the plate
The direction and value ce outside the plane of the plate make no obvious difference for its stress
Case Study
The Louvre Pyramid in Paris is a 20.6m(70ft) glass structure which acts as an entrance to the museum.
The Lu
xor Hotel in Las Vegas, United States, is a 30-story pyramid with light beaming from the top.
CONCLUSION
DTSSs deployment is made possible by the use of detachable elements. Previous designs of deployable structures compromised their structural efficiency to achieve deployment
The different types of Deployable Tension-Strut Structures are discussed using the parametric studies by finding structural efficiency index (SEI) based on the different span to height ratios of structures and different number of modules in one direction of span.
[attachment=22260]
Introduction
Deployable structures:- capable of undergoing large configuration changes in an autonomous way.
Uses of Deployable structure:-
Easy Storage
Transportation
DTSS
Deployable Tension-Strut Structures(DTSSs) are:
Composed of struts
High strength tension element
Types of DTSS:
Pyramid-on-Pyramid structure (POP)
Pyramid-in-Pyramid structure (PIP)
Pyramid-Pantograph-Cable structure (PPC)
Pyramid-Pantograph-Pyramid structure (PPP)
POP
Composed of two pyramids attached to each other at their base.
“Pyramid” consists of four struts, connected in the centre by a pinned joint.
Disadvantage:-
Poor in resisting uplifts loads, which may require additional layer of cables in conditions where the uplift loads may exceed the self weight o
f the structure.
PIP
Composed of two pyramids attached at the base to each other but within each other.
“Pyramid” are formed by four pinned connected struts as in POP Structures.
The deployable of a PIP is achieved by sliding the central joint along the central rod and locking in its fina
l configuration.
POP Vs PIP
PIP Structure is in the central rod, which in the case of a POP structure is in tension and in the PIP is in compression.
If the central rod is made of cable(in POP) and struts(in PIP) then the variations in their modules and the higher cross sectional area of the compressive strut contribute to the higher stiffness of the PIP.
PPC
A new class of structures which consist of scissor-like elements (SLEs) and pyramidal elements.
The structure is stabilized into the deployed state by attaching the locking cables to the top pivot.
Under gravity loads the compressive forces are resisted by the top pyramid struts, the tensile forces are resisted by the network of cables at the bottom of the structure and the shear forces are resisted by the SLE system.
PPP
The Pyramid-Pantograph-Pyramid structure (PPP) is another SLE-based system.
The structure is deployed and stabilized by attaching and pre-stressing the central locking cable.
The PPP system can resist both gravity and uplift wind loads efficiently.
STRUCTURAL EFFICIENCY
Determining the suitability of any proposed structural system for practical implementation
Tension structures are highly flexible in nature, a nonlinear large displacement inelastic analysis is used to investigate their load–displacement behavior and to derive their optimum configurations to achieve maximum structural efficiency for design implementation.
DESIGN PROCEDURE
Elastic analysis
Factored loads
Service loads
Ultimate Limit State condition
Serviceability Limit State condition
COMPARATIVE STUDY
The least efficient of the DTSSs is chosen to explain structural efficiency
The effects on SEI, whi
ch increases by 75% on average when it changes from 0.15 to 0.08
DEPLOYMENT CHARACTERISTICS
The pantographs structures during deployment
The non-pantographic structures require manual coordination as each unit is not strongly linked to other units
Gravity loads are found to be sufficient to cause the deployment of these model structures
CONSTRUCTION OF JOINT IN DEPLOYABLE STRUCTURES
Joint must assure scissor-link bars rotating freely. So there is no larger friction and deformation of bending between the joints and bars.
Assuring bars packaged in a small volume for convenience in storage.
There should be enough strength for joint to bear axial force, also local shearing force, bending moment and bearing force.
Also, it should meet some special requirements in construction.
STRESS ANALYSIS FOR PLATE
The thickness of plates and diameter of hole their strength requirements
Forces inside the plane of the plate
The direction and value ce outside the plane of the plate make no obvious difference for its stress
Case Study
The Louvre Pyramid in Paris is a 20.6m(70ft) glass structure which acts as an entrance to the museum.
The Lu
xor Hotel in Las Vegas, United States, is a 30-story pyramid with light beaming from the top.
CONCLUSION
DTSSs deployment is made possible by the use of detachable elements. Previous designs of deployable structures compromised their structural efficiency to achieve deployment
The different types of Deployable Tension-Strut Structures are discussed using the parametric studies by finding structural efficiency index (SEI) based on the different span to height ratios of structures and different number of modules in one direction of span.