Analysis of structure

Analysis of structure

Based on the forces for analysis, structures are classified into two types

1.     Determinate structures

2.     Indeterminate structures

Determinate Structures: The structures whose unknown forces can be determined by using the equilibrium conditions itself are called as determinate structures.

Indeterminate Structures: These are the structures in which the unknown forces cannot be analyzed by using conditions of equilibrium only but instead it requires the additional equations to determine the unknowns which are called as compatibility equations.

Degree of indeterminacy

Degree of Indeterminacy is nothing but the number of redundants that has to be calculated .DOI is classified into two categories such as

1.     Statically indeterminate structure

2.     Kinematically indeterminate structure

Statically indeterminate structure: It is the number of additional equations required apart from equilibrium conditions to solve the unknown reactions of the structure.

Static Indeterminancy is further classified into two categories

·        External Static Indeterminancy

·        Internal Static Indeterminancy

External Static Indeterminancy: It is the type of static Indeterminancy, caused due to the unknown reactions of the support itself.

De = R-3 (for 2D structures)

De =R-6 (for 3D structures, since for 3D structures, there will be 6 equilibrium conditions)

Where De = External Static Indeterminacy

R= Number of Support Reactions

                       

                       De=R-3 = Externally Determinate Structure

                       De> R-3= Redundant structure

De< R-3=Unstable structure

Internal Static Indeterminancy: It refers to geometrical stability of the structure.If the internal forces of the members cannot be determined by equilibrium conditions itself then it is said to be internally indeterminate.

For geometric stability of structures sufficient members are requires to preserve the shape of the structure without causing excessive deformation.

Dsi =3C-Rr            (Where C= No of closed loops

Dsi =6C-Rr                                Rr= Released reactions)

Therefore Static Indeterminancy= External + internal Indeterminancy

Degree of static Indeterminancy for different structures.

1. Plane Frame = 3m+r-3j
2. Space Frame = 6m+r-6j
3. Plane Truss = m+ r-3j
4. Space Truss = m+r-2j

Kinematic Indeterminancy

It is the number of free displacement of the structure which are unknown in addition to the compatibility equations.

Hence the extra equations required to determine the additional unknown displacements are called as kinematic Indeterminancy or it is also called as degree of freedom.

DEGREE OF FREEDOM

DEGREE OF FREEDOM

Degree of freedom (DOF) is defined as the set of independent displacements/rotations that describe the deformed shape of the structure with respect to its initial position.

In simple terms, DOF of the structure is the number of directions the structure can be moved freely without any restrainment.

As in case of two dimensional structures; each joint will have the 3 possible degrees of freedom .i.e., one in horizontal direction, one in vertical direction and one rotation. But as in case of 3 dimensional structure; each joint will have the 6 possible degrees of freedom .i.e., 2 in horizontal direction ,2  in vertical direction and 2 rotation.

Mode number and mode type are the two important factors on which dof depend. Since every possible mode has to fit with the respective moving direction of the structural element. Therefore structure with more dof has more complicated modes.

Example: The train moving freely on the rail. This means the train can move freely along the rail in only one direction itself. Therefore the DOF for the above case will be 1.

Human head has 6 degrees of freedom

DOF is calculated as

DOF=R-S

Where R= 3, .i.e, Conditions of Equilibrium

S= No of Reaction forces of the support which required to resist the External load acting.

Degree of freedom for various support conditions

For Simple support

R = 3 ; S = 1 (i.e vertical direction)

Therefore, Dof = 2 (1 Horizontal direction and 1 rotation)

For Hinged support

R = 3 ; S = 2 (i.e vertical direction and 1 Horizontal direction)

Therefore, Dof = 1 (  1 rotation)

For Roller support

R = 3 ; S = 1 (i.eVertical direction)

Therefore, Dof = 2 (1 Horizontal direction and 1 rotation)

For Fixed support

R = 3 ; S = 3 (i.e Vertical direction , 1 Horizontal direction and 1 rotation)

Therefore, Dof = 0

Structure and structural forms

Structure and Structural forms

Structure is the assembly of the elements interconnected with each other which is exposed to the external loading and transfers the same load coming on it through its elements to the under-laying system.

Therefore, Structure is the one which is exposed to the external loading and transfers the load coming on it through its neighboring elements to the under-laying system.

Structural Analysis is the study of determination of the effects of the loads on the structure and its components.

The elements of the structure through which the loads are transferred to the under laying system  are called as structural forms.

Generally structural forms are classified into 3 groups:

•      One dimensional element: These are the elements on which the load is applied along the length and the corresponding deformations will takes place in the same direction as that of the applied load. Generally, in this type of element; the length of the element is greater than the other two dimensions.

Example: Beams, Cables etc.…

•      Two-dimensional element: These are the elements on which the loads are applied along both length and width and the corresponding deformations will takes place in both X and y directions of the element corresponding to the load applied. The thickness of the element is smaller than other dimensions as in case of two-dimensional elements.

          Example: Plates, Shells etc.…

•  Three-dimensional element: These are the elements on which the loads are applied along all the 3 dimensions and the corresponding deformations will takes place in all X ,Y and Z directions of the element corresponding to the load applied.

        Example: 3D solids

Theory of failure - Rankine's theory

Rankine's Theory or Maximum Principal stress theory

     According to this theory, Failure of the structure takes place when the major principal tensile stress reaches the value beyond elastic limit in simple tension and minor principal stress(compressive in nature) reaches a value beyond elastic limit in simple compression.

Consider the three dimensional structure subjected to stresses in three mutually perpendicular directions, let σ1 , σ2 and σ3 be the normal stress in all 3 respective directions in which , σ1 and σ2(Major principal stress) be the normal stress in tensile nature and σ3 (Minor principal stress) normal stress  which is  compressive in  nature.Therefore, According to this theory, the failure of the material takes place as follows

• σ1 and σ2 ≥ σt in simple tension.
• σ3  ≥ σc in simple compression

Therefor if the material has to be safe against failure, then the maximum principle stress should not exceed permissible stress.

• σ1 and σ2 = σp
• Since,  σp = σt / FOS

where  σp = permissible stress , σt = Tensile stress after elastic limit
Limitation of Rankine's theory

• This theory is only applicable for structure made of brittle materials subjected to all loading conditions.Since brittle materials are weak in tension.
• This theory is not suited for structures made of ductile material, since the ductile material is weak in shear.But only in some conditions the theory holds good for ductile materials .Some of the conditions are as follows

1. Under uni axial state of stress when maximum shear stress is equal to half of maximum principal stress.
2. Under bi axial state of stress when there is occurrence of like forces and also when maximum shear stress is equal to half of maximum principal stress.
3. Under hydrostatic condition .i.e, when shear stress at all the boundaries is equal to zero.

THEORY OF FAILURES - Introduction

THEORIES OF FAILURE 

     When a structural element has to be designed,then it is important to determine its strength and stability based on the elasticity,yielding and fracture.As a element alone , it is easy to determine its structural behavior in terms of simple stress and strain.But in reality, the structure cannot be analysed as a part since , load applied and its corresponding stress and strain behavior will be in complex form.Some of the theories were designed to predict failure pattern for simple loads were also declared to be feasible for complex loading also.But these theories used to predict failure pattern in complex loading , failed to provide proper results in practical conditions, hence they are termed as theories of failure.The following are the five theories of failure put forth by researchers.

1. Rankine's theory or Maximum Principal Stress theory.
2. Columb's theory or Maximum Shear stress theory.
3. St Venant's theory or Maximum Strain theory.
4. Beltrami and Haigh's theory or Maximum strain energy theory.
5. Von-Mises theory or Maximum Energy distortion theory.

Difference Between Determinate and Indeterminate Structures

Difference Between Determinate and Indeterminate Structures

S. No.	Determinate Structures	Indeterminate Structures
1	Conditions of Equilibrium are sufficient to determine the unknown forces and moments.	Conditions of Equilibrium are not sufficient to determine the unknown forces and moments.
2	Bending moment or shear force at any section is independent of the material property of the structure.	Bending moment or shear force at any section depends upon the material property.
3	The bending moment or shear force at any section is independent of the cross-section or moment of inertia.	The bending moment or shear force at any section depends upon the cross-section or moment of inertia.
4	Temperature variations do not cause stresses.	Temperature variations cause stresses.
5	No stresses are caused due to lack of fit.	Stresses are caused due to lack of fit.
6	Extra conditions like compatibility of displacements are not required to analyze the structure.	Extra conditions like compatibility of displacements are required to analyze the structure along with the equilibrium equations.

Classification of prefabricated construction system

Based on the type of precasting


Partial prefabricated open system: It is the system in which prefabrication is done only for the part of the conventional building.
Ex : Sunshades ,Kitchen sills etc.......



Full prefabrication system: It is the system in which  the overall building is constructed by prefabrication technique.

Classification of prefabricated construction system

Based on degree of precast

Smaller degree Prefabrication: Here the prefabrication is done in the smaller scale.

precast brick

Medium degree Prefabrication:  Here the prefabrication is done in the moderate scale.

                                  

      precast roof system                                                       precast floor system

Large degree Prefabrication : Here the prefabrication is done in the large scale.

  precast stair case system       

precast building 

Trade mark

Trade mark

A trade mark (popularly known as brand name in layman’s language) is a visual symbol which may be a word to indicate the source of the goods, a signature, name, device, label, numerals, or combination of colours used, or services, or other articles of commerce to distinguish it from other similar goods or services originating from another.

It is a distinctive sign which identifies certain goods or services as those produced or provided by a specific person or enterprise.

A trade mark provides protection to the owner of the mark by ensuring the exclusive right to use it or to authorize another to use the same in return for payment.

The period of protection varies, but a trade mark can be renewed indefinitely beyond the time limit on payment of additional fees.

INDUSTRIAL DESIGN

INDUSTRIAL DESIGN

Industrial design is a process of design applied to products that are to be manufactured through techniques of mass production.

Registration of industrial design

1.    Submit a duly filled in registration form with the prescribed fees along with four copies of the representation of the Design (of size 33cm x 25cm with suitable margins). The drawing should clearly depict the features of the design from all the views and it must state the view.

2.    The Application along with the required documents must be submitted to the Design Wing of the Patent Office in Kolkata or to any branch office of the Patent Office in Delhi, Mumbai or Chennai.

3.    On receipt of the application in the Patent Office, the Application is numbered, dated and taken up for examination. (Please note that unlike Patents there is no need to file a separate request for examination. Design Applications, once filed are automatically taken up for examination)

4.    If any defects are noticed in the Application, they are communicated to the Applicant or to his Agent.

5.    The defects must be corrected within a period of 6 months from the official date of Application.

6.    If the defects are not rectified, as required by the Controller a personal hearing is provided to the applicant. The Controller’s decision after the hearing is communicated in writing (stating reasons) to the Applicant or his Agent.

7.    The Applicant can appeal to the High Court (within 3 months from the date of the Controller’s decision)

Once accepted the Application is notified in the Patent Office Journal.

TYPES OF PATENTS

TYPES OF PATENTS

     A utility patent is what most people think of when they think about a patent. It is a long, technical document that teaches the public how to use a new machine, process, or system. The kinds of inventions protected by utility patents are defined by Congress. New technologies like genetic engineering and internet-delivered software are challenging the boundaries of what kinds of inventions can receive utility patent protection.

  

    A provisional patent goes hand in glove with a utility patent. United States law allows inventors to file a less formal document that proves the inventor was in possession of the invention and had adequately figured out how to make the invention work. Once that is on file, the invention is patent pending. If, however, the inventor fails to file a formal utility patent within a year from filing the provisional patent, he or she will lose this filing date. Any public disclosures made relying on that provisional patent application will now count as public disclosures to the United States Patent and Trademark Office (USPTO).

     A design patent protects an ornamental design on a useful item. The shape of a bottle or the design of a shoe, for example, can be protected by a design patent. The document itself is almost entirely made of pictures or drawings of the design on the useful item. Design patents are notoriously difficult to search simply because there are very few words used in a design patent. In recent years, software companies have used design patents to protect elements of user interfaces and even the shape of touchscreen devices.

            
           A plant patent is just that: a patent for a plant. Plant patents protect new kinds of plants 
           produced by cuttings or other nonsexual means. Plant patents generally do not cover                             genetically modified organisms and focus more on conventional horticulture.

Patent Agent.

Patent Agent.

The function of a patent agent are both technical and legal. The patent agent is therefore required to be qualified in science or engineering or technology and also the patent law through an examination conducted by the central government. Until 2005 advocates were permitted to apply for the patents on behalf of the client and also draft the specifications and claims in additions to practice and conduct the cases. Subsequent to the patent amendment act 2005, the following are the qualifications to register as a patent agent:

1.      Citizen of India

2.      21 years of age

3.      Graduate in science or Engineering or technology

4.      Should have passed the written examination conducted by the central government on patent law.

5.      Should have functioned as a controlled or examiner for atleast 10 year and should not be holding that post.

However patent agent inducting advocates who had registered prior to 2005 can continue to function as patent agent with the requisite renewal. The patent agents are required to apply for registration to the controller of the patents Kolkatta. Annual renewal with the prescribed fees is mandatory. On examination of the applications the controller shall grant the certificate of registration and publish the names of the patent agents in the gazette periodically and also maintain a register of patent agents.

Only individual are permitted to register as patent agent. A firm can act as a patent agent provided all the partners of the firm are registered patent agents. A company cannot register itself as a patent.

The patent agents can prepare the application for the patents draft the specifications and conduct the cases before the authorities without the attestation and signature of the paten agent patent. Application, specifications and claims shall not be received by the controller. The patent agent has to prepare all the documents and sign them. Certain document can be signed only by the patent agent, without the patent holders or investor’s signature.

The following documents must necessarily have signed by the applicant:

1.      Application for the patent

2.      Application for restoration of lapped patent

3.      Application for restoration of patent after the time allowed has expired.

4.      Application to amend

5.      Application for compulsory licenses or revocation

6.      Notice of surrender

The proceedings connected with the patent are legal and technical, Hence the patens agent should be convergent with both detailed discussions between the applicant and the patent agent on various aspects of the invention are necessary before drafting and filing. The applicant may not be competent or capable of drafting the claims in a legally acceptable form and hence the patent agent role is very crucial.

Also the time schedules under the patent law are many cases in spite of the discretionary powers of controller. Certain default have no remedy at all, also failure to attend the patent proceeding may result in ordinate delays and endanger. The grant of the patent” thus the patent agent should act with utmost case and responsibility any negligence mat cost the applicant. The degree of knowledge and care required by the patent agent are compared to those of a highly qualified person practicing with this high sense of duty and responsibility.

If the patent agent is found to be negligent in the use of his skill and experience or if he fails to exercise the necessary care and vigilance, he will be held liable for beach of duty towards his client.

            In cases where the patent agent fails to take precautions there by allowing the application to                lapse, the count may hold the negligent patent agent liable for damage.