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NOORUL ISLAM COLLEGE OF
ENGINEEING KUMARACOIL
DEPARTMENT OF CIVILENGINEEING
QUESTION ANSWERBANK
CE1029 COMPUTER AIDED DESIGN FOR
STRUCTURES EIGTH SEMESTER
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Unit 1
INTRODUCTI
ON
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1. Define CAD.
Computer Aided Design involves any type of design
activity which makes use of computer to develop, analyze or
modify an engineering design. Modern CAD systems are
based on interactive computer graphics.
2. Define data structure.
A data structure is defined as a scheme, logic or a
sequence of steps developed to achieve a certain
graphics, non- graphics and a programming goal.
3. What is a database?
A database is defined as an organized collection of
graphics and non graphics data stored on secondary storage
in the computer.
4. Define automated drafting.
Automated drafting involves the creation of hard
copy engineering drawings directly from the CAD data
base. Graphic features of computer aided design can
increase productivity in drafting function.
5. Define model co ordinate system.
It is defined as the reference space of the model
with respect to which all the model geometric data is stored.
Three types of co ordinate systems are needed in order to
input, store and display model geometry and graphics.
6. Write the functions of design work station.
The functions of design work station are:
i) It must interface with the central processing unit.
ii) It must generate a steady graphic image for the user.
iii) It must provide digital descriptions of the graphic image.
iv) It must translate computer commands into operating
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functions.
v) It must facilitate communication between the user andthe system.
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7. What is a geometric model? Mention its types.
A geometric model is a graphical representation of
an object, using the mathematical database in the
computer. Solid model, surface model and wireframe model
are the types of geometric model.
8. Write the various design tasks performed by CAD system.
The design tasks performed by CAD system
are geometric modeling, engineering analysis, design
review and evaluation and automated drafting.
9. What is the graphic configuration of a
graphic system? The graphic configuration ofa graphic system is,
i) It interacts with the graphics terminal
to create and alter images on the screen.
ii) Construct a model of something
physical out of
the images on the screen. The
models
are sometimes called application models.
iii) Enter the model into computermemory and
or secondary storage.
10. What are functions of a graphic package?
The functions of a graphic package are
generation of graphic elements, transformations,
display control and windowing functions, segmenting
functions and user input functions.
11. List the types of output devices used in conjunction
with computer aided design system.
Pen plotters, hard copy units, Electrostatic
plotters, Computer-output-to-microfilm (COM) units
are the output devices
used in conjunction with computer aided design
system.
12. What are the modules of ICG?
The interactive computer graphics software is
divided into three modules as the graphics package,
application software and application database.
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13. Write the display devices used in computer graphics
application.
Raster scan monitor, LCD monitors and plasma
panel display are the display devices used in
computer graphics application.
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14. Write the display devices used in computer graphicsapplication.
The display devices used in computer graphics
application are Raster scan monitor, LCD monitor and
Plasma panel display.
15. List any two types of output devices used inconjunction with CAD
system.
Graphic Displays and Hard copy Printersand Plotters.
16.Define Recognition of need.
Recognition of need involves the realization by
someone that a problem exists for which some corrective
action should be taken. This might be identification ofsome defect in current machine design by an engineer or
the perception of a new product marketing opportunity by
salesperson. Definition of the problem involves a thorough
specification of the item to be designed. The specification
includes physical and functional characteristics, cost,
quality and operating performance.
17.Write the analysis step of design process
Synthesis and analysis are closely related and highlyiterative in the design process. A certain component or
subsystem of the overall system is conceptualized by the
designer, subjected to analysis, improved through this
analysis procedure and redesigned. The process is repeated
until the design has been optimized within the constraints
imposed on
the designer. The components and subsystems are
synthesized into the
final overall system in a similar iterative manner.
18. what is evaluation?
Evaluation is concerned with measuring the design
against the specifications established in the problem
definition phase. This evaluation often requires the
fabrication and testing of prototype model to assess
operating performance, quality, reliability and other
criteria. The final phase in the design process is the
presentation of design. This includes documentation of the
design by means of drawings, material specifications,
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assembly lists and so on.
19. Write a note on engineeringdesign?
Engineering design has traditionally been accomplished
on drawing boards, with design being documented in the form
of a detailed engineering
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drawing. Mechanical design includes the drawing of the
complete product as well as its components and
subassemblies.
20. Define Electrical design of CAD
Electrical design is concerned with the presentation of
circuit diagrams, specifications of electronic components, and so
on. In each engineering discipline, the approach has traditionally
been to synthesis a preliminary design manually and then to
subject that design to some form of analysis.
UNIT
2
GRAPHICSPACKAGE
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1. Define segmentation.
Segmentation or curve splitting is defined as replacing
one existing curve by one or more curve segments of the
same curve type such that the shape of the composite curve
is identical to that of the original curve.
2. Define transformations.
Transformations are used to change the image on the
display screen and to reposition the item in database.
Transformations are applied to the graphic elements in
order to aid the user in constructing an application model.
3. What is a frame buffer?
A viewing surface of a raster scan display is divided
into an array of pixels. Every pixel in the viewing screen
must be associated with one bit of memory. In this graphics
memory, one bit is associated with each pixel on the display
surface. This memory is called frame buffer.
4. What is a digitizer?
It is an input device used for inputting a serious of x-y
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coordinate pairs. In a CAD environment, digitalizes are used
for two functions viz, inputting maps and drawings into
the system and for creating tablet menus.
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5. Define scanner.
The input device used for inputting images directly is
the scanner, which converts a page into an array of dots
depending on the resolution of the scanner. These dots are
converted to pixels that can be used as inputs.
6. What are the methods adopted to generate text in graphics?
In computer graphics two methods are adopted
to generate text primitive. They are vector generated text
and raster generated.
7. Define scaling.
The image displayed can be reduced or enlarged
using scaling. Scaling can be done either in x or y directionor in both directions simultaneously. Scaling factors can be
specified in x and y directions to carry out scaling.
8. Write the properties of graphical work station.
The properties of graphical workstation are:
i) It has one display surface with a fixed
resolution. ii) The display spaces are
rectangular.
iii) No image is displayed outside the specified display space.
iv) It supports several line types, marker types , text
fonts, character spacing etc.
v) It has one or more logical input devices.
vi) It stores and manipulates segments.
9. List the GKS work stations.
GKS defines six categories of workstations viz,
Output workstation which has display surface for
displaying images. Input workstation with atleast onelogical input device.
Output / Input workstation with a display surface &
atleast one logical input device.
Workstation independent segment
storage (WISS) GKS metafile input &
output.
10. What is a GKS metafile?
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A graphics metafile is defined as mechanism for the
transfer and storage of graphics data, which is both
applicant independent and device independent.
11. Define wireframe model.
A wireframe model is the simplest geometric
modeling type, where an object is described by points,
lines, circles, and curves in 3D representation.
12. Define surface model.
Surface model is similar to wireframe model where an
object is described by surface entities such as B- spline,
Bezier patches, coons patches, ferguson, surfaces,etc.
13. Define solid model.
Solid model is a complete representation of a
surface model where the object is described by solidentities such as blocks, cylinder, cone, sphere, wedge etc.
It can also be compared with an actual or existing
model.
14. Write the functions of GKS.
Regeneration and transformation of imagesImage generated in user co-ordinateControlling the activities of work stationStructuring the cell arrays and there bygenerating images
15. State the advantages of AUTOCAD
Smooth arcs can be drawn to connect two lines.
Objects can be filled with specified pattern or crosshatched.
Aspect ratios can be varied at any time.
Objects can be dragged to vary their locations andsizes.
16. Define pivot point.
The point about which the image is rotated is calledpivot point.
17.What are the types ofmodel
Wireframe model
Surface model
Solid model
18. Define wire framemodeling.
Wireframe models are the simplest of the
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three types of models. They are easy to create and use. They
provide sufficient information on
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solid object. They are normally used to create models of simple
objects. Wire frame models are generated by continuing line
segments
19. Define Surface
Modeling
Surface entities are introduced to the wire frame model in
the surface modeling. Surface models define part geometry
more precisely, compared to wire frame models. An object
generated through surface modeling can be displayed on a screen,
in such a way that it look like a solid object .
20. DefineRotation
The transformation is used to rotate objects or images aboutany point in the world space either clockwise or anticlockwise
direction. The point about which the image is rotated is called
pivot point. These steps are required to perform this operation.
They are
Translate the pivot point xp,yp to the origin
Rotate the translated points by e about the origin
Translate the centre of rotation back to the pivot point
In the first step the points (x,y) get transformed to (x,y),and inthe zsecond step (x,y).In the third step to (x,y).all the line
segments on the objects has to be transformed to get the
complete image rotated about the pivot point xp,y
UNIT 3
STRUCTURALANALYSIS
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1. Define discretization.
The basic concept of the finite element method is that
a body or a structure is divided into smaller elements of
finite dimension called finite elements.
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2. Mention some commercially available software
packages of finite element analysis.
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ABACUS, ADINA, ANSYS, ASKA, COSMOS, GT-
STRUDL, NISA, PAFEC, SAP, SESAM-80 are some of the
available software packages of finite element analysis
3. What is meant by banding of a stiffness matrix?
The adjacent elements of the diagonal matrix
are non zero numbers and the elements far away from
them are non zero numbers.
4. Define nodal point.
The point at which two nodal planes meet is called
node (or) nodal point. Nodes are points at which
different elements are connected to generate the
structure or system.
5. Define general type pre and post processor.
The types of pre and post processors are general
and specific purpose. General purpose type processors canbe coupled to many finite element packages and many even
offer facility to process problems in the field of engineering.
6. Define special purpose type pre and post processor.
The special purpose processor work in connection with
specific finite element analysis package and is usually
available in an integrated form with that package.
7. What is duplication?
Portions of an existing model or the entire model can
be translated, rotated, mirrored or scaled to generate
another portion of the model is called duplication.
8. Write the functions of pre and post processor.
A preprocessor creates the finite element model and
the input necessary for a finite element analysis
program. A post processor program accepts the results of
the analysis and generates tables, diagram/pictures etc for
the interpretation of results.
9. Write the basic steps of finite element analysis.
The basic steps of finite element
analysis are:i) Discretization of a given body or structure into an
assemblage of finite elements.
ii) Derivation of element equations for various types ofanalysis.
iii) Assemblage of elements to obtain the governing
equation for the whole problem.
iv) Solution of the assembled
equations v) Post-processing of
results.
10. What is FEM.
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FEM is a numerical technique for solving boundary value
problem in which one divides the domain of the problem into little
pieces over which the solution is approximated using polynomials.
11. Define shape function.
Shape function is defined as one whose values at a
particular node is unity and other nodes zero.
12. What are the properties of shape function?
i) There will be as many shape functions as there are nodes.
ii) It will have unit at the node in question and zero values at
other nodes. iii) The sum of all the shape functions is unity.
13. List out the advantages of FEM?
Advantages
Since the properties of each element are evaluated
separately we4can incorporate different material properties of
each element
There is no restriction to the shape of the medium.
Any type of boundary condition can be accommodated.
14. List out the disadvantages of FEM?
Disadvantages
The computational cost is more.
The solution is approximate.
15. Define displacement function?
Simple functions which are assumed to approximate the
displacement for each element are called displacement functions.
It may be a function of polynomials, trigonometry or others.
16.Name the types of noded elements
2-noded elements-line
3-noded elements-triangle
4-noded elements-quadrilateral
17. List the Hardware requirements of pre and post processor
Computers-VAX family
Prime family
DEC
HARRIS
APPOLLO
CDC cyber
18. List the various co ordinates of FEM.
I) Local or element co
ordinates
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ii) Natural coordinates
iii) Simple natural co
ordinates iv) Area co
ordinates
v) Generalised coordinates.
19. What are the factors that govern the selection type of finiteelement?
Geometry of the body
Number of independent space coordinates
Nature of stress variation
20. What are the properties of shape function?
No. of shape function=no. of nodes
Values of the nodes in the question =1 and all others mustbe zero
The sum of the shape function is unity
Unit-4
DESIGN ANDOPTIMIZATION
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1. Define objective function.
A function for which an extreme is sought, in theoptional design
process. It is also referred to as merit function. Usually weight,
cost or volume of the structure/solid/component is chosen as the
objective function.
1. What is a design variable?Design Variables are those quantities defining a system andthese are varied to achieve an extremism of the objectivefunction. Generally the Cross-sectional dimensions, thickness,etc are taken as design variables.
2. What is meant by InequalityConstraints?
These constraints usually ensure safety against a failure modeor satisfactory behaviour under the given loading conditions. Thelimits imposed on stress at a section/point not to exceed the
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allowable value and displacement at a node not to exceed thepermissible limits is typical examples for inequality constraints.
3. Define EqualityConstraints.
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These are conditions that must be strictly satisfied
for the design to be acceptable. In the case of solids, the
conditions of equilibrium are to b imposed as equality
constraints, but they are implicit as part of analysis
procedure and are not stated. So it may be noted that the
inequality constraints such as limits in press cannot be
expressed explicitly since it requires a finite element
analysis.
4. What are Side Constraints?
The upper and lower bounds on the design variables are
usually referred to as side constraints. Generally the idle
constraints impose geometric restrictions on the design
variables 10
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generate and test approach.
8. Write short notes on constrained optimization techniques?
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A constrained optimization is concerned with obtaining a
minimum(or maximum) of the objective function to constraints.
The methods of optimization can be classified into two broad
categories: (i)Direct Methods and (ii)Transformation or Indirect
Methods.
9. Write short notes on unconstrained optimization techniques.An unconstrained optimization problem aims at
minimization ( or maximization) of the objective function inthe absence of constraints. The unconstrained optimizationtechnique can be broadly classified into two categories , i)single variable/ unidirectional search techniques and ii) multi-variable optimization techniques.All the algorithms
10. Define Transformation/Indirect Method
These methods transform the constrained optimizationproblem into a sequence of unconstrained optimizationproblems with the motivation to use well establishedunconstrained optimization techniques discussed in theearlier section. The general approach of the indirectmethods will be to minimize (or maximize) the objectivefunctions as an unconstrained function but provide penaltyto limit the constraint violation.
11. Define meta-knowledge.The term meta knowledge refers to knowledge about
knowledge. As the size of the knowledge base grow larger andlarger, and controls strategy become more complex. An ideal
way in this situation is to logically divide the knowledge intosmaller ones, and have a higher level knowledge base, whichcontaining the knowledge about the lower level knowledgebases and problem solving strategy. Knowledge base athigher level is called meta-knowledge.
12. Write the architecture of KBES development tool.
The architecture of KBES development tool consists of Rulebase inference engine which consists of Knowledgeacquisition facility, Data base management system, Framemanagement system, Engineering design synthesis and
Design critic.13. Write the functions of preprocessor?
Reads control parameter.
Reads or generates nodal Coordinates boundaryconditions.
Reads or generates element connectivity and
element loads.
Reads material constants constitutive matrixcoefficients.
Reads nodal loads and loading conditions.14. Write the functions of postprocessor?
Prints/plots deflection shape.
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Prints/plots contours of displacements.
Calculates strains and stresses.
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Prints/plots contours of stresses, Displaysstress bands, maximum and minimumvalues.
15. Write the different gradient based
methods?
Methods od Steepest descent/Ascent
NewtonSearch Method
Conjugate Gradient Method
Method of Flecture and reevs
Quasi-Newton/Variable Metric Methods and under this
category, Davidon-Fletcher-Powell (DFP) method is
reported to be stable and reliable for use.
16. Name the methods ofconstraints
Cutting plane method
Move Limit Method
Method of Feasible Directions
Zontendijk's Method
Gradient Projection Method
Generalized Gradient Projection Method
Pschenichnny's Linearization Method
Quadratic Objective function and Linearized Constraints Sequential Quadratic Programming
Recursive Quadratic Programming
17. What are the Principles of RC design.
Find the strengthconsidering
(A) Strength in yielding of gross area.
(B) Strength in rupture of critical section and
(C) Strength in block shear.
Minimum edge distance and minimum pitch
distances are maintained, strength in yield is the least
value, hence the design is safe.
18. What are the Principles of compression member design.
Select a section togive effective are required and calculate rmin.
Knowing the end conditions and deciding the type of connection
determine effective length. find
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the slenderness ratio and hence the design stress and load
carrying capacity. Revise the section if calculated Pd differs
considerably from the design load.
19. Write the types of optimization techniques.
The types of optimization techniques are constrained
optimization techniques and unconstrained optimization
techniques
20.Define Explanation Facility
Explanation facility is one of the most important
components of the expert system. This provides a mechanism for
the user of the expert system, to get more information on the
inference process. Primarily a user will be looking for four
different pieces of information during and after the inference
process.
UNIT-5
EXPERTSYSTEM
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1.Define Inference Mechanism.
It is impossible to compile the knowledge in a database.
Hence certain components directs to implement it in theknowledge base. It is a search technique. This can be done in 2
types Forward chaining, Backward chaining
2.Define Backward chaining:
In Backward chaining inference mechanism the data
required fed in steps in which it is required. It selects the goal
and scans until the goal is reached.
3. What is an Inference Engine?
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The inference engine, which is nothing but the
implementation of one or more inference mechanisms, carries out
the search through the knowledge base either to prove
hypotheses or to arrive at a conclusion. Depending on the nature
of problem to be solved and the nature of knowledge
contained in the knowledge base, a proper inference
mechanism is I selected and the search is
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carried out. When a prototype expert system is developed
the knowledge engineer decides on the inference strategy to be
selected.
4.Define production rule.
Production rule are based on control knowledge orhieuristic knowledge. The antecedent has a course of action andit is satisfied only then the course of action of antecedent issatisfied.That is RHS is equal to LHS only if the course of action of LHSis satisfied then only the course of action of RHS is satisfied.
Example:IF the environment iscorrosive THEN avoidusing steel columns. IF
flow is open channelAND fraude number is 1THEN flow is critical.
5.What are the common ways of knowledge representation?Knowledge can be represented in many ways. They are
1.Quantitative Method2.Qualitative Method3.Compiled Method
6.What is meant by forward chaining?
In forward chaining, inference mechanism rules arescanned until a goal is achieved. It is done if a rule matches with
the goal or the process is repeated. No data is fed during the
process. The inference mechanism uses the data only from the
working memory.
7.What is meant by Artificial Intelligence?
Artificial Intelligence is the method of acquisition of human
or other animals behavior in solving complex problems. It is the
study in which human act in such a way that he can do all theactivities.
8.Define decision tables.
It is a simple and effective method for controlling the
knowledge-based techniques. It consists of both heiuristic and
initative knowledge basis. The decision table consists of four parts.
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Goal Rule I Rule II Rule III Rule I
9.Write the stages of expert system.
The stages of expert system are identification,
formulation, conceptualization, implementation testing
and validation.
10.Write about the search methods of artificial intelligence.
The search methods used in the area of Artificial Intelligence
are broadly classified into five types. They are,
1. Simple search
2. Evaluation based search
3. Games search
4. Constraint search
5. Controlled search
11. List the common ways of knowledge representation.
The most common ways of knowledge representation are,
Production rules, decision tables, frames, semantic networks,predicate logic, conventional programs.
16. What is RDBMS?
A relational database management system (RDBMS) consists
of a set of programs which can relate relations and manipulate the
data stored in the relations. In a standalone mode, the structured
query language (SQL) is used to query the database to get
required information. In language interface mode, generally SQL
queries are embedded in language.
17. What are the components of KBES?
There are two main components of any KSEB are theknowledge base and inference engine. The inference engine
acts on the knowledge stored in the knowledge base to
carry out reasoning. As the nature of database processing
and knowledge processing is different, the strategy adopted
for embedding DBMS in programming language cannot be
adopted here; Databases are created either in standalone
mode or through programs.
18. What is hill climbing techniques
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Hill climbing is an example of an informed search method
because it uses information about the search space to search
in a reasonably efficient manner. If you try to climb a
mountain in fog with an altimeter but no map, you might use
the hill climbing generate and test approach.
19. Define Working Memory
Working memory, which is also sometimes called context, is
nothing but a workspace for the problem, generated by the
inference engine, from the information provided by the user. Many
hypotheses and facts are established during the reasoning
process. These are stored in the working memory. The information
available in the working memory are used for continuing with the
inference process using the knowledge contained in the
knowledge base. The explanation facility also uses the information
in the working memory, to answer the queries of the user.
20.Define Knowledge Acquisition Facility
A knowledge acquisition facility is an optional component
of an expert system. This very much depends on the expertsystem development tool used to implement the system. Any text
editor can be viewed as a knowledge acquisition facility, since it
provides an environment for the knowledge engineer or the expert
to input the coded knowledge into the system. Many development
shells allow the development engineers to code the formal
presentation of the knowledge in a text file, following a specified
syntax. Later, the knowledge in the text files are converted into a
form of data and stored in a data structures for carrying out
reasoning process.