MODULE 5: STRUCTURAL ANALYSIS FOR STRESS RESULTANTS Flashcards
the ability to conduct rapid calculations enabled structural engineers to produce multiple design iterations to fit the requirements of cost and safety, at a degree of relative accuracy
COMPUTER-AIDED STRUCTURAL ANALYSIS AND DESIGN
most commonly recognized structural analysis and design software include:
- Bently Staad.Pro
- Autodesk Robot Structural Analysis Professional
- Csi ETABS, SAFE, and SAP software
- Strand7 - Finite Element Analysis
- Trimble Tekla Structures
- Some Filipino authored software like FrameCE
meaning of FEM
FINITE ELEMENT METHOD
a popular technique for numerically solving differential equations in engineering and mathematics.
FINITE ELEMENT METHOD
the classic domains of structural analysis, heat transfer. fluid flow, mass transport, and electromagnetic potential are typical areas of its application.
FINITE ELEMENT METHOD
Its a genetic numerical approach for solving partial differential equations with two or three variables in two or three dimensions.
FINITE ELEMENT METHOD
The process is further simplified by subdividing a large/complex structure into smaller components called as _____________
FINITE ELEMENT
The process of subdividing a large/complex structure into smaller components
DISCRETIZATION
the resulting finite elements also known as _________
DISCRETE ELEMENTS
In structural engineering, one of the basic examples of this process (DISCRETIZATION) can be observed in the analysis of _________
STRUCTURAL SLAB ELEMENTS
Instead of discretization, it is commonly preferred to use the term __________ for slab elements
MESHING
For regularly, shaped slabs, ______________ is preferred, while for complex slab geometry, such as when there is the presence of slab opening, __________ is preferred.
RECTANGLE/SQUARE MESH
TRIANGULAR MESH
It is important to take note that the ______ of the mesh matters, as the results may be more accurate for ___________ mesh units but would require additional computation.
SIZE
SMALLER SIZED
The structural engineer must them choose the balance between ___________ and the ____________ needed for the project.
CALCULATION SPEED
LEVEL OF ACCURACY
It is also equally important that the ______________ must be considered, since different __________ may produce different _________
ARRANGEMENT/ORIENTATION OF MESH
ARRANGEMENT
RESULTS
One of the methods of structural analysis, a matrix method that makes use of the members’ stiffness relations for computing member forces and displacements in structures and is particularly suited for computer-automated analysis of complex structures including the statically indeterminate type.
DIRECT STIFFNESS METHOD
Direct stiffness method is also known as ________
MATRIX STIFFNESS METHOD
___________ is the one of the implementations of the finite element method (FEM). In applying the method, the system must be modeled as a set of simpler, idealized elements interconnected at the nodes, also known as __________
DIRECT STIFFNES METHOD
ANALYTICAL MODEL
is commonly made up of basic elements such as nodes, beams, and plate elements
ANALYTICAL MODEL
Analytical modelling in staad can be done in multiple ways:
- modelling using the USER INTERFACE (UI) DRAWING AREA
- modelling using the COMMAND LINE EDITOR
- modelling using STRUCTURAL WIZARD
- IMPORTING DXF FILES of the analytical model
__________________ is where the model is built completely through the available UI commands of the software itself to add STAAD elements, which includes: ________
USER INTERFACE (UI) DRAWING AREA
-NODES
-BEAMS
-PLATES
-SURFACE
-SOLIDS
where the model information can be typed, not relying entirely on the UI itself
COMMAND LINE EDITOR
where the whole or parts of the model is created using predefined structural configurations, like common frames, truss models and others.
STRUCTURAL WIZARD
modelling processes:
- ADDITION OF NODES AS ELEMENT BOUNDARY CONDITIONS
- ADDITION OF BEAMS AND/OR PLATES USING THE NODES BOUNDARY CONDITIONS
- ADDITION OF STRUCTURAL RESTRAINTS OR SUPPORTS
- ASSIGNMENT OF ELEMENT PROPERTIES SUCH AS SECTION PROPERTY MATERIALS, DIMENSIONS AND ROTATIONS
- ASSIGNMENT OF LOADS
nodes can be modelled using the _________ or the tabulation of coordinates
DRAWING AREA
Beams can be added using the _________ or by using the tabulation to indicate the __________, and other properties such as the id of the material properties and others
MOUSE CURSOR
NODE INCIDENCES
________ are modelled at the location of the nodes coinciding the location of actual footing or foundation
supports can be modelled as _________ and others
SUPPORTS RESTRAINTS
FIXED, PINNED, SPRING
______________ are included in Staad. One can just utilize these predefined properties without manually creating said properties
AISC COMMON STEEL SECTIONS
Load in Staad can either be ___________ or _________ of load
PRIMARY
COMBINATION
code-based inputs like directional wind and or static force procedure for seismic are treated as ____________
LOAD DEFINITIONS
the capacity of a compression member, element, or frame to remain in position and support load, even if forced slightly out of line or position by an added lateral force. Galambos, 1998
STABILITY
Most steel structures are governed by stability limit states:
- GEOMETRICAL IMPERFECTIONS
- MEMBER INELASTICITY
- CONNECTION RIGIDITY
- SECOND ORDER EFFECT
out of plumbness of frame
member cambers
GEOMETRICAL IMPERFECTIONS
Plastic behavior of steel
MEMBER INELASTICITY
procedures of stability analysis:
- 1ST ORDER ANALYSIS METHOD
- EFFECTIVE LENGTH METHOD (ELM)
- DIRECT ANALYSIS METHOD (DAM)
pure structural analysis
“perform” analysis, run
1ST ORDER ANALYSIS METHOD
second order analysis/ higher order analysis:
- EFFECTIVE LENGTH METHOD (ELM)
- DIRECT ANALYSIS METHOD (DAM)
1st order analysis method
with second order analysis (P-delta effect)
calculation of K factor
EFFECTIVE LENGTH METHOD (ELM)
1st order analysis method
with second order analysis (P-delta effect)
inclusion of “notional load”
inelastic behavior of sections
DIRECT ANALYSIS METHOD (DAM)
meaning of SCM in table 2-2 Steel Construction Manual 14th edition
SUMMARY COMPARISON OF METHODS
a non-linear effect that occurs in structures that are subjected to compression load and lateral displacement
P-DELTA EFFECT
two types of p-delta effect:
P-(TRIANGLE) EFFECT / P-“BIG-DELTA”
P-(GAMMA) EFFECT / P-“SMALL-DELTA”
- associated with displacements of the member ends when the whole structure is taken into consideration
- “global” or “per system”
P-(TRIANGLE) EFFECT / P-“BIG-DELTA”
- associated with local deformation relative to the element chord between end nodes
- “local” or “per member”
P-(GAMMA) EFFECT / P-“SMALL-DELTA”
effect of loads acting on the displaced location of joints or nodes in a structure
P-BIG DELTA
effect of loads acting on the deflected shape of a member between joints or nodes
P-SMALL DELTA
For older versions of the code, ___________ is recommended
EFFECTIVE LENGTH METHOD (ELM)
_____ FOR NEWER VERSION
DIRECT ANALYSIS METHOD (DAM)
advantages of “direct analysis”
- straight forward approach to stability analysis and design
- small and big delta are accounted
- geometric imperfections are accounted (through the inclusion of notional loads)
- inelastic effect are accounted for (through reduction of flexural and axial stiffness)
- applicable to all types of structures
- applicable to all any 2nd to1st order effect ratio
capacity of compression member
STABILITY
Compression member
COLUMNS
deflection/imperfection of members in manufacturing process
CAMBERS
change of shape of steel under earthquake
PLASTIC BEHAVIOR OF STEEL
induced lateral load due to gravity load
P-DELTA EFFECT
axial causing more deflection
know if the structure is stable/unstable
P-DELTA EFFECT
number of iterations?
minimum of 10 iterations
set a limit
if iterations are increasing
DIVERGENCE (collapse)
if iterations are decreasing and approaching to zero
CONVERGENCE OF DEFLECTION (STABLE)
loads resulting from inaccuracies and imperfections introduced into the structure during its construction
NOTIONAL LOAD
