What is the difference between trapezoidal load and hydrostatic load?

Slab pressure loads (Kn/m2) are transferred to supporting beams as line load (kn/m) which can be triangular, trapezoidal, or partially distributed. Slab having two unequal sides distribute trapezoidal load on longer side beam.

Hydrostatic load: The pressure exerted by a fluid at equilibrium at a given point within the fluid, due to the force of gravity. Hydrostatic pressure increases in proportion to depth measured from the surface because of the increasing weight of fluid exerting downward force from above. Hydrostatic load can be trapezoidal but trapezoidal load cannot be hydrostatic. Because hydrostatic load occur due to water.

Is it necessary to correct warnings in Staad Pro?

Is it necessary to correct warnings in Staad Pro?

HOW CAN I TAKE LOAD COMBINATIONS IN STAAD PRO?

StaadPro Analysis methods

STAAD.Pro offers several analysis methods as noted below:

• Perform Analysis - instructs STAAD to perform a linear elastic (stiffness) analysis.

• P-Delta Analysis - performs a second-order elastic analysis that considers the effects of the applied loads acting on the displaced structure (P-Δ effect). This type of analysis is generally preferred by most building codes. This is an iterative analysis process. This analysis type also has options to specify the number of iterations to be performed or to place a convergence tolerance on the displacements from successive iterations. There is also an option to include the P-δ (small delta) effect, which considers the effect of applied loads acting on the deformed shape of individual members. Finally, this analysis includes an option to include the Geometric Stiffness (Kg) matrix, which modifies the member stiffnesses based on the applied loads.

• Cable Analysis - performs a non-linear cable analysis on a structure that contains non-linear cable members

• Direct Analysis - performs a Direct Analysis. This method accounts for the second-order effects resulting from deformation in the structure due to applied loading, imperfections, and reduced bending stiffness of members due to the presence of axial loads. This analysis is similar to a P-Delta Analysis with the Use Geometric Stiffness (Kg) and Small Delta options selected. However, this analysis calculates modifications to the stiffness matrix using the τb factors described in AISC 360-05.

• Generate Floor Spectrum - used to request the calculation of floor and/or joint response spectra from time history results. This is particularly useful in the analysis of floor systems supporting vibrating equipment. This feature requires a license for the Advanced Analysis Engine.

• Imperfection Analysis - considers the secondary effects of loads acting on members that have an initial curvature (camber) or an initial drift This analysis is used on structures that have members with an Imperfection specification applied to them.

How do I change the font settings in STAAD.Pro?

What is the command to delete text in STAAD.Pro?

What is the meaning of ‘cut off mode 150’ in STAAD software?

CUT OFF MODE 150 means the user has requested the software to consider 150 modes for the dynamic analysis. By default the software considers 6 modes and in case more number of modes are required to get enough mass participation (greater than 90% is recommended by most codes), user can do so by using the CUT OFF MODE command. More details are available in technical reference section 5.30.1.

What is Beta Angle in Staadpro?

Beta Angle
When the local x-axis is parallel to the global Vertical axis, as in the case of a column in a structure, the beta angle is the angle through which the local z-axis (or local Y for SET Z UP) has been rotated about the local x-axis from a position of being parallel and in the same positive direction of the global Z-axis (global Y axis for SET Z UP).
When the local x-axis is not parallel to the global Vertical axis, the beta angle is the angle through which the local coordinate system has been rotated about the local x-axis from a position of having the local z-axis (or local Y for SET Z UP) parallel to the global X-Z plane (or global X-Y plane for SET Z UP)and the local y-axis (or local z for SET Z UP) in the same positive direction as the global vertical axis. Figure details the positions for beta equals 0 degrees or 90 degrees. When providing member loads in the local member axis, it is helpful to refer to this figure for a quick determination of the local axis system.

Material constant in Staadpro

The material constants are:

modulus of elasticity (E);

weight density (DEN);
Poisson's ratio (POISS);

co-efficient of thermal expansion (ALPHA),

Composite
Damping Ratio, and

beta angle (BETA) or coordinates for any reference (REF) point.

E value for members must be provided or the analysis will not be performed.
Weight density (DEN) is used only when selfweight of the structure is to be taken into account.

Poisson's ratio (POISS) is used to calculate the shear modulus (commonly known as G) by the formula,
G = 0.5⋅E/(1 + POISS)

If Poisson's ratio is not provided, STAAD will assume a value for this quantity based on the value of E.

Coefficient of thermal expansion (ALPHA) is used to calculate the expansion of the members if temperature loads are applied. The temperature unit for temperature load and ALPHA has to be the same.
Composite damping ratio is used to compute the damping ratio for each mode in a dynamic solution. This is only useful if there are several materials with different damping ratios.

How to define constant for concrete structure in staadpro editor?

If all members are in concrete. Than after defining properties you have to define constants. In editor you can define constant command as given below:

CONSTANT

E CONCRETE ALL

DENSITY CONCRETE ALL

POISSON CONCRETE ALL

BETA 40.37 MEMB 62

Where last line is just example showing 40.37 angle and 62 is member number.

StaadPro editor command for concrete member property

The following example shows the required input:

UNIT INCH
MEMBER PROPERTY
1 3 TO 7 9 PRISM YD 18. ZD 12. IZ 2916 IY 1296
11 13 PR YD 12.
14 TO 16 PRIS YD 24. ZD 48. YB 18. ZB 12.
17 TO 19 PR YD 24. ZD 18. ZB 12.

In the above input, the first set of members are rectangular (18 inch depth and 12 inch width) and the second set of members, with only depth and no width provided, will be assumed to be circular with 12 inch diameter. Note that no area (AX) is provided for these members.

The third and the fourth set of members in the above example represent a Tshape and a TRAPEZOIDAL shape respectively. Depending on the properties (YD, ZD, YB, ZB, etc.) provided, the program will determine whether the section is rectangular, trapezoidal or T-shaped and the BEAM design will be done accordingly.

How do i define Prismatic Properties in Staad?

The following prismatic properties are required for analysis:

• AX = Cross sectional area
• IX = Torsional constant
• IY = Moment of inertia about y-axis.
• IZ = Moment of inertia about z-axis.

In addition, the user may choose to specify the following properties:

• AY = Effective shear area for shear force parallel to local y-axis.
• AZ = Effective shear area for shear force parallel to local z-axis.
• YD = Depth of section parallel to local y-axis.
• ZD = Depth of section parallel to local z-axis.

For T-beams, YD, ZD, YB & ZB must be specified. These terms, which are shown
in the next figure are:

• YD = Total depth of section (top fiber of flange to bottom fiber of web)
• ZD = Width of flange
• YB = Depth of stem
• ZB = Width of stem

Prismatic property nomenclature for a T and Trapezoidal section

For Trapezoidal beams, YD, ZD & ZB must be specified. These terms, which too
are shown in the next figure are:

• YD = Total depth of section
• ZD = Width of section at top fiber
• ZB = Width of section at bottom fiber

Top & bottom are defined as positive side of the local Z axis, and negative side of
the local Z axis respectively.

STAAD automatically considers the additional deflection of members due to pure
shear (in addition to deflection due to ordinary bending theory). To ignore the
shear deflection, enter a SET SHEAR command before the joint coordinates. This
will bring results close to textbook results.
The depths in the two major directions (YD and ZD) are used in the program to
calculate the section moduli. These are needed only to calculate member stresses
or to perform concrete design. You can omit the YD & ZD values if stresses or
design of these members are of no interest.

To define a concrete member,you must not provide AX, but instead, provide YD
and ZD for a rectangular section and just YD for a circular section. If no moment
of inertia or shear areas are provided, the program will automatically calculate
these from YD and ZD.

Required Section Properties

Table is offered to assist the user in specifying the necessary section values. It
lists, by structural type, the required section properties for any analysis. For the
PLANE or FLOOR type analyses, the choice of the required moment of inertia
depends upon the beta angle. If BETA equals zero, the required property is IZ.

How do I change a cover to a reinforcement for beams and columns in STAAD.Pro V8i?

Got to Commands- Concrete Design- Design parameters-Clear

Cover to reinforcement

How to Specify member properties graphically in Staadpro?

• To define member properties, click on the Property Page icon located on the top toolbar.

Alternatively, one may go to the General | Property page from the left side of the screen as shown below.

• In either case, the Properties dialog box comes up (see figure below). The property type we wish to create is the W shape from the AISC table. This is available under the Section Database button in the Properties dialog box as shown below. So, let us click on the Section Database button.

or

For beam and column properties in Rcc structure you have to click on Define button next to Section Database.

• In the Section Profile Tables dialog box that comes up, select W Shape under the American option. Notice that the Material box is checked. Let us keep it that way because it will enable us to subsequently assign the material constants E, Density, Poisson, etc. along with the cross-section since we want to assign the default values.
  Choose W12X35 as the beam size, and ST as the section type. Then, click on the Add button as shown in the figure below.
  

or

For beam and column properties in Rcc structure after clicking on Define button next to Section Database you get dialog box as shown below. Click on Rectangle for rectangular properties.

How do I change the sizes of reinforcement bars for beams and columns in STAAD.Pro V8i?

Go to Commands - Design - Concrete Design

Concrete design command

On right side small window appear, Under current code select your code

Select code

Click on Define Parameters- in left panel click on MD1 & MD2

how to check The Dead load as per Staad for no of floors

1. Self weight (columns,beams and shear walls for the entire building)
2. Brickwall over the exterior beams except on shear wall only are added.
3. The dead load on slab- Self weight of slab+Finish+Construction load +15% for furniture, staircase, water tank etc is added with an intensity of 6KN/Sq.m.

A manual check for these items are carried out as:

• Dead load: Area of floor x no. of floors x intensity of load
• Brickwall load:
  
  
  
  
  Total length of beam in one floor =
  Load per floor =
  Load due to brickwall alround exterior beams =
  Load due to Parapet 1.0 m height of 4.5” wall=
  Total dead load due to brickwall =
• SELF WEIGHT OF:
  • COLUMNS =
  • Beams for all floors
  • Shear wall:

HOW TO DO MANUAL CHECK AGAINST STAAD RESULTS FOR SEISMIC FORCES?

Example
The structure is 36x21m and is symmetrical in x and Z direction as well as in vertical elevation and its total height from the footing is 74m.(21 storey)

The building is in Zone III and the time period as per IS 1893-2002(PartI) for infill is taken 0.09h/√d.

After analysis through STAADPRO the followings check is carried out to verify and check the results between manual calculation and the software results.




-------------------------------------------------------------------------------------------------

A. TIME PERIOD:

As per IS CODE 1893-2002(Part I) T =0.09h/ √d where d is the direction along the EQ forces.
Tx =0.09x74/ √36 =1.11 Sec.
Tz =0.09h/ √21 =1.453 Sec.

The output of STAADPRO is

TIME PERIOD FOR X 1893 LOADING = 1.11000 SEC
TIME PERIOD FOR Z 1893 LOADING = 1.45333 SEC
******************************************************************************************

Manual checking of Staadpro output

LOADS:

Correct assessment of loads both dead and live loads are important since excessive assumed loads may lead to uneconomical member sizes and footing sizes. Also excessive loads will be adding more weight in the case of seismic forces.
In order to have equilibrium i.e .ΣV=0 under the Load case DEAD LOAD calculate the total dead load on all floor slabs and check it against the output by the program.

METHOD TO CHECK:

Using a single support for the whole structure RUN the ANALYSIS and find out the total support reaction in Y axis i.e FY from the output of the program. Check whether the above two values are in agreement to the manually calculated values. If the results vary then there is some error or mistake took place while entering the input.
The same procedure can be carried out for the LIVE LOAD for both FLOOR LIVE LOAD and ROOF LIVE LOAD cases also.

If the single support is not considered or modeled then use all the supports and copy the values of Fy to EXCEL and get the sum of the FY and check whether it tallies with the manually calculated values.

WIND LOAD:

To find the point load FX or FZ at a joint as nodal wind force calculate the tributary area for the corresponding node and multiply it with the intensity of loading.
For example:
Area = (h1+h2)/2*(L1+L2)/2* intensity of loading.
Please note that the consistence unit shall be used.
Where h1 and h2 are the height above and below the joint in meters and L1 and L2 are the width of the bay on either side of the node in meter units.

If      h1 =4.0m
and h2=3.0m,

         L1=5.0m

and L2=6.0m

then the tributary area for the node is
=(4+3)/2*(5+6)/2 = 19.25sq.m.

Using an intensity of 1KN/sq.m the nodal force shall be =19.25 KN.

This can be verified with the values generated by the program.

SUPPORT CONDITIONS:

Usually while modeling a structure either FIXED or HINGED support condition is proposed. If the support condition is FIXED the there shall be six restraints i.s. FX,FY ,FZ, Mx, My and Mz
For HINGED there shall be no moments. In order to account for the soil spring the modulus of subgrade reaction Ks has to be considered for the support condition.

Ref:  by T.Rangarajan

Manual checking of Staadpro inputs

Model checking

It is important to check the UNITS at every stage while modeling since it may lead to a unexpected error in the output. While modeling use of length units may be in meter for beam, column and plate and while entering the properties it is usual practice to make use of either mms or inch unit . While inputting the LOADS on members check the UNIT system is in KN and meter system since the program continues to use the previous unit till it is changed.

Before inputting the LOADS to the structure facility is available in STAADPRO as per the screen shot.

• Check Multiple Structures.

Some times by mistake the user would have without his knowledge created too many members and structure. Better use this tool menu to remove the multiple structures. It is the responsibility of the applicator to verify that there exists only one structure and not more than it for any model.

Check for multiple structure in Staadpro

How to see Reinforcement details in Staad.pro?

After you run analysis you can either see in output or postprocessing.

• First method

As shown in figure below to see output u have to click on icon

OUTPUT FILE OF STAADPRO

You will see concrete design option on left click on that

BEAM REINFORCEMENT RESULT IN STAADPRO

You can see reinforcement on right side.

• Second method

or you can see in postprocessing also. Run analysis , go to postprocessing. Than click on beam or column whose reinforcement you want to see. small window will open. Click on concrete design there you can see reinforcement.

BEAM REINFORCEMENT IN POSTPROCESSING IN STAADPRO