Input
Geometry Input Load Input
Material Input

 

This is a web-app that analyzes precast prestressed stadium riser sections, which are not symmetrical about their vertical axis, contrary to most precast concrete elements. Once the user inputs all necessary information and clicks the 'Analyze' button, the app:

The dimensions which should be input in the boxes are shown in the figures. Other input parameters are:

Please use . not , for decimal points

 

Analysis Results
Component design data

 

Determination of principal axes

Principal axes are the set of axes, not necessarily axes of symmetry, for which the second moment of area is zero. It is necessary to determine the principal axes and their orientation with the horizontal axis to analyze unsymmetric sections.

 

Coordinates of extreme section points, in

 

Rotated section properties and moments
  • ex' = Eccentricity of center of gravity of prestressing strands with respect to X'-X' axis
  • ey' = Eccentricity of center of gravity of prestressing strands with respect to Y'-Y' axis
  • ds = Approximate effective depth of center of gravity of mild steel
  • Mx'ps, Mx'ns = Moment about X'-X' axis with positive and negative sway, respectively
  • My'ps, My'ns = Moment about Y'-Y' axis with positive and negative sway, respectively

 

Stresses at extreme points, ksi

At this section, stresses at extreme points at mid-span are calculated for positive sway and negative sway. These stresses are checked to stay within limits of allowable compressive and tensile stresses that are given below. If the stresses exceed these limits, the user is warned by way of red colored output boxes and either the member dimensions or the prestressing design of the member should be changed to satisfy stress requirements.

  • Compressive stress limit = 0.60fc'
  • Tensile stress limit = 12√fc'
  • Compressive stresses are positive

With positive sway, ksi

 

With negative sway, ksi

 

Flexural strength analysis

At this section, flexural strength of the section is determined iteratively (Secant Method) for flexure about X'-X' and Y'-Y' axes. Figure below shows the following parameters at section equilibrium:

  • dnaX', dnaY' = Depth of neutral axis for flexure about X'-X' and Y'-Y' axes, respectively
  • dsX', dsY' = Depth of centroid of strands for flexure about X'-X' and Y'-Y' axes, respectively
  • aX', aY' = Depth of compression block for flexure about X'-X' and Y'-Y' axes, respectively
  • εc = Strain at extreme concrete compression fiber
  • εsX', εsY' = Strain at prestressing strands fiber for flexure about X'-X' and Y'-Y' axes, respectively
  • CX', CY' = Compressive resultant force for flexure about X'-X' and Y'-Y' axes, respectively
  • TX', TY' = Tensile resultant force for flexure about X'-X' and Y'-Y' axes, respectively
  • MnX', MnY' = Moment capacity of the section about X'-X' and Y'-Y' axes, respectively
  • MuX', MuY' = Moment demand on the section about X'-X' and Y'-Y' axes, respectively
  • McrX', McrY' = Cracking moment about X'-X' and Y'-Y' axes, respectively

Flexural analysis about X'-X' axis

 

 

Flexural analysis about Y'-Y' axis

 

Checking interaction

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