PSC Design Parameters
Use this function to define the design parameters i.e. types of tendon, bridge type, construction type, output parameters etc.
From the Main Menu select PSC > Design Parameters.
AASHTO LRFD-17
Design Code
Display the design code selected for PSC Design.
Tendon Type
AASHTO LRFD 8th Edition (2017) code gives different stress limits for different types of prestressing tendons (Refer to Table 5.9.2.2-1 of AASHTO LRFD 2017.). Select the Tendon type provided in bridge from:
Low Relaxation Tendons
Stress Relieved Tendons
Prestressing Bars (Deformed High Strength Bars)
Corrosive Condition
In order to determine the tensile stress limits in prestressed concrete at service limit state, select the corrosive condition from:
(Refer to Table 5.9.2.3.2b-1 of AASHTO LRFD 2012.)
Severe
Moderate/Mild
Flexural Strength
Tensile stress of prestressing steel fps can be calculated by code or strain compatibility.
Code: Tensile stress fps is calculated by the equation as per AASHTO-LRFD 2017 for bonded and unbonded tendon respectively.
For bonded type tendon (Refer to the equation 5.6.3.1.1-1 of AASHTP LRFD 2017.)
For unbonded type tendon (Refer to the equation 5.6.3.1.2-1 of AASHTP LRFD 2017.)
Strain Compatibility: Tensile stress fps is calculated by the stress-strain relationship. (Refer to clause 5.6.3.2.5 of AASHTO LRFD 2017.)
Note
When flexure strength option is entered as Strain Compatibility and unbonded type tendons are entered, tensile stress will be calculated by Code instead of Strain Compatibility method. It is because strain compatibility method is valid only for fully bonded tendons.
Exposure Factor for
Crack Width
Select the appropriate exposure factor to calculate the maximum spacing of reinforcement, s_max, for the control of cracking. (Refer to the clause 5.6.7 of AASHTO LRFD 2017.)
Class I(1.0): Exposure factor = 1.0 as per Class I exposure condition
Class II(0.75): Exposure factor = 0.75 as per Class II exposure condition
User: User defined exposure factor.
Construction type
For the segmental bridges, special provision as per the clause 5.12.5 of AASHTO LRFD 2017 is applied. Also in order to determine the tensile stress limits in prestressed concrete, Bridge type needs to be selected. (Refer to Table 5.9.2.3.1b-1 and 5.9.2.3.2b-1 of AASHTO LRFD 2017.)
Segmental: Segmentally constructed bridges
Non-Segmental: Other than segmentally constructed bridges
Output Parameters
midas Civil produces PSC Design results for service limit state and strength limit state. User can select the parameters of interest for output display from the following list:
At Construction Stage/Service loads
Stress by Construction Stage
Stress by Service Load Combinations
Stress in Prestressing Tendons
Principal Stress by Construction Stage
Principal Stress by Service Load Combinations (Max. Shear)
Principal Stress by Service Load Combinations (Max. Torsion)
Check Crack
At Factored Loads
Flexural Strength Check
Shear Strength Check
Combined Shear and Torsion Check
AASHTO LRFD-12
Design Code
Display the design code selected for PSC Design.
Tendon Type
AASHTO LRFD 6th Edition (2012) code gives different stress limits for different types of prestressing tendons (Refer to Table 5.9.3-1 of AASHTO LRFD 2012.). Select the Tendon type provided in bridge from:
Low Relaxation Tendons
Stress Relieved Tendons
Prestressing Bars (Deformed High Strength Bars)
Corrosive Condition
In order to determine the tensile stress limits in prestressed concrete, select the corrosive condition from:
(Refer to Table 5.9.4.1.2-1 and 5.9.4.2.2-1 of AASHTO LRFD 2012.)
Severe
Moderate/Mild
Flexural Strength
Tensile stress of prestressing steel fps can be calculated by code or strain compatibility.
Code: Tensile stress fps is calculated by the equation as per AASHTO-LRFD 2012 for bonded and unbonded tendon respectively.
For bonded type tendon (Refer to the equation 5.7.3.1.2-1 of AASHTP LRFD 2012.)
For unbonded type tendon (Refer to the equation 5.7.3.1.1-1 of AASHTP LRFD 2012.)
Strain Compatibility: Tensile stress fps is calculated by the stress-strain relationship. (Refer to clause 5.7.3.2.5 of AASHTO LRFD 2012.)
Note
When flexure strength option is entered as Strain Compatibility and unbond type tendons are entered, tensile stress will be calculated by Code instead of Strain Compatibility method. It is because strain compatibility method is valid only for fully bonded tendons.
Exposure Factor for
Crack Width
Select the appropriate exposure factor to calculate the maximum spacing of reinforcement, s_max, for the control of cracking. (Refer to the clause 5.7.3.4 of AASHTO LRFD 2012.)
Class I(1.0): Exposure factor = 1.0 as per Class I exposure condition
Class II(0.75): Exposure factor = 0.75 as per Class II exposure condition
User: User defined exposure factor.
Construction type
For the segmental bridges, special provision as per the clause 5.14.2 of AASHTO LRFD 2012 is applied. Also in order to determine the tensile stress limits in prestressed concrete, Bridge type needs to be selected. (Refer to Table 5.9.4.1.2-1 and 5.9.4.2.2-1 of AASHTO LRFD 2012.)
Segmental: Segmentally constructed bridges
Non-Segmental: Other than segmentally constructed bridges
Output Parameters
midas Civil produces PSC Design results for service limit state and strength limit state. User can select the parameters of interest for output display from the following list:
At Construction Stage/Service loads
Stress by Construction Stage
Stress by Service Load Combinations
Stress in Prestressing Tendons
Principal Stress by Construction Stage
Principal Stress by Service Load Combinations (Max. Shear)
Principal Stress by Service Load Combinations (Max. Torsion)
Check Crack
At Factored Loads
Flexural Strength Check
Shear Strength Check
Combined Shear and Torsion Check
AASHTO LRFD-07
Design Code
Display the design code selected for PSC Design.
Tendon Type
AASHTO LRFD-07 code gives different stress limits for different types of prestressing tendons (Refer to Table 5.9.3-1 of AASHTO LRFD-07 with 2008 interim, Customary U.S. Units).
Select the Tendon type provided in bridge from:
Low Relaxation Tendons
Stress Relieved Tendons
Prestressing Bars
Corrosive Condition
Select the corrosive condition from:
Severe
Moderate/Mild
Flexural Strength
Flexural strength to be computed based on:
Code: Clause 5.7.3.2 of AASHTO LRFD-07
Strain Compatibility: For more precise calculations moment resistance is calculated iteratively using strain compatibility approach. (refer to clause 5.7.3.2.5 of AASHTO LRFD-07)
Bridge
type
As per AASHTO LRFD-07,Select the bridge type from:
Fully PSC: Resistance only from prestressing tendons and concrete considered. No cracking is permitted.
Partially PSC: Resistance from prestressing tendons, reinforcement and concrete considered. Cracks within a control limit are allowed in this type of bridge.
Exposure Factor for
Crack Width
Select the appropriate exposure factor based on AASHTO LRFD-07, from:
Class I(1.0): Exposure factor = 1.0 as per Class I exposure condition
Class II(0.75): Exposure factor = 0.75 as per Class II exposure condition
User: User defined exposure factor.
Construction type
As per AASHTO LRFD-07, stress limits for fully/partially prestress concrete are different for segmentally and non-segmentally constructed bridges. Select the construction type from:
Segmental
Non-Segmental
Output Parameters
midas Civil produces PSC Design results for service limit state and strength limit state.
User can select the parameters of interest for output display from the following list:
At Construction Stage/Service loads
Stress by Construction Stage
Stress by Service Load Combinations
Stress in Prestressing Tendons
Principal Stress by Construction Stage
Principal Stress by Service Load Combinations (Max. Shear)
Principal Stress by Service Load Combinations (Max. Torsion)
Check Crack : Only if Partially PSC bridge type
At Factored Loads
Flexural Strength Check
Shear Strength Check
Combined Shear and Torsion Check
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all the output parameters
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all the output parameters.
Design Code
Display the design code selected for PSC Design.
Tendon Type
CSA-S6S1-2010 code gives different stress limits for different types of prestressing tendons (Refer to Table 8.2 of CSA-S6S1-2010.). Select the Tendon type provided in bridge from:
Low Relaxation Strand
Smooth High-strength Bar
Deformed High-strength Bar
Flexural Strength
Tensile stress of prestressing steel fps can be calculated by code or strain compatibility.
Code: Tensile stress fps is calculated by the equation as per the clause 8.8.4.2 of CSA-S6S1-2010 for bonded and unbonded tendon respectively.
For bonded type tendon
For unbonded type tendon
Strain Compatibility: Tensile stress fps is calculated by the stress-strain relationship. (Refer to clause 8.8.3 of CSA-S6S1-2010.)
When εp ≤ 0.008:
fps = Epεp
When εp > 0.008
Grade 1760
Strands: 
Grade 1860
Strands: 
Note
When flexure strength option is entered as Strain Compatibility and unbond type tendons are entered, tensile stress will be calculated by Code instead of Strain Compatibility method. It is because strain compatibility method is valid only for fully bonded tendons.
Reinforcing Rebar
In order to determine the crack width w, select reinforcing steel type from:
(Refer to the clause 8.12.3.2 of CSA-S6S1-2010.)
Epoxy-coated Rebar: kb shall be taken as 1.2.
All Other Components: kb shall be taken as 1.0.
Environmental Exposure
Select the appropriate environmental exposure to determine the maximum crack width, w_max. (Refer to the clause 8.12.3.1 of CSA-S6S1-2010.)
De-icing Chemicals; Spray or Surface Runoff Containing De-icing Chemicals; Marine Spray; Swamp; Marsh; Salt Water; Aggressive Backfill: Maximum crack width = 0.15 mm
Other Environmental Exposure: Maximum crack width = 0.20 mm
Construction type
For the segmental bridges, special provision as per the clause 8.22 of CSA-S6S1-2010 is applied. Also in order to determine the tensile stress limits in prestressed concrete, Bridge type needs to be selected. (Refer to the clause 8.8.4.6 of CSA-S6S1-2010.)
Segmental: Segmentally constructed bridges
Non-Segmental: Other than segmentally constructed bridges
Output Parameters
midas Civil produces PSC Design results for service limit state and strength limit state. User can select the parameters of interest for output display from the following list:
At Construction Stage/Service loads
Stress by Construction Stage
Stress by Service Load Combinations
Stress in Prestressing Tendons
Principal Stress by Construction Stage
Principal Stress by Service Load Combinations (Max. Shear)
Principal Stress by Service Load Combinations (Max. Torsion)
Check Crack
At Factored Loads
Flexural Resistance
Shear Resistance
Torsion Resistance
Both non-composite box girder and composite girder are supported for design check as per CSA-S6-14.
Design Code
Display the design code selected for PSC Design.
Tendon Type
CSA-S6-14 code gives different stress limits for different types of prestressing tendons. Select the Tendon type provided in bridge from:
Low Relaxation Strand
Smooth High-strength Bar
Deformed High-strength Bar
Flexural Strength
Tensile stress of prestressing steel fps can be calculated by code or strain compatibility.
Code: Tensile stress fps is calculated by the equation as per the clause 8.8.4.2 of CSA-S6-14 for bonded and unbonded tendon respectively.
For bonded type tendon
For unbonded type tendon
Strain Compatibility: Tensile stress fps is calculated by the stress-strain relationship. (Refer to clause 8.8.3 of CSA-S6-14.)
Note
When flexure strength option is entered as Strain Compatibility and unbond type tendons are entered, tensile stress will be calculated by Code instead of Strain Compatibility method. It is because strain compatibility method is valid only for fully bonded tendons.
Reinforcing Rebar
In order to determine the crack width w, select reinforcing steel type from:
(Refer to the clause 8.12.3.2 of CSA-S6-14.)
Epoxy-coated Rebar: kb shall be taken as 1.2.
All Other Components: kb shall be taken as 1.0.
Environmental Exposure
Select the appropriate environmental exposure to determine the maximum crack width, w_max. (Refer to the clause 8.12.3.1 of CSA-S6-14.)
De-icing Chemicals; Spray or Surface Runoff Containing De-icing Chemicals; Marine Spray; Swamp; Marsh; Salt Water; Aggressive Backfill: Maximum crack width = 0.15 mm
Other Environmental Exposure: Maximum crack width = 0.20 mm
Construction type
For the segmental bridges, special provision as per the clause 8.22 of CSA-S6-14 is applied. Also in order to determine the tensile stress limits in prestressed concrete, Bridge type needs to be selected. (Refer to the clause 8.8.4.6 of CSA-S6-14.)
Segmental: Segmentally constructed bridges
Non-Segmental: Other than segmentally constructed bridges
Output Parameters
midas Civil produces PSC Design results for service limit state and strength limit state. User can select the parameters of interest for output display from the following list:
At Construction Stage/Service loads
Stress by Construction Stage
Stress by Service Load Combinations
Stress in Prestressing Tendons
Principal Stress by Construction Stage
Principal Stress by Service Load Combinations (Max. Shear)
Principal Stress by Service Load Combinations (Max. Torsion)
Check Crack
At Factored Loads
Flexural Resistance
Shear Resistance
Torsion Resistance
Design Code
Display the design code selected for PSC Design.
National
Annex
Select National Annex
The Following National Annex are incorporated in the program
a. Recommended
b. British
c. Italy
Design parameter
(Ultimate limit state)
Moment resistance
Consider tendons in tensile zone: For Moment of Resistance calculations, the tendons are to
be considered only in the Tensile Zone or all the tendons in the cross section.
Consider all tendons: Consideration of all the tendons will increase the resisting Moment and hence will
make the design less conservative.
Shear
resistance
Strut Angle for shear resistance: The Strut Angle will be used in the Shear Resistance calculation.
Prestressing steel type
Select the ratio of bond strength between bonded tendons and ribbed steel in concrete.
Cement
Class
Cement Class is used in calculation of compressive strength of Cement. We have to select one of Class R,Class N, And Class S.
User
Input
Modify design Parameters to be found in National Annex : Design Parameters according to the code are default set in the calculations. But the user has the option to edit them.
Beta (Interface Shear)
This option is activated only when PSC composite section is defined and assigned to beam elements. The β factor is the ratio of the longitudinal force in the new concrete area and the total longitudinal force either in the compression or tension zone, both calculated for the section considered. Refer to clause 6.2.5 of EN 1992-2.
Compression zone for the positive moment: 1.0 is always applied.
Tension zone for the negative moment: Select how to determine the β factor.
1.0 : 1.0 is applied.
Exact Design : The β factor is calculated as the ratio of the longitudinal force in the reinforcement and the total longitudinal force in the tension zone for the negative moment.
Design Code
Display the design code selected for PSC Design.
Design parameter
(Ultimate limit state)
Moment resistance
Consider tendons in tensile zone: For Moment of Resistance calculations, the tendons are to
be considered only in the Tensile Zone or all the tendons in the cross section.
Consider all tendons: Consideration of all the tendons will increase the resisting Moment and hence will
make the design less conservative.
Shear
resistance
Strut Angle for shear resistance: The Strut Angle will be used in the Shear Resistance calculation.
Prestressing steel type
Select the ratio of bond strength between bonded tendons and ribbed steel in concrete.
Cement
Class
Cement Class is used in calculation of compressive strength of Cement. We have to select one of Class R,Class N, And Class S.
User
Input Data
Modify design Parameters : Design Parameters according to the code are default set in the calculations. But the user has the option to edit them.
Design Code
Display the design code selected for PSC Design.
Input Parameters
Design parameter
(Ultimate limit states)
Moment resistance
Consider tendons in tensile zone: For Moment of Resistance calculations, the tendons are to
be considered only in the Tensile Zone or all the tendons in the cross section.
Consider all tendons: Consideration of all the tendons will increase the resisting Moment and hence will
make the design less conservative.
Prestressing steel type
Smooth bars and wires
Strands
Construction type
Segmental: Segmentally constructed bridges
Non-Segmental: Other than segmentally constructed bridges
Output Parameters
midas Civil produces PSC Design results for ultimate limit state and serviceability limit state. User can select the parameters of interest for output display from the following list:
Ultimate Limit States
Ultimate Bending Resistance
Shear Resistance
Torsional Resistance
Serviceability Limit States
Stress for Cross Section at a Construction Stage
Stress for Cross Section at Service Loads
Principal Stress at a Construction Stage
Principal Stress at Service Loads
Tensile Stress for Prestressing Steel
Crack Control
Design Code
Display the design code selected for PSC Design.
Note: Composite precast sections and non-composite post-tensioned box girder are supported for design.
Input parameters
Maximum Nominal Aggregate Size (8.2.4.2)
d_g: Maximum nominal aggregate size in mm.
Crack Control
Maximum Increment of Steel stress: Maximum increment of steel stress to control crack.
Output
Parameters
Check on items for which the design will be performed.
Ultimate Limit States
- Flexural resistance
- Shear resistance
- Torsional resistance
Serviceability Limit States
- Control of Cracking
Design Code
Display the design code selected for PSC Design.
Input Parameters
User Input Data
Partial Safety Factors for Materials (Ultimate Limit State)
Reinforcement and Prestressing Tendons: 1.15
Concrete: 1.5
Partial Safety Factors for Materials (Serviceability Limit State)
Triangular Compressive Stress Distribution: 1.25
Uniform Compressive Stress Distribution: 1.67
Pre-tensioned: 1.25
Post-tensioned: 1.55
Increase ultimate torsion shear stress, vtu for concrete grade above 40 (c6.3.5.2)
For concrete grades above 40 the values of vtu may be increased to 0.75 sqrt(fcu) but not more than 5.8 N/mm2. Check on this option to apply the increase of vtu. Otherwise, vtu will be determined according to Table 10.
Tensile Stress Limit in the Concrete at Transfer and during Construction
Pre-tensioned: 1.0 MPa
Post-tensioned: 1.0 MPa
c6.3.2.4 Cracking
b) At transfer and during construction. The flexural tensile stress in the concrete should not exceed the following values:
1) 1 N/mm2 due solely to prestress and co-existent dead and temporary loads during erection;
2) 0.45 sqrt(fci) for pre-tensioned members and 0.36 sqrt(fci) for post-tensioned members due to all other load combinations.
The above provision is not automatically applied in the PSC design function. Enter tensile stress limit which will be compared with the stresses occurring during construction.
Principal
Stress Limitation
Principal stress checks are not specifically required in the BS 5400 code. However, the user can specify the limit value if necessary.
Serviceability Limit State
Comp. / Tens.
Construction Stage
Comp. / Tens.
Output Parameters
The following checks are provided in excel format or table format
Serviceability
Limit State
Concrete stress limitation under service loads
Concrete stress limitation at construction stage
Principal stress under service loads
Principal stress at construction stage
Tensile stress for prestressing steel
Ultimate Limit State
Bending resistance
Shear resistance
Torsional resistance