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 LRFD17 Design CodeDisplay the design code selected for PSC Design. Tendon TypeAASHTO LRFD 8th Edition (2017) code gives different stress limits for different types of prestressing tendons (Refer to Table 5.9.2.21 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 ConditionIn order to determine the tensile stress limits in prestressed concrete at service limit state, select the corrosive condition from: (Refer to Table 5.9.2.3.2b1 of AASHTO LRFD 2012.) Severe Moderate/Mild Flexural StrengthTensile stress of prestressing steel fps can be calculated by code or strain compatibility. Code: Tensile stress fps is calculated by the equation as per AASHTOLRFD 2017 for bonded and unbonded tendon respectively.
Strain Compatibility: Tensile stress fps is calculated by the stressstrain 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 WidthSelect 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 typeFor 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 5.9.2.3.1b1 and 5.9.2.3.2b1 of AASHTO LRFD 2017.) Segmental: Segmentally constructed bridges NonSegmental: Other than segmentally constructed bridges Output Parametersmidas 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 LRFD12 Design CodeDisplay the design code selected for PSC Design. Tendon TypeAASHTO LRFD 6th Edition (2012) code gives different stress limits for different types of prestressing tendons (Refer to Table 5.9.31 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 ConditionIn order to determine the tensile stress limits in prestressed concrete, select the corrosive condition from: (Refer to Table 5.9.4.1.21 and 5.9.4.2.21 of AASHTO LRFD 2012.) Severe Moderate/Mild Flexural StrengthTensile stress of prestressing steel fps can be calculated by code or strain compatibility. Code: Tensile stress fps is calculated by the equation as per AASHTOLRFD 2012 for bonded and unbonded tendon respectively.
Strain Compatibility: Tensile stress fps is calculated by the stressstrain 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 WidthSelect 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 typeFor 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 5.9.4.1.21 and 5.9.4.2.21 of AASHTO LRFD 2012.) Segmental: Segmentally constructed bridges NonSegmental: Other than segmentally constructed bridges Output Parametersmidas 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 LRFD07 Design CodeDisplay the design code selected for PSC Design. Tendon TypeAASHTO LRFD07 code gives different stress limits for different types of prestressing tendons (Refer to Table 5.9.31 of AASHTO LRFD07 with 2008 interim, Customary U.S. Units). Select the Tendon type provided in bridge from: Low Relaxation Tendons Stress Relieved Tendons Prestressing Bars Corrosive ConditionSelect the corrosive condition from: Severe Moderate/Mild Flexural StrengthFlexural strength to be computed based on: Code: Clause 5.7.3.2 of AASHTO LRFD07 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 LRFD07) Bridge typeAs per AASHTO LRFD07,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 WidthSelect the appropriate exposure factor based on AASHTO LRFD07, 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 typeAs per AASHTO LRFD07, stress limits for fully/partially prestress concrete are different for segmentally and nonsegmentally constructed bridges. Select the construction type from: Segmental NonSegmental Output Parametersmidas 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
: Select all the output parameters : Unselect all the output parameters.
Design CodeDisplay the design code selected for PSC Design. Tendon TypeCSAS6S12010 code gives different stress limits for different types of prestressing tendons (Refer to Table 8.2 of CSAS6S12010.). Select the Tendon type provided in bridge from: Low Relaxation Strand Smooth Highstrength Bar Deformed Highstrength Bar Flexural StrengthTensile 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 CSAS6S12010 for bonded and unbonded tendon respectively.
Strain Compatibility: Tensile stress fps is calculated by the stressstrain relationship. (Refer to clause 8.8.3 of CSAS6S12010.)
fps = Epεp
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 RebarIn order to determine the crack width w, select reinforcing steel type from: (Refer to the clause 8.12.3.2 of CSAS6S12010.) Epoxycoated Rebar: kb shall be taken as 1.2. All Other Components: kb shall be taken as 1.0. Environmental ExposureSelect the appropriate environmental exposure to determine the maximum crack width, w_max. (Refer to the clause 8.12.3.1 of CSAS6S12010.) Deicing Chemicals; Spray or Surface Runoff Containing Deicing 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 typeFor the segmental bridges, special provision as per the clause 8.22 of CSAS6S12010 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 CSAS6S12010.) Segmental: Segmentally constructed bridges NonSegmental: Other than segmentally constructed bridges Output Parametersmidas 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 noncomposite box girder and composite girder are supported for design check as per CSAS614.Design CodeDisplay the design code selected for PSC Design. Tendon TypeCSAS614 code gives different stress limits for different types of prestressing tendons. Select the Tendon type provided in bridge from: Low Relaxation Strand Smooth Highstrength Bar Deformed Highstrength Bar Flexural StrengthTensile 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 CSAS614 for bonded and unbonded tendon respectively.
Strain Compatibility: Tensile stress fps is calculated by the stressstrain relationship. (Refer to clause 8.8.3 of CSAS614.) 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 RebarIn order to determine the crack width w, select reinforcing steel type from: (Refer to the clause 8.12.3.2 of CSAS614.) Epoxycoated Rebar: kb shall be taken as 1.2. All Other Components: kb shall be taken as 1.0. Environmental ExposureSelect the appropriate environmental exposure to determine the maximum crack width, w_max. (Refer to the clause 8.12.3.1 of CSAS614.) Deicing Chemicals; Spray or Surface Runoff Containing Deicing 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 typeFor the segmental bridges, special provision as per the clause 8.22 of CSAS614 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 CSAS614.) Segmental: Segmentally constructed bridges NonSegmental: Other than segmentally constructed bridges Output Parametersmidas 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 19922.
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 typeSegmental: Segmentally constructed bridges NonSegmental: Other than segmentally constructed bridges Output Parametersmidas 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 noncomposite posttensioned 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.
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 Pretensioned: 1.25 Posttensioned: 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 Pretensioned: 1.0 MPa Posttensioned: 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 coexistent dead and temporary loads during erection; 2) 0.45 sqrt(fci) for pretensioned members and 0.36 sqrt(fci) for posttensioned 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.
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

