midas Civil webinar: PSC Box Girder Bridge Design as per AASHTO LRFD12

and then we will see some of the PSC design features in the program after that I will be discussing about some features that help the bridge engineers so let’s start so Midas civil is a 3d FIM software for bridges and civil structures so as you can see on your screens that Midas civil is capable of handling all types of pieces you can handle the suspension bridges the conventional bridges the integral bridges using the program also Midas civil is capable of performing all kind of analysis varying from the simple static analysis to advanced analysis such as the construction stage analysis the dynamic nonlinear analysis and so on so in the coming slides we will be talking about the capacities and the major functionalities of the program first of all let’s see a project application of my bur civil so here we have the model for basarab overpass this is located in Romania and it is one of the widest bridges in the Europe the bridge is around 46 meter wide at its widest section and the beach is around one and a half kilometers long the bridge is constructed using the free cantilever method also Romania is a highly seismic zone so the program was also used for performing nonlinear dynamic analysis with laid rubber bearings and viscous dampers now let’s discuss regarding the modeling philosophy as well as the features so whenever we need to design a we need to first idealize the structure of the bridge let’s say we have a structure like this so we need to idealize the structure now for the idealization of the structure we have various options available we can idealize the beam as a line beam model or a grillage model or a full finite element model let’s discuss some pros and cons of all these three models so first we have the line beam model for narrow pages we can obtain accurate results in a quick way using the line beam model but as the width of the bridge starts increasing the line model fails to give the transverse distribution of the loads and the bearing reactions cannot be obtained accurately using this model so for those cases we have to switch to the grillage model in the greenish model we idealize the bridge leg through village of interconnected beans so in the village model we can get the accurate load distribution as well as the accurate bearing reactions and then we have the full finite element model using the full finite element model we get a more realistic structural response and we can group and it represents the local as well as the global responses more accurately today I will be using the line beam model for the demonstration purpose now let’s see some of the modeling features in the program so the program offers the general modeling procedure also for the bridges which are constructed through typical construction processes the program offers various modeling results so the program offers you a wizard for incremental or teaching method which also the program offers you wizard for the bridge which is being constructed through free cantilever method and full showing method then we have the various other wizards like for the suspension which for the cable-stayed bridge then we have the grillage wizard which helps you in creating the grillage model and then the transfer section wizard will be discussing about these in the coming slides so first we have the Freak cantilever method bridge wizard so here you can see that once you input the information regarding the model

regarding this section and they tell them then the program will automatically model the bridge for you and the program can also simulate the construction stages for you let’s see how we can use the bridge wizards in my disable so for this purpose I’ll open a new model file I won’t have any predefined material or section information I am starting from a fresh file so here in the structure tab we have the FCM bridge wizard here I will open a file containing the values for these parameters so now I need the material information for the girders as well as the piers for that the software has the database of the materials also the program supports the import of the materials from the previously completed projects so here I have three materials in my previous model file so I will import those materials and then I need some section for the pier for that the program also supports the import from the previously defined project so I can make a selection that what sections I want to import and what section that do not want import so here I have the information for the sections this information was for the section for the pier and now for the section for the bridge so here I have some predefined shapes so I enter the values of these parameters for height and the width and the section will also be created and then finally the tendon information so I need to input the information like the jacking stress and the location of the tendons and then I need a tendon property I need to define my tendons so I’m defining a tendon property so all is done now as soon as I will click OK the program will start modeling a so here we have the bridge with us so here we can see that in the works tree we have the information with us the program created the static load cases and the tendon profiles and then also the construction stages so here we can see that in the first construction stage we have the piers and the deck above the piers as soon as the construction staging stages are going ahead the is being installed and as we move to the last construction stage the installation of the complete has taken place so using the bridge results it is very easy to model the bridges now after free cantilever method which wizard the program also supports the full showing method which wizard so similarly here we can enter the information regarding the model the section and the tendon and the bridge will be modeled by the program now for PSE sections we can have the ensel sections paci sections and PACP sections these sections are auto defined in the program so you can enter the values of height as well as width and then you can model these sections also for data base the program supports the section data base as per our stock codes as per Caltrans codes and the ically as well as UK codes show you so you can just select

the section from these data bases and use the section then if you want to have a user-defined shape then you can import a DXF file using section property calculator and you can create any user-defined shape in section property calculator and general section designer and then use the shape in my disable for the bridge analysis as well as design now in the bridges when it comes to tapered section groups engineers feel it very convenient to use so what do you do when you have to use the tapered section you have to calculate the section properties at all the intermediate sections so if you want a tapered section like this so you will create you will need to calculate the section properties at this section at this section at this section and similarly at all the other sections now using the midas civil one can create the tapered sections very conveniently so the program omits the need for calculating the section properties at all the intermediate sections so the engineer needs to provide the information regarding the section property at the end of the first element at at the JNA of the last element and then you can assign the tapered section group to all these elements and then you will see that the section properties at the intermediate sections are automatically calculated by the program then for the use of the pse sections the program also supports the pse bridge research so if you are using the PSE bridge wizard then you need to enter the information regarding the depth of the section varying with the longitudinal direction of the witch so you enter the distance of the longitudinal direction and depth at that section in this way you can create the tapered section using the PSE bridge wizard you can vary not only the depth of the section but you can also vary the width of the section the web thickness as well as the flange thickness now let’s see some of the modeling features in the program so here I have a model file here I have defined some materials for the concrete as well as for the tendons and then I have also defined the time-dependent material properties for creep and shrinkage so for the creep and shrinkage I have selected the ash to code and then we need to enter some required parameters like relative humidity and age of concrete at the beginning of shrinkage and then we need the volume surface ratio for each element the program supports the auto calculation of this volume surface ratio for all the elements so we have the results for the creep coefficient and the shrinkage strain then I have a predefined attendant property now let’s see how we can use some general modeling features of my disable so apart from the Wizards for the business the program offers a very user-friendly general modeling so here I have a so I’ll use the bean wizard so I need to enter the information regarding these plans so as soon as I enter this information after that I’ll need to select the material as well as

the section so as soon as I entered the information I have the bridge model with me now I need to connect the supports to the bridge deck so for that I’ll be using the elastic links so now I need to create the elastic links at the four locations so I can simply create the elastic links at one location and the program can copy those elastic links to the other locations so I created one elastic link and three are automatically created similarly for this position now we need to have tendons for the deck let’s see that how the program offers the tendon input information so the program offers the manual definition of the tendon profile for the manual definition the program has the various reference axis for the tendon definition you can use this straight reference axis we can also have the curved reference axis and we can also input the coordinates of the tendon with reference to the centerline of the element also the program supports import and export of tendon profiles with the DXF format so we’ll see that how we can import and export tendons from the DXF format so for that we need to go to tools and tendon profile generator here I locate my DXF file and then I need to enter information regarding the material property and the elements where I want my tendon and then which profile is for exit plane and which profile is for XY plane and finally we’re dependent should be inserted and similarly for the second tendon so as we will enter this information the program will generate a text file for us so we can copy the information of this text file in the MCT command shell and click on run so we have the tendon profiles with us so here the program created the tendons as they were defined in the DXF file now if I have to manually copy these tendons then that is also very convenient in the loads and the temperature and P stress loads we have the tendon profile so we can select the tendon profile that you want to copy and then the location where we want to copy the tendon profile so now we copy two tendon profiles and in total we have the four tendon profiles now let’s see the application of the loads for this structure for the application of flows we need to have some static load cases I have some predefined static load cases so first of all the cell rate for the structure for defining the cell bit of the structure

and 36 at the J node of sixteenth element we have the support and at the island of the seventeenth element we have the node similarly for element number 35 and 36 the J and at the I N and finally for the element number 52 we have the support at the J end so we have this pan information and then in the PSE bridge we have the effect of it so we can select the effective width to be calculated as per the ASCO recommendations and then we can have the results for the effective width scale factor as well as the effective width so we have a text report for this and also the results can be obtained in a tabular format so after this our modeling part is completed let’s see how we can control the analysis in the program so some of the features of analysis control so when we have the elastic shortening then the tendon tension loss will be affected I mean to say when there is the elastic deformation due to live loads then there will be the elastic when there will be elastic deformations due to live loads then the tendon tension will be affected so the tendon tension loss will change with the elastic deformations so if we want to consider that change we can op using the analysis control if you want to ignore that effect that can also be done usually for preliminary analysis we ignore that effect and finally for the full detailed analysis we consider this effect also due to the creep and shrinkage the tendon tension loss will be affected so in order to consider that we can check this option and the program will take into account the change in the tendon tension due to the creep and shrinkage and then we can control the stress over the transfer length in a post tension model so in order to use this we need to define the transfer length in the tendon profile so we can choose that we want to have a constant stress in the transfer length or we want the stress to be varying linearly here we see the we have a tendon and a member and near the Anchorage’s the concrete will crack and due to this this stress in the tendon will be reduced and we can consider this effect and then we can also consider the presence of tendons for calculating the section properties for calculation of the section properties the program can consider the presence of the tendons in case of post tension we can use the next section with the duct areas excluded before the grouting and then we can use the transformed section with the duct areas included after the grouting now let’s see some the result features so for results as we have the construction stages with us so the first construction stage the

second construction stage the third construction stage so as soon as we compose a construction stage the program creates the program creates the load cases for tendon prime v10 done secondary creep primary creep secondary shrinkage prime B and shrinkage secondary so we can view the beam diagrams for these load cases so let’s see the beam diagrams so here we have the beam diagram in the fourth construction stage for the dead load similarly we can have for the tendon primary and tendon secondary also we can choose to have the current step forces so we can see the forces produced in this construction stage only then the results are also available in the tabular forms also with the results of the construction stages the program provides the envelop of the construction stages as well so for the envelopes we can choose the min/max so here we have the results in the tabular forms all these tables are compatible with Microsoft Excel we need to select export to excel and you can have all the results in an excel sheet then for the result of tendons we can have the tendon losses so here the program will calculate the stress after immediate loss and the loss in stress due to elastic deformation and the ratio of the both and then the loss due to creep and shrinkage the relaxation loss and finally de-stress after all the losses so we can choose the construction stage and the tendon and then we can view the results also this results are available in the form of forces then we can also have the tendon loss graph so for tendon loss graph we need to select the construction stage and the tendon and we can get the tendon force varying with the distance also we can export this graph as image or as text then we also have the camber results with us we’ll discuss about the camber results in the coming slides now for the results of the moving load the program offers a moving load tracer so in the post construction stage we can view the results from the moving low tracer so here we can select that for this element we want which component to be maximized at which part so here we see that we have the results for the moving load tracer so the program displays the location of the vehicle for that specific situation and also we get the maximum value so we have the results with us then we can also view the results for the moving load pressure in the beam diagrams in

we select code the stress in the tendons will be calculated using the equations provided in the code so the code provides equations for all the situations for both bonded as well as unbonded tendons but when it comes to strain compatibility we can use the strain compatibility for the bonded tendons the strain compatibility is not applicable to the unbonded tendons so if we have the unbonded tendons and we select the strain compatibility then the program will automatically calculate the flexural the stress in the tendons as per the codal provisions and then we can specify the construction type to be segmental or non segmental in case the construction type is segmental then the Bravo design forces will be at the joints and not at the sections and then we can select the design positions so if we have a very large model then we can choose very few positions to be defined to be designed for moment as well as sheer but here I have selected all the positions for the pse design for both moment as well as here and then we can choose the output positions so we can select that at what positions we require the design report so once I am done with all these information we can start performing the design so as for the results of the design we’ll be getting all the tables for the limit state checks also we will be getting the Excel report at the specified output locations and then we’ll also have the PSA result diagram which is a very useful tool so in the message window we have the information that the PSA design is completed now let’s see the limit state checks for both ultimate limit state as well as the serviceability limit States so first of all we will see the serviceability limit States now when we have the time varying compressive strength then the allowable load changes with the compressive strength so for every construction stage for a particular section we will be having the different allowable strength so for that we need to ensure the safety of the structure so here we have the results with us so how the program ensures the safety of the structure is that the program calculates the ratio of the required stress and allowable stress at all the construction stages for all the sections then whichever ratio is the highest the program chooses that stress to be compared with the allowable stress so the program calculates the stress at the top fiber the center top at the bottom top at the center bottom at the top left at the bottom left at the top right and at the bottom right so whichever stress comes out to be maximum that is compared with the allowable stress and then we have the check for the tensile stress in

the tendons so here the program calculates the stress in the tendons so FD l1 is this stress in the tendon at encourages ft L 2 is the maximum stress in the tendon along the length away from the encourages and SL L 1 is the stress in the tendon after all the losses at the last stage and then the program also has the allowable stresses for these so we have the comparison between the allowable stress and the actual stress and then third is the check stress for the cross-section at the service loads so here the program calculates distress using the service loads so the program calculates the stress for the center top center bottom top left bottom left top right bottom right positions and then compares the maximum stress with the allowable stress and then we have the principal stresses at the construction stage so the program calculates the stresses at the ten specified locations so and then compares the maximum stress with the allowable stress similarly stress for service loads excluding the torsion shear stress and then also the combined shear stress the principle stress and then we have the check for the crack width at the service loads let’s see how the check for the crack width is applied so here the program compares the spacing of the rivers and the maximum allowed spacing of the rebars so we have the results for the combined stress due to bending moment about the major axis and the axial force at the top fiber and similarly we have the results for combined stress due to bending about major axis and the axial force at the bottom fiber and then these are the tensile stresses in the reinforcement and then the spacing we specified for the reinforcement and the maximum allowed spacing also I would like to mention that for the PSC sections the program offers the beam stresses here we can specify the position as well as the component to be displayed and then we can get distressed diagrams I should have mentioned it earlier when we were discussing about results but a forward and I’m sorry for that so here we have the beam stresses so we can select the ten specified output locations and then we can have the stress diagrams now for the design force we can have the tabular results so for all the elements we can have the design forces so here we have the results so for element and the load combinations we have all the results with us in the tabular form and

now we can see the PSC result diagrams this is a very useful tool for the PSA design the tool offers to check the ultimate force and the criteria force at once so here in the diagram the green line mentions that this is the allowable force but the ultimate force is less than that the actual force is less than the allowable so we can very quickly verify that our forces are appropriate or not and then we can also have the results in the form of the safety factor so this is the criteria line for a factor of safety of 0.6 and then finally we can have the Excel report of the design so for the generation of the Excel report we can use the units to be standard units or the US units the Excel report will be generated for the element that is specified in the output position I have a pre generated Excel report with me so in the Excel report the program provides all the tables for the ultimate limit state as well as the serviceability limit states all the text for the serviceability limit states are in separate sheets so first we have this stress at the construction stages and then for the stress check for the serviceability load combinations and then the principal stresses so these are all the serviceability limit States and for the ultimate limit state we have the detailed design report so in the design report first we have the information results regarding the design code then the section properties then the material properties then the prestressing steel and we have the sectional forces due to effective prestress and then we have the flexural design for the section so we have the axial force in concrete and the axial force in the reinforcement steel for both tensile as well as the compressive zone and then the axial force in the tendons and the calculation of the flexural resistance so whenever there is a calculation for the flexural resistance the program will also mention the specification number in the code so you can manually verify the results and the manual verification is very easy then you have when you know that from where what thing is coming so for that the we have provided the specification numbers in the report as well and then the shear design so we can have the shear design the calculation of the effective depth the maximum spacing of the transverse reinforcement so with every check we have this specification number mentioned so it is a very detailed report and then the torsion design for the section and then the crack check so we have the reports for all the output location specified at I node of the sixteenth element at the J node of the sixteenth element and similarly we have all the results with us also you can perform the peer design using the program for the

peer design you can get the PM interaction curves and you can also get a very detailed report for the peer design and the graphic report now let’s see some of the other features in the program that assists the bridge engineers so first is the visit for the transverse analysis so here what you can do is that you can specify a element for generating the transverse analysis model and input the information regarding the load in the reinforcement and then input the definition regarding the load parameter then the program will generate a model for the transverse analysis of the section then if you want the full 3d modeling then you can use Midas fel so Midas civil can communicate with the Midas Fe a and the geometry and Midas civil can be exported as the solid in F here so in this way the geometry is automatically generated and then the grillage model desert so the grillage wizard automatically generates the drainage model it also generates the longitudal members and also you can specify the location of the transverse members and then the FCM camber so the Campbell is very important for election engineers whenever we are installing the bridge at the site then sometimes we face the problem that the last segment is not fitting so in order to take care of that problem the program calculates the FCM camber so the program can provide you with the camber control graph and you can take care of the camber by installing the bridge so let’s see the camber results and the results we have the camber so we’ll get the construction camber so the program supports the calculation of the Campbell as well this was all regarding the today’s webinar if you are having any questions then please feel free to ask in the questions window so we have some questions with us so the first question is that how we can extract the pitch deflections for the

each construction stage so I’ll demonstrate this so for the extraction of the bridge deflections we need to go to the particular construction stage and then select the deformed shape so here we can select the load combination for gate we want the deflections can have the deformations also this information is available in the form of tables so we can select the appropriate load case and then we can check the deformation results for the various construction stages also we can get enveloped for all the construction stages so this is in the tabular form I hope this clarifies that how we can extract the deformation results for the construction stages you you you so then we have the next question that if it is possible to transfer sections from the longitudinal analysis to the transverse model so when you will be using the transverse section wizard then the section created will be a line section but if you want to have the modeling of the transverse section in using the solid plates then you can use Midas fel so here from export options you can export the frame section for model for solid and then you can use the geometry generated in Midas Fe you then we have a question that regarding the camber control so a demonstrated the camber control in the webinar so in order to take care of the camber you need to manually adjust the location of the nodes you you

so next question we have that what is the use of the option the real displacement so if we uncheck this option then the program applies a scale factor for the deformation so that we can clearly see the deformations but if we check this option then the program will provide us with the real displacement in the bridge you also the program offers to see the stage step real displacements you you so next question we have is that if we can perform the PS if we can reflect the effect of camber in the PSC composite design you you you so next question is regarding the design of PSE composite so at the moment the program doesn’t supports the PSE composite design as per our stock code but the PSE composite design is supported as per the euro code and as per ushe two codes the program will be able to design the steel I composite sections in the next release the next release will be in June 2014 you you

so next question we have is regarding the second the displacement due to the secondary effects of creep and shrinkage so so you so for deformations we have the creep primary and shrinkage primary results with us but the creeps secondly and this the shrinkage second will results are not required for design so that’s why the program doesn’t support those results you you so next question we have is that can we use PSC to model the cable-stayed bridges so the software supports the use of PSC for the cable-stayed bridges the next question is regarding the stage step real displacements so I will like to use a picture for this for the explaining this so here we can see that in the different stages we have the deformations in this structure so the real displacement in the construction stage 3 at the point 3 will be the summation of the deformations in the first two stages so using the real displacement option checked on we get these displacements so this option is activated after we check on the option in the construction stage analysis

control here we need to check this option on for having the stage real displacements you you so the next question is regarding the friction losses in tendons so in the tendon property when we specify the tendon property we can specify the factors for the curvature friction as well as the wobble friction so using these factors the program calculates the friction losses you you you you you you you you you you you you you you you you you questions please feel free to write the questions in the questions window you so we think there are no more questions so thank you all for attending today’s webinar so if you have any questions in the further please feel free to write @y j k IM at midas IT calm i will spell the email why j k IM at the rate mid-80s you

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