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# Bridge Engineering - Science topic

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Questions related to Bridge Engineering
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While estimating the contraction and local scour, there are many equations in the literature mostly produced by using prismatic channels (e.g. rectangular). However, in real case studies, we are modelling the rivers with their irregular cross-sections and for scour analysis, the approach channel depth or flow depth at just upstream of the bridge could be "Maximum flow depth", "Local flow depth" at the upstream face of pier, and "Average flow depth".
The question is which approach should be used for contraction and local scour?
For contraction scour the answer is most probably the "Average flow depth".
What about the scour around piers?
The depends on the depth of erosion you want to define. The assumed flow depth is the local depth immediately ahead of the supports or abutments.
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i have vibration data of bridge and process the data with different possible techniques such as FFT, Wavelet decomposition, Empirical mode decomposition, Hilbert Transform, Frequency domain decomposition, spectrograms, etc. but still i am not able to locate exact or pin point frequency of the bridge structure. in the following techniques the results are in a specific range of frequency such as 2.6 to 3.1 Hz. The data showing this specific range and not providing the exact frequency. because in this range any number can be the natural frequency of the bridge structure. so the actual frequency lies in this specific range but i want to go further in depth to figure out the exact value of the frequency in Hz. but the problem is i am not able to find any technique that will give me answer of my curiosity. i recorded data from accelerometers considering normal traffic conditions. there is not closure of bridge. vehicles are passing normal situation.if anyone have any clue about it or still my question is not clear so i can explain further
i attached some of my results
i will be very grateful to anyone who let me find my answer
thanks
Dear Ali,
the maximum response recorded by your accelerometers is mathematically the CONVOLUTION of the structural response of the bridge (with a peak expected at each natural frequency) and the excitation by the trucks (with a peak at their own suspension frequency) meaning the frequency of the maximum response is a mix of both! Of course the truck's primary suspension frequencies vary from a truck to the next, still in the same range.
In addition the natural frequency of the bridge is load dependant (weight and position of the heavy trucks at the time of the record), and temperature-dependant (meaning day/night, clear day/cloudy and seasonal fluctuations...)
Back to your precise question, you have just NO WAY to determine the exact bridge natural frequencies by this "natural response" method. As suggested, you must close the bridge (however with the same added load than the usual traffic) and use for example a dropped weight to generate a broadband shock (preferably located in consideration of the anticipated mode shape, which allows you to trigger distinctively the first flexural/torsional modes). And still the exact frequency will vary with the previously mentioned load and temperature conditions... Sorry for you, that's just the complexity of structural vibration physics!
Back to Vahid's remark, we could only appreciate the likely natural frequency range of your bridge by knowing its precise construction and span, but the natural frequency of very long bridge spans can even be below 1Hz (remember the ill-fated Tacoma bridge, destroyed by wind gusts at approx. 0.5Hz resonance https://www.youtube.com/watch?v=j-zczJXSxnw). Obviously short bridges have higher natural frequencies but you can interpret it as revealing over-designed structures! The Tacoma bridge example is also a good evidence of the 3D complexity of the mode shapes (something also well evidenced by Eric's study, which provide a very accurate in-situ modal analysis). My guess is that in your case the 2.6 to 3.1 band correspond effectively to the interaction of the trucks suspensions with one of the main natural frequencies of this bridge... in this global 2.8 +/- 0.3Hz band! But don't ask for more precision...
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Hi All,
l am modeling a composite slab on girder bridge on ANSYS APDL following the shown procedure.
I connected the shell element slab to the beam by using MPC184 rigid links.
All of my elements have 6 degrees of freedoms (compatible) and it's a linear static analysis.
I am applying a lateral force in the Z direction along the bridge parapet/railing.
Self weight / gravity is not added.
The nodes from all elements match and the meshing seems fine.
Its a simply supported bridge (roller on one side and hinge on the other)
The deformed shape of the bridge under lateral loading looks okay. But the reaction forces do not make sense. I change the location of the force laterally and the reaction forces do not change.
I glued the areas/lines before meshing.
What could possibly be wrong? I see it as a connectivity error but am not sure where I went wrong
Zeinah Mohamad Elnassar, No, when you reduce the mesh, firstly, you can get the result faster, if there is a wrong you can repeat it without losing much time. Secondly, if you get a big difference in the results compared with the finer mesh, then the insensible results are caused by the mesh.
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What is the shell orientation mean in ANSYS APDL?
Does it mean that if I have a shell on the XZ plane then I set the orientation as 0 degrees as shown in the pictorial view
and if I have a shell on the XY plane then I set the orientation as 90 degrees?
Or does it mean something else? Like the direction of the fibers in the material?
Exactly, when using isotropic materials you can observe that the results won't change no matter the value of the orientation angle.
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I am modeling a bridge on ANSYS APDL using shell and beam elements. The beams and slab are connected using MPC184 (constrained element).
After I am done modeling and meshing I merge nodes with 0.001 tolerance yet I still get an error saying meshing will produce errors. even when i tried to merge all I still get a warning / error message
After Nummrg,all / Nummrg,NODE .... future commands which depend on the node to solid model connectivity (meshing, mesh, clearing, solid boundary condition transfer, etc.) may not operate properly.
My results are wrong. Is there a step that I messed?
It is a “warning”, not an “error” message, so it only warns the user to pay attention because something is happening in the analysis. As far as understand, the message simply tells you that a node, which before merging belonged to only one CAD entity, after merging is shared by more than one geometrical entity – which is exactly the purpose of merge command. This was also explained very well by Naveen Bhatt.
I think that if areas are glued before meshing, nodes will be shared automatically at common boundaries. Anyway, besides this point, I have two comments:
- Why to connect shell/beams with MPC184 (constrained element)? Have you tried simply to connect them at a node? They should be compatible (i.e. same degrees of freedom);
- Why to use such small elements for the slabs? Normally, small elements should be only be used in regions where high stress variations are expected, otherwise they will increase the computational cost unnecessarily;
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I am not sure whether to use boolean A glue command to glue the areas / lines of my model together.
OR
just use merging nodes NUMMRG, node command
My model is a static linear bridge element where the slab and railings are shell elements, the beam flanges are beam elements and the beam web is a shell element.
Beam and shell elements are connected using MPC184 rigid links.
Glue Command
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Hello!
I am analysing a cable stayed bridge seismic behaviour in Ansys Mechanical APDL, but I have got some problem unfortunately. I wolud like to run multiplie loadsteps in one work session. In every load step I want to prestress a pair of cables so that the other ones are stay prestress free. Every cable in the structure made of LINK 180 element. Here is the snipet of my code where I defining the loads and loadsteps and try to solve them.
!MEGTAMASZTASOK
!///////////////////////////
ALLSEL,ALL,ALL
NSEL,S,LOC,Y,15
NSEL,A,LOC,Y,-15
NSEL,R,LOC,X,0 !MEGTAMASZTAS
D,ALL,UZ,,,0
ALLSEL,ALL,ALL
NSEL,S,LOC,X,0
NSEL,R,LOC,Y,0 !SZELSARU
D,ALL,UZ,,,0,UY
ALLSEL,ALL,ALL
NSEL,S,LOC,X,144
NSEL,R,LOC,Z,-11.285
NSEL,R,LOC,Y,-23.463,23.463 !TELJES MEGTAMASZTAS PILON ALJ
D,ALL,ALL,,,0
ALLSEL,ALL,ALL
NSEL,S,LOC,X,444
NSEL,R,LOC,Z,-11.285
NSEL,R,LOC,Y,-23.463,23.463 !TELJES MEGTAMASZTAS PILON ALJ
D,ALL,ALL,,,0
ALLSEL,ALL,ALL
NSEL,S,LOC,Y,15
NSEL,A,LOC,Y,-15
NSEL,R,LOC,X,588 !MEGTAMASZTAS
D,ALL,UZ,,,0
ALLSEL,ALL,ALL
NSEL,S,LOC,X,588
NSEL,R,LOC,Y,0 !SZELSARU
D,ALL,UZ,,,0,UY
ALLSEL,ALL,ALL
NSEL,S,,,6168,6173,5 !LEKOTES
F,ALL,FZ,-4000*1000
ALLSEL,ALL,ALL
NSEL,S,,,6188,6213,25 !LEKOTES
F,ALL,FZ,-4000*1000
!TERHEK
!///////////////////////////
ACEL,,,9.81 !GRAVITACIO
!KABEL FESZITES
!///////////////////////////
*DO,I,1,2,1
ESEL,S,TYPE,,3
INISTATE,DELETE
ESEL,S,,,3733+2*I,3734+2*I,1,1 !KABEL ELEMEK
INISTATE,SET,CSYS,-2 !LOKALIS KOORDINATRENDSZER
INISTATE,SET,DTYP,STRE !FESZULTSEG
INISTATE,DEFINE,,,,,1000000000 !FESZITESI ERTEK
LSWRITE,I
*ENDDO
FINISH
!MEGOLDAS
!///////////////////////////
/SOLU
ALLSEL
ANTYPE,0 !ANALIZIS FAJTA
PSTRESS,ON
OUTRES,ALL,ALL !FESZITES BEAKCSOLASA
LSSOLVE,1,2,1
FINISH
Ansys solves the problem, but got an error wich says:
*** ERROR *** CP = 626.422 TIME= 17:49:37
LSSOLVE looping is stopped because of a solution error.
In post procesing I have some sort of result, but it has only one load step, and gives a rigidy body displacement (I added the picture as a file).
Do you have any ide what did I mess up? If I prsetess only one pair of cable, and ask Ansys for solution, it perfectly works withou any errors.
My other problem is about elemnt table results. I would like to write out the element table result into a text file, but I don't have any idea how could I extract the results with scripts.
Rafael
It is a reflection of the constraints. Can you send me the file of the model to check out?
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I mean simply a structural analysis of different bridges.
Thanks
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For modeling bridge deck slab on ANSYS APDL, why is shell element preferred over solid element?
I read somewhere that the mesh of shell elements is more efficient than solid elements. Why is that?
Solid elements model a complete system of partial differential equations. As a result, you find the entire stress and strain tensor. This requires a long computation time and does not always give the required accuracy.
Shell elements reduce the dimension of the problem and take into account only principal stresses. Therefore, the task is considered faster and the counting accuracy will be higher.
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For the bridge shown below, the web is connected to both flanges, and the slab is connected to the parapet by meshing and merging the nodes, but what is the name of this connection?
is it semi-rigid? rigid? pinned? fixed?
Can i say the parapet-slab connection is rigid?
In general, what is the connection between elements on ANSYS when we merge them together?
Yes, it is similar to bonded contact and it can be considered as rigid joint.
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I modeled a bridge on ANSYS APDL and added cross bracings / diaphragms as shown below. The diaphragms are not straight along the x or y or z direction, they are inclides BEAM188 elements.
how can I get the axial stress for inclined Beam188 elements?
by using an Element Table, see Ansys Help
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I want to automate all by bridge modelling not directly using the program interface rather using a scripting language like matlab,vba,.net etc.
Sap2000 provides OAPI  but I could not find options for substructure design in the software using OAPI  and CSI bridge seem to not giving any OAPI.
So I want to know which is the best FEM software available which gives scripting or api interface to model my bridge(both superstructure and substructure)
I suggest to adopt more a graphical language for parametric modelling. Take a look to Rhino + Grasshopper used in combination with Sofistik as solver. You can combine solver with parametric input obtaining the response in real time.
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Which feature of Fluent 14 is able to simulate pier scouring?
difficult for cohesive bed
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Dear colleagues
I have faced to a problem in extracting contact force of rail-wheel in transition zone which have been modeled in ABAQUS. there are many kind of contacts there, but I'm not sure which one suites my problem in transition zones. I was wondering if you can help me to find out this subject.
by the way I enabled CF(contact force) of Field Output but there is no CF in my .odb files which are my results.
many thanks for your kind consideration.
best regards,
Saeed Sotoudeh
Reliable movement and path will be provided by wheel and rail contact, and this would be dependent on several factors.
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The reinforced concrete plane frame with lumped plasticity approach is developed in OpenSees using Joint2D element for panel zone and elastic elements for beam and columns. When I model four springs with Modified Ibarra-Medina-Krawinkler Deterioration Model with Bilinear Hysteretic Response (Bilin Material) for four springs and elastic spring for shear spring at the center of the beam-column joint, I got unexpected results using this bilinear model. It means that I am using inappropriate material model or something is missing to include nonlinearities in beam column elements.
Please suggest me which material model should be used for four spring considered in Joint2D element (Arash Altoontash, 2004). In addition, advice me how to model shear panel in RC beam column joint by any other options to get reasonable results.
If your code failing in Gravity analysis itself then I suggest checking the Eigenvalues before doing analysis, If your eigenvalues are reasonable then you can proceed to change the analysis parameters, I neither used Penalty constraint handler nor Joint2D, but I can say that selection of alphaM and alphaS matters a lot.
The below note is from the OpenSees website :
The degree to which the constraints are enforced is dependent on the penalty values chosen. Problems can arise if these values are too small (constraint not enforced strongly enough) or too large (problems associated with conditioning of the system of equations).
You can check the OpenSees User forum.
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BRIDGE ENGINEER
M.E/TECH IN STRUCTURAL ENGINEERING
ABOVE 7 YEARS OF EXPERIENCE
Please sent the requirements. I am interested in this su ject. Thanks.
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I am performing non-linear analysis on a bridge deck modeled as a layered shell element. The bridge deck is supported by four concrete girders which are modeled using section designer in SAP2000.
I am applying the load in steps in order to measure the deflection on in the model for the loads.
Hi,
Many of these convergence problems are because of instabilities.
1. Do a modal analysis and check the first mode shape and period.
3. Reduce your step size and see if it improves the analysis.
4. Change the boundary conditions and increase the indeterminacy. (e.g. change hinge supports to fix supports, reduce hinges in model) and check if the convergence is obtained and then find the source of the issue and then consider something between hinge and fix for such zone using springs,...
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Hello,
presently we are joining big (example 5 meter X 5 meter) laminates using bolts or some other aiding material etc etc. My question is how to join these big panels with zero radius. and if it is there what is the price?? Thank you in advance. Material is glass reinforced polyester laminates.
I agree with A S Kaddour .
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I'm working on the RCC bracing concept to reduce the displacement. using push over analysis through  Etabs V13. Do the bracing required to be assigned with hinge, if yes which book could I refer?
Depends on actual situation of connections in your frame modelling. If they have fixed supports, no need for applying hinge at the the phases before post-elastic phases and after performing plastic hinges you may model the connections as plastic hinges, but if you have designed the joints with simple connections you may consider normal hinges in safe side.
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What are the methods for internal damage detection of structures?
Take a look at NDE web manual designed by FHWA
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Hello everyone!
I just enrolled for a phd and need to determine what my research and thesis will be about. From the start I considered concrete bridges for research. There is an incredible opportunity in my vicinity where two concrete girder slab bridges will be built. Both bridges have two roughly 25m spans, but one bridge is an integral reinforced concrete construction, while the other one is a prestressed concrete construction with bearings on the abutments. This seems like a perfect opportunity to set up a thesis, put some monitoring instruments on the bridges and in a year or two draw a conclusion and see differences in reinforced concrete bridge and prestressed concrete bridge. Whatever the thesis is about the plan was to also do a numerical model of the bridges and see their behaviour using probably SOFiSTiK.
All of this is fairly overwhelming so I would like to ask all of you for help. I already looked up some dissertations but cannot decide what would be good to do here. I am open to all suggestions (creep, shrinkage, cracks, earthquake, etc.) with little guidance.
Thank you all very much for your time!
Having access to instrument two bridges of same span but different in support condition (integral and simply supported) is a great opportunity. Integral bridge construction is the preferred option of Highways Agency in the UK for newly constructed short to medium span bridges when strong ground condition and low skew is present. However, integral bridges rely on their flexibility when taking on short and long term deformations due to temperature, shrinkage, creep and support settlements. These deformations and the secondary bending effects created are not fully understood, especially with long term field testing. If the integral abutment is a frame abutment rather than a flexible support abutment with sleeves around the top part of the abutment piles, you will also see complex soil structure interactions such as ratcheting of soil behind the abutment. On the other hand, you have a straightforward simply supported bridge with bearings which you can use as a reference for comparison.
You can Instrument both of these bridges with temperature gauges, inclinometers, strain gauges and if possible with fibre optic cables. You can also use traditional surveying intermittently to validate the deformations provided by the instrumentation. Creating an initial numerical model to estimate the expected behavior of the bridge will help you when deciding the required accuracy of the sensors and the sensor arrangement. Finally you can update the numerical model with the field measurements and potentially draw conclusions on the complex behavior of integral bridges.
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I am trying to model the foundation of a bridge that has damage to the junction of the column foundation with the piles and loss of cross section and, I would like to know how it could take into account the damage to the piles in the mathematical model.
Any and all advice would be great
Thanks!!!
1- temporary supports
2- soil remove around piles
3- check and rehabilitation
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What might be the future of cable-stayed bridges in terms of need, choice, affordability and number !?
As this type of bridges is new, it will have more developments especially in the materials that used in construction.
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Could anybody share the details geometry and material properties of simple supported reinforced concrete bridge beam/girder based on following.
1. AASHTO, Eurocode or any others standard
2. Without prestressed strands, only reinforcement concrete (with reinforcement details)
3. geometry details based on different span
4. T-Beam/Girder or just simple rectangular beam
Methods of the calculus of variations could also be used to formulate the governing equations and hence the analysis.
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I would like to know if "2008 NYC DOT seismic design guidelines for bridges considering local site conditions" is implemented in practice or not. If anyone has some information regarding this it will be really helpful.
Regards…
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Hi everyone,
I am developing a shell element model for a concrete bridge. I am currently at a stage of assigning the traffic lane UDL.
As you can see in Figure 1, the traffic lanes are unfortunately at a angle (not 90 degrees) with respect to the horizontal direction, in other words, are not in parallel with the bridge span direction.
My model is shown in Figure 2. It is already been meshed.
Can someone please give me some hints on selecting the elements that are under the traffic lanes; hence I can apply required UDL on them?
if the lanes had been perpendicular to the horizontal, I would have used NSEL,S, LOC,Z,(elevation of bridge deck) and NEL,R,LOC,Y, (coordinate of the left and right boundary of the lane), to select the elements. However, it's been difficult when the angle is not 90.
Thanks.
Following..
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Hello all,
I would like to ask about how to model rigid and flexible joints "connections" in SAP 2000?
Check the following reference Please.. it might's assist you in your question … Regards…
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I am looking for any resources related to this field. It might include things like 1] aesthetic treatments to hard surfaces (soffit, paved traffic islands, bridge retaining walls, etc), 2] Lighting, 3] Signage, 4] Pedestrian and Vehicular Safety, 5] Greening of the interchange, 6] etc.
Regards…
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Bridge is of a 175m span, post-stressed cables, Software preferably in Sofistik AG, could be in Autodesk Robot 2012.
Check the following reference Please.. it might's assist you in your question … Regards…
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For Curve Segment Cable Stayed bridge. What is the design criteria for max. twisting moment to find manually as per IRC or lrfd or any other standard. or a any equation related to find twisting moment.
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I have to calculate the optimal thickness of well steining for a well foundaton having external diameter 11.6 m and depth 30 m.
IRC 78-2014 gives the formula h =kd√l .Using this formula, thickness will be about 1.9 m. It has been proposed to use Jack down method of well sinking.
Clause 708.2.3.5 of IRC:78-2014 allows to adjust the steining thickness according to design and construction requirement if specialised method of sinking such as jack down method are adopted.
Some case studies to mention here are:
Signature bridge, wazirabad in north delhi having 0.8m steining thickness for a well diameter 8m and depth 35-39 m (jack-down method used here)
Pretensioned sutlej bridge in Punjab having steining thickness 1.05m tapered to 0.75m for well having diameter 6m and depth 32m. (jack down method not used here)
According to the book "Soil Mechanics and Foundation" by B.C. Punmia page 789, steining thickness is given by
t =D/2{1-√1-4r/ρD} ; t is thickness, D is Dia of well, r is unit skin friction, ρ is unit weight of concrete for steining.
As per this equation for a constant skin friction, steining thickness should decrease with increase in diameter of well.
According to the book "Structural detailing in Concrete" by M. Y. H. Bangash, thickness of steining is given by
t=k(0.01H+0.1D) ; t is thickness, k is sub soil constant, D = external dia of wall , H is depth of well.
Using any of the formula, the thickness of steining wont come close to the thickness provided in the case studies i mentioned above.
By using Jack-down method of well sinking, thickness will be reduced, but how to calculate the optimum thickness of well steining in case of jack-down method?
I notice that the steining thickness equation provided in IRC 78-2014 gives the thickness which increases cost of the project.
Your esteemed comments and experiences are highly welcomed and appreciated on this topic.
Regards…
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Hello everyone
I am simulating the suspension bridge given on the pictures by ANSYS workbench.
However, I just add the earth gravity force(self weight ) on the structure but it has exceeded the allowable deflection in vertical direction.
So I was wondering whether the anchorages of bridge use the pull force to cancel the self weight of bridge?
I will very appreciate any replies.
Check the following reference Please.. it might's assist you in your question … Regards…
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I modeled a concrete bridge by sap2000 and developed nonlinear time history analyses to obtain maximum deck displacement in longitudinal and transversal directions. Could anyone have an idea about it?
Regards…
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how i can find the results of the " flieden bridge piled-raft foundation " paper ,if it possible please ?
Interesting..
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Hello,
I need to calculate the area which is less than 0.5Pa.
In Wall shear stress contour, I would like to calculate the area except for the red colored-legion.
Please let me know how to do it.
I have the data such as x,y,z, WSS and so on in the excel.
Interesting..
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I'm new in Bridge Engineering
How can I modelling a steel box girder (deck) using Midas Civil engineering software?
Check the following reference Please.. it might's assist you in your question … Regards…
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There has been historical mention of the construction of bridges in ancient societies even in B.C. times, but I have yet to find any documentation on any specific bridges from this time period. I am interested in learning more about these ancient bridges, but as most of these bridges are not still in existence I'll have to rely on documentation on the existence of these structures, or archaeological evidence proving they existed. How would I go about finding this information?
Check the following reference Please.. it might's assist you in your question … Regards…
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Are there mitigation measures put in place?
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for experimental analysis of scour depth at particular site, How can I proceed if I am starter in the civil engg. field ? What experiments are mandatory for this?
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I want to apply the statistical parameters (bias ,and COV) on three and four lane bridges but the available data can be used for one and two lanes.
I should have answered ages ago: AS5100:2017 is the Australian Bridge Design Code. If you have actual data for the road, you can determine which lanes are actually used by the heavy vehicles, and then do simulations yourself accounting for this. Lane preference for heavy vehicles allowed us to determine the likelihood of the actual traffic loading being heavy enough to cause a severely weakened bridge to collapse, and to use appropriate measure to control that risk during the repair period.
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I am looking for references regarding piers which are monolithically connected to deck at concrete bridges with prestressed-precast beams.
Check this out:
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For the analysis design and construction of a suspension bridge.
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I want to automate my bridge constructions for which I am using sap2000 OAPI.But I could not find any OAPI for the csibridge.
Does any OAPI exist for csibridge or it is provided for only for the sap2000??
sap2000 OAPI does not contains the substructure modules so please tell me how do I automate my model if it has substructures and other options (like bearing,abutments)which can be done in csibridge.
Efren Sandoval Mora
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I wonder if someone can send me reports or address of links that I can find relating to severe damages of concrete bridges in Iran based on past earthquakes.
Following
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my research about an experimental test on horizontally curved steel I-girder bridges, so I need the AASHTO LRFD formula 1998 for comparesion purpose
Interesting..
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For determining the acceleration parameter Ss and S1 the site class is compulsory to select first.
As per ASCE 7-10 which site class (form A-F) can be taken as it can be similar with the medium soil site given Indian Standard IS1893-2002?
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Both method consider that loading is at crown of masonry arch bridge. For a train having multiple axles at boogie, there is a standard loading as mentioned in brackets but that is a maximum axle load of any axle for that locomotive. If I get a value of Provisional Axle Load (PAL) by MEXE, how do i compare that with railway standards?
Regards…
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Design of bridges
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Hi everyone,
We know that AASHTO LRFD bridge design specification for stud design is based on the push-out tests performed by Slutter and Fisher. They proposed an equation showing the relation between stress range amplitude and number of cycles to failure for a shear stud as follows,
Δτ = 1020 n −0.186
where Δτ = stress amplitude and  n = number of cycles
Could anybody please tell me whether this relationship is accepted by AASHTO LRFD to calculate number of cycles to failure when stress amplitude is known. If not, then how it can be determined.
Regards…
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Physical modelling requires to assume some scale factor according to the available space for the model study.But it is also fact that low scale give good results(CHETN XIII-3,Briggs 2013, USACE). Why is it so? How is it related to scale factor?
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I am trying to calculate the fatigue life of a concrete structure under cyclic loading.
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The methodology for completion of fatigue assessment of concrete bridges is not that clear.
for steel structures, the procedure is vague. The code has been adopted based on Euro-code 3, but it seems that there is still a need of the old version of AS5100.6 in order to complete the assessment.
The effect of DLA is doubled in formula ( once has been applied in AS51000.2 as f* and again in AS5100.6). Considering this change and value for Lambda(t) , the fatigue life significantly reduce resulting in an adequate remaining life for bridges.
I would appreciate if you share your experience with the new code and provide procedure/examples that you have used in your assessment.
Regards,
Mehdi
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Dear Structural/Bridge Engineers!
As per AASHTO LRFD, we can ignore earthquake loads while designing of single span bridges. My question is if the span is long so should we consider the seismic loads or not?
Thanks
I think it depends on the seismic zone of your bridge.
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I am tryng to assess whethere the deflection under traffic load for a bridge slab is acceptable. Can anyone help with this ?
Hi Mohamed Wehbi, the unit of "L" will be the same unit of the answer, regardless of if you use meters, feet, inches...
Best,
Sálvio.
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A motorway bridge has collapsed near the Italian city of Genoa, sending vehicles plummeting some 100m (328ft) to the ground and killing at least 11 people, local media report.
Actually, the ADT increased along the years. As you mentioned, two cables were completely replaced with iron ones. There was a project for the replacement of the other prestressed cables.
I agree with you, the fatigue can be one of the reason assuming the sudden collapse. In addition, that bridge was the first one in the world that used prestressed concrete. It has been a civil engineeniring challange for tht time.
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I have designed a 60 meter (196.85 feet) simply supported cast in place (directly casting on bearing pad) post-tensioned prestressed concrete I girder due to the requirement for horizontal clearance of the respective channel following AASHTO LRFD Bridge Design Specification.
Do I need to consider any special check besides traditional design checking of post-tensioned prestressed concrete I girder?
Dear Pablo Krahl,
Thank you very much for your detailed response. Those documents are related to Precast system when the girder will be listed and shifted to place it in the desired position above bearing pad.
However, in my case, the girder is fully cast-in-situ. The formwork will be set above bearing pad (there will be no formwork in the contact place of girder and bearing pad, rather polyethylene will be provided in that place). The girder will be totally free of listing and shifting.
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Please provide the values or equations for (corresponding references if any available)
1. Crushing strain of confined core concrete
2. Spalling strain of Unconfined cover concrete
Thank you
A good equation for ultimate strain of confined concrete is that given by Mander et al. (1988).
eps_cu = 0.004 + 1.4ps x fyh x eps_sm / f'cc
where ps is the volumetric ratio of transverse reinforcement in confined concrete, fyh the yield strength of confining reinforcement, eps_sm is the fracture strain of confining reinforcement, f’cc is the compressive strength of confined concrete
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On pages 148-151 (RG numbers 171-174) of my book, Geometry-Do, I prove the skew angle theorem, some other related theorems and I solve several triangle construction problems.
Are there any structural engineers on Research Gate who have worked with skew bridges? Can you suggest any theorems or triangle constructions that would be useful in the construction of bridges?
I want to make my geometry book as useful as possible to engineering students and I will very much appreciate any suggestions.
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Hi all,
I am doing analytical study on behavior of chevron (eccentric) bracing with pall friction damper in RC structures using Etabs. I am looking details for mass, size and stiffness of pall friction damper connected between braces and roof.
Hi Shiva,
You can also try to contact the manufacturer directly. Pall Dampers are manufactured at Quaketek in Montreal (used to be built at Mechtronix), I’ve worked with them in the past in a research project.
The stiffness, mass and other parameters are well explained in https://www.quaketek.com/seismic-design/. The approximate sizes and masses are also on that page at the bottom. They have a guide for finding the optimum slip load that isn’t on their website, if you contact them they’ll probably help you out.
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I saw that in many design details of bridges.
Basically, piers constructed monolithically with the bridge deck are advantageous in the following ways:
(i) Movement of the bridge deck is achieved by the bending deformation of long and slender piers. In this way, it saves the construction cost of bearings by using
monolithic construction between bridge deck and piers. Moreover, it is not
necessary to spend extra effort to design for drainage details and access for bearing replacement. On the other hand, in maintenance aspect substantial cost and time savings could be obtained by using monolithic construction instead of using bearings as bridge articulation.
(ii) Monolithic construction possesses the shortest effective Euler buckling length for piers because they are fixed supports at the interface between bridge deck and piers.
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I am looking for the governing equations of infinite plate hole problem. For reference, i have added the picture. I have found the exact solution of the infinite plate hole problem in terms of stress and displacement however, i want to know the main governing equations in terms of differential equation.
I will appreciate this..
Thanks
Regards
Zulfiqar Ali
Use a Body fitted for eqs. Good luck.
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Indian standard code of practice for Prestressed Concrete Design  IS 1343 1980 had table number 12 for the design of Unbonded post tensioned concrete for varying l/d ratio and reinforcement index. However, the same has been removed in the recent revision of IS 1343-2012. Nothing is mentioned explicitly why it has been removed?
Does that mean Indian standards does not allow Unbonded PSC design in INDIA?
hello dear friend
if you use ADAPT software to model prestressed design, you can find it there
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Yesterday in the field we had some trouble with the bleeding in our concrete, the bleeding was adjudicated to the admixture (we use sikament 450 at .08% per weight of cement), here is some data:
·   We were constructing a part of a bridge column of 200 cubic meters, the F´c was targeted at 350 kg/cm^2, the concrete slum was aimed at 18 +3 cm.
·         Mix design
400 kg Cement
957 kg Gravel (3/4”) M.F. 6.7
783 kg River Sand M.F. 2.7
210 lt Water
3.2 Lt Sikament 450 (low range water reducer)
The aggregates satisfy the regulations and codes, but due to the severity of the bleeding, i want to find out:
1)      The probable source of the bleeding (I think it is the excessive use of dispersion admixture)
2)      How can I stablish the severity of the bleeding?
3)      Is the color or the bleeding water normal?
Bleeding is often a result of an "unstable" mix design. Sometimes the mix could be borderline, and with addition of an "overdosing" of admixture (which might still be within the manufacturer's recommendation), could result in bleeding as well.
Usually you might want to increase your powder to course agregate ratio, and/or your fine aggregate to course aggregate ratio.
I agree that the water of the mix could be cut as well, since the mix could be at risk of segregation as well with high water & water reducing admixture.
The colour of the water is most likely due to the water reducing admixture.
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I want to find the torsional and bending stiffness for a box girder. Is there any particular formulas or software which I can use do i need to find for individual member and then add them together?
Thank you for the help. that paper helped alot.
Regards
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Hi everyone
I am studying the suspension bridge.
But I can not find any information which is vertical and horizontal allowable / permissible deflections for suspension bridge.
who can tell me?
It is best to provide the links for me.
Thank you very much!!!
Hello Yonglin,
I agree with with Vidish that it depends on the code. The figures L/300, L/350 and even L/250 have all been quoted by different codes and authors. The reason being that there are different parameters to consider.
There are many papers on the public domain (internet), here is a nice one:
Wishing you the best.
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I need to do scaled down model studies of an existing river bridge. Froude number dynamic similarity would be maintained.I need to know the criteria for scaling down the size and properties of the river bed material to be used in the model.
Dear Vilayasheree, Hello
In scour studies around bridge piers, dimensional analysis based on effective variables (ds = f(flow parameters : V,h; sediment parameters: d50, σg, Vc; fluid : ρ, µ and g, Pier: D, Ks, etc.) leads to non-dimensional function as: ds/D = f1 (V/Vc, Fr, D/d50, y/D, Re, Ks=pier shape factor, Kθ=angle of attack for flow, KG=river geometry, ). For similarity all of this parameters should be same for model and prototype system. As it is difficult to satisfy this similarity criteria, you should use a distorted model.  Based on above dimensional analysis, for scaling down the river bed materials the similarity for D/d50 should be satisfied, in other words, the parameter D/d50 should be same for model and prototype. For non-uniform bed materials, this similarity should be satisfies by σg too.
The problem is when your scaled down bed material size be so small that could not be cohesionless, or when sediment size be smaller than 0.6 mm that ripple forms may be formed.
Regards
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Dear all,
Most of the research papers are showing academic applications of the various truss structure.
I would be glad if you please share some real world examples of various truss structures (as spatially for topology optimization). Please share related webs, images, pics etc.
Please refer trusses designed in the following papers
a roof truss for Elatanya hotel in Assuit Egypt
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bridge girder is placed on three columns placed next to each other . which method we have to opt to get optimum results to design ?
Hello Piriya,
If you know the loading, you may use the moment distribution method to obtain maximum moments. From there, you can then design the girders.
The following is a good example to follow for the design procedure:
I wish you all the best.
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In SAP  2000 in a analysis time history is the behavior of a link element that simulates the behavior of a force displacement of a hinge assumed when using the direct integration method?
Hellow  Ricardo José Simão
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Isolation Time Period T= 2 sec
Bridge is horizontally curved 3 spans box girder 88 m length
8 isolators - 2 under each pier and 2 at each abutment