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  1. CanyonRat

    Conspan LA

    Seems to me you are looking at a RR bridge?. I'm pretty sure that the program can handle different spacings with different girders but I don't know about the DF's. Leap will make special runs for you but I'm sure you'll have to pay. MikeD
  2. CanyonRat

    Concrete Pile Caps - Shear Design

    Maybe consider the wet concrete of the diaphragm if there is one? Most states have standardized reinforcing for simple pile caps at abutments and the reinforcing need not be checked if piles are under the girders. Make sure you satisfy yourself with this of course. One easy method is to just...
  3. CanyonRat

    Bridge Widening

    40' is too long for a slab unless it's prestressed. I've been involved with a lot of widenings over the years and a few times have switched girder types with no problems. It does help to have the substructure on piles... Also worked on widening a few T-girder bridges. Just match existing for...
  4. CanyonRat

    AASHTO loading interpretation for Pier design

    I've been reviewing this thread and am finding it very interesting. I don't think I've ever run in to this type of bridge design even though it is very common. I'm betting most people design the substructures for a truck in each span. I always make sure the bridge is continuous for live load...
  5. CanyonRat

    Operating Rating Level - interpretation

    Operating Rating: Represents the absolute maximum permissible load level to which the structure may be subjected to. To find out the different operating level requirements you have to talk to the owner; usually the state dot. This can be adjusted. If you slow the vehicle down to 5mph (not...
  6. CanyonRat

    PSC box bridge design

    A 50-m span cannot be transported w/out splicing the girder. Therefore, the individual girder pieces will require prestressing but post-tensioning will be required to put the pieces together. The other option would be to cast on-site. Or, the other option would be a cast-in-place PT girder...
  7. CanyonRat

    Questions on PE license requirement:

    You can call yourself an engineer, just not a professional engineer, at least in Utah. #1 No, you will need a licensed engineer to review. #2 Yes, imo. See my comment above. My dad's business card says 'Drilling Fluids Engineer'. He is not a licensed engineer and does not have a degree but he...
  8. CanyonRat

    Base plate design

    I have a very good example (my own) but it would probably be easier to fax it to you than try to explain. Email me off broadband at miked<at>horrocks<dot>com That's miked@horrocks.com in case the web site hides the email addresses. MikeD
  9. CanyonRat

    Expansion Bearing

    I work for 3 state dot's and their policy is no expansion joints unless the bridge is over 300' to 350' long. Now, I design simple span bridges all the time up to 120' to 140' long and have never used expansion joints. These bridges are either on piles or caissons. Our firm designed a 190'...
  10. CanyonRat

    Retraining as a structural engineer

    1) Job/career stability? I've never been laid off and for the most part have stayed busy. Most engineers change jobs quite a few times. Sometimes it's busy and sometimes slow. I worked for a state dot for 7 yrs; job was very secure but pay sucked. 2) Likelihood of getting on with State DOT...
  11. CanyonRat

    Load Rating for CIP PT Box

    Well... It looks like you already did cross-post. MikeD
  12. CanyonRat

    Load Rating for CIP PT Box

    This isn't really a code issue. Why don't you crosspost your question in the Bridge Engineering Forum located in the 'Engineering Forums by Industry' section. If you have the shear demands and capacities and you are using LFD it should be fairly easy to do by hand. As I recall WinBDS should...
  13. CanyonRat

    Factor of Safety Questioned

    JAE: Good explanation; much better than mine. One addition to number 5. I was going to mention the statistical side but was tired of typing I guess. LRFD has been statistally 'calibrated' pretty much across the board at least for bridge design. ASD is not really as far as I know. Maybe pieces...
  14. CanyonRat

    Factor of Safety Questioned

    >I found the following statement in one of the responses to >a forum question. I would like to hear some >opinions/discussion regarding FS relating to this following >statement: > >“I would calculate the bending moment based on the real >load, not the safety factor. AISC has its own safety...
  15. CanyonRat

    AASHTO LOADINGS

    Nope. Any Bridge text should have it and it's also shown in the AASHTO Standard Specification for Highway Bridges. MikeD
  16. CanyonRat

    effects of vibration

    I'm going to respond to d) only: You will need to change the natural period of the structure to account for the vibration. This is done by changing the stiffness and/or adding an offsetting mass to the system (increasing the mass of the foundation). Dampeners can also be incorporated. The...
  17. CanyonRat

    Elastic Seismic Design loads on (older) Bridges

    You are right about comparing the two. Several years ago I was involved in some bridge designs where we performed the seismic analysis / design using both methods. Everything is hardcopy and packed in boxes somewhere. I remember two main things after finished: 1)Don't try and mix and match the...
  18. CanyonRat

    Difference between Longitudinal and Transverse LL DF

    12 years experience with bridges; Worked for a state dot bridge program for 3 yrs with more experienced bridge engineers who knew the AASHTO code inside and out; State DOT's are on the AASHTO Committee and therefore have resources and in depth knowledge of the code. There were also several...
  19. CanyonRat

    Difference between Longitudinal and Transverse LL DF

    Section 3.23.4 is only for bridges that utilize the top flange as the driving surface such as deck bulb-tees or PS Slabs. Section 3.23.4.2 is saying that wheel loads on other girders don't effect the girders next to it. Section 3.23.4.3 gives you the distribution factor (aka load fraction or...
  20. CanyonRat

    P/S box beam end reinfocement

    You need to use the 12&quot; end block. Place a bunch of stirrups or even the grillage within the 6&quot; region. If you use the 1.5&quot; clear you can easily add 20 more rows of the stirrups by adding transverse rows in the end block. The girder is 48&quot; wide so you can fit 20 rows of...

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