Founding Dubai's skyline

While on my local intranet I noticed a new post about an article discussing the construction of Dubai's high rises from excavation to erection. The article refers to the help of a WSP Middle East structural engineer who explains the process in five easy phases. Each phase seems to incorporate parts which do not quite fit but for the average person that does not have a background in engineering or construction, this is a great article to help them understand the process.

LRFR Guidelines Revision #1 Clarifications

After a few questions from multiple consultants, RIDOT sent back responses to answer our questions.

These are our responses to your questions for clarification: (AECOM)


1. Page 21 – Load Rating Report: there is a statement in bold at the bottom regarding the color of the cover that states “… is any rating is…” My interpretation of this statement is that it is inclusive of the BP and OP vehicles. This would be a change from what we’ve been told previously (i.e. color of the cover determined only by the “legal” load vehicles)

Response: The color of the cover is not determined only by the legal load vehicles but by any rating and is independent of the controlling limit state and is strictly based on the controlling rating factors regardless of what controls the posting.

2. Page 22 – Load Rating Report Layout Table: Item 4 says “PE Stamp to be included” however there is no space on the reference sheet 24 for the stamp. Is the stamp required or just the PE number?

Response: The PE number is sufficient.

3. Page 22 – Load Rating Report Layout Table: Item 14 says “…and the written agreement of the independent reviewer.” Where can this written agreement be found?

Response: The independent reviewer should agree that the computations (Index, sketches, hand calculations..) are satisfactory in writing. Note, his signatures or initials on the computation sheets are considered a written agreement.

4. Page 24 – Summary of Bridge Rating: The new table now has a RL (TONS) input required for the HL-93 at Inv and Oper level where previously these were N/A and only rating factors were supplied. There has been some debate over what the correct vehicle weight is for the HL-93 notional load. What is the weight we should be using for this vehicle to get the rating loads (tons)?

Response: The rating of HL-93 in the new table is represented by an RF only for inventory and operating level and RL (Tons) are not applicable here since HL-93 is only a notional load.

5. There are a few times throughout the manual where the statement “…the initials of the reviewer shall be placed on every sheet of the calculations.” Are electronic initials sufficient for “hand-calcs” using programs such as MathCAD or are wet initials required?

Response: Any kind of initials will do.

6. Regarding the new vehicles I would like to make sure that what I’ve concluded from the new guidelines is correct:
a. RI-BP3 is a new vehicle
b. RI-BP4 was previously RI-OP2
c. RI-OP2 was previously RI-OP3
d. RI-OP2 was previously RI-OP4

Response: All the above correct except for d.
d. RI-OP3 was previously RI-OP4

If you have any further question, let us know.

Here are the answers to your questions: (AI)


1) On Page 6 Table #1 the HL-93 and Specialized Hauling Vehicles (SU4,SU5,SU6 & SU7) are listed as AASHTO Legal loads. Is there any reason?

Answer 1: The Specialized Hauling Vehicles are considered part of the legal loads per the MBE and FHWA regulations.

2) Response: The color of the cover is not determined only by the legal load vehicles but by any rating and is independent of the controlling limit state and is strictly based on the controlling rating factors regardless of what controls the posting.

Does this include also HL-93 vehicle?

Answer 2: The HL-93 is a notional load and not an actual vehicle, and should not be considered in deciding the color of the cover.

3) Could you clarify which legal loads are we going to use for posting analysis?

Answer3: Page 24 Rating Table includes Posting Column, the posting values should be calculated for every single vehicles listed in that table except for

HL-93. RIDOT will decide later how the posting signs will be carried out across the state.

After all of this we still noticed one change that the new RI-BP4 is not the same as the previous RI-OP2 with changes in the spacing between the last two axles previously 4'-6" and now 4'-3".

 
You are right the RI-BP4 was previously RI-OP2 and the rear axle spacing should be 4’-6”. It was a typing error in our latest manual and we will correct.

LRFR Guidelines Revision #1

Just received revisions to RIDOTs Load and Resistance Factor Rating (LRFR) guidelines which we use for our RIDOT bridge load ratings. The major change is the addition of six new permit trucks (RI-BP3, RI-BP4, SU4, SU5, SU6 and SU7). The down side to more permit trucks is of course the increase amount of work needed to satisfy the client. The up side is knowing that your client is satisfied with having a better grasp on which live load combinations certain structures can handle.

Hybrid Steel Girder Ratings (Cont.)

The Wrentham hybrid steel girder bridge ratings are moving forward, yesterday I was able to complete the first draft of the text for the report, organize information for VIRTIS input and finish the dead loads. Today I will be setting up the live load distribution factors and beginning one of VIRTIS runs.

Hybrid Steel Girder Ratings

Its been almost four months since my last rating for MassDOT and I could not have asked for an easier way to get back on the horse than a hybrid steel girder. A hybrid steel girder is simply a girder which contains different grades of steel in the flanges and web. Typically a hybrid steel girder consists of a high strength steel (HSS) for the flanges and a lower grade for the web.

This will be my second go around rating a hybrid girder bridge and this time it I have a pair of simple span bridges with a minor skew. The bridges are almost cookie cut having the same span length, girder spacing and skew.

Along with rating the girders, the reinforced concrete deck must also be rated. The deck is 8.5" thick with a girder spacing of 8'-9". 

Over the next couple of months I will be working on these off and on and will try to give updates along the way.

United by Bridges

Received my WSP magazine today "United by Bridges" has a couple great articles which include international inter office assistance with designs and inspections, it's a great way to share knowledge.

ASCE conference in Seattle

Just found out my good friend Phillip Lanergan will be presenting at an ASCE conference in Seattle this coming July for his work on the East Boston CSO. Good luck Phil.

AMTRAK Fracture Critical Inspections

This morning I found out that we will begin our fracture critical inspections of several bridge which intersect AMTRAK. Last March I has my AMTRAK rail road safety training down in Providence which prepares consultants for working in the AMTRAK right of way safely. Unfortunately these inspections will be taking place late at night in the dead of winter. One thing that is always present at an AMTRAK inspection is waiting. Waiting for the safety briefing. Waiting for access to the tracks. Waiting for the power to be turned off and lines to be grounded. Hurry up and wait.