UmarMakhzumi

Ali, Both would result in the same analysis results. However, for a given zone, ACI might have different reinforcement detailing requirements then AASHTO. That is the only plausible answer that comes to mind. Thanks.

The distance has significance as it shows the length in which more reinforcement is required than the rest of the beam. Concrete is poor in compression. Reinforcement or rebars are used to provide required tensile capacity that concrete can't provide by itself. The reinforcement requirement varies along the length of the beam. For a simply supported beam (beam with 2 supports) more reinforcement is required at the middle than at the ends (like your case). Therefore, instead of providing continuous bars throughout, engineers provide additional bars where extra reinforcement is required. In that was they save on steel quantity The only catch is that the additional reinforcement should be long enough so that it develops completely. You can read more about development length of rebars here. Thanks.

@engruzair post preview feature is back. You can preview the post by clicking the second from left button on toolbar. Visit the following link for further details: https://invisionpower.com/news/new-in-4112-post-preview-r968/ Thanks

We are glad to have you on the forum. The real credit goes to all people who have been active on the forum.. In addition to Rana, Baz, EngrUzair, WaqarSaleem, Ayesha, AQ etc have been consistently active. The more active users, the more we get to spread our message. The aim is to get maximum Pakistani Structural Engineers on this forum and then work together to make recommendations to Pakistani Building code, best practises and structural issues that can improve engineering practise and ensure public safety. Thanks.

Thanks guys! I think its a great idea and something should be done. Maybe when I will come to Pak this December, I will arrange something in Islamabad. Thanks.

Clearly not a design failure as the other spans are standing. Lets see what comes out of the investigation report. I hope they are able to find the root cause. Thanks.

All, We are 4 years old. Thanks You for your support. SEFP turned 4 years old on May24th. I was travelling so couldn't post this on time. Thanks.

You can provide truss below deck to transfer load and keep the arches but instead of making them lattice, you can just provide minimum angles/ channels and keep it non structural. That would keep cost low. The structure load requirements aren't that great and you can play a lot with load path. Also, be careful when doing connection design. While designing connections, do make sure your design matches analytical model. Thanks.

I will just add to what Rana has said. To control torsion, the best thing you could do is to have new shear walls at perimeter of your building. They would add the most value interns of controlling torsion. Thanks.

You can also use Response 2000 for deep beam analysis and design. The best part is that it is free. http://www.ecf.utoronto.ca/~bentz/inter4/inter4.shtml Thanks.

Hi Alex, I would advise that you go through the ETABS Watch & Learn Tutorials and ATKINS ETABS Manual as a starting point. Both would help you get up to speed on modelling and design. ETABS Watch and Learn: https://www.csiamerica.com/products/etabs/watch-and-learn ATKINS ETABS Manual: Thanks.

Hi Sami, Overlap shouldn't be a big issue. I would suggest that you do a manual calc and compare weights. I am very confident that your numbers would match with ETABS. For the questions: Please see this: The last comment on the thread address when to consider and when to ignore torsion. For interior beams, torsion can be ignored safely. For edge beams, ignoring torsion would result in higher deflection of slab. Please do ask any follow up questions should you have any. Thanks.

For any structure we need load path for gravity and lateral. So lets discuss both one by one. Your structure is a lattice truss structure. My first observation is that this type of structure is an overkill for pedestrian bridge. Reasons being that a lattice structure involves numerous connections and that would increase fabrication cost in addition to over-design. Lets talk about gravity load path. The vertical load that you need to transfer is the weight of pedestrians standing on the bridge and the weight on the structure itself. My first observation is on your framing. You have got two arches (I would call the concave and convex trusses as arches for simplicity). Lets call them the inverted U and V shaped arch. Why do you need 2 arches? Shouldn't the inverted U shaped arch be good along with cables suspending down supporting the deck? In that case you can even eliminate the columns. If you want to retain the columns, you are even better off providing a truss below the deck to transfer the load/ weight of pedestrians to the columns. And you don't need a lattice arch. Also for pedestrian walkway is not straight. I wonder why? The structural concept is not robust. Now for lateral load path. Your columns are stabilized by 4 braces which are in fact lattice trusses which in my opinion are totally unnecessary. The simplest thing to do would be to create a 3D frame and have a truss bridge connected to it and not have these braces at all. For a sketch of how the 3D frame should look like, have a look at: Once you do that, you should be fine. Using standard members and least connections, you can make this happen. In addition to above, there is a bridge replacement project going on in Edmonton these days. Have a look at the website to get some design ideas: http://www.edmonton.ca/transportation/road_projects/walterdale-bridge-features.aspx Thanks.

Read this: and this:

Read this: Thanks.

You need to look at summary printout of ETABS analysis. Thanks.

Hi Waqar, Sorry for the late reply. Have been very busy for last week. I quickly ran your model and noticed that it is unstable. Please see the log below. Thanks. SAP2000 v17.1.1 Advanced (Analysis Build 9267/64) File: C:\Users\uma75058\Desktop\SAP2K\bridge-loads-corrected.LOG B E G I N A N A L Y S I S 2016/05/19 11:41:35 RUNNING ANALYSIS AS A SEPARATE PROCESS USING THE ADVANCED SOLVER (PROVIDES LIMITED INSTABILITY INFORMATION) NUMBER OF JOINTS = 1580 WITH RESTRAINTS = 32 NUMBER OF FRAME/CABLE/TENDON ELEMENTS = 4629 NUMBER OF SHELL ELEMENTS = 18 NUMBER OF LOAD PATTERNS = 12 NUMBER OF ACCELERATION LOADS = 6 NUMBER OF LOAD CASES = 12 E L E M E N T F O R M A T I O N 11:41:36 L I N E A R E Q U A T I O N S O L U T I O N 11:41:36 FORMING STIFFNESS AT ZERO (UNSTRESSED) INITIAL CONDITIONS TOTAL NUMBER OF EQUILIBRIUM EQUATIONS = 9378 NUMBER OF NON-ZERO STIFFNESS TERMS = 198177 * * * W A R N I N G * * * THE STRUCTURE IS UNSTABLE OR ILL-CONDITIONED !! CHECK THE STRUCTURE CAREFULLY FOR: - INADEQUATE SUPPORT CONDITIONS, OR - ONE OR MORE INTERNAL MECHANISMS, OR - ZERO OR NEGATIVE STIFFNESS PROPERTIES, OR - EXTREMELY LARGE STIFFNESS PROPERTIES, OR - BUCKLING DUE TO P-DELTA OR GEOMETRIC NONLINEARITY, OR - A FREQUENCY SHIFT (IF ANY) ONTO A NATURAL FREQUENCY TO OBTAIN FURTHER INFORMATION: - USE THE STANDARD SOLVER, OR - RUN AN EIGEN ANALYSIS USING AUTO FREQUENCY SHIFTING (WITH ADDITIONAL MASS IF NEEDED) AND INVESTIGATE THE MODE SHAPES NUMBER OF EIGENVALUES BELOW SHIFT = 0 L I N E A R S T A T I C C A S E S 11:41:37 USING STIFFNESS AT ZERO (UNSTRESSED) INITIAL CONDITIONS TOTAL NUMBER OF CASES TO SOLVE = 12 NUMBER OF CASES TO SOLVE PER BLOCK = 12 LINEAR STATIC CASES TO BE SOLVED: CASE: DEAD CASE: LIVE CASE: EQX CASE: EQY CASE: EQY- CASE: EQX- CASE: EQX+ CASE: EQY+ CASE: WX CASE: WY CASE: WX- CASE: WY- A N A L Y S I S C O M P L E T E 2016/05/19 11:41:37 SAP2000 v17.1.1 Advanced (Analysis Build 9267/64) File: C:\Users\uma75058\Desktop\SAP2K\bridge-loads-corrected.LOG B E G I N A N A L Y S I S 2016/05/19 11:41:43 RUNNING ANALYSIS AS A SEPARATE PROCESS USING THE ADVANCED SOLVER (PROVIDES LIMITED INSTABILITY INFORMATION) NUMBER OF JOINTS = 1580 WITH RESTRAINTS = 32 NUMBER OF FRAME/CABLE/TENDON ELEMENTS = 4629 NUMBER OF SHELL ELEMENTS = 18 NUMBER OF LOAD PATTERNS = 12 NUMBER OF ACCELERATION LOADS = 6 NUMBER OF LOAD CASES = 12 E L E M E N T F O R M A T I O N 11:41:43 L I N E A R E Q U A T I O N S O L U T I O N 11:41:43 FORMING STIFFNESS AT ZERO (UNSTRESSED) INITIAL CONDITIONS TOTAL NUMBER OF EQUILIBRIUM EQUATIONS = 9378 NUMBER OF NON-ZERO STIFFNESS TERMS = 198177 * * * W A R N I N G * * * THE STRUCTURE IS UNSTABLE OR ILL-CONDITIONED !! CHECK THE STRUCTURE CAREFULLY FOR: - INADEQUATE SUPPORT CONDITIONS, OR - ONE OR MORE INTERNAL MECHANISMS, OR - ZERO OR NEGATIVE STIFFNESS PROPERTIES, OR - EXTREMELY LARGE STIFFNESS PROPERTIES, OR - BUCKLING DUE TO P-DELTA OR GEOMETRIC NONLINEARITY, OR - A FREQUENCY SHIFT (IF ANY) ONTO A NATURAL FREQUENCY TO OBTAIN FURTHER INFORMATION: - USE THE STANDARD SOLVER, OR - RUN AN EIGEN ANALYSIS USING AUTO FREQUENCY SHIFTING (WITH ADDITIONAL MASS IF NEEDED) AND INVESTIGATE THE MODE SHAPES NUMBER OF EIGENVALUES BELOW SHIFT = 0 L I N E A R S T A T I C C A S E S 11:41:43 USING STIFFNESS AT ZERO (UNSTRESSED) INITIAL CONDITIONS TOTAL NUMBER OF CASES TO SOLVE = 6 NUMBER OF CASES TO SOLVE PER BLOCK = 6 LINEAR STATIC CASES TO BE SOLVED: CASE: EQX CASE: EQY CASE: EQY- CASE: EQX- CASE: EQX+ CASE: EQY+ A N A L Y S I S C O M P L E T E 2016/05/19 11:41:44

Did you model this in SAP? If yes, can you upload the file. The top and bottom chrod of your truss would be "continuous", or else your model will be unstable. How have you modelled them? I need to know this before I answer your question. Thanks.

So another way to put the question would be: what would happen if shear wall is under-reinforced in a dual system? How would the frame behave? What would be the limit state? This is a tricky question as the analysis technique requires frames in dual systems to be independently checked for X% (50% I guess but don't remember) of base shear. However, the lack of ductility in shear wall would result in loss of stiffness, and the frames would start to pick up as soon as the wall cracks. Its hard to predict what would happen as there could be a number of scenarios. Thanks.

There should be no problem for pouring successive slab within 24 hours if you meet temperature requirements. Roughen the existing and pour the new as long as you stay within the temperature. Use thermocouples are stated above.

I work in Oil and Gas sector where one would rarely come across slab design. I used to work in commercial and used SAFE at that time. Thanks.

So your results do match for the middle strip? Is there anything in the manual.. @Rana Waseem may be able to answer as he uses SAFE a lot. Thanks.

Everything that you need to know including a step by step tutorial to model masonry infills: Thanks.

Here is an update: 3-Storey Library Building In Karachi.pdf Four Storey Office Building In Muzaffarabad.pdf Stone Masonry School In Abbottabad.pdf Storey Mixed Use Building In Karachi.pdf 6-Storey Mixed Use Building in Karachi.pdf And finally a step by step method on how to create and analyse your model. A_Practical_Guide_to_Nonlinear_Static_An.pdf The attachments are conclusive in manner that they provide extensive informaiton about modelling infills. For further information related to subject topic, please also visit: http://framedinfill.org/ Thanks.

I will add to what Uzair has said. For mass concrete, recommendations of ACI 207 are used to reduce heat of hydration during curing. This involves replacing cement with a recommended percentage of fly ash and water with crushed ice. The temperature inside foundation is monitored using thermocouples. Generally, contractor has to ensure that no part of concrete mass is allowed to become cooler than the hottest part by more than 20oC (68oF). Thanks.