abbaskhan2294

The full scale pile group load test would be quite difficult to execute + due to defective piles there are greater chances of settlement and thus making the entire pile group sink as a result extra loss to the contractor and a complete failure of project. So I would rather opt for concrete core tests. In addition GPR will be useful in giving idea about the condition of pile. So any pile with weak concrete mix will possibly be identified using GPR as per my observations.

Thanks bro for your reply. Exactly what I have been thinking to adopt. If there is any pile that is not meeting the standards will definitely have a changed profile and will be helpful in indicating the defective pile. In addition destructive tests on extracted cores will aide to the investigation.

Hello members I hope this thread finds you well. My query today is related to compressive strength of concrete bored piles. The issue is that pilegroup with 24 no of piles have been casted almost two years ago but there were observations regarding quality control on couple of piles in the group which are not known. Now the higher-ups are recommending to resume the project again and unfortunately I'm the incumbent and have to propose a methodology. Now the question is that since the piles are already buried underground, which procedure shall be adopted to predict its compressive strength near to its actual. Your suggestions will highly be appreciated. Thanks.

Hello. Can I get a general detail of RRM (Stone Masonry) retaining wall bearing details like PCC band, weep holes, through stones etc. Also any equation for evaluating the shear capacity of the stone-mortar joint which is a structural limit state for design of RRM retaining wall? Thanks

Hello everyone. I have a question that can a main beam be supported on confining column in a confined brick masonry structure? Does the anchorage between confining column and masonry ensures the load transfer from column to masonry?

Dear Umar Bhai why shorter directions are preferred for construction joint over larger direction? Is it because of the controlled shear demands in the shorter as compared to the longer ones? please enlighten your knowledge on this. Thanks

There can be certain conclusions to this. 1) crack as mentioned by Umar bhai are not bad and nothing to worry as such unless they are within acceptable ranges of the code. Structural cracks maximum size is 0.40mm or 0.016 inch and crack widths shall be monitored regularly. 2) The development length if not provided adequately can also be a reason for these cracks giving a feeling that the positive reinforcement provided is less than the actual case as shown here. The cracks are flexural cracks originating at extreme fibres with clear visibility to fainter ones at the mid. It should certainly not be an issue but shall be monitored for avoiding any inconvenience in future.

I have a query related to this. Mostly rafts are two way slabs with moment distribution in both directions. My question here is that why the location of construction joint is not considered for the other dimension since that bending with produce shear too for which the location provided is not adequate. Experts are requested to give their expert opinion on this. Thanks.

The solution in the sketch is pretty straight forward but none of the clients will agree to this solution as he would be losing his valuable space. Also, In order to avoid any tension you can also not go into the property line of others as it would either lead to damage of their structure or yours in future during excavation procedures. I believe perpendicular strips designed for flexural can control the overturning provided the you have enough development length for transfer of moments to adjacent perpendicular strips. The mechanism would be that the torsion (overturning) in the edge wall footing shall be transferred as moment in the perpendicular strips and the reinforcement provided on fully development will prevent the overturning of the edge footing.

The number of bole holes as stated by Umar bhai is dependent on your engineering judgement and site variability. However, literature have different opinions regarding this topic. E.g A literature suggests that for every 2500 sft one bore hole should be made. Another suggests to have minimum of 3 bore holes for site with soil relatively having similar properties whereas for variable soil a minimum of 5 bore holes should be made with 4 on corners of periphery and one at the centre. So it all depends on your experience and given site conditions.

Well I got a few solutions for the problems and I will list them below: 1- providing tie down anchor on the right extreme end of the footing. 2- projecting footing of the edge wall in L shape at the tension end to provide firm support through length of the wall. 3- Rather then starting the wall in masonry right from footing , cast the wall in RCC to plinth level and protruding reinforcement in the slab to resist the overturning. 4- providing perpendicular strip footings and designing it for negative reinforcement to resist the overturning of the adjacent Edge wall footing. out of these all #3 and #4 were found to be the best solution in terms of cost saving. Please add your comments too. Regards

Is there any benchmark of development length for the connection to be assumed rigid or pinned? I heard that 3/4 of full development length is the threshold between pinned and rigid connection.

I have a question related to design of edge strip footing. Below is the sketch for illustration. The footing to be designed is a strip footing that is going to support a brick masonry wall on top. The literature on every footing design suggests that the resultant load should act within kern of the footing and if its outside the kern then increase the width and that's pretty much it. However in practice for edge strip footings the perpendicular strips are reinforced with negative reinforcement for preventing the overturning of the footing and as a result the uniform stresses distribution in soil is achieve and differential settlement/overturning is prevented. Here in my case, the building is erected from basement and the finish floor level is 4 ft above the NSL. The foundation of only one load bearing wall is to be erected 3 ft below NSL and in such case no perpendicular strips are available to prevent the overturning as they are erected below the basement level. What's your take on this? I believe if a footing is designed rigidly it will have the tendency of uniform stresses distribution in soil and will not cause overturning. Please provide your opinion on this as this is one common issue in design practice. Regards

So the backspan has to counteract same moment as that of the cantilever. Is that all I need to care about? Development length offcourse would be fulfilled by meeting criteria no.1

Hello everyone. I have a cantilever beam spanning 16 ft and supported on a load bearing wall. Can anyone provide details about cantilever backspan with reference to code?

But wont the use of cracked properties increase the time period and amplitude of the structure and will this behaviour simulate the actual response of the structure when subjected to seismic excitation?

Thanks for the indepth analysis to the topic. However for very long columns that cannot be casted in one pour where shall the cold joint be preferably located? Also in which conditions shall dowel bars/key be provided in cold joints in raft?

can you suggest design codes/manuals for design of masonry in brick and concrete blocks?

Here I found one in JC Mccormic book.

Wassalam Waqar. Thanks for taking out time and addressing my query. I'm looking for these statements with a reference document (if available). Can you please provide some references that can clarify these points to me?

Hello everyone. I want to know couple of things related to detailing in RCC particularly column as; 1) Is there any limit imposed by ACI on percentage of curtailment of bars in the columns located at at two different levels? Lets say; I want to extend 12#8 bars from 24#8 (almost 50% curtailment). Is there any permissible limit for this curtailment. 2) Is there any provision in the code for the splicing of two different bar sizes in columns extending from the bottom level to top; lets say splicing #8 (extended from bottom story column) with #6 (right above).

AOA everyone. I need some guidance regarding the construction of confined masonry directly over the frame structure i-e it should not be erected from foundation. What does your engineering judgement suggests? Is there any reference available on this particular thread? Thank you.

Design shear wall from the old model without scale factor and moment frame from the same model if columns are taking more than 25% of the total design base shear. Incase columns are taking less than 25% of the design base shear then modify the model with an upgraded scale factor so that your moment frame is designed for atleast 25% of the design base shear. I hope it helps. Goodluck!

Dear Badar, I read your comment somewhere on section modifiers to use uncracked modifiers for obtaining stresses/forces. I'm now looking keen into this issue as I was modelling a structure and the columns had more than 6 sq.in difference of reinforcement between uncracked and cracked (with cracked being the greatest). I was just thinking about the UBC-97 code defining the section modifiers for the lateral force resisting systems. Code has specified three lateral force resisting systems as moment resisting frames, Braced building system and dual systems. Now if you play with the modifiers in each of the case you will see how the load distribution behaviour in the building system is. It means that section modifiers do play a crucial role in design and should be used as given by ACI for beams,slabs and columns accordingly. Also strength based design comes into play after concrete fails in tension and we know that even if steel is provided, cracking of concrete will occur prior to the yielding of steel. I'm sure many professionals are still facing confusion on this topic and it needs to be addressed. Would like to have your useful insight on it. Thank you!

That's a wonderful explanation. Thank you so much!