EngrUzair

Aoa. Heartiest congratulations to the Administrator, the moderators and the members. I strongly second waqar saleem. Regards.

WA. UBC Section 1630.9 deals with Drift and Drift Calculation requirements. Section 1630.9.1 outlines the procedure for determination of Delta_S i.e., structural deformation due to seismic effects, whereas Section 1630.9.2 is related to the determination of Maximum Inelastic Response Displacement (Delta_M). Story Drift Limitations are given in UBC Section 1630.10. Regards.

1. According to ACI Concrete Terminology 2013, Mass Concrete is "any volume of concrete in which a combination of dimensions of the member being cast, the boundary conditions can lead to undesirable thermal stresses, cracking, deleterious chemical reactions, or reduction in the long-term strength as a result of elevated concrete temperature due to heat from hydration." Now, first of all it is necessary to check whether your concrete really comes under the definition of Mass Concrete or not. ACI 207.1R-05 does provide basic information & general guidance about mass concrete, but it does not specify any minimum dimensions of concrete to qualify as 'Mass Concrete'. Following links however suggest some critical dimensions of concrete to consider it 'mass concrete', as well as useful information regarding placement of mass concrete and recommended practice for effective control of heat of hydration & thermal cracking in mass concrete. a. https://www.concrete.org/tools/frequentlyaskedquestions.aspx?faqid=650 b. http://people.wallawalla.edu/~larry.aamodt/engr325/concrete_heating.pdf c. http://www.nrmca.org/aboutconcrete/cips/42p.pdf d. https://www.structurepoint.org/publication/pdf/pdh-Mass-Concrete-Structures.pdf e. ACI 301-05, Section 8 Mass Concrete (Includes required concrete placement temperatures, among others) f. http://people.ce.gatech.edu/~kk92/massconcrete.pdf g. http://www.agcia.org/documents/Mass Concrete Thermal Control.pdf In case your concrete tunnel lining actually falls within definition of Mass Concrete, you will need to adopt suitable measures (including installation of thermocouples, as advised above by Umar) to keep the concrete temperatures within limits recommended for mass concrete. 2. Alternately, you may ask your consultant to provide you the calculations to prove that concreting you are doing is mass concrete, and also to provide you the reference that requires waiting for 72 hours, to start the next pour. 3. You may possibly do such calculations yourself too, provided you have relevant temperature values and other required information. Guidance is available in following document:- http://www.oea.org.lb/Library/Files/Arabic/Downloads/Reports/ندوات ومؤتمرات/Presentation Mass Concrete OEA dec 20.pdf I don't have some reference now. However, if the tunnel lining concrete does not qualify for mass concrete, in the light of documents referred earlier, or (as already said earlier) the concrete reinforcement design & placement is adequate to counter both the applicable loads as well as thermal cracking, 72 hour restriction might not be applicable. In such a case, you can start next pour earlier. Regards.

Here are my 2 cents:- 1. It depends upon whether the design code, you are following for your project, permits the use of brick masonry struts for the seismic resistance in general, and also in Zone 3 or otherwise. Following links discuss how some of the design codes account for the use of brick masonry infills for seismic resistance:- a. Brick Masonry Infills in Seismic Design of RC Framed Buildings_Part 1.pdf b. Brick Masonry Infills in Seismic Design of RC Framed Buildings_Part 2.pdf 2. Discussion at the following links, might help you understand how you can model brick masonry infills in a structural software. like ETABS or SAP2000: a. Modelling of brick masonry in ETABS with reference to Indian Standard Code (1) http://www.sefindia.org/forum/viewtopic.php?t=15975 (2) http://www.sefindia.org/forum/viewtopic.php?t=9922&postdays=0&postorder=asc&start=0 b. Modelling of brick masonry in SAP2000 with reference to FEMA 273 https://www.researchgate.net/post/How_can_I_model_masonry_infill_in_sap_2000_as_an_equivalent_strut HTH Regards.

There are two aspects of this question: a. When the concrete is to be placed in single layer, as in a tunnel construction (what IMO OP has asked for) Recommendations regarding maximum horizontal length of concrete pour for this case, are given in ACI Standard referred in my previous post. When the concrete is reinforced properly, to withstand applied loads as well as thermal cracking, next or adjacent layer of concrete may be cast both sooner (the same day) as well as later (e.g., next morning), depending upon availability of concreting party. Proper construction joint should however be provided at the face of concrete common between the two pours. When the the concrete is to be cast in panels, separated by expansion joints (as in the case of concrete pavements), casting is generally done in alternate panels at one time. b. When the Mass Concrete is to be laid in multiple-layers Guidance regarding Mass Concrete is given in ACI 207.1R-05. AFAIK, no specific time duration has been given by ACI for placement of successive layers in a mass concrete. However, last paragraph of ACI 309R-05 Section 7.2 provides general guidance in this regard, in following words: "When the placement consists of several layers, concrete delivery should be scheduled so that each layer is placed while the preceding one is still plastic to avoid cold joints. If the underlying layer has stiffened just beyond the point where it can be penetrated by the vibrator, bond can still be obtained by thoroughly and systematically vibrating the new concrete into contact with the previously placed concrete; however, an unavoidable layer line will show on the surface when the form is removed." Ways and means are available for execution of large mass concrete works in a single casting operation. Following link gives details of such a mass concreting job, involving casting of 5.5 m (18 ft) thick concrete slabs at 70 m (230 ft) depth belo ground level, carried in one-go using self-compacting concrete. http://www.silicafume.org/pdf/reprints-201407.pdf Regards.

Refer to "ACI 224.3R-95 Joints in Concrete Construction", Chapter 7 at the following link, for your required information:- http://xa.yimg.com/kq/groups/2173108/199513267/name/2243r_95.pdf Regards.

Dear Usman, Here are a few links, containing examples of raft foundation design :- 1. https://falmatasaba.files.wordpress.com/2013/04/design-of-mat-sd.pdf 2. http://www.nptel.ac.in/courses/105104137/module5/lecture 3. https://www.youtube.com/watch?v=tobZOK_2s8E (See later part of video, for raft foundation design) You may find even more, through a clever search on the internet. Regards.

WA. Links and documents at the following web address, might help you in this regard. https://www.google.com/search?q=minimum+floor+vibrations+criteria+for+industrial+buildings&ie=utf-8&oe=utf-8 Regards.

An intelligent internet search may also lead you to links and abstracts for the impact factor publications. These are generally available for purchase online, costing around 35 US dollars per paper..

For proper application of Mass Source, you may refer to the following links: 1. http://www.sepakistan.com/topic/191-use-of-mass-source-command-in-etabs/ 2. http://www.sepakistan.com/topic/1733-shear-and-torsional-failure/#comment-4628 Regards.

Dear Ahmed Waqar, Thanks for sharing. IMHO, whenever someone asks a question on the Forum, but later on reaches some good answer by himself or herself, it is always a good idea to share the answer at the Forum as well, for the benefit of other colleagues & users. Regards.

You may contact them at 051-928 0844, between 9 am and 12.30 pm, from Monday to Friday.

A structural engineer is urgently required at Rawalpindi, to assist a senior structural designer. The potential candidate should have at least two years experience of structural modelling on ETABS, SAP2000 and SAFE, with some good design office. Interested candidates may email their CVs along with details of relevant experience & minimum acceptable salary to me, at 'engruzair@yahoo.com'. Please include reference to 'SEFP Job Ad', in the email subject.

Assalam-o-Alaikum! Dear colleagues, International Building Code (IBC) 2015 edition is available online, and can be read and consulted Free of Cost, chapter by chapter, at the following link: http://codes.iccsafe.org/app/book/toc/2015/I-Codes/2015 IBC HTML/index.html Regards.

Aoa. Document & links at the following location, may help you gather your required information: https://www.google.com/search?q=hair+fiber+reinforced+concrete&ie=utf-8&oe=utf-8#q=health+and+safety+policy+on+dam+construction+site Regards.

I don't know how many of them are published in impact factor journals. However, You may find several research papers on hair fiber reinforced concrete here: https://www.google.com/search?q=hair+fiber+reinforced+concrete&ie=utf-8&oe=utf-8 Moreover, many of our universities have subscription to one or more of international organizations (like Elsevier, Springer, RILEM etc.) that publish impact factor journals. Faculty and students (both MS & PhD) of these universities can download required research papers free of charge, from the relevant web page, using university computers specially designated for this purpose. You should contact your university, to know about this facility and make use of it, in case it is available there. Regards.

I do the connections manually, using custom made Excel worksheets. However, I use ETABS for main frame analysis & design. You may develop steel connection design worksheets in MS Excel, a very powerful spreadsheet software, yet not very difficult for developing structural worksheets for routine design office work.

Seismic detailing of beams requires the placement of shear reinforcement at a closer spacing within a length, equal to twice the beam height, from the support face. This is close to span/4 of the beam in many practical cases. Dividing the beam in 4 segments will give you 12 shear reinforcement values in total, with 3 values for each beam segment. Without dividing the beam into segment, you are getting only 3 values for the 18 ft span beam. With 12 values, you can more easily calculate stirrup spacing by adopting a suitable value applicable to each beam segment. Thus, it would be a lot more easy to detail the stirrups, as compared with the present situation of a single beam without segments or subdivision. HTH Regards.

1. In the following explanation, I am referring to ETABS version 9.7.4, with active units of 'kip-in' for all quantities. You are probably using ETABS 13 or later version. In these later ETABS versions, systems of adoptable units have been improved, and new options of units have also been implemented. However, in order to understand the explanation given in the following, you will need to change active system of units your model to 'kip-in' for all quantities. Otherwise you might miss some important point. 2. In case of beams supported at both ends, shear force (& accordingly, shear reinforcement) is more near the beam ends, as compared to middle portion of the beam. For these beams, ETABS indicates shear reinforcement at 3 points along the beam _ at the start, at the middle and at the other end of beam span. If the beam is not subdivided into smaller parts, shear reinforcement value would generally be larger at both ends, as compared to that for the middle portion of the beam.(Beam in your attached image is indicating the similar results.) 3. Calculation of required stirrup spacing is similar, to that described for the ties in case of columns in my earlier post. 4. Upto which distance, what stirrup spacing is to be provided depends upon the shear force distribution along the beam, as will be clear from shear force diagram for the controlling load combination. This spacing will however subject to relevant provisions of ACI 318-08 Chapter 21, depending upon the earthquake zone or design category of the area in which your structure is located. 5. Now referring to the beam shown in your attached image, the value shown in the middle (0.1000), indicates maximum required shear reinforcement applicable to middle portion of the beam, whereas the other two values (0.1521 & 0.1351) are the maximum required shear reinforcement, to be placed at the relevant beam portions adjacent to supports (columns) on the relevant ends. In case your lengths in 'inches', and shear reinforcement in in 'sq.in/in.' units, you may calculate required stirrup spacing, similar to column tie spacing discussed earlier, keeping in view relevant ACI requirements. 6. For exact detailing of the 18 ft span referred beam, following further information is required: a. Overall Beam size (width & height) b. Image showing required shear reinforcement values, after changing the active units to 'kip-in' for all the structural parameters, similar to ETABS 9. It would be better & simplify the detailing a lot, if the beam is subdivided into 4-equal parts, before analysis. c. Earthquake zone or seismic design category of the area in which the structure is located. c. Structural frame system used (OMRF, IMRF, SMRF, etc.) d. Minimum reinforcing bar size used for flexural reinforcement of this beam e. Preferable bar size for stirrups (Normally #3, or #4 bars are used). Regards.

A tragic incident. Reminds of the partial collapse of Sher Shah Bridge Karachi in the year 2007.

Not at all. Only cross-sectional area of stirrup bar, and actual number of stirrup legs (1, 2, or 4) used, are required.

This may be true only when the truss members are pin-jointed, and assumed so in the analysis. This assumption is historical and is basically adopted to simplify the analysis, most probably to carry out manual calculations. A more complex analysis will be required where the truss joints are rigid and impose significant bending loads upon the truss elements, as in a Vierendeel truss. You might like to see the following link, in this connection: https://en.wikipedia.org/wiki/Truss_bridge Regards.

Yes, your friend is right. It is preferable to use a beam width, about 6 inch larger than the column. It permits easy placement of column and strap beam bars at the junction of the two structural members, without interference. This extra width of strap beam also serves as a support for the column form work later on. Strap beam is also designed like other beams. For proper transfer of loads, its width however should not be less than the width of columns to which it is connected.

If the resultant column reinforcement is equal to the minimum reinforcement, as required by the applicable design code, one possibility is that you might have erroneously assigned 'supports' condition to all the beam-column joints, instead of the joints at base/foundation level only.

You need to check your design, using manual calculation to verify the results produced by the staad foundation. See the following thread for a few references for the manual calculations: http://www.sepakistan.com/topic/1978-strap-footing-design/ Regards.