EngrUzair

Aoa. I agree with haro0n that this is a very nice topic. Thanks to waqar saleem for starting this important topic. IMHO, this sub-forum is a very good platform for the engineering students in several ways. For example, here they can discuss their structure related problems, learn practical aspects of civil & structural engineering and share their structural knowledge as well. This all is however not possible without active participation from seniors. I understand that the seniors, especially the experienced ones, might be very busy in their professional duties (experience in structural engineering means a lot of study as well as a lot of hard work). and they may not having much time to spare for this forum. Everybody who works in an office, organization or firm as a structural engineer, gathers experience by carrying out different types of design jobs. Therefore, he/she can and should share his/her experience at this forum, whenever a similar problem is discussed here. I however sincerely feel that all of us should give some time to this Forum, particularly 'students zone' sub-forum regularly, and share our experience and knowledge here. This would certainly help our student colleagues, in developing better ideas and learning more practical engineering knowledge, thereby making them better engineers. I will myself, insha-allah, try to visit this sub-forum as regularly as possible, and to share whatever experience and knowledge I have gathered, as and when it may be needed. @Abdul Razzaque, and @Musawer! It is my personal experience that it is very difficult to learn structural designing on your own, unless you have an actual job to do. Similar is the case of application of a structural software (e.g., ETABs, SAP2000, etc.) for practical design of structures. No doubt that you may learn the use of ETABS etc and get certificate for it as well. however, you cannot use it properly or efficiently, if you do not understand how various commands & options of ETABS relate to a real structure. At this forum, strictly IMHO, it is not possible for any one to teach you structural engineering, or modeling with ETABS etc, from scratch. The best possible way therefore should be that you should look around you and find some experienced structural engineer, whether working on his own or for some organization or firm. Start working for him, even if you have to work without any financial benefits, and ask him to give you some actual job for designing. Once you get some real design job, you may use your engineering knowledge, and ETABS as well (if it is frame type structure) to perform the structural designing. You may discuss the practical aspects of your assigned job in this forum (in addition to asking your structural engineer boss), should you have some queries or need some help in performing its design. In this way, you are more likely to learn structural designing as well as practical use of structural software (ETABS etc). WORD OF CAUTION: Always remember that no software (ETABS or else) is a structural engineer. It is just a better quality calculator, that can help the structural engineer analyze and design structural frames comparatively quickly and reliably, provided you understand the capabilities & limitations of the software very well, and can apply them to your structural problem correctly.

Your required documents can be viewed online using following links, provided you are registered with ACI. otherwise only abstracts are available. http://www.concrete.org/Publications/MCPOnline/MCPSearch.aspx?m=abstract&MCP_DocID=029 http://www.concrete.org/Publications/MCPOnline/MCPSearch.aspx?m=abstract&MCP_DocID=978 Alternately, these documents may be purchased on ACI website (http://www.concrete.org/Store.aspx)

Sohaib! I have just seen your profile, and visited your website as well. I am very impressed from the information and data you have collected on your webpage. Well done, and keep it up. I am however surprised to note that you are absent from this forum for a long time. In my personal opinion, this is a very good forum for pakistani structural engineers, for both learning and sharing of structural knowledge. Therefore, I strongly recommend that you should keep visiting this forum from time to time, and share your knowledge as well.

Aoa. @baz! Bundle of thanks for contributing such a nice article, full of practical knowledge.

Aoa. Thanks for you responses. @Umar! I haven't read about the second approach in the literature I have gone through so far. However, I have heard some people talking about this approach. @baz! Thanks for apprising about third approach. Although I have seen many soil investigation reports, I haven't came across this type of approach yet..

Aoa. While designing foundations for building and other structures, allowable bearing capacity is used to calculate required area (spread) of footing. There are two approaches of structural engineers, regarding value of allowable bearing capacity, actually to be used. First approach says that the weights of soil below ground level and the footing concrete must be deducted from the allowable bearing capacity value given in the soil investigation report, to determine net bearing capacity. This net bearing capacity is to be used to be used for calculating footing area required to support the load from superstructure. The second approach, says that NO deduction is required for soil and concrete below ground level, because: a. soil investigation is carried out while original soil over burden is in place, and only superstructure load is to be carried out by the foundation, b. Allowable bearing capacity given in the soil investigation report is very conservative, as it is commonly calculated by employing a factor of safety of 2.5 to 3. The first approach results in comparatively larger footing sizes. The question is, which of the above two approaches should be followed? And, why (code or some other references)?

Aoa. What do you think, should be the qualification of a person, authorized to carry out soil investigation, and to provide allowable soil bearing pressures for the design of foundations? Whether he/she should be a civil / geotechnical engineer, or a normal geologist having no engineering degree? Reference to relevant rule or code, if any?

Design codes have built-in provisions for ensuring ductile design of flexural members, i.e., beams. Prior to 2002, ACI 318 did it by defining balanced and maximum steel ratios (rho-b and rho-max) for the tensile reinforcement. Rho-b is the steel reinforcement ratio at which both steel and concrete reach their ultimate load carrying capacity simultaneously. In case provided steel ratio is MORE than rho-b, beam failure will be through failure of concrete in compression (non-ductile design). On the other hand, reinforcement ratio LESS than rho-b, will result in failure of beam through yielding of reinforcement (Ductile design). To make sure that the beam design is always DUCTILE, ACI 318 Section 10.3.3 (1999 and earlier editions)) limited maximum tensile reinforcement ratio for flexural members (beams) to be NOT BE MORE than 75% of the balanced steel ratio, rho-b. In later editions of ACI 318 (2002 to 2011), ductile design of flexural members is being ensured by defining limiting tensile strain for flexural members. Relevant requirements are described and explained in ACI Sections 10.3 and R10.3 respectively.

As a glass wall is expected in future, I would try to make sure that the deflection is minimum. Since it is steel structure, self weight will also be less. For that I may go for deflection limit of L/360. As far as applicable live load is concerned, it depends upon whether it will be subjected to maintenance workers load or not. In case it will (or possibly may be any time in future), I will recommend a roof live load of 20 psf, reduced as per ASCE 7 Section 4.9. Otherwise, non-reduceable live load, mentioned in ASCE 7 Table 4-1 for fabric structures, should be applicable. Additionally, you will certainly be checking for wind effects on the structure for the situations with and without glass wall. You may also need to check topographic wind effects, in case the structure is not located in a plain area. In addition, requirements of IBC section 1604.3.5 might also be applicable in your case.

Would the seniors like to share their views on the subject?

How can we model masonry infill walls with RC frame in ETABS? What is its effect on overall design of structure?

If you know how to design a box culvert manually, you can probably make your own spread sheet as well. Otherwise, you can search the internet, to find a box culvert program appropriate for your needs.

Bridge design is a very vast subject. You will need a bridge design book (and relevant bridge design code as well) to learn how the bridges are designed. One such book is "Design of Highway Bridges, An LRFD Approach" written by Barker and Puckett. It is based on AASHTO bridge design code. Alternately, you may search the internet for Bridge design tutorials and examples, to start with.

Thanks for a good informative article on torsional aspects of RC members. However, it is suggested that references to relevant codes or documents should be complete, for easy following of information and checking back the original reference for further study. For example, it took me a while to figure out which edition was being referred to, since the year of ACI 318 being referred was missing. Accordingly, a little addition of references. The above article refers generally to section 11.6 of 2005 edition of ACI 318 (ACI 318-05). In 2008 and 2011 editions (ACI 318-08 and ACI318-11), however the relevant information has been moved to section 11.5. The quote portion, in new codes, is in section R11.5.1, and the new figure numbers are Fig. R11.5.2.1 and R11.5.2.2 respectively.

Waqar sahib! Can you give some practical example, how a "conservative" design snow load value can be selected for a particular city? What should be the design snow loads for Quetta and Murree? IMHO, as structural engineers, we are responsible to design safe and economical structures. Using unlikely heavy loads, will result in larger structural members or more reinforcement, thereby making the structure uneconomical. As such, selected loads should be very realistic. In this purview, I am interested to know how the other structural engineers are selecting snow load values for various hilly areas of Pakistan? I think, seniors should share their experience here to tell us about what snow load values they have used for their designs?, and what criteria they adopted to determine the selected snow load value? This sharing of knowledge would certainly help the younger engineers to decide at least about selection of reasonable design snow loads, in absence of standard or code-recommended values.

Our construction workers are generally ignorant of structural requirements. Moreover, they are commonly paid on per job basis, rather than per day basis. As such, they are most probably guided by ways or procedures which may help the job complete in lesser time. Placing the bottom hooks of column vertical bars to the outer side (opposite to what is required by ACI 21.12.2.2), makes the column reinforcement assembly more stable WITHOUT many lateral supports, as compared to the situation when the bends are turned inwards. This might be the reason why the construction workers keep the column bends outwards in our country commonly.

Thanks for providing an interesting and practice-oriented article. I hope you will update the material very soon.

Thanks for contributing such an informative article.

waqar sahib! Chapter 5 Division II of Building Code of Pakistan (Seismic Provisions-2007) provides the following information only: 1. Which load combinations are to be used for snow load. 2. How the snow load reduction factor can be calculated. It however DOES NOT tell us recommended values of snow load (in psf or kN/m^2 etc) to be used for the design of building roofs in various areas of Pakistan. Snow does not fall in all areas of Pakistan. Moreover, snowfall intensity is not the same in different hilly area. For example, Murree receives much more snow, as compared to Quetta. As such, design snow load for these two cities will certainly be different. I am interested to know where can I find design snow load values, applicable for structural design of building roofs located in Murree, Quetta and other hilly areas of Pakistan.

@waqar saleem: Yes, softcopy is available at following location: http://www.pec.org.pk/buildingcode.aspx @Ghulam Abbas Gazer: Thanks for the link. However, the copy available at PEC link, mentioned above, is not only in a much better form, but has more number of pages as well.

waqar sahib! 1. Are you referring to Building Code of Pakistan (Seismic Provisions-2007)? Which section? 2. Is it available in printed form? If yes, where from? (address, contact number?)

ASCE 7 provides ground snow loads values for the design of structures, located in various parts of the USA. Where we can find snow load data related to various regions of Pakistan?

Weight of a material is related to the its mass through the relation W = m g --------- (1) Dividing both sides of above equation (1) by 'g' , the relation changes to m = W/g --------- (2) where W is the weight of the material m is mass of the material g is the acceleration due to gravity Equation (2) gives the mass of a material in terms of weight of the material. Simply speaking, mass of of a material is obtained by dividing its the weight by g (acceleration due to gravity). This relation holds good even if 'weight' is replaced by "weight per unit volume", AND, the 'mass' by "mass per unit volume". You have to use consistent units in above equations. Now coming to your question; 'Analysis Property Data' is related to the properties of the structural material you are using for the frame elements (beams, columns, etc). For example, if you are modeling your structure as a Concrete Frame, 'Analysis Property Data' is related to the structural properties of Reinforce Concrete (denoted by "CONC", in ETABS). In this case, using "lb-ft" units in ETABS, 'weight per unit volume' value should be about 150 lb/ft^3 (= normally used unit weight or density of reinforced concrete), with "mass per unit volume' being 150/g = 150 /32.2 = 4.658. (32.2 is the value of 'g' when the unit weight is in 'lb-ft' units). Select the Units of your choice in ETABS, that you normally use in manual calculations, and then observe the corresponding value of 'weight per unit volume' for reinforced concrete (CONC) and structural Steel (STEEL) in 'Analysis Property Data' . Keeping above discussion in view, and the values indicated by ETABS should hopefully make you clear regarding wherefrom these numbers have come.

Which design code should we use for the design of steel structures in Pakistan? Which authority, law or rule directs to use this code?

Which design code should we use for the design of reinforced concrete structures in Pakistan? Which authority, law or rule directs to use this code?