WR1

100% agreed. Usually shearwall/floor area is ~ 1%

Dear Umair, I understand what you said, but, that is only one of the condition I asked about (see below). Ok let me put this in following way; lets call T-computed simply as T, there are following 4 cases; a. T < Ts < Ta b. T > Ts but < Ta c. T > Ta but < CuTa {not my concern} d. T > CuTa {not my concern} Now lets focus on condition a & b; Let's say; Ts=0.3s and Ta=0.7s Condition a Assume T=0.1s which is less than both Ts and Ta In order to jump to V, we need to first set the time period. a1. If we use Ts, then obviously maximum base shear would govern. This is what you are referring to. a2. if we use Ta (which is higher than Ts), base shear would be less than Max. V so we get some saving. Now the question is what T you'd use? Ts or Ta? As per FEMA (moment frame example) use Ta. As per research papers I have mentioned for tunnel construction you should use actual T (or in other words Ts as Max V would govern, as you rightly pointed out). Condition b Assume T=0.5s which is more than Ts but less than Ta. Still, if we go with FEMA approach, we should use Ta which will give us lesser base shear. And use of actual T would give us higher base shear. So the question remains, what value of T to be used? 0.1 x (no of floors) is for certain moment frame buildings as per ASCE 7-10 seismic design examples book (example 17), that might not be correct for buildings with large no/area of shear walls. Anyway, the intention, as i see, is to use approximate method (Ta) if analysis T is less than Ta, which is in-line with what Baz said. However, after going through the above research papers, I am again inclined towards using T from analysis instead of Ta for such buildings. For moment frames, yes we could use Ta.

I have another point, (Source: http://www.tdmd.org.tr/TR/Genel/pdf/TDMSK010.pdf) Lower bound and upper bound limits of regression analysis are given as in building codes. More exact solutions (such as in analytical models) give higher T than Ta due to absence of partition and infill walls etc. But my concern is for buildings having large shear walls areas such as tunnel construction, very very dynamically stiff (e.g. 0.1s). In such cases (T-computed < Ta) and as mentioned by following paper, we should not use Ta (as per discussion in posts above) and should use T-computed. Paper can be found here: http://erolkalkan.com/Pubs/12.pdf Also see this: http://www.sciencedirect.com/science/article/pii/S1687404815000565

Wow. But there is no clear reference for this in ubc or asce. I got the sense and could save some structures from over-design but would be very difficult to convince authorities without a clear overt, explicit reference to building codes.

No way Ilyas. That will reduce the total base shear. Wrong approach.

Do you mean "There is no need to use the value of time period that is LESS than Ta" or "NOT LESS than Ta"? As you quoted FEMA 451, it says Ta is lower-bound limit (more conservative for base-shear as T-computed would be higher) CuTa is the upper-bound limit (can be ignored for drift calculations) But, There is no guidance on if T-computed is less than Ta, not even in ETABS manuals. All the documents highlight the upper limit but not the lower one. For example, consider a bearing wall building, (density of walls/floor is large), T-computed is ~ 0.10s, however Ta=0.5s; huge difference. ETABS only checks the upper limit (lets say 1.0s) and not the lower one and selects 0.10 automatically and calculates base shear for this T. However, if I am getting you right or as per; 2009 NEHRP Recommended Seismic Provisions; Chapter 4, page-41, it says; if T-computed is less than Ta, then use Ta. https://www.fema.gov/media-library-data/1393888487069-c071850c3050c34da135376baa478a1b/P-752_Unit4.pdf Please shed some light on this issue.

Waqas, just reverse calculate; In books you will find for singly reinforced; a = Asfy/0.85f'cb and Phi Mn = 0.9Asfy(d-a/2) re-arrange, and you will find your answer.

As you said, according to R7.12.1.2, first of all, reduce the modulus of rupture by half i.e. from 0.62√f'c to 0.31√f'c. Second, increase the reinforcement as required for axial tension (T=phi As fy) in addition to what required for moment.

1. Increase modes from 12 to have SumRx more than 90%. 2. first mode is translation in x plus some torsion. second mode is pure translation y. third mode is torsional + x-translation. it appears that you have irregularities in x direction (CM and CR are at different locations).

Check in all 4 or 6 cases, then magnify in all 4 or 6 cases.

Dear rummaan17, Step 1: Include 5% eccentricity in X and Y cases (X+Eccen Y, X-Eccen Y, Y+Eccen X, Y-Eccen X). Total 4 cases. Step 2: Check if torsional irregularity exists. If yes then increase 5% values to the amplified values (7%, 8% whatever, There is upper limit too in the code). This increase of eccentricity would be different for each floor plate and can be manually entered into ETABS by using "override diaphragm eccentricities" option. You should do this for all the 4 cases. Now after doing this, if you torsional irregularity still exists, you don't need to further iterate. Only one time increase is sufficient.

1. P/A + My/I,xy If area req for isolated footing is so large that it combines with other footings, provide raft. 2. Soil report recommendations including uplift and water table, soil type, liquification etc.

Ground to roof.

Please see the attached image; Full pdf here: https://www.engineersaustralia.org.au/sites/default/files/detailing_of_reinforcement_in_concrete_structures_28_aug_2012.pdf

A beam is a flexural element with axial load less than 0.1Agf'c. So the main action is bending (bending stresses) and not the axial stresses. However, a column on the other hand is considered usually an axial member (compression or tension) carrying only axial stress (P/A) and this action is called column action. If however an element carries moment + axial forces, resulting stresses will be flexural + axial (My/I + P/A) and you come up with interaction diagram between P and M. On an interaction diagram, M is usually on X-Axis and P on Y-Axis. If the loading is such that axial force = 0 (point lies on X-axis, this is called beam action) and the opposite is called column action.

Read this: This is excerpt from FEMA 451 Part 2: Section 6.2.1.

I think the situation is different. In case 2 I highlighted in my post, killing 1 person situation is intertwined with saving 4. They depend on each other. While the case you are highlighting are separate events. Yes 4 people could be saved by donation of 1 person or by forcefully killing him making all the scene ethical but they are not altogether under one script, they are in different times and events.

first-off its a very rare/exaggerated example one would not face in his/her entire life...probability is nominal. in my personal view; 1. inaction is immoral plus its killing 5 people (although you are consciously doing an action inside your brain by not acting). Thats crime. 2. if you go by numbers, that is more logical to me, as it involves action + saving 4 + the intention to save lives. Intention also matters here that leads to act in a good way.

You are right, we lack in professionalism and justice because no matter how qualified one becomes in Pakistan, ethics are still left out due to absence of fear of judgement/punishment/morality.

Tip1: Being ambitious is good and appreciated. But dont go so deeper and end up having an unyielding tough topic making your life harder. Think big, start small. Okay? For topics in bachelors, let me direct to some; have you thought about these? My suggestion is to think of yourself as the 'future leader' of structural engineering...not just a technical number cruncher.... 1. Highlighting the ordinary house construction mistakes and tackling them? like putting more steel always isnt good in a beam, like snap-failure of concrete floors killing people in factories, mosques and homes in pakistan? A sort of guide for public? Could go on publishing in media as well afterwards. 2. Environment? Value engineering/whole life cost, structural engineering solutions in pakistan to protect environment from construction effects??? What are the shortcoming. 3. Rehab of ordinary public homes to protect for future earthquakes? 4. Study of moderately mid to high rise or complex shape buildings that are dynamically sensitive. For example you could consider an important national building (faisal mosque ?) whose shape is very sensitive to dynamic loading (wind/seismic) and how the design was done and what are the your suggestions to improve? or the lessons learnt for future buildings of same kind. 5. 3d printing, what are the effects and how and at what scale it could be implemented in pak and what type of sector can use it? can we make better and cheap and environmentally friendly homes from it? if not now then may be in future? 6. structural health monitoring? 7. Preparing tables for beams, slabs that shows economy vs span for ordinary construction in pk? Could be distributed as served as a guide in design offices. For example google 'concrete center' span tables. 8. Structures and Terrorists! How would you protect important buildings in Pakistan from terrorist threat? Evacuation plans and structural engineering, blast resistant, progressive collapse, what material is better? Implementation plan? What are more sensitive national buildings?

Reduce the stiffness of shear walls such that the base shear carried by columns is 25%.

No, as long as there is a lid on drifts and irregularities.

I am sorry for misunderstanding. Torsional irregularity information cannot be checked from the tables you provided above. What I meant was overall dynamic performance of the building looks okay from the numbers. However, I am glad, you found the solution.

Columns failing in shear? Thats very rare. Are you sure your models are correct?