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Dear senior brothers! I have one year experience as a site engineer and 5 months as a project coordinator.I am getting 38,000 rupees per month.But i have keen interest in design job from the very beginning.I may get one opportunity where i will get up-to 25,000 rupees per month.But experience there is good.So kindly suggest which alternative should i choose out of them???? I need your valuable suggestions and advice.... Thanks brother Regards, Rasheed

Waqas, First note that development length in indicated case is only the straight length as shown in figure and doesn't include bent portion and secondly this requirement can be fulfilled as follows, 1,you can use greater no of lesser dia bars complying ldh requirement and if beam width is insufficient to accommodate greater no of bars then you can distribute them in effective flange width (ACI 318-11 section 10.6.6). 2. you can multiply ldh by 0.8 if you tie hooked end reinforcing bar with ties parallel or perpendicular to the bar, spaced not greater than 2db (db = hooked bar diametre).(ACI 318-11 figure R12.5.3). 3, You can provide excessive reinforcement and multiply ldh by As req/As prov. 4, You can multiply ldh by 0.7 by maintaining minimum side cover to the longitudinal bar to 2.5".

Asad, It is not necessarily required to extend the seismic analysis's storey range till basement levels as for buildings with several below grade levels supported by basement walls, two stage static analysis procedure is used (ASCE 7-10 Section 12 & UBC97 section 1630.4.2) that consists in distribution of building in flexible upper portion (above basement levels) and rigid lower portion (basement levels), provided the lower portion have a stiffness minimum 10 times greater than upper and time period of whole structure should not exceed 1.1 times of flexible upper portion's period while it is considered as a separate structure. You can simply check these limitations as, 1, by computing stiffness ratio (EI/L ratios of basement walls + LFRS in rigid lower portion) to the (EI/L ratios of LFRS in flexible upper portion) 2, computing time period of whole structure (Eigen vector) and computing time period of upper portion alone modeled without basement levels. Having satisfied these, seismic analysis is required to be performed till base of upper portion only & rigid lower portion is required to design only for seismic forces transmitted at the base of flexible upper portion modified by the factor Rupper/Rlower. In ETABS you have to define "ground level" as bottom storey in analysis storey range and seismic shear imparted on ground level will be automatically transmitted to the levels below through diaphragm action.It will be just required to compute "R" value for lower portion considering it separate and to modify seismic load case's scale factor by Ru/Rl for the design of below grade structure. In this way the maximum seismic shear will be acting at the ground level not at B4, that will reduce the magnitude of force and could be beneficial in mentioned below grade serviceability issues particularly drift will be considerably reduced (also compute drift using user defined time period obtained from eigen vector analysis see UBC Section 1630.10.3). As long as below grade torsion is concerned, it is just required to satisfy that Ax (UBC97 Eqn 30-16) should not exceed 3 and required to be noted that amplification of diaphragm eccentricity is of no meaning there since seismic forces are imposed from upper portion and are not calculated & applied separately. Secondly, load combinations should be inclusive of minimum seismic vertical effects and dynamic load combinations.

It will require two plastic hinges to develop mechanism, as it act as propped beam, and it can still redistribute moment. You are not relying on plastic strength of the structure to carry gravity loads. If , in a particular frame, your reliability/redundancy factor is less than 1, excluding the bay which contains propped beam, and your drifts are under control, then you can use a propped beam in one bay of that frame. If you can afford a non-moment resisting bay, which means your drifts are under control and your structure has adequate redundancy, then you don't have to worry about integrity of that one joint. Other joints and bays of the frame can take care of that.

Slab on grade is a foundation type and the use of the term varies from region to region. I have seen them to be provided normally in Industrial Buildings as floors. They are designed for storage + machinery operating loads like fork lifter etc. Frost Heave is a concern for most slabs on grade. In Pakistan, I have seen some firms providing reinforced slab panels above grade and calling it Slab on Grade. That is a reinforced slab panel not slab on grade. To be classified as slab on grade, the slab panel should be acting as the sole foundation. Thats what I would say. Other may disagree.

here is an excerpt from on of my fav books on structural design, I read it some 3 years back, and it always reminds me how we structural engineers can exploit material properties to achieve robust designs.

Property modifiers in etabs are used to model cracked behaviour of concrete sections. They are only applied to concrete members because of cracking. Gross moment of inertia is bd^3/12 for a rectangular section, but when you make this member of concrete, it will experience cracking when loaded after some time. This cracking will happen when concrete reaches its tensile capacity which is about 7-10% of its compressive strength. Formula to calculate cracking moments are given in ACI. For example 3000psi will have only 300psi of tensile strength. Actually the reinforcement starts its work when concrete cracks because of tension. After cracking concrete is no longer able to carry tension so steel starts taking the tension. So now if concrete cracks after 300psi the moment of inertia will be reduced because of cracking. If moment of inertia is reduced, its stiffness is reduced, taking less moment, and its deflection increases because of less stiffness. This moment which the cracked beam is not taking anymore will be re distributed to other structural members based on their stiffness. If you read ACI chapter 10, there are many sets of modifiers used for different types of analysis. ok im leaving from office, if you have more doubts i will write in later.