Reinforcement Detailing of Beams from ETABS output

Detail design of beams in Etabs 2018.
The ETABS file for a G+4 building is provided. Run the analysis and design the RCC Moment ResistingFrame. The following challenge deals specifically with two continuous beams in the 1st floor.

1) 3 span continuous beam along grid A
2) 7 span continuous beam along grid 3

Address the following issues thereafter.
• Provide details of longitudinal and shear reinforcement for the two continuous beams. Sketch the beam elevation details or draft it using autocad software. A sample of how beam elevation details is prepared in consultancy firms is provided below. Participants can prepare it as per their preference:

• Calculate value of the maximum shear force in any one of the spans in the continuous beams, as per clause 6.3.3 (b) in IS 13920 – 2016. Also, confirm these values from shear force demand calculated by ETABS.Please note that if longitudinal reinforcement provided is more than required (as per ETABS results), the shear force demand will vary from what is provided by ETABS.

INTRODUCTION:

• Beams are horizontal structural members that are used to support the lateral load. The beams usually receives load from the floor slab, but, the load intensity to the beams include the loads from the walls, finishes and the self weight of the beam. So it is the first priority to calculate the load.
• After this the amount of reinforcement required, the cross-sectional area of a single steel bar, that is going to be provided in the beam as per their diameter, he number of the bars required for bending etc are found out.
• After these steps, we find out the nominal shear stress and permissible shear strength depending upon the dimensions, and the percentage of tensile reinforcement. If the nominal shear strength exceeds the permissible shear stress, shear reinforcement is to be designed.
• It is also verified that the nominal shear stress should not exceed the maximum shear strength, either the section is redesigned.
• Checks for deflection and cracking is done.
• And at last, the complete design process, the detailed design datas and cross-section of beam showing the reinforcement is provided.
• Developed elevations can elevate any drawn path on a plan view. This is particularly useful for elevating a facade that takes a very unique shape. Once the developed elevation is drawn, it will then be added to the list of elevations in the model.

AIM:

• To design Beam in ETABS software and to design the RCC Moment Resisting Frame
• To calculate the maximum shear force in any one of the spans in both the continuous beams as per Clause 6.3.3 (b) in IS 13920 – 2016.

PROCEDURE:

• First we have to open the challange 7 page and download the challenge.
• After downloading the Challenge open it

• Next we have to check the load combinations, as shown below.

• Next we have to start the beam design by selecting the 'Start Design/Check' option, as shown below.

• After the completion of the beam design, we need to select the 'Display Design Info' option, as shown below.

• After selecting the 'Display Design Info' option the new tab appears, In that we select the Longitudinal Reinforcing in the Design Output and click on the OK button, as shown below.

• Next the longitudinal reinforcement details will appear, as shown below.

• After providing the beam reinforcement details, we select the beam and right click on the beam then the new tab appears, as shown below.
• Next we need to click on the Details option in Concrete beam design tab, as shown below.

• Next the Shear details will be visible, as shown below.
• As per the clause 6.3.3 the design force is 232 kN.
• We got, Maximum Shear force = 174.11 kN.

• For continuous beams in the 1st floor-3 span continuous beam along Grid A

• 

• For continuous beams in the 1st floor-7 span continuous beam along Grid 3

• 2 bars of 32mm dia is provided at the top
• At the bottom also 2 bars of 32 mm dia is provided.
• In the middle of the beam (ie from the beams B63 to B70 to B73) in addition to 2 bars of 32mm dia bars, 1 bar of 25 mm is also provided at the top

Result:

• The reasons for failure of the middle span along grid A is mainly due to high shear stress, this can be avoided to an extreme by reducing the depth of the beam, which in turn reduces the requirement of stiffness. And the high shear stress can be also controled by changing the grade of concrete used.
• Maximum shear force obtained from ETABS software is 174.1134 KN