RCC Beam and Structure Design Steps

RCC Beam and Structure Design Steps

Before beginning the Bidding and Construction phases of any project, i.e. in the pre-bidding phase, the viability of the project is checked by preparing Conceptual design data, drawings, and a preliminary estimate, which is then passed through various administrative and technical authorities to review the financial and technical aspects of the project and give the project the "go-ahead" signal.

Following approval, the first item that is done is a detailed design of all the components of that project, as this will allow the development of a Detailed Estimate, which will inform the owner of the project's actual cost.

As a result, the Design phase is a key step in project execution, as it drives project execution and final project delivery.

In this post, I'll attempt to explain the approach for designing an RCC beam in sequential steps using the limit State method of design, as this is the most frequent, easy-to-grasp, and accurate design used in practically all structural parts.

RCC Beam Design Steps

The design steps for the RCC beam are as follows:

Step 1: Calculate the intensity of the load projected to act on the beam in the first stage. This can be calculated by summing the slab's transferable loads and the beam's self-weight from the slab to the beam. Determine the clear span of the beam to be designed using the drawings provided.

Step 2: Next, determine the effective span of the beam. In the case of a simply supported beam, the effective span should be the lesser of the two values-

Effective depth plus clear span.The support's centre-to-centre distance.

In the case of a Cantilever Beam, the clear span (overhang part) is commonly regarded as the effective span for design purposes. Determine the bending moment and shear force from the loads obtained in step 1 after determining the effective span of the beam.

Step 3: Determine the trial dimensions of the beam in this stage. The trial depth for a simply supported beam is l/12 to l/15, where l is the effective span of the beam. The width of the beam is half the depth of the beam.

Step 4: Carry out the Depth check. The depth check equations, which may be found in any Design book, provide the minimum needed depth of that beam. The specified depth should always be equal to or greater than the obtained minimum depth. If this is not the case, the section should be redone with different span-to-depth ratios.

Step 5: Determine the quantity of reinforcement needed. Because the designed section should be under-reinforced, the equations required for under-reinforced sections should be used. After entering the needed values into the equations, a quadratic equation will be produced, which, when solved, will provide the amount of reinforcement used based on the bending moment and beam size.

After determining the quantity of reinforcement beam applied, it is compared to the minimum reinforcement required for the segment. It is also compared to the maximum amount of reinforcement that should be employed, which is typically 4% of the total cross-sectional area of the beam. If it passes these two tests, the section should be redesigned.

Step 6:Calculate the cross-sectional area of a single steel bar that will be provided in the beam based on its diameter in the following step. The number of bars necessary for bending can be simply determined by dividing the reinforcement employed in the previous stage by the cross-sectional area of a single bar.

The bending design is finished.

Step 7: The shear design process begins. Determine the nominal shear stress and allowed shear strength based on the dimensions and the percentage of tensile reinforcement at the start of this stage. Shear reinforcement is required if the nominal shear strength exceeds the allowable shear stress. It is also confirmed that the nominal shear stress does not exceed the maximum shear strength, or the section is modified.

Step 8: The spacing of shear reinforcement is determined using shear reinforcement formulas. The obtained spacing should not exceed—

0.75d, where "d" is the section depth of 300mm.

It is also compared to the specified minimum gap.

Step 9: The serviceability inspection has been completed. Assessment for deflection and cracking as part of the serviceability check. The above formulae are also used to calculate the development length.

Stage 10: This is the final step in the Complete Design process, and it includes extensive design data and a cross-section of the beam displaying the reinforcing detailing.

 These are the steps involved in beam design (Simply supported and Cantilever). The steps may be memorized by practising; thus, the more you practice, the clearer the procedure becomes to the reader. The design of a beam is an essential aspect of the Civil Engineering Course curriculum and the industry, where a designer must be very efficient and well-versed in all techniques and methods of design.

Table 2: Maximum Number of Bars in a Single Layer in Beam Stems with a Maximum Aggregate Size of 19 mm

Beam Width, mm	200	250	300	350	400	450	500	550	600	650	700	750
Bar Size	-	-	-	-	-	-	-	-	-	-	-	-
16	2	4	5	6	7	9	10	11	12	13	15	16
19	2	3	4	6	7	8	9	10	11	12	14	15
22	2	3	4	5	6	7	8	9	11	12	13	14
25	2	3	4	5	6	7	8	9	10	11	12	13
29	2	3	3	4	5	6	7	8	9	9	10	11
32	1	2	3	4	5	5	6	7	8	8	9	10
36	1	2	3	3	4	5	6	6	7	8	8	9
43	1	2	2	3	3	4	5	5	6	6	7	7
57	1	1	2	2	3	3	3	4	4	5	5	6

Tabl-3: Maximum Number of Bars as a Single Layer in Stems of Beams for Maximum Aggregate Size of 25 mm

Beam Width, mm	200	250	300	350	400	450	500	550	600	650	700	750
Bar Size	-	-	-	-	-	-	-	-	-	-	-	-
16	2	3	4	5	6	7	8	9	10	11	12	13
19	2	3	4	5	6	7	8	9	10	11	11	12
22	2	3	4	5	5	6	7	8	9	10	11	12
25	2	3	3	4	5	6	7	8	8	9	10	11
29	2	2	3	4	5	6	6	7	8	9	10	10
32	1	2	3	4	4	5	6	7	8	8	9	10
36	1	2	3	3	4	5	6	6	7	8	8	9