Mendesain Tulangan Geser menurut SNI 2847 2019

Summary

This video explains the process of calculating shear reinforcement for beams according to the SNI 2847:2019 standard. The speaker details the classification of zones based on shear stress, ranging from Zone 1 (no shear reinforcement) to Zone 5 (requiring larger sections). Step-by-step, the video covers how to compute shear capacities, determine the necessary reinforcement based on beam dimensions and loading conditions, and calculate the required shear reinforcement (Sengkang). Examples are provided to illustrate the calculations and final reinforcement placement for both support and span regions of the beam.

Takeaways

• 😀 The shear reinforcement design in the SNI 2847:2019 standard involves dividing the beam into different zones based on the shear force (Pu) values.
• 😀 The shear zones are categorized as Zone 1 (no shear reinforcement), Zone 2 (minimum shear reinforcement), Zone 3 (reinforcement required based on specific calculations), Zone 4 (shear reinforcement requirements based on VC + 0.33), and Zone 5 (significant reinforcement required if Pu exceeds a certain value).
• 😀 In Zone 1, no shear reinforcement is needed if Pu is less than half of PVC, while Zone 2 requires minimum shear reinforcement when Pu is between half PVC and smaller than VVC.
• 😀 Zone 3 requires more detailed calculations, where Pu exceeds VVC but is less than V × VC + 0.33. Zone 4 and Zone 5 have further calculations for reinforcement based on maximum allowable shear.
• 😀 For the example case of a 400 x 600 mm beam with a 5 m length, the first step involves identifying the shear force (Pu) in the beam, with Pu values of 350 kN at the support and 300 kN at the span.
• 😀 The second step is to calculate VC (shear capacity of concrete), using formulas for different conditions to determine the minimum value. In this case, VC = 182.92 kN.
• 😀 The maximum shear capacity (VC max) is calculated using the formula VC + 0.66 × D, yielding a result of 710.34 kN, which is then compared to the applied Pu value for confirmation.
• 😀 Step three involves checking whether the beam can resist the applied shear force using a comparison of Pu to V × VC max, which ensures the design is safe and adequate.
• 😀 The fourth step focuses on determining the shear zone for Pu by comparing it against thresholds like PVC, VVC, and other critical limits to find the correct zone for reinforcement.
• 😀 Step five is about calculating the shear reinforcement required, based on the shear forces, distances between stirrups, and cross-sectional properties of the beam, resulting in the need for specific stirrup spacing and diameter to ensure safety.

Q & A

What is the key difference between the new shear reinforcement calculation method and the previous SNI method?

The key difference is that the new method divides the shear zones into five distinct categories, as opposed to the previous method, which only used three zones. These zones are based on the shear force and other parameters like the concrete's compressive strength.

What are the five shear zones described in the new SNI method?

The five shear zones are: Zone 1 (no shear reinforcement needed), Zone 2 (reinforcement is minimum), Zone 3 (shear reinforcement needed based on calculated values), Zone 4 (reinforcement required due to higher shear forces), and Zone 5 (where the section needs to be enlarged to accommodate shear forces).

How is the shear force categorized in the new method?

The shear force is categorized into five zones based on its magnitude, with Zone 1 indicating no reinforcement required, and Zones 3, 4, and 5 indicating progressively higher levels of shear reinforcement needed, depending on the shear force and other conditions.

How do you calculate the shear capacity of a section using the new SNI method?

The shear capacity is calculated by considering the concrete's shear strength (vc) and the maximum shear capacity (vc max). The calculation involves using specific formulas for each zone, taking into account the concrete's compressive strength, and multiplying by the effective depth (d) to determine the shear capacity.

What does the term 'V * vc + 0.33' refer to in the new SNI method?

'V * vc + 0.33' is a formula used to calculate the maximum shear capacity for certain zones. It helps determine if additional shear reinforcement is necessary based on the calculated shear force in the section.

How do you determine the shear zone for a particular point in the beam?

The shear zone is determined by calculating the shear force (Pu) at that point and comparing it with specific thresholds like half of the PVC, VVC, or other calculated limits. The zone is assigned based on which threshold the shear force falls into.

What is the significance of the 'Sengkang' reinforcement?

Sengkang reinforcement is the shear reinforcement used to resist shear forces in specific zones, especially in areas where the shear force exceeds the capacity of the concrete. It is typically used in Zones 3, 4, and 5, depending on the shear force and the calculated requirements.

Why is the spacing of shear reinforcement (S) smaller in the support regions compared to midspan?

The spacing of shear reinforcement is smaller in the support regions (closer to the column or joint) because shear forces are higher there. A tighter spacing helps better resist the increased shear forces, while in the midspan, the forces are lower, so the spacing can be larger.

What is the calculation for the required shear reinforcement area?

The required shear reinforcement area is calculated by determining the theoretical shear force the reinforcement must resist. This is based on the ultimate shear force (vs) and the shear capacity of the concrete (vc), and then using appropriate formulas to calculate the area of reinforcement needed.

How do you verify the adequacy of the shear reinforcement in the final design?

The adequacy of the shear reinforcement is verified by checking that the shear force (Pu) is smaller than the total shear capacity of the section, which includes the contribution from both the concrete (vc) and the shear reinforcement (vs). This is done by calculating the actual shear capacity and comparing it with the applied shear force.