Desain Pelat 2 Arah Beton Bertulang - Part 1 Konsep SNI 2847-2019

Summary

This video covers the design and analysis of two-way reinforced concrete slabs, including various types like beam-slab systems, flat plates, and waffle slabs. It explains how to determine slab thickness based on design codes and provides methods for calculating ultimate moments using moment coefficients. The video also delves into reinforcement detailing for different slab types and outlines how boundary conditions affect the design process. Aimed at civil engineering students and professionals, this tutorial provides essential knowledge for designing safe and effective two-way slabs in concrete structures.

Takeaways

• 😀 Two-way slabs are supported on all four sides and bend in both directions when loaded, requiring reinforcement in both directions.
• 😀 The **Beam-Slab System** is the most common type, where slabs are supported by beams on all sides.
• 😀 **Flat Plates** are used for lighter loads and shorter spans (up to 6 meters), supported directly by columns without beams.
• 😀 **Flat Slabs** include thickened areas around columns to resist shear failure and can have a capital (column enlargement) for additional strength.
• 😀 **Waffle Slabs** use voids to reduce weight while maintaining strength, typically used for large spans and heavy loads.
• 😀 Slab thickness is determined using guidelines from SNI 2847:2019, based on the slab type and conditions (e.g., flat plate, flat slab, or slab with beams).
• 😀 The minimum slab thickness for a **flat plate** without drop panels is 120 mm for internal panels, with 100 mm allowed for those with drop panels.
• 😀 When designing slabs with beams, the stiffness ratio between beams and slabs (Alfa FM) is important for selecting the appropriate design method.
• 😀 The **Moment Coefficient Method** is used to calculate ultimate moments in both directions (LX and LY) for two-way slabs, considering support conditions.
• 😀 Support conditions affect design calculations, with three types: simply supported, elastically restrained, and fully restrained.
• 😀 Proper reinforcement detailing ensures that the slab can resist the calculated bending moments, with specific rules for minimum reinforcement and spacing.

Q & A

What is a two-way slab and how does it differ from a one-way slab?

A two-way slab is a concrete slab supported on all four sides, where both directions of the slab (short and long spans) are responsible for carrying the load. In contrast, a one-way slab is supported on two opposite sides and primarily carries loads in one direction.

What are the common types of two-way slabs discussed in the video?

The common types of two-way slabs discussed include the Beam-Slab System, Flat Plate, Flat Slab (with drop panels and column heads), and Waffle Slab (with hollow spaces to reduce weight).

How is the thickness of a two-way slab determined?

The thickness of a two-way slab is determined based on its type and span. For flat slabs without drop panels, the thickness is referenced from SNI 2847-2019 tables, while for slabs with drop panels, the thickness can be reduced.

What is the significance of the 'Alfa FM' ratio in slab design?

The 'Alfa FM' ratio refers to the rigidity ratio between the beam and the slab. It helps determine the slab thickness and whether a more rigid or flexible design approach is needed. It is calculated using the ratio of the moment of inertia of the beam to the slab.

What are the differences between a 'simply supported' and 'fully fixed' slab?

A 'simply supported' slab is free to rotate at the support, whereas a 'fully fixed' slab is rigidly connected at the supports, preventing rotation and leading to different moment coefficients during design.

What is the role of drop panels in flat slabs?

Drop panels are used in flat slabs to reinforce the area around the column-slab connection, preventing shear failure and providing additional strength, especially for slabs with higher loads.

How do you calculate the ultimate moment for a two-way slab?

The ultimate moment for a two-way slab is calculated using a coefficient method, where a base formula is applied with coefficients based on the span lengths (LX and LY) and the slab's support conditions.

What are the different types of slab support conditions mentioned in the video?

The three types of slab support conditions are: simply supported (free rotation), elastically restrained (slightly flexible connections), and fully fixed (rigid connections that prevent rotation).

Why is it important to determine the slab thickness correctly in structural design?

Correctly determining slab thickness ensures the slab can carry the expected loads without failure. It also affects the amount of reinforcement needed, the overall weight of the structure, and the economy of the design.

How does the SNI 2847-2019 standard help in slab design?

SNI 2847-2019 provides detailed guidelines and tables for determining slab thickness and reinforcement requirements, ensuring safety and efficiency in concrete slab design. It also offers formulas and coefficients for calculating moments and forces.