How to Read Reinforced Concrete Drawings for Beginners

Summary

This lesson delves into reading reinforced concrete structural drawings for a residential project. The instructor emphasizes identifying load-bearing elements and understanding slab profiles from the General Arrangement plan. Key concepts include recognizing different wall types, interpreting slab steps, and analyzing reinforcement plans. The session also covers reading sections to confirm design intent, identifying integrity reinforcement for column support, and noting reinforcement details like bar placement and splicing. The instructor encourages practice by providing a PDF for further study.

Takeaways

• 🏢 The lesson focuses on understanding a residential project's reinforced concrete structural drawing, following a previous lesson on a commercial project.
• 📐 The first plan analyzed is the Level One General Arrangement plan, which is similar to the 'slab profile plan' from previous lessons, with different names but the same details.
• 🔍 Identifying loadbearing elements like columns and walls is crucial, and a legend on the drawing helps to distinguish between loadbearing and non-loadbearing walls.
• 📚 Understanding the slab outline and the depth of the concrete sections is key to interpreting the structural intent of the design.
• 📉 The use of hatches and lines in the drawing indicates different structural elements, such as loadbearing walls and slab steps.
• 🔬 Sections are essential for confirming the design intent, especially when the plan view is not clear, with examples given like Section 1.8 and Section 1.1.
• 🌿 The script mentions planter walls (PW), which are part of the structural design, likely for balconies or outdoor spaces.
• 📈 The bottom reinforcement plan is more complex with more lines, indicating the placement and spacing of reinforcement bars.
• 🔗 Integrity reinforcement is highlighted as crucial for structural stability, especially around columns to prevent progressive collapse.
• 🔄 The top reinforcement plan shows different splice locations and stepping at wet areas, indicating adaptability in reinforcement design based on structural needs.
• 🔍 Corners typically have trimmer bars, indicated by tags with the letter 'X', which are important for structural integrity at edges.

Q & A

What is the primary focus of the lesson described in the transcript?

The primary focus of the lesson is to go through an example of a reinforced concrete structural drawing for a residential project, explaining the details and interpretation of the drawing.

What is the first step in analyzing the level one General Arrangement plan?

The first step in analyzing the level one General Arrangement plan is to familiarize yourself with the load-bearing elements, identifying which members are supporting the slab and which members are loading the slab.

What does the legend on the top left-hand corner of the drawing page indicate?

The legend on the top left-hand corner of the page indicates hatches that represent load-bearing columns and walls under or over, as well as non-load bearing walls.

How can you determine if a wall continues to the level above or stops under the slab?

You can determine this by looking at the hatching on the drawing. A wall that continues to the level above is indicated by parallel lines, while a wall that stops under the slab does not have the parallel lines hatch.

What is indicated by a dashed line running along the inner face of the wall?

The dashed line running along the inner face of the wall indicates a step in the slab, where the slab depth changes. This step is typically represented by a dashed line because it cannot be seen from above.

How is a step in the slab typically represented on a plan?

A step in the slab is typically represented by a dashed line on the plan. This dashed line indicates a change in the slab's depth that is not visible from above.

What does section 1.1 reveal about the structural design?

Section 1.1 reveals that there is a 230 mm thick slab with a step down to a 400 mm deep beam in between the walls. This section also shows that there are PW walls, indicating an outside balcony with a planter box.

What should be done before looking at the detailed sections of the drawing?

Before looking at the detailed sections of the drawing, you should first try to understand the plan and roughly draw the section yourself. Then, you can compare your drawing to the section detail to confirm your understanding.

What is the purpose of the 'Integrity reinforcement' mentioned in the lesson?

The purpose of the 'Integrity reinforcement' is to prevent progressive collapse. These reinforcement bars are extra bottom bars placed in specific locations, such as under columns, to ensure structural integrity.

How should the top reinforcement at the edge of the slab be installed?

The top reinforcement at the edge of the slab should be cogged, meaning that the bars are bent down at the edges to provide additional structural support and to ensure that the reinforcement is anchored properly.

Outlines

00:00

🏗️ Structural Drawing Analysis: Residential Project

This paragraph introduces a lesson on reinforced concrete structural drawings, focusing on a residential project. The instructor emphasizes the importance of identifying loadbearing elements such as columns and walls from the General Arrangement plan. A legend is used to distinguish between loadbearing and non-loadbearing walls. The slab outline and depth variations are explained, including a 400 MM deep section and a 230 MM deep section, with steps indicated by dashed lines. The lesson encourages cross-referencing with section drawings for clarity.

05:00

📐 Understanding Slab Steps and Reinforcement

The second paragraph delves into the specifics of slab steps and reinforcement in structural drawings. It explains how to interpret the slab's thickness changes and the presence of planter walls (PW). The instructor guides the learner through understanding the reinforcement plans, including the sequence of bar placement and the importance of integrity reinforcement for columns. The paragraph also covers how to identify and interpret the bottom reinforcement layout, including the use of closed ties and the stepping of reinforcement at slab steps.

10:04

🔍 Reinforcement Plan Details and Inspection Tips

The final paragraph provides a detailed look at the top reinforcement plan, highlighting the differences in splice locations compared to the bottom reinforcement. It discusses the importance of reinforcement stepping down in wet areas, such as bathrooms, and the necessity of cogged reinforcement at slab edges. The paragraph also mentions extra bars for negative bending moments at supports and the presence of trimmer bars at corners. The instructor advises learners to download the PDF for further study and to apply the knowledge during structural inspections.

Keywords

💡Reinforced Concrete Structural Drawing

A reinforced concrete structural drawing is a technical representation of the design and construction of concrete elements that are reinforced with steel bars or mesh to improve strength. In the video, the drawing serves as the primary reference for analyzing structural elements in both commercial and residential projects. It includes detailed information on load-bearing elements, slab profiles, reinforcement plans, and more.

💡Loadbearing Elements

Loadbearing elements are components of a structure that support the weight and forces acting on it, such as walls, columns, and beams. In the video, understanding these elements is crucial for identifying which parts of the structure support the slabs and other components, ensuring the integrity of the building.

💡Slab Profile Plan

A slab profile plan, also referred to as the General Arrangement plan, details the layout, thickness, and support structure of the concrete slab in a building. The video highlights how to read and interpret these plans, emphasizing the importance of recognizing slab outlines, steps, and associated loadbearing elements.

💡Legend

The legend in a structural drawing explains the symbols, hatches, and lines used to represent different elements like loadbearing columns, walls, and non-loadbearing structures. The video suggests referring to the legend as the first step in understanding the drawing, as it helps identify key components quickly.

💡Section View

A section view is a cross-sectional representation of a structure, showing details of its internal components at a specific location. In the video, the instructor refers to section views to clarify the designer's intent and to ensure a complete understanding of the structural elements, such as slab thickness and beam depth.

💡Reinforcement Plan

The reinforcement plan shows the placement, size, and spacing of steel bars within a concrete structure. In the video, these plans are essential for understanding how to properly reinforce slabs and beams to prevent structural failures, such as progressive collapse, and to accommodate the design's load requirements.

💡Suit Step

A suit step refers to a step or change in the thickness of a slab, often represented by a dashed line in structural drawings. The video discusses how to identify and interpret these steps in the drawings, emphasizing their significance in understanding the slab's structural behavior.

💡Integrity Reinforcement

Integrity reinforcement involves the use of additional steel bars in critical areas, such as around columns, to prevent progressive collapse in case of localized failures. The video explains how these reinforcements are identified and their role in maintaining the overall structural integrity.

💡Splice

A splice is the overlap of two reinforcement bars to ensure continuity in areas where a single bar cannot span the entire length. In the video, the placement of splices in both top and bottom reinforcement plans is discussed, showing how they are positioned based on bending moments and structural requirements.

💡Trimmer Bars

Trimmer bars are additional reinforcement bars placed at corners or edges of slabs to provide extra support and stability. The video highlights their importance in reinforcing vulnerable areas, ensuring that the structure can handle loads and stresses at these critical points.

Highlights

Introduction to the lesson focusing on a reinforced concrete structural drawing for a residential project.

Explanation of the importance of identifying loadbearing elements in the General Arrangement plan.

Discussion on how to interpret hatches and dashed lines indicating loadbearing columns, walls, and slab outlines.

Clarification on reading the slab profile plan, emphasizing the difference between loadbearing walls under and walls over the slab.

Introduction to the concept of a slab step and how it is represented by a dashed line in the drawing.

Detailed walkthrough of Section 1.8 to confirm the interpretation of slab thickness and step details.

Analysis of Section 1.1, explaining the identification of steps and slab transitions in the structural drawing.

Insight into interpreting the dashed lines and solid lines for understanding slab steps and actual steps on the top surface.

Explanation of the planter wall (PW) and its representation in the drawing, particularly in Section 1.1.

Overview of the reinforcement plan, focusing on the bottom reinforcement with N12 bars at 250 centers.

Introduction to Integrity Reinforcement and its role in preventing Progressive Collapse, as discussed in the previous lesson.

Explanation of the significance of reinforcement bars, including N16 and N20 bars, and how they are depicted in the drawing.

Walkthrough of Section 1.5 to understand the detailed reinforcement layout and the role of side face bars and closed legs.

Discussion on the top reinforcement plan, highlighting the differences in splice locations compared to the bottom reinforcement plan.

Explanation of the need for cogs at the ends of the reinforcement, particularly along the edges of the slab.

Transcripts

welcome to this next lesson where we

will go through an example of a

reinforced concrete structural drawing

the first example that we investigated

was a commercial project and now we will

look into a residential project I'll try

to make this lesson brief and I'm not

going to repeat myself because the

previous lesson was pretty pretty long

so you can always go back to the

previous lesson and rewatch it so the

first plan we will look into is the

level one General Arrangement

plan in the previous drawings we called

it slab profile plan they're just

different names but they convey the same

details first thing I would familiarize

myself with in the drawing is the

loadbearing elements you should be able

to identify what members are supporting

this lab and what members are loading

this lab there's a legend on the top

left hand corner of the page where you

can see the hatches that indicates

loadbearing columns and walls under or

over or non-load bearing walls and if

you're in doubt as I emphasized in the

previous lessons you can always have the

drawings aligned and move the page up

and down so you can identify columns and

walls below above and

continuous let's start from this upper

corner this hatch indicates load bearing

walls under and the parallel lines hatch

indicates wall over so this this wall

comes from the level below and continue

to the level above this wall stops under

this laab and I can tell that because it

doesn't have the parallel lines

hatch the solid thick line around the

perimeter is the slab outline and

there's a dashed Line running along the

inner face of the wall and it turns down

this way and between this slab outline

and the dashed line we have a section of

concrete 400 MM deep and on the inside

is it is 230 mm deep I'm sort of getting

the gist of the intent of the designer

but I'm still not 100% of what's

Happening Here okay so to be 100% sure

of what's Happening I'll look at the

sections provided so let's go to section

1.8 okay now it's very clear the intent

of the design we have a 230 thick slab

that steps down to a 400 MM bin in

between the walls remember last lesson I

told you that a step on the slab suit is

represented by a dashed line there we go

you have the suit line here and it steps

down at the inner face of the wall and

that's why you have a dashed Line

running along the face of the wall on

the pl so that makes sense this dash

line here that's the suit step to the

beam in in between the walls let's

understand what's going on at section

1.1 there's a 230 slab then there's the

dashed line which means there's a step

of the slab of fet and following that

there's a solid line with a step tag you

got a step here a step here which

indicates an actual step on the top

surface of the laab the dashed line is

dashed because if you stand on top of

the floor you can't see the suit step

and then there are two PW walls it looks

like to me that this is an outside

balcony with a planter box so PW is a

planter wall let's zoom into section 1.1

and see if we got it right okay so it

looks like exactly how we read the plan

there's a 230 slab then there's a step

on the suit which we cannot see from

above that's why it's represented by

dash line following that there is an

actual step and then the planter box

walls PW that's basically how we're

going to read these drawings okay let's

go through a couple of sections and then

we jump to the reinforcement plans let's

go to the other side on grade six and

seven section 1.7 shows me that there is

a 230 laab then there is a wall under

supporting this laab and also there is a

sop step because I can see a dash line

running along the inner face of the wall

it doesn't show any step tag so I'm

assuming there's no actual step on the

floor we simply increasing the thickness

of the laab from 2030 to 400 MM and

along the edge there is a 300 mm deep

Hub so let's go to section 1.7 and

confirm that let's zoom in on section

1.7 yep so 230 here the laab ofit steps

down at the load bearing wall and then

the slab increases to 400 MM and then

along the edge there is a 300 mm hob or

you can say a recess of 100

mm so that's basically what you're going

to do for this whole plan you can

download this PDF I'll leave the and

I'll leave the remaining sections as a

homework for you try to look at the plan

first and roughly draw the section

before you go to the section detail and

then you confirm what you have drawn the

next drawing is the bottom reinforcement

plan you can tell that this drawing has

way more lines than the previous one

which might make the reading slightly

more difficult but the principles will

not change there is a direction of bar

line which is the thicker line and the

extent line exactly like we saw in the

previous drawings let's go through an

example here this middle portion of the

laab has any 12s at 250 centers and this

direction in the bottom will be the

first to be placed because you have the

number one after the spacing and that

represents the lane sequence so you have

bars all the way up here so if I had to

draw you would have

bars like this space this way

250 and then when it gets to this line

they increase to spend between

walls so let's extend this bar goes all

the

way and that happens to the other side

as well you have

bars let's copy

this I supposed to

copy all the

way up here

and then when it gets to this side it

extends the B go all the way over the

walls and that's pretty much how you

will see on

site there is one n16 1.3 M long extra

bar with a hook and remember the

Integrity reinforcement that we

discussed in the previous lesson so we

have a column under and if you have a

column you might need those extra bottom

bars to prevent Progressive collapse and

these reinforcement bars are called

Integrity

reinforcement we have two N20 bottom

bars there's a letter a tag that tag

indicates n12 closed leags at 250

centers if we go to the section we can

understand better what's happening so

that is section

1.5 if we go to section 1.5 there is a 1

M deep Bane with two

N20 bars at the bottom and then you have

n12 at 200 side face bars and the closed

leags go up to the top reinforcement

this dash line is the suit step and as

we've seen before in the laab

arrangement plan if we are stepping the

bottom surface of this lab we also have

to step the bottom reinforcement so we

looking at reinforcement on this

direction

now they are any2 at 250 centers and

this is the second layer of

reinforcement the drafter plac the tags

outside the slab out line so that it

doesn't get too messy but you can see

you can see here the intersection point

between the extent line and and the

reinforcement line let's have a look at

the section to understand this better so

this is section this is section 1.4 so

if we zoom in at section

1.4 so the bottom reinforcement extends

past the suffit

step so let's go back there see what's

happening so you've got the bottom

reinforcement that goes past the suet

the the suet line okay that looks right

and the bottom rear of the balcony cogs

up and it's tied to the top

reinforcement so let's see if there's

anything else here so there's 5 n16 at

250 centers extra bars in this direction

so when you're doing your structure

inspection you should also be able to

see the 5 n16 extra boss somewhere

around

here okay let's go back back to the

plans typically at Corners you will have

trimmer bars and that's what those tags

with the letter X

indicate now let's move to level one top

reinforcement plan okay the first thing

I notice is that the splies are at

different locations from the bottom

reinforcement plan which makes sense due

to the peak bending moment so the in the

top reinforcement plan we have the spli

close to the to the middle span in

between walls and then if we go to the

bottom reinforcement you don't have a

splice here in the middle that's

something important for you to notice

you're also going to see the top

reinforcement stepping at the wet area

set down so this areas where the

reinforcement steps down they're

probably bathrooms so you have a recess

you have a a set down and that's the

reason you have to crank the

reinforcement down another detail that I

can see on this plan as well is that the

reinforcement should be cogged at the

ends so if you look at the edge of the

laab the reinforcement is always cogged

so you got a cog in all the edge you've

got a cog here you've got a cog down on

the edge here cogs down it cogs down it

cogs down so also Ure when you do your

inspection the reinforcement at the edge

of the slab is cogged that one M deep B

that we saw before now we can see the

top reinforcement which is 2 and 16 so

if we go to the

section those two bars here should be

n6s we saw in the bottom reinforcement

plan that we have two N20 bars now on

the top reinforcement plans we saw that

we we need to have two n6s at the top

what else can we tell we have some extra

n2s stepping up outside to the balcony

and they are 2.5 M long on the left hand

side some n12 extras at 500 centers

they're 2.5 M long as well and they're

running on top of the supports which

makes sense because you have a peck

negative bending moment at the supports

therefore you might need some extra bars

and what else and on the very end to the

right there are nine n2s at 200 100

centers extra bars 4 M long so that's

basically it fellas you can tell that

these drawings have much more

information for you to absorb this PDF

will be available for you so go through

the drawings yourself and if you have

any questions just comment below I'll

see you in the next lesson