Designing Buildings - User contributions [en]

Why and where to put rods on beams

2024-04-20T20:37:28Z

Ebhosworks: Created page with "Why and where to put rods on beams Reinforced concrete is the combination of two different structural materials which are concrete and steel to achieve a more durable strength f..."

Why and where to put rods on beams

Reinforced concrete is the combination of two different structural materials which are concrete and steel to achieve a more durable strength for both materials. Good concrete should be able to resist fire for a reasonable period, which means concrete is very good at resisting fire. Another good property of concrete is that it should be able to provide good compressive resistance when it is under load condition

Concrete has poor resistance to tensile stresses and they are not also very good at providing shear resistance when it is under load conditions. One unique property of concrete is that it is very durable, which means it can stand the test of time before it starts losing some or all of its other properties to deformation.

Unlike concrete steel is very good in tensile strength and also in compressive strength, the shear resistance and durability condition of any steel materials are very high, but one area steel lacks is the low resistance to fire.

To understand the concepts of reinforced concrete, one will need to learn from a practical angle, the properties of concrete, the properties of steel, and the best way to combine both materials to achieve what is called reinforced concrete. You know that concrete is very good in compressive strength, very good in the ability to resist fire, and fair in shear resistance but very durable Steel on the other hand is very good both in compressive and tensile strength and also good in shear resistance but does not have good fire resistance.

Having a practical knowledge of the behavior of structural members under load or force will help you understand how we can combine these materials in a way that will provide good structural strength to the member or beam.

For instance, if we have a beam under a point load, you will notice that the top area of the beam will try to compress and the bottom area will try to split apart or expand. what it means is that those areas that try to compress experience compressive stresses and those areas that try to split apart will be experiencing tensile stresses. once you can identify the area that is experiencing tensile stresses, all you need to do is to place reinforcement on those areas. the image below gives a graphical illustration of those areas with compressive and tensile stresses.

See the image below1

From the image above, practically when you apply or place a load on a simple supported member without reinforcement, you will notice that the member will be displaced downward a little causing the top area to experience compressive stresses and the bottom areas to experience tensile stresses.

To eliminate these stresses you will need to understand practically how the members behave under load conditions. those areas where you have the compressive stresses acting at the top of the member will need more concrete materials and less steel materials while those areas where you have the tensile stresses acting at the bottom will need more steel materials in addition to the concrete materials.

it becomes very easy to understand how and where you place your steel in a simple supported member when you are considering a reinforced concrete member.

Now at the bottom of the beam, you will need to place more numbers of rods since it is under tensional forces to help resist the stresses acting at the bottom, while at the upper area of the beam, you can place just the nominal bars at the top areas since the stresses there are compressive stresses and concrete in that area should be able to resist the stresses acting at the top areas.

The quality of concrete and the number of steels required to resist the compressive and tensile forces can be derived theoretically but the scope of this work is to have practical knowledge of why and where to place the steel bar on a simple supported member.

See the image below 2

For the case of a cantilever member or beam, considering the image above you will notice that once you apply a force or a load close to the end of the member, the end of the beam deflects downwards thereby causing compression at the bottom and tension at the top area. This experience gives you an idea of how to reinforce the member.

So for the case of a cantilever beam, since the top experiences tensional stresses, it therefore means you need to provide more reinforcement at the top section and since the bottom area experiences compression stresses, it means more concrete will be at the bottom area, and less steel materials.

Another case that is worth discussing is the continuous beam or member, for a continuous member if you carefully study the displacement of the members when a load or force is acting on it. it becomes very easy to understand how the reinforcement will be placed on the beam. Let us look at the image below and study the displacement pattern

See the image below 3

You will notice that when a load is placed on the beam, the span and the support will experience tensional stresses, from the image above the spans A to B, B to C, and C to D will deflect downward which will cause those areas to have tension while the support B and C will be having hugging at the top which will result to tension at the support top areas.

Once you understand the behaviors of the load on the members, it will help you know where to place your reinforcement and how to place it. However, the number of reinforcement required will be based on a theoretical calculation that is outside our discussion today. The main aim of this subject matter is to give you a practical understanding of why and how we combine concrete with reinforcement at the site.

So for a continuous member or beam, especially if the beam is long, it a advisable to note that the bottom and the support area will need more reinforcement to take care of the tensional forces developed in that section as a result of the load acting on the member or beam.

In conclusion, the study of the concepts of reinforced concrete enables us to know where, how, and why we need reinforcement to combine with concrete. the way we combine these reinforcements depends on the behaviors of the members, once you understand how the members behave it becomes very easy to know where you will place your reinforcement. I hope this article will help you to determine where and how to place your reinforcement in beam members.

 

[[Category:Articles_needing_more_work]] [[Category:Projects_and_case_studies]] [[Category:Publications_/_reports]] [[Category:Construction_techniques]]

File:Block-work2.jpg

2021-10-25T15:29:57Z

Ebhosworks:

File:2015-11-02-1446504628-1544224-HowSuccessfulPeopleBeatStressHP.jpg

2021-10-25T15:25:09Z

Ebhosworks:

File:2brm-1-1024x819.png

2021-10-25T15:18:35Z

Ebhosworks:

File:Site-plan.jpg

2021-10-25T15:07:30Z

Ebhosworks:

How To Know Numbers Of Head Pan Of Sand And Gravel For A Bag Of Cement Mix

2021-10-25T14:30:28Z

Ebhosworks:

# [[File:Site-preparation.jpg]]Redirect:[[Cement|Cement]]

[[Category:Circular_economy]] [[Category:Definitions]] [[Category:International]] [[Category:Organisations]] [[Category:Publications_/_reports]] [[Category:Construction_techniques]] [[Category:Design]] [[Category:Property_development]]

File:Site-preparation.jpg

2021-10-25T14:22:42Z

Ebhosworks:

Concrete

2021-07-28T17:16:37Z

Ebhosworks:

[[File:Concrete290.jpg|link=File:Concrete290.jpg]]

= Introduction =

Concrete is the most commonly used man-made material on earth. It is an important construction material used extensively in buildings, bridges, roads and dams. Its uses range from structural applications, to paviours, kerbs, pipes and drains.

Concrete is a composite material, consisting mainly of Portland cement, water and aggregate (gravel, sand or rock). When these materials are mixed together, they form a workable paste which then gradually hardens over time.

For the different types, see Types of concrete.

= History =

A material similar to concrete was first developed by the Egyptians, consisting of lime and gypsum. Typically, lime, chalk or oyster shells continued being used as the cement forming agent until the early-1800s.

In 1824, Portland cement, a mixture of limestone and clay was burned and ground, and since then, this has remained the predominant cementing agent used in concrete production.

= Benefits of concrete =

There are numerous positive aspects of concrete:

* It is a relatively cheap material and has a relatively long life with few maintenance requirements.
* It is strong in compression.
* Before it hardens it is a very pliable substance that can easily be shaped.
* It is non-combustible.

= Limitations of concrete =

The limitations of concrete include:

* Relatively low tensile strength when compared to other building materials.
* Low ductability.
* Low strength-to-weight ratio.
* It is susceptible to cracking.

= Characteristics of concrete =

The characteristics of concrete are determined by the aggregate or cement used, or by the method that is used to produce it. The water-to-cement ratio is the determining factor in ordinary structural concrete with a lower water content resulting in a stronger concrete.

This, however, reduces the workability (and pumpability) of the concrete, which can be measured using the slump test. The grading, shape, texture and proportion of aggregate can also have a similar affect. If a particularly strong concrete is required, the amount of aggregate can be reduced in relation to the cement. However, cement is a significant cost factor, and increasing its proportion in the mix will increase the overall price.

For more information, see The properties of concrete.

= Concrete strength =

Concrete strength is determined by the force required to crush it and is measured in pounds per square inch or kilograms per square centimetre. Strength can be affected by many variables including moisture and temperature.

The tensile strength of concrete can be improved with the addition of metal rods, wires, cables or mesh. Where very high tensile stresses are expected (such as in wide unsupported spans in roofs or bridges) concrete can include pre-tensioned steel wires. This creates compressive forces in the concrete that help offset the tensile forces that the structure is subject to.

Sacrificial probes can be integrated within concrete to provide strength determination and this is likely to help improve construction methodologies.

For more information, see Testing concrete.

= Formwork =

Formwork is a temporary mould into which concrete is poured and formed. Traditional formwork is fabricated using timber, but it can also be constructed from steel, glass fibre reinforced plastics and other materials.

Formwork may be; temporary, re-usable, or stay-in-place. There are also a number of proprietary systems such as those used to support vertical formwork while concrete cures, consisting of a series of tubes and ties.

Efficiency within concrete construction is being improved by the adoption of hybrid solutions and innovations in formwork such as self-climbing forms.

See Formwork for more information.

= Sustainability =

Concrete has a relatively high embodied energy, resulting from its extraction, manufacture and transportation. Waste materials can be included within the concrete mix such as Recycled Crushed Aggregate (RCA), Ground Granulated Blast-Furnace Slag (GGBS) and Pulverised Fuel Ash (PFA).

In addition, moves are being made to assess the potential of using recycled concrete, however, issues such as moisture content and material variability may make this unviable.

Concrete is a very durable, low maintenance material and can provide thermal mass, helping reduce the energy consumption of buildings in operation.

= Related articles on Designing Buildings Wiki. =

* 3D concrete printer.
* Admixture, additive or agent.
* Admixtures in concrete.
* Alkali-activated binder.
* Alkali-aggregate reaction (AAR).
* Alkali-silica reaction (ASR).
* Architectural concrete.
* Blocked concrete delivery pumps.
* Cast-in-place concrete.
* Cellular concrete.
* Cement and concrete companies release 2050 Climate Ambition.
* Cement-free precast product.
* Cement mortar.
* Concrete batching plants.
* Concrete boom pumps.
* Concrete in aggressive ground (SD 1).
* Concrete joints.
* Concrete masonry unit CMU.
* Concrete repair mortars.
* Concrete-steel composite structures.
* Concrete superplasticizer.
* Concrete to cover.
* Concrete vs. steel.
* Concreting plant.
* Decarbonising concrete in the UK.
* Differences between jumpform and slipform climbing formwork systems.
* Glass reinforced concrete.
* Hempcrete.
* How to clean concrete.
* Laitance.
* Portland cement.
* Precast concrete.
* Prestressed concrete.
* Power float.
* Pyrite and mica redress issues in Dail Eireann.
* Rebar.
* Recycled concrete aggregate RCA.
* Reinforced concrete.
* Scabbling.
* Screed.
* Self-compacting concrete.
* Slip form.
* Smart concrete.
* Spanish brutalism.
* Stationary pump skills.
* Stratification of concrete.
* Testing concrete.
* Textile-reinforced mortars TRM.
* The properties of concrete.
* The World Recast: 70 buildings from 70 years of Concrete Quarterly.
* The use of concrete structures to protect construction sites.
* Types of concrete.
* Ultra high performance fibre concrete.
* Vibration Compaction Technology.

[[Category:DCN_Definition]] [[Category:DCN_Product_Knowledge]] [[Category:Products_/_components]]

How To Know Numbers Of Head Pan Of Sand And Gravel For A Bag Of Cement Mix

2021-07-28T17:08:10Z

Ebhosworks: Created page with "= How To Determine Concrete Mix Ratio In Relation To The Number Of Head Pans Of Sands And Gravels That Is Actually Needed For A Bag Of Cement. = In a bid to understand how to de..."

= How To Determine Concrete Mix Ratio In Relation To The Number Of Head Pans Of Sands And Gravels That Is Actually Needed For A Bag Of Cement. =

In a bid to understand how to determine [https://houseplanng.com/blog/how-to-know-numbers-of-head-pan-of-sand-and-gravel-for-a-bag-of-cement-mix/ concrete mix ratio] in relation to the number of head pans of sands and gravels that is actually needed for a bag of cement.

Concrete mix ratio is widely use by civil engineers to define the relationship between cement, sands and gravels.

Over the years concrete mix ratio have being use by many civil engineering authors to mean the quantity of cement in relation to the quantity of sands and gravel that will result in maximum strength at a particular period of time usually 28 days.

Having this in mind it therefore means that care must be taking when deciding the concrete mix ratio to use at construction site and how to convert it into bags for cement and head pans for sands and gravels.

To understand the concept of concrete mix ratio, the concept of concrete mix design can not be under estimated. If you will like to know more about concrete mix design in details please [https://coren.gov.ng/download/send/8-library/104-concrete-mix check Nigeria manual on (Concrete Mix Design the first of it kind)]

For the purpose of this article, i will be explaining some terms that will be use to help us understand better the concept of concrete mix ratio.

== Concrete Mix Design ==

This could be explained as a step by step method of achieving the right materials needed to produced a specific strength of concrete mix. For the purpose of our discussion i am going to limit it to how you can determine concrete mix ratio at site using a specific concrete grade.

== Concrete Mix Ratio ==

As earlier explained, it is the relationship that connects cement,water, sand and aggregated together that will result in a good concrete grade

== Concrete Grade (C) ==

Concrete grade can be explain to be the different minimum comprehensive strength of concrete at a specific period of time usually 28 days under a quality control situation.

== Characteristic strength of concrete (Fcu) ==

This could be explain as the comprehensive strength which the concrete must develop after 28 days of curing before failing to crushing.

== Concrete Curing ==

On the other hand is the process of ensuring that the concrete in question receives adequate moisture content and temperature in other to result in its maximum strength and durability after certain period of time.

Now that we have gotten clear understanding of the above terms lets begin by making reference to different grade of concrete in relation to their mix ratio and strength after specific period of time.

The BS code recommend that different concrete grade should be use for different purpose of construction work. These concrete grade will need to be converted in their mix ratio which will then be used at construction site. There are different types of concrete mix which are nominal mix and design mix. The nominal mix are always specified by volume and they are most widely used concrete mix in Nigeria today.

On the other hand the design mix is a more economical way which is done in the laboratory by using weight of different constituent materials to determine the strength or grade of concrete to be used at site.

The confusing part of the concrete mix ratio is that most young engineers, builders and masons do not know how to relate the mix ratio into bags for cement and head pans for sands and gravels. For the purpose of this article we will be looking at some specified grade of concrete and their mix ratio.

Note: the cement grades of 32.5 and 42.5 popularly used in Nigeria is not taking into account for this analysis.

The Grade are : 
Grade C-10 which has a concrete mix ratio of 1:4:6 
Grade C-15 which has a concrete mix ratio of 1:3:5 
Grade C-20 which has a concrete mix ratio of 1:2:4 
Grade C-25 which has a concrete mix ratio of 1:1.5:3

Now that we know the relationship between the concrete grades and mix ratio. it simply mean that if you must produce a concrete grade of say C-20, you will need a mix ratio of 1 head pan of cement : 2 head pans of sands : 4 head pans of gravels.

This is just the simple truth, but the confusion here is that cement is always measured in bags at construction site instead of head pans. So the question here is how do we determine the number of head pans of sands and gravels that is actually need for a bag of cement giving the concrete grade to be C-20 and the concrete mix ratio to be 1 : 2 : 4

With reference to Building Contractor Secrete, one bag of cement should be able to fill 2 head pans full of cement. If this is correct it therefore means that for every :

1 head pans of cement we will need 2 head pans of sand and 4 head pans of gravels to produce the required concrete grade.

Mathematically;

1 pan of cement = 2 pans of sand = 4 pans of gravels 
1 pan of cement = 2 pans of sand = 4 pans of gravels

if we add the above together we will have;

2 pans of cement = 4 pans of sand = 8 pans gravel

but remember 2 pans of cement = 1 bag of cement

therefore;

1 bag of cement = 4 pans of sand = 8 pans of gravel

This simply mean for every 1 bag of cement you will need 4 head pans of sand and 8 head pans of gravel to give you a concrete strength that will be equal to grade C-20 equal to 20 N/mm2

If you convert this to wheel barrow it means for every 1 bag of cement you will need 1 wheel barrow of sand and 2 wheel barrow of gravel to give the concrete grade strength of 20 N/mm2 This is the minimum standard that is suppose to be used at site during construction.[https://houseplanng.com/blog/how-to-know-numbers-of-head-pan-of-sand-and-gravel-for-a-bag-of-cement-mix/ You can check the video for more explanation.]

 
In Nigeria most construction site use below this minimum standard by using concrete mix ratio which reduce the concrete grade strength below grade C-10, for instances;

A concrete mix of 1 bag of cement with 10 head pan of sand and 12 head pans of gravel will give you a mix ratio of 1 : 5 : 6 which falls below concrete grade C-10

A concrete mix of 1 bag of cement with 8 head pans of sand and 10 head pans of gravel will result in a mix ratio of 1 : 4 : 5 which is greater than grade C-10 but less than grade C-15.

These two concrete mix describe above is what is generally use at most construction site in Nigeria. What this mean is that most construction site uses below the minimum concrete grade for reinforce concrete which is against the Nigeria design mix manual and British code of practice.

The use of concrete grade below the minimum standard should not be encourage. This could be as a result of high cost of cement or inability to deduce the right volume of materials needed to be use for a bag of cement.

Finally, proper care and steps should be taking by the Authorities in charge like COREN, NSE and others to educated the Nigerian artisan, craftsmen, masons and fresh graduate engineers of the danger of using sub standard concrete mix ratio, and educate them on how they can achieve the right concrete mix ratio for a bag of cement.

I hope this will help young engineers, builders and masons in making proper decision on how many head pans of sand and gravel that will be needed for 1 bags of cement to produce a minimum concrete grade of C-20, if you have any comment or want to improve in what i have on ground please feel free to help someone today or contact us now

Thanks for spending time to read.

[[Category:Circular_economy]] [[Category:Definitions]] [[Category:International]] [[Category:Organisations]] [[Category:Publications_/_reports]] [[Category:Construction_techniques]] [[Category:Design]] [[Category:Property_development]]

File:Woman engineer.jpeg

2021-07-28T17:04:07Z

Ebhosworks: