reinforcement fixing for a beam - quality management procedure

8/11/2019 Reinforcement fixing for a beam - quality management procedure

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Quality assurance procedure forreinforcement fixing for in-situ

concrete beams

NAME : Tissera P.M.R.

INDEX NO : 110582T

DATE OF SUB : 26.09.2014


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Introduction

Concrete is an essential material in modern construction industry. It is being used for the

construction of various different structural elements and these structural elements are being

utilized to carry complex load patterns with innovative architectural and service requirements.

Anyway, these members basically carry compression and tension where the latter should behandled by the steel reinforcement embedded in concrete when it comes to reinforced concrete;

which will be denoted by RC hereafter in this text.

This Quality Assurance Procedure is written with reference to respective British Standards for

necessary specifications and the workmanship practices.

1. Specific steps to be followed in the execution of reinforcement fixing in beams

Preliminary check list

The necessary bars and links (stirrups) should be done by the bar bending yard as per the

bar bending schedule provided with reference to the shop drawings

The steel bars should be transported to the place where the fixing is carried out and a

tower crane or any other necessary transportation mean should be provided

The necessary formwork should be provided in accordance to the drawings with form oil

applied

The reinforcement for abutments (most often columns) should be partially done

Supports should be provided accordingly

At the least, one skilled steel fixer and one helper should be attended with the respective

tools and etc.

An experienced supervisor should be attended from time to time for QA/QC

A set of necessary drawings should be available for the reference

With the fulfillment of the above requirements, the reinforcement fixing can be started.

Method of execution

The main bars are identified as top bars and bottom bars according to the drawings.

Top bars are temporary attached to the abutment (column) reinforcement to make them

stay above their actual position. This is to make the reinforcement fixing easier. In

attaching the top bars temporary to the column reinforcement, it is advisable to direct the

anchorage part such that it goes down in to the column for a main beam and horizontally

in to the main beam or downwards as necessary when it is a secondary beam. This is

illustrated clearly in the images below.


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The spacing of the links as per the drawings provided is marked on the top bars using a

piece of chalk. In practice, the specified spacing may not be able to maintain with the

specified number of links. The conservative solution is to provide the specified number

of links spread equally as possible over the span of the beam. It is possible that service

ducts are crossing the beam laterally so that even the modified spacing may not be able to

maintain throughout the span. In such situations it is advisable to provide the modified

spacing as above along the undisturbed length and provide the links as close as to the

modified position within the disturbed region. This is shown in the image below.

After marking the appropriate spacing for the links, the links are inserted in to the top

bars now hanging above from the mid portion.

Then the bottom bars are inserted through the links such that the anchorage lengths aredirected as necessary.


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The links are distributed over the span and attached to the main bars in the marked

distances as necessary with the aid of binding wire.

The cover blocks (spacers) are attached to the links as necessary to keep the specified

cover to reinforcement.

The temporary attachments with the column reinforcement are removed and the

reinforcement cage is lowered in to the necessary place in the formwork.

Specifications and workmanship applicable

The main consideration in fixing of reinforcement for an in-situ concrete beam should be fixing

right bar with specified anchorage. Otherwise the purpose of fixing the bar will not be fulfilled.

Other than that, the BS8110-1:1997 specifies the specifications and workmanship practices

applicable in the section 7 of the text and in section 5.3.2 in ICTAD specifications.

Key factors of the details are presented below.

Tying of bars:

Reinforcement bars should be placed according to the drawings and the tying of bars should be

done so that they do not get displaced in later actions. And also the tying should be done with

steel wire of 0.9mm to 1.6mm using two strands at the intersections of reinforcement. The ends

of the steel wire should be bent back in to the concrete body.

Cover blocks:

The cover blocks of 1:1:1/2 with 40mm x 40mm should be provided to keep the reinforcement

so that the beam has the adequate cover to reinforcements as given in the drawings.

Cover:

Cover is specified in table 5.4 the ICTAD specifications. The structural designer may use it or

his preferred COP to choose the cover value. The advantage of following ICTAD specified

values is that it is more suitable to our environmental conditions keeping the balance between

economy and durability. And also there are notes that can be used to optimize the design.


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Inspection and tests to be performed

The casting of the beam can be done only if the fixing of reinforcement is approved by the

consultant. To get the approval, the workmanship and the materials used should be up to a

certain quality. For that, there are few inspection steps to be followed with care. They are stated

below.

The reinforcement cage should be done tightly to prevent misplacement during concrete

pouring

The cover blocks should be provided necessarily to maintain the cover specified in the

design

The cover blocks should not be easily breakable

Any foreign material such as unused binding wire, broken cover block pieces should be

removed manually and/or with compressed air

The links should be spaced according to the design

The reinforcement cage should be connected to other elements as shown in the design

reinforcement fixing for a beam - quality management procedure

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