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Types of Bar Splice & Its Requirements

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        <h2>Bar splices</h2>
<p>In <a rel="nofollow" onclick="javascript:_gaq.push(['_trackPageview',
'/outgoing/article_exit_link/2443583']);"
href="http://www.aboutcivil.com" title="Civil Engineering">Civil
Engineering</a>, Bar splices are necessary bars of limitations of the
bars length available. It may also be required at construction joints and
also change from larger bars to smaller bars.</p>
<h3>Types of Bar Splices</h3>
<ol>
<li>Lap Splices</li>
<li>Mechanical Splices</li>
<li>Compression splices<br>Reinforcing bars in compression are spliced
mainly in columns, where bars are most often terminated just above each
floor or every other floor.<br><br>In accordance with the ACI
code:<br>For bars with fy &lt;= 60, 000 psi ls = (0.0009fy - 24)
db<br><br>But not less than 12"<br><br>For fc' &lt; 3000 psi - the splice
length must be increased to the computed laps by one third.</li>
<li>Welded Splices</li>
</ol>
<p>While using welding as an option, consider the following points:</p>
<ul>
<li>Reinforcing steel must be suitable for welding</li>
<li>Welded joints should not occur at or near bends,</li>
<li>Where possible, joints in parallel bars of the principal tensile
reinforcement should be staggered in the longitudinal direction,</li>
<li>Butt welded joints in compression resist 100 percent of the design
strength, but joints in tension should be designed to resist 80 percent
of the design strength.</li>
</ul>
<h3>Minimum lap splices in tension:</h3>
<p>Two different classifications of lap splices are established according
to the <strong>ACI </strong>code:</p>
<p>Class A splice - 1.0 ld</p>
<p>Class B splices - 1.3 ld</p>
<p>But no less than 12", lap splices in general must be class B
splices.</p>
<p>Class A splices are allowed when the area of reinforcement provided is
at least twice that of required by analysis over the entire length of the
splice and when one half or less of the total reinforcement is spliced
within the required lap length.</p>
<h3>Location of splices:</h3>
<p>Splice should be located away from the points of maximum tensile
stresses.</p>
<p>All of the bars should not be spliced at the same location i.e. the
splices should be staggered. When bars of different size are lap spliced
in compression, the splice length is to be the larger of the development
length of the larger bar and the splice length of the smaller bar.</p>
<p>In reinforced concrete construction splices between the ends of bars
are required to extend their length. Splices transferring stress are
generally lapped, but may also be welded or joined with mechanical
devices. Splices should be placed, wherever possible, away from points of
high stress and preferably should be staggered. Laps in fabric may be
layered or nested to maintain the lapped bars in one plane. Good
detailing should avoid spalling of the concrete in the neighborhood of
the splice and the width of the cracks should not exceed allowable
values.</p>
<p>Areas where typical bends or lap splices are present should be
reviewed in detail and tolerances, including clear distances from soil or
forms as dictated by code, should be monitored throughout. Assure that
sufficient chairs or dobies (small concrete blocks) are present to avoid
sagging of horizontal bars.</p>
<p>Both design drawings and a subcontractor's placing drawings should
clearly identify the condition and placement of reinforcing bars,
including size and location, anchorage length, location and length of lap
splices, and type and location of welded splices or mechanical
connections.</p>        <!--INFOLINKS_OFF-->
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posted:7/5/2011
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