<!doctype HTML public "-//W3C//DTD HTML 4.0 Frameset//EN">

<html>

<head>
<title>SDG 3.15 Box Culvert Design</title>
<meta http-equiv="content-type" content="text/html; charset=windows-1252">
<meta name="generator" content="RoboHelp by eHelp Corporation www.ehelp.com">
<link rel="stylesheet" href="SDGandSDM_ns.css"><script type="text/javascript" language="JavaScript" title="WebHelpSplitCss">
<!--
if (navigator.appName !="Netscape")
{   document.write("<link rel='stylesheet' href='SDGandSDM.css'>");}
//-->
</script>
<style type="text/css">
<!--
div.whs1 { width:100%; }
table.whs2 { x-cell-content-align:top; width:100%; border-bottom-style:Solid; border-bottom-width:1px; border-bottom-color:#000000; border-spacing:0px; }
col.whs3 { width:50%; }
tr.whs4 { x-cell-content-align:top; }
td.whs5 { width:50%; padding-right:0px; padding-left:0px; border-top-style:none; border-right-style:none; border-bottom-style:none; border-left-style:none; }
td.whs6 { width:50%; padding-right:0px; padding-left:0px; border-top-style:none; border-right-style:none; border-bottom-style:none; }
td.whs7 { width:50%; padding-right:0px; padding-left:0px; border-right-style:none; border-bottom-style:Solid; border-left-style:none; border-bottom-width:1px; }
td.whs8 { width:50%; padding-right:0px; padding-left:0px; border-right-style:none; border-bottom-style:Solid; border-bottom-width:1px; }
table.whs9 { x-cell-content-align:Center; left:0px; top:576px; width:620px; border-spacing:0px; }
col.whs10 { width:100%; }
tr.whs11 { x-cell-content-align:center; }
td.whs12 { width:100%; padding-right:10px; padding-left:10px; border-bottom-style:None; border-right-style:None; border-left-style:None; border-top-style:None; }
p.whs13 { margin-left:24px; }
td.whs14 { width:100%; padding-right:10px; padding-left:10px; border-bottom-style:None; border-right-style:None; border-left-style:None; }
table.whs15 { x-cell-content-align:top; width:100%; border-spacing:0px; }
td.whs16 { width:100%; padding-right:10px; padding-left:10px; border-bottom-style:None; border-left-style:None; border-top-style:None; border-right-style:None; }
p.whs17 { margin-left:48px; }
td.whs18 { width:100%; padding-right:10px; padding-left:10px; border-right-style:None; border-left-style:None; border-bottom-style:None; }
table.whs19 { x-cell-content-align:top; left:0px; top:1071px; width:623px; margin-left:24px; border-spacing:0px; }
col.whs20 { width:22.855%; }
col.whs21 { width:77.145%; }
td.whs22 { width:22.855%; border-left-width:1px; border-left-color:#000000; border-left-style:Solid; border-top-style:Solid; border-top-color:#000000; border-top-width:1px; border-right-width:1px; border-right-color:#000000; border-right-style:Solid; border-bottom-style:Solid; border-bottom-color:#000000; border-bottom-width:1px; padding-right:10px; padding-left:10px; }
p.whs23 { font-weight:bold; }
td.whs24 { width:77.145%; border-top-style:Solid; border-top-color:#000000; border-top-width:1px; border-right-width:1px; border-right-color:#000000; border-right-style:Solid; border-bottom-style:Solid; border-bottom-color:#000000; border-bottom-width:1px; padding-right:10px; padding-left:10px; }
td.whs25 { width:22.855%; border-left-width:1px; border-left-color:#000000; border-left-style:Solid; border-right-width:1px; border-right-color:#000000; border-right-style:Solid; border-bottom-style:Solid; border-bottom-color:#000000; border-bottom-width:1px; padding-right:10px; padding-left:10px; }
td.whs26 { width:77.145%; border-right-width:1px; border-right-color:#000000; border-right-style:Solid; border-bottom-style:Solid; border-bottom-color:#000000; border-bottom-width:1px; padding-right:10px; padding-left:10px; }
col.whs27 { width:4.368%; }
col.whs28 { width:95.632%; }
td.whs29 { width:100%; padding-right:10px; padding-left:10px; border-top-style:none; border-top-width:4px; border-top-color:#000000; border-right-style:none; border-bottom-style:none; border-left-style:none; }
td.whs30 { width:4.368%; padding-right:10px; padding-left:10px; border-right-style:none; border-bottom-style:none; border-left-style:none; }
td.whs31 { width:95.632%; padding-right:10px; padding-left:10px; border-right-style:none; border-right-width:4px; border-right-color:#000000; border-bottom-style:none; }
td.whs32 { width:4.368%; padding-right:10px; padding-left:10px; border-right-style:none; border-bottom-style:none; border-bottom-width:4px; border-bottom-color:#000000; border-left-style:none; }
td.whs33 { width:95.632%; padding-right:10px; padding-left:10px; border-right-style:none; border-right-width:4px; border-right-color:#000000; border-bottom-style:none; border-bottom-width:4px; border-bottom-color:#000000; }
col.whs34 { width:4.524%; }
col.whs35 { width:95.476%; }
td.whs36 { width:4.524%; padding-right:10px; padding-left:10px; border-bottom-style:None; border-right-style:None; border-left-style:None; }
td.whs37 { width:95.476%; padding-right:10px; padding-left:10px; border-bottom-style:None; border-right-style:None; }
td.whs38 { width:4.524%; padding-right:10px; padding-left:10px; border-right-style:None; border-left-style:None; border-bottom-style:None; }
p.whs39 { text-align:center; }
img_whs40 { border:none; border-style:none; width:88px; height:8px; float:none; }
p.whs41 { margin-left:24px; text-indent:-24px; }
-->
</style><script type="text/javascript" language="JavaScript">
<!--
if ((navigator.appName == "Netscape") && (parseInt(navigator.appVersion) == 4))
{
  var strNSS = "<style type='text/css'>";
  strNSS += "p.whs41 {text-indent:1pt; }";
  strNSS +="</style>";
  document.write(strNSS);
}
//-->
</script>
<script type="text/javascript" language="JavaScript" title="WebHelpInlineScript">
<!--
function reDo() {
  if (innerWidth != origWidth || innerHeight != origHeight)
     location.reload();
}
if ((parseInt(navigator.appVersion) == 4) && (navigator.appName == "Netscape")) {
	origWidth = innerWidth;
	origHeight = innerHeight;
	onresize = reDo;
}
onerror = null; 
//-->
</script>
<style type="text/css">
<!--
div.WebHelpPopupMenu { position:absolute; left:0px; top:0px; z-index:4; visibility:hidden; }
-->
</style><script type="text/javascript" language="javascript1.2" src="../whmsg.js"></script>
<script type="text/javascript" language="javascript" src="../whver.js"></script>
<script type="text/javascript" language="javascript1.2" src="../whproxy.js"></script>
<script type="text/javascript" language="javascript1.2" src="../whutils.js"></script>
<script type="text/javascript" language="javascript1.2" src="../whtopic.js"></script>
</head>
<body><script type="text/javascript" language="javascript1.2">
<!--
if (window.gbWhTopic)
{
	if (window.addTocInfo)
	{
	addTocInfo("Vol. 1 - Design Guidelines\n3 - Substructure and Retaining Walls\nSDG 3.15 Box Culvert Design");
addAvenueInfo("DesignGuidelines","DesignGuidelines/SDG3.14FenderSystems.htm","DesignGuidelines/SDG4.1General.htm");
addButton("show",BTN_TEXT,"Show","","","","",0,0,"","","");

	}
	if (window.writeBtnStyle)
		writeBtnStyle();

	if (window.writeIntopicBar)
		writeIntopicBar(1);

	if (window.setRelStartPage)
	{
	setRelStartPage("../StructuresManual.htm");

		autoSync(1);
		sendSyncInfo();
		sendAveInfoOut();
	}
}
else
	if (window.gbIE4)
		document.location.reload();
//-->
</script><script type="text/javascript" language="JavaScript1.2" src="../ehlpdhtm.js" x-save-method="compute-relative" name="EHELP_DHTM"></script>
<script type="text/javascript"
		language=JavaScript1.2>
<!-- 
if( typeof( kadovInitEffects ) != 'function' ) kadovInitEffects = new Function();if( typeof( kadovInitTrigger ) != 'function' ) kadovInitTrigger = new Function();if( typeof( kadovFilePopupInit ) != 'function' ) kadovFilePopupInit = new Function();if( typeof( kadovTextPopupInit ) != 'function' ) kadovTextPopupInit = new Function();
 //-->
</script>


<div placeholder id="header" class="whs1"><table x-use-null-cells cellspacing="0" width="100%" class="whs2">
  <col class="whs3">
  <col class="whs3">
  <tr valign="top" class="whs4">
  <td width="50%" class="whs5">
  <p class=HeaderFooterText
	style="font-size: 8pt;">Structures Design Guidelines</td>
  <td width="50%" class="whs6">
  <p class=HeaderFooterText
	style="text-align: right; font-size: 8pt;"
	align=right>&nbsp;Jan 
 2008</td></tr>
  <tr valign="top" class="whs4">
  <td colspan="1" rowspan="1" width="50%" class="whs7">
  <p class=HeaderFooterText
	style="font-size: 8pt;">3 - Substructure and Retaining Walls</td>
  <td colspan="1" rowspan="1" width="50%" class="whs8">
  <p class=HeaderFooterText
	style="text-align: right;"
	align=right>&nbsp;</td></tr>
 </table>
</div>
<p>&nbsp;</p>

<h2><a name=SDG_3_15_Culverts></a>3.15 Concrete Box and Three-Sided Culvert 
 Design <a class="expandspot" href="javascript:kadovTextPopup(this)" id="a3" style="font-weight: bold;"><span class=expandtext
											style="color: #008000;"><font color=green >(01/07)</font></span></a><span class=expandtext style="display: 'none';" id=POPUP199959837 >   Jan 2007 - Added New Section.</span></h2>

<h2>3.15.1 General</h2>

<p>Use <span style="font-weight: bold; font-style: italic;"><I><B><a href="http://www.fdot.gov/roadway/PPMManual/PPM.htm"
	target=_blank>PPM</a> Volume 1,</B></I></span> Chapter 33 for culvert plans 
 preparation in conjunction with the design requirements of this Section. 
 Refer to <span style="font-weight: bold; font-style: italic;"><I><B>SDG</B></I></span> 
 Chapter 1 for the box culvert <a href="javascript:void(0);" id="a1" onMouseOver="if (parseInt(navigator.appVersion) >= 4 && typeof(BSPSPopupOnMouseOver) == 'function') BSPSPopupOnMouseOver(event);" class="BSSCPopup" onclick="BSSCPopup('SDG1.4ConcreteAndEnvironment.htm#Table_1_3_Concrete_Class');return false;">concrete class</a><script 
 type="text/javascript"
	language=JavaScript1.2><!--
kadovFilePopupInit('a1');
//--></script> 
 and reinforcing <a href="javascript:void(0);" id="a2" onMouseOver="if (parseInt(navigator.appVersion) >= 4 && typeof(BSPSPopupOnMouseOver) == 'function') BSPSPopupOnMouseOver(event);" class="BSSCPopup" onclick="BSSCPopup('SDG1.4ConcreteAndEnvironment.htm#Concrete_Cover');return false;">steel cover</a><script type="text/javascript"
	language=JavaScript1.2><!--
kadovFilePopupInit('a2');
//--></script> 
 requirements.</p>

<h3>3.15.2 Design Method</h3>

<p>Design new reinforced concrete culverts and extensions to existing culverts 
 (precast or cast-in-place, four-sided or three-sided) subjected to either 
 earth fill and/or highway vehicle loading in accordance with the <span 
 style="font-weight: bold; font-style: italic;"><I><B>AASHTO LRFD Bridge Design 
 Specifications.</B></I></span></p>

<h3>3.15.3 Load Modifiers and Load Factors [3.4.1] [12.5.4]</h3>

<p class=OutlineA>A. The product of the load modifiers and maximum load 
 factors [ (<span style="font-family: 'Times New Roman', serif; font-size: 14pt;"><font size=4 style="font-size:14pt;">&#951;</font></span>) 
 x (<span style="font-family: Symbol, serif;
					font-size: 14pt;
					font-weight: bold;"><font size=4 style="font-size:14pt;"><B>g</B></font></span>) ] for Strength Limit 
 States shall be equal to:</p>

<p class=OutlineA1>1.) Box Culverts (four-sided)</p>

<p class=OutlineA1a>&nbsp;&nbsp;1.05 
 x 1.30 = 1.365 for Horizontal Earth Pressures (EH) </p>

<p class=OutlineA1a>&nbsp;&nbsp;1.05 
 x 1.35 = 1.418 for Vertical Earth Pressure (EV) </p>

<p class=OutlineA1>2.) Three-Sided Culverts </p>

<p class=OutlineA1a
	style="text-indent: -9px;">1.05 x 1.35 = 1.418 for Horizontal and Vertical 
 Earth Pressure (EV and EH)</p>

<p class=OutlineA>B. Use 1.00 as the load modifiers (<span style="font-family: 'Times New Roman', serif; font-size: 14pt;"><font size=4 style="font-size:14pt;">&#951;</font></span>) 
 for horizontal loads when investigating the minimum horizontal earth pressure 
 effects in accordance with <span style="font-weight: bold; font-style: italic;"><I><B>LRFD</B></I></span> 
 [3.11.7], and combined with the maximum load factors for Strength Limit 
 State investigation. </p>

<p class=OutlineA>C. Use 1.00 as the load modifier (<span style="font-family: 'Times New Roman', serif; font-size: 14pt;"><font size=4 style="font-size:14pt;">&#951;</font></span>) 
 for all other Limit States and Load Types including construction load 
 investigation.</p>

<h3>3.15.4 Dead Loads and Earth Pressure [3.5] [3.11.5] [3.11.7] </h3>

<p class=OutlineA>A. The dead load on the top slab consists of the pavement, 
 soil, and the concrete slab. For simplicity in design, the pavement may 
 be assumed to be soil. </p>

<p class=OutlineA>B. Use the following design criteria in determining dead 
 load and earth pressures:</p>

<table x-use-null-cells cellspacing="0" width="620" class="whs9">
<col class="whs10">

<tr valign="middle" class="whs11">
<td rowspan="1" colspan="1" width="100%" class="whs12">
<p class="whs13">Soil = 120 pcf</td></tr>

<tr valign="middle" class="whs11">
<td rowspan="1" colspan="1" width="100%" class="whs14">
<p class=OutlineA
	style="margin-left: 24px; text-indent: 0px;">Concrete = 150 pcf</td></tr>
</table>

<table x-use-null-cells cellspacing="0" width="100%" class="whs15">
<col class="whs10">

<tr valign="top" class="whs4">
<td rowspan="1" colspan="1" width="100%" class="whs16">
<p class=OutlineA
	style="margin-left: 24px; text-indent: 0px;">Horizontal earth pressure 
 (At-Rest) for:</td></tr>

<tr valign="top" class="whs4">
<td rowspan="1" colspan="1" width="100%" class="whs14">
<p class="whs17">Maximum load effects = 60 pcf, (assumes soil 
 internal friction angle = 30°)</td></tr>

<tr valign="top" class="whs4">
<td rowspan="1" colspan="1" width="100%" class="whs18">
<p class=OutlineA
	style="text-indent: 0px; margin-left: 48px;">Minimum load effects = 
 30 pcf, (50% of maximum load effects)</td></tr>
</table>

<p class=OutlineA>&nbsp;C. 
 Modify vertical earth pressures in accordance with <span style="font-style: italic; font-weight: bold;"><I><B>LRFD</B></I></span> 
 [12.11.2.2.1], Modification of Earth Loads for Soil Structure Interaction 
 (Embankment Installations) for both box and three-sided culverts.</p>

<h3>3.15.5 Live Load</h3>

<p>Design reinforced concrete culverts for HL-93. Lane loading is required 
 for the design of culverts with spans greater than 15 feet in lieu of 
 the exemption in <span style="font-weight: bold; font-style: italic;"><I><B>LRFD</B></I></span> 
 [3.6.1.3.3]. </p>

<p class=Commentary
	style="margin-left: 0px;">Commentary: Concurrent lane loading is necessary 
 for <span style="font-weight: bold;"><B>LRFD</B></span> designs because the SU4 
 Florida Legal Load produces greater flexural moments then HL-93 without 
 lane loading for spans exceeding 18 feet. </p>

<h3>3.15.6 Wall Thickness Requirements</h3>

<p class=OutlineA>A. Determine the exterior wall thickness for concrete 
 culverts based on the design requirements, except that the following minimum 
 thickness requirements have been established to allow for a better distribution 
 of negative moments and corner reinforcement: </p>

<p>&nbsp;</p>

<table x-use-null-cells cellspacing="0" width="623" class="whs19">
<script language='JavaScript'><!--
if ((navigator.appName == "Netscape") && (parseInt(navigator.appVersion) == 4)) document.write("</table><table x-use-null-cells cellspacing='0' width='623' border='1' bordercolor='black' bordercolorlight='black' bordercolordark='black'>");
//--></script>
<col class="whs20">
<col class="whs21">

<tr valign="top" class="whs4">
<td width="22.855%" class="whs22">
<p class="whs23">CLEAR SPAN</td>
<td width="77.145%" class="whs24">
<p class="whs23">MINIMUM EXTERIOR WALL THICKNESS</td></tr>

<tr valign="top" class="whs4">
<td width="22.855%" class="whs25">
<p>&lt; 8 ft. </td>
<td width="77.145%" class="whs26">
<p>7-inch (Precast); 8-inch. (C.I.P.)</td></tr>

<tr valign="top" class="whs4">
<td width="22.855%" class="whs25">
<p>8 ft. to &lt; 14 ft.</td>
<td width="77.145%" class="whs26">
<p>8-inch</td></tr>

<tr valign="top" class="whs4">
<td width="22.855%" class="whs25">
<p>14 ft. to &lt; 20 ft.</td>
<td width="77.145%" class="whs26">
<p>10-inch</td></tr>

<tr valign="top" class="whs4">
<td width="22.855%" class="whs25"><span style="font-size: 10pt;"><font size=2 style="font-size:10pt;">20 ft. and greater</font></span></td>
<td width="77.145%" class="whs26">
<p>12- inch</td></tr>
<script language='JavaScript'><!--
if ((navigator.appName == "Netscape") && (parseInt(navigator.appVersion) == 4)) document.write("</table></table><table>");
//--></script>
</table>

<p>&nbsp;</p>

<p class=OutlineA>B. The interior wall thickness in multi-cell culverts 
 must not be less than 7-inches for precast culverts and 8-inches for cast-in-place 
 culverts. </p>

<p class=OutlineA>C. Increase the minimum wall thickness by one inch for 
 concrete culverts in extremely aggressive environments (3-inch concrete 
 cover).</p>

<h3>3.15.7 Concrete Strength and Class</h3>

<p>Design reinforced concrete culverts for the following concrete strengths 
 in accordance with the <span style="font-weight: bold; font-style: italic;"><I><B>SDG</B></I></span> 
 Chapter 1:</p>

<table x-use-null-cells cellspacing="0" width="100%" class="whs15">
<col class="whs27">
<col class="whs28">

<tr valign="top" class="whs4">
<td rowspan="1" colspan="2" width="100%" class="whs29">
<p>Precast:</td>
</tr>

<tr valign="top" class="whs4">
<td width="4.368%" class="whs30">
<p>&nbsp;</td>
<td width="95.632%" class="whs31">
<p><span style="font-family: 'Times New Roman', serif;
				font-size: 14pt;
				font-style: italic;"><font size=4 style="font-size:14pt;"><I>f </I></font></span><span style="font-size: 14pt;"><font size=4 style="font-size:14pt;">'</font></span><span 
 style="font-size: 14pt;
		font-family: 'Times New Roman', serif;
		font-style: italic;"><font size=4 style="font-size:14pt;"><I>c</I></font></span> = 5,000 psi (Class II modified, or 
 Class III) in Slightly Aggressive Environments</td></tr>

<tr valign="top" class="whs4">
<td width="4.368%" class="whs32">
<p>&nbsp;</td>
<td width="95.632%" class="whs33">
<p><span style="font-family: 'Times New Roman', serif;
				font-size: 14pt;
				font-style: italic;"><font size=4 style="font-size:14pt;"><I>f </I></font></span><span style="font-size: 14pt;"><font size=4 style="font-size:14pt;">'</font></span><span 
 style="font-size: 14pt;
		font-family: 'Times New Roman', serif;
		font-style: italic;"><font size=4 style="font-size:14pt;"><I>c</I></font></span> = 5,500 psi (Class IV) in Moderately 
 and Extremely Aggressive Environments</td></tr>
</table>

<table x-use-null-cells cellspacing="0" width="100%" class="whs15">
<col class="whs34">
<col class="whs35">

<tr valign="top" class="whs4">
<td rowspan="1" colspan="2" width="100%" class="whs12">
<p>Cast-in-place:</td>
</tr>

<tr valign="top" class="whs4">
<td width="4.524%" class="whs36">
<p>&nbsp;</td>
<td width="95.476%" class="whs37">
<p><span style="font-family: 'Times New Roman', serif;
				font-size: 14pt;
				font-style: italic;"><font size=4 style="font-size:14pt;"><I>f </I></font></span><span style="font-size: 14pt;"><font size=4 style="font-size:14pt;">'</font></span><span 
 style="font-size: 14pt;
		font-family: 'Times New Roman', serif;
		font-style: italic;"><font size=4 style="font-size:14pt;"><I>c</I></font></span> = 3,400 psi (Class II) in Slightly 
 Aggressive Environments</td></tr>

<tr valign="top" class="whs4">
<td width="4.524%" class="whs38">
<p>&nbsp;</td>
<td width="95.476%" class="whs37">
<p><span style="font-family: 'Times New Roman', serif;
				font-size: 14pt;
				font-style: italic;"><font size=4 style="font-size:14pt;"><I>f </I></font></span><span style="font-size: 14pt;"><font size=4 style="font-size:14pt;">'</font></span><span 
 style="font-size: 14pt;
		font-family: 'Times New Roman', serif;
		font-style: italic;"><font size=4 style="font-size:14pt;"><I>c</I></font></span> = 5,500 psi (Class IV) in Moderately 
 and Extremely Aggressive Environments</td></tr>
</table>

<h3>3.15.8 Reinforcement</h3>

<p class=OutlineA>A. Reinforcement may be deformed bars, smooth welded 
 wire reinforcement, or deformed welded wire reinforcement. Use a yield 
 strength of 60 ksi for deformed bar reinforcement and 65 ksi for welded 
 wire reinforcement.</p>

<p class=OutlineA>B. For the maximum service load stress in the design 
 of reinforcement for crack control, comply with <span style="font-weight: bold; font-style: italic;"><I><B>LRFD</B></I></span> 
 [12.11.3] using the following exposure factors for <span style="font-weight: bold; font-style: italic;"><I><B>LRFD</B></I></span> 
 [5.7.3.4]:</p>

<p class=OutlineA
	style="text-indent: 0px; margin-left: 36px;">&nbsp;<span 
 style="text-indent: 6px;
		font-family: Symbol, serif;
		font-size: 14pt;"><font size=4 style="font-size:14pt;">g</font></span><span style="vertical-align: Sub;">e</span><span 
 style="text-indent: 6px;
		font-family: Symbol, serif;
		font-size: 12pt;"> <font size=3 style="font-size:12pt;"></font></span><span style="text-indent: 6px;">= 1.00 
 (Class 1) for inside face reinforcement in slightly to moderately aggressive 
 environments, and extremely aggressive environments where a minimum 3 
 inches of concrete cover is provided;</span></p>

<p class=OutlineA
	style="text-indent: 0px; margin-left: 36px;"><span style="font-family: Symbol, serif; font-size: 14pt;"><font size=4 style="font-size:14pt;">g</font></span><span 
 style="vertical-align: Sub;">e</span> = 0.75 (Class 2) for outside face 
 reinforcement in all environments.</p>

<p class=OutlineA>C. Ensure that reinforcement stresses for the fatigue 
 limit state satisfy the requirements of <span style="font-weight: bold; font-style: italic;"><I><B>LRFD</B></I></span> 
 [5.5.3.2] and the following reduced stress range (in ksi) for welded wire 
 reinforcement with cross welds within a distance of 1/4 of the clear span 
 from the critical sections:</p>

<p class=OutlineA
	style="text-indent: 0px; margin-left: 36px;"><span style="font-family: 'Times New Roman', serif;
	font-style: italic;
	font-size: 14pt;"><font size=4 style="font-size:14pt;"><I>f</I></font></span><span style="font-family: 'Times New Roman', serif;
											font-size: 12pt;
											vertical-align: Sub;
											font-style: italic;"><font size=3 style="font-size:12pt;"><I>f</I></font></span> 
 &nbsp;<span style="x-text-underline: normal; /*begin!kadov{{*/ text-decoration: underline; /*}}end!kadov*/ "><U>&lt;</U></span> 
 16 – 0.33 f<span style="vertical-align: Sub;">min</span> </p>

<p class=OutlineA>D. Provide minimum reinforcement in accordance with <span 
 style="font-weight: bold; font-style: italic;"><I><B>LRFD</B></I></span> [5.7.3.3.2] 
 for cast-in-place culverts and simple span top slabs of precast culverts, 
 and <span style="font-weight: bold; font-style: italic;"><I><B>LRFD</B></I></span> [12.11.4.3.2 
 and 12.14.5.8] for precast culverts. Additionally, for precast culverts 
 with earth fill cover equal to or greater than 2 feet:</p>

<p class=OutlineA1>1.) Where reinforcement is distributed on both inside 
 and outside faces, the ratio of minimum reinforcement area to gross concrete 
 area may be reduced to 0.001, but not less than the area of reinforcement 
 required to satisfy 1.33 times the factored flexural moment for reinforcement 
 ratios less than 0.002. &nbsp;</p>

<p class=OutlineA1>2.) Walls or slabs with a thickness equal to or less 
 than 13 inches may contain only a single layer of reinforcement, located 
 at the tension face when the opposite face is permanently in compression 
 and in contact with the soil. </p>

<p class=OutlineA>E. Provide distribution reinforcement as described in 
 <span style="font-weight: bold; font-style: italic;"><I><B>LRFD</B></I></span> [9.7.3.2], 
 transverse to the main flexural reinforcement in both the top and bottom 
 slabs of reinforced concrete box culverts for earth fill cover heights 
 less than two feet as follows:</p>

<p class=OutlineA1>1.) For skews <span style="x-text-underline: normal; /*begin!kadov{{*/ text-decoration: underline; /*}}end!kadov*/ "><U>&lt;</U></span> 
 60°, provide the amount of distribution reinforcement required in <span 
 style="font-weight: bold; font-style: italic;"><I><B>LRFD</B></I></span> [9.7.3.2] first 
 equation.</p>

<p class=OutlineA1>2.) For skews &gt; 60°, provide the amount of distribution 
 reinforcement required in <span style="font-weight: bold; font-style: italic;"><I><B>LRFD</B></I></span> 
 [9.7.3.2] second equation.</p>

<p class=OutlineA>F. Do not use shear reinforcement in concrete culverts. 
 Design slab and wall thickness concrete shear capacity in accordance with 
 <span style="font-weight: bold; font-style: italic;"><I><B>LRFD</B></I></span> [5.8] 
 and [5.14.5.3].</p>

<h3>3.15.9 Reinforcement Details</h3>

<p class=OutlineA>A. Design the main reinforcement in the top and bottom 
 slabs perpendicular to the sidewalls in cast-in-place culverts and non-skewed 
 units of precast culverts. For reinforcement requirements of skewed precast 
 culverts, see <span style="font-weight: bold; font-style: italic;"><I><B>SDG</B></I></span> 
 3.5.10.</p>

<p class=OutlineA>B. The minimum inside bend diameter for negative moment 
 reinforcement (outside corners of top and bottom slabs) must satisfy the 
 requirements of <span style="font-weight: bold; font-style: italic;"><I><B>LRFD</B></I></span> 
 [5.10.2.3] and be not less than 4.0 d<span style="vertical-align: Sub;">b</span> 
 for welded wire reinforcement.</p>

<p class=OutlineA>C. Top and bottom slab transverse reinforcement &nbsp;must 
 be full-length bars, unless spliced to top and bottom corner reinforcement. 
 </p>

<h3>3.15.10 Skewed Culverts</h3>

<p class=OutlineA>A. Design and detail skewed precast concrete culverts 
 with non-skewed interior units designed for the clear span perpendicular 
 to the sidewalls and skewed end units designed for the skewed clear span. 
 </p>

<p class=OutlineA>B. For a cast-in-place concrete box culvert with a skewed 
 end, the top and bottom slab reinforcement will be &quot;cut&quot; to 
 length to fit the skewed ends. The &quot;cut&quot; transverse bars have 
 the support of only one culvert sidewall and must be supported at the 
 other end by edge beams (headwall or cutoff wall). See <span style="font-weight: bold; font-style: italic;"><I><B><a 
 href="http://www.fdot.gov/roadway/DesignStandards/Standards.htm"
	target=_blank>Design Standards</a></B></I></span> Index No. 289 for layout 
 details.</p>

<p class=OutlineA
	style="font-style: italic;
			text-indent: 0px;
			margin-left: 0px;">Commentary: &nbsp;Precast 
 concrete culverts with skewed ends usually cannot use edge beams as stiffening 
 members because of forming restrictions. The transverse reinforcement 
 must be splayed to fit the geometry of the skew. This splaying of the 
 reinforcement will increase the length of the transverse bars and, more 
 importantly, the design span of the end unit. For small skews, the splayed 
 reinforcement is usually more than adequate. However, large skews will 
 require more reinforcement and may require an increased slab thickness 
 or integral headwalls.</p>

<h3>3.15.11 Deflection Limitations [2.5.2.6.2]</h3>

<p>Ensure that top slab deflection due to the live load plus impact does 
 not exceed 1/800 of the design span. &nbsp;For 
 culverts located in urban areas used in part by pedestrians &nbsp;this 
 deflection must not exceed 1/1000 of the design span. Determine deflections 
 in accordance with <span style="font-weight: bold; font-style: italic;"><I><B>LRFD</B></I></span> 
 [2.5.2.6.2]. &nbsp;Gross 
 section properties may be utilized.</p>

<h3>3.15.12 Analysis and Foundation Boundary Conditions</h3>

<p class=OutlineA>A. Analyze culverts using elastic methods and model the 
 cross section as a plane frame (2D) using gross section properties.</p>

<p class=OutlineA>B. For box culverts restrain the bottom slab by any of 
 the following methods:</p>

<p class=OutlineA1>1.) Fully pinned support at one corner and pin-roller 
 support at the opposite corner;</p>

<p class=OutlineA1>2.) Vertical springs (linear-elastic or non-linear soil 
 springs) at a minimum of tenth points and a horizontal restraint at one 
 corner;</p>

<p class=OutlineA1>3.) Beam on elastic foundation and a horizontal restraint 
 at one corner.</p>

<p class=OutlineA1
	style="margin-left: 24px; text-indent: 0px;">Obtain the modulus of 
 subgrade reaction from the Geotechnical Engineer when performing the more 
 refined analyses in 2.) and 3.). </p>

<p class=OutlineA>C. Three-sided culverts on spread footings should be 
 designed at critical sections for the governing case of either, a fully 
 pinned support condition and a pin-roller support condition. A refined 
 analysis of the pin-roller support condition is permitted if soil springs 
 (linear-elastic or non-linear) are substituted for the horizontal supports 
 allowing for one inch movement at the maximum horizontal reaction for 
 the governing factored load case.</p>

<p class=Commentary>Commentary: &nbsp;Designers 
 of three-sided culverts typically compute moments, shears, and thrusts 
 based on fully pinned support conditions that are able to resist horizontal 
 forces and prevent horizontal displacements. These boundary conditions 
 may not be appropriate for most foundations in Florida. Fully pinned support 
 conditions could be used if site and construction conditions are able 
 to prevent any horizontal displacement of frame leg supports. Such a condition 
 may exist if footings are on rock or pile supported, and frame legs are 
 keyed into footings with adequate details and construction methods.</p>

<h3>3.15.13 Span-to-Rise Ratios</h3>

<p>Span-to-rise ratios that exceed 4-to-1 are not recommended. As span-to-rise 
 ratios approach 4-to-1, frame moment distribution is more sensitive to 
 support conditions, and positive moments at midspan can significantly 
 exceed computed values even with relatively small horizontal displacement 
 of frame leg supports. If it is necessary to use a three-sided frame with 
 a span-to-rise ratio in excess of 4-to-1, the structure must be analyzed 
 for midspan positive moment using pin-roller support conditions.</p>

<h3>3.15.14 Load Rating Requirements</h3>

<p class=OutlineA>A. Load rate bridge-size culverts (see definition in 
 <span style="font-weight: bold; font-style: italic;"><I><B><a href="http://www.fdot.gov/roadway/PPMManual/PPM.htm"
														target=_blank>PPM</a> 
 Volume 1, Chapter 33</B></I></span>,) in accordance with <span style="font-weight: bold; font-style: italic;"><I><B>SDG</B></I></span> 
 Chapter 1. Calculations must be signed and sealed by a professional engineer 
 currently approved to perform Minor Bridge Design under Rule 14-75.</p>

<p class=OutlineA>B. Cast-in-place culverts load ratings must be performed 
 by the licensed professional engineer designer. Show the load rating summary 
 in the Contract Plans. Precast culverts must be load rated by the Contractor’s 
 Engineer of Record (see definition in the Construction Specifications 
 Section 102) and the load rating shown on the approved shop drawings, 
 unless otherwise provided on the <a href="http://www.fdot.gov/roadway/DesignStandards/Standards.htm"
									target=_blank
									style="font-style: italic; font-weight: bold;">Design 
 Standards</a>, Index No. 292.</p>

<p class=OutlineA>&nbsp;</p>

<p align="center" class="whs39"><img src="../storyend_dingbat.gif" x-maintain-ratio="TRUE" width="88px" height="8px" border="0" class="img_whs40"></p>

&nbsp;<br>

<div placeholder id="footer" class="whs1">
 <p class="whs41">&nbsp;</p>
 <p>&nbsp;</p>
</div>
<script language="javascript1.2" type="text/javascript"><!--
kadovTextPopupInit('a3','POPUP199959837');
//--></script><script type="text/javascript" language="javascript1.2">
<!--
if (window.writeIntopicBar)
	writeIntopicBar(0);
//-->
</script>
</body>
</html>
