751.14 Steel Superstructure - Revision history

Hoskir: /* 751.14.4.5 Shear Connector Details */ updated per RR3912

2024-07-30T19:14:52Z

751.14.4.5 Shear Connector Details: updated per RR3912

← Older revision		Revision as of 14:14, 30 July 2024
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	'''P/C P/S Panel Forms on Steel Structures'''		'''P/C P/S Panel Forms on Steel Structures'''

	~~Use precast prestressed panels on all tangent steel structures.~~ Evaluate the viability of the use of P/S panels on curved structures on a case by case basis and use or include as an option to a CIP slab where deemed appropriate.		Evaluate the viability of the use of P/S panels on tangent and curved structures on a case by case basis and use or include as an option to a CIP slab where deemed appropriate.

	Whenever panels are used, the minimum top flange width shall be 12" for plate girders and 10" for wide flange beams.		Whenever panels are used, the minimum top flange width shall be 12" for plate girders and 10" for wide flange beams.

Hoskir: /* 751.14.1.3 Optimizing Girder Spacing on Non-Standard Roadways */ updated per RR3912

2024-07-30T18:33:07Z

751.14.1.3 Optimizing Girder Spacing on Non-Standard Roadways: updated per RR3912

← Older revision		Revision as of 13:33, 30 July 2024
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	'''Number of girders.''' For consideration of future stage construction, there may be a minimum number of girders that should be considered.		'''Number of girders.''' For consideration of future stage construction, there may be a minimum number of girders that should be considered.

	'''Maximum ~~Precast Panel~~ Span.''' ~~Since precast~~ panels ~~are the standard, the panel~~ span ~~limit~~ should not be exceeded. For cases where ~~CIP option is~~ used ~~in lieu of panels~~, it is generally recognized that 12 ft girder spacing is a maximum practical limit to allow for future redecking.		'''Maximum Form Span.''' Precast panels and transparent forms have maximum span limits that should not be exceeded. For cases where conventional forms or corrugated steel forms are used, it is generally recognized that 12 ft girder spacing is a maximum practical limit to allow for future redecking.

	'''Vertical Clearance and Deflection Requirements.''' It is expected that fewer girder lines would result in deeper girders. Vertical clearance or deflection constraints may dictate the use of more girder lines than optimum, or a shallower web than optimum.		'''Vertical Clearance and Deflection Requirements.''' It is expected that fewer girder lines would result in deeper girders. Vertical clearance or deflection constraints may dictate the use of more girder lines than optimum, or a shallower web than optimum.

Hoskir: /* 751.14.3.1 Field Bolted Splice Design */ updated per RR 3673

2023-04-03T13:19:47Z

751.14.3.1 Field Bolted Splice Design: updated per RR 3673

← Older revision		Revision as of 08:19, 3 April 2023
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	Uniform bolt patterns are preferred in all cases except that a staggered pattern may be used for flanges that are 14 and 15 inches wide. A staggered bolt pattern reduces the distance between rows of bolts so panels can be placed along the edges of the plate.		Uniform bolt patterns are preferred in all cases except that a staggered pattern may be used for flanges that are 14 and 15 inches wide. A staggered bolt pattern reduces the distance between rows of bolts so panels can be placed along the edges of the plate.

	Bolt tightening clearances may become a problem for thick ~~flanges. Generally~~, if the ~~flange inner splice plate thickness is less than 1~~.~~5” then construction clearances can be assumed to be adequate. Otherwise, a~~ thorough review is required to ensure that a 2.5” diameter socket with 1/16” clearance can be used. If the ~~inner splice plate thickness cannot~~ be ~~reduced~~ the web bolt pattern ~~can be modified~~.		Bolt tightening clearances may become a problem for thick inner flange splice plates or flange bolt patterns that use a narrow bolt gauge, I, across the web. A thorough review is required to ensure that a 2.5” diameter socket with 1/16” clearance can be used. Typically, when bolt tightening clearances are an issue the bolt gauge, I, needs to be increased but the sealing check shall not be violated. If increasing the bolt gauge is not an option the clearance to web bolts, e, shall be increased the minimum extent necessary to maintain a practical uniform web bolt pattern.


	<center>[[Image:751.14 flange bolt patterns-uniform bolt pattern.gif]]</center>		<center>[[Image:751.14 flange bolt patterns-uniform bolt pattern.gif]]</center>

Hoskir: /* 751.14.5.8 Protective Coating Requirements */

2022-12-29T19:13:58Z

751.14.5.8 Protective Coating Requirements

← Older revision		Revision as of 14:13, 29 December 2022
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	===751.14.5.8 Protective Coating Requirements===		===751.14.5.8 Protective Coating Requirements===
	Coating requirements for new steel girder bridge shall be in accordance with [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1080] and [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]. See [[751.1 Preliminary Design#751.1.2.9.2 Steel Girder Options\|EPG 751.1.2.9.2]], [[751.~~6 General Quantities~~#751.6.2.~~11 Structural Steel Protective Coatings (Nonweathering Steel)~~\|EPG 751.6.2.11]] and [[751.6 General Quantities#751.6.2.12 Structural Steel Protective Coatings (Weathering Steel)\|EPG 751.6.2.12]] for additional guidance.		Coating requirements for new steel girder bridge shall be in accordance with [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1080] and [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]. See [[751.1 Preliminary Design#751.1.2.9.2 Steel Girder Options\|EPG 751.1.2.9.2]], [[751.6_General_Quantities#751.6.2.11_Structural_Steel_Protective_Coatings_.28Non-weathering_Steel.29\|EPG 751.6.2.11]] and [[751.6 General Quantities#751.6.2.12 Structural Steel Protective Coatings (Weathering Steel)\|EPG 751.6.2.12]] for additional guidance.

	System G (three-coat system) is the preferred system for both non-weathering and weathering steel structures ([http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]). System G typically is not preferred when overlapping an existing vinyl coating but may be allowed if the existing coating is determined to be in good condition. System G uses a solvent based finish coat which may cause issues when overlapping an existing solvent-based vinyl coating system (System C) because it may re-wet the existing coating and cause delamination of the base coat. If the existing coating is in good condition as determined by paint pull-off tests the intermediate epoxy coating will provide a reliable barrier between the solvent-based coatings. Consult the structural project manager or structural liaison engineer before using System G near existing vinyl coatings.		System G (three-coat system) is the preferred system for both non-weathering and weathering steel structures ([http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]). System G typically is not preferred when overlapping an existing vinyl coating but may be allowed if the existing coating is determined to be in good condition. System G uses a solvent based finish coat which may cause issues when overlapping an existing solvent-based vinyl coating system (System C) because it may re-wet the existing coating and cause delamination of the base coat. If the existing coating is in good condition as determined by paint pull-off tests the intermediate epoxy coating will provide a reliable barrier between the solvent-based coatings. Consult the structural project manager or structural liaison engineer before using System G near existing vinyl coatings.

Hoskir: /* 751.14.5.8 Protective Coating Requirements */ updated per RR 3607

2022-12-21T20:45:13Z

751.14.5.8 Protective Coating Requirements: updated per RR 3607

← Older revision		Revision as of 15:45, 21 December 2022
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	System G (three-coat system) is the preferred system for both non-weathering and weathering steel structures ([http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]). System G typically is not preferred when overlapping an existing vinyl coating but may be allowed if the existing coating is determined to be in good condition. System G uses a solvent based finish coat which may cause issues when overlapping an existing solvent-based vinyl coating system (System C) because it may re-wet the existing coating and cause delamination of the base coat. If the existing coating is in good condition as determined by paint pull-off tests the intermediate epoxy coating will provide a reliable barrier between the solvent-based coatings. Consult the structural project manager or structural liaison engineer before using System G near existing vinyl coatings.		System G (three-coat system) is the preferred system for both non-weathering and weathering steel structures ([http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]). System G typically is not preferred when overlapping an existing vinyl coating but may be allowed if the existing coating is determined to be in good condition. System G uses a solvent based finish coat which may cause issues when overlapping an existing solvent-based vinyl coating system (System C) because it may re-wet the existing coating and cause delamination of the base coat. If the existing coating is in good condition as determined by paint pull-off tests the intermediate epoxy coating will provide a reliable barrier between the solvent-based coatings. Consult the structural project manager or structural liaison engineer before using System G near existing vinyl coatings.

	System G has replaced calcium sulfonate as the preferred overcoating system. To ensure sufficient bond of the existing coating, adhesion pull-off tests shall be performed in accordance with ASTM D4541. If the adhesion test fails, as determined by the engineer of record, then overcoating shall not be allowed and recoating should be considered.		System G has replaced calcium sulfonate as the preferred overcoating system. To ensure sufficient bond of the existing coating, adhesion pull-off tests shall be performed in accordance with ASTM D4541. If the adhesion test fails, as determined by the engineer of record, then overcoating shall not be allowed and recoating should be considered.

Hoskir: Undo revision 52128 by Hoskir (talk)

2022-12-20T19:06:32Z

Undo revision 52128 by Hoskir (talk)

Hoskir: /* 751.14.5.8 Protective Coating Requirements */ updated per RR 3607

2022-12-20T19:04:16Z

751.14.5.8 Protective Coating Requirements: updated per RR 3607

Hoskir: /* 751.14.5.8 Protective Coating Requirements */ updated per RR 3607

2022-12-20T18:56:36Z

751.14.5.8 Protective Coating Requirements: updated per RR 3607

Hoskir: /* 751.14.3.4 Wide Flange Splice Tables */

2022-10-04T20:57:48Z

751.14.3.4 Wide Flange Splice Tables

← Older revision		Revision as of 15:57, 4 October 2022
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	=== 751.14.3.4 Wide Flange Splice Tables ===		=== 751.14.3.4 Wide Flange Splice Tables ===
			Note: In the 15<sup>th</sup> edition of the AISC Steel Construction Manual (2017) the k1 values for many w-shapes increased. The k1 dimension is the distance between the centerline of web and the toe of the fillet into the flange. The inner plates below were designed before this change and as designed may encroach on the toe of the flange fillet. Before using one of the tabulated wide flange splice designs the inner plate shall be checked to ensure it does not encroach on the toe of the flange fillet.

Smithk: Per BR, clarified tension flanges with holes

2022-06-24T13:37:42Z

Per BR, clarified tension flanges with holes

← Older revision		Revision as of 08:37, 24 June 2022
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	Composite regions shall be defined as regions where shear connectors are used to connect the steel section to a concrete deck. Simple spans and horizontally curved girders (see below) are designed as composite throughout.		Composite regions shall be defined as regions where shear connectors are used to connect the steel section to a concrete deck. Simple spans and horizontally curved girders (see below) are designed as composite throughout.

			<div id="Tension Flanges with Holes"></div>
			'''Tension Flanges with Holes'''

	~~'''Compact Section'''~~		Compact Design is not allowed in composite positive flexure regions where holes are located in the tension flange. Similarly, in negative flexure regions where holes are present in the tension flange the girders shall not be proportioned with compact or noncompact webs in accordance with LRFD Appendix A6. The placement of bolted field splices near DL contraflexure points will not preclude the use of compact design or LRFD Appendix A6 in adjacent regions. Girders with holes in the tension flange shall further meet the requirements of LRFD 6.10.1.8 Tension Flanges with Holes.

	Compact Design ~~will be~~ allowed in ~~straight~~ girders if holes ~~drilled~~ in tension flange ~~are investigated for~~ LRFD 6.10.1.8 ~~Net Section Fracture~~.


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	Bolted splices for flexural members shall be designed using slip-critical connections as specified in LRFD 6.13.2.1.1. The connections shall also be proportioned to prevent slip during the erection of the steel and during the casting of the concrete deck.		Bolted splices for flexural members shall be designed using slip-critical connections as specified in LRFD 6.13.2.1.1. The connections shall also be proportioned to prevent slip during the erection of the steel and during the casting of the concrete deck.

	The tensile stress on the flange should be checked ~~for net fracture~~ per LRFD 6.10.1.8.		The tensile stress on the flange should be checked per LRFD 6.10.1.8.

	In bolted slip-critical connections subject to shear, the load is transferred between the connected parts by friction up to a certain level of force that is dependent upon the total clamping force on the faying surfaces and the coefficient of friction of the faying surfaces. As loading is increased to a level in excess of the frictional resistance between the faying surfaces, slip occurs, but failure in the sense does not occur. As a result, slip critical connections are able to resist even greater loads by shear and bearing against the connected material. The strength of the connection is not related to the slip load. Slip resistance, shear resistance and bending shall be computed separately. Any potential greater resistance due to combined effect is ignored.		In bolted slip-critical connections subject to shear, the load is transferred between the connected parts by friction up to a certain level of force that is dependent upon the total clamping force on the faying surfaces and the coefficient of friction of the faying surfaces. As loading is increased to a level in excess of the frictional resistance between the faying surfaces, slip occurs, but failure in the sense does not occur. As a result, slip critical connections are able to resist even greater loads by shear and bearing against the connected material. The strength of the connection is not related to the slip load. Slip resistance, shear resistance and bending shall be computed separately. Any potential greater resistance due to combined effect is ignored.
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	<center>'''Bearing Stiffener -<br/>Diaphragms or Cross Frames Attached<br/>'''(Preferred detail)</center>		<center>'''Bearing Stiffener -<br/>Diaphragms or Cross Frames Attached<br/>'''(Preferred detail)</center>

			<div id="Holes in the tension flange1"></div>
	[[Image:751.145.1.3.jpg\|470px\|center]]		[[Image:751.145.1.3.jpg\|470px\|center]]
	<center>'''Intermediate Bearing Stiffener -<br/>Cross Frames Attached<br/>'''(Optional detail)</center>		<center>'''Intermediate Bearing Stiffener -<br/>Cross Frames Attached<br/>'''(Optional detail<sup>'''1'''</sup>)<br/><sup>'''1'''</sup> Holes in the tension flange restricts girder design in accordance with [[#751.14.2.2 Analysis Methods\|EPG 751.14.2.2 Analysis Methods]]</center>


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	<center>'''Intermediate Diaphragm Connection Plate<br/>'''(Preferred detail)</center>		<center>'''Intermediate Diaphragm Connection Plate<br/>'''(Preferred detail)</center>

			<div id="Holes in the tension flange2"></div>
	[[Image:751.14 Intermediate Diaphragm Connection Plate Optional.jpg\|center\|350px]]		[[Image:751.14 Intermediate Diaphragm Connection Plate Optional.jpg\|center\|350px]]
	<center>'''Intermediate Diaphragm Connection Plate<br/>'''(Optional detail)		<center>'''Intermediate Diaphragm Connection Plate<br/>'''(Optional detail<sup>'''1'''</sup>)<br/><sup>'''1'''</sup> Holes in the tension flange restricts girder design in accordance with [[#751.14.2.2 Analysis Methods\|EPG 751.14.2.2 Analysis Methods]]


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	{\|border="0" cellpadding="3" align="center" style="text-align:center" cellspacing="0"		{\|border="0" cellpadding="3" align="center" style="text-align:center" cellspacing="0"
	\|-		\|-
	\|[[Image:751.14 ~~diaphragm connection details~~.~~gif~~\|~~450px~~]]		\|[[Image:751.14.5.2_diaphragm_details.jpg\|500px]]
	\|-		\|-
	\|		\|
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	\|-		\|-
	\|valign="top" align="right" width="10pt"\|*\|\|align="left" width="350pt" \|When angles are required verify clearance for cross slope.<br/>6 1/4" (Min.) for wide flanges<br/>6 1/2" (Min.) for plate girders		\|valign="top" align="right" width="10pt"\|*\|\|align="left" width="350pt" \|When angles are required verify clearance for cross slope.<br/>6 1/4" (Min.) for wide flanges<br/>6 1/2" (Min.) for plate girders
			\|-
			\|valign="top" align="right" width="10pt"\|**\|\|align="left" width="350pt" \|Holes in the tension flange restricts girder design in accordance with [[#751.14.2.2 Analysis Methods\|EPG 751.14.2.2 Analysis Methods]]
	\|}		\|}
	\|-		\|-

← Older revision		Revision as of 14:06, 20 December 2022
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	===751.14.5.8 Protective Coating Requirements===		===751.14.5.8 Protective Coating Requirements===
	Coating requirements for new steel girder bridge shall be in accordance with [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1080] and [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081].		Coating requirements for new steel girder bridge shall be in accordance with [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1080] and [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]. See [[751.1 Preliminary Design#751.1.2.9.2 Steel Girder Options\|EPG 751.1.2.9.2]], [[751.6 General Quantities#751.6.2.11 Structural Steel Protective Coatings (Nonweathering Steel)\|EPG 751.6.2.11]] and [[751.6 General Quantities#751.6.2.12 Structural Steel Protective Coatings (Weathering Steel)\|EPG 751.6.2.12]] for additional guidance.

	System G (three-coat system) is ~~typically used~~ for non-weathering steel ([http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]).		System G (three-coat system) is the preferred system for both non-weathering and weathering steel structures ([http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]). System G typically is not preferred when overlapping an existing vinyl coating but may be allowed if the existing coating is determined to be in good condition. System G uses a solvent based finish coat which may cause issues when overlapping an existing solvent-based vinyl coating system (System C) because it may re-wet the existing coating and cause delamination of the base coat. If the existing coating is in good condition as determined by paint pull-off tests the intermediate epoxy coating will provide a reliable barrier between the solvent-based coatings. Consult the structural project manager or structural liaison engineer before using System G near existing vinyl coatings.
			System G has replaced calcium sulfonate as the preferred overcoating system. To ensure sufficient bond of the existing coating, adhesion pull-off tests shall be performed in accordance with ASTM D4541. If the adhesion test fails, as determined by the engineer of record, then overcoating shall not be allowed and recoating should be considered.

	System H (three-coat system) is typically used for ~~weathering steel ([http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1080] and [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]) or~~ where ~~coating~~ operations will take place near an existing vinyl coating system (System C).		System H (three-coat system) is typically used when the bond for System G is considered questionable where recoating operations will take place near an existing vinyl coating system (System C). System H uses a waterborne acrylic for the intermediate and finish field coats that does not tend to interfere with the solvent-based vinyl coating.

	System I (two-coat system) ~~shall~~ be used for non-weathering steel ~~only~~ and should be based on the following guidance:		System I (two-coat system) may be used for non-weathering and weathering steel and should be based on the following guidance:

	:(a) System I should be considered in areas where the aesthetics of a coating system over the long term is unusually more critical than System G. While System G and I provide long term protection, System I has excellent gloss retention and UV resistance. System I is a context sensitive design (CSD) solution. CSD follows from project scoping and is subject to the project core team protocols.		:(a) System I should be considered in areas where the aesthetics of a coating system over the long term is unusually more critical than System G. While System G and I provide long term protection, System I has excellent gloss retention and UV resistance. System I is a context sensitive design (CSD) solution. CSD follows from project scoping and is subject to the project core team protocols.
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	::(2) Consider the image consciousness of the surroundings in conjunction with rather than solely the protection of the structure which is equally provided by both systems. Maintenance of either System G or I should be considered the same.		::(2) Consider the image consciousness of the surroundings in conjunction with rather than solely the protection of the structure which is equally provided by both systems. Maintenance of either System G or I should be considered the same.

	:(b) System I is a polysiloxane finish coat that is normally applied directly over an inorganic zinc primer with no intermediate coating. Since the system is a two-coat system, it may be applied in less time which can influence critical path scheduling and impacts to the driving public. For example, it may be possible for a contractor to get in and out quicker than if they were to use a three-coat system. MoDOT coating policy as described in Standard Specification Section 1081 requires different field coating requirements based on the type of bridge crossing. For roadway grade separations, it is required that interior girders have only a single field coat in order to satisfy that all girders on a roadway grade separation bridge have at least two coatings for protection. In the case of System I, the Standard Specifications require that a System G epoxy intermediate field coat be applied to all interior girders and the interior of fascia girders and that the System I polysiloxane finish coating be applied to the exterior of the facia girders only. This is based on a system I polysiloxane coating cost being greater than a system G epoxy coating on a per-gallon cost basis. It also requires that the contractor be given the option to substitute the System I finish coat in place of a System G intermediate coat. If CSD determines that the polysiloxane should to be applied to all girders, then the general notes for coatings and the quantities on the contract plans will need to reflect the revised coating requirements.		:(b) System I is a polysiloxane finish coat that is normally applied directly over an inorganic or organic zinc primer with no intermediate coating. Since the system is a two-coat system, it may be applied in less time which can influence critical path scheduling and impacts to the driving public. For example, it may be possible for a contractor to get in and out quicker than if they were to use a three-coat system. MoDOT coating policy as described in Standard Specification Section 1081 requires different field coating requirements based on the type of bridge crossing. For roadway grade separations, it is required that interior girders have only a single field coat in order to satisfy that all girders on a roadway grade separation bridge have at least two coatings for protection. In the case of System I, the Standard Specifications require that a System G epoxy intermediate field coat be applied to all interior girders and the interior of fascia girders and that the System I polysiloxane finish coating be applied to the exterior of the facia girders only. This is based on a system I polysiloxane coating cost being greater than a system G epoxy coating on a per-gallon cost basis. It also requires that the contractor be given the option to substitute the System I finish coat in place of a System G intermediate coat. If CSD determines that the polysiloxane should be applied to all girders, then the general notes for coatings and the quantities on the contract plans will need to reflect the revised coating requirements.

	:(c) System I is approved for use on state highway projects beginning February 2011. Alternate bidding is encouraged if guideline (a) is not required to be met and with approval of the Structural Project Manager or Structural Liaison Engineer and the project core team.		:(c) System I is approved for use on state highway projects beginning February 2011. Alternate bidding is encouraged if guideline (a) is not required to be met and with approval of the Structural Project Manager or Structural Liaison Engineer and the project core team.

			System G, H or I typically require an inorganic or organic zinc primer per Sec 1081. Inorganic zinc shall be used for new steel fabrication. For recoating operations, organic zinc primer should be considered as a direct replacement for the inorganic zinc required in the specifications. Organic zinc primers require a lower level of surface preparation (SSPC-SP6: commercial blast cleaning vs SSPC-SP10: near white blast cleaning) and are generally easier to apply in the field than inorganic zinc primers. Only organic zinc primers that can provide a Class B slip coefficient are allowed for use in recoating operations.

	See [https://epg.modot.org/index.php?title=751.50_Standard_Detailing_Notes#A4._Protective_Coatings EPG 751.50 A4. Protective Coatings] for standard detailing notes and guidance on how they are used.		See [https://epg.modot.org/index.php?title=751.50_Standard_Detailing_Notes#A4._Protective_Coatings EPG 751.50 A4. Protective Coatings] for standard detailing notes and guidance on how they are used.
	~~<div id="Galvanized nonweathering~~ structural~~"></div>~~
			Epoxy-mastic primers may be used for overcoating lead-based coatings if the existing coating is determined to be in good condition, but this is considered a short-term solution in comparison to System G overcoating. Consult the structural project manager or structural liaison engineer before using epoxy-mastics near existing lead-based coatings.

	Galvanized non-weathering structural steel beams, girders, bracing and diaphragms may be used as required or allowed by alternate, on a case-by-case basis, with approval of the Structural Project Manager or Structural Liaison Engineer and the project core team.		Galvanized non-weathering structural steel beams, girders, bracing and diaphragms may be used as required or allowed by alternate, on a case-by-case basis, with approval of the Structural Project Manager or Structural Liaison Engineer and the project core team.

← Older revision		Revision as of 14:04, 20 December 2022
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	===751.14.5.8 Protective Coating Requirements===		===751.14.5.8 Protective Coating Requirements===
	Coating requirements for new steel girder bridge shall be in accordance with [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1080] and [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]. See [[751.1 Preliminary Design#751.1.2.9.2 Steel Girder Options\|EPG 751.1.2.9.2]], [[751.6 General Quantities#751.6.2.11 Structural Steel Protective Coatings (Nonweathering Steel)\|EPG 751.6.2.11]] and [[751.6 General Quantities#751.6.2.12 Structural Steel Protective Coatings (Weathering Steel)\|EPG 751.6.2.12]] for additional guidance.		Coating requirements for new steel girder bridge shall be in accordance with [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1080] and [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081].

	System G (three-coat system) is ~~the preferred system~~ for ~~both~~ non-~~weathering and~~ weathering steel ~~structures~~ ([http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]). System G typically is not preferred when overlapping an existing vinyl coating but may be allowed if the existing coating is determined to be in good condition. System G uses a solvent based finish coat which may cause issues when overlapping an existing solvent-based vinyl coating system (System C) because it may re-wet the existing coating and cause delamination of the base coat. If the existing coating is in good condition as determined by paint pull-off tests the intermediate epoxy coating will provide a reliable barrier between the solvent-based coatings. Consult the structural project manager or structural liaison engineer before using System G near existing vinyl coatings.		System G (three-coat system) is typically used for non-weathering steel ([http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]).
	System G has replaced calcium sulfonate as the preferred overcoating system. To ensure sufficient bond of the existing coating, adhesion pull-off tests shall be performed in accordance with ASTM D4541. If the adhesion test fails, as determined by the engineer of record, then overcoating shall not be allowed and recoating should be considered.

	System H (three-coat system) is typically used ~~when the bond~~ for ~~System G is considered questionable~~ where ~~recoating~~ operations will take place near an existing vinyl coating system (System C)~~. System H uses a waterborne acrylic for the intermediate and finish field coats that does not tend to interfere with the solvent-based vinyl coating~~.		System H (three-coat system) is typically used for weathering steel ([http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1080] and [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]) or where coating operations will take place near an existing vinyl coating system (System C).

	System I (two-coat system) ~~may~~ be used for non-~~weathering and~~ weathering steel and should be based on the following guidance:		System I (two-coat system) shall be used for non-weathering steel only and should be based on the following guidance:

	:(a) System I should be considered in areas where the aesthetics of a coating system over the long term is unusually more critical than System G. While System G and I provide long term protection, System I has excellent gloss retention and UV resistance. System I is a context sensitive design (CSD) solution. CSD follows from project scoping and is subject to the project core team protocols.		:(a) System I should be considered in areas where the aesthetics of a coating system over the long term is unusually more critical than System G. While System G and I provide long term protection, System I has excellent gloss retention and UV resistance. System I is a context sensitive design (CSD) solution. CSD follows from project scoping and is subject to the project core team protocols.
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	::(2) Consider the image consciousness of the surroundings in conjunction with rather than solely the protection of the structure which is equally provided by both systems. Maintenance of either System G or I should be considered the same.		::(2) Consider the image consciousness of the surroundings in conjunction with rather than solely the protection of the structure which is equally provided by both systems. Maintenance of either System G or I should be considered the same.

	:(b) System I is a polysiloxane finish coat that is normally applied directly over an inorganic ~~or organic~~ zinc primer with no intermediate coating. Since the system is a two-coat system, it may be applied in less time which can influence critical path scheduling and impacts to the driving public. For example, it may be possible for a contractor to get in and out quicker than if they were to use a three-coat system. MoDOT coating policy as described in Standard Specification Section 1081 requires different field coating requirements based on the type of bridge crossing. For roadway grade separations, it is required that interior girders have only a single field coat in order to satisfy that all girders on a roadway grade separation bridge have at least two coatings for protection. In the case of System I, the Standard Specifications require that a System G epoxy intermediate field coat be applied to all interior girders and the interior of fascia girders and that the System I polysiloxane finish coating be applied to the exterior of the facia girders only. This is based on a system I polysiloxane coating cost being greater than a system G epoxy coating on a per-gallon cost basis. It also requires that the contractor be given the option to substitute the System I finish coat in place of a System G intermediate coat. If CSD determines that the polysiloxane should be applied to all girders, then the general notes for coatings and the quantities on the contract plans will need to reflect the revised coating requirements.		:(b) System I is a polysiloxane finish coat that is normally applied directly over an inorganic zinc primer with no intermediate coating. Since the system is a two-coat system, it may be applied in less time which can influence critical path scheduling and impacts to the driving public. For example, it may be possible for a contractor to get in and out quicker than if they were to use a three-coat system. MoDOT coating policy as described in Standard Specification Section 1081 requires different field coating requirements based on the type of bridge crossing. For roadway grade separations, it is required that interior girders have only a single field coat in order to satisfy that all girders on a roadway grade separation bridge have at least two coatings for protection. In the case of System I, the Standard Specifications require that a System G epoxy intermediate field coat be applied to all interior girders and the interior of fascia girders and that the System I polysiloxane finish coating be applied to the exterior of the facia girders only. This is based on a system I polysiloxane coating cost being greater than a system G epoxy coating on a per-gallon cost basis. It also requires that the contractor be given the option to substitute the System I finish coat in place of a System G intermediate coat. If CSD determines that the polysiloxane should to be applied to all girders, then the general notes for coatings and the quantities on the contract plans will need to reflect the revised coating requirements.

	:(c) System I is approved for use on state highway projects beginning February 2011. Alternate bidding is encouraged if guideline (a) is not required to be met and with approval of the Structural Project Manager or Structural Liaison Engineer and the project core team.		:(c) System I is approved for use on state highway projects beginning February 2011. Alternate bidding is encouraged if guideline (a) is not required to be met and with approval of the Structural Project Manager or Structural Liaison Engineer and the project core team.

	System G, H or I typically require an inorganic or organic zinc primer per Sec 1081. Inorganic zinc shall be used for new steel fabrication. For recoating operations, organic zinc primer should be considered as a direct replacement for the inorganic zinc required in the specifications. Organic zinc primers require a lower level of surface preparation (SSPC-SP6: commercial blast cleaning vs SSPC-SP10: near white blast cleaning) and are generally easier to apply in the field than inorganic zinc primers. Only organic zinc primers that can provide a Class B slip coefficient are allowed for use in recoating operations.

	See [https://epg.modot.org/index.php?title=751.50_Standard_Detailing_Notes#A4._Protective_Coatings EPG 751.50 A4. Protective Coatings] for standard detailing notes and guidance on how they are used.		See [https://epg.modot.org/index.php?title=751.50_Standard_Detailing_Notes#A4._Protective_Coatings EPG 751.50 A4. Protective Coatings] for standard detailing notes and guidance on how they are used.
			<div id="Galvanized nonweathering structural"></div>
	Epoxy-mastic primers may be used for overcoating lead-based coatings if the existing coating is determined to be in good condition, but this is considered a short-term solution in comparison to System G overcoating. Consult the structural ~~project manager or structural liaison engineer before using epoxy-mastics near existing lead-based coatings.~~

	Galvanized non-weathering structural steel beams, girders, bracing and diaphragms may be used as required or allowed by alternate, on a case-by-case basis, with approval of the Structural Project Manager or Structural Liaison Engineer and the project core team.		Galvanized non-weathering structural steel beams, girders, bracing and diaphragms may be used as required or allowed by alternate, on a case-by-case basis, with approval of the Structural Project Manager or Structural Liaison Engineer and the project core team.

← Older revision		Revision as of 13:56, 20 December 2022
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	===751.14.5.8 Protective Coating Requirements===		===751.14.5.8 Protective Coating Requirements===
	Coating requirements for new steel girder bridge shall be in accordance with [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1080] and [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081].		Coating requirements for new steel girder bridge shall be in accordance with [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1080] and [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]. See [[751.1 Preliminary Design#751.1.2.9.2 Steel Girder Options\|EPG 751.1.2.9.2]], [[751.6 General Quantities#751.6.2.11 Structural Steel Protective Coatings (Nonweathering Steel)\|EPG 751.6.2.11]] and [[751.6 General Quantities#751.6.2.12 Structural Steel Protective Coatings (Weathering Steel)\|EPG 751.6.2.12]] for additional guidance.

	System G (three-coat system) is ~~typically used~~ for non-weathering steel ([http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]).		System G (three-coat system) is the preferred system for both non-weathering and weathering steel structures ([http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]). System G typically is not preferred when overlapping an existing vinyl coating but may be allowed if the existing coating is determined to be in good condition. System G uses a solvent based finish coat which may cause issues when overlapping an existing solvent-based vinyl coating system (System C) because it may re-wet the existing coating and cause delamination of the base coat. If the existing coating is in good condition as determined by paint pull-off tests the intermediate epoxy coating will provide a reliable barrier between the solvent-based coatings. Consult the structural project manager or structural liaison engineer before using System G near existing vinyl coatings.
			System G has replaced calcium sulfonate as the preferred overcoating system. To ensure sufficient bond of the existing coating, adhesion pull-off tests shall be performed in accordance with ASTM D4541. If the adhesion test fails, as determined by the engineer of record, then overcoating shall not be allowed and recoating should be considered.

	System H (three-coat system) is typically used for ~~weathering steel ([http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1080] and [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=14 Sec 1081]) or~~ where ~~coating~~ operations will take place near an existing vinyl coating system (System C).		System H (three-coat system) is typically used when the bond for System G is considered questionable where recoating operations will take place near an existing vinyl coating system (System C). System H uses a waterborne acrylic for the intermediate and finish field coats that does not tend to interfere with the solvent-based vinyl coating.

	System I (two-coat system) ~~shall~~ be used for non-weathering steel ~~only~~ and should be based on the following guidance:		System I (two-coat system) may be used for non-weathering and weathering steel and should be based on the following guidance:

	:(a) System I should be considered in areas where the aesthetics of a coating system over the long term is unusually more critical than System G. While System G and I provide long term protection, System I has excellent gloss retention and UV resistance. System I is a context sensitive design (CSD) solution. CSD follows from project scoping and is subject to the project core team protocols.		:(a) System I should be considered in areas where the aesthetics of a coating system over the long term is unusually more critical than System G. While System G and I provide long term protection, System I has excellent gloss retention and UV resistance. System I is a context sensitive design (CSD) solution. CSD follows from project scoping and is subject to the project core team protocols.
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	::(2) Consider the image consciousness of the surroundings in conjunction with rather than solely the protection of the structure which is equally provided by both systems. Maintenance of either System G or I should be considered the same.		::(2) Consider the image consciousness of the surroundings in conjunction with rather than solely the protection of the structure which is equally provided by both systems. Maintenance of either System G or I should be considered the same.

	:(b) System I is a polysiloxane finish coat that is normally applied directly over an inorganic zinc primer with no intermediate coating. Since the system is a two-coat system, it may be applied in less time which can influence critical path scheduling and impacts to the driving public. For example, it may be possible for a contractor to get in and out quicker than if they were to use a three-coat system. MoDOT coating policy as described in Standard Specification Section 1081 requires different field coating requirements based on the type of bridge crossing. For roadway grade separations, it is required that interior girders have only a single field coat in order to satisfy that all girders on a roadway grade separation bridge have at least two coatings for protection. In the case of System I, the Standard Specifications require that a System G epoxy intermediate field coat be applied to all interior girders and the interior of fascia girders and that the System I polysiloxane finish coating be applied to the exterior of the facia girders only. This is based on a system I polysiloxane coating cost being greater than a system G epoxy coating on a per-gallon cost basis. It also requires that the contractor be given the option to substitute the System I finish coat in place of a System G intermediate coat. If CSD determines that the polysiloxane should to be applied to all girders, then the general notes for coatings and the quantities on the contract plans will need to reflect the revised coating requirements.		:(b) System I is a polysiloxane finish coat that is normally applied directly over an inorganic or organic zinc primer with no intermediate coating. Since the system is a two-coat system, it may be applied in less time which can influence critical path scheduling and impacts to the driving public. For example, it may be possible for a contractor to get in and out quicker than if they were to use a three-coat system. MoDOT coating policy as described in Standard Specification Section 1081 requires different field coating requirements based on the type of bridge crossing. For roadway grade separations, it is required that interior girders have only a single field coat in order to satisfy that all girders on a roadway grade separation bridge have at least two coatings for protection. In the case of System I, the Standard Specifications require that a System G epoxy intermediate field coat be applied to all interior girders and the interior of fascia girders and that the System I polysiloxane finish coating be applied to the exterior of the facia girders only. This is based on a system I polysiloxane coating cost being greater than a system G epoxy coating on a per-gallon cost basis. It also requires that the contractor be given the option to substitute the System I finish coat in place of a System G intermediate coat. If CSD determines that the polysiloxane should be applied to all girders, then the general notes for coatings and the quantities on the contract plans will need to reflect the revised coating requirements.

	:(c) System I is approved for use on state highway projects beginning February 2011. Alternate bidding is encouraged if guideline (a) is not required to be met and with approval of the Structural Project Manager or Structural Liaison Engineer and the project core team.		:(c) System I is approved for use on state highway projects beginning February 2011. Alternate bidding is encouraged if guideline (a) is not required to be met and with approval of the Structural Project Manager or Structural Liaison Engineer and the project core team.

			System G, H or I typically require an inorganic or organic zinc primer per Sec 1081. Inorganic zinc shall be used for new steel fabrication. For recoating operations, organic zinc primer should be considered as a direct replacement for the inorganic zinc required in the specifications. Organic zinc primers require a lower level of surface preparation (SSPC-SP6: commercial blast cleaning vs SSPC-SP10: near white blast cleaning) and are generally easier to apply in the field than inorganic zinc primers. Only organic zinc primers that can provide a Class B slip coefficient are allowed for use in recoating operations.

	See [https://epg.modot.org/index.php?title=751.50_Standard_Detailing_Notes#A4._Protective_Coatings EPG 751.50 A4. Protective Coatings] for standard detailing notes and guidance on how they are used.		See [https://epg.modot.org/index.php?title=751.50_Standard_Detailing_Notes#A4._Protective_Coatings EPG 751.50 A4. Protective Coatings] for standard detailing notes and guidance on how they are used.
	~~<div id="Galvanized nonweathering~~ structural~~"></div>~~
			Epoxy-mastic primers may be used for overcoating lead-based coatings if the existing coating is determined to be in good condition, but this is considered a short-term solution in comparison to System G overcoating. Consult the structural project manager or structural liaison engineer before using epoxy-mastics near existing lead-based coatings.

	Galvanized non-weathering structural steel beams, girders, bracing and diaphragms may be used as required or allowed by alternate, on a case-by-case basis, with approval of the Structural Project Manager or Structural Liaison Engineer and the project core team.		Galvanized non-weathering structural steel beams, girders, bracing and diaphragms may be used as required or allowed by alternate, on a case-by-case basis, with approval of the Structural Project Manager or Structural Liaison Engineer and the project core team.