STR654- Lecture 5 - 29 October 2013

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SPECIAL TOPICS IN STEEL STRUCTURES – STR 654

STEEL STRUCTURE ERECTION

By

Hazem M. Ramadan

October 13 1

Hazem M. Ramadan

Associate Professor, Steel Structures and BridgesStructural Engineering DepartmentCairo University

CONTENTS

Field Bolts Connections

Field Welded Connections

Quali

Inspection Testing Plan [ITP]

Inspector Check List

Cladding Erection

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Rivets

Bolts

A- FIELD BOLTS CONNECTIONS

Bolts› Bearing Type

› Friction Type (Slip Resistant)

Common Bolts Grades

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Bolts Components Bolt


Bolt

Nut

Washer

› Threaded Length (important for design)

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Bearing Type Bolts› Resists shear by:


› Resists shear by: shear strength of bolt shaft (gross / net)

Bearing between bolt shaft and steel plates

› Bolts used: Ordinary

High Strength

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High Strength

Friction Type Bolts› Also known as slip critical


› Also known as slip-critical

› Clamping action created by bolt pre-tension

› Shear forces are resisted by friction between steel plate surfaces and bolts are not subjected to shear or bearing.

› Proper tightening is essential to ensure developing adequate clamping force

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› Frictional resistance is effective over a relatively large area, reducing local stresses on the net section at the hole.

› High initial tension prevents the nuts from loosening.

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A- FIELD BOLTS CONNECTIONSFriction Bolts Tightening Methods

Tightening Methods› Turn of nut method› Turn of nut method

› Torque wrench (calibrated wrench).

› Direct Tension Indicator (protrusion compressed to specified gap)

› Tension control (Shear-off head)

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Turn of Nut Method› Snug-tight is reached with a few impacts of an impact


g g p pwrench, or the full effort of a man using an ordinary spud wrench

› All bolts shall be placed in the holes prior to tightening› Contractor must snug-tighten enough bolts to ensure full

contact› During tightening the “fixed” head shall not rotate (no

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› During tightening, the fixed head shall not rotate (no wheeling)

› Contractor shall demonstrate that routine procedure properly establishes design requirement

Eng.Ahmed

Stamp

5

Turn of Nut Method› Match-marking the nut with the bolt point after snug-


g p gtightening.

› Apply specified turns systematically› Inspector: observe testing representative samples, and

survey ongoing work› Inspector shall mark the bolts after they are snugged and

after they are tightened

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after they are tightened› If any nut or bolt head is turned using the job inspecting

torque, all bolts in the connection should be tested accordingly

Turn of Nut Method› Egyptian Code


α = 90o + t + d

t is thickness of connected parts (mm), d is the bolt diameter ( mm).

› AISC

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Eng.Ahmed

Stamp

Eng.Ahmed

Rectangle

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Torque Wrench› The toque wrench shall be calibrated [Certificate] before


› The toque wrench shall be calibrated [Certificate] beforeusage in the presence of the inspector

› Torque values must be determined from tables or equationsmentioned in the approved Code

› The rotation between the bolt and the nut need not begreater than the Turn of the Nut rotation value

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› At least three complete fastener assemblies shall be testedfor each combination of bolt length, diameter, grade, …etc

› The calibrated wrench must be re-used to re-torquepreviously tightened bolts.

Torque Wrench› If there are several bolts in a single connection minor


› If there are several bolts in a single connection, minorseparation is acceptable at the beginning.

› After tightening of subsequent bolts, the separation shalldisappear, leaving the tension in the first bolt less thanrequired.

› Hardened washers shall be installed under the element to beturned in tightening

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turned in tightening.› Several cycles may be necessary to ensure all bolts reach the

torque established for the day.

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Torque Wrench Types› Manual or Hydraulic in accordance to the project nature


› Manual or Hydraulic in accordance to the project nature.

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Torque Wrench› Egyptian Code


gyp

Ma = k d T

Ma is the applied torque.

k is a coefficient (about 0.2).

d is the bolt diameter.

T is the bolt pretension force.

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Direct Tension Indicator› The DTI with protrusion

compressed onl indicates that


compressed only indicates thatenough tension was applied at sometime.

› Specified tension is assured only ifthe bolts are systematically snuggedand tightened.

› Tightening of individual bolts withDTI shall not be accomplished in a

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DTI shall not be accomplished in asingle continuous operation.

Tension Control (Sheared Off Head)› The sheared-off splined end only indicates that enough


p y gtorque was applied to fracture the break neck.

› Specified tension is assured only if the bolts aresystematically snugged and tightened.

› Tightening to final tension and shearing the break neckshall not be accomplished in a single continuousoperation

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operation.

› The use of specific and proper lubricant.

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Bolts have to conform to the contract documents (ensure that the proper bolt grade is used)

A-FIELD BOLTS CONNECTIONSGeneral Procedure

Steel contact surfaces have to be free of dirt, dust, mill scale or any other foreign material

Ensure solid contact between the contact surfaces

Verify bolt installation method in accordance with specifications

Receipt of fasteners:

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p

Test certificate.

Lot number.

Accessories (nuts and washer) of same type

Proper storage

Get only the number of bolts for each shift.

Tension measuring device.


g

Reaming of poorly aligned holes.

Record major misalignment.

Exclude corroded or dirty bolts.

Fastener assemblies shall demonstrate an installation tension 5% higher than min. required tension.

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Bolts shall be brought to a snug-tight position.

Begin snug-tightening at the most rigid part of the connection and progress to the free edge.

After snug-tightening, full tightening to proceed similarly.

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Continuous surveillance by inspector.

Tension higher than specified is not a reason for rejection.


g p j

HSB must not be re-used.

Bevel washers are required if the surface of connected parts slopes more than 5% (1:20).

At splice location, bolts are to be tightened from the center outwards.

HSB b ti ht d b t r i ith r th t r th

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HSB may be tightened by turning either the nut or the head, provided a washer is used at the tightening end.

HSB must never be replaced by ordinary bolts.

All bolts (100%) must be checked at splice locations.

Specify codes and standards to be followed for fieldwelding

B-FIELD WELDED CONNECTIONS

welding

Weld procedure specifications must be submitted andapproved

Welders must be qualified

Non prequalified joints need to be qualified by testing

All ld b f h ldi d

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All welders must be aware of the welding procedurespecifications

Contact surfaces shall be cleaned prior to welding

Eng.Ahmed

Stamp

Eng.Ahmed

Typewriter

This is only in case of (HEX) head Bolts Round Plane Head Bolts Need to be tightened from the nut side.

Eng.Ahmed

Typewriter

Otherwise it will fail

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Welded parts shall be aligned complying with thetolerances specified in the mentioned codes and

B-FIELD WELDED CONNECTIONS

pspecifications

Specify weather and environmental conditions whenfield welding is not allowed

Weld consumables shall be purchased, stored, dried,and used according to the specifications

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g p

Preheat shall be applied when applicable as perspecifications

Field painting / touch up shall be performed

A quality control plan should be prepared and carefullyfollowed:

C- QUALITY CONTROL

Erection method statement

Inspection and Testing Plan (ITP)

Erection inspection check list (EICL)

Procedures & inspection forms as stated in the ITP

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Bolt tightening procedure

Paint touch up procedure

Site organization chart including dedicated safetyofficer and Quality Control engineer

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D- INSPECTION TESTING PLAN

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E- INSPECTOR CHECK LIST Review and understand erection procedure Review false work and traffic plan E l f b Ensure complete survey of superstructure by an

independent surveyor Check alignment and levels of bearings Check anchor bolt locations Check surface finish of concrete. Minor grinding /

chipping may be required Check required shims for level adjustment

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Check required shims for level adjustment Ensure pockets are fully grouted with an approved grout

material (where required) Check temperature when grouting according to supplier

requirements

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F- CLADDING ERECTION Preparation Touch up any paint damage of the steel

structure prior to erecting the cladding. Install the base angle (in case side cladding

extends to the ground). Use temporary supports (if sag rods are not

used or not sufficient to get the side girts inhorizontal position.

Prepare erection tools Lay down the roof panels on the roof (make

sure of the applied load)

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pp )

F- CLADDING ERECTION Installation of cladding Use chalk line to mark the position of the

girts on the cladding.girts on the cladding. Make sure that the wall sheeting is

straight and connect it to the top purlin,base angle, and side girts.

Install the roof sheeting as per theprearranged sequence in the drawings

Bead mastic should be carefully installedbetween the cladding layers.

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g y

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F- CLADDING ERECTION Important Notes Stay away from high

corrugationscorrugations. Brush off any metal chips. Workers should use soft

footwear to avoid damagingthe cladding.

Walk on the sheet valleys incontact with the purlins

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F- CLADDING ERECTION Important Notes

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STR654- Lecture 5 - 29 October 2013

Documents

Transcript of STR654- Lecture 5 - 29 October 2013