Failure Report of Sign Board

7/27/2019 Failure Report of Sign Board

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REPORT

ON THE COLLAPSE OF THE 8m SIGN-BOARD

AT 60TH K.M ASUIT-CAIRO ROAD

TO DR. Sherif Mourad

December 2010

Prepared By :

Ahmed Shaban Mahmoud (Master Pre.)


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Inspection & Maintenance 8.0m Sign-board collapse Report 28-DEC-2010

Prepared By: A. Shaban & Refat Taha

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Contents

1 Introduction ................................................................................................................................................. 3

2 Inspection Record........................................................................................................................................ 4

2.1 Inspection notes .................................................................................................................................. 4

2.2 Inspection measurements ................................................................................................................... 5

3 Structural Assessment Cause of Collapse ................................................................................................ 8

3.1 Reaction estimation according to Egyptian code ................................................................................ 8

3.2 Estimation of stress in Anchor Rods .................................................................................................... 9

3.3 Estimation of stress in foundation reinforcement .............................................................................. 9

3.4 Result of assessment ........................................................................................................................... 9

3.5 Cause of collapse ............................................................................................................................... 10

4 Conclusion................................................................................................................................................. 10


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1 Introduction On 29 July 2010 at about 1:00 Pm, the sign-board at 60th Kilometer WESTERN ASUIT-

CAIRO ROAD collapsed.

The sign-board pole had been totally collapsed.

Figure 1: 8.0m sign-board pole had been totally collapsed


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2 Inspection Record2.1 Inspectionnotes

On 5 December 2010 at about 3:00 Pm, an inspection was carried out by Eng. AhmedShaban with Eng. Refat Taha (4 months after collapse).

Structure age estimated to be about 4 years. The structure was totally collapsed due to foundation failure without any noted damage to

any other part of the structure (figure 2).

Some damages were only noted in the top truss carrying the board (seemed to be occurredafter fall down).

A steel tape measure was used to measure the structure dimension.

Figure 2: Collapse due to foundation pedestal failure


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2.2 Inspectionmeasurements The sign-board was 8.0m height (include board height) carrying solid sign with dimension

2.0m x 6.0m.

Pole shaft consist of circular hollow section 600mm out diameter & 5mm thickness. Base connection contained 12 anchor rod 20mm diameter & 350mm embedded length. Base flange is PL 20 thk.x1000x1000. Figure 3 and figure 4 showing pole and base connection dimensions. Figure 5 showing system of the foundation reinforcement. Foundation pedestal is reinforcement concrete reinforcement by 4 L60x6 as main vertical

reinforcement (shown in figure 5)

Figure 3: 8.0m sign-board dimension as measured


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Figure 4: Base connection dimension as measured


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Figure 5: Foundation reinforcement details


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3 Structural AssessmentCause of Collapse3.1 ReactionestimationaccordingtoEgyptiancode

Basic 3-sec gust wind speed = 30 m/sec (108 km/hr)

Topographic Factor, Ct = 1.0 for flat region

K = 1.0 for height < 10.0m & Open exposure

Sign-Board aspect ratio = 6.0 / 2.0 = 3.0

Shaft aspect ratio = 6.0 / 0.6 = 10.0

Sign shape factor Coefficient, Cf = 1.1 + ( 3.0 - 1.0 ) / ( 10.0 - 1.0 ) * 0.1= 1.122

Shaft shape factor Coefficient, Cf = 0.6 + ( 10.0 - 7.0 ) / ( 25.0 - 7.0 ) * 0.1= 0.617

Structure Factor , Cs = 1.0 For structure height less than 60m

q = 0.5 * 1.25 * 302

* 1.0 * 1.0 = 562.5 N/m2

Wind force = CfK q A

Wind on sign = 1.122 * 1.0 * 562.5 * ( 6.0 * 2 ) = 7573 N

Wind on pole shaft = 0.617 * 1.0 * 562.5 * ( 0.6 * 6 ) = 1249 N

Base Moment due to wind = 7.573*7.0 + 1.249 * 3.0 = 56.76 KN.m

Assume Sign-board weight = 800 KG. (include top structure)

Shaft weight = 8 * / 4 * ( 0.62

0.592

)* 7850 = 587 KG.

Down force at base connection = 587 + 800 = 1387 KG = 13.87 KN


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3.2 EstimationofstressinAnchorRods X

2= 8 * 553

2+ 4 * 184

2= 2581896 mm

2

Max. Tension Force in extreme anchor = 56.76 *1000 * 553 / 2581896 - 13.87 / 12

= 11.0 KN

Max. Shear Force in extreme anchor = ( 7.573 + 1.249 ) /12 = 0.735 KN

Tension stress in anchor rod = 11.0 * 1000 / ( / 4 * 202

) = 35 N/mm2

Too small value

Shear stress in anchor rod = 0.735 * 1000 / ( / 4 * 202

) = 2.34 N/mm2

extreme small value

Anchor rod is too safe against applied stress in it.

3.3 EstimationofstressinfoundationreinforcementMax. Tension Force in vertical reinf. = 56.76 / 1.105 / 2 = 25.68 KN (conservative method)

Area of angle L60x6 = 691 mm2

Tension stress in L60x6 = 25.68 * 1000 / 691 = 37.16 N/mm2

Too small value

Allowable tensile stress = 140 N/mm2

(including large factor of safety)

Applied stress


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3.5 Causeofcollapse As shown in figure 6 the vertical reinforcement casted in foundation pedestal without cover. The vertical reinforcement in pedestal became indirect contact with soil. The vertical reinforcement in pedestal had been founded to be totally corroded. The vertical leg reinforcement became divided due to extreme corrosion. Foundation pedestal became acting as plain concrete after total corrosion of reinforcement. The pedestal broken after the absent of vertical reinforcement.

Figure 6: Vertical Reinforcement Leg totally corroded

4 Conclusion Absence of concrete cover around vertical reinforcement cause total corrosion to the vertical

reinforcement which led to total collapse of the pole.


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Failure Report of Sign Board

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