Structural Investigation Report (Sign Board)

8/2/2019 Structural Investigation Report (Sign Board)

1/12


2/12

SUMMARY

On 06 July 2008, Royal Commission for Jubail and Yanbu (RC), Madinat Al-

Jubail Al-Sinaiyah, has reported noticeable vertical deflection for the overhead

Road Sign on TS1 at exit 5B South Bound. The mentioned signs structure is a

single post cantilever type Trussed-Column Frame Steel Structure. The cantilever

span of the signs structure is equal to 13.0 m extending across the street. Asprovided by RC (Jubail) Road Department, the estimated vertical deflection of the

cantilever arm, at 7.0 m from its post, is about 200 mm. In addition it has beennoticed that the vertical deflection is started around the first 2.70 m from its post.

Based on the E-Mail provided by RC (Jubail) on 08 July 2008, regarding the

above subject, SAUDCONSULT Structural Engineers reviewed the structuraldesign drawings (provided by RC) and made visual site inspection for the

aforementioned signs structure on 26 July 2008, accompanied with the RC

(Jubail) structural engineer.

The aim of this report is to provide an insight on the existing structural conditionof the mentioned signs structure and to present a preliminary proposal for its

structural design to satisfy the strength/serviceability requirements.

The report describes/discuses (briefly) the designed structural system adopted in

comparison with our finding during site inspection, the possible reasons for theabove mentioned excessive vertical deflection and finally presents a preliminary

structural design proposal for the subject signs structure to keep safety,

enhancing its stiffness/stability and limiting deflection.

1. REVIEW OF THE STRUCTURAL DESIGN DRAWINGS/EXISTING

SIGNS STRUCTURE CONDITIONS

Based on the available data shown on the structural designed drawings, the

structural system of the subject sign is composed of cantilever type Trussed-Column Steel Frame. The cantilever span of the frame is composed of steel truss(N-system configuration) of 13.0 m span extending across the street. Figure (1)

shows the general layout of the designed structural system of the mentioned sign.

However, based on the site visual inspection it has been found out that the verticaland diagonal members of the main trusses have been provided (only) on the first

panel and have not been provided on the remaining panels of the truss, as shown

in Figure 2. Furthermore, it has been noticed that the existing cross section of thetop and bottom chords of the truss member is different from that provided on the

structural drawings. In addition, the dimensions of existing sign board are larger

than that provided by the designed drawings and consequently, the expected

applied wind effect on the signs structure shall be larger than that adopted by thedesign drawings.

Mathematical models using STAAD.Pro software computer program have been

adopted to simulate the subject signs structure/existing conditions of the structureload considering the existing structural system of the signs structure and the

proposed/designed structural system. The cantilever arm of the proposed/designed

structural system (see Figure 1) has been analyzed as a three dimensional truss.

1 of 11


3/12

SIGNAGE (FIGURE-1)3D VIEW

Software licensed to [LZ0 + LND]

Job Title

Client

Job No Sheet No Rev

Part

Ref

By Date Chd

File Date/Time

1

ROYAL COMMISION

PROPOSED DESIGN

AF 03-Aug-08 KF

04-Aug-2008 11:52Str2A.std

Print Time/Date: 04/08/2008 11:53 Print Run 1 ofSTAAD.Pro for Windows Release 2005

Load 1

XY

Z

2 of 11


4/12

EXITING SIGN BOARD (FIGURE-2)


Job Title

Client

Job No

Part

Ref

By

FileROYAL COMMISION

EXIS

AF

Str2A

Print Time/Date: 05/08/2008 09:03 STAAD.Pro for Windows Release 2005


5/12

The truss members have been simulated by Frame elements. The torsion/bendingstiffness of the adopted frame elements has been released to simulate the truss

member behavior. The top and bottom connections between the truss and its steel

post have been simulated by Pinned supports. However, based on the structuraldetail of the top connection between the truss and its post, the vertical

displacement of the above mentioned top pinned supports has been released.On the other hand, the existing structural system of the cantilever arm of

mentioned sign may not be appropriate to be simulated as space truss, see Fig. 2.As can be seen from the general layout of the existing structural system of the

signs cantilever arm, the slenderness ratios of the top and bottom chords are

exceeding the acceptable limits and the main loads are acting along its spans.Accordingly, the existing structural system of the cantilever arm of mentioned

sign has been simulated as space Frame considering the same support conditions

as stated above.

The existing post base connection and its (post) connections to the cantilever armstructure have been visually inspected and no defects have been noticed. In

addition structural design review for the mentioned (truss/post) connections has

been carried out.

2. STRUCTURAL MODEL RESULTS, ANALYSIS AND DISCUSSION

Based on the results of the mathematical models analysis, it can deduce the

following:

a) The estimated stresses on the existing steel structure of the cantilever armare exceeding the allowable limits, see Figure 3.

b) The estimated maximum elastic deflection on the existing steel structureof the signs cantilever arm is equal to 247 mm, see Table 1. It can benoticed that the estimated maximum elastic deflection is close to its

corresponding existing deflection. It may be worth mentioning that thevertical steel members provided for supporting the sign board have played

a significant role on reducing the mentioned deflection. As can be seen

from Table 2, the expected deflection without the aforementioned

members may exceed 523 mm.

c) The stiffness of the existing steel structure of the sign cantilever arm hasbeen reduced drastically at the end of the orphan panel provided (about

2.60 m from the post). Accordingly, it seems logic for the existing

deflection to be started at this location as mentioned by RC (Jubail) Road

Department.

d) Figures 4 and 5 show a preliminary structural design proposal for the signcantilever arm of the subject road sign to keep safety, enhancing its

stiffness/stability and limiting deflection. In addition, the stiffness/rigidityof base/posttruss connections shall be enhanced by adopting the

following:

i. The use of H.S.B., type 10.9 for the post-truss connections.

4 of 11


6/12

EXITING SIGN BOARD (FIGURE-3)


Job Title

Client

Job No

Part

Ref

By

FileROYAL COMMISION

EXIS

AF

Str2A


0.951 1

0.727 1.150.498 1.4

1.370.635

11.4

1.190.342

0.7911.06

0.7990.778 0.563

0.94

0.777 0.789

0

0.837 0.68

0.833

1.32

0.849 0.471

1.06

0.507 1.46

0.4281.67 0.982

1.66 1.370.689

1.87 1.04

0.615

0.387 1.06

1.12

0.93

0.525 2.68

2.311.1

0.395 0.67

2.28

0.51 0.719

1.11

1.1e+003

2.89

0.708

1.4

0.985

3.55

0.394

1.6

1.42e+003

2.01 1.15

1.09

0.586 4.61

1.25

1.030.895

0.924 2.42

1.37e+003

1.52

1.42

1.71 0.804

0.537

1.29 1.2

2.46

2.010.674 1.03

0.802

1.78e+0031.562.38

1.51

0.541

1.42

0.499 0.875

0.564

2.27

2.24

2.71

0.624

2.46e+003

2.17

2.18 1.36

0.553

1.26

1.86 3.122.52e+003

0.76

2.28

0.373

1.372.02

0.532

1.55e+0032.1

0.497

1.681.25

0.977

1.67e+0031.29

1.66


7/12

EXITING SIGN BOARD (TABLE-1)


Job Title

Client

Job No Sheet No Rev

Part

Ref

By Date Chd

File Date/Time

1

ROYAL COMMISION

03-Aug-08

04-Aug-2008 10:14Str2A-1.std


Node Displacement SummaryNode L/C X

(mm)

Y

(mm)

Z

(mm)

Resultant

(mm)

rX

(rad)

rY

(rad)

rZ

(rad)

Max X 22 6:0.9DL+WL 4.992 -173.849 -168.805 242.371 -0.041 0.015 -0.007

Min X 57 3:WL -4.670 -27.519 -156.603 159.071 -0.040 0.016 -0.002

Max Y 38 4:DL+LL -0.100 2.795 -0.218 2.806 0.001 0.000 -0.001

Min Y 35 5:DL+LL+WL -1.188 -247.109 -96.548 265.303 -0.042 0.008 0.006

Max Z 10 1:DL -0.116 -191.450 3.663 191.485 -0.003 -0.001 -0.008

Min Z 21 6:0.9DL+WL -4.655 -200.526 -168.809 262.162 -0.044 0.016 -0.006

Max rX 4 4:DL+LL -0.190 -48.518 -0.240 48.519 0.014 -0.000 -0.026

Min rX 59 5:DL+LL+WL -4.556 -229.992 -142.155 270.417 -0.048 0.016 -0.015

Max rY 61 6:0.9DL+WL 4.901 -135.459 -118.667 180.153 -0.041 0.017 -0.017

Min rY 36 4:DL+LL 0.349 -218.220 -0.310 218.221 -0.003 -0.002 0.004Max rZ 30 4:DL+LL -0.181 -52.925 1.775 52.955 0.006 0.000 0.011

Min rZ 67 5:DL+LL+WL -3.924 -95.974 -60.121 113.318 -0.024 0.015 -0.033

Max Rst 21 5:DL+LL+WL -4.558 -247.107 -166.875 298.211 -0.043 0.016 -0.006

6 of 11


8/12

EXITING SIGN BOARD (TABLE-2)


Job Title

Client

Job No Sheet No Rev

Part

Ref

By Date Chd

File Date/Time

1

ROYAL COMMISION

EXISTNG SIGNAGE

AF 03-Aug-08 KF

04-Aug-2008 10:56Str2A-2.std


Node Displacement SummaryNode L/C X

(mm)

Y

(mm)

Z

(mm)

Resultant

(mm)

rX

(rad)

rY

(rad)

rZ

(rad)

Max X 22 6:0.9DL+WL 4.856 -384.140 -168.232 419.392 -0.036 0.013 -0.014

Min X 57 3:WL -4.713 -22.154 -159.620 161.219 -0.041 0.016 -0.001

Max Y 74 5:DL+LL+WL 1.486 6.267 -7.361 9.780 -0.005 0.007 -0.000

Min Y 35 5:DL+LL+WL 2.665 -522.510 -99.246 531.858 -0.039 0.001 0.014

Max Z 22 2:LL -0.092 -71.141 3.470 71.226 0.003 -0.001 -0.004

Min Z 21 6:0.9DL+WL -4.563 -409.615 -168.242 442.844 -0.042 0.015 -0.013

Max rX 53 4:DL+LL -0.073 -312.002 -2.240 312.010 0.092 0.001 -0.061

Min rX 36 6:0.9DL+WL 4.392 -384.145 -99.158 396.760 -0.045 0.003 0.005

Max rY 58 6:0.9DL+WL 4.846 -363.717 -152.235 394.321 -0.040 0.016 -0.025

Min rY 36 4:DL+LL -0.262 -501.781 -1.148 501.782 -0.001 -0.010 0.009Max rZ 35 5:DL+LL+WL 2.665 -522.510 -99.246 531.858 -0.039 0.001 0.014

Min rZ 65 5:DL+LL+WL -4.152 -238.453 -76.589 250.486 -0.025 0.015 -0.067

Max Rst 21 5:DL+LL+WL -4.407 -522.500 -164.822 547.898 -0.040 0.015 -0.018

7 of 11


9/12


10/12

PROPOSED SIGN BOARD (FIGURE-5)


Job Title

Client

Job No

Part

Ref

By

FileROYAL COMMISION

PRO

AF

Str2A


0.0746 0

0.125 0.05710.0171 0.0

0.129

0.106

0.1540.103

0.103

0.09940.129

0.0694

0.1830.103

0.0171

0.124

0.0867

0.1290.278 0.0223

0.117

0.0231

0.103

0.141 0.149

0.137

0

0.177

0.058

0.175

0.0676

0.0675

0.319

0.342

0.0284 0.17

0.141

0.233 0.0247

0.0657

0.2080.357 0.177

0.0112

0.292 0.008650.0779

0.124

0.414 0.141

0.233

0.00911 0.241

0.141

0.0506

0.0675

0.201

0.127

0.147

0.292

0.4620.16

0.0598

0.0899 0.233

0.0426

0.288

0.324

0.0926

0.201

0.527

0.0579

0.508

0.18

0.16

0.00911

0.42

0.325

0.135

0.15

0.201

0.527

0.576 0.0223

0.134

0.27

0.0426

0.139 0.362

0.105

0.420.21

0.175

0.0644

0.334

0.527

0.112

0.616

0.154

0.337 0.197

0.139

0.628 0.286

0.0773

0.3640.653 0.175

0.0483

0.787 0.2710.471

0.141

0.139

0.628

0.394

0.066

0.384

0.112

0.604

0.0891

0.787

0.0815

0.562 0.628

0.0978

0.0999

0.4971.1

0.0706

0.751

0.0162

0.8760.629

0.0711

1.10.939

0.0978

0.8760.786

0.0875

1.1

0.946


11/12

ii. Stiffened Rectangular Seat Bracket for the lower post-trussconnection

iii. Vertical stiffeners to the post base connection.However, the structural details of these connections shall be subject to

final design

3. CONCLUSION

i. The estimated stresses on the existing steel structure of the cantilever armof the subject road sign are exceeding the allowable limits.

ii. A preliminary structural design for the aforementioned signs cantileverarm has been proposed.

iii. Recommendations for enhancing the base/column-truss connection havebeen proposed.

iv. Accordingly, the existing cantilever arm structure shall be disconnectedand replaced as soon as possible, as per the proposal/recommendationpresented above.

v. The estimated cost of the proposed cantilever arm structure per sign isprovided on Table-3.

10 of 11


12/12

TA

Contract No. 082-C35

Pay Item # Pay Item Description Cantilever sign

UNIT/ Ea

Unit Quantity Unit Price

Demolition of existing str. LS 1 10,000 Removal of existing board, transportation etc.

Str. Steel

Truss Frame & Bracing members Ton 6.00 16,000

Cladding M 90 450

Misc.LS 1 10,000

Sign Painting with Writing LS 1 10,000

Electrical Works

Ligthting fixtures, Cable, Conduits etc. LS 1 35,000

Add Contractor's profit @ 30%

Say SR. 260,000/- per Ea

COST BREAKUP

Contract Title Tareeg Sarie-1

Description Total Cost S R. Remarks

In case of utilization of existing fixtures this amoumay be reduced.

Unit Cost for One Sign 201,500.00

10,000.00

96,000.00

40,500.00

10,000.00

Strengthening the connections,fixing of existing

walkway structure etc.

60,450.00

261,950.00

10,000.00

35,000.00

11 f 11

Date post:	06-Apr-2018
Category:	Documents
Upload:	irfan-ali
View:	217 times
Download:	2 times

Structural Investigation Report (Sign Board)

Documents