Instructions, queries, and non-conformances are issued only for the purpose of recording any clarification or interpretation of the Contract Documents or giving direction on problems resulting from unanticipated occurrence on site. They do not authorize any change in the terms of the Contract relating to Price or Schedule. These instructions are subject to the provisions of the terms of the Contract and unless provided for in the Contract and expressly co-authorized by LAMATA, will not change the contract.

LAGOS RAIL MASS TRANSIT PROJECT (Blue Line)

Site Special Report Document Number: NXT/LRT/BLP/SSR/ /0004 Location: National Theatre Yard

Contractor: CCECC Originator: Izu Nnaji

Consultant: Nexant Date: 24th of April, 2012

Subject: REPORT ON STATIC LOAD TEST ON T-BEAM 30Z2-074

Historical Background:

Very serious cracks were observed on precast prestressed bridge T-beam number 30Z2-074 after its mould was stripped off on Wednesday the 8th of February 2012. The beam was manufactured on the 7th of February 2012 and stripped on the 8th of February 2012. Concrete compressive strength test on day-old cubes sampled during the production of the beam certified it adequate for stripping operations at 74% of designed strength as against a minimum of 54% being used. Most of the cracks were so big that they could not be measured. The cracks and defects were observed all around the beam, but the major ones were on the mid-span clapboards on both the north and south sides of the beam, as well as the second transverse connection support boards on both the north and south sides of the beam. Please see photos 1 to 8 showing some of the cracks and defects observed. The issue attracted the management of both LAMATA and Nexant who were on site for a meeting and were dismayed at CCECC's effort to conceal the cracks. CCECC was instructed not to send the beam out to the bridge site for erection until technical investigations were completed on the beam and the beam certified adequate for use. Summary of Test: The Static Load Test on T-beam 30Z2-074 was carried out at the National Theatre Yard between 10.00hrs and 14.00hrs on Monday, the 23rd of April 2012. The test was based on the Chinese Standard as stipulated in TB/T 2092-2003 (Post-tensioned precast concrete simple-supported girder for railway bridge pro-stress). Both the Standard and the approved Method Statement were made available to all parties long before the test was carried out. However, in summary, the Static Beam Load Test is about the application of a distributed load on the beam via five equally-spaced loading jacks and applied according to a particular loading sequence, after which the beam is examined and calculations made to ascertain the effect of the load on the beam. The beam is usually not loaded to destruction but only to the designed anti-crack coefficient that the beam is expected to bear. There are two major empirical indices for judging the acceptance of the beam. Cracks: Before the test, the lower flange and the underside of the beam are inspected for cracks and all identified cracks are measured and marked with blue markers. After each grade of loading, the beam is again examined for new cracks and/or opening of old cracks, and these are marked with red markers. If after the maximum load has rested on the beam for the specified 20 minutes, cracking is observed at the bottom of the lower edge of girder body, or at the sides of the lower flange extending to the edge of the girder bottom. The load shall be unloaded grade by grade to the

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static/active loading grade and then loaded to the maximum loading grade in accordance with the loading procedure. If there is the occurrence of crack opening, this load grade will be assessed as the real anti-crack grade for the beam, and since this does not correspond to the designed anti crack coefficient for the beam, the beam will be assessed as unqualified. Deflection: The measured deflection-span ratio must be less or equal to the designed ratio as stipulated in the calculated figures issued to CCECC by their designers for the particular beam in question. The beam designed span value used in calculations was 29.34m, and the calculated maximum deflection-span ratio and coefficient of correction issued by CCECC designers were 1/3066 and 1.04 respectively. During the test CCECC engineers on site were joined by Nexant and LAMATA engineers who monitored the processes all the way, to ensure that the test was carried out in line with the reference Standard and the approved Method Statement. Data Acquisition: Firstly, Nexant had to ensure that the equivalent loads applied on the beam via the five equally spaced loading jacks corresponded with the theoretical values specified. But because CCECC insisted that having more than one Nexant engineer on the beam would adversely affect the deflection readings, Nexant put only one engineer on the beam and made up by quickly distributing cameras among some of CCECC operators who got clear shots of the pressure readings at each stage of loading as the Nexant engineer was also not permitted by CCECC to move across the mid-span of the beam during test. Below is Table 1 showing the summary of the monitoring of the oil pressure gauge readings during the test.

LOADING

GRADE

PRESSURE

GAUGE

READINGS

(MPa)

FIRST CYCLE LOADING JACK POSITIONS SECOND CYCLE LOADING JACK POSITIONS

Jack No.1

Jack No. 2

Jack No. 3

Jack No. 4

Jack No. 5

Jack No. 1

Jack No. 2

Jack No. 3

Jack No. 4

Jack No. 5

Primary status

Target: 0 0 0 0 0 0 0 0 0 0

Actual: N/A N/A N/A N/A N/A N/A N/A N/A

N/A N/A

Base grade (ka)

Target: 12.0 11.9 11.8 11.8 11.9 12.0 11.9 11.8 11.8 11.9

Actual: 12.1 11.7 11.5 11.6 N/A N/A N/A 11.6 N/A N/A

Grade 0.8 Target: 13.9 13.7 13.6 13.7 13.8 13.9 13.7 13.6 13.7 13.8

Actual: 14.6 13.7 13.3 N/A N/A N/A 12.9 13.5 13.5 N/A

Static live load (kb)

Target: 17.6 17.4 17.3 17.4 17.5 17.6 17.4 17.3 17.4 17.5

Actual: 17.0 17.4 17.3 N/A N/A N/A N/A 17.1 17.4 N/A

Grade 1.0 Target: 18.7 18.6 18.4 18.5 18.7 18.7 18.6 18.4 18.5 18.7

Actual: 19.1 19.0 18.3 N/A N/A N/A 18.2 18.4 18.3 N/A

Grade 1.05 Target: 19.9 19.8 19.6 19.7 19.7

Actual: 19.9 19.5 19.6 19.7 N/A

Grade 1.10 Target: 21.1 21.0 20.8 20.9 21.1

Actual: 21.6 21.0 20.8 20.8 N/A

Grade 1.15 Target: 22.3 22.2 22.0 22.1 22.4

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Actual: 23.5 21.9 22.0 22.0 N/A

Grade 1.20 Target: 23.5 23.4 23.2 23.3 23.6

Actual: 24.0 23.0 23.0 23.2 N/A

Table 1: summary of the monitoring of the jacks oil pressure gauge readings during the test

On the table, the red colours are used to indicate erroneous pressure readings as observed by Nexant during the test. The error judgement is based on the precision of the pressure gauges as submitted by CCECC in the approved Method Statement, which is 0.4. The maximum pressure capacity of the gauges is 60MPa. This means that the allowable tolerance for the gauges is 0.4% of 60MPa, which is ± 0.24MPa. Out of the 60 given target readings, Nexant was practically able to monitor 38 target readings. And out of the 38 target readings monitored by Nexant in the course of the test, 12 readings showed disparity between the target reading and the actual reading beyond the allowable tolerance, representing 11.6% of the monitored target readings. Of the 12 erroneous readings, 4 were over-pressured readings while 8 were under-pressured readings. The highest over-pressured reading was by a difference of 1.2MPa representing 5.4% of the expected reading, while the highest under-pressured reading was by a difference of 0.8MPa representing 5.8% of the expected reading. Below is Table 2 showing a summary of the over-pressured and under-pressured oil pressure gauge readings during the test. Please, also see photos 9 and 10 at the bottom showing readings on #1 pressure gauge during the highest 1.2 loading grade of the second cycle and #1 pressure gauge during the 0.8 loading grade of the first cycle respectively. The pressures were 24MPa against 23.5MPa and 14.6MPa against 13.9MPa respectively.

OVER-PRESSURED READINGS (MPa UNDER-PRESSURED READINGS (MPa)

TARGET READING

ACTUAL READING

DIFFERENCE TARGET

READING ACTUAL

READING DIFFERENCE

13.9 14.6 0.7 11.8 11.5 0.3

21.1 21.6 0.5 13.6 13.3 0.3

22.3 23.5 1.2 13.7 12.9 0.8

23.5 24.0 0.5 17.6 17.0 0.6

18.6 18.2 0.4

19.8 19.5 0.3

22.2 21.9 0.3

23.4 23.0 0.4

Table 2: summary of the over-pressured and under-pressured oil pressure gauge readings

Secondly, Nexant had engineers permanently posted to monitor and acquire data from the six deflection data acquisition positions located at the mid-span and at the two ends of the beam. Nexant engineers ensured that the readings being taken down by the Chinese engineers were accurate, while also taking their own readings and getting pictures of the flexometers at the end of every loading grade. (Please see photos 11 and 12 at the bottom showing flexometer deflection readings for mid-span (south) and east-end (north) respectively during the 1.2 loading grade of the second cycle. The deflections were 34.97mm and 7.08mm respectively).

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Thirdly, Nexant engineers were equipped with permanent markers and magnifying crack gauges. At the end of every loading grade, the beam was examined for new cracks and opening of existing cracks. Data Analysis: Cracks: During the various stages of the loading of the beam and after the application of the 1.2 loading grade representing the load to be borne by the beam at the designed anti-crack coefficient, the beam was thoroughly examined and no new cracks were observed. Neither did the existing cracks open any further. Deflection: The deflection readings were monitored and checked during the test and found to be accurate. The deflection readings were calculated for the north and south side deflections and the average values used in the final assessment of the deflection-span ratio for the beam. Please see Table 3 below for the average girder centre measured deflection values (averaged between the north and south flexometer readings) for the various loading grades.

Cycle 1

Loading grade

Base grade (Ka)

0.80

Static-live load

grade (Kb)

1.00

Load (KN)

176.7 204.7 261.1 278.0

Average

deflection

(mm)

12.383 15.853 19.785 20.790

Cycle 2

Loading grade

Base grade (Ka)

0.8

Static-live load

grade (Kb)

1.0 1.05 1.10 1.15 1.20

Load (KN)

176.7 204.7 261.1 278.0 296.3 314.6 332.9 351.2

Average

deflection

(mm)

12.463 15.160 19.918 21.673 23.230 25.193 26.948 28.498

Table 3: average girder centre measured deflection values for the various loading grades

For the calculation of the final deflection-span ratio, the average measured deflection at the Base Grade (ka) and that at the Static-Live Load (kb) are used. The final deflection-span ratio is given by

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the formula: Y/L = (ykb - yka)/L Where Y is the final calculated deflection in millimetres, L is the designed beam span or 29340mm, ykb is the average measured deflection at the Base Grade (ka), and ykb is the average measured deflection at the Static-Live Load (kb). According to the specifications given to CCECC by their designers, the value of Y/L must not be more than the corrected design deflection-span ratio for beam 30Z2-074 at the age of test, which is 1.05*(1/3066)/1.04 = 0.0003293 = 1/3037. From the analysis of the deflection readings gathered during the test: Y/L = (ykb - yka)/L = (19.785mm - 12.383mm) / 29340.0mm = 0.000252 = 1/3968 (for the first loading cycle) = (19.918mm - 12.463mm) / 29340.0mm = 0.000254 = 1/3937 (for the second loading cycle). Both of these values are less than the specified maximum, which is 0.0003293 = 1/3037 Conclusion:

1. The test was carried out in accordance with the specifications as stipulated in the Chinese code TB/T 2092-2003 (Post-tensioned precast concrete simple-supported girder for Railway Bridge pro-stress).

2. At the end of the loading time for the 1.2 loading grade, no new crack was observed and there was no extension or opening of existing cracks.

3. The measured deflection-span ratio values obtained during the beam static load test were less than the specified maximum deflection-span ratio.

4. 38 target loads were monitored out of 60 target loads. 12 of the 38 monitored loads showed errors in the actual loads applied. 4 loads were higher than the target with the greatest value deviating by 5.4% of the target. 8 loads were lower than the target with the greatest value deviating by 5.8% of the target.

Izu Nnaji, Quality Assurance Supervisor, Nexant Consulting LLP.

Attachments:

1. Photographs photos 1 to 8 showing some of the cracks and defects observed on stricking the mould.

2. Photographs (Photos 9 and 10 showing readings on #1 pressure gauge during the 1.2

loading grade of the second cycle and #1 pressure gauge during the 0.8 loading grade of

the first cycle respectively. The pressures were 24MPa against 23.5MPa and 14.6MPa

against 13.9MPa respectively).

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3. Photographs (Photos 11 and 12 showing flexometer deflection readings for mid-span

(south) and east-end (north) respectively during the 1.2 loading grade of the second cycle.

The deflections were 34.97mm and 7.08mm respectively).

4. Photographs (Photos 13 and 14 showing a LAMATA engineer examining flexometer

readings during the test, as well as a cross-section of Nexant engineers getting final briefs

before the commencement of test).

Distribution List:

Name Company Position

Alexander Wang CCECC Deputy Project Manager

Lv Feng CCECC Deputy Project Manager

Li Bing CCECC Deputy Project Manager

Chen Gao Liang CCECC Chief Engineer

Dr. Dayo Mobereola LAMATA Managing Director

Gbenga Dairo LAMATA Director Public Transport

Olaseni Akinwunmi LAMATA Project Manager

Photographs

Photos 1 and 2 showing cracks and defects on the south side mid-span clapboard.

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Photos 3 and 4 showing cracks and defects on the north side mid-span clapboard.

Photos 5 and 6 showing cracks and defects on the second south side transverse connection board.

Photos 7 and 8 showing cracks and defects on the second north side transverse connection board.

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Photos 9 and 10 showing readings on #1 pressure gauge during the 1.2 loading grade of the second

cycle and #1 pressure gauge during the 0.8 loading grade of the first cycle respectively. The pressures

were 24MPa against 23.5MPa and 14.6MPa against 13.9MPa respectively.

Photos 11 and 12 showing flexometer deflection readings for mid-span (south) and east-end (north)

respectively during the 1.2 loading grade of the second cycle. The deflections were 34.97mm and

7.08mm respectively.

Photos 13 and 14 showing a LAMATA engineer examining flexometer readings during the test, as

well as a cross-section of Nexant engineers getting final briefs before the commencement of test.