MERLIN consists of a rigid metal frame, 1

CALIBRATION

OF

BUMP INTEGRATORJUNE- 2015

Center For Transportation Engineering Department of Civil Engineering Bangalore University

Bangalore 560 056

BUB/CTE/2014-15 Date: 05-06-2015CONDITIONS OF ISSUE OF CALIBRATION CERTIFICATE

This is to certify that the Automatic Road Unevenness Recorder No.

STECO-062, belongs to Highway Engineering Section, Department of Civil Engineering, Bangalore University, Bangalore is calibrated in the Centre for Transportation Engineering, Bangalore University , Bangalore - 560 056 using TRL MERLIN as the standard equipment. The results presented in this report is valid from June-2015 to June 2017 or 5000 Kms whichever occurs earlier, unless the machine suffers a major mechanic breakdown. In such a condition this certificate becomes invalid and then should be recalibrated for further use.

CONTENTS

Sl. Title

No.1.0 INTRODUCTION

2.0 SELECTING AND PROFILING CALIBRATION SECTIONS

3.0 TRL MERLIN

4.0 THE CALIBRATAION SURVEY

5.0 ANALYSIS

BUB/CTE/2015-16 Date: 5th JUNE- 2015 Sub: Calibration of Automatic Road Unevenness Recorder No. STECO-091

Ref : Letter No. Testing/2007-08, dated 15-05-2007

Project Manager,M/s Patel-KNR (JV), Keela Urappanur (Village), Thirumangalam,

Dindigul Road, Thirumangalam-625 706 {Project: *: 4 Laning and Strengthening of Existing 2 lane of Madurai- Kanyakumari

Section of NH7, Package 39,Km 0/ 000 to 48/817 in the State of Tamilnadu *}

. 1.0 INTRODUCTION The Bump Integrator (BI) a response type unevenness meter, which is towed by a vehicle to monitor pavement unevenness. It records the displacement per unit distance traveled, usually in terms of counts/km.

A well calibrated unevenness meter which is properly operated, will give accurate and reproducible data at a very low cost. However, a poorly calibrated meter will not only give questionable data it June lead to incorrect decisions being made.

2.0 SELECTING AND PROFILING CALIBRATION SECTIONS.The objective of calibration section profiling is to obtain an accurate representation of the road profile. It is necessary to identify calibration sections, which cover the full range of Unevenness the survey is likely to encounter. These sections should have the following Characteristics:. The sections should be at least 200-300 m long with adequate geometry before and after the section to ensure that they can be travelled at a constant speed;

the unevenness should be fairly uniform along the length insofar as there are not

short sub-sections with high unevenness interspersed with sub-sections containing lower unevenness; the surface should not be broken (i.e. potholes or bad depressions) so that the

profiling survey can get the true profile; they should have low traffic volumes so that the unevenness will not change significantly over time and so that the crew will survive the calibration survey; One should not have combinations of rigid and flexible or machine laid and hand Laid sections since these can have different unevenness properties although this is not always possible in some countries if one cover the full range of unevenness: The beginning and end of sections should be clearly marked;

The wheel paths should be permanently marked for profiling using nails and painting them white. During recalibration the crew can then readily remark the wheel paths. The sections should be profiled using one of the techniques below:

A rod and-level survey;

TRL Beam;

DIPSTICK;

Walking Profilometer;

High- Speed Profilometer;

TRL MARLIN,

Multiple wheel unevenness Indicator.

MERLIN was used in this particular study for profiling.

3.0 TRL MERLIN

MERLIN (Machine for Evaluating Roughness using Low- cost Instrumentation) was devised to measure the unevenness of a calibration section inexpensively, quickly,

easily and reliably. It does not measure the elevation profile; instead it correlates a measured profile with the international Roughness Index (IRI) or Unevenness Index (UI)

Because of its ease of use and the ability to have one constructed even in the remotest

parts of the globe, the MERLIN has gained widespread acceptance as a calibration tool.

MERLIN consists of a rigid metal frame, 1.8 m long, with a wheel at the front; a curved foot at the rear and a moveable probe midway between the two, which rests on the road surface. If the road were always smooth, the probe would always lie on a straight line between the bottom of the wheel and the rear foot. If the road were uneven, the probe would usually be displaced above or below the line.

To measure the displacements, the probe is attached to a pivoted arm, at the other end of which is a pointer, which moves over a chart. The arm is pivoted close to the probe so that a movement of the probe of 1mm will produce a pointer movement of 5 mm or 1 cm.

The unevenness of a section is measured by wheeling the MERLIN along the road with the handles raised. Once every wheel revolution, the handles are lowered so that the probe and rear foot touch the ground and the resulting pointer position is recorded as a cross on a chart. Two hundred measurements are made to produce a histogram, which means the MERLIN surveys require approximately 450m long calibration sections. The width of the central 90 percent of the histogram is measured from the chart and this can be converted directly into unevenness.

4.0 The Calibration Survey

The calibration survey is conducted by operating the vehicle over each calibration section over each wheel path at a constant speed of 30 kmph and recording the output of the Bump Integrator.

Calibration surveys are done by driving the vehicle at a constant speed. Unevenness data were collected over what is called a sampling Interval. By running the survey vehicle with Bump Integrator over a number of profiled sections, each with different unevenness, a relationship between the raw count of the Bump Integrator towed by the survey vehicle and the standard roughness measured using MERLIN was established.

The survey vehicle is driven such that the Bump Integrator travels over the marks made on the road from start point to the end point at a speed of 30 kmph. MERLIN surveys were carried out on the same stretches on both the wheel paths to obtain the D value in mm. The D value for each run was established by measuring the positional mid-way between the tenth and eleventh crosses, counting in form each end of the distribution.

The D value is converted into IRI using the following equation (for use on Asphaltic Concrete surface).

IRI = 0.593+0.0471 x D

The IRI value is converted into UI using the following equation.

UI=630 x (IRI)1.12

Where

IRI= International Roughness Index, m/Km

UI = Unevenness Index expressed in mm/km for Asphaltic Concrete

D = the roughness in terms of the MERLIN scale measured in mm.

5.0 AnalysisThe raw Bump Integrator counts per kilometer obtained from the calibration survey are correlated with the UI values obtained from MERLIN. This equation is used to convert the raw Bump Integrator counts into UI in mm/km.Results from Calibration Test SectionsSection Number.Merlin ResultsRAW BUMP INTEGRATOR COUNTS

UI in mm/km

D in mmUI in mm/km

159.824892860

298.540214100

3123.750565080

495.238863930

567.627892810

The general equation used for the calibration of the raw counts in terms of UI can be summarized as follows:

UI = A0 x RAW + A1

Where

UI = Roughness calibrated to International Roughness Index in m/km

RAW = Raw Bump Integrator counts in mm/km

A0 = Regression coefficient

A1 = Constant

The resulting regression relationship and the regression equation are presented below.

Validity: June 2015 June 2017 or 5000 kms whichever occurs earlier.Therefore, the Unevenness Index value can be obtained from the raw Bump Integrator counts by applying the calibration equation.

UI = 0.9818 * RAW 20.63

Where,

UI = Unevenness Index in mm/km

RAW = Raw Bump Integrator counts in mm/km. EMBED MSPhotoEd.3

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