The Standard New Road Project

Transcription

1 Agile Construction Initiative The Standard New Road Project Benchmark method ACI/DLV/ 96/017

2 The Standard New Road Project Authors David Madigan, Agile Construction Initiative Document control information: Date of issue 31 March, 1997 Document number ACI/DLV/ 96/017 Circulation Public Version 3.00 To obtain a copy of this document contact ACI at: School of Management University of Bath Bath, BA2 7AY United Kingdom Tel: + 44 (0) Fax: + 44 (0) A.P.Graves@bath.ac.uk Web: Copyright University of Bath, 1997 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the copyright holder. 2

3 Table of Contents 0. TABLE OF CONTENTS INTRODUCTION THE AGILE CONSTRUCTION INITIATIVE THE PRINCIPLES OF BENCHMARKING THE PURPOSE OF THIS DOCUMENT PRODUCT BREAKDOWN STRUCTURE DEVELOPING THE PRODUCT BREAKDOWN STRUCTURE HIGHWAYS AGENCY CESMM ADVANTAGES AND DISADVANTAGES DETAILED COMPARISON FINAL PRODUCT BREAKDOWN STRUCTURE SIZING ELEMENTS PRINCIPLES OF MEASUREMENT GENERAL COMMENTS ON MEASUREMENT EARTHWORKS IN SITU CONCRETE CONCRETE ANCILLARIES DRAINAGE PIPES PIPEWORK - MANHOLES PILES ROADS AND PAVING RESULTS FROM PILOTS THE NEED FOR SIZING ITEMS GENERAL DIFFICULTIES IN OBTAINING DATA CONCLUSIONS ANNEX A - DERIVATION OF SIZING ITEMS FOR MANHOLES...26 FIGURE 1 EARTHMOVING OPERATIONS...11 FIGURE 2 TYPICAL CROSS SECTION OF A ROAD...22 FIGURE 3 COMPOSITE CONSTRUCTION...23 FIGURE 4 RIGID CONSTRUCTION...23 FIGURE 5 LABOUR GANG HOURS VERSUS MANHOLE VOLUME...26 TABLE 1 HIGHWAYS AGENCY MEASUREMENT METHOD - SERIES...7 TABLE 2 MAIN CATEGORIES OF CESMM...8 TABLE 3 ADVANTAGES AND DISADVANTAGES OF BOQ AND CESMM...8 TABLE 4 DETAILED COMPARISON OF BOQ AND CESMM...8 TABLE 5 PRODUCT BREAKDOWN STRUCTURE...9 TABLE 6 EXCAVATION TIMES FOR DIFFERENT TYPES OF MATERIAL...13 TABLE 7 EQUIVALENT QUANTITY OF EXCAVATION...13 TABLE 8 VARIATION OF EXCAVATION TIMES WITH MATERIAL TYPE...14 TABLE 9 EQUIVALENT QUANTITY OF EXCAVATION...14 TABLE 10 VARIATION OF MAKE AND FIX TIME WITH TYPE OF FORMWORK...16 TABLE 11 SIMPLIFIED FORMWORK PRODUCTIVITY FACTORS...16 TABLE 12 CALCULATION OF EQUIVALENT QUANTITIES OF FORMWORK

4 Introduction The Agile Construction Initiative The Agile Construction Initiative (ACI) is a new project under the government s Innovative Manufacturing Initiative (IMI), funded by the Engineering and Physical Sciences Research Council (EPSRC). ACI has been set up to research into the transfer of lean production practices pioneered by leading Japanese manufacturing companies to the UK civil engineering industry. The leading industrial partner will be Balfour Beatty Civil Engineering Limited (BBCEL) based in the UK. The research is being undertaken by the University of Bath, School of Management. The programme of work consists of a number of elements. Primarily, the project will undertake benchmarking to compare the current performance of the UK construction industry with the best in the world. It will develop ideas on what constitutes best practice in the construction industry. Best practices identified by the programme will be piloted by the Agile Construction Initiative within the industrial partners before being disseminated to the industry at large. In parallel to this work research will be conducted on financial control systems, managing the value chain and life cycle assessment. The principles of benchmarking Benchmarking is a management tool that is currently enjoying a high profile. Many projects are being carried out under the banner of benchmarking and it is important to outline what ACI understands by the term. ACI has adopted the following definition of benchmarking: Benchmarking is a systematic and continuous measurement process; a process of continuously measuring and comparing an organisation s business processes against business process leaders anywhere in the world to gain information which will help the organisation take action to improve its performance. 1 In order to develop a methodology some additional principles have been adopted, based on the work of the International Motor Vehicle Program (IMVP). 1. Standard products 2. Measures of performance 1 The definition was developed by the International Benchmarking Clearinghouse (IBC) 4

5 3. Indicators of practice. The use of standard products allows fair comparison to be made between different organisations. It is important to compare apples to apples. The standard product is defined by the set of activities that result in the construction of the standard product. Measures of performance are used to find the organisations that are capable of delivering superior performance to their customers. The starting point for lean thinking is the concept of value. Organisations exist to create value for their customers and this must be reflected in the measures of performance. Indicators of practice are used a the stepping stone into deep case studies of successful organisations. They point to the best practices that allow the organisations to deliver superior performance. The purpose of this document The overall benchmark method is described in full in the ACI Working Paper Benchmark Method: Building on CESMM. The purpose of this document is to describe one of the standard products that has been developed to benchmark the civil engineering industry. This standard product is a new road construction. The document describes the activities that are included in the definition of the standard product and the principles of measurement that apply to these activities. 5

6 Product breakdown structure Developing the product breakdown structure The product breakdown structure defines the construction products that when assembled together on site make up the standard new road. The list was arrived at by doing the following: 1. Excluding all products that were considered non-standard and for which it would be difficult to get data from all participating projects. 2. Taking the 20% of components that represented about 80% of the cost of the standard product. 3. Generalising the component definitions to make it easier to get returns from all participating projects. This resulted in about fifty elements in the standard new road. Two standard documents were using in generating the component definitions; the Highways Agency Bill of Quantities and the ICE s CESMM3. These are rather different in character as a result of the generalisation in CESMM3 to make it applicable to all civil engineering contracts. The following sections contrast the two documents and then introduce the final product breakdown structure for the new road project. Highways Agency The Highways Agency measurement method is organised into a number of different series of construction components. Series 400 Safety Fences Safety Barriers And Pedestrian Guardrails Beam Safety Fences Vertical Concrete Barrier Series 500 Drainage And Service Ducts Drains Sewers Piped Culverts And Service Ducts (Excludng Filter Drains, Narrow Filter Drains And Fin Drains) Fin Drains And Narrow Filter Drains Filter Drains Linear Soakway Chambers Concrete Channels Series 600 Earthworks Excavation Excavation In Hard Material Deposition Of Fill Compaction Of Fill Topsoiling And Storage Of Topsoil Grassing Completion Of Formati0n Series 700 Pavements 6

7 CESMM3 Sub Base Flexible Pavement Rigid Pavement Bridge Decks.Surfacing Series 1100 Kerbing footways and paved areas Kerbs, Channels, Edgings And Combined Drainage And Kerb Blocks Series 1200 Traffic Signs & Roadmarkings Roadmarkings Table 1 Highways Agency measurement method - series The applicable sections of CESMM3 are as follows: Code Description E EARTHWORKS F IN SITU CONCRETE G CONCRETE ANCILLARIES G1 Formwork: rough finish G2 Formwork: fair finish G3 Formwork: other stated finish G4 Formwork: stated surface finish G5 Reinforcement G8 Concrete accessories G81 Finishing of top surfaces I PIPEWORK - PIPES K PIPEWORK - MANHOLES ETC M STRUCTURAL METALWORK M5 Erection of members for bridges N MISCELLEANOUS METALWORK N15 Bridge parapets P PILES P1 Bored cast in place concrete piles R ROADS & PAVING R3 Sub-bases, flexible road bases and surfacing R4 Concrete pavements R6 Kerbs, channels and edgings R8 Ancilliaries R82 Surface markings W WATERPROOFING X MISC. X1 Fences X18 Metal crash barriers 7

8 Table 2 Main categories of CESMM Advantages and disadvantages Highways Agency BoQ UK Highways projects site measurement systems will match this format well. The match between BoQ items and site activities is good. Little work has to be done on the BoQ to turn it into the benchmark method. Site performance isn t recorded in same categories as BoQ Detailed comparison CESMM3 The performance on individual construction activities can be compared for non-highways and highways sites The match will not be so good in all cases. More work has to be done. Site performance isn t recorded in same categories as CESSM3 Table 3 Advantages and disadvantages of BoQ and CESMM Item Highways Agency CESMM3 Placement of concrete Divides items according to location in structures; superstructure, ends Divides items according to type of pour; slab, wall, base, column supports Distinguishes between Excavation Formwork Reinforcement concrete mixes. Separate items for compaction Uses Highways Agency materials definitions (in particular chalk is treated separately) Uses Highways Agency formwork definitions Table 4 Detailed comparison of BoQ and CESMM Final product breakdown structure Simpler materials definitions Distinguishes between straight and deformed reinforcement The final product breakdown structure is shown in Table 5. The breakdown is based on the Highways Measurement Method and CESSM. The breakdown is simplified to tie up with the way that data is collected on site. 8

9 Sizing elements Classification Description C31 Insitu concrete in Superstructure C32 Insitu concrete in End Supports C33 Insitu concrete in Intermediate Supports C34 Insitu concrete in Underpass/Culvert main construction C7 Insitu concrete in blinding not exceeding 75mm in thickness E11 Excavation of acceptable material; Topsoil E12 Excavation in cutting and other excavation other than topsoil and rock E311 Deposition of acceptable material in embankments and other areas of fill; material other than topsoil and rock E322 Deposition of acceptable material in landscape areas E51 Topsoiling of varying thickness to surfaces sloping at 10 degrees or less to the horizontal E52 Topsoiling of varying thickness to surfaces sloping exceeding 10 degrees to the horizontal E7 Completion of formation F11 Formwork in Superstructure F12 Formwork in End Supports F13 Formwork in Intermediate Supports F14 Formwork in Underpass/Culvert main construction I11 Carrier drain, internal diameter from greater than 150mm and less than or equal to 450mm, in a trench depth to invert less than or equal to 3m I12 Carrier drain, internal diameter from greater than 450mm and less than or equal to 750mm in trench depth to invert less than or equal to 3m I21 Edge of carriageway drain; narrow; in trench depth not exceeding 1.5m I3 Manhole I4 Gullies P1 Vertical 600 or 750mm diameter cast-in-place main piling (boring, concrete and reinforcement) P2 Vertical 900mm or 1050mm diameter cast-in-place main piling (boring, concrete and reinforcement) R11 Granular sub-base in main carriageway R12 Lean concrete sub-base in main carriageway R22 Heavy Duty Macadam basecourse in main carriageway R23 Heavy Duty Macadam roadbase in main carriageway R31 Wearing Course in main carriageway R32 Continuous Reinforced Concrete Pavement in main carriageway S1 High yield steel deformed bar reinforcement in superstructure S2 High yield steel deformed bar reinforcement in end supports S3 High yield steel deformed bar reinforcement in intermediate supports S4 High yield steel deformed bar reinforcement in underpass/culvert main construction SF1 Safety fence; untensioned single sided open box beam straight or curved exceeding 50 metres radius SF2 Safety fence; tensioned double sided corrugated beam straight or curved exceeding 50 metres radius Table 5 Product breakdown structure The final product breakdown structure is inadequate for making like for like comparisons between different sites. The categories are too broad. To 9

10 overcome this the concept of sizing elements are introduced. These work as follows: 1. The site submits are return for a given element in the product breakdown structure. The return contains the quantity of the item produced. 2. The product breakdown structure categories are too general for fair comparison so the quantities are adjusted using sizing elements. 3. The quantity adjustment means that the comparison is being made against the same construction product. This is best illustrated by an example. 1. Formwork performance data is collected according to the part of the structure that is being constructed; superstructure, end supports etc. 2. However, two end supports are not the same design and will contain different mixes of individual types of formwork. 3. In order to make fair comparison, the quantities of different classes of formwork are listed and then these are converted to equivalent quantities of a single class of formwork. 4. The conversion is based on the different times it takes to fix each different class of formwork according to the CESSM3 Price Database 1996/7. The classes that are used are i) horizontal, sloping or battered ii) vertical and iii) curved. The quantities of each of these that go together to make up the total quantity on the return are listed. They are then converted to equivalent quantities of horizontal formwork. The total quantity of horizontal equivalent is then used to compare performance. 10

11 Principles of measurement General comments on measurement Earthworks Excavation General The benchmark method requires the following data to supplied for each of the activities that make up the standard new road project. 1. The total quantity of the component produced by the activity. 2. The amount of working time that the construction gang spent producing the component. 3. The theoretical capability of the construction gang based on the plant configuration in use. In order to make sure that a fair comparison is made between projects a number of additional factors will be measured that may affect performance. If necessary the affect of these will be removed before project performance is compared. The following sections define the principles of measurement for different classes of construction components that make up the new road project. Disposal Re-use Double handling Import Figure 1 Earthmoving operations 2 2 Taken from Barnes, M (1992) CESMM3 Handbook, London: Thomas Telford 11

12 Effort calculation Capability calculation Sizing factors Excavation and filling/compaction are separated. The reason for this is because of the varying destinations and sources for excavated and filling material. This is shown in Figure 1. The amount of effort required is calculated for each piece of excavation plant. The time is then the amount of time that the piece of plant is working. The time includes time that the plant is idle awaiting trucks to load and plant breakdowns, but excludes meal breaks and breaks for poor weather. The calculation is the same for motor scrapers. They will not suffer idle time awaiting trucks but may have idle time waiting for access to the cutting area. As the productivity may vary according to the type of material being excavated, this information will be included on the returns to allow its significance to be investigated. The rate of production that the excavation plant should be capable of producing working 100% of the time according to the manufacturers specification. The rate of production will need to take into account the properties of the material being excavated, in particular the bulking factor of the material. The rate of production of excavators is related to the type of material being dug. In order to make fair comparison on excavation, the returns need to be adjusted to a common material type. The default material is Medium hard clay with cobbles. Returns for other types of materials will be adjusted. The quantities will be adjusted to equivalent quantities of the default material. The following adjustments will be made to the working time according to the type of material being excavated: 12

13 Factors to measure Material being excavated Multiplier (Equivalent quantity = measured measured * Multiplier) Firm sand 0.70 Soft loam, sandy clay 0.85 Medium hard clay with cobbles 1.00 Gravel 1.10 Broken stone 1.25 Stiff clay with boulders 1.33 Soft chalk 2.50 Table 6 Excavation times for different types of material Sample calculation: Material Quantity (m 3 ) Equivalent quantity (m 3 ) Medium hard clay with cobbles 40,000 40,000 Broken stone 60,000 75,000 TOTAL 100, ,000 Table 7 Equivalent quantity of excavation Working time = 262 hours Gross productivity = 262/100,000 = 2.62 per 1000m 2 Adjusted productivity = 262/115,000 = 2.28 per 1000m 2 1. The average distance the material is being hauled over (in km) 2. Whether the haul is all contained within the site or goes on to public roads. (1 = within site, 2 = on public roads). 3. The destination of the material. Filling and compaction General comments Effort calculation Filling and compaction will be measured as a single activity. The amount of effort is calculated for each piece of compaction plant. The amount of effort will be the working time of the compaction plant. The time 13

14 Capability calculation Sizing factors includes time that the plant is idle awaiting material to compact and plant breakdown, but excludes meal breaks, breaks for poor weather. The rate of production that the excavation plant should be capable of producing working 100% of the time according to the manufacturers specification and the appropriate design tables of numbers of passes required for the material being compacted. 1. The material being compacted. The rate of production of excavators is related to the type of material being dug. In order to make fair comparison on excavation, the returns need to be adjusted to a common material type. The default material is Medium hard clay with cobbles. Returns for other types of materials will be adjusted. The quantities will be adjusted to equivalent quantities of the default material. The following adjustments will be made to the working time according to the type of material being excavated: Material being excavated Multiplier (Equivalent quantity = measured quantity * Multiplier) Firm sand 0.70 Soft loam, sandy clay 0.85 Medium hard clay with cobbles 1.00 Gravel 1.10 Broken stone 1.25 Stiff clay with boulders 1.33 Soft chalk 2.50 Table 8 Variation of excavation times with material type Sample calculation: Material Quantity (m 3 ) Equivalent quantity (m 3 ) Medium hard clay with cobbles 40,000 40,000 Broken stone 60,000 75,000 TOTAL 100, ,000 Table 9 Equivalent quantity of excavation Working time = 262 hours 14

15 Factors to measure In situ concrete General Effort calculation Gross productivity = 262/100,000 = 2.62 per 1000m 2 Adjusted productivity = 262/115,000 = 2.28 per 1000m 2 1. The average distance the material is being hauled over (in km) 2. Whether the haul is all contained within the site or goes on to public roads. (1 = within site, 2 = on public roads). 3. The source of the material. Separate items are included for different types of pour. The amount of effort is calculated as the working time from start to finish on a particular concrete pour. The figure includes time preparing for the pour, the pour itself and any time required to finish the concrete and repair any cracks etc. The time excludes meal breaks and curing time for the concrete. Capability calculation Sizing factors Not applicable. None. Factors to measure 1. Indicate the type of pour (1 = Concrete pump; 2 = Direct from concrete mixer, 3 = Manual (using dumper, excavator shovel etc), 4 = Skip and crane) Concrete ancillaries Formwork General Separate returns are required for end supports, intermediate supports, superstructure and culvert/underpass main construction. 15

16 Effort Calculation Capability Calculation Sizing factors The effort calculation shall be the total man hours in fabricating, assembling, striking and cleaning/repairing the formwork. The calculation should include the assembly and striking of any falsework required to support the formwork. Not applicable. The time taken to fix formwork of different types is shown below. 3 Rough Fair Extra Smooth Horizontal Sloping Battered Vertical Curved Table 10 Variation of make and fix time with type of formwork This has been simplified to three categories: Type of formwork Horizontal, sloping or battered Correction factor Vertical 1.65 Curved 2.25 Table 11 Simplified formwork productivity factors Formwork quantities will be converted into equivalent horizontal formwork quantities. Example: 1 3 Source: Harris, EC (1996) CESMM3 Price Database 1996/7, London: Thomas Telford 16

17 Type of formwork Measured Qty, m 2 Horizontal equivalent, m 2 Horizontal, sloping or battered Vertical Curved Factor to measure Reinforcement General Effort Calculation Capability Calculation Sizing factor TOTAL Table 12 Calculation of equivalent quantities of formwork Working time = 320 hours Gross productivity = 320/316 = 1.01 hours per m 2 Adjusted productivity = 320/518 = 0.62 hours per m 2 1. Where is the formwork manufactured? (1 = on-site, 2 = off-site) 2. How many times on average is formwork re-used? Separate returns are required for end supports, intermediate supports, superstructure and culvert/underpass main construction. The effort calculation shall be the total man hours in handling and fixing of reinforcement. The calculation shall include all effort from the arrival of steel on site to the start of the concrete pour. The time shall include time waiting for deliveries, information etc but exclude meal breaks. Not applicable. 1. The nominal size of the reinforcement bars. The time taken to fix reinforcement is proportional to the mass per unit length of the reinforcement. If the standard nominal size of the reinforcement bars is taken to be 20mm, then the quantity of reinforcement can be adjusted to an equivalent quantity of 20mm nominal size reinforcement. The equivalent quantity of 20mm nominal size reinforcement is then calculated as: 17

18 q 20 = q m { 1 ( 20 )} d 20 d + am m... Equation 1 m 2 Where, m - the mass per kg of the steel actually fixed m 20 - the mass per kg of 20mm nominal size steel q - the quantity of steel actually fixed. q 20 - the equivalent quantity of 20mm nominal size steel. d m - the nominal size of the steel actually fixed d 20 - the nominal size of the default reinforcement (20mm) Example: Factor to measure Drainage pipes General Effort measurement Nom Size, mm Qty, tonne Mass, kg/m Qty (20mm), Tonne TOTAL Working time = 98 hours Gross productivity = 98/10.4 =9.42 hours per tonne Adjusted productivity = 98/13.07=7.50 hours per tonne 1. Is the steel delivered JIT? The measurement will include all activities related to drainage installation, including excavation, supporting of trenches, installation of pipes, backfilling and testing. The effort will be the total working time of each gang that is advancing a single line of drainage. Working time shall include any time waiting for preceding activities, but will not include meal breaks or breaks due to weather conditions. Capability calculation Not applicable. 18

19 Sizing factors Factor to measure 1. Nominal bore, mm 2. Depth to invert, m The time taken to lay a carrier drain varies linearly with the nominal bore of the pipe and the depth to invert. There are four zones in which these relationships hold: 1. Small, shallow pipes (nominal bore < 450mm, depth < 3m) 2. Small, deep pipes (nominal bore < 450mm, depth > 3m) 3. Large, shallow pipes (nominal bore > 450mm, depth < 3m) 4. Large, deep pipes (nominal bore > 450mm, depth > 3m) For each zone, the time taken to lay a drain can be expressed as: t = t0 + a. dnom + b. hnom... Equation 2 Where, d nom - the nominal depth in metres h nom - the nominal pipe diameter in mm. The equivalent quantity of nominal sized pipes, is then given by the following: { ( ) ( )} q = q 1 + a d d + h h... Equation 3 nom nom nom Length,m Depth, m Diameter, mm Length of nominal pipe,m Working time = 16 hours Gross productivity = 16/200 = 0.08 hours per m Adjusted productivity = 16/167.5 = 0.10 hours per m 1. Type of excavation (1 = hand, 2 = excavator, 3 = trencher) 2. Type of material. 3. Type of support to pipes (1 = concrete bed, 2 = concrete bed + surround, 3 = granular bed, 4 = granular bed + surround, 5 = granular bed + haunch, 9 = other) 19

20 4. Type of pipe (1 = clay, 2 = concrete, 3 = iron, 4 = steel, 5 = PVC, 6 = GRP, 7 = polyethylene, 9 = other) Pipework - Manholes General Effort measurement The depths of manholes shall be measured from the tops of covers to channel inverts of base slabs, whichever is lower. The measurement will include all items, including excavation, installation of the manhole, installation of pipework and fittings and backfilling. Capability calculation Sizing Factors Not applicable. 1. Internal diameter of the manhole, D 2. The depth of the manhole, h. The time taken to install the manhole is found to be a function of the volume, V = πd 2 * h... Equation 4 Where, D - the internal diameter of the manhole, mm h - the depth of the manhole, m The time taken to install a manhole is then, t = 1 + a( V Vnom)... Equation 5 Where, V nom is the volume of the standard manhole. The equivalent number of nominal sized manholes, is then given by the following: ( ( nom )) q = q 1 + a V V... Equation 6 nom Depth, m Diameter, mvolume, m Number of nominal tan Working time = 7.3 hours Gross productivity =7.3 hours per manhole 20

21 Factor to measure Piles General Effort calculation Adjusted productivity = 7.3/ = hours per manhole 1. Type of manhole (1 = Brick, 3 = In situ concrete, 5 = Precast concrete, 9 = Other) The length of piles shall be those required, from the cut-off level to the toe level. Will include all operations including setting up the rig, boring, reinforcement, placing of concrete and breaking down any excess. Working time shall be the total working time on the pile including breakdowns and waiting for materials but excluding meal breaks and breaks due to weather. Capability calculation Not applicable. Factor to measure 1. Number of piles. Roads and paving Sub-bases, flexible road bases and surfacing General A typical cross section of a road pavement is shown in Figure 2. The capping layer is only required if the subgrade is weak. 21

22 Surfacing Road surface Wearing course Base course Roadbase Pavement Pavement foundation Sub-base Formation Capping Subgrade Formation Effort Calculation Capability calculation Sizing factor There are two variations of interest; rigid pavement construction and composite construction (Error! Reference source not found.). The effort calculation will be carried out for the gang of men and machines that are advancing a single line of road. In the case of flexible road layers this will probably correspond to a paving machine. In the case of the rigid pavement this will correspond to a concrete train. The capability calculation will be based on the rated output of the paving machine or concrete train. 1. Depth of the road layer, mm The time taken to lay a m 2 of roadworks and paving is proportional to the depth of the layer. t Figure 2 Typical cross section of a road = ad... Equation 7 If the nominal depth of a road layer is d nom, then the equivalent quantity of nominal depth roadworks and paving is given by the following: q nom d = q....equation 8 dnom Example: Base course nominal depth is 50mm. 22

23 Surfacing Road surface Wearing course Base course Roadbase Pavement Pavement foundation Lean-mix Capping Subgrade Formation Figure 3 Composite construction Pavement Surfacing Pavement foundation Road surface Reinforcement mesh Concrete Polythene Sub-base Subgrade Formation Factor to measure Figure 4 Rigid construction Return, nominal depth is 75mm. Quantity is 1000m 2.. The equivalent quantity of 50mm base course is 1500m 2. Working time = 7.3 hours Gross productivity =7.3 hours per 1000m 2 Adjusted productivity = 7.3/1.5 = 4.9 hours per 1000m The actual width of the road 2. The actual depth of the layer. 23

24 Results from pilots The need for sizing items The pilots showed up difficulties in the original concept. The list of construction activities was initially based more directly of CESMM. This proved problematic for the following reasons: 1. Site data collection did not generally go down to the required level of detail. Increasingly site data collection is based on the activities on the project plan. These would have items such as fix formwork on abutment. There was no way to separate data amongst the different types of formwork in CESMM. 2. Using the CESMM definitions led to a list of 55 construction activities that accounted for about 80% of the value of the standard project. When visiting other sites it was impossible to get returns on all 55 due to differences in the designs. Sizing items have two main advantages: 1. They allow the data to be collected at a level that suits the sites - resulting in returns on only about 30 construction activities. 2. They allow the data to be adjusted for differences in the designs on different sites so that a like for like comparison of performance can be made. General difficulties in obtaining data Whilst sizing items helped a great deal in the development of the method, there were still difficulties with the quantity and quality of data on site. The information required by the benchmark method is all available on site to some degree. However, it is often fragmented amongst different individuals - engineers, quantity surveyors, accountants etc. Sometimes differences in the way that these different groups collect data makes it difficult to combine the data in the way that we require. There is also a difficulty with obtaining consistency with respect to the productive units. When counting hours on an activity like formwork, some sites only included carpenters hours, whilst others included carpenters and labourers. Similarly, on plant intensive activities it is often difficult to extract the hours for the productive units from the general plant hours. As a result the amount of that can be achieved with historic data may be limited. It may be necessary to work only with live sites, training site personnel in the benchmark method. 24

25 Conclusions The standard new road project has proved that the principles adopted by ACI for benchmarking civil engineering projects can be applied in practice. However, pilot trials have highlighted difficulties with both the design of the method and its implementation. Having learnt from these experiences ACI is now ready to roll out the method on a wider scale and will be looking for projects to benchmark over the next few years, in order to build up a comprehensive picture of the relative performance of civil engineering projects. This information will then be used to derive guidelines about best practice in civil engineering. 25

26 Annex A - Derivation of sizing items for manholes The data in the CESMM price book was put into a table. Several attempts were made to find a physical characteristics of the manhole that varied linearly with the time taken to install a manhole. It was found that the time taken varied with the volume of the manhole, calculated as follows: V 2 D = π 4 h... Equation 9 A regression analysis was carried out on the data to determine the relationship between the production time and the volume. The results are shown in Figure 5. X Variable 1 Line Fit Plot Labour Gang Hours Y Predicted Y V olum e of m anhole (m 2) Figure 5 Labour gang hours versus manhole volume The relationship was then normalised around the time taken to install a 1200mm diameter, 3m deep manhole. The resulting equation is given by the equation: t t t 0 = a t + t V...Equation 10 nom nom nom But, we know that t = t nom when V = V nom, so the equation can be rewritten as follows: 26

27 { } t a t = 1 + t V V...Equation 11 nom nom nom Rather than adjust the working time, it is better to adjust the quantity produced to achieve the same effect. That is the actual quantity of a product is modified to give an equivalent quantity of the nominal size product. It is this nominal equivalent quantity that is used to determine the productivity of the project. I.e. ( ) Q= Q a a 1 + t V V nom...equation 12 nom Where Q a is the actual quantity produced and Q is the equivalent quantity of the nominal sized product. 27