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Partnerships for Sustainable DevelopmentNovember 7-10, 2004 12th International Conference of Greening of Industry Network Hong Kong

GreenPartner: A Decision-making Model for Sustainable Partnerships in Construction

Zhen ChenInstitute of Technology and EngineeringMassey University

Palmerston NorthNew Zealand

Heng Li, Stephen C.W. Kong, Qian Xu

Department of Building and Real EstateHong Kong Polytechnic UniversityHung Hom, KowloonHong Kong


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GreenPartner: A Decision-making Model for Sustainable Partnerships in Construction

Zhen ChenMassey UniversityNew Zealand

Heng Li, Stephen C.W. Kong, Qian XuHong Kong Polytechnic UniversityHong Kong

Abstract: Sustainable development in the construction industry requires contractors toquantitatively reduce adverse environmental impacts on construction sites by every possible

way, such as mitigating pollution level and seeking optimum environmental-friendly plans inconstruction planning, and assessing sustainable options for design and material in

construction partnering. Although several quantitative approaches have been put forward and

proved to be efficient in selections of the best construction design, plan, and material based ondistinguishing the degree of their potential adverse environmental impacts, there is still a

research task to develop an effective tool for contractors and clients to conduct sustainabilityassessment in construction partnering. In this regard, a decision-making model is presented in

this paper using analytic network process (ANP) to evaluate the environmental consciousnessand performanceand sustainable performances of partner candidates (maincontractors andsubcontractors) in competitive procurement processes of construction projects. To undertake

this task, this paper firstly reviews sustainable issues and their characteristics relating topartnerships in construction, which are critical factors to evaluate potential adverseenvironmental impacts and sustainability of construction partnerships. These sustainable

characteristics, as well as other criteria generally used in construction partnership assessment,

are then used to structure the decision-making model for evaluating sustainable partnershipsby using ANP. The ANP model named GreenPartner can be used by both contractor andclients when it is necessary to evaluate the sustainable partnerships and select the best partnerduring construction partnering.

Keywords : analytic network process, sustainable construction, partnerships

Introduction

Sustainable construction requires innovation in engineering and management areas, including

construction engineering for sustainability and construction management for sustainability.Regarding innovative construction engineering and management at all stages of theconstruction lifecycle from the initial architectural design and structural design, through to theactual construction, and then the maintenance and control as well as the eventual dismantlingof buildings and civil infrastructures, environmental consciousness and performanceisessential. Although there are some progresses in environmental-friendly design andconstruction, for example, there are quantitative approaches to reducing or mitigatingpollution level in construction planning have been put forward and proved to be efficient in

selection of the best construction plan based on distinguishing the degree of its potentialadverse environmental impacts (Chen, et al, 2000; Li, et al, 2002), there is still a research task

to develop an effective tool for construction contractors to conduct environmental assessmentin partnering.


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In this regard, this paper proposes a decision-making model using Analytic Network Process(ANP) to evaluate the environmental consciousness and performance of partner candidates incompetitive procurement of construction projects. To undertake this task, this paper firstly

reviews environmental issues and their characteristics relating to contractors requirements onmaterial, equipment and design selection driving resource use in construction partnering,which are critical factors in evaluating potential adverse environmental impacts of aconstruction partner. These environmental characteristics, as well as other criteria such asassessments of qualification, profit, risk and constructability, which are generally adopted inconstruction partnering, are then used to construct an ANP model for evaluating constructionpartner candidates. The ANP model named GreenPartner can therefore be used byconstruction contractors when it is necessary to evaluate the potential adverse environmental

performance of partner candidates and thus select the most suitable partner.

The significant contributions of this paper include a set of criteria applied to partner

evaluation regarding to possessing sustainability in construction enterprises, and an ANPmodel for sustainability assessment in construction partnering. Meanwhile, the evidence to be

presented in this paper is the ANP model for selecting the most suitable partner based onenvironmental-friendly concerns and other general criteria for evaluation used in construction

partnering. It is expected that construction contractors can use the proposed GreenPartnermodel for sustainability-concerned evaluation in construction partnerings.

GreenPartnerIndicators

GreenPartner indicators are a group of evaluation criteria which are to be used to set up the

ANP model and select the most suitable partner. Although general evaluation criteria such ascost and qualification are to be adopted, the GreenPartner indicators will involve some newcriteria which can be used to evaluate potential adverse or favourable environmental impactsdue to partnering. Based on this consideration, a procedure of extensive literature review for

collecting comprehensive GreenPartner indicators is assigned. The extensive literature reviewfor collecting GreenPartner indicators is conducted by mining indicators from seven primary

academic & professional information resources in construction engineering and managementfields including the Civil Engineering Database (CEDB) from the American Society of CivilEngineers (ASCE), the ScienceDirect database from the Elsevier B.V., the Compendex

database from the Elsevier Engineering Information Inc., the Engineering News-Record(ENR) executive search engine (enr.com) and magazines from the McGraw-Hill Companies,

the Construction Plus (CN+) search engine (www.cnplus.co.uk) from the Emap ConstructionNetwork, and the advanced search engine of the U.S. Environmental Protection Agency(USEPA) of the United States (epa.gov) and the Environment Agency of the United Kingdom(environment-agency.gov.uk). In addition to these dominant information resources, acommonly used search engine, Google, was also employed to search for any undetectedliteratures. Regarding the search results, the authors retrieved thousands of references relatedto environmental issues in construction partnering. As a result, the GreenPartner indicators areinterrelated with engineering, management, cost, time, resource, surrounding nature, and

society with which the processes of a construction partnering is deployed and executed. Allindicators are listed in Table 1.


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Table 1. GreenPartner indicators & corresponding value of Partner Candidates

Partner CandidatesCluster Node (Environmental Indicators) Unit

A B C

E1:Suitability of design & construction plan % 100 95 95

E2:Reliability of design & construction plan % 100 95 105

E3:Quality of design & construction plan (Expected durability of the building) year 50 45 55

E4:Constructability of design & construction plan % 100 100 100

E5:Flexibility of variation and renovation % 100 90 80

E6:Level of automation % 80 75 85Engineering

E7:Level of cleaner technologies % 80 50 40

M1:ISO EMS accreditation % 100 0 0

M2:ISO QMS accreditation % 100 100 100

M3:Qualification in design & construction (Rate of chartered engineers) % 100 80 65

M4:Experience in similar project % 100 70 50

M5:Computerization in design & construction % 90 85 80

M6:Cooperativity risk in design & construction % 10 20 30

M7:Unionization risk in design & construction % 100 80 60

M8:Suitability of site layout design & controlment % 95 80 60

M9:Pollution controllability in design & construction % 90 75 50Man

agement

M10:Accountability in design & construction % 100 100 100

T1:Duration from design to completion day 620 660 700

T2:Transportation arrangements in construction hour 4.95k 5.28k 5.72k

T3:Interference possibility in design & construction % 25 35 35

T4:Delay risk in design & construction hour 165 150 140

T5:Overrun risk in design & construction % 15 20 15Time

T6:Responsivity in design & construction % 100 90 90

C1:Lifecycle cost of the project tender M$ 200 210 205

C2:Variation possibility in design & construction % 10 20 15

C3:Overrun risk in design & construction % 10 15 10

C4:Financial risk in design & construction % 10 10 0Cost

C5:Emergency risk % 0.1 0.3 0.2

R1:Electricity consumption in construction kWh 40k 55k 55kR2:Fuel consumption in construction MJ 45k 52k 55k

R3:Water consumption in construction ton 3.9k 4.3k 4.5k

R4:Wastewater treatment/reuse rate % 100 50 40

R5:Material availability, serviceability & durability % 100 85 60

R6:Generative material use rate % 20 5 10

R7:Construction & demolition waste generating rate % 1.0 3.0 5.5

R8:Waste reuse & recycling rate % 90 30 45

R9:Equipment requirement in construction lifecycle m-day 29k 35k 36k

R10:Workforce requirement in construction lifecycle m-day 68k 75k 82kResource

R11:Required skills on workforce % 80 60 60

N1:Temperature difference risk in construction lifecycle % 11.0 9.8 9.6

N2:Windstorm risk in construction lifecycle % 2.0 1.8 1.8

N3:Rainfalls risk in construction lifecycle % 1.0 1.1 1.1

N4:Flood risk in construction lifecycle % 0.15 0.25 0.25

N5:Earthquake risk in construction lifecycle % 0.01 0.01 0.01

N6:Landslip risk in construction lifecycle % 0.0 0.1 0.2

N7:Settlement risk in construction lifecycle % 1.5 2.5 3.0

N8:Corrosion risk in construction lifecycle % 1.1 1.1 1.5Nature

N9:Disturbance risk to geoenvironment % 1.2 5.3 6.0

S1:Public health risk in construction lifecycle % 10 15 20

S2:Public safety risk in construction lifecycle % 0.15 0.20 0.30

S3:Landfill burden (waste disposal) in construction lifecycle M$ 0.15 0.30 0.35

S4:Public traffic disruptions in construction lifecycle day 45 60 70

S5:Cargo transportation burden in construction lifecycle t-mile 600k 650k 710k

S6:Legal & responsibility risk % 0.05 0.20 0.30Society

S7:Neighbourhood disturbance in construction lifecycle day 35 45 55


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Table 1 gives a detailed list of GreenPartner indicators collected from the extensive literaturereview. There are total 55 indicators classified into 7 interrelated evaluation clusters inaccordance with the seven GreenPartner indicators. In order to facilitate the evaluation, theauthors give each indicator a specified unit. Assuming there are three partner candidates

including Partner A, Partner B and Partner C, the GreenPartner indicators are then quantifiedby different Partner candidates. So far the three groups of quantified GreenPartner indicatorsare ready to be evaluated by using the proposed ANP model. Before conducting multicriteriadecision-making process to select the most appropriate partner, the ANP model is required tobe set up by using the series of GreenPartner indicators.

ANP Approach

Saaty (1996) developed the ANP and defined it as a general theory of relative measurement

used to derive composite priority ratio scales from individual ratio scales that represent

relative measurements of the influence of elements that interact with respect to controlcriteria. The ANP is a coupling of two parts: one is a control network of criteria and

subcriteria that control the interactions including interdependencies and feedback; another is anetwork of influences among the nodes and clusters. Moreover, the control hierarchy is a

hierarchy of criteria and subcriteria for which priorities are derived in the usual way withrespect to the goal of the system being considered. The criteria are used to compare thecomponents of a system, and the subcriteria are used to compare the elements of a

component. The procedure of using GreenPartner indicators to select the most suitable partneris laid out below from Step A to D:

Step A: ANP model construction

The objective of Step A is to construct an ANP model for evaluation based on determining thecontrol hierarchies such as Engineering, Management, Time, Cost, Resource, Nature, andSociety, as well as the corresponding criteria for comparing the components (clusters) of the

system and sub-criteria for comparing the elements of the system, together with adetermination of the clusters with their elements for each control criteria or subcriteria.

The GreenPartner ANP model is outlined in Figure 1. Inside the GreenPartner ANP model,connections among 7 clusters and 58 nodes are modelled by one-way or two-way and looped

arrows to describe the interdependences existed between each two clusters and each twonodes of different clusters. The 7 clusters are Partner Candidates, Engineering, Management,

Time, Cost, Resource, Nature, and Society. In correspondence with the 7 clusters, there are 58nodes including

- 3 nodes in the cluster of Partner Candidates,- 7 nodes in the cluster of Engineering,- 10 nodes in the cluster of Management,- 6 nodes in the cluster of Time,- 5 nodes in the cluster of Cost,- 11 nodes in the cluster of Resource,- 9 nodes in the cluster of Nature, and- 7 nodes in the cluster of Society.

The 55 GreenPartner indicators listed in Table 1 are thus be used in setting up the ANPmodel.


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Figure 1. The GreenPartner ANP model

Figure 1 illustrates the GreenPartner model implemented using an ANP with all interrelatedclusters and nodes, while the feedback process or the loop of Partner candidates indicates a

circulation for environmental- friendly/sustainable priority evaluation of partner candidates.Concerning the interdependences between two clusters/nodes, the GreenPartner model built

here is a simple ANP model containing feedback and self-loops among the clusters, but withno control model, because there is an implicit control criterion, i.e. sustainability, with respectto which all judgments (paired comparisons) are made in GreenPartner model. For example,when comparing the clusterEngineering to the clusterManagement, no one is obviously moreimportant in sustainability. After cluster comparison are made, relative importance of nodescan be decided in the same way. For example, when comparing the node E2,i.e. Reliability of

the design & construction plan, in clusterEngineering to the node S2, i.e. Public safety risk inconstruction lifecycle, in cluster Society, no one is obviously more important in Sustainability

either.

Step B: Paired comparisons

The objective of step B is to carry out pairwise comparisons among the 7 clusters, as well aspairwise comparisons between each two from the 58 nodes, because they are more or lessinterdependent on each other. In order to complete the pairwise comparisons, the relativeimportance weight, denoted aij, of interdependence is determined by using a scale of pairwise

judgement, where the relative importance weight is valued from 1 to 9 (Saaty, 1996). Thefundamental scale of pairwise judgement is given in Table 2:

Table 2. Scale of pairwise judgement:

1 = Equal3 = Moderately dominant

5 = Strongly dominant

7 = Very strongly dominant9 = Extremely dominant

2 = Equally to Moderately dominant4 = Moderately to Strongly dominant

6 = Strongly to Very Strongly dominant

8 = Very Strongly to Extremely dominant


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In fact, the weight of interdependence is generally determined by decision-makers who areabreast with professional experience and knowledge in the application area. In this study, it isdetermined by the authors as the objective of this study is mainly to demonstrate theusefulness of the ANP model in evaluating the sustainability of the construction partnering.

Table 3 gives a general form for pairwise judgement among indicators and Partner candidates,which is adopted in this study. For example, for the node R2, i.e. Fuel consumption inconstruction, in the clusterResource, the pairwised judgements are given in Table 3, becausethe fuel consumption in the plan from Candidate A is the least among the three plans from allPartner Candidates, whilst the fuel consumption in the plan from Candidarte C is the highest.In this regard, quantitative pairwise judgements are thus conducted in order to definepriorities of each indicator for each Partner candidate, and the judgements are based on the

quantitative attribute of each indicator from each Partner Candidate. Besides the pairwisejudgement between an indicator and a Partner Candidate, the GreenPartern ANP model

contains all other pairwise judgements between each two indicators (IndicatorIi and Indicator

Ij in Table 3) and this essential initialization is set up based on the quantitative attribute of theindicators from each Partner Candidate which is described in Table 1.

Table 3: Pairwise judgement of indicatorIi &Ij

Pairwise judgement 1 2 3 4 5 6 7 8 9

IndicatorIi Candidate A

Candidate B

Candidate C

IndicatorIi IndicatorIj

Note:

1. The fundamental scale of pairwise judgement is given in Figure 2.2. The symbol denotes item under selection for pairwise judgement, and the symbol denotes selected pairwise judgement.

Step C: Supermatrix calculation

This step aims to form a synthesized supermatrix to allow for the resolution of the effects ofthe interdependences that exists between the elements (nodes and clusters) of the ANP model.The supermatrix of the EnvironalPlanning system is a two-dimensional partitioned matrix

consisted of sixteen submatrices (see Figure 2).

It is necessary to note that pairwise comparisons are necessary to all connections (clusters and

nodes) in the ANP model to identify the level of interdependences which are fundamental inthe ANP procedure. After finishing the pairwise judgement, from indicator 1 to n, the series

of submatrices are then aggregated into a supermatrix which is denoted to supermatrix A inthis study (see Figure 2), and it is then used to derive the initial supermatrix in the later

calculation in Step C, and the calculation of the ANP can thus be conducted following theStep CtoD.

Weights defined from pairwise judgement for all interdependences for each individual partnercandidate are then aggregated into a series of submatrices. For example, if the cluster of

Partner Candidates and its nodes are connected to nodes in the cluster ofEngineering,pairwise judgements of the cluster thus result in relative weights of importance between each

Partner candidate and each Engineering indicator. The aggregation of the determined weightsthus forms a 37 submatrix located at W21 in Figure 2.


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Supermatrix A Submatrix

78

97

116

55

64

103

72

31

87654321

8887868584838281

7877767574737271

6867666564636261

5857565554535251

4847464544434241

3837363534333231

2827262524232221

1817161514131211

:

:

NNNNNNNNNodes

CCCCCCCCClusters

WWWWWWWW

WWWWWWWW

WWWWWWWW

WWWWWWWW

WWWWWWWW

WWWWWWWW

WWWWWWWW

WWWWWWWW

W

=

=

JINJIN

JIiJIi

JIJI

JIJI

IJ

nIIww

ww

ww

ww

W

,,

,,

,2,2

,1,1

1L

LLL

L

LLL

L

L

Note:Iis the index number of rows; andJis the index number of columns; both I and J correspond to the number ofcluster and their nodes (I,J (1, 2, , 58)),NI is the total number of nodes in cluster I, n is the total number of columnsin clusterI. Thus a 5858 supermatrix is formed.

Figure 2. Formulation of supermatrix and its submatrix for GreenPartner ANP model

In order to obtain useful information for Partner selection, the calculation of supermatrix is to

be conducted following three substeps which transform an initial supermatrix to a weightedsupermatrix, and then to a synthesized supermatrix.

At first, an initial supermatrix of the ANP model is created. The initial supermatrix consists oflocal priority vectors obtained from the pairwise comparisons among clusters and nodes. A

local priority vector is an array of weight priorities containing a single column (denoted as)...,,...,,,( 21 ni

Twwwww = ), whose components (denoted as iw ) are derived from a judgment

comparison matrixA and deduced by Equation 1 (Saaty, 2001).

JaawI

i

J

j

ijijJIi = =

=

1 1, (1)

WhereJIi

w , is the weighted/derived priority of node i at row Iand column J; ija is a matrix

value assigned to the interdependence relationship of node i to node j. The initial supermatrix

is constructed by substituting the submatrices into the supermatrix as indicated in Figure 2. Adetail of the initial supermatrix is omitted in this paper.

After the formation of the initial supermatrix, a weighted supermatrix is transformed. Thisprocess is to multiply every node in a cluster of the initial supermatrix by the weight of the

cluster, which has been established by pairwise comparison among the four clusters. In theweighted supermatrix, each column is stochastic, i.e., sum of the column amounts to 1.(Saaty, 2001).

The last substep is to compose a limiting supermatrix, which is to raise the weightedsupermatrix to powers until it converges/stabilizes when all the columns in the supermatrix

have the same values. Saaty (1996) indicated that as long as the weighted supermatrix isstochastic, a meaningful limiting result can be obtained for prediction. The approach to arrive


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at a limiting supermatrix is by taking repeatedly the power of the matrix, i.e., the originalweighted supermatrix, its square, its cube etc, until the limit is attained (converges), in whichcase the numbers in each row will all become identical. Calculus type algorithm is employedin the software environment of Super Decisions by Bill Adams and the Creative DecisionFoundation to facilitate the formation of the limiting supermatrix and the calculation result is

omitted in this paper. As the limiting supermatrix is set up, the following step is to select aproper plan alternative using results from the limiting supermatrix.

Step D: Selection

This step aims to select the most suitable Partner Candidate based on the computation resultsthe limiting supermatrix of the GreenPartner ANP model. Main results of the ANP modelcomputations are the overall priorities of Partner Candidates obtained by synthesizing the

priorities of individual Partner Candidate against different indicators. The selection of themost suitable Partner who has the highest sustainability priority is conducted by a limiting

priority weight, which is defined in Equation 2.

)( ,1,,, nCCiCCiCi PlanPlanPlanPlanPlan wwwwwW ++== L (2)

Where Wi is the synthesized priority weight of Partner Candidate i (i=1, , n)(n is the total

number of Partner Candidates, n=3 in this study), and iCPlanw , is the limited weight of Partner

Candidate i in the limiting supermatrix. Because the iCPlanw , is transformed from pairwise

judgements conducted in Step B, it is reasonable to be regarded as priority of the Partner

Candidate i and thus to be used in Equation 2. According to the computation results in the

limiting supermatrix, iCPlanw , = (0.381, 0.103, 0.089), so the Wi= (0.665, 0.180, 0.155), as a

result, the best Partner is Candidate A (see Table 4).

Table 4: Selection of the most appropriate tender

Synthesized priority weight WiANP model No. of nodes

Candidate A Candidate B Candidate CSelection

GreenPartner 58 0.665 0.180 0.155 Candidate A

According to the attributes of each Partner Candidate listed in Table 1, the comparison resultsusing Wi also implies that the most preferable partner for sustainability in construction is the

candidate that regulates the construction practice with least consumption on fuel and water,

lowest ratio of wastage, and lower adverse environmental impacts, etc. This indicates theGreenPartner model provides a quite logical comparison result for the aim of sustainability inconstruction and thus can be applied into construction practice.

Conclusions and Recommendations

This paper presents an ANP model named GreenPartner for evaluating sustainability inconstruction Partner selection. The GreenPartner model is developed based on the ANP

containing feedback and self- loops among the clusters (see Figure 1), but with no controlmodel. However, there is an implicit control criterion with respect to which all judgments are

made in this model: sustainability. The supermatrix computations are conducted for the


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overall priorities of Partner Candidates, and the priorities are obtained by synthesizing thepriorities of the candidates from all the subnetworks of the GreenPartner ANP model. Finally,the synthesized priority weight Wi is used to distinguish the degree of sustainability due to thedeployment of design and construction plans from each Partner Candidate.

In summary, in order to apply the GreenPartner model in practice, it is recommended tofollow the following steps:

1. Original assessment of Partner Candidates on all indicators using Table 1;2. Pairwise comparisons among all indicators using Table 2;3. Supermatrix calculation to transform an initial supermatrix to a limiting supermatrix;4. Calculation of each limiting priority weight of Partner Candidates using limiting

supermatrix and decision-making on Partner selection using Table 4.5. If none of the candidates meets sustainability requirements, adjustments to the plans

are requested and re-evaluation of the plans by repeating the above procedure fromstep 1.

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