A Sustainability Model for the Assessment of Civil Engineer Works
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Recent Advances in Energy, Environment, Biology and Ecology
A Sustainability Model for the Assessment of Civil Engineer Works
CORNELIU BOB, TAMAS DENCSAK, LIANA BOB
Civil Engineering and Building Works
Politehnica” University of Timisoara
Traian Lalescu Street, No. 2, Timisoara
ROMANIA
cbob@mail.dnttm.ro
Abstract: - The present paper presents an evaluation tool proposed by authors, which can appreciate the overall
sustainability of a specific construction work. This specific model is a flexible and target oriented tool, based
on a simple quantitative equation. The analysis can be performed with a relative small number of measurable
parameters, but which offer conclusive results. The final result is a sustainability index, which can be used as
parameter of comparison between different solutions. The applicability of the model is exemplified on three
case studies: Rehabilitation of two buildings, using different strengthening solutions and transportation of
prefabricated RC elements by different means.
Key-Words: - sustainability; assessment; specific model; construction works; transportation;
1 Introduction performances of a building [5]. Although there may
As defined in the Report of the World be different perspectives in the approach of
Commission on Environment and Development: sustainability, most of the rating tools do not respect
Our Common Future (WCED 1987) [1], the definition of sustainability. The three domains
sustainability links together issues of the natural are not treated proportional, environmental aspects
system with social challenges and economic growth, gaining higher importance than social and economic
in a time frame of present and future. This is the performances. Furthermore, most of the rating tools
reason why it is represented as a confluence of the are focused on entire buildings, without permitting
three pillars: economy, environment and society. the sustainability evaluation of individual elements,
The construction industry plays an important role in processes or rehabilitation solutions.
the social - economic development, but also has a The present paper presents an evaluation method
great impact on the local and global environment. It developed by the authors, which intend to be used as
is a major consumer of non-renewable resources and an assessment tool for individual construction
generates a great amount of waste and greenhouse works, respecting the definition of sustainability. It
gases [2]. combines parameters of each dimension and is
A sustainable construction develops the idea of low based only on quantitative values. The model results
embodied energy, reduced greenhouse gas in a Sustainability Index SI which can be used as a
emissions, low operation and maintenance costs, parameter for the comparison of different solutions.
durability, adaptability, comfort and responsibly After a theoretical presentation, the applicability of
sourced materials with recycled contents [3]. the specific model is exemplified on three case
In many countries directives and certificates has still studies: Rehabilitation of two buildings, using
been developed and adopted, which evaluate the different strengthening solutions and transportation
sustainability performances of buildings. The rating of prefabricated RC elements on road, railway or
and certification tools are intended to encourage the water.
implementation of sustainable criteria in the design,
construction, operation, maintenance, and 2 Specific Model
deconstruction of buildings [4]. That means that the Sustainability of construction works can be assessed
traditional decision criteria should be completed using different rating tools. In many countries
with environmental, economic and social ones. The directives and certificates has still been developed
tools can be used as a decision making support, and adopted, which evaluate the sustainability
since they transform the sustainability goals into performances of entire buildings [6]. These rating
quantifiable issues, which evaluate the overall tools offer a global assessment, are very
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Recent Advances in Energy, Environment, Biology and Ecology
comprehensive with high applicability but present The sustainability index can be calculated using the
also some disadvantages [7], [8], [9], [10], [11], following equations:
[12]:
• Some of the models do not cover all three SI = S env + S eco + S soc (2)
dimensions of sustainability;
• The tools include a great number of criteria and n
Pi Re nv
parameters and many of them are very difficult
or impossible to quantify;
S env = ∑
i =1
αi ×
Pienv
;
• The tools are available mainly for entire n n
(3)
Pi Re co Pi Rsoc
buildings, and can be applied with difficulties S eco = ∑β ×
i =1
i
Pieco
⋅; S soc = ∑γ
i =1
i ×
Pi soc
on other types of construction activities;
The authors elaborated an assessment tool, the Where:
specific model, which has the aim to help engineers
to assess the sustainability of different construction SI –Sustainability Index;
works. The specific model is a flexible and target
oriented evaluation tool, which was developed Senv, Seco, Ssoc – sustainability indexes for the
mainly for the comparison of different solutions, but environmental, economic and social dimensions;
can be used also for self-assessment. It has a larger
applicability then the global models and can be used αi – weighting factor of each parameter for the
for partial building works, production of building environmental dimension
materials, rehabilitation works, transport of
prefabricated elements, construction technologies βi – weighting factor of each parameter for the
etc. All the parameters are quantified. The model is economic dimension
based on a quantitative equation, which covers
parameters from each dimension of sustainability. γi – weighting factor of each parameter for the social
Similar approach has been suggested also by [13], dimension;
but it was only a general proposal, without any
practical application. Another similar formula has Pi env , Pi eco , Pi soc - the calculated value for each
been proposed by [14], which intended to solve the
parameter;
problem that for some parameters “higher is better”,
while for other “lower is better”. A disadvantage of
this model is that it takes in account three values for Pi Re nv , Pi Re co , Pi Rsoc - the reference value for each
a single parameter: calculated value, standard value parameter.
and best practice, which are difficult or impossible
to be found for some applications. Furthermore, for The weights for each parameter are established
cases where “higher is better” the model gives not through the estimation of their sustainability impacts
proper results. on micro and macro level. Independent on the
An initial version of the specific model has been importance of each parameter, environmental issues
proposed by the authors in [15], [16], [17]. The contribute with 40%, while economic and social
model was applied on entire buildings, but also on issues each with 30% to the final score, according to
rehabilitation works. It has been continuously the definition of sustainability. Depending on
developed and is presented in the paper. researcher the distribution of the weightings may be
The model can be applied using two proceeding: the changed.
direct appreciation, which results in a sustainability In case of a comparison between different solutions,
index SI and the inverse appreciation, which results the reference value represents the best value from
in an unsustainability index SI . In both cases, the each solution; while in case of a self-assessment the
final score is a dimensionless value between 0 and best practices available are taken as reference
1, where 1 is the best and 0 the worst value for SI values.
and vice - versa for SI . The correlation between the For situations of “higher is better” the ratios in eq.
two indexes is:
Pi
(3), which involve such parameters, become
SI+ SI =1 (1) Pi R
(see Eq. (6)).
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The unsustainability index results from eq. (1) and • Transversal and longitudinal frames with eight
is obtained from: stores and two spans of 5.6 m and eleven bays
SI = S env + S eco + S soc (4) of 3.8m;
• Floors with girder mesh in two directions and a
n
Pienv − Pi Re nv
slab of 100mm;
S env = ∑α ×
i =1
i
Pienv
; • Foundation with a thick slab and deep beams in
(5) two directions.
Pieco − Pi Re co Pi soc − Pi Rsoc
n n
S eco = ∑β ×
i =1
i
Pieco
⋅; S soc = ∑γ
i =1
i ×
Pi soc
From visual examination and non-destructive
measurements no important damages of the RC
structure were observed. Performing a structural
The weighting factors for each parameter remain analysis, including seismic action at present-day
unchanged. level, the following were noticed:
For situations of “higher is better” the ratios in eq. • The drift limitation conditions are not within
(5), which involve such parameters, become the admissible limits at the ground store;
Pi R − Pi • Weakness of reinforcement and insufficient
(see Eq. (7)). anchorage of beam-positive reinforcement at
Pi R the beam-column joint, especially in
The correlation between the two indexes is longitudinal direction.
presented in Figure 1, for a theoretical construction Rehabilitation solutions consist in strengthening of
work with four solutions. Practical applications of the columns located at the ground storey. Some
the specific model are presented in the next chapter. columns were strengthened in 1999 to prevent local
damages due to reinforcement corrosion, while the
others were rehabilitated in 2004 for decreasing the
lateral displacement and for homogeneous column
stiffness at the ground storey [18].
3.1.2 Calculation of the sustainability and
unsustainability indexes
Different solutions have been proposed for the
strengthening of the columns: Coating with steel
profiles, reinforced concrete jacketing, and
composites based on CFRP (lamellas and sheets).
Details of the solutions are presented in Figure 2.
Analysing the characteristics of the solutions,
Fig 1. The correlation between the sustainability several parameters from each dimension have been
and unsustainabiity index selected for evaluation, which were considered the
most representative for a correct comparison. These
3 Applications of the specific model parameters are the following: CO2 emissions arising
from the manufacturing, transport and execution of
3.1 Case study 1 – Rehabilitation of the the building materials, total cost, consolidating time
Western University of Timisoara, Romania (workload), increasing of the capable bending
Subsection moment and stiffness of the consolidated element.
To quantify the parameters, different databases,
3.1.1 Description and assessment of the building codes and bulletins have been used, [19], [20], [21],
The Western University of Timisoara, built in 1962- [22], [23]. Adjusting eq. (3) and (5), the indexes
1963, has many buildings, among them the Main resulted from:
Building that is used as administrative part as well
as classrooms for students. The RC structure
consists of:
CR Co R WR ∆B K
SI = 0.4 × + 0.2 × + 0.1 × + 0.1 × + 0.2 × R (6)
C Co W ∆B R
K
C −CR Co − Co R W −W R ∆B R − ∆B KR −K
SI = 0.4 × + 0.2 × + 0.1 × + 0.1 × + 0 . 2 × (7)
C Co W ∆B R KR
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Fig.2 Strenghtening solutions using steel profiles, RC
Where C, CR, Co, CoR, W, WR, ΔB, ΔBR, K, KR are indexes, is summarized in Table 1. The best value of
given in Table 1. each parameter has been considered as reference.
The specific value of each parameter, for 1m2 of
rehabilitated element, with their corresponding
Table 1 Rehabilitation of the Western University using different solutions
Western University of Timisoara
Rehabilitation solution
Steel Profiles RC Jacketing CFRP Reference
Parameters
CO2 , C, Emissions [kg/m2] 41.70 93.1 25.47 25.47
Cost, Co, [euro/m2] 91.66 68.4 155.70 68.4
Workload, W, [man-hour/m2] 4.29 5.9 1.86 1.9
Increase of bending moment,
62.37 57.2 58.26 62.37
ΔB, [kNm/m2]
Stiffness, K, [kNm/m2] 241.61 292.6 169.13 292.62
Sustainability Index SI 0.702 0.633 0.797 1
Unsustainability Index SI 0.298 0.367 0.203 0
A graphical representation of the results in Figure 3,
underlines the correlation between the two indexes.
Each solution showed advantages and
disadvantages: coating with CFRP had by far the
lowest CO2 emissions and shortest consolidating
time, but without assuring the drift limitation
conditions, which was the main objective of the
rehabilitation. Furthermore it was very expensive;
RC jacketing resulted in a good stiffness, relative
good price, but high workload in comparison to
coating with steel profiles. By applying the specific
model, the most sustainable solution proved to be Fig. 3 Indexes of the three solutions
the CFRP procedure; RC jacketing and steel profiles
have comparably SI, but as final solution the coating 3.2 Case study 2 – Rehabilitation of the
with steel profiles has been applied due to its Timisoreana Brewery, Romania
stiffness.
3.2.1 Description and assessment of the
building
The Timisoreana Brewery is a reinforced concrete
framed structure, with one section of five storeys
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and a tower of nine storeys. The brewery and the The necessary rehabilitation of the RC structure was
tower were built in 1961 and the extension in 1971. adopted for all types of damages and has been
The industrial building’s vertical structure is a performed in two steps. First, in 1999 the main
spatial frame, while the foundation system consists girders, secondary beams and the columns were
of isolated RC foundations under columns. The RC strengthened for both local damage and inadequate
monolithic floors are made of main girders, reinforcement, by jacketing with reinforced
secondary beams and a one way reinforced slab. concrete.
From visual examination and non-destructive in situ In 2003 due to continues operation and subsequent
assessment several problems have been identified at damage of the structure, new assessment was
slabs, main girders, secondary beams and columns: required. It was found that some beams and one
• Concrete cover spalled over large surface; column were characterized by inadequate
• Complete corrosion of many stirrups and deep longitudinal reinforcement and shear reinforcement
corrosion of main reinforcement; as well as corrosion of many stirrups at beams. The
• Some broken reinforcement; strengthening solution adopted was based on CFRP
• Dangerous inclined cracks; composites [24].
The damages were mainly produced by concrete
carbonation and chloride ion penetrations, favoured 3.2.2 Calculation of the sustainability and
by high RH (≈80%) and temperature (over 40°C). unsustainability indexes
Performing a structural analysis, including seismic As in the case of the first example (Western
action at present-day level, the following were University of Timisoara) different rehabilitation
noticed: solutions were proposed. Details of the solutions are
• High vulnerability to seismic actions due to presented in Figure 4 and Figure 5.
structural irregularities; The parameters and indexes have been determined
• Some elements were characterized by similar but with slight modifications (structural
inadequate longitudinal reinforcement (column) stiffness was not a problem of vulnerability). The
and shear reinforcement (beams). results are summarized in Table 2, separately for
column and girder.
Fig. 4 Strengthening of the column by RC jacketing and CFRP composites
Figure 5: Strengthening of the girder by RC jacketing and CFRP composites
Table 2 Rehabilitation of the Timisoreana Brewery using different solutions
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Brewery Timisoreana
Rehabilitation solution Column Girder
RC RC
Parameters CFRP Ref. CFRP Ref.
Jacketing Jacketing
CO2 Emissions, C, [kg/m2] 141.19 14.88 14.88 25.32 7.75 7.75
Cost, Co, [euro/m2] 92.20 85.23 85.23 36.77 40.73 36.77
Workload, W, [man-hour/m2] 8.58 1.84 1.84 32.34 9.19 9.19
Increase of bending moment,
55.07 11.65 55.07 64.03 20 64.03
ΔB, [kNm/m2]
Sustainability Index SI 0.548 0.763 1 0.751 0.774 1
Unsustainability Index SI 0.452 0.237 0 0.349 0.226 0
For both elements, the most sustainable solution is 690km. The elements are handled ones at
proved to be the coating with CFRP. In 1999 the loading and ones at downloading. Noise is
solution with RC has been chosen due to the lack of considered as the maxim level of sound
experience of the authors in the field of CFRP at produced by the convoy of trucks [25].
that time. In 2003 the sustainable solution has been Scenario 2 – The transport on railway is done
applied fulfilling all technical and technological
by freight trains with cars up to 50t loading
requirements.
capacity on a distance of 720km. Having rail
3.3 Case study 3 – Transportation of access to the manufacturer, the elements are
prefabricated RC elements loaded directly in the cars, skipping
supplementary handling. At the final destination
3.3.1 Description of the cargo the elements will be handled twice. The noise
The aim of this example is to demonstrate the level of the train has been considered at a speed
applicability of the specific model also on other of 70km/h [26].
types of construction activities. An industrial hall Scenario 3 – The combined transport is
made of prefabricated reinforced concrete elements necessary because Timisoara has no direct
have to be transported from Timisoara to Galati access on the Danube River. The elements are
(690km on road). The structure consists of 97 transported on road by trucks to Moldova Noua
elements (beams and columns), weighting 450t. Due (150km), from there to Galati on barges
to the great mass, four transport opportunities have (950km), repeating the load and download
been evaluated: on road by trucks, on railway by
process two times. The noise level of trucks has
train, on inland water (Danube River) by barge and
a combined solution by truck and barge, because in been considered in this scenario.
many situations there is no direct access on inland Scenario 4 – This scenario considers that the
water (like in case of Timisoara). entire transport is done on water, with two
processes of loading and downloading. Because
3.3.2 Calculation of the sustainability and barges have no disturbing effect on settlements,
unsustainability indexes the minimum noise level imposed by standards
has been considered.
For the evaluation of the sustainability of each For all scenarios, the values for specific CO2
transport method different parameters have and dust emissions, costs and duration were
been assessed. The most important were the taken from different databases and catalogues [
CO2 emissions, costs, transport duration, [27], [28], [29], [30], [31], [32]. All specific
emissions of dust and noise. To calculate the values were obtained for a cargo of 450t and the
sustainability index the following scenarios minimum distance of 690km.
have been considered: Adjusting eq. (3) and (5) the indexes resulted
Scenario 1 – The transport on road is done by from:
trucks with cargo capacity of 20t. The distance
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CR Co R DR PM R NR
SI = 0.4 × + 0.2 × + 0.1× + 0.1× + 0.2 × (8)
C Co D PM N
C −C R
Co − Co R
D−D R
PM − PM R N − NR
SI = 0.4 × + 0.2 × + 0.1 × + 0.1 × + 0.2 × (9)
C Co D PM N
The results are summarized in Table 3.
Table 3 Transportation of prefabricated RC elements by different means
Transport of prefabricated RC elements Timisoara - Galati
Transport solution Combined Only
Truck Train
Truck Barge Barge Ref.
Parameters 690km 720km
150km 950km 1100km
CO2 Emissions, C,
123.13 24 46.14 22.43 22.43
kg/1000tkm]
Cost, Co, [Euro/1000tkm] 39.4 56.04 35.26 0.04 0.04
Duration, D, [hour/1000tkm] 0.11 0.12 0.30 0.31 0.11
Dust (PM10+VOC), PM,
0.13 0.04 0.06 0.04 0.04
[g/1000tkm]
Noise, N, [dB] 90 110 90 50 50
Sustainability Index SI 0.305 0.689 0.412 0.931 1
Unsustainability Index SI 0.695 0.311 0.588 0.069 0
Each mean of transport shows advantages and evaluation models, sustainability issues can be
disadvantages. Transportation on water is by far assessed and quantified, which may help engineers
the most sustainable solution, even if the in the decision making regarding different solutions.
duration is much higher than for other cases. The presented specific model, resulting in a
But its main disadvantage represents its sustainability index of different construction works,
offers many advantages and opportunities. It is a
applicability. Barges need ports and access to
method to appreciate the overall sustainability of a
water, which is not possible in all situations. specific application, which finally leads to optimum
Like in the case of Timisoara – Galati, a design solutions. It is a flexible tool, based on a
combined alternative was proposed. Transport simple quantitative equation, which can be applied
by trucks to the nearest port and then further on on a series of practical problems. The analysis can
water. Due to great CO2 and dust emissions of be performed with a relative small number of
the trucks this alternative is becoming less measurable parameters, but which offer conclusive
sustainable. Transport by freight trains resulted results. Due to its flexibility, the proposed model
to be the most viable solution in this situation. can be applied on entire building, building elements,
Transport by trucks is suitable for smaller rehabilitation methods, production of construction
cargos, and for places where none of the above materials, transport solutions, construction
technologies etc.
mentioned means can be applied, due to the
From the presented case studies some useful
lack of infrastructure. conclusions can be underlined. A sustainable
solution not always represents the best solution, it
3 Conclusions must be also technically useful; for instance, the
Sustainability is defined as the confluence of the CFRP solution resulted as the most sustainable, but
environmental, economic and social dimensions. due to its insufficient stiffness, could not fulfil the
For a correct assessment of sustainability technical requirements. Similar problem appeared in
performances, all the three dimensions should be the case of the transport of prefabricated elements.
treated in equal way. The construction industry has Although the most sustainable solution proved to be
great environmental impacts, contributes to the the transport on water by barge, due to the lack of
economic growth, but has also social responsibility. direct access to water, a less sustainable solution
It should implement sustainability issues in all types had to be obtained.
of activities, including entire life cycle. Using
ISBN: 978-960-474-358-2 167Recent Advances in Energy, Environment, Biology and Ecology
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