Structural Investigation of Drini River Bridges, Case Study of
Structures Analyses
IRALDA XHAFERAJ
Civil Engineering Department,
Polytechnic University of Tirana,
“Dëshmoret e Kombit” boulevard, square “Nënë Tereza”,
Tirana,
ALBANIA
Abstract: - The Drini is the longest river not only in Albania, but in the west Balkan region, with a total length
of 285 km. It is well known for a lot of number and famous bridges constructed since the antiquity period and
continuing nowadays. This paper is focused on the structural development of bridges that used to be called
“Kukësi Bridges” located over the White and Black Drini rivers. The old bridges were built and designed in
1974 using KTP Albanian national codes, carrying the first-class road until the building of a national road. The
new bridge is in the final construction stage with the reconstruction of the national road highway, designed with
advanced requirements regarding Eurocode standards. This paper analyses the structural bridges' progress
related to historical and technical points of view.
Key-Words: - Bridges structure, Eurocode loads, Technical design code of Albania, Drini river bridges,
Historical bridges, bridge geometry, standard, load model.
Received: July 6, 2023. Revised: February 27, 2024. Accepted: March 23, 2024. Published: May 16, 2024.
1 Introduction
Historical investigation of Albanian structural
bridges may be characterized by the fourth
development era. In the first period of the Antiquity
era, three types of bridges structure were
constructed, [1]:
1) wood bridges with stone abutments;
2) one archway stone arch bridge (Çobanaj,
Kushi, Muriqan, Kasabashi, Sharova bridge,
etc.);
3) multi-archway stone arch bridges
(Bashtova, Qukesi, Goliku bridge, etc.).
The second period in the Middle Ages era (VII
and XV century) is not characterized by any special
structure bridges. The third period, between the XV
and XIX centuries, built 72 cultural monument
bridges (Mesi bridge on Shkodër, Veziri bridge on
White Drini River, Velabishti bridge on Berat,
Luma bridge on Drini River, etc.), [1]. The fourth
period of the XX century, has been characterized by
the building of concrete, reinforcement concrete and
prestress bridges designed with technical Albanian
codes, [1]. The 1990s years and nowadays, are
characterized by the great development of road
infrastructure in the period designed and constructed
according to Eurocode requirements, [2]. Previews
structural investigation studies have been presented
that it’s important to understand and identify the
historical structure evaluation and development, [3],
[4], [5].
This paper described a structural investigation of
the old and new ‘Kukësi” bridge on the Drini River.
Figure 1 shows an illustration view of the two
bridges.
This paper described a structural investigation of
the old and new ‘Kukesi” bridge on the Drini river.
Figure 1 shows an illustration view of the two
bridges.
Fig. 1: Old and new bridge over Drini River
illustration
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2 Traffic Moving Loads and Material
with Technical Albanian Codes
Old “Kukësi bridges” were built in the 1974 year,
situated over the Black and White Drini Rivers
carrying the first class road before the construction
of the national highway Albanian road, currently the
second highway road. It is a four-span girder beam-
type scheme. The substructure was designed as a
reinforced concrete monolithic construction system
on a supported span with a cantilever length of
50.28 m over the pile and prefabricated beams with
a 30.6 m length on the middle bridge span. Piles no.
1 and no. 2 are realized using a four-column bridge
system with φ = 2.4 m diameter dimension.
Columns have been realized with Fe-44k steel
reinforced bar and C20/25 concrete class. C12/15
concrete class and st-3 reinforcement steel are used
for plinth foundation construction. Longitudinal
profile views of the bridge set out on the White and
Black Drini Rivers are presented in Figs 2 and 3.
Cross sections 1-1 and 2-2 used on middle and
supported span bridge length, respectively, are
shown in Fig. 4.
Fig. 2: Longitudinal profile and plan view of bridge
over Black Drini River
Fig. 3: Longitudinal profile and plan view of bridge
over Black Drini River
Fig. 4: Cross Section bridge 1-1, 2-2 on middle and
supported span length
According to KTP Albanian codes, the N-300
traffic moving load scheme is used for highway road
type A calculations, which is composed of a range
of loads with a distance of 10 m equally dispersed.
The total vehicle value weight is Pi= 300 KN. K-
800 control load scheme is the only vehicle with an
800 KN weight load. Figure 5 shows N-300, K-800
moving and control load schemes respectively, [6],
[7].
Fig. 5: Traffic moving load N-300 and K-800 based
on KTP codes, [7]
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3 Traffic Moving Loads and Material
with Eurocode. New Bridge over
Drini River Case Study
The New Drini Bridge, designed for the
reconstruction of the national highway road,
consists of three spans, spans 20+270+20 length
respectively. The main structure has a total length of
23.213 m and two side platforms with a width of
1.762m. Figure 6 presents a typical bridge cross-
section along the arch length. A longitudinal view
of a new bridge is shown in Figure 7.
Fig. 6: Typical bridge cross-section along the arch
length
Fig. 7: Longitudinal view of the new Drini Bridge
The indicative design working life for the new
bridge is 100 years, for the number 5 category of
monumental bridge structures as it is shown in
Table 1, according EN 1990:2002, [8], [9].
Table 1. Indicative design working life EN
1990:2002, [8]
Design working
life category
Indicative design
working life
(years)
Examples
1
10
Temporary structures
2
10 to 25
Replaceable structural
parts e.g gantry girders,
bearings
3
15 to 30
Agricultural and
similar structures
4
50
Building structures and
other common
structures
5
100
Monumental building
structures, bridges, and
other civil engineering
structures
Mechanical properties of steel grades are
presented on Table 2.
Table 2. Mechanical properties of steel grades, EN
10025-2:2004 [10]
Young modulus:
E = 210 000 N/mm2;
Shear modulus:
G = E / [2(1+ν)] = 80770
N/mm2;
Poisson ratio:
ν = 0,3;
Coefficient of thermal
expansion:
α = 12 × 10-6 for °C-1;
Density:
ρ = 7850 kg/m3
Slip-resistant bolted connections on
serviceability limit states are designed regarding EN
1993-1-8, [10], [11], [12], B category. The
preloaded designed force of M27 bolts is verified by
F(p, cd)=290 kN. The slipped coefficient of bolted
connections ks is equal to 0.41. The ultimate limit
states verification capacity is done for A category
according to EN 1993-1-8, [13], [14], [15].
Slip designed with preloaded bolted resistance:
  


 (1)
where, Fs,Rd = is the resulted bolt related shear
load,
μ = is the friction coefficient,
γM5 = is the safety factor.
Slip designed for bolted resistance to all slipped
plans:
 

 (2)
where αv is the coefficient of thermal expansion,
fubA is the steel tensile stress,
γM2 = is the safety factor
Shear resistance of bolted connections plan is
limited to 2/3 of the resulting bolt 󰇛 󰇜:

󰆒 (3)
Reinforced steel class is taken B450C, [13],
according to Eurocode requirements. Mechanical
properties of steel grades and reinforced concrete
C40/50 are shown in Tables 3 and 4, respectively
[16], [17], [18], [19], [20].
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Table 3. Mechanical properties of steel grades
Steel B450C
Es
Young modulus
200
000
N/mm2
γs
Safety factor
1,15
fyk
Characteristic yield strength
450
N/mm2
fyd
Design yield strength
391,30
N/mm2
εud
Ultimate strain
0,0675
εyd
Elastic limit strain
0,0022
Table 4. Mechanical properties of reinforced
concrete C40/50
Concrete C40/50
Rck
Characteristic concrete cube
compressive strength
50
N/mm2
fck
Characteristic concrete cylinder
compressive strength
40
N/mm2
γc
Partial factor
1,5
fcm
Mean value of concrete cylinder
compressive strength
48
N/mm2
fctm
Mean value of axial tensile strength
3.5
N/mm2
Ecm
Young modulus
35 000
N/mm2
fcd
Design compressive strength
26.7
N/mm2
fctk
Characteristic tensile strength
2.5
N/mm2
fctd
Design tensile strength
1.7
N/mm2
Figure 8 presents a parabola rectangle diagram
adopted for concrete verification.
Fig. 8: Parabola rectangle diagram adopted for
concrete verification
Ultimate concrete limit states deformation for
structure calculation are:
 ;   (4)
Table 5 shows exposure class determination
according Eurocode standards, [18], [21].
Table 5. Determination of exposure class
Class designation
Description of the
environment
Informative
examples where
exposure classes
may occur
XC3
(top of the slab)
Moderate humidity
Concrete inside
buildings with
moderate or high
air humidity
XC4
(bottom of the
slab)
Cyclic wet and dry
Concrete surfaces
subject to water
contact, not within
exposure class
XC2
cmin,b is the minimum cover due to because the
bond requirement is based on EN 1992-1-1:2004,
[20], [21]. The minimum cover values on the top
and bottom face slab due to bond requirement,
environmental conditions, additive safety elements,
reduction of cover for use of stainless steel, and
additional protection are taken as below:
The top and bottom cover face slab values
calculations are shown in Table 6.
Table 6. Top and bottom face slab values
Cover slab values
Cover (mm)
cmin,b
cmin,dur
Δcdev
cnom
The top face of
the slab
20
20
10
30
The bottom
face of the slab
25
25
10
35
Moving load LM1 for highway bridges
according to Traffic Eurocode loads used for
structure analysis is taken as shown in Figure 9,
[22].
Fig. 9: Load Model No. 1: (a) Application of TS and
UDL along the longitudinal axis; (b) Application of
LM1 on the notional lanes
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Plate stress compression analysis according to
the Eurocode standard is shown in Figure 10, [23]
Fig. 10: Plate stress before initial prestress
6 Conclusions
This paper aims to provide a historical investigation
of bridge requirements designed with KTP Albanian
code and Eurocode requirements. It describes a case
study analogy of “Kukësi” bridges, the first one
designed and constructed with prior technical code
and the second with EN standard.
The use of mechanical material properties and
traffic load values application with prior and
nowadays codes are presented.
The bridge structure analysis progress is
described from historical and technical points of
view. This study revealed the use of the low
concrete and steel grade class in the old bridges
designed with KTP codes, while higher values of
concrete and steel grade classes are used for the
construction of currently designed bridges.
The length of the main span of the old bridge is
about 80 m length, comparing the 270 m span length
of the new bridge, which has approximately three
times longer span than the first one, as a result of
new technological and material progress.
The difference is also observed in the use of
traffic load values with KTP and Eurocode standard
structure analysis, increasing carrying capacity.
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Contribution of Individual Authors to the
Creation of a Scientific Article (Ghostwriting
Policy)
The paper’s concept was set out by Iralda Xhaferaj.
Sources of Funding for Research Presented in a
Scientific Article or Scientific Article Itself
No funding was received for conducting this study.`
Conflict of Interest
The authors have no conflicts of interest to declare.
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