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International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 6, June 2017, pp. 411–422, Article ID: IJCIET_08_06_045
Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=6
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication Scopus Indexed
SEISMIC ANALYSIS AND DESIGN OF CARGO
BERTH
Ramesh Kannan
Assistant Professor, Division of Structural and Geotechnical Engineering,
School of Mechanical and Building Sciences,
VIT University Chennai Campus, Chennai –127, India
ABSTRACT
Port facilities play a vital role in the flow of a country’s import and export. Cargo
berth is one of the berthing structures in ports for the purpose of handling different
types of bulk cargo and it is considered to be a challenge in itself due to the complicated
design sequence and the consideration of various loads acting upon it. Earthquakes
have caused severe damage to such structures in the past and these risks should be
eliminated at any cause. This paper illustrates the seismic analysis of a cargo berth
using two different methods, the linear or equivalent static analysis is carried out using
IS 1893 codes with which the natural time period, base shear and seismic coefficient of
the structure are arrived at. The second method of analysis used is nonlinear static
method and it is done in the form of pushover analysis using SAP 2000 to model the
cargo berth. The base displacement vs. base shear known as the pushover curve is
obtained. By using the pushover analysis a realistic behavior of the structure can be
studied i.e. the various hinge properties, mode shapes and behavior of the structure at
each step of load increment can be analyzed. In addition to this the capacity curve and
demand spectra are plotted graphically to obtain the performance point and levels,
which is the essential outcome of this analysis. The results are obtained by using the
ATC 40 and FEMA 356 guidelines and the acceptance criteria of the structure is also
checked by analyzing the hinge properties. The main objective of the analysis is to
compare the results thus obtained from both the linear static analysis and non-linear
static methods. This comparative study is approached in order to obtain efficiency in
terms of various factors. A performance based seismic analysis is aimed at and using
both the results the conventional design of cargo berth can be optimized to meet the
performance demand and cost effectiveness.
Key words: Equivalent Static Analysis, Pushover Analysis, Acceptance Criteria, Hinge
Formations, Performance Point, Optimization.
Cite this Article: Ramesh Kannan, Seismic Analysis and Design of Cargo Berth.
International Journal of Civil Engineering and Technology, 8(6), 2017, pp. 411–422.
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Ramesh Kannan
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1. INTRODUCTION
Various port structures enable the flow of export and import of a country. Berthing facilities is
one of them, it is a platform support extending from the port towards the sea is used for the
purpose of berthing and mooring ships or vessels. The platform is also used for the purpose of
handling goods. Depending on the type of vessels berthed and the purpose of use the type of
berth to be laid is decided [1]. Cargo berth is used for the loading, unloading and handling of
bulk cargo such as vehicles, construction equipment, machinery etc. A cargo berth consists of
various structural elements such as: piles, pile muff, transverse and longitudinal beams, deck
slab, fenders and bollards etc. The construction sequence and design of the berth is done as per
IS 4651 codes.
Earthquake damage is a severe threat and to eliminate the risks of seismic failure of the
berth, for example the Kandla and Kobe port, and to study the behavior of the berth, seismic
analysis is vital. Linear or Equivalent static analysis is carried out in the assumption that the
structure remains elastic for the level of ground motion i.e. The effects of an earthquake are
assumed to be the same as the ones resulting from the statically transverse loadings. This
method is carried out by following standard codes and in this case the IS 1893Part-1 [3].
Nonlinear analysis can reduce the uncertainty of the assumption of linear static analysis, as the
structure in real implies greater inelastic demand. Pushover analysis makes use of a computer
model to analyze the real time behavior of the structure. The model is subjected to a lateral load
of a certain shape, whose intensity is slowly increased and the sequence of yielding, plastic
hinge formations, and failure of various structural components is recorded. The performance
of the structure can also be studied in the form of graphical and tabular results using the ATC
40 acceptance criteria and other set of codes [4].
The objective of this research is to optimize the conventional design in order to bring better
performance of the structure while maintaining the cost effectiveness as well. The performance
based design is thus highlighted by illustrating the various hinge properties, acceptance level
for each level of loading and the performance levels obtained graphically. Yet the scope of the
project is limited to seismic analysis of cargo berth by the use of IS 1893, ATC 40 and FEMA
356 code of practice.
A performance based seismic analysis was previously carried out by Syed Ahamed (2013),
where the various analytical approaches were performed to identify the seismic demand and to
determine the performance levels and a comparative study was carried out. The real time
behavior of the structure was highlighted [5]. Similarly pushover and time history analysis and
the importance of ductility in platform design was discussed by Frank.J et al (2013) [6].
Following these analyses Sofan.Y Ahmed (2013) discussed in detail the pushover analysis
(inelastic structural analysis) and highlighted the performance based design and retrofitting
techniques using acceptance criteria illustrated in ATC 40 [7].
S. Naga Sujani et al (2012) illustrated clearly the study of hinge properties and acceptance
criteria using ATC 40 codes and also presented a few retrofitting techniques for structural
elements beyond the acceptance levels [8]. Bilge Doran et al (2012) implemented the same
performance based design in pile-wharf design, where the performance evaluation of the
structure was also carried out including the analysis of acceptance levels of the structure [9]. A
series of research on seismic methods and analysis of port structures was carried out in the year
of 2009 up to 2004, G.J.Rix at al (2009) summarized the basic concepts and methods that are
being developed to address the analysis of seismic risks to a port-wide system of berths. It also
discussed how results from such analyses can guide port decision makers in making a more
informed selection of design, retrofit, operational, and other seismic risk management options
that may be under consideration [10]. Vahdani.S et al (2007) followed the same techniques of
seismic capacity study for an existing wharf at the Port of Oakland, which was accomplished
Seismic Analysis and Design of Cargo Berth
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by performing nonlinear pushover analysis. The performance levels were found out and it was
determined that the wharf at Berth 59 is not expected to collapse due to events with return
periods of 2500 years [11].
2. METHODOLOGY
Figure 1 Research methodology
3. DESIGN DATA
The proposed cargo berth is set to be constructed at Kandla port, Andhra Pradesh. Since it is a
sheltered one, the tidal forces need not be taken into consideration. The proposed area for the
construction of the berth is 300m x 30m. A survey of vessels berthing at the location of the
berth is carried out and the final vessel details with reference to IS 4651 part III are as given in
Table I.
Table 1 Vessel Data
Vessel type DWT Length (m) Beam (m) Draft (m)
Bulk Carriers 120,000 277 45.8 13.4
The given average temperature variation at the berth location is ± 20°C. The wind speed
under operating and storm conditions is 26m/s and 50m/s respectively. Depending upon the
geo-technical data the design dredge level is set to level of (-) 16.0m CD. Hence the top deck
Conclusion
Design Optimization
Analysis of results
Push Over Analyses in SAP2000
Equivalent Static analysis
Conceptual design and modelling of Berth in STAAD.Pro V8i
Design Load Calculations
Design Data collection
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level is estimated to be (+) 5.70m CD based on the dredge level, slope and the total depth of
the sea bed. It is proposed to use M40 grade of concrete and Fe500 grade of steel both super
structure and sub structure and also water cement ratio of 0.45.
4. LOAD CALCULATIONS
The different types of loads are calculated as per IS 4651 Part III. The load combinations are
taken as per IS 4651Part-4. The different types of loads are as follows:
The different types of loads are calculated as per IS 4651 Part III. The different types of
loads are as follows:
4.1. DEAD LOAD
The dead loads are assessed by considering following unit weights of materials.
• Unit weight of concrete 25 kN/m3
• Unit weight of steel 78.5 kN/m3
• Sea water density 10.30 kN/m3
4.2. LIVE LOAD
• Uniformly Distributed Live load of 5.0 t/m2
• Vehicular load: IRC Class AA, IRC 70R (Tracked and wheeled)
• Crane load is 0.75 t/m2
4.3. BERTHING LOAD
The load acting towards the berth when the ship is berthed is called as berthing load. The impact
or vibration effect on the berth due to this load is minimized by the use of fenders attached to
the berths. The berthing energy is calculated as per IS 4651 Part 3.
• Type of berthing: Sheltered site and difficult berthing conditions
• Berthing velocity: 0.10 m/s
• Approach of 10°
Berthing Energy, E = (WD * V2 / 2g) x Cm x Ce x Cs (1)
Mass Co-efficient, Cm = 1 + (2D/B) (2)
Eccentricity Co-eff. Cs = (1 + (l / r) 2sin2 θ)/ (1+ (l / r) (3)
Where the values of D = 13.4m, B = 45.8m as per Table 2.
And l/r =1, θ = 10° as per IS 4651 Part 3 Cl.5.2.1.3.
Hence
• Cm = 1 + ((2 x 13.4) / 45.8) = 1.280
• Cs = [1 + (1 x 2 x sin2 10° 0.95)] / [1 + 1] = 0.95
• E = [(144000 x 0.102) / 2 x 9.81] x 1.280 x 0.4 x 0.95 = 364.465 kN/m
Hence berthing Reaction, R = 132.56 T
From Trelleborg standards adopting SCN1200 E1.2 Super Cone Fender.
Spacing provided between fenders = 2.1m.
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4.4. MOORING LOAD
The mooring load acts away from the berth when the removal of the ropes is initiated or due to
the action of wind.
F = Cw x Aw x P (4)
Aw = 1.175 Lp (Dm - Dl) (5)
Where,
• Shape factor adopted, Cw = 1.3
• P = 0.9 as per IS 875
• Wd = 0.9 x 47 = 1325.4 T
• Lp = 0.95 x 277 = 263.15 m
• (Dm - Dl) = 20.6 – 17.6 = 3m
Hence
Aw = 1.175 x 263.15 x 3 = 927.603 Sq.m
F = 1.3 x 927.603 x 0.9 = 1598.28 kN
Hence Mooring force per bollard = 0.6 x 1598.28 kN = 958.96 kN
Hence providing a bollard of approximately 1000 kN capacity
4.5. WIND LOAD
The wind load confirming to IS: 875 part 3 is calculated as follows:
• Design wind speed Vz = k1 x k2 x k3 x Vb
• k1 = 1, k2 = 0.99, k3 = 1.0
• Vz = 1 x 0.99 x 1 x 26 = 25.74 m/s (Under normal condition)
• Vz = 1 x 0.99 x 1 x 50 = 49.5 m/s (Under storm condition)
4.6. LOAD COMBINATIONS
Load Combinations are taken as per IS 4651 Part IV and are tabulated as in Table-II. And
defined in Staad. Pro as in Fig 3.
Load combinations as per IS: 4651 Part 4
Loading Limit state of serviceability Limit state of collapse
I II III IV V VI VII VIII IX X
Dead load 1 1 1 1.5 1.5 1.2 1.2 0.9 1.2 0.9
0.9
Vertical live load 1 1 1 1.5 1.5 1.2 1.2 0.9 1.2 0.9
0.9
Earth pressure 1 1 1 1 1 1 1 1 1 1
Berthing force 1 1.5
Mooring force 1 1.5
Seismic force 1.5 1.5
Wind force
(operational) 1 1 1 1 1 1.2 1 1
Wind force
(extreme) 1.5 1.5
Wave & current 1 1 1 1 1 1.2 1 1 1 1
Temperature 1 1
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5. DESIGN OF BERTH
The pile dimensions assumed are as per the given dredge level and top deck level from the geo-
technical data such as the founding and fixity level. The height of the pile is 46 m. The diameter
of the pile is 1m based on the guidelines from IS 4651. The pile capacity is then calculated with
the following equation, to arrive upon the number of piles required.
Qu = Ap x (Cp x Nc + 0.5D x γNγ+Pd x Nq) + (αCi + Kx Pdi x tanδ) x Asi– Ws (6)
Where,
D = 1 m, Ap = 0.785m2, Ws = 79.13 T, Dredge Level = 16 m, Pile Cut off Level = 5m
Nc = 46, Nq = 55, Nγ = 48, Pd = 0.67, Pdi = 13.8, K = 1.46, Adhesion factor, α = 0.3,
Normal Condition: Qu = 305.38 T
Compression Capacity of the Pile, Qcp = Qu ‐ Ws = 226.25 T
Seismic Condition:
Compression Capacity of the Pile = 1.25*Qcp = 381.73 T
No. of Piles required = Total Vertical Load / Compression Capacity = 29694.76/226.25 ≈
132 no’s.
The pile center to center distance is even longitudinally and varies transversely depending
upon the crane locations. This is estimated using the Staad. Pro model. Hence the clear span
and clear cover for the design of the beam is determined. The transverse beam and longitudinal
beam are designed as per IS 456 as follows:
Transverse Beam: Clear span = 11m, Bearing thickness = 0.50m,
Leff = 11.5m, Slab thickness, Df = 0.15m, Span/depth = 12 ≈ D=1.3m (Cover=50mm)
bw = 400mm (As per IS 456), Bf = (Lo/6) + bw + 6Df = 1.25m
Longitudinal beam: Clear span = 7m, Spacing between the beams = 2.5m
Span / depth = 12 ≈ D=1.1m (Cover = 50mm)
The deck slab is designed as a two way slab in Staad Pro. The model of the cargo thus
deigned and modelled in Staad Pro, by applying the material properties and defining the various
load combinations. The design model thus obtained is illustrated in Fig.2.
Figure 2 Cargo Berth Design and Loading in Staad Pro
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Figure 3 Load application on berth
6. LINEAR STATIC ANALYSIS
This method is carried out using the IS 1893 guidelines. The time period and the base shear can
be calculated and the seismic co-efficient is then calculated which when multiplied by the total
vertical load of the structure gives the seismic load distribution along the structure. This load
is in turn defined as in Fig.2 in the Staad Pro model and the final design is obtained.
Design seismic co-efficient, Ah = Z I (Sa/g) / (2R)
Where, Zone factor, Z = 0.16, Importance factor, I = 1.5, Response reduction factor = 3
T = 0.075 x H ^ 0.75 = 0.075 x 27^0.75 = 0.883 s
Avg. response acceleration co-efficient, Sa/g = 1/T = 1.13
Hence Ah = (0.16 x 1.5 x 1.13) / (2x3) = 0.05
Base shear, Vb = Ah x W = 0.05 x 29687.26 = 1490.43 kN
The design of the berth is carried out by using the results obtained from equivalent static
analysis in the Staad. Pro model as in Fig.4
Figure 4 Design using linear static analysis
7. NON-LINEAR STATIC ANALYSIS
Pushover analysis is a nonlinear analysis and gives a realistic behavior of the structure. The
model of the berth is done using the SAP 2000 software. The material properties and load are
defined. The static pushover case is also defined and the analysis is run to establish the
pushover, hinge and modal properties and also the performance levels as per ATC 40 and
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FEMA 356. The mode shape and modal properties are obtained as in Fig.5 and it is noted that
the time period obtained is T = 1.19s whereas the base shear is Vb = 12780.92 kN.
Figure 5 Mode shape and Modal Properties
The pushover curve is obtained by using the Push load case, it is a graph plotted for Base
reaction and displacement, and is developed as in Fig.6 along with the displacement and base
shear values for each push case (incremental load).
Figure 6 Pushover curve and results
Similarly using the FEMA 356 co-efficient method, the displacement and base shear are
plotted and in this case the target base shear, displacement and time period are obtained as in
Fig.7.
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Figure 7 Pushover curve and results using ATC 356 method
The pushover curve is then converted to capacity diagram. The demand spectra and capacity
curve are plotted together to obtain the performance point. The performance point gives us the
point at which the capacity of the structure satisfies the demand created on it. This is illustrated
in Fig.8 where the pink lines represent the constant period, blue is the single demand spectrum,
red is the demand spectra and green is the capacity curve. The effective time period, base shear
and displacement of the structure are also obtained. The capacity and demand parameters are
also tabulated in Fig.8.
Figure 8 Plotting capacity curve and demand curve and ATC 40 Tabulated results
The results obtained from Fig.8 gives teff = 0.85s in step 2. The hinge points formed are also
analyzed step by step and it can be determined whether the model falls under the acceptance
criteria as per the ATC 40 guidelines. The step 2 of hinge formations is illustrated in Fig.9. The
figure illustrates that the structure falls under immediate occupancy criteria which proves that
the structure modelled in SAP 2000 is hence safe.
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Figure 9 Hinge formation at step 2 push
8. RESULTS AND CONCLUSION
• Using the conventional method as in IS 1893 the cargo berth is designed and the following
parameters are arrived at from the linear static method
T = 0.79s, Vb = 14616.13 kN and Ah = 0.05
• The pushover analysis is effectively carried out and the mode shapes are derived. The time
period and base shear are thus obtained as:
T = 1.19s, Vb = 12780.92 kN
• The results obtained in terms of pushover demand, capacity spectrum give the performance
factors of the structure, hence enabling to carry out a performance based design.
• The effective values obtained from the performance based analysis are:
Teff = 0.85s, Vbeff = 14873.84 kN, Deff = 0.051
• The results of the linear and nonlinear static analysis are compared in terms of time period and
base shear in the form of bar charts as in Fig.10
Figure 10 Comparison of time period and base shear results from both the methods
• Based on the comparative results, the conventional design practice followed can be optimized
by using the pushover results to bring efficiency in terms of economy. The utility ratio is
illustrated as in Fig.11 for the design followed by linear static analysis and Fig.12 for non-linear
static analysis. It proves that the design followed using pushover analysis gives a better utility
ratio of 0.991 whereas the conventional design of a utility ratio of 0.777. This proves that the
design procedure carried out using Pushover method is more effective as it studies the real time
behavior of the structure and brings efficiency in terms of cost too.
Time
period
Linear static
analysis0.8835
Non-Linear
static analysis1.19637
00.5
11.5
Ax
is T
itle
Time period (s)
Vbx
Linear static
analysis1490.43
Non-Linear
static analysis12780.92
05000
1000015000
Ax
is T
itle
Base shear Vb (kN)
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Figure 11 Design using linear static analysis
Figure 12 Design using Non-linear static analysis
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