SEISMIC ANALYSIS AND DESIGN OF CARGO BERTH€¦ · Seismic Analysis and Design of Cargo Berth 413...

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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

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ISSN Print: 0976-6308 and ISSN Online: 0976-6316

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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.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=6

Ramesh Kannan


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


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

Ramesh Kannan


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.



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

Ramesh Kannan


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



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

Ramesh Kannan


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.



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.

Ramesh Kannan


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)



Figure 11 Design using linear static analysis

Figure 12 Design using Non-linear static analysis

REFERENCES

[1] Carl.A, “Port Designer's Handbook: Recommendations and Guidelines,” Thomas Telford

Publications, London, 2006

[2] John Gaythwaite, “Design of Marine Facilities for the Berthing, Mooring, and Repair of

Vessels,” ASCE Publications, 2004

[3] T.K.Datta, “Seismic Analysis of Structures,” John Wiley & sons, Singapore, 2010.

[4] Farzad Naeim, “The seismic design handbook,” Ch.15, John A. Martin & Associates, Los

Angeles, March 2001.

[5] Syed Ahamed. Performance Based Seismic Analysis of an Unsymmetrical Building Using

Pushover Analysis. International Journal of Engineering Research-Online, 2013 Vol.1,

pp.100-110.

[6] Frank J, Albert P, Richard.W. Recent Trends in the Analysis and Design of Offshore

Platforms in Seismic Regions. Offshore Technology conference, Texas, 2013, Vol.4,

pp.2805-2815.

[7] Sofyan. Y. Ahmed. Seismic Evaluation of Reinforced Concrete Frames Using Pushover

Analysis. Engineering Journal, 2013, Vol.21 issue 3, pp.28.

Ramesh Kannan


[8] S. Naga Sujani, K. Phanisha, N. Mohana Rupa, Sunita Sarkar, M.Nageswari, P.Poluraju.

Determination of Performance Level of G+5 Building Using Pushover Analysis by SAP

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2, Issue 2, pp.832-837.

[9] Bilge Doran, Yalçın Yükse, Caner Çakır, Senol Korkmaz, Aytuğ Seçkin and Mustafa

Köroğlu. Non-Linear Static Analysis of Vertical/Batter Pile-Wharf Structures. International

Offshore and Polar Engineering Conference, 2012, pp.1237-1242.

[10] G. J. Rix, S. D. Werner, L. M. Ivey. Seismic Analysis of Container Ports. TCLEE, 2009,

pp. 1-12.

[11] Prince Kumar and Sandeep Nasier, An Analytic and Constructive Approach to Control

Seismic Vibrations in Buildings. International Journal of Civil Engineering and

Technology, 7(5), 2016, pp.103–110.

[12] Hema Venkata Sekhar and T. Venkata Das, Analysing The Seismic Behaviour of Set Back

Building by Using E-Tabs. International Journal of Civil Engineering and Technology,

8(1), 2017, pp. 444–451

[13] Vahdani.S, Egan.J, Pyke.R, Chin.C, Griswold.T and La Basco T. Evaluating the Seismic

Capacity of a Newly Designed Wharf at the Port of Oakland. 11th Triennial International

Conference on Ports, 2007, pp.1-9.

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