International Journal of Technical Innovation in Modern … · 2019. 3. 19. · Impact Factor: 5.22...

International Journal of Technical Innovation in Modern

Engineering & Science (IJTIMES) Impact Factor: 5.22 (SJIF-2017), e-ISSN: 2455-2585

Volume 5, Issue 03, March-2019

IJTIMES-2019@All rights reserved 182

AN EVALUATION OF RESPONSE REDUCTION FACTOR (R) OF CABLE

STAYED SUSPENSION HYBRID BRIDGE

1 Krutarth Talati, 2 V. R. Panchal, 3 A. N. Parikh

1 Post Graduate Student (Structural Engineering), Department.of Civil.Engineering, .Chandubhai S. Patel Institute of

Technology, Charotar University of Science.and Technology, Changa, Gujarat, India.

2 Professor and Head, Department of Civil Engineering, .Chandubhai S. Patel Institute of Technology, Charotar

University of .Science.and Technology, Changa, Gujarat, India.

3 Director, Multi Media Consultant Pvt. Ltd. Ahmadabad

ABSTRACT:The requirement of large span bridges increases with the development in every nation. Cable stayed

suspension hybrid bridge could be acceptable choice as long span bridges. The reason of this study is to find

Response Reduction Factor (R) of this type of bridge with different type of pylon shapes using midas Civil software.

Nonlinear Static Analysis is carried out to determine this factor. The ‘R’ factor is applied to base shear of the bridge

for economical bridge design. There is no specific value of ‘R’ Factor mention in IRC codes. From the study, it is

observed that values of ‘R’ for seismic Zone : II are 6.3884, 4.6880, 7.7322 for H type, Diamond type, A type pylon

shape, respectively.

Index Terms : Cable Stayed Suspension Hybrid Bridge; Response Reduction Factor (R); Nonlinear Static Analysis

(pushover analysis)

I. INTRODUCTION

CABLE STAYED SUSPENSION HYBRID BRIDGE The necessity of large span bridge is rapidly increasing in every nation. To construct an extremely large span bridge,

uses of higher strength materials along with new structural techniques are mandatory. Among different options for large

span, bridges Cable stayed suspension hybrid bridge (CSSHB) is an efficient system. This bridge is merger of

Suspension bridge and Cable stayed bridge. In Cable stayed bridge, deck weight is carried by cable and transfers load to

pylon. In Suspension bridge, deck weight is carried by suspender (Hangers) and it transfers load through main

suspension cable to pylon. This system is adopting in the rehabilitation of existing bridges. Brooklyn bridge in New

York is one of the example of it. Figure 1 shows the diagram of CSSHB.

Figure1. Schematic Diagram of CSSHB

ADVANTAGES OF CSSHB

The cable stayed portion is reduced in CSSHB as compared to similar span cable stayed bridge. This results into

reduced in height of pylon, axial forces in cable and length of stayed cables.

The some amount of suspension portion (near pylon) is replaced by cable-stayed portion and main suspension can be

shortened in CSSHB as compared to a same length suspension bridge.

Shortening of suspension part in main span results in decrease in construction cost of main cable and large anchors.

RESPONSE REDUCTION FACTOR (R)

During an earthquake event, forces are generated along all axis resulting in axial forces, moments, shear forces in the

structure. For the cost of the structure to be economically viable, the structure needs to designed for forces less than the

actual forces generated in an extreme event but still ensuring safety through a combination of strength, ductility and

redundancy. Applied Technology Council - 19 [1] suggests that value R factor should be a product of Ductility factor

(Rµ), Over Strength factor (RS), Draft Redundancy factor (RR). In equation form it is given by:

R = R µ x R S x R R

International Journal of Technical Innovation in Modern Engineering & Science (IJTIMES)

Volume 5, Issue 03, March-2019, e-ISSN: 2455-2585, Impact Factor: 5.22 (SJIF-2017)


II. LITERATURE SURVEY

Zhang and Sun [2] carried out three-dimensional nonlinear aerodynamic solidity investigation of Cable supported

suspension hybrid bridge with 1400 m center span. They also carried out parametric study to find the influences of

various design parameters on the aerodynamic secureness of the CSSHB.

Qian and Astsneh [3] carried out nonlinear static investigation of new self anchored suspension bay bridge. Height of the

tower considered was 156 m.

Savaliya et al. [4] studied the nonlinear static investigation and modal time history investigation of CSSHB in SAP 2000.

The frequencies of bridge for various mode shapes were also calculated.

Savaliya et al. [5] presented the study of outcomes of lateral configuration on static and dynamic analysis in CSSHB.

They used different type of pylon shapes and calculated time period of bridge and compared with same span Suspension

bridge and Cable stayed bridge.

Frere [6] studied pushover seismic analysis of bridge structure. A plastic hinge model was developed to represent the

nonlinear behavior of structure and got capacity curve of bridge piers.

Mondal et al. [7] represented performance base analysis of Response Reduction Factor of Reinforcement Concrete

Frame. They concluded that IS recommends more value than actual value of ‘R’.

III. VALIDATION

Validation of work is done with the paper titled ‘Static and Dynamic analysis of Cable-stayed suspension hybrid bridge

and Validation’ [Savaliya et al.] [4]. Here, study is for 1400 m main center span and 319 m side span. Height of pylon is

259 m. Span of suspension part is 612 m in center of main span.

Pylon Column size : 6 m x 5 m

Pylon Transverse beam size : 3.17 m x 3.14 m

Deck : Box Girder

Figure 2. Geometry of CSSHB [4]

Figure 3. Geometry of Deck [4]

Table 1. C/S area and properties of CSSHB [4]

Members E (MPa) A (m2) M (kg/m)

Girder 2.1 x 105 1.761 26340

Tower Column 3.3 x 104 30 78000

Tower T. beam 3.3 x 104 10 26000

Main Cable CS 2.0 x 105 .0.3167 .2660.30

Main Cable SS 2.0 x 105 .0.3547 .2979

Cables(Hanger) 2.0 x 105 .0.0064 .50.20

Cables(Stayed) 2.0 x 105 0.008 to 0.015 Vary

where, E - Young’s modulus; A – Area of section; M - Mass per meter length

Table 2. Load Values [4]

Type of the loading Amount of load (kN/m) Component Assigned

DL 97.98 Deck only

SIDL 50.00 Deck only

LL 34.64 Deck only




To find frequencies and time period, Eigen value (Ritz vector) analysis is carried out and static & dynamic analysis is

executed to determine response of structure. Lateral and vertical mode shapes match well with the paper considered in

the study for validation. Figures 2 and 3 show the geometry of bridge and geometry of deck, respectively. The properties

and cross section area are shown in Table 1 [4] and load values are shown in Table 2 [4].

The comparison of time period between considered paper and midas Civil is shown in Table 3.

Table 3. Comparison of Time period

Mode shape T (sec) Paper T (sec) Midas Error

Lateral 14.51 14.39 0.82%

Vertical 5.38 5.43 0.92%

Figure 4. Geometry of CSSHB in midas Civil

Figure 5. Lateral mode shape T = 14.39 sec

Figure 6. Vertical mode shape T = 5.43 sec

Figure 4 show the model of CSSHB in midas Civil. Figures 5 and 6 show mode shapes in lateral and vertical direction,

respectively.




IV. RESULT AND ANALYSIS

To find response reduction factor of any structure, response of structure during earthquake needs to be found out. To find

response of structure, nonlinear static analysis (pushover analysis) should be carried out.

STEPS OF PUSHOVER ANALYSIS

Design section as per IRC 112 – 2011 [8]

Define load pattern

Define plastic hinge location and properties

PUSHOVER ANALYSIS OF STRUCTURE

H-TYPE PYLON SHAPE

(a) (b) (c)

Figure 7. (a) Geometry of pylon (b) Expected location of plastic hinge (c) Pylon model in midas Civil

(a) Pushover Curve Zone : II (b) Pushover Curve Zone : III

(c).Pushover Curve Zone : IV (d) Pushover Curve Zone : V

Figure 8. Pushover curve (a) Zone : II (b) Zone : III (c) Zone : IV (d) Zone : V




CALCULATION FOR ‘R’ FOR ZONE II

Weight of Structure = 439800 kN

Zone II

Zone factor (Z) = 0.1 , Importance factor (I) = 1.5 , Response reduction factor (R) = 5

Sa/g = 2.5

Ah = 0.0375 (as per IS 1893-2016) [9]

Base shear (as per IS 1893-2016) [9] = 0.0375 x 439800 = 16492.5 kN

Base shear from pushover curve = 31708.7 kN

Rs = 31708.7 / 16492.5 = 1.9226

µ = 2.45798 / 0.52521 ∆m = 2.45798 m (from pushover curve)

= 4.6799 ∆y = 0.52521 m (from pushover curve)

Rµ = µ = 4.6799 (Frequency is less than 1 Hz)

RR = 0.71

R = 1.9226 x 4.6799 x 0.71 = 6.3884

Values of ‘R’ of different zones for H type pylon shape are shown in Table 4.

Table 4. Values of ‘R’ for different Zones

ZONE RS Rµ RR R

II 1.9226 4.6799 0.71 6.3884

III 1.4008 4.0689 0.71 4.0469

IV 1.0737 3.6576 0.71 2.7883

V 1.0428 2.9211 0.71 2.1627

DIAMOND TYPE PYLON SHAPE

(a) (b) (c)

Figure 9. (a) Geometry of pylon (b) Expected location of plastic hinge (c) Pylon modal in midas Civil





(c) Pushover Curve Zone : IV (d) Pushover Curve Zone : V


Values of ‘R’ of different zones for Diamond type pylon shape are shown in Table 5.


ZONE RS Rµ RR R

II 1.3452 4.9084 0.71 4.6880

III 1.0229 4.2537 0.71 3.0893

IV 1.0577 3.0831 0.71 2.3153

V 1.0182 2.4166 0.71 1.7470

A TYPE PYLON SHAPE

(a) (b) (c)

Figure 11. (a) Geometry of pylon (b) Expected location of plastic hinge (c) Pylon modal in midas Civil





(c) Pushover Curve Zone : IV (d) Pushover Curve Zone : V


Values of ‘R’ of different zones for A type pylon shape are shown in Table 6.


ZONE RS Rµ RR R

II 3.8726 2.8122 0.71 7.7322

III 3.0027 2.7781 0.71 5.9224

IV 2.2243 2.7209 0.71 4.2969

V 1.8182 2.6623 0.71 3.4368

Figures 7, 9 and 11 show the geometry of pylon, location of plastic hinge and model of pylon in midas Civil for H,

Diamond and A type pylon shapes, respectively. Figures 8, 10 and 12 show the pushover curve for different zone of H,

Diamond and A type pylon shapes, respectively.

Figure 13. Graphical represent of ‘R ’ Vs. Zones

0

1

2

3

4

5

6

7

8

9

II III IV V

Val

ues

of

'R'

Zones

H shape

Diamond shape

A shape




Figure 13 show Graphical represent of ‘R ’ Vs Zones and Summary of ‘R’ factor is shown in Table 7.

Table 7. ‘R’ for different type of pylon shapes

Type of pylon Zone : II Zone : III Zone : IV Zone : V

H shape 6.3884 4.0469 2.7883 2.1627

Diamond shape 4.6880 3.0893 2.3153 1.7470

A shape 7.7322 5.9224 4.2969 3.4368

CONCLUSIONS

In the present study, H type, Diamond type, A type pylon shape CSSHB are modeled in Midas civil. From the present

study, following conclusions may be derived:

There is no specific ‘R’ value given in IRC guidelines for cable stayed / suspension type bridges.

From different type of pylon shapes, it is observed that for higher zone (i.e. higher design spectral acceleration)

Response Reduction Factor is reduced.

For Seismic Zone - II, ‘R’ value is maximum. For H type, Diamond type, A type values of ‘R’ are 6.3884, 4.6880,

7.7322, respectively.

It is observed that using A type pylon shape results in an economical design because ‘R’ value is higher compared to

other two pylon shapes.

REFERENCES

[1] ATC 19 (1995), “Structural Response Modification Factors Report”, Applied Technology Council, Redwood City,

California, USA.

[2] Zhang, X., Sun, B. (2004), “Aerodynamic stability of cable stayed-suspension hybrid bridges”, Journal of Zhejiang

University Science, Vol. 6A, pp. 869 - 874.

[3] Astsneh, A., Qian, X. (2016), “Pushover analysis of the tower of the new self-anchored suspension bay bridge”, IAJC

- ISAM joint international conference, The university of California, Berkeley.

[4] Savaliya, G., Desai, A. and Vasanwala, S. (2015), “Static and dynamic analysis of cable-stayed suspension hybrid

bridge & validation”, International Journal of Advanced Research in Engineering and Technology, Vol. 6, pp. 91 -

98.

[5] Savaliya, G., Desai, A. and Vasanwala, S. (2015), “The effect of lateral configuration on static and dynamic

behaviour of long span cable supported bridge”, International Journal of Advanced Research in Engineering and

Technology, Vol. 6, pp. 156 - 163.

[6] Frere, B. (2012), “Pushover seismic analysis of bridge structures”, Technical University of lisbon, Portugal.

[7] Mondal, A., Ghosh, S. and Reddy, G. (2013), “Performance-based evaluation of the response reduction factor for

ductile RC frames”, Engineering structures, Vol.56, pp. 1808 – 1819.

[8] IRC 112 (2011), “Code of Practice for Concrete Road Bridges”, Bureau of Indian Standards, The Indian Road

Congress, New Delhi.

[9] I.S. 1893 (2016), “Indian Standard Criteria for Earthquake Resistant Design of Structures Part 3, General Provisions

and Buildings”, Bureau of Indian Standards, New Delhi, India.

International Journal of Technical Innovation in Modern … · 2019. 3. 19. · Impact Factor: 5.22...

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