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  • http://www.iaeme.com/IJCIET/index.asp 189 editor@iaeme.com

    International Journal of Civil Engineering and Technology (IJCIET)

    Volume 6, Issue 9, Sep 2015, pp. 189-204, Article ID: IJCIET_06_09_017

    Available online at

    http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=6&IType=9

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

    © IAEME Publication

    TRANSIENT ELASTO-PLASTIC RESPONSE

    OF BRIDGE PIERS SUBJECTED TO

    VEHICLE COLLISION

    Dr. Avinash S. Joshi

    M.B. Gharpure, Engineers and Contractors, Pune-411004, Maharashtra, INDIA

    Dr. Namdeo A.Hedaoo

    Associate Professor, Department of Civil Engineering,

    Govt. College of Engineering, Pune, Maharashtra, INDIA

    Dr. Laxmikant M. Gupta

    Professor, Department of Applied Mech,

    Visvesvaraya National Institute of Technology, Nagpur, Maharashtra, INDIA

    ABSTRACT

    Dynamic loading of structures often causes excursions of stresses well into

    the inelastic range. Bridge piers subjected to collision from an errant truck is

    one such loading. Owing to heavy traffic conditions coupled with lesser space,

    authorities are unable to provide enough setbacks around the piers, thus

    subjecting them to the hazard of a vehicle collision. The present study

    investigates the dynamic nonlinear response of bridge pier subjected to a

    collision. A Finite Element Analysis is carried out using a developed code in

    MATLAB. Dynamic nonlinearity in the material, i.e. concrete is studied. An

    elasto-plastic response of the pier is obtained by varying the pier geometry,

    approach velocity of the vehicle and the grade of concrete in pier. The results

    reveal several quantities. Using these results an attempt is made to quantify

    the likely damage to the pier post collision. The study is intended to investigate

    the effect of change in grade of concrete, effect of change in speed and mass of

    the colliding vehicle considering material nonlinearity.

    Keywords: collision, Drucker-Prager yield criterion, plasticity, bridge piers

    Cite this Article: Dr. Avinash S. Joshi, Dr. Namdeo A.Hedaoo and Dr.

    Laxmikant M. Gupta. Transient Elasto-Plastic Response of Bridge Piers

    Subjected To Vehicle Collision. International Journal of Civil Engineering

    and Technology, 6(9), 2015, pp. 189-204.

    http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=6&IType=9

  • Dr. Avinash S. Joshi, Dr. Namdeo A.Hedaoo and Dr. Laxmikant M. Gupta

    http://www.iaeme.com/IJCIET/index.asp 190 editor@iaeme.com

    1. INTRODUCTION

    Heavy trucks have become important in local and national freight transport with the

    rapid improvement of road networks and highways, especially in developing

    countries. The vehicle capacities have also increased. Thus the function and the safety

    of conventional transport are subjected to a risk of an errant vehicle colliding with a

    bridge structure, especially bridge piers. Although heavy goods vehicle (HGV)

    collision with bridge piers is a relatively rare type of loading it could have severe

    consequences such as loss of life, repair costs and enormous losses due to disruption

    of traffic. The forces involved are of enormous magnitude. The problem has worsened

    with traffic density increasing and severe space crunch in major cities. The minimum

    offset distances are very often encroached, increasing the risk of a collision. This

    paper addresses the effects of a dynamic force generated due to a vehicle (truck)

    collision on a bridge pier. The force-time history is one of the inputs to the program.

    Several geometries of piers with different grades of concrete are analyzed using finite

    element analysis capable of handling material nonlinearity that may be introduced in

    the pier due to a collision. This is to identify the effect on the response of the pier due

    to shape and grade of concrete. An idealized collision scene is shown in Fig.1

    2. DIMENTIONAL DETAILS OF PIERS

    The types of piers selected are as given in Table 1. Broadly three types of piers were

    selected viz., wall type, solid circular and hollow circular piers. The sizes selected are

    in accordance with the present specifications and the sizes obtained as a result of

    customary design of bridges so as to represent a significant number of bridge support

    systems.

    Figure 1 Simplified Sketch of a Collision Scene

    Table 1 Dimensional details of Pier

    Sr.No. Referencing Description Dimensions in (m) * (Fig.2)

    1 W1 Wall pier - 1 1.00 x 5.00 x 7.50 (ht.)

    2 W2 Wall pier - 2 1.50 x 5.00 x 7.50 (ht.)

    3 SC1 Solid circular pier - 1 1.50ϕ x 7.50 (ht.)

    4 SC2 Solid circular pier - 2 2.00ϕ x 7.50 (ht.)

    5 HC1 Hollow circular pier - 1 2.00ϕouter (1.00 ϕinner) x 7.50 (ht.)

    6 HC2

    Hollow circular pier - 2 2.50ϕouter (1.50 ϕinner) x 7.50 (ht.)

    Tapering to 2.00ϕouter (1.00 ϕinner)

    at top

    Sketches of piers are shown in Fig.2 along with the axis orientation. The collision

    force is considered to act in the ‘x’ direction i.e. the traffic direction. Bridge piers

    have caisson or pile foundations. These are generally buried and hence offer a great

  • Transient Elasto-Plastic Response of Bridge Piers Subjected To Vehicle Collision

    http://www.iaeme.com/IJCIET/index.asp 191 editor@iaeme.com

    deal of fixity to the pier. The superstructure and its inertia effect are considered in the

    dynamic analysis and are suitably considered in the algorithm. The partial fixity

    offered by the resistance of bearings is accommodated by applying lateral spring

    elements capable of resisting displacement at the top, limited to the frictional

    resistance offered by bearings. Wall piers have considerable length (5 m and 6 m).

    The impact force is applied eccentrically. For the Finite element analysis a 3D-8

    Noded, isoparametric brick element is employed. This is used for both, the wall piers

    as well as circular pier. Hollow piers generally have thick walls, (0.5 meters in this

    case), and hence the use of a thin shell element is not found to be suitable. Fig.3 and 4

    show the discretization of the pier. The aspect ratio of each element is nearly equal to

    one. Three grades of concrete are considered for each pier i.e. Grade 40, 50 and 60

    MPa. The intention in varying the grade of concrete is to quantify the effect on the

    response of piers (Details as per Table 1). An idealized stress-strain curve for

    concrete is adopted and identical behavior is assumed in tension and compression.

    3. FORCE-TIME HISTORIES AND VEHICLE

    CHARACTERISTICS

    This study considers two types of Force-time histories. They are briefly described

    here along with some notable points. Commercial truck classification is determined

    based on the vehicle's gross weight rating (GVWR). Force-time histories of class 6

    and class 8 are considered from the above mentioned rating.

    1.5 m

    7 .5

    0 m

    6.0 m

    6.0 m PLAN

    PIER - W2

    Y

    Z

    Z

    X

    1.0m

    5.0 m

    5.0 m

    7 .5

    0 m

    SIDE ELEVATION

    PIER - W1

    7 .5

    0 m

    1.5Ø m

    Y

    X

    X

    Z

    1.5m

    PIER - SC 1

    2.0m

    2.0 Øm

    7 .5

    0 m

    PIER - SC 2 PIER - HC 2PIER - HC 1

    Ø 1.0m

    Ø 1.5m Ø 2.0m

    Ø 2.5m

    1.0 m

    2.0 m

    1.5 m

    2.5 m

    Ø 1.0m

    1.0 Øm

    Ø 2.0m

    7 .5

    0 m

    2.0 Øm

    ELEVATION

    PLAN

    Figure 2 Orientation and Dimensional Details of Piers

    http://en.wikipedia.org/wiki/Gross_vehicle_weight_rating

  • Dr. Avinash S. Joshi, Dr. Namdeo A.Hedaoo and Dr. Laxmikant M. Gupta

    http://www.iaeme.com/IJCIET/index.asp 192 editor@iaeme.com

    Figure 3 Discretization of Wall Type Pier Figure 4 Discretization of Circular Pier

    3.1 Type-1

    Force-time history for a Medium Truck (MT) with Gross Vehicle Weight (GVW) as

    11900 kgs (Cabin Load = 4590 kgs) and having wheel base 3600 x 4200mm. The

    force-time history was obtained with simulation techniques using LS-DYNA. The

    deceleration curve is obtained for a full frontal impact of 48 kph (kilometers per hour)

    on a rigid barrier. As crash tests are carried on rigid barriers, the dynamic force

    generated is maximum taking into consideration the plastic deformation of the

    vehicle, while neglecting the flexibility of the barrier. Although flexibility of the

    barrier matters, several studies note its significance to be less in collision analysis

    [1,2].

    0 20 40 60 80 100 120

    -50

    -40

    -30

    -20

    -10

    0

    10

    20

    D EC

    EL ER

    A TI

    O N

    (G )

    TIME IN MILISECONDS

    DECELERATION

    FULL FRONTAL CRASH TEST RESULT FOR MEDIUM TRUCK

    WITH RIGID BARRIER

    G = a/g, therefore a=G*g

    g=9.81m/sec^2

    Figure 5 Deceleration Curve (MT)

    0 20 40 60 80 100 120

    -4

    -2

    0

    2

    4

    6

    8

    10

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