### TEMPERATURE STRESSES EFFECT IN COMPOSITE GIRDER BRIDGES LOCATED AT JAIPUR IN RAJASTHAN

#### Abstract

Composite bridges exposed to environment undergo varying temperatures due to diurnal and seasonal changes

in climatic or atmospheric conditions. Temperature distributions in a bridge structure depend upon various

environments, meteorological and a bridge parameter. The important environmental parameters inuencing the temperature

distributions in a bridge structure are intensity of solar radiation, daily range of ambient air temperature humidity, cloud covers, wind

speed, turbidity of atmosphere etc.

Addition to these parameters the temperature variation in bridges is also affected by other parameters and also which includes

geographic location of the bridge as governed by the latitude and altitude, geometrical parameters and materials properties of the bridge

cross sections.

The aim of the study is to construct and instrument composite bridge, b) to subject the structure to thermal loading, and c ) to correlate the

experimental temperature distributions. Theoretical procedure provides a rational method for predicting the thermal behavior of

composite-girder bridge structures and it can be applied when used with realistic temperature , proles, material properties, and

substructure stiffness characteristics.

Bridge structures are subject to complex thermal stresses which are varying continuously with time. The magnitude of these stresses

depends upon the temperature variation within the structure and this also depends upon the geographic location and the orientation of

the bridge, climatological conditions, geometry of cross section and thermal properties of the material and the exposed surfaces. Many

bridge designers recognize that the temperature variations can produce high stresses with little guidance is given in bridge design codes

on how these stresses can be accurately calculated. The distribution of temperature throughout the cross section of a bridge structure must

be known if the resulting stresses, reactions and deformations are to be calculated. Analysis of temperature distribution throughout the

cross section of a typical bridge structure is complex as temperature varies with time and also varies from section to section. In a concrete

bridge with constant cross-sectional properties over a long length, it is assumed that the temperature is constant over the bridge length

and varies through the depth and within the width of the cross section. Therefore, the temperature eld to be determined at any time t is

two-dimensional. In this paper, a method of analysis based on nite elements is described to determine the time-dependent temperature

variation within the cross section of a concrete bridge of arbitrary geometry and orientation for a given geographic location and

environmental conditions. The nite element formulation for the analysis of transient heat ow in a two-dimensional body is treated by

various authors.

In simply supported bridge linearly or uniform varying temperatures across the depth of bridge cross section produce no stresses but the

bridge is subjected to self equilibrating stresses due to non linear temperature gradients because of the restraint of thermal expansion that

would occur between the different bers.

In continuous bridges, stresses of continuity are developed over the supports due to restraint of induced thermal curvature which is added

to self equilibrating stresses to get the total state of thermal stresses. Non Scientic research studies have been carried out to calculate what

should be the design of thermal gradients.

The bridge designers are adopting British Code, BS 5400; 1978, IRC :6-2000 and Indian Railway Standards, IRS-1997 have also recommended

temperature gradients to be considered in the design.

The Heat Transfer analysis is used in solving the temperature eld distribution. The analysis process should have two steps. The rst step is to

solve the composite girder internal temperature eld distribution and determining boundary conditions. After calculating the

temperature eld, effect of thermal stress study is done.

A study related to thermal stresses has been carried out with 2 D and 3 D approach which shows signicant change in thermal stresses for

varying span length in a simply supported bridge.

A computer program on nite element method has been developed in ANSYS to study the thermal effects in composite girder bridges.

This study is carried out to predict the temperature distribution and thermal response of a composite girder bridge located in different

parts of country in three seasons ie winter, spring, summer respectively. The country is divided into 22 zones and it was seen that many

zones computed value of thermal gradients and the observed values of the corresponding stresses differ minutely.

The numerical implementation suggested the adequacy of classifying into seven zones and attempt has been made to put thermal design

recommendations for each zone.

To do this one city from each zone has been considered as the respective representative city to predict the thermal response of a composite

girder bridge.

A detailed parametric study has been carried out to determine the thermal gradients and induce stresses in composite bridge due to

variations in environmental, geometrical and materials parameters for one location ie Jaipur, the capital of Rajasthan which can be

repeated if necessary for the other zones.

Some aspects of study include:

a) Effect of the environmental parameters i.e. ambient air temperature, wind speed and turbidity factor.

b) Effect of bridge orientation.

c) Effect of geometrical parameters eg shapes of the cross section, variation in top concrete deck thickness, steel girder web thickness and

total depth of the cross section.

d) Effect of the material parameters like wearing coat of asphalt concrete over the top deck, percentage of steel in concrete sections,

modulus of elasticity and coefficient of thermal expansion of steel and concrete.

It has been seen that non linear thermal gradients and induced stresses in a composite girder bridge are maximum when the range of daily

maximum and minimum ambient air temperature is large, the turbidity of the atmosphere is low, the surrounding wind speed is minimum

and the top deck is covered with a thicker of asphalt concrete.

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PDF#### References

. Dwivedi , A.K. Bhargava , P. Bhandari, N.M.(2004), “ Thermal Gradients in Concrete Box Girder Bridges”, The Bridge and Structural Engineer, IABSE, New Delhi Vol 34, No 1, pp 53-72 [2]. AASHTO(1989) , “ Guide specifications for Thermal effects in Concrete Bridge Superstructure”, Washington, D.C.

. Bhandari, N.M. and Bhargava, P(2002), “ Thermal Studies in Concrete Bridges” Volume on Bridge Engineering. Some Issues of Research Interest, Department of Civil Engineering , Indian Institute of Technology, Roorkee, India pp 109-130.

. Branco, Fernando A and Mendes, Pedro A(1993), “ Thermal Actions for Concrete Bridge Design”, Journal of Structural Division, ASCE, Vol 119, No 8,pp. 2313-2331

. British Standard Institution, BS 5400-1978: Part 2: Steel, Concrete and Composite Bridges, “ Specification for Loads”, London.

. Clark, L.A.(1983), “ Concrete Bridge Design to BS 5400”, Construction Press, London, pp 36-38 and 158-170.

. Elbadry, M.M. and Ghali A (1983), “ Temperature Variations in Concrete Bridges”, Journal of Structural Division, ASCE Vol 109, No STIO, pp 2355-2374.

. Imbsen, R.A, Vendershaf, D.E, Schamber, R.A and Nutt, R.V(1985), “ Thermal Effects in Concrete Bridge Superstructure”, Report No 276, Transportation Research Board(TRB), National Cooperative Highway Research , Washington, D.C.

Priestly, M.J.N(1978), “Design of Concrete Bridges for Temperature Gradients”, ACI Journal , pp: 209-217

Flaga (2001) “Application of Composite Structures in Bridge Engineering. ” Civil And Environmental Engineering Reports, Volume 15, Issue 4, pp.57-8

. Mirambell and Agaudo,( 1990) “Temperature and Stress Distributions in Concrete Box Girder Bridges” Journal of structural Engineering Volume 116 Issue-9 September 1990

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