Thermal-stress behaviour of RCC gravity dams

Vladan Kuzmanovic,Ljubodrag Savic,Nikola Mladenovic

doi:10.5937/fmet1501030k

Abstract

Roller Compacted Concrete (RCC) is a special concrete mixture with low cement content, frequently used for concrete gravity dams. This paper deals with the 3D finite element model for unsteady phased thermal-stress analysis of RCC dams. Model calibration and verification has been done, based on the in-situ measurements of the Platanovryssi dam. The study has been done using the actual dam shape, RCC time schedule, and material properties. The results prove that the recommended 3D model enables a reliable thermal-stress prediction and transversal joint distance computation for an RCC gravity dam. Roller Compacted Concrete (RCC) is a special concrete mixture with low cement content, frequently used for concrete gravity dams. To reduce the thermal cracking, RCC dams are usually cut by transverse contraction joints into monoliths. The number and position of the joints should be determined based on the thermal-stress computations. The numerical model should consist of: (a) definition of the thermal and mechanical RCC properties, (b) computation of the temporal evolution of the thermal field, and (c) thermal-stress computation. Up to date models do not simulate accurately the long- term RCC behaviour ((1), (2)), due to simplifications. This research presents one of the first attempts to faithfully predict the RCC dams contraction joint distance, and to estimate it's influence on the thermal stress field. The developed model takes into account: the actual shape of the dam, different types of concrete, actual initial and boundary conditions, thermal and mechanical properties of RCC and construction technology, (3). Calibration and verification of the thermal model are based on the in-situ temperature measurements of the Platanovryssi dam, (4). 2. THEORETICAL BACKGROUND The change of temperature (T) of a nonhomogeneous, isotropic body in time (t), due to the hydration heat, is described by the Fourier heat conductivity equation. If the thermal conductivity is independent of space and temperature:

Highlights

Roller Compacted Concrete (RCC) is a special concrete mixture with low cement content, frequently used for concrete gravity dams
To reduce the thermal cracking, RCC dams are usually cut by transverse contraction joints into monoliths
Thermal-stress computation is performed for the 3 values of the monolith length: 16 m, 20 m, and 24 m

Summary

INTRODUCTION

Roller Compacted Concrete (RCC) is a special concrete mixture with low cement content, frequently used for concrete gravity dams. To reduce the thermal cracking, RCC dams are usually cut by transverse contraction joints into monoliths. The number and position of the joints should be determined based on the thermal-stress computations. The numerical model should consist of: (a) definition of the thermal and mechanical RCC properties, (b) computation of the temporal evolution of the thermal field, and (c) thermal-stress computation. This research presents one of the first attempts to faithfully predict the RCC dams contraction joint distance, and to estimate it’s influence on the thermal stress field. The developed model takes into account: the actual shape of the dam, different types of concrete, actual initial and boundary conditions, thermal and mechanical properties of RCC and construction technology, [3]. Calibration and verification of the thermal model are based on the in-situ temperature measurements of the Platanovryssi dam, [4]

THEORETICAL BACKGROUND

NUMERICAL MODEL

RESULTS

TRANSVERSAL JOINT DISTANCE

CONCLUSIONS