ENGINEERING COURSEWORK

Engineering Coursework

Abstract

A numerical method apt to analyse compact cross-sections of general shape under bending,. The results of this work lead to the proposal of some practical design rules. compression and given non-linear strain distributions of general shape is presented. The method can take into account holonomic hardening or perfectly plastic constitutive models of generic shape. The proposed method is implemented in a computer program permitting the analysis of the effect of the non-linear thermal loads (owing to daily and seasonal changes in shade air temperature, solar radiation, re-radiation, etc.) on the cross-section behaviour of reinforced concrete or prestressed concrete bridge decks, roof planks and slab, reinforced either with steel or with carbon, aramid or glass fibre reinforced polymers

Abstract2

Chapter 1: Introduction4

Chapter 2: Literature Review7

The numerical algorithm7

Chapter 3: Methods14

Chapter 4:Results16

The effect of non-linear thermal actions on reinforced and prestressed cross-sections under pure bending—description of the cross-sections adopted16

The effect of non-linear thermal actions on reinforced and prestressed cross-sections under pure bending—outcome of the analyses22

Chapter 5: Conclusions31

REFERENCES32

Chapter 1: Introduction

Steel rebars and tendons usually adopted to reinforce or prestress concrete have the property of being particularly ductile. If collapse of the concrete structure occurs when the tension reinforcement is markedly yielded, the whole structure presents a ductile behaviour. When this well established statement is fulfilled, the static theorem of the limit analysis guarantees that the structure will not collapse if it can stand up to an arbitrary distribution of the internal actions that equilibrates the external loads. Moreover, given strains acting on the structure (i.e. thermal actions, differential settlement of the foundation, creep and shrinkage of concrete, etc.) do not affect its load-carrying capacity (Al-Emrani, 2006, pp.819-31).

In recent years the possibility of replacing steel with fibre (usually carbon, glass or aramid) reinforced polymers (FRP) has been increasingly investigated to improve durability of the reinforcement, especially in the marine environment and in other aggressive environments. Nevertheless, reinforcement made with FRP exhibits a brittle behaviour and therefore the previous statements do not apply. When dealing with non-linear strain distributions due to daily and seasonal changes in shade air temperature, solar radiation, re-radiation, etc. (that “depend on local climatic conditions, together with the orientation of the structure, its overall mass, finishes) it has to be pointed out that the coefficient of thermal expansion of FRP materials is quite different from those of steel and concrete (the coefficient of thermal expansion of aramid fibres is negative) (Al-Saidy, 2004, pp.163-72). This dissimilarity, together with the non-linear thermal strain distribution, can give rise to self-equilibrating stresses that have to be taken into account in the evaluation of the load-carrying capacity of the cross-section owing to the brittle behaviour of the reinforcement.

This work originates from the desire to investigate the extent of the influence gathered by non-linear thermal effects due to daily and seasonal changes in shade air temperature, solar radiation, re-radiation, etc. (given according to the codes) on the behaviour (both under service loads and at failure) of reinforced concrete and prestressed concrete compact cross-sections, reinforced with FRP, under ...