I=
Pakistan Research Repository Home
 

Title of Thesis

Effects of an External Explosion on a Concrete Structure

Author(s)

Javed Iqbal

Institute/University/Department Details
Department of Computer Engineering / University of Engineering and Technology, Taxila
Session
2008
Subject
Structural Engineering
Number of Pages
196
Keywords (Extracted from title, table of contents and abstract of thesis)
Blast, Utilize, External, Structure, Parameters, Relationships, Gauss, Effects, Elements, Explosion, Concrete , Empirical

Abstract
Analysis for the structural behavior of reactor containments under Impact/Explosive loadings is an emerging field of research.The containment is the most important structure in a nuclear power plant. It is classified as a Seismic Category 1 Structure.its protection against external aggression such as explosion, aircraft, missiles and fires is essential to keep the masses safe from the hazards of radiation.The present study has, therefore, been directed to study the effect of external explosion on a typical reinforced concrete containment structure.
The general practice is to utilize the air blast pressure values in the structural analysis and design against external explosion.The ground shock parameters are usually neglected during blast resistant analysis and design.Many empirical relations have been proposed in the past to calculate the airblast pressure. Most of them, however, only predict peak pressure values. In this thesis, not only the airblast parameters have been studied but also the ground shock parameters have been dealt with.Therefore, the thesis deals with the experimental determination of relationships of following airblast and ground shock parameters against scaled distance on a reactor containment scaled model
Airblast Time History Parameters
(a) Peak pressure (Pso)
(b) Shock wave front arrival time (Ta)
(c) Rising time (Tr)
(d) Decreasing time (Td )
(e) Duration of the positive pressure phase (T )
Ground Shock Time History Parameters
(f) Peak Particle Acceleration (PPA)
(g) Arrival Time ( ta)
(h) Shock Wave Duration (td )
(i) Time lag between ground shock and air blast pressure arrival at structures (Tlag)
The results have been compared with that of previous researchers and CONWEP.The variation of results is due to curved surface of containment model.
In the second part of the study, full scale typical reactor containment has been modeled against external blast loads varying from 30 t to 160 t of Trinitrotoluene (TNT) at a detonation distance of 50-200 m using the above mentioned relationships. . . It is concluded that all the failure points lie either within the lowest 10m region or at top of the shell. It is observed that an increase of 5-20 MPa occurs with the simultaneous application of air blast and shock wave on reinforced concrete containment as compared to that of airblast only. It shows that an accurate analysis of structural response and damage of structures to a nearby external explosion requires application of ground shock and air blast pressure time history parameters at the same time.
A comparative study has also been carried out to calculate the critical distance for the Various external blast charges. The distances at which 90% of the shell elements have failed may be termed as critical distances. In the present study, the critical distances vary from 110 to 200 m for above blast charges. . The 70% of the shell elements are cracked on both faces and may be described as doubly cracked gauss points. These occur at the locations which have been crushed in the plastic range.

Download Full Thesis
1,642 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 CONTENTS

 

vii
23 KB
2

1

INTRODUCTION

1.1 General
1.2 Classification of Blast loads on structures
1.3 Blast Basics
1.4 Explosion Scenarios and Designer Options
1.5 Structural Response against Blast
1.6 Review of Previous Research Works regarding effects of Impulsive Loading on Concrete Structures
1.7 Salient Findings of Previous Researchers
1.8 Problem Statement
1.9 Objectives and Scope

1
78 KB
3 2 FUNDAMENTALS OF BLAST LOADING

2.1 Introduction
2.2 Pressure Time History
2.3 Effect of angle of incidence on Reflected pressure
2.4 Path of Triple Point
2.5 Impulse of the blast wave
2.6 Factors affecting blast loading
2.7 Calculation of blast loads
2.8 Calculation of Blast effects
2.9 Effects of blast loading
2.10 Extent of protection
2.11 Research in Reactor Containment Analysis and Design Against External Explosions

19
652 KB
4 3 MODELLING OF EXTERNAL EXPLOSION EFFECTS ON ABOVE GROUND STRUCTURESE

3.1 Prediction of blast load parameters
3.2 Features of overpressure phase
3.3 Features of Nuclear weapons
3.4 Characteristics of Conventional high explosives
3.5 Unconfined vapour cloud explosions
3.6 Airflow and reflection process
3.7 Calculation of Reflected Overpressure
3.8 External impulsive loading on Superstructures
3.9 Dynamic Response of Blast Loaded Structures
3.10 Damage Mechanism at High Strain rate
3.11 Failure modes associated with blast loading
3.12 Blast wave structure interaction
3.13 Blast Resistant Design Manuals
3.14 Computer Programs for Blast and Shock effects
3.15 Scope and Review of Computer Programs

39
897 KB
5

4

EXPERIMENTAL EVALUATION OF IMPULSIVE LOADING ON CONCRETE STRUCTURE

4.1 Introduction
4.2 Effects of structural configuration
4.3 Defining the threat
4.4 Scaling effects
4.5 Scope of Impulsive Loads in ACI Standard 359
4.6 Experimental Setup
4.7 Overpressure in the free air from surface explosions
4.8 Relationship between peak airpressure and scaled distance
4.9 The shock wave front arrival time Ta
4.10 The duration of the positive pressure phase of the shock wave
4.11 Shock wave reflection from the concrete structure
4.12 Ground shock wave from surface explosions
4.13 CONWEP introduction
4.14 CONWEP Assumptions/References for Ground Shock
4.15 Demonstration of CONWEP 94
4.16 Peak particle acceleration (PPA)
4.17 Arrival time ta
4.18 Shock wave duration td
4.19 Time lag between Ground Shock and Airblast pressure arrival at structures
4.20 Summary

77
284 KB
6

5

EVALUATION OF CONTAINMENT STRUCTURE AGAINST EXTERNAL EXPLOSION

5.1 Introduction 101
5.2 SAP 2000 Review
5.3 Material properties of concrete and steel
5.4 Soil Structure Interaction
5.5 Model description
5.6 Forces due to vertical tendons
5.7 Forces due to hoop tendons
5.8 Forces due to dome tendons
5.9 Forces due to temperature gradient
5.10 Numerical results
5.11 Critical distance for different amount of surface blast charges
5.12 Simultaneous application of blast overpressure and shock wave
5.13 Summary

101
1,542 KB
7

6

CONCLUSIONS AND RECOMMENDATIONS

6.1 Conclusions
6.2 Recommendations

129
25 KB
8

7

BIBLIOGRAPHY AND ANNEXURE

 

134
1,434 KB