AIN SHAMS UNIVERSITY FACULTY OF ENGINEERING STRUCTURAL ENGINEERING DEPARTMENT Modeling of lightweight concrete elements using nonlinear finite element analysis Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE in CIVIL ENGINEERING (STRUCTURES) by Eng. Randa Fouad Ibrahim Fouad Hegazi Supervised by Prof. Dr. Amr Zaher Professor of Concrete Structures Ain Shams University ASS. Prof. Dr. Khaled Hilal Riad Associate Professor of Structural Engineering Ain Shams University Dr. Aiman Ezzat Mohamed Assistant Professor of Structural Engineering Modern academy Cairo – 2016 AIN SHAMS UNIVERSITY FACULTY OF ENGINEERING Modeling of lightweight concrete elements using nonlinear finite element analysis By Randa Fouad Ibrahim Fouad Hegazi B.Sc. (2011) with Honor Structural Division- Civil Engineering Department Faculty of Engineering – Ain Shams University EXAMINERS’ COMMITEE Signature Prof. Ashraf El-Zanaty Professor of Concrete Structures Dean of Faculty of Engineering Cairo University …………………… Prof. Ayman Hussein Hosny Khalil Professor of Concrete Structures Faculty of Engineering – Ain Shams University …………………… Prof. Amr Hussein Zaher Professor of Concrete Structures Faculty of Engineering – Ain Shams University …………………… Date: 21/ 9/2016 STATEMENT This thesis is submitted to Ain Shams University in partial fulfilment of the requirements for the degree of Master of Science in Civil Engineering (Structural). The work included was carried out by the author at reinforced concrete laboratory of the Faculty of Engineering, Ain Shams University and Housing and Building National Research Center. No part of this thesis has been submitted for a degree or a qualification at any other university or institution. Date: 21/9/2016 Name: Randa Fouad Ibrahim Fouad Hegazi Signature: AUTHOR Name : Randa Fouad Ibrahim Fouad Hegazi Date of birth : 4 August 1988 Place of birth : Alex, Egypt Academic Degree : B.Sc. in Structural Engineering University : Ain Shams University Date : July 2011 Grade : Very good with honor degree ACKNOWLEDGEMENT First of all, I thank GOD who guided and helped me to finish this work in the proper shape. To my family, whose patience and love enabled me to complete this work. To my parents, who taught me the value of hard work. I would like to share this moment of happiness with my parents, brother and sisters. They rendered me enormous support, encouragement and motivation during my whole life. To you my lovely sister Nashwa, the entire thesis is your words. Without you I couldn't make it. I am deeply indebted to Prof. Amr Zaher, Professor of concrete structures, faculty of engineering, Ain Shams University, for his guidance and valuable suggestions. I'm also extremely grateful to Dr. Khaled Hilal Riad, Assistant Professor of Structural Engineering, Ain Shams University, for giving me the opportunity to work with him. I would like to express my gratitude to their experienced advice, continuous support and deep encouragement through all phases of the work. Finally, I would like to thank my friends and colleagues who helped me in the completion of this work. ABSTRACT Modeling of foam balls lightweight concrete elements using nonlinear finite element analysis Researchers and industrialists' interest in lightweight concrete (LWC) to be used in structural applications is steadily increasing. It is currently believed to have a promising future. It was restricted to use as partition wall, thermal insulation and rehabilitation work in the past. In the last few decades with the understanding of the phenomenon underlying LWC, efforts have been made to use foamed concrete in structural application. The main objective of the research was to investigate the mechanical and structural properties of foam balls lightweight concrete. Foam balls lightweight concrete FBLWC is a type of concrete with cementations' paste, fines, water, coarse aggregate and foam balls. The use of admixtures such as fly ash and silica fume, the foam concrete provides more strength. Foam balls lightweight concrete is a concrete weighing substantially less than that is made using gravel or crushed stone aggregates. FBLWC is usually chosen for structural purposes, which its use will lead to a lower overall cost of structure than will be expected with normal weight concrete. The general high unit cost of lightweight structural concrete is offset by reducing dead loads and lower foundation costs. A new kind of LWC (foamed balls lightweight concrete) was developed for foam balls lightweight concrete, in which conventionally aggregate is partially replaced by polystyrene foam particles, which combined the advantages of normal density concrete, cellular concrete and high workability. Advances in the field of computer that aided engineering during the last two decades have been quite extensive and have led to considerable benefits to many engineering structures. In the building industry, the use of advanced finite element tools has not only allowed the introduction of innovative and efficient building products, but also the development of accurate design methods. The main objective of this study was to determine the mechanical properties of FBLWC. The investigation focused on studying the compressive strength, tensile splitting strength, modulus of elasticity, stress-strain relationship in (compression and tension) and tension stiffening effect. The research work included an experimental and a numerical phase. The experimental program included the testing of foam balls lightweight concrete specimens under concentric axial load in both tension and compression to obtain the actual stress strain properties of the produced FBLWC. The program consisted of twenty seven specimens of cubes, cylinders and prisms of FBLWC. Three standard cubes of dimension 150x150x150 mm and cylinders of dimension 150x300 mm were tested after 28 days to determine the compressive strength. Three cubes and five cylinders were tested after 28 days to draw the stress-strain relationship. One cylinder was tested to determine the Young's modulus. The last three cubes were tested to determine the tensile splitting strength. Each prism with different steel bar diameter was tested to obtain the tension stiffening effect behavior of FBLWC. This study showed that the use of foam balls in lightweight concrete clearly reduced the density of the concrete from 24.00 kN/m3 to 18.45 kN/m3 which represented a reduction of 23%. The average compressive strength for cube specimens was 27 MPa. And the average compressive strength for the cylinder specimens was 22.40 MPa. Also the ratio of the cylindrical compressive strength to the cubic compressive strength was about 0.81. The stress-strain curve in tension was the average of direct tension for three specimens of 12 mm, 16 mm and 18 mm steel diameter in the middle of the FBLWC prisms. The curve assumed a linear relationship up to the concrete cracking strength, fcr. The fcr was 2.03 MPa and ԑcr was 0.00012. The calculated Ec was 16917 MPa. The difference between experimental Ec and calculated Ec from direct tension test was 2.5%. After cracking, where the average strain ԑm exceeded the cracking strain ԑcr, the stress-strain curve could be represented by exponential function up to average strain. In the numerical phase, a finite element model was developed to be used for the simulation of nonlinear behavior of foam balls lightweight concrete. This finite element model was validated using previous experimental results available in literature and self-performed tests. The model would be calibrated and used to perform a parametric study on the behavior of foam balls lightweight concrete. Keywords: Foam balls lightweight concrete, mechanical properties, compression stress-strain curve, tensile stress-strain curve, tension stiffening effect, SOFISTIK software, modelling of actual behavior TABLE OF CONTENTS Chapter 1: Introduction ………..……………………………………………..…. -11.1. General ……………………………………………………………………..… -112. Finite element …………………………………………………………………. -21.3. Lightweight foamed concrete ……………………………………………...… -31.4. Scope …………………………………………………………………..……… -31.5. Objectives …………………………………………………………………..… -41.6. Organization of thesis ……...………………………………………………… -4Chapter two: Literature review…………………………..…………………...…. -62.1. Foam balls lightweight concrete …………………………………………...…-62.1.1. Introduction …………………………………………………………...…... -62.1.2. Historical background …………………..………………………………… -62.1.3. Structural lightweight foam concrete …………………………………….. -72.1.3.1. Definition ………………………………………………………………. -72.1.3.2. Concrete classification..……………………………………………........ -82.1.3.2.1. The production …………………………………………………....... -82.1.3.2.1.1. Lightweight aggregate concrete ..…………………………....… -92.1.3.2.1.2. Aerated lightweight concrete ………………………………...... -92.1.3.2.1.3. No-fines concrete …………………………………………….... -92.1.3.2.2. The utilization purpose …………………………………………… -122.1.4. Comparison of foamed concrete and plain concrete ….……………..…. -132.1.5. General behavior of concrete ……………..…………………………….... -132.1.5.1. In compression ……………………………...………………………… -132.1.5.2. In tension …………………………………………...………………… -142.1.5.3. General behavior of cracked concrete ………………………………... -142.1.6. Application of lightweight concrete …………………………………....... -162.1.7. Benefit of lightweight …………….……………………………………..… -182.1.8. Mechanical properties of structural lightweight foam concrete ………. -192.1.8.1. Stress-strain relationship ……..……………………………………… -202.1.8.1.1.1. General stress-strain curve for normal weight concrete in ECP 203-2007….. -20- i 2.1.8.1.1.2. General stress-strain curve for normal weight concrete and lightweight concrete in Euro code ………………………………………………………..…… -212.1.8.1.1.3. General stress-strain curve for normal weight concrete and lightweight concrete for the design of cross section in Euro ………………………………….. -222.1.8.1.1.4. General stress-strain curve for lightweight concrete …………….….. -242.1.8.1.1.5. General stress-strain curve for lightweight concrete foamed concrete..-252.1.8.1.2. Factors effecting stress-strain curve ……………………………….... -252.1.8.1.2.1. Setup of the test.….……………………………………………… -252.1.8.1.2.2. Effect of specimen slenderness and friction …………………….. -272.1.8.1.2.3. Effect of boundary restraint ……………………………………... -282.1.8.1.2.4. Effect of loading rate …...………………………………………. -292.1.8.1.3. Important of determining the stress-strain curves ……………….… -332.1.8.2. Modulus of elasticity ……….………………………………………….. -332.1.8.2.1. Modulus of elasticity for normal weight concrete in (ECP 203-2007) …………………………………………………………………………………….. -332.1.8.2.2. Modulus of elasticity for normal weight concrete in ACI-318M-14, 2014) ……………………………………………………………………………… -342.1.8.2.3. Modulus of elasticity for lightweight concrete in (ACI-318M-14, 2014) …………………………………………………………………………………….. -342.1.8.2.4. Modulus of elasticity for lightweight concrete in BS-8110 ………. -352.1.8.2.5. Modulus of elasticity for lightweight concrete in EN 1992-1-1 ….. -352.1.8.3. Compressive strength ……………………….………………………… -372.1.8.3.1. Compressive strength for normal weight concrete in ECP 203-2007 ………………………………………………………………………………..…… -372.1.8.3.2. Compressive strength for normal weight concrete in EN 1992-1-1…………………………………………………………………………………….. -382.1.8.3.3. Compressive strength for lightweight concrete in EN 1992-1-1 .… -382.1.8.3.4. Compressive strength for normal weight concrete in ACI-318M-14, 2014) ……………………………………………………………………………… -392.1.8.3.5. Compressive strength for lightweight concrete in (ACI-318M-14, 2014) ……………………………………………………………………………… -39ii