Lecture_1 - Structural Concrete Design Course Notes for...

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Unformatted text preview: Structural Concrete Design Course Notes for CIVL 232 by J S Kuang Department of Civil Engineering Hong Kong University of Science and Technology [email protected] by J.S. Kuang Chapter One _____________________________________________________________________ Design of Reinforced Concrete 1.1 Introduction 1.1.1 Reinforced concrete (RC) structures • Reinforced concrete is a strong durable building material that can be formed into many varied shapes and sizes • Reinforced concrete is a dominant structural material in engineering construction and widely used in every country. • Reinforced concrete structures vs Steel structures 1 1.1.2 Design Standards (Design codes, codes of practice) Building codes: the municipal bylaws for the design and construction of building structures. • British standard (British code) BS 8110: 1997 − Structural Use of Concrete (1985 old version) • Hong Kong regulations [issued by the Buildings Department (BD)] o Code of Practice for Structural Use of Concrete 2004 o Building (Construction) Regulations 1990 o Code for loads in Buildings (to be issued); Wind code; etc. • American code ACI 318-05 (American Concrete Institute) • European codes EN 1992 Eurocode 2 (EC-2): Design of Concrete Structures [All parts of the code will be published (scheduled for April 2006)]. • Chinese code 混凝土結構設計規範 GB 50010-2002 (Code for Design of Concrete Structures GB 50010-2002) 1.1.3 Composite Action • Concrete — tensile strength ≈ 1/10 compressive strength ⎧ takes compression mainly (strong in compression) ∴ Concrete ⎨ ⎩ does not resist any tensile force (assumption) • ⎧ takes tension mainly in flexural members (berams, slabs, etc.) Steel ⎨ takes both tension and compression (columns, etc.) ⎩ 2 a) P1 P2 c) Steel reinforcement Reinforcing steel • Why do they work together well? Composite action o Bond on the interface between the two materials o Similar coefficients of thermal expansion Steel: α = 10 × 10 −6 per C o Concrete: α = (7 ~ 12) × 10 −6 per C o ∴ When temperature charges, there is no large relative movement between steel and concrete. 1.1.4 Mechanics of reinforced concrete − plain concrete beams and R.C. beams • A plain concrete beam Compression Neutral axis Tension Stresses and neutral axis 3 o Cracks occur easily under the loads as its low tensile strength (≈ 10% of compressive strength) • A reinforced concrete beam Neutral axis Steel reinforcement (reinforcing bars) As After cracks occur, steel reinforcement will carry all the tensile forces (assume that concrete does not resist any tensile force at all). o Concrete carries compression o Steel carries tension 1.1.5 Reinforced concrete members Slabs, beams, columns, walls, etc. General load path: slabs beams columns/structural walls foundations 4 slab beam column slab beam (secondary beam) beam (main beam, girder) column 5 Reinforced concrete building elements (members) 6 ...
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