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2015

WIN

CKK

8/21/2015

DESIGN BRIDGE

I. Introduction

Bridge design is a complex engineering problem. The design process includes consideration of other important factors, such as choice of bridge system, materials, dimensions, foundations, aesthetics, and local landscape and environment. And this report presents method design for Highway Bridge.

Figure_1: Picture of a type bridge

II. Main bridges

There are main bridges as: Reinforced concrete bridges, Prestressed concrete bridges, Steel – concrete composite I – Girder bridges, Arch bridges, Suspension bridges, Timber bridges, Cable – Stayed bridges,….

Several images of bridges are show under here:

Figure_2: Reinforced concrete bridge Figure_3: Suspension bridge

Figure_4: Prestressed concrete bridge Figure_5: Arch bridge

III. Main parts of the Bridge

Main pasts of the bridge is show in Figure_2

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Figure_6: Main pasts of the Bridge

IV. Design philosophy

IV.1.1. General

Bridges shall be designed for specified limit states toachieve the objectives of constructibility, safety, and serviceability, with due regard to issues of inspectability, economy, and aesthetics.

IV.1.2. Limit States

Strength Limit States - Strength limit state shall be taken to ensure that strength and stability, both local and global, are provided to resist the specified statistically significant load combinations that a bridge is expected to experience in its design life.

Extreme Event Limit States - The extreme event limit state shall be taken to ensure the structural survival of a bridge during a major earthquake or flood, or when collided by a vessel, vehicle, or ice flow, possibly under scoured conditions.

Service Limit States - The service limit state shall be taken as restrictions on stress, deformation, and crack width under regular service conditions.

Fatigue and Fracture Limit State - The fatigue limit state shall be taken as restrictions on stress range as a result of a single design truck occurring at number of expected stress range cycles. The fracture limit state shall be taken as a set of material toughness requirements of the AASHTO Materials Specifications.

IV.1.3. Ductility (tính dẻo)

The structural system of a bridge shall be proportioned and detailed to ensure the development of significant and visible inelastic deformations at the strength and extremeevent limit states before failure.

IV.1.4. Redundancy (tính dư)

IV.1.5. Operation importance (tầm quan trọng khi sử dụng)

V. Bridge Design

V.1. Determine design creteria

Design standard, design life,…

V.2. Determine load designation

Load designation have two main types: permanent load and trensient load

Permanent load:

DD = downdrag DC = dead load of structural components and nonstructural attachments DW = dead load of wearing surfaces and utilities EH = horizontal earth pressure load EL = accumulated locked-in force effects resulting from the construction process, including the

secondary forces from post-tensioning ES = earth surcharge load

EV = vertical pressure from dead load of earth fill

Transient load:

BR = vehicular braking force CE = vehicular centrifugal force CR = creep CT = vehicular collision force CV = vessel collision force EQ = earthquake FR = friction IC = ice load IM = vehicular dynamic load allowance LL = vehicular live load LS = live load surcharge PL = pedestrian live load SE = settlement SH = shrinkage TG = temperature gradient TU = uniform temperature WA = water load and stream pressure WL = wind on live load WS = wind load on structure

V.3. Load combination

VI. Calculation and check

- Calculation interion load of structure. - Check for the strength limit state, extreme, service and fatigue.

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VII. Flowchart for Prestress Concrete Bridge

Main design steps is show in under chart: