Search

Bridge Design Practice in North America – An Overview

By
Isidro P. Buquiron

Introduction
The primary objective of code specifications in bridge design is public safety. Thus, in the United States, the American Association of State Highway Officials (AASHO) was formed in 1914 which later on issued the first edition of the Standard Specifications for Highway Bridges and Incidental Structures in 1931 [1]. The concept of safety provided in this document is to guarantee that all structural element in the system in part and as a whole must have minimum resistance that will exceed the load and demand applied to the structure during its specified years of service. In Canada, specifically in Ontario, the American Association of State Highway and Transportation Officials (AASHTO) specification was widely used, however unofficially before the first edition of the Ontario Highway Bridge Design Code (OHBDC) was issued in 1978 [2].

Continue Reading »

Lateral Torsional Buckling of Long Span Suspension Bridge: Geometrically Nonlinear Analysis Under Wind Load

By
D.Ishihara, H.Yamada, H.Katsuchi, and E.Sasaki
Yokohama National University

Abstract
There are plans of constructing bridges longer span like Messina strait bridge. This trend causes the necessity of discussing on the problems of instability analysis such as lateral-torsional buckling. However, lateral torsional buckling analysis of long span bridge is not sufficiently taken yet. For that reason, we apply the Abaqus/Standard to solve the high nonlinear problem. The analysis object is Akashi-kaikyo Bridge which is the longest bridge in the world. This paper presents how to analyze the lateral-torsional buckling of long span bridge applying wind load.

Keywords
Lateral Torsional Buckling, Suspension Bridge, Aerodynamics

Introduction
By now, a lot of long span suspension bridges have built and their lengths keep growing. As a result, their girder stiffness is relatively reduced and their strengths for wind force are also decreasing. Therefore, numerous futter analysis and experiments were executed. On the other hand, it is as well as important to investigate the lateral torsional buckling strengths of suspension bridges, but the investigations have never been made for decades. Certainly, we just use Hirai-Okauchi formulation that was proposed around 60’s to confirm the stability against the problem. It contains a theoretical equation and ideal boundary conditions so the application of the formulation is limited. Therefore, the need of modern examination of lateral torsional buckling of suspension bridge is increasing. A long span suspension bridge shows quite nonlinear behavior and shows non linearity when its initial condition and wind load are applied. Therefore it needs some techniques. We present the way of modeling bridges using the structural elements and making initial conditions under gravity. After this we present how to analyze the lateral-torsional buckling of long span bridge applying wind load. The wind load is calculated by the static coefficient of wind force. Finally, the result is showed and the conclusion is presented.
Continue Reading »

What is stress corrosion of prestressing steel?

Stress corrosion is the crystalline cracking of metals under tensile stresses in the presence of corrosive agents. The conditions for stress corrosion to occur are that the steel is subjected to tensile stresses arising from external loading or internally induced stress (e.g. prestressing).

Continue Reading »

In prestressing work, if more than one wire or strand is included in the same duct, why should all wires/strands be stressed at the same time?

If wires/strands are stressed individually inside the same duct, then those stressed strand/wires will bear against those unstressed ones and trap them. Therefore, the friction of the trapped wires is high and is undesirable.

Continue Reading »

What are the functions of grout inside tendon ducts?

Grout in prestressing works serves the following purposes:

(i) Protect the tendon against corrosion.

(ii) Improve the ultimate capacity of tendon.

Continue Reading »

Page 1 of 1912345Last »