Lecture06 - Design loads

Lecture06 - Design loads - Lecture # 06 Design Loads...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture # 06 Design Loads
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Introduction. The bridge engineer must first list all the possible loads on the superstructure; to wit, A) Permanent Loads: 01. Dead Loads 02. Superimposed Dead Loads 03. Pressures (earth, water, ice, etc.) B) Temporary Loads: 04. Vehicle Live Loads 05. Earthquake Forces 06. Wind Forces 07. Channel Forces 08. Longitudinal Forces 09. Centrifugal Forces 10. Impact Forces 11. Construction Loads C) Deformation and Response Loads: 12. Creep 13. Shrinkage 14. Settlement 15. Uplift 16. Thermal Forces D) Group Loading Combinations.
Background image of page 2
A Brief History of Highway Loading. The primary design parameter for highways are truck loadings . The American Association of State and Highway Transportation Officials (AASHTO), founded in 1914 as AASHO, developed the concept of a train of trucks in the 1935 that imitated the railroad industry’s standards. However, as the weight of the trucks grew, the bridges were overstressed. In 1944, AASHTO developed a new concept: hypothetical trucks , called the H (with two- axles) and the HS (with three-axles) classes of trucks. These were fictitious trucks, used only for design and they did not resemble any real truck on the road. In 1975, the federal DOT upgraded the allowable gross weight for trucks from 73,280 lb to 80,000 lb (although some states increased them to 90,000 lb). A similar standard exists for Canada (the Ontario Highway Bridge Design Code, OHBDC), or the United Kingdom, the BS5400 code. Europe has higher bridge loads, because they are designed to carry heavier loads than the US, primarily military loads.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Permanent Loads. Permanent loads are always on the bridge throughout its life. 1. Dead Loads (DL). The dead loads of a bridge are all the loads from the superstructure, such as, the wearing surface, the deck, the stay-in-place forms, parapets, sidewalks, railings, bracing, connection plates, stiffeners, signing and utilities. The table below shows some of the dead load unit weights that are used to calculate the superstructure.
Background image of page 4
2. Superimposed Dead Loads (SDL). In a typical composite superstructure, the deck is formed by an 8 inch thick slab of reinforced concrete, placed upon steel stringers or box girders. The top chord of this composite is in compression, which is ideal for concrete, and the bottom chord is in tension, which is ideal for steel. The superimposed dead loads are those loads placed on the superstructure after the deck has cured, and thus has begun to work with the primary members. These are sidewalks, railings, parapets, signing, utilities and the wearing surface. 3. Pressures. In general, earth pressures upon the back-wall of the abutment is part of the substructure. The same is true of the water pressure (and ice) upon the pier. However, part of the earth pressure can end up affecting the superstructure, and this must be checked in all designs.
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Temporary Loads. 4. Vehicle Live Loads
Background image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 09/07/2011 for the course CES 5325 taught by Professor Prieto-portar during the Spring '10 term at FIU.

Page1 / 30

Lecture06 - Design loads - Lecture # 06 Design Loads...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online