Draft

Chapter 2

LOADS

2.1 Introduction.

1 Themainpurposeof a structureis to transferloadfromonepoint to another:bridgedeck to

pier;slabto beam;beamto girder;girderto column;columnto foundation;foundationto soil.

2 Therecan alsobe secondaryloads such asthermal(inrestrained structures),dierential

settlement of foundations,P-Deltaeects(additionalmoment causedby theproductof the

verticalforceandthelateraldisplacement causedby lateralloadin a highrisebuilding).

3 Loadsaregenerallysubdividedinto two categories

VerticalLoadsor gravity load

1. deadload(DL)


2. live load(LL)

alsoincludedaresnow loads.

LateralLoadswhich acthorizontallyonthestructure

1. Windload(WL)


2. Earthquake load(EL)

thisalsoincludeshydrostaticandearthloads.

4 Thisdistinctionis helpfulnotonlyto computea structure'sload,butalsoto assigndierent

factorof safety to each one.

5 For a detailedcoverageof loads,referto theUniversalBuildingCode(UBC),(UBC1995).

2.2 VerticalLoads.

6 For closelyspacedidenticalloads(such as joistloads),it is customaryto treatthemas a

uniformlydistributedloadratherthanas discreteloads,Fig.2.