Str & Loadsb(Lec 2)

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STRUCTURES

ANDLOADS



Beams – usually straight horizontal members

used primarily to carry vertical loads- primarily designed to resist bending

moment

simply supported beam

cantilevered beam

fixed-supported beam

continuous beam



Wide Flange

flange

flange

web



Concrete Beams – generally have rectangular

cross-section

Pre-Cast Concrete Beams – fabricated at a shop

or yard and then transported to the site

Wooden Beams – maybe sawn from a solid

piece of wood or laminated (constructed fromsolid sections woods, fastened together)



Columns – members that are generally vertical

and resist axial compressive loads

Examples of column sections

- tubes and wide flange (for metal columns)

- circular and square sections with reinforcingsteel bars (for concrete columns)

Beam Columns – occasional columns designed to resist

axial load and bending moment



Types of Structures

Structural System – combination of structural

elements and the materials from which they are

composed



Trusses

- used when the span of a structure isrequired to be large and its depth is not an

important criterion for design

- consist of slender elements, usually

arranged in a triangular fashion

- has the advantage over a beam to use less

material in supporting a given load and the long

slender rods can be arranged in various ways- economically feasible to cover spans ranging

from 9m to 122m (sometimes even longer)



Planar Trusses – composed of members that lie

in the same plane, frequently used for bridgesand roof support

Space Trusses – with members extending inthree dimensions and are suitable for derricks

and towers



Cables and Arches

Cables

– usually a flexible material that can carry

tensile loads

- unlike tension ties, the external load isnot applied along the axis of the cable, and

consequently takes a sag form



Cont…(Cables)

- commonly used to supportbridges and building roofs (for these

purposes, cable has an advantage over

beams and trusses especially for spansgreater than 46 m)

-limited only by the sag, weight and

method of anchorage



Arch

– has a reverse curvature to that of cable,

thus, achieves its strength in compression

- must be rigid in order to maintain its

shape

- frequently used in structures like dome

roofs and masonry wall openings



Frames

- often used in buildings and are composedof beams and columns that are either pin or

fixed connected

- extend in 2 or 3 dimensions

pinned

pinned

rigid

rigid



Cont..(frames)

- the loading causes bending on its

members and is generally indeterminate in

its analysis- the strength derived from the

moment interactions between the beams

and the columns



General Building Codes

- specify the requirements ofgovernmental bodies for minimum design loads

on structures and minimum standards for

construction

Design Codes

- provide detailed technical standards andare used to establish the requirements for the

actual technical design



Some Of the Important Codes Used in Practice:

General Building Codes:

Minimum Design Loads for Buildings and Other Structures

SEI/ASCE 7-05, American Society of Civil Engineers

International Building Code



Design Codes:

Building Code Requirements for Reinforced

Concrete, American Concrete Institute (ACI)Manual of Steel Construction, American Institute ofSteel Construction (AISC)

Standard Specifications for Highway Bridges,

American Association of State Highway andTransportation Officials(AASHTO)

National Design Specification for WoodConstruction, American Forest and Paper

Association (AFPA)Manual for Railway Engineering, American RailwayEngineering Association (AREA)



Dead Loads

-consist of the weights of the various

structural members and the weights of any

objects that are permanently attached to the

structure

- for a building, include the weights of

columns, beams and girders, floor slab, roofing,

walls, windows, plumbing, electrical fixtures,

and other miscellaneous attachments



Live Loads

- can vary both in magnitude andlocation like weights of objects temporary

placed on structure, moving vehicles, or

natural forces.- minimum live loads specified in

codes are determined from studying the

history of their effects on existingstructures



Minimum Design Dead Loads kN/m2

Walls

100 mm clay brick 1.87



Frame Partitions and Walls

Exterior Stud Walls with Brick veneer 2.30

Windows, glass, frame and sash 0.38Wood studs 50 x 100 mm unplastered 0.19



Cont..(Minimum Design Dead Loads: Frame Partitions/Walls)

Wood studs 50 x 100 mm plastered one side 0.57

Wood studs 50 x 100 mm plastered two sides 0.96

Floor Fill

Cinder Concrete, per mm 0.017

Lightweight Concrete, plain, per mm 0.015

Stone, concrete, per mm 0.023



Floor Fill

Cinder Concrete, per mm 0.017

Lightweight concrete, plain, per mm 0.015

Stone concrete, per mm 0.023

CeilingsAcoustical fiberboard 0.05

Plaster on tile or concrete 0.24

Suspended metal lath and gypsum plaster 0.48

Asphalt shingles 0.10

Fiberboard, 13 mm 0.04



Minimum Live Loads

Occupancy or Use kN/m2

Assembly areas and theaters Fixed Seats 2.87

Movable Seats 4.79

Dance halls and Ballrooms 4.79Garages (passenger cars only) 2.40

Office Buildings

Lobbies 4.79Offices 2.40



Storage Warehouse

Light 6.00

Heavy 11.97Residential

Dwellings (one and two family) 1.92

Hotels and Multi-Family Houses Private rooms and Corridors 1.92

Public Rooms and Corridors 4.79

Schools

Classrooms 1.92Corridors above first floor 3.83



Sample Problem 1

The floor of a light storagewarehouse is made of 150-mm thick cinder

concrete. If the floor is a slab having a

length of 3m and width of 2.4m, determinethe resultant force caused by the dead load

and that caused by the live load.

(Ans: DL = 18.4 kN; LL = 43.2 kN)



Sample Problem 2

The building wall consists of 200-mm clay brick. In theinterior, the wall is made from 50mm x 100 mm wood

studs, plastered on one side. If the wall is 3m high,

determine the load in kN per meter of length of wall

the wall exerts on the floor.

3 m

Answer : LOAD = 13.1 kN/m



Sample Problem 3

The pre-cast T-beam has the cross-sectionshown. Determine its weight per meter length if

it is made from reinforced stone concrete and

eight 20-mm cold formed steel reinforcing rods.

USE : ρsteel = 77.3 KN/m3

Ρconc = 23.6 kN/m3

200mm

200mm

500mm

375mm 1 5 0 m m

1 5 0 m m

375mm

Answer : W B = 9.16 kN/m

150mm



Sample Problem 4

The beam supports the roof made from

asphalt shingles and wood sheathing boards. If

the boards have thickness of 38 mm and a

specific weight of 7.86 kN/m3, and the roof’s

angle of slope is 30O, determine the dead load ofthe roofing – per square meter – that is

supported in the x and y directions by the

purlins.



purlin

sheathing

shingles

30O

Answer:

ρx = 0.2 kN/m2

ρy = 0.35 kN/m2



Sample Problem 5

The second floor of a light manufacturingbuilding is constructed from a 125 mm thick

stone concrete slab with an added 100 mm

cinder concrete as shown. If the suspended

ceiling of the first floor consists of metal lath

and gypsum plaster, determine the dead load for

design in kN per square meter of the floor area.



100 mm cinder fill125 mm concrete slab

ceiling

Answer: DL = 5.0 kN/m2

Str & Loadsb(Lec 2)

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