DESIGN Iv And GEOTECH Assignment

NAME: LEWEL MURITHI KIAMBATI

REG NO: E024-1229/2012

UNIT: DESIGN IV

TASK: DESIGN ASSIGNMENT

DEPARTMENT: CIVIL ENGINEERING

LECTURER: Dr (Eng. KILISWA)

Rolling loads are those loads which roll over the given structural element from one end to another .For

example

i. Single point rolling loads

ii. Uniformly distributed rolling loads e.g shorter than span and longer than span

iii. Two point loads at a fixed distance

iv. Several point load at a fixed distance

If a single point concentrated load moves from one end of a girder to another end of it, it

becomes necessary to find out the maximum value of shear force and maximum bending

moment at every section of the girder to produce an economical and safe design.

Two point loads at fixed distance y

Let us assume that instead of one single point load, there are two point loads P1and P2spaced at y

moving from left to right on the beam as shown in Figure below. We are interested to find maximum

shear force in the beam at given section C. In the present case, we assume that P2<P1.

Now there are three possibilities due to load spacing. They are: x<y, x=y and x>y.

Case 1: x<y

This case indicates that when load P2will be between A and C then load P1will

not be on the beam. In that case, maximum negative shear at section C can be

given by

and maximum positive shear at section C will be

Case 2: x=y

In this case, load P1 will be on support A and P2 will be on section C. Maximum negative shear can be

given by

And maximum positive shear

at section C will

Case 3: x>y

With reference to Figure below, maximum negative shear force can be obtained when load P2 will be on

section C. The maximum negative shear force is expressed as:

And with reference to Figure above, maximum positive shear force can be obtained when load P1 will be

on section C. The maximum positive shear force is expressed as:

Maximum moment at sections in a beam supporting two concentrated loads

Let us assume that instead of one single point load, there are two point loads P1 and P2spaced at y

moving left to right on the beam as shown in Figure below. We are interested to find maximum moment

in the beam at given section C

With reference to Figure below, moment can be obtained when load P2 will be on section C. The

moment for this case is expressed as:

Influence line for moment at section C

With reference to Figure above, moment can be obtained when load P1 will be on section C. The

moment for this case is expressed as:

From above two cases, maximum value of moment should be considered for maximum moment at

section C when two point loads are moving from left end to right end of the beam.

Example:

The beam is loaded with two loads 25 kN each spaced at 2.5 m is

traveling on the beam having span of 10 m. Find the absolute maximum

moment.

Solution:

When thea load of 25kN and center of gravity of loads are equidistant

from the center of span then absolute bending moment will occur.

Hence, place the load on the beam as shown in Figure below.

The influence line for M

shown in Figure below

= 25(2.461) + 25(1.367) = 95.7Kn.m

Positive and negative shear force diagram

REFERENCE

 R.S Khurmi

 Version 2 CE IIT, Kharagpur

NAME: LEWEL MURITHI KIAMBATI

REG NO: E024-01-1229/2012

UNIT NAME: GEOTECHNICAL ENGINEERING

LECTURER: Dr. (Eng.) MOSES KILISWA

TASK: ASSIGNMENT ONE

Question

As a graduate engineer tasked with the design of a road/embarkment, briefly describe various

techniques and materials (incorporating synthetic materials/systems) that you will apply in

different related cases. Assume that the road passes in areas with unsuitable soils (20 marks).

1. Geosynthetic Clay Liners (GCLs)

Extruded Geomembrane Geosynthetic clay liners (GCLs) include a thin layer of finely-ground

bentonite clay. When wetted, the clay swells and becomes a very effective hydraulic barrier.

GCLs are manufactured by sandwiching the bentonite within or layering it on geotextiles and/or

geomembranes, bonding the layers with needling, stitching and/or chemical adhesives. The

preferred sodium bentonite clay occurs naturally in Wyoming, North Dakota and Montana in the

U.S. GCLs are commonly used to augment or replace compacted clay layers.

2. Geomembranes

Geomembranes are relatively impermeable sheets of plastic. There are two general categories of

geomembranes:

a) Calendered Geomembranes

They are formed by working and flattening a molten viscous formulation between

counterrotating rollers. Polyvinyl chloride (PVC), chlorosulfonated polyethylene (CSPE),

chlorinated polyethylene (CPE), and, more recently, polypropylene (PP) are the most common

calendered geomembranes. Specialty ethylene interpolymer alloy (EIA) geomembranes are used

for unique applications. In most cases these engineered films are supported by a textile that

provides tensile strength and enhances tear and puncture resistance.

b) Extruded Geomembranes

These are manufactured by melting polymer resin, or chips, and forcing the molten polymer

through a die using a screwextruder. The sheet is formed either by a flat horizontal die or through

a vertically oriented circular die to form either a flat wide sheet advanced on a conveyor belt.

Common extruded geomembranes include high-density polyethylene (HDPE) and various lower

density, or very flexible, polyethylenes (VFPE). Polypropylene (PP) is a relatively new type of

extruded (as well as calendered) geomembrane. Variations in the manufacturing of

geomembranes include texturing to enhance the interface friction between the geomembrane and

adjacent soils or other geosynthetics; coextruding different polymers into a single sheet to

provide enhanced durability; and the availability of multiple thicknesses and sheet sizes.

3. Punched/Drawn GeogridSlit film fabrics

Commonly used for sediment control, i.e. silt fence, and road stabilization applications but are

poor choices for subsurface drainage and erosion control applications. Though the flat tape slit

film yarns are quite strong, they form a fabric that has relatively poor permeability.

Alternatively, fabrics made with fibrillated tape yarns have better permeability and more uniform

openings than flat tape products.

Monofilament wovens have better permeability, making them suitable for certain drainage and

erosion control applications. High strength multifilament wovens are primarily used in

reinforcement applications.

4. Geogrids

Geogrids are single or multi-layer materials usually made from extruding and stretching high-

density polyethylene or polypropylene or by weaving or knitting and coating high tenacity

polyester yarns. The resulting grid structure possesses large openings (called apertures) that

enhance interaction with the soil or aggregate. The high tensile strength and stiffness of geogrids

make them especially effective as soil and aggregate reinforcement.

5. Geofoam

Geofoam is manufactured into large blocks which are stacked to form a lightweight, thermally

insulating mass buried within a soil or pavement structure. Typical applications of geofoams

include: within soil embankments built over soft, weak soils; under roads, airfield pavements and

railway track systems subject to excessive freeze-thaw conditions; and beneath on-grade storage

tanks containing cold liquids.

6. Geocellular Confinement Systems

Geocellular confinement systems (GCS) are 3-dimensional honeycomb-like structures filled with

soil, rock or concrete. The GCS structure, often called a geocell, is made of strips of polymer

sheet or geotextile connected at staggered points so that, when the strips are pulled apart, a large

honey-comb mat is formed. The GCS provides both a physical containment of a depth of soil and

a transfer of load through the GCS.

7. Geonets.

Geonets are made of stacked, criss-crossing polymer strands that provide in-plane drainage.

Nearly all geonets are made of polyethylene. The molten polymer is extruded through slits in

counter-rotating dies, forming a matrix, or “net” of closely spaced “stacked” strands. Two layers

of strands are called “bi-planar”. Three layers are called “tri-planar”.

8. Geopipe

Another significant product which has been “adopted” as a geosynthetic is plastic pipe. The

specific polymer resins used in the manufacturing of plastic pipes are: high-density polyethylene

(HDPE), polyvinyl chloride (PVC), polypropylene (PP), polybutylene (PB), acrylonitrile

butadiene styrene (ABS), and cellulose acetate buytrate (CAB). There is a wide variety of civil

engineering applications for these products, including: highway and railway edge drains,

interceptor drains, and leachate removal systems.

9. Drainage Geocomposites.

The most common geocomposite configuration is known as a drainage geocomposite. They are

composed of a geotextile filter surrounding either a geonet (blanket drain), a thick preformed

core (panel or edge drain), or a thin preformed core (wick drain). Some applications of drainage

geocomposites are blanket drains, panel drains, edge drains and wick drains.

I. Blanket Drains: commonly used as leachate or infiltration collection and

removal layers within landfills.

II. Panel Drain Panel Drains: can be placed adjacent to structures to reduce

hydrostatic pressures.

III. Edge Drains: Edge drains are often used adjacent to pavement structures to

collect and remove lateral seepage from the road base.

10. Erosion Control Nets, Meshes, and Blankets

Temporary, degradable geosynthetics are used to prevent loss of soil from the seedbed and to

enhance the establishment of vegetation where the vegetation alone should provide sufficient site

protection once established. Erosion control netting (ECN), open weave meshes (ECM), and

erosion control blankets (ECB) are the most common temporary, degradable systems. Typically

natural fibers are used in these materials. The fibers are derived from the cultivation of various

types of straw/hay or jute, or by the processing of coconut hulls (coir) or wood shavings

(excelsior).

11. Turbidity Curtains

Turbidity curtains are reusable floating geosynthetic panels that prevent water-polluting

sediment from shore-side construction or off-shore filling and dredging operations from moving

off-site. The top edge of each curtain contains floats and a cable or chain. Weights are attached

to the lower edge of the curtain to keep it vertical in the water. Posts, piling, or anchors hold the

curtains in place.

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