WHAT ARE RHE TYPES OF STRUCTURES ? EXPLAIN JN DETAILS, 2020

TYPES OF STRUCTURES

Structures may be classitied in many ways, based on S1Ze, shape or geometry, support

system, type of material used and methods used in their analysis and design. When a structure

1S subjected to external torces, the elements of the structure are subjected to internal stresses

set in them. the internal stresses and the reaction components can be determined by the

application ot equations oI statics alone, the structure is said to be a staticaly determunate

structure. It however, additional equations, formulated on the basis of consistent deformations

of the elements, are required along with the equations of statics, the structure is Known as

statically ndeterminate srucure.

Depending upon supporting system, structures may be ot three types:

 i)Line strucures having one dimensional supporting system.

ii)Surface structures having the two dimensional supporting system.

(iii) Space structures having three dimensional supporting system.

In the lne structure, having one dimensional supporting system, the structure 1s large in

one dimension in comparison to the other two dimensions. In such a structure, the material

of the element remains concentrated in one line which may be either straight or curved. Flexible

cable is a typical example under this category. A surface structure, which may be either plane

or curved, is large in two dimensions and very small in the third dimension. A surtace structure

may also be composed of a number of continuously connected line structures. The common

examples of surface structures are shell structures (such as water tanks, chimneys, roofs etc.)

having rigid curved surfaces and framed or skeletal structures such as roof trusses, bridge girders

industrial shades etc. Space siructures or three dimensional structures are large in three dimensions.

The common examples of this type are multistoryed buildings, exhibition pavilions, transmission

tower, television masts etc.

Depending upon the shape and geomery, structures may be of three types:

 i)Shell structures

(ü) Framed structures or skeletal structures.

(ü Solid structures.

How the road patterns are classified ?

    ROAD PATTERNS

The various road patterns may be classified as follows

(a) Rectangular or block pattern

(b) Radial or star and block pattern

(c) Radial or star and circular pattern

(d) Radial or star and grid pattern

(e) Hexagonal pattern

(f) Minimum travel pattern

These have been shown in Fig. a, b, c, d, e & f.

CLASSIFICATION OF ROADS BASED ON ALL SEASON?

 CLASSIFICATION OF ROADS

   

Types of Roads

           The different types of roads are classified into two categories, depending on whether they can be used during different seasons of the year

  i) All-weather roads and

(ii) Fair-weather roads. All weather roads are those which are negotiable during all weather,except at major river crossings where interruption to traffic is permissible

up to a certain extend.

#Based on the type of the carriage way or the road pavement, the roads are classified as

  

i) paved roads, if they are provided with a hard pavement course which should be

atleast a water bound macadam (WBM) layer and

(ii) unmpaved roads, if they are not provided with a hard pavement course of atleast a WBM layer. Thus earth roads and gravel roads may be called unpaved roads.

#Based on the type of pavement surfacing provided; the road types are divided as:

i)surface roads, which are provided with a bituminous or cement concrete surfacing

and

(ii) unsurfaced roads which are not provided with bituminous or cement concrete surfacing. The roads provided with bituminous surfacing are also called black toped roads.

Nagpur Road Plan classified the roads in India based on location and function into following five

categories and described in section 2.4.3.

 i. National Highways (NH)

(ii) State Highways (SH)

iii) Major District Roads (MDR)

(iv) Other District Roads (ODR) and

(v)Village Roads (VR)

IMPORTANCE OF HIGHWAY DRAINAGE/Significance of Drainage?

IMPORTANCE OF HIGHWAY DRAINAGE

     Significance of Drainage

              An increase in moisture content causes decrease in strength or stability of a soil mass the variation in soil strength with moisture content also depends on the soil type and the mode of stress application. Highway drainage iS l important because of the following reasons

 (i)Excess moisture in soil suberade causes considerable lowering of its stability The pavement is likely to fail due to subgrade failure as discussed in Article 10.1.

(11) Increase in moisture cause reduction in strength of many pavement materials like stabilized soil and water bound macadam.

(1i1)) In some clayey soils variation in moisture content causes considerable variation in volume of subgrade. This sometimes contributes to pavement failure

(iv) One of the most important causes of pavement failure by the formation of waves and corugations in flexible pavements is due to poor drainage.

(v) Sustained contact of water with bituminous pavements causes failures due to

stripping of bitumen from aggregates like loosening or detachment of some of the

bituminous pavement layers and formation of pot holes.

(VI) The prime cause of failures in rigid pavements by mud pumping is due to the

presence of water in fine subgrade soil.

(vii) Excess water on shoulders and pavement edge causes considerable damage.

(viil) Excess moisture causes increase in weight and thus increase in stress and

simultaneous reduction in strength of the soil mass. This is one of the main

reasons of failure of earth slopes and embankment foundations.

(ix) In places where freezing temperatures are prevalent in winter, the presence of

water in the subgrade and a.continuous supplyof water from the ground water can

cause considerable damage to the pavement due in frost action.

(x) Erosion ot soll rom top oF unsurtaced roads and slopes of embankment, cut and

hill side is also due to surface water

Briefly explain the types of Cross Drainage structure?

Cross Drainage

       Whenever streams have to cross the roadway, facility for cross drainage 1s to beprovided. Also often the water from the side drain is taken across by these cross drain in order to divert the water away from the road, to a water course or valley The cross drainage structures commonly in use are culverts and small bridgesWhen a small stream crosses a road with a linear waterway less than about six meter, the cross drainage structure provided is called culvert: for higher values of linear waterway, the structure is called a bridge.

The common types of culverts in use are

     Slab culvert

     Box culvert

     Arch culvert

     Pipe culvert

      slab culverts RcC slab is placed over abutments made of masonry and the span isgenerally limited to 3 metre.

 Box culvert of square or rectangular shapes is mads ofRCC.

 Arch culvert is generaly built using brick or stone masonry, plain cement concrete

may also be used. 

Pipe culverts ot minimum diameter 75 cm and made of steel or prefabricated RCC is used when the discharge is low.

           Various types of bridges are in use: the choice is based on severalconsiderations including the span. RCC and steel bridges are commonly constructed these days

              On less important roads, in order to reduce the construction cost of cross drainage structures, sometimes submersible bridges or cause ways are constructed. During the floods the water will flow over the road. The total period interruption to traffic has however to be kept as low as possible, not exceeding about 15 days in a year.

what are the Requirements of Highway Drainage System?

 Requirements of Highway Drainage System

ans:The followings are the basic Requirements of Highway Drainage System

i) The surtace water from the carriageway and shoulder should effectively be drained off without allowing it to percolate to subgrade

ii) The surface water from the adjoining' land should be prevented from entering the roadway.

(iii) The side drain should have sufficient capacity and longitudinal slope to cary

away all the surface water collected.

(iv) Flow of surface water across the road and shoulders and along slopes should not cause formation of cross ruts or erosion.

(V) Seepage and other sources of under ground water should be drained off by the

subsurface drainage system.

(vi) Highest level of ground water table should be kept well below the level of

Subgrade, preferably by atleast 1.2 m.

(vii) In waterlogged areas special precautions.should be taken, especially if detrimental salts are present or if flooding is likely to occur.

How to Control of Seepage Flow//Control of Capilary Rise??

     Control of Seepage Flow

            When the general ground as well as the impervious strata below are slopping, seepage

flow is likely to exist. If the seepage zone is at depth less than 0.6 to 0.9 metre from the

Subgrade level, longitudinal pipe drain in trench filled with filter materlal and clay seal

may be constructed to intercept the seepage flow. Figure 11.7 shOws the method by

which the seepage line can be lowered to the desired depth.

 Control of Capilary Rise

             If the water reaching the subgrade due to capillary rise is likely to be detrimental, it is

possible to solve the problem by arresting the capillary rise instead of lowering the eater

table. The capillary rise may be checked either by a capillary cut-of of any one of the

following two types

(i) A layer of granular material of suitable, thickness is provided during the

construction of embankment, between the subgrade and the highest level of subsurface

water table, (See Fig. 11.8). The thickness of the granular capillary cut-off layer should

be sufficiently higher than the anticipated capillary rise within the granular layer so that

the capillary water can not rise above the cutoff layer.

(ii) Another method of providing capillary cut-off is by inserting an impermeable or a

bituminous layer in the place of granular blanket. (See Fig. 11.9).