FIELD OF THE INVENTION
The present invention relates to a two legged trestle for low elevated structure
used in coal handling plant of thermal power plant. More particularly, the present
invention relates to an optimized and standardized two legged trestle for
supporting conveyor galleries at lower elevation in coal handling plant.
BACKGROUND OF THE INVENTION
A two legged trestle for low elevated structure is one of the components in coal
handling plant. The two legged trestle for low elevated structures support the
galleries used in transporting the material from the port to bunker or storage
yard and then to the boiler. These trestles can be of various heights and width
depending on the technical requirement.
The prior art arrangement for supporting conveyor galleries at low elevations is a
single framed structure and which per se consists of two built-up columns made
up of flat sections. It consists of a plurality of horizontal beams and front
bracings, all of them are of built up members made up of flat sections for
example, channels, angles. Since the single framed structure has built up flat
members it will have more welding length and hence more fabrication and
erection time. Because of the built-up section, the wind load acting on the
structure is higher due to its more exposed surface area which can be avoided in
pipe sections. Higher force coefficient for the flat members also increases the
wind load acting on the structure. Moreover, there is no known process for
optimization of the structure and hence the prior art structures are mostly over
designed.

OBJECT OF THE INVENTION
It is therefore an object of the present invention to propose an optimized and
standardized two legged trestle for supporting conveyor galleries at lower
elevation in coal handling plant, which supports the conveyor gallery structure at
low elevations reduces the total weight of the structure due to optimization of
structural components.
Another object of the invention is to propose an optimized and standardized two
legged trestle for supporting conveyor galleries at lower elevation in coal
handling plant, which is formed of standard pipe sections to eliminate welding
requirement of prior art built up sections.
A further object of the invention is to propose an optimized and standardized two
legged trestle for supporting conveyor galleries at lower elevation in coal
handling plant, which can withstand heavy wind load conditions.
A still further object of the invention is to propose an optimized and standardized
two legged trestle for supporting conveyor galleries at lower elevation in coal
handling plant, which prevents excessive deflection of the structure and limit the
stress up to a safe limits under severe wind load conditions.

SUMMARY OF THE INVENTION
Accordingly, there is provided an optimized and standardized two legged trestle
for supporting conveyor galleries at lower elevation in coal handling plant. The
trestle comprises of single frame with two legs.
The single frame in transverse to the conveyor direction and connected to two
legs. The frame contains a plurality of horizontal as well as inclined bracings. The
bracings between the legs provide stability against lateral deflection. The whole
structure is divided into a number of segments by horizontal bracings, depending
upon the height of the structure.
Standard pipe sections are employed in the proposed trestles. Pipe sections are
preferred to standard flat sections because of the following reasons,
i) The force coefficient of circular sections are almost 30% less when
compared to flat sections which results in huge reduction in wind load
acting on the structure.
ii) The load carrying capacity increases because of increase in moment of
inertia.
iii) Circular section may have as much as 30 to 40% less surface area than
that of an equivalent rolled shape and thus reduces the cost of
maintenance, cost of painting.

iv) There is no better section than the tubular one for torsional resistance.
v) Tubes are of special interest to architect from an aesthetics view point.
vi) The external surface of the tube does not permit the collection of moisture
and dust thus reducing the possibility of corrosion.
The present invention bridges the gap of weight optimized design from
conventional design for a standard trestle with two legs for supporting conveyor
gallery structure at low elevations.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS :
The accompanied drawings describe the invention in detail and illustrate the
features, aspects, and advantages of the present invention. Reference numerals
are used for locating the component of the system. The invention may be readily
understood and carried into practical effect based on the following description
taken in conjunction with the accompanying drawings, wherein:
Figure 1 shows the device of the invention in an isometric view of the two legged
trestle for low elevated structure.
Figure 2 shows an isometric view of a typical segment from the two legged
trestle for low elevated structure of figure 1.

Figure 3 shows the front view of the segment of figure 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE
INVENTION
Figure 1 shows the overall isometric view of the trestle with two legs for
supporting conveyor gallery structure at low elevations in accordance with a
preferred embodiment of the invention. The two legged trestle for low elevated
structure consists of a single frame formed between two legs (1,2) across the
direction of coal flow (lateral frame).
The following are the parameters considered for finalizing the technical
requirements :-
1) Top width of the structure - Centre to centre distance between two legs
(across the direction of coal flow) at the top of the trestle which is equal
to the gallery width.
2) Bottom width of the structure - Centre to centre distance between two
legs (across the direction of coal flow) at the bottom of the trestle.
3) Height of the structure.
4) Height of the first segment

According to the invention, the legs in figure 2, (1, 2) are made up of pipe
section located at a particular distance considering the top width, bottom width
and elevation (from ground) of the conveyor structure to be supported. The
frame consists of a plurality of horizontal bracings (4), a plurality of inclined
bracings (3), and multiple cross bracings (5). A cross bracing (5) joins an inclined
bracing (3) (figure 3) at its midpoint making an angle of 90 degree in between.
The whole trestle is divided into different segments. The number of segments
depends on the height of the structure.
The major loads that act on this trestle is the self weight, dead load if any i.e.,
cables etc., live load/ wind loads and loads from the conveyor. The pipe sections
reduces total wind load acting on the structure. The following table is a reference
from IS 875 Part III code Table 28 for Force co-efficient for single frame.

It can be seen from the above table that the force co-efficient of a pipe section is
lesser than the flat members, total wind load acting on the structure for the
same dimension, the pipe section structure has less wind load acting than the
flat member structure. For example, for an average solidity ratio of 0.3 and given
topographical condition, the wind load acting on the structure is approximately
29% lower than that on the structure with flat members.

The bracing pattern followed in the frame has an additional advantage of having
lower exposed area and contributing lesser into solidity ratio due to reduction in
length of the bracing members compared to X or cross-type bracing. The
cumulative effect will be seen in the reduction of wind load along the conveyor
direction.
While the illustrative embodiments of the disclosure has been described above, it
will be recognized and understood that various modifications can be made to the
embodiments and the appended claims are intended to cover all such
modifications which may fall within the spirit and the scope of the disclosure.

WE CLAIM :
1. An optimized and standardized two legged trestle for supporting conveyor
galleries at lower elevation in coal handling plant, comprising:
a braced single frame with two legs placed at spaced apart locations;
the single frame having two legs connected with a plurality of horizontal
as well as inclined bracings, each leg made up of a single column and two
such columns are connected by horizontal beams at a specified interval
which divides the trestle into segments.
2. The trestle as claimed in claim 1, wherein all the members of forming the
trestle are made up of standard pipe sections.
3. The trestle as claimed in claim 1, wherein the centre to centre distance at
the top of the trestle is equal to the gallery width.
4. The trestle as claimed in claim 1, comprising a plurality of cross bracings,
wherein each cross bracings joins one of the plurality of inclined bracings
at a middle location making an angle of 90°.

ABSTRACT

The invention relates to an optimized and standardized two legged trestle
for supporting conveyor galleries at lower elevation in coal handling plant,
comprising: a braced single frame with two legs placed at spaced apart
locations; the single frame having two legs connected with a plurality of
horizontal as well as inclined bracings, each leg made up of a single
column and two such columns are connected by horizontal beams at a
specified interval which divides the trestle into segments.