Analysis and Design of Box Culvert : A Manual Approach

Box culverts are the monolithic structure made to pass across a roadway, railway lines etc. Embankments are used to balance the flood water on both sides. Box takes various types of loads generated by water, traffic, cushion, soil etc. This work deals with complete design of box culvert manually and study the design parameters such as effect of earth pressure, depth of cushion at the top slab of culvert, factor such as braking force, Impact load, Live load, Dispersal of load through tracked or wheeled vehicle, effective width etc. In this work, study of culvert with and without cushion analyzed for different classes of IRC loadings and conclusions made on the basis of bending moments and shear forces with and without cushioning cases. This paper provides full discussion of provisions provided by Indian Standards, their justifications and considerations are taken into the account for design purpose. Keywords— Box culvert, Cushioning, Loading class, Moment calculations, Percent reinforcement, Pressure cases, Side walls, Top slab.


I. INTRODUCTION
Box culverts are low rise bridge or structure which is used to discharge water in the proper channel in crossing of railway, flyover, roads etc. and is used where the bearing capacity of soil is low.Culverts are always economical than bridge where the discharge in the opening is 18 m2 it depends on the number of cells which is generally used where roadway crosses the high embankment.Box culverts are generally cast in situ in India, but in other countries the box culverts are preferred due to low cost and economically with having fast workmanship.The box is just name given for its shape, can be found in various types of shapes and also it can be act as minor bridge when the number of cells increases and span greater than 6m in length.Its height depends on span.It can control all water coming from irrigation, surface water, river and canals they control all the storm water and flood water during rainy season.
Box culverts which have four corners are monolithically jointed.In other cases the box will be of three sides means which has bottom slab (Raft) and vertical walls.Top slab needed to be made otherwise precast slab also available in market we cannot joint it monolithically.Cushioning is very important in every box culvert which decided by road profile and bearing capacity of soil available at site.

According to the Classification by Loading as per IRC
As per IRC 6, the value for Class A provided is 114 KN for wheeled vehicle.3.3)IRC-CLASS-B:-Thisloading is preferred on each and every road on which temporary structures are made and for bridges the different materials are used respect to situations.As per IRC 6, the value for Class B provided is 68 KN for wheeled vehicle.

III. CASES TO BE SOLVED & PARAMETERS USED For
this work, total six cases are taken for analysis and design.For that each case is numbered as Case A, Case B, etc. Description for Without Cushion and With Cushion cases are mentioned in table 1.

Table . 1
:-Types of cases used with description as per loading class Cushion Type Cases Description Without Cushion CASE A 350 KN of Tracked vehicle using Class-70(R) CASE B 114 KN of Wheeled vehicle is using Class-A CASE C 68 KN of Wheeled vehicle is using Class-B With Cushion CASE D 350 KN of Tracked vehicle using Class-70(R) CASE E 114 KN of Wheeled vehicle is using Class-A CASE F 68 KN of Wheeled vehicle is using Class-B For this work, parametric values taken for analysis and designing of box culvert.Description for both Without Cushion and With Cushion cases are mentioned in table2.Table.2:-Parametersusedfor designingFig.1:Box culvert without cushion Fig.2: Box culvert with cushion IV.

Table 4 :
-Values of Braking Forces