Challenge

Week 6 Challenge

SShubhankar Chakravarty5 Jun 2022

Aim

To calculate the pipe loads acting on the given bridge and apply the loads on StaadPro.

Introduction

Introduction to utility Loads:

Utility loads are due to the use of various utilities related to electrical, mechnical, architectural and functional elements.
The self weight of these materials and live loads during their functional usage are considered in utility loads.
The various utility loads we are going to discuss here are:
a. Electrical lamp post, traffic signal post and direction banner loads.
b. Rain water drain pipe loads.
c. Collision loads.
d. Other live loads.

Electrical Light Mast Loading

Typical normal light post with LED lightings.
Load differs according to various vendor data like light manufacturer's product catalogue such as Philips, etc.
Typical Loads = 23kg
This load is applied according to arrangement of light poles.

Electrical light Loading - High Mast Pole

The high mast poles are placed in signals, major junctions like bus stands and rounabouts.
The load including the light fixtures and pole depends on the height of pole. Typically it varies between 10m to 20m height. Usually it is a steel structure.
Typical load = 300kg

Pipe Loads

When the pipeline is laid on the bridge for carrying water or gas, it has to be designed for the dead load of the pipe and live load of water or gas in it.
Pipes can be cast Iron-CI, Ductile Iron-DI or PVC pipes.

Introduction to Seismic loads

IS: 1893 Code

IS 1893 provides us the seismic zone map of India with Zone II to Zone IV.
Seismic loads are calculated in accordance with IS 1893 code.
Zone factor, importance factor, response reduction factor are the factors taken from IS 1893 code.

Seismic Zones of India

Seismic zones are four starting with Zone II and then Zone III, Zone IV and Zone V.
The Zone factor varies between 0.10 to 0.36 based on seismic zones.

Procedure

Given data

Width of the bridge = 3m

Bridge location = Banks of river Narmada

Length of the bridge = 24m

No. of pipes = 2

Diameter of first pipe = 700 dia NB DI

Diameter of the second pipe = 200 dia NB DI

Manual Calculations

1. Load acting due to pipe 1

Weight of 600mm dia is taken since 700mm dia is not given

As per CPHEEO manual,

Weight of pipe of 700mm dia = 217.19 kg/m

= 2.172 kN/m

Live Load due to water = area x unit weight of water

= π x 0.7 x 0.7 x0.25 x10

Total load on the bridge due to pipe 1 = 2.172 + 3.848

= 6.02 kN/m

2. Load acting due to pipe 2

As per CPHEEO manual,

Weight of pipe of 200mm diameter = 45.25 kg/m

= 0.4528 kN/m

Live load due to water = area x unit weight of water

= π x 0.2 x 0.2 x 0.25 x 10

= 0.314 kN/m

Total load on the bridge due to pipe 2 = 0.4528 + 0.314

= 0.767 kN/m

Modelling in StaadPro

Step 1: Geometry

Using Structure Wizard, we select 'Truss Models' from the drop down options and then 'Lattice Truss'.
We input the given data as shown below and import the model to StaadPro.

To add bracing to the deck, we insert nodes to the mid point along the member elements as shown below.

We then select the corner nodes and using transitional repeat command, create the columns of 7m height in the 4 corners.

With this, our geometry is complete. We now move to the Specification stage.

Step 2: Specifications

We provide the specifications bgt using the section database >> Indian>> choosing ISMB400 for the entire superstucture and 1.2m cicular pier for the columns

Step 3: Loading

We add a new Load Case Detail called Utility Loads and assign the pipe loads calculated above as member loads.
We apply Self Weight to the whole structure.