Week 3 Challenge

Challenge -3: Modelling & Analysis of I-Girder Bridge for IRS Loading

Problem Statement

For the I Girder bridge to be designed for the following data, the centre-to-centre distance of piers along the width of the bridge deck is 26m, Span of the bridge is 25m, Pier height is 10m, Apply the IRS railway loads and model in StaadPro and perform the structural analysis.

1. Aim & Introduction:

The main aim of the project is to understand and apply live load as per IRS standards on I-Girder bridge using StaadPro and also to understand the structural behaviour of bridge superstructure under this loading condition. The simply supported bridge with 26m width and 25m span is supported by two 2.3m diameter circular pier. The deck slab assumed of 300mm thickness with 50mm wearing coat is supported by longitudinal and cross girder as shown in Fig. The Data of the bridge is given below:

Width of the bridge deck is 26m,

Span of the bridge is 25m,

Pier size is 2.3 m diameter,

Height of Pier – 10m

Deck slab thickness: 300mm (Assumed)

Wearing coat thickness: 50mm (Assumed)

Longitudinal I Girder:

Top Flange – 1000mmX250mm

Bottom Flange-700mmX250mm

Web-700mmX250mm

Overall Depth-1200mm

c/c distance between main girder: 3.5m

2. Procedure

2.1 Live Load Considered as per IRS

2.2 Modelling, Application of Live Load and Analysis in StaadPro

Analysis in StaadPro consist following Steps:

1. Geometry
2. Define & Assign Members
3. Define & assign the load
4. Define & assign the support
5. Analysis
6. Post processing of Results.

For the considered bridge, the main girders are modelled as a I beam using general elements and deck slab is modelled as a 4 point plate elements.

2.2.1. Geometry of Bridge

The geometry in StaadPro is created by define the nodes using coordinate system and beam is drawn using beam command as shown in Fig. and then using translation command full geometry as per requirement can be modelled.

2.2.2. Define & Assign Members

2.2.3 Define & Assign the load

The Following loads are considered for the analysis:

1. Dead Load – Self weight of deck and wearing coat and kerb beam.

The Load cane be defined by using Load & Definition command and for live load as a moving load can be defined using vehicular definition in load & definition command as shown in Fig.

For the self-weight of wearing coat, the loads is applied as a plate load in vertical direction as shown in Fig.

Self-weight of deck and girders are applied using self-weight command in vertical downward direction.

Wearing coat – 50mm thick – Self weight = 0.05X25=1.25 kN/m²

2. Live Load – IRS Loading

The live load for I-Girder bridge is considered as shown in Fig. The axle load is 17t and there are 4 load of 17t is acting on the bridge as a moving load.

2.2.4 Define and Assign the Support

The simply supported bridge is supported on hinged support and it can be defined under the section of supports and assign at the end of main girders at each span as shown in Fig.

2.2.5 Analysis

The analysis of bridge can be initiated by command analysis print command as shown in Fig.

2.2.6 Post Processing of Results

The post processing of the results can be obtained in post processing tab of StaadPro as shown in Fig.

The results for the plate elements and rectangular beam elements are shown in Fig.

3. Results

The results can be obtained through the post processing mode and can be extracted through report also and hence some sample diagram and table are shown in Fig.