Connection design RFIs – Retrofitting existing steel connections

This article is a part of a series "Connection Design RFIs."
Read all articles in the series.

Retrofitting – what and when

There are many reasons to evaluate existing steel structures. AISC described very well the most common ones in their AISC webinar a few years ago: 

1. Live or dead loads change
   • Building expansion 
   • Change in occupancy
   • New equipment in the building
   • Reframing: new openings, column removal
2. Repairs
   • Failures due to fire or impact
   • Corrosion 
   • Seismic retrofit

However, in this blog post, we will focus on how the IDEA StatiCa Connection app can help to revise existing steel connection adequacy to the changes. 

The process to strengthen a steel connection is to calculate the new loads for the connection, review the current materials, and calculate or find the current capacity. The engineer must decide how to strengthen the connection if it is inadequate. Some solutions provided by AISC Design Guide 15: Rehabilitation and Retrofit (Second Ed.) can be: 

• Replace rivets with bolts
• Add weld reinforcement 
• Add a welded/bolted stiffened seat connection 
• Add plate reinforcement

Why use IDEA StatiCa

In IDEA StatiCa, designing any connection is possible, no matter the geometry complexity, and you can test the recommended solutions from AISC in your model. 

Connection design capacity
Run joint design resistance analysis to determine the connection's maximum capacity with the current design. This will help you assess whether the connection can handle the new loads and whether reinforcement is needed. 

Model rivets
Modify the bolt grade in IDEA StatiCa to simulate the rivets in the current connection.

Model historic cross-sections and materials
Modify material properties to model old materials like ASTM 9. Use the cross-section database to select profiles like S-shaped wide flange beams. 

Add weld reinforcement
Use the weld operation to add welds whenever needed to reinforce the connection.

Add seated connections
Use stiffening member operation to add an angle section to strengthen the connection design.

Add a stiffening plate to any part of the model
Add plates to reinforce the seated connection or welded plates to reinforce the members near the connection.

Summary

IDEA StatiCa is a versatile solution for new and existing structural design. The Connection application easily models and quickly assesses AISC's proposed solutions. Thanks to this, retrofitting steel connections with IDEA StatiCa can save hours of hand calculations.