How do I fix this sagging pergola?

[3WA]

I just want to say I am so impressed with how much you guys all know about pergolas.

 

[KleinBoontjie]

iBeam, hidden behind the front plank, post to post.

 

[RedViking]

I just want to say I am so impressed with how much you guys all know about pergolas.

I design pergolas, but all calculated for New Zealand timber sizes.

 

[KleinBoontjie]

I just want to say I am so impressed with how much you guys all know about pergolas.

Not just pergolas, but fixing **** in general is our national pastime, in this country. We even need municipalities to issue court orders to stop you from fixing ****.

 

[rh1]

I just want to say I am so impressed with how much you guys all know about pergolas.

My plan is to do something similar myself. As in DIY, but without looking DIY, but something done professionally. So I am watching and learning as much as I can.

 

[jezzad]

Stumbled upon something yesterday similar to this, how to connect to pieces of timber together.

You can use something called a scarf join (image below)

 

[WaxLyrical]

Another thing to bare in mind is that the beam might have permanently warped due to weight and weather.
Run a piece of string from one end to the other and pull taught to determine how much it has actually sagged.

Beam needs to be straighted before it's reinforced. Might have to replace as last option

 

[PilgrimToHyperion]

Thank you so much for the wonderful input everyone. Had to deal with a family tragedy so have not been online much. I'll go through these and look at the options available. Thank you to those who have PM'd as well.