Every year I grow a lot of climbing beans. Not just runner beans but a lot of different ones. They are all nice to eat fresh, just as we pick them – best are steamed (I always steam all my vegetables, that way nothing gets lost). But after the last two summers, where I constructed the usual double lines of bean poles joined at the top and they got knocked over in the sudden high mid-summer winds, I decided to change the set up. This time I erected only a single line of beanpoles and joined them by two levels of horizontals and also placed them beside my greenhouse and the net cage, that way they’ll be sheltered.
I use the same framework to support a row of sunflowers and it works very well.
If I were you I would put bamboo over the top to join the two structures. A line of bamboo by itself is not stable enough to stay up, when in full leaf and a big wind. It needs to be a wigwam or toblarone shape really. I use a solid wooden frame and tie mine in to that.