I stood mesmerized by the sleek, slanted, gleaming white column brightly lit by the evening sun against the clear blue sky. The cables tying the column to where I was standing, a pedestrian bridge across the Sacramento River in Redding, California, with see-through glass panels for the deck, made it all the more intriguing and aesthetically pleasing.
I got the first glimpses of the Sundial Bridge when a friend of ours had visited and posted its pictures years ago.
Designed by Santiago Calatrava, a Spanish Swiss architect of renown, the bridge sports a massive tower. As a structural engineer, Calatrava has a long list of projects around the world known for their architectural statements. The tower, slanted at 42 degrees, appears to reach for the heavens. It acts as a cantilever and counterbalances the weight of the bridge with the help of the 14 cables. The strength and integrity of these cables are vital. They support both the tower and the bridge and keep them in place. Their visual aesthetics are what we see and enjoy as we take a stroll.
Interestingly, this bridge uses gravity in a creative way. The conventional design has supports on either bank (and sometimes more) of a river. This keeps the deck of the bridge from collapsing due to gravity. Calatrava’s design uses the gravitational pull on the bridge as well as the pylon tower to cancel each other through the tension in the cables.
I visualize these by picturing two yoga poses: the plank and the modified boat pose. Plank exemplifies the conventional bridge where the torso and the legs act like the deck of the bridge with firm supports on both sides, namely the feet and the hands (or elbows depending on how the yogi does it). The modified boat pose I am thinking of is where the body is in the boat pose but the hands are grasping the legs. In this picture, the legs are the bridge deck and the upper body is the pylon, with the hands acting like the cables that help the two parts counterbalance each other.
While it looks sleek and inviting, the cantilever design is not as strong as the regular construction. Think of someone pushing the yogi in the poses above. It would take considerable effort to push a yogi in the plank pose to fall over. But it is quite easy to do the same to the yogi in the boat pose. The Sundial Bridge endures this reduced stability due to the cantilever design. But as it serves just pedestrians and bicyclists and the challenges to stability are more manageable.
Aesthetics and Driving Traffic
The engineer in me marveled at the delicate details of the construction. But the artist in me just saw the aesthetics and the ambience on that cloudless, balmy, summer day.
The evening sun adding shimmer to the full flow of the Sacramento River
The emphasis on aesthetics at the expense of robust engineering appears deliberate. The project started in the early 1990’s with a goal of increasing tourism in the Redding area. It was a conscious decision to add a bridge where there was none before and drive more traffic to the area. The project ended up costing eight times the original estimate. But it was successful after its opening in 2004. Visitations rose 42% in the first year. Millions of dollars’ worth of commerce and tourism ensued each year thereafter.
Sundial Bridge cares about ecology
One of the design decisions was to leave the river free of obstructions for salmon to migrate up the river during the salmon run. The Sacramento River offers an important spawning habitat for the Pacific Salmon that swim upstream to multiply for the next season.
The 700-foot span of the bridge has no touch point in the river itself. The cantilever design made this possible, as seen below.
The cantilever design leaves the river undisturbed
Another aspect of the bridge that’s special is the translucent structural glass panels that form the deck of the bridge. These allow light to pass through them, and this is supposed to maintain the natural environment as intact as feasible (by not blocking sunlight) for the salmon in the water. (Photo on the right by Razster at the English Wikipedia)
But the bridge is lit from below in the night. That ruins the advantage of translucence; it compromises the night experience for the salmon! The only beneficiary seems to be the pedestrians and cyclists who would have light in the night for their own safety and enjoyment.
Keeping with the theme of entertaining tourists, another twist in the construction adds to the experience: The sundial. The 42-degree angle of the cantilever tower, as it is pointing precisely North, opens up the possibility of a sundial. There is a sundial patch built into the grounds. The shadow moves about one foot per minute, so you can see it move! But it may be that it is more of a talking point than of any utility. It indicates the correct time on only one day of the year: the summer solstice, on June 20 or 21. Regardless, it gives the bridge its catchy name.
Sundial Bridge: A Worthwhile Stop
All in all, the Sundial Bridge lives up to its purpose. It attracts tourists with interesting architecture, beautiful views of the Sacramento River and fun with the sundial. It is situated in the city of Redding with quick and easy access from Interstate 5. Yet, it is secluded and shielded from city noise for a peaceful sojourn.
I am glad I went and enjoyed the bridge and the surroundings on a summer day. I think I will visit it again, this time on the summer solstice, to experience the sundial in precise action!