Bridges are metaphors for everything in ASCII Art
Python 2 , 173 bytes

i=input()
f=lambda b:'-|'+b[::-1].replace('/','\\')+-~(~i%2)*'-'+b+'|-'
b=(i*'/--')[:~-i/2]
for x in range(1,~-i/2):print f((len(b)-x)*'-'+b[:x]).replace('-',' ')
print f(b)

Mirror the value of b and add the central &quot;-&quot;
f=lambda b:'-|'+b[::-1].replace('/','\\')+-~(~i%2)*'-'+b+'|-'
Base pattern (right half of the bottom line)
b=(i*'/--')[:~-i/2]
Loop for non-bottom layers
for x in range(1,~-i/2):
Get the first x characters of the base pattern and complete with &quot;-&quot;
(len(b)-x)*'-'+b[:x]
Replace all - with spaces to print all the layers (except bottom)
print f().replace('-',' ')
Print bottom layer
print f(b)