aspnet_Users table and aspnet_Profile table - getting relationship right.

I am using Asp membership controls in my project. I have aspnet_Users table that keeps users log in information. I understand that if I want to add custom fields about the user like email, phone etc, I can use asp profile which adds these additional fields to the aspnet_Profile table. 
1. Does it add the new field as an additional column in aspnet_Profile table?
2. Lets say  I add TripId as a custom field to the profile table. TripId actually comes from another table called tblTrips where it is the PK for that table. A single tripId can have multiple UserIds. How do I get this relationship work .. If I had TripId in aspnet_Users, it would be simple, but  I cannot do that.. I am adding this tripId to aspnet_Profile table.. so how can I achieve this one to many relationship between tblTrips and aspnet_Users table.
Thanks in advance for help.
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