Dear Loyda, the answer depends at least partially on the kind of data you have. If you dispose i.e. on a NxN actor matrix you can generate triads. I proposed a measure for social capital based on triadic positions in "Connections": Measuring the Social Capital of Brokerage Roles. Another possibility would be the "ressource generator" as proposed by T. Snijders.
A widely used and validated instrument for measuring social support, at least in the U.S., is the MOS Social Support Survey Instrument. It has 19 items but there are also abbreviated versions available. You can access it at the link below.
Also don't underestimate the power of qualitative data, I found evidence for the role of social networking online in developing bridging social capital amongst rural SMEs: https://www.researchgate.net/publication/268579596_Building_Virtual_Bridges_How_Rural_Micro-Enterprises_Develop_Social_Capital_in_Online_and_Face-to-Face_Settings
Article Building Virtual Bridges: How Rural Micro-Enterprises Develo...
Creo que es importante la evidencia empírica, tanto como la generación de modelos estadísticos. Dos tipos de cohesión en grupos existen :de redes y de puentes. La CIEPLAN en Chile ha trabajado una serie de indicadores al respecto muy interesantes, pueden seevirte
I think that Name Generator methodology is a key tool to measure social support and social capital. You can see the work of VanDerGaag . Also we apply many name generators in a Survey in México about Quality of Citizenship:
Try the Measurements Book that comes out every year or so with measurements for all things that need measuring in the social sciences. Each measure is evaluated on such factors as validly, reliability, ease of use, time, etc.