This is Bay Area Retrofit in San Francisco. The two images describing the base shear formula were taken from my video www.bayarearetrofit.com/videos-seismic-retrofitting/ with very minor modifications which violates copyright laws. I really don't mind, but would you please give me credit or anything else you used of mine? I remember giving you permission to use some of my images a few years ago but I would still like credit. Howard Cook, Bay Area Retrofit