John M. Hanson, who, as president, helped guide the growth of Wiss, Janney, Elstner Associates Inc. into an industry-leading forensics and failures engineer and who led probes into high-profile collapses of the Kansas City Hyatt hotel walkway in 1981 and the New York State Thruway Schoharie Creek Bridge in 1987, died on May 26 in Green Valley, Ariz., at 84.