A system includes a sensor network comprising a network of optical sensors coupled to structural members of a structure loaded by vehicles or by an environmental event. A processor is operatively coupled to the sensor network. The processor is configured to receive the strain measurements from the network of optical sensors, calculate total strain energy using the received strain measurements, detect a heavy load on the structure in response to the total strain energy exceeding a total strain energy threshold developed for the structure, and determine whether the heavy load results from a superload vehicle or the environmental event. A transmitter is operatively coupled to the processor and configured to transmit one or both of an alert and a condition assessment report for the structure to a predetermined location in response to determining that the heavy load results from the superload vehicle or the environmental event.