In engineering structures,various damages are generated in service,which can result in serious destruction of the integrity of structures.Thus,the damage identification and detection research is significant to reduce or avoid the loss caused by damages.This paper presents a vibration-based method for detecting bolt looseness in frame structures.The proposed signal method is based on empirical mode decomposition(EMD),which decomposing a signal into a set of different bands of signal components referred to as intrinsic mode functions(IMFs).