Damage detection based on strain responses of vibration is highly attractive for monitoring long-span reticulated structures.However,there are a lot of structure members in reticulated structures and it is impossible to install strain sensors in each member.Therefore,how to locate and quantify damages with the incomplete mode shapes obtained from few strain sensors is a challenge topic.A new strategy,named incomplete strain mode damage detection(ISMDD) strategy,is proposed in this paper.In the strategy,the distribution of the strain sensors in the reticulated structures can be optimized through sensitive analysis on strain mode perturbation matrix,which can be obtained by perturbation theory.Mode assurance criterion(MAC) value is applied in damage location,and the members with relative large MAC values are defined as damage members.In addition,damage index obtained by solving the perturbation equation is used for damage quantification.Numerical analysis on a long-span reticulated structure,including damage location and quantification for single-and multi-member damages,detection for different damage quantity,the effect analysis of sensor quantity,are performed to verify the effectiveness of the proposed ISMDD strategy.It can be shown from the analysis that the ISMDD strategy is effective in damage location and quantification for both single-and multi-member damages.And the quantity of strain sensors has effect on damage location,but has no obvious influence on damage quantification.Additionally,the anti-noise pollution ability analysis of the ISMDD strategy is carried out,which shows that the ISMDD strategy has excellent anti-noise pollution ability for both single-and multi-damaged members. Damage detection based on strain responses of vibration is highly attractive for monitoring long-span reticulated structures. However, there are a lot of structure members in reticulated structures and it is impossible to install strain sensors in each member. Wherefore, how to locate and quantify damages with the incomplete mode shapes obtained from few strain sensors is a challenge topic. A new strategy, named incomplete strain mode damage detection (ISMDD) strategy, is proposed in this paper. In the strategy, the distribution of the strain sensors in the reticulated structures can be optimized through sensitive analysis on strain mode perturbation matrix, which can be obtained by perturbation theory. Mode assurance criterion (MAC) value is applied in damage location, and the members with relative large MAC values ​​are defined as damage contributors. , damage index obtained by solving the perturbation equation is used for damage quantification. Numerical analysis on a long-span reticulated struc ture, including damage location and quantification for single-and multi-member damages, detection for different damage quantity, the effect analysis of sensor quantity, are performed to verify the effectiveness of the proposed ISMDD strategy. It can be shown from the analysis that the ISMDD strategy is effective in damage location and quantification for both single and multi-member damages.And the quantity of strain sensors has effect on damage location, but has no obviously influence on damage quantification. Additionally, the anti-noise pollution ability analysis of the ISMDD strategy is carried out, which shows that the ISMDD strategy has excellent anti-noise pollution ability for both single and multi-damaged members.