Proceedings of the twenty-first national conference on structural engineering 并列题名：Proceedings of the twenty-first national conference on structural engineering Proceedings of the twenty-second national conference on structural engineering Proceedings of the twentieth national conference on structural engineering Proceedings of the eighth national conference on structural engineering Proceedings of the ninth national conference on structural engineering Proceedings of the seventh national conference on structural engineering Proceedings of the ninth national conference on structural engineering 并列题名：Proceedings of the twenty-second national conference on structural engineering 并列题名：Proceedings of the twentieth national conference on structural engineering