1. Assistant Professor, Dept. of Civil Engineering, National Taiwan Univ., Rm. 313, Civil Engineering Bldg. No. 1, Roosevelt Rd., Sec. 4, Taipei, 10617, Taiwan (corresponding author).
2. Graduate Research Assistant, Dept. of Civil Engineering, National Taiwan Univ., Rm. 313, Civil Engineering Bldg. No. 1, Roosevelt Rd., Sec. 4, Taipei, 10617, Taiwan.