钢索为何是黑色的? 由于本四联络桥的架设和横滨港湾桥的开通,斜索桥作为日本全国各地的象征被广为人知。现代桥梁形式的多样化真可使人联想到“飞鸟”的美姿。然而,只要注意一下相当于“飞鸟”翅膀的斜拉索就会发现,任何一座桥上的斜索都是 Why is the cable black? Due to the erection of the fourth bridge and the opening of the Yokohama Bay Bridge, the cable stayed bridge is widely known as a symbol of Japan all over the country. The diversity of modern bridge forms really reminds us of the beauty of “flying birds.” However, once you look at the stay cables that are equivalent to the wings of a “flying bird,” you will find that the crooks on either bridge are all