Improved of the Pull Out Force of the Concrete Anchor Bolt

很多建筑物、水坝、桥梁等都是用混凝土建造的，因为混凝土很便宜，而且很丰富，墙上和地板上都有很多仪器，如机床、招牌、自动售货机等。为了将这些仪器连接到墙上和地板上，使用了多种混凝土锚杆。一般情况下，使用金属锚。金属锚是用钢做的。所述金属锚由地脚螺栓和锥体组成。当使用金属锚将仪器固定在混凝土墙上和地板上时，将金属锚插入钻孔，并锤击混凝土锚的头部。然后，通过锥体将地脚螺栓的底端展开到钻孔中，并将地脚螺栓固定在井眼中。另一方面，1995年1月17日阪神-阿瓦吉大地震发生后，混凝土墙体和楼板上的大量混凝土锚杆很容易被拔出。许多机床和仪器都掉了下来。因此，需要提高混凝土锚杆的拉拔力。因此，本文研究了提高混凝土锚杆拉拔力的方法。该方法采用倒锥孔将混凝土锚杆固定在墙体和楼板上，即孔的直径随深度增加而增大。本文研制了一种新型倒锥孔加工工具，并对其进行了拔出力测试，得到了以下结论：(1)研制了一种新型倒锥孔加工工具。它的倒锥角为10度，倒锥孔的深度为12 mm。(2)当金属锚杆固定在倒锥孔中时，拔出力大约是普通钻孔的2.8倍。

Many structures, that is a building, a dam, a bridge, and so on, are made of concrete because the concrete is very cheap and rich.Many instruments, that is a machine tool, a sign board, a slot vending machine, and so on, are attached to the wall and the floor of these structures. In order to attach these instruments to the wall and the floor , many kinds of concrete anchors are used. In general, a metal anchor is used. A metal anchor is made of steel. The metal anchor consists of an anchor bolt and a cone. When the instruments are attached to the concrete wall and floor using the metal anchor, the metal anchor is inserted to the drilled hole and the head of the concrete anchor is hammered. Then, the bottom end of the anchor bolt is expanded in the drilled hole by the cone and the anchor bolt is fixed in the drilled hole. On the other hand, a great many concrete anchor bolts are happen to be pulled out from the concrete walls and floors easily when the Hanshin-Awaji Earthquake has been occurred at 17th, January, 1995. Many machine tools and instruments are fallen down. So, it is demanded to increase the pull out force of the concrete anchor bolt.Therefore, in this study, a method for improvement of the pull out force of the concrete anchor bolt has been studied. In this method, the concrete anchor bolt is fixed to wall and the floor using inverse tapered hole, that is the diameter of the hole increases with the depth. In this study, a new tool has been developed in order to make a inverse tapered hole and the pull out force has been measured.As the result, the following conclusions are obtained.(1) The new tool to make an inverse tapered hole has been developed. Its inverse taper angle is 10 degree and the depth of the inverse tapered hole is 12 mm.(2) When the metal anchor is fixed in the inverse tapered hole, the pull out force is approximately 2.8 times larger than that of general drilled hole.