297. End-Method Arches

In this method the blocks are generally made rectangular in shape, with one vertical and one horizontal partition, and with bevel end joints. In this system it is not the practice to have the blocks in one row break joint with those in another, as it entails extra expense in setting. When this is done, however, the substantialness of the floor is increased.

297 End Method Arches 100191

Fig. 178.

297 End Method Arches 100192

Fig. 179.

297 End Method Arches 100193

Fig. 180.

The most common type of end-method arch is that shown in Fig. 178, which was first brought into general use by Mr. Thomas A. Lee, and is often designated as the "Lee End-method Arch." It has the advantage of simplicity and economy in manufacture, as all the blocks for a given depth of arch can be made with one die. Most, if not all, manufacturers making this type of arch use porous terra cotta in its construction. These arches require very heavy webs in order to give sufficient bearing on the beams, which greatly increases the weight of the arch. Fig. 179 shows an isometric view of one of the "butment " pieces or hanches.

Some complaint has been made by architects that they find it difficult to get a strictly flat ceiling with this type of arch.

The open ends of the hollow tiles not being well adapted to receive mortar for the mortar joint, the mortar often squeezes out, permitting some of the blocks to drop below the others.

As there is no bond between the rows of tiles, if a single tile in a row should be broken or knocked out of place, the entire row will fall, and for the same reason a single tile cannot be omitted for making a temporary hole, as may be done in side-method arches.

Where the tile blocks abut endways they should be cut to fit perfectly between the beams, so that the divisions will abut perfectly against each other. Solid plates may, however, be placed between the ends of the tile blocks without injurious effect, and, in fact, the author believes that such plates would give a stronger joint.

297 End Method Arches 100194

Fig. 181.

Fig. 180 represents the transverse system of floor arch construction now made by the Pioneer Company. The interiors are of the same shape as those used in their former system (Fig. 181), sometimes called the Johnson Arch, but instead of using parallel abutments end-section abutments are used, as shown in the figure. Whenever the former system was tested to destruction the abutments were almost invariably the parts which failed. It was for this reason that a different style of abutment or skewback was adopted, and the manufacturers claim that they now have the strongest and lightest flat tile arch on the market. This arch is made of dense tile, with webs and flanges and inches thick respectively.