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the cumulative effects of impact loading; i.e., successive impacts of increasing magnitude might possibly lower the impact resistance of the fixture.

2.5. Concentrated Load, Sump Sidewall (Bathtub) (S104)

a. Purpose and Scope

The purpose of this test is to determine if the sidewalls of the sump of a bathtub can withstand highly concentrated loads of relatively small magnitude without excessive deflection, denting, indentation, or other damage. The service load simulated would be the pressure exerted by a person bracing himself against the side of a bathtub, or other similar load applications during normal

use.

b. Recommended Test Method

(1) Apparatus

The load-application and deflection-measuring devices shall be essentially as shown in figure 2.5-1. The 1-in-diam steel ball shall be cemented to the arm. The lengths of the lever arms for the loading device shall be equal to within 0.01 in to provide for a one-to-one transfer of the load. The counter balance shall be adjusted so that the level system is balanced without the weight hanger.

The tripod used for holding the 0.001-in dial gage shall have thin rubber pads mounted on its feet and shall have sufficient stiffness and weight to prevent movement of the tripod during test. The hanger for the loading weight shall weigh 0.5 0.1 lb, and the test load weight shall be 25.0 0.1 lb including the hanger. The load may be applied in increments.

(2) Test Procedure

Mount and prepare the bathtub for test as specified in section 2.2. Inspect the finished surfaces for defects and damage in accordance with section 2.8 prior to test. Maintain the temperature of the testing laboratory and bathtub at 75 ± 5 °F.

FIGURE 2.5-1. Deflection test for unsupported area.

Apply the test load of 25 lb to the sidewall of the sump at midheight. Test four positions, including two near the midlength of the front and rear side walls. The other two positions are to be about 12 in horizontally from the original positions and on nearly vertical walls. Read the dial gage immediately after loading.

When setting up the testing device shown in figure 2.5-1, take special care to ensure that:

1. The level arm with the load-application ball is parallel to the surface being tested.

2. The stem of the dial gage over the load-application point is directly on the centerline of the ball.

3. The stem of the dial gage is normal to the surface on which it is resting.

The loading procedure is as follows:

1. Apply the hanger and observe initial deflection reading on the dial gage.

2. Apply test load and observe the deflection reading.

3. Inspect the tested surface in accordance with section 2.8, following removal of load. Take special care to determine if indentation of the surface at the load point has occurred.

(3) Information to be Reported

Include the following in the test report:

1. Specimen identification;

2. Description of test frame and method of supporting and fastening;

3. Defects and damage noted prior to test; 4. Damage noted after test;

5. Positions of test areas;

6. Deflection readings made at each position.

c. Test Results and Discussion

(1) Discussion of Existing Methods

Commercial Standard CS 221-59 [2] includes a requirement for a deflection test for unsupported areas. A load of 10 lb is applied through a 1-in

round steel bar rounded to a 12-in radius at the end in contact with the bathtub. The maximum deflection allowed under this load is 1 in. No permanent deflection is allowed. The proposed revision of CS 221-59 [1] is essentially the same except that the deflection is to be determined with a 0.001 in deflectometer and the no-permanentdeflection requirement was withdrawn. In addition, the proposed revision specified that surface cracking as a result of the test shall constitute failure.

Neither version of the Commercial Standard specified methods for applying the load or for measuring deflection.

There are no other known standard test methods which are similar in purpose to that recommended here.

(2) Test Development

Initially a simple hand-held instrument that would overcome the drawbacks in the method outlined in CS 221-59 was considered. A preliminary design was developed for an instrument similar in principle to the rubber-hardness-testing durometer. As time was of the essence, this idea was dropped and the simple lever-dial-gage arrangement shown in figure 2.5-1 was adopted for the

test.

The device used in the test work was the same as shown in the drawing except that an additional dial gage was added to measure deflections 42 in from the load point. It was thought that this additional deflection measurement could be used to judge the extent of the cupping effect when the load was applied.

The load of 10 lb specified in CS 221-59 was thought to be unrealistically low. After preliminary tests indicated that no surface damage should be expected, the load was increased to 25 lb for the test work.

Table 2.5-1 presents the deflection data from both gages for all bathtubs tested. The ratio of the two deflections can be used to judge the extent of the cupping for flat areas without reinforcing members or back-up material. The more flexible FRPE tubs had stiffening ribs or back-up materials which affected the deflection ratios greatly. For this reason the measurement of deflections 412 in from the load point is not recommended.

The measured deflections at the 25-lb load point varied considerably, especially for the PB-4 tub. This bathtub had a 3%-in stiffener cemented to the backwall, but none on the front wall. The wall thickness varied considerably on the FRPE tubs, so some variation in deflections was expected. No visible surface damage, denting or indentation was caused by the testing.

Table 2.5-2 summarizes the deflections observed when a 10-lb load, as prescribed in CS 221-59, was imposed on the sidewalls. The maximum observed deflection on any specimen was slightly less than half that permitted by the Commercial Standard.

352-020 070- -3

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(3) Rationale for Test Selection

The basic principles outlined in CS 221-59 were preserved, but methods for applying the load and measuring the deflection were incorporated. It was felt that these methods should not be left to each testing laboratory to develop.

Commercial Standard CS 221-59 originally required that there be no permanent deflection. A requirement for no permanent deflections seems unnecessary because the small permanent deflections resulting from the test have no aesthetic or functional significance. These very small deflections are difficult to measure and the lack of precision in measuring them might lead to difficulties in interpretation of test results. For determining the presence of any relatively large permanent indentations, or denting, the use of the surface inspection routine of section 2.8 is satisfactory.

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d. Comments on Performance Requirements (1) Suggested Format for a Performance Level Visible surface-finish damage including denting or indentations shall not be present at any of the four test positions after removal of the 25-lb load. In addition, the deflection at any of the four test points shall not be greater than in during load application.

(2) Rationale for Suggested Format

The reason for suggesting a limiting value for the deflection under the load point is to limit the flexibility of the sidewall material. A requirement for no surface damage under a reasonable loading is desirable, since concentrated loads are sometimes applied to sump sidewalls in service.

It can be seen from the data in table 2.5-1 that the sidewall deflections of the tubs tested were all less than 0.200 in.

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ious configurations of the drain-hole outlets), a detachable lever arm, and a micrometer dial gage mounted so as to measure movement of the lever arm when a bending moment is applied.

The lever arm, with the gage mounted, shall weigh 7.25 lb to produce an initial moment of 10 ft-lb. The weights and hanger shall weigh a total of 20 lb to produce an additional moment of 40 ft-lb. Four, or more, weights of approximately equal mass shall be provided.

(2) Preparation of Test Specimen

Mount the bathtub and prepare for test as specified in section 2.2. Take special care to fasten the specimen securely to the frame. As an additional precaution, add at least 100 lb of weight distributed over the bottom of the sump so as to approximately cancel out the overturning moment of the test load.

When assembling the connecting device to the bathtub drain hole, adjust the collar so that there will be no physical contact between the top washer and the tub. Place a bedding of freshly mixed plastic of Paris around the connection as illustrated in figure 2.6-2. Plumb the vertical member of the connecting device when the plaster is placed. When the plaster is partially set remove excessive plaster so that no plaster extends beyond the 3-indiam washer and collar.

Finally, when the plaster is hardened the horizontal lever arm shall be attached to the connecting device and the deflection-measuring dial gage shall be adjusted for indication of vertical

movement.

(3) Test Procedure

1. Before beginning the test, inspect the inside surfaces of the bathtub for damage and defects in accordance with section 2.8. Maintain the temperature of the testing laboratory and bathtub at 75±5 °F.

2. Make the test in at least two radial directions 90° apart, including one for which the lever arm is parallel to the long direction of the bathtub.

3. With the lever arm in place, record the initial dial-gage reading. Place the weights individually on the arm, and record deflection for each incre ment of load. Continue loading until the indicated deflection is equal to or greater than 1.25 in, or until an additional load of 20 lb (40 ft-lb of moment) has been applied.

4. After application and removal of the load, again inspect the inside surfaces of the tub for damage attributable to the test in accordance with the inspection procedure prescribed in section 2.8. (4) Information to be Reported

Include the following in the test report: 1. Specimen identification;

2. Description of test frame and method of supporting and fastening specimen in frame;

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3. Damage and defects noted prior to test; 4. Damage noted after test;

5. Radial direction of lever arm for each test position;

6. The deflections for each load increment at each test position;

7. The weight added at each increment (including the weight hanger).

c. Test Results and Discussion

(1) Discussion of Existing Methods

A drain-fitting-connection test is described in Commercial Standard CS 221-59 [2]. This test method requires that a 25-lb weight be applied by means of a lever arm two ft in length connected to the drain fitting extending horizontally in a plane parallel to the rim of the tub. The arm and weight are placed in three radial positions, two of which are approximately 180° apart. The performance requirement for this test is that no visible cracks in the bathtub surface shall be evident when inspected with the fitting in place using a standard ink test. In the proposed revision of CS 221-59 [1], the test was changed to require the application of a 50-lb weight through a 2-ft lever arm. The performance requirement was not changed in the proposed revision.

(2) Test Development

The test as described in CS 221-59 applies the load through a "drain fitting connection." After examining several drain fitting connections produced by different manufacturers it was obvious that the rigidity of the fittings themselves would be a factor to be considered in the test. In order to standardize the test it was necessary to design a "standard" drain fitting connection so that the same test conditions would apply to all tubs. The

recommended apparatus for the drain fitting test is shown in figure 2.6-1.

After the apparatus was designed, it was necessary to consider the magnitude of service loads and/or movements which would be encountered by a bathtub in service. The applied load in service would usually result from the restraint offered by the soil or waste stack to the downward movement of a bathtub supported by framing members undergoing drying shrinkage. If lumber is not dried before installation, the shrinkage of 2- x 10in joists can be as much as 1/2 in in the 10-in direction.

An auxiliary test was performed in order to determine how much of this movement might be transferred to the bathtub as bending moment through the connecting assembly. This test was made with a cast-iron tub placed upside down on the floor and weighted at each corner to offset overturning moments. Two different drain-fitting assemblies, complete with overflows and traps were obtained for this test. One assembly included a cast-iron trap and the other a 17-gage brass-tubing trap. Otherwise the assemblies were similar. Each assembly was installed on the inverted bathtub and loads were applied to a pipe extension of the trap outlet as shown in figure 2.6-3. The distance from the drain outlet to the point at which the load was applied was chosen as the shortest possible between the drain and the stack. This would simulate the most severe condition occurring in service as a result of relative vertical movement. The movement of the outlet end of the trap was measured by a 0.001 in dial gage supported on the floor. The results of the tests made in this way are shown in figure 2.6-4 and indicate that a load of about 50 lbs applied at a distance of 1114 in from the centerline of the drain caused a relative movement of about 1/2 in at the point of deflection

measurement.

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FIGURE 2.6-3. Test arrangement for evaluating rigidity of commercial drain-fitting

assemblies.

Using these data as a guide the drain-fitting-load test was performed on one specimen of each available bathtub sample. The test procedure was as recommended in 2.6b and the data are presented in table 2.6-1. Figure 2.6-5 presents some typical moment-deflection data obtained for one specimen. As is indicated in this figure the initial deflection readings were with the 10 ft-lb of moment contributed by the weight of the lever arm. Because the deflection caused by this moment was not measured directly the moment-deflection curves for each specimen were graphically extended back

to zero-moment. Deflections determined by this method are entered in table 2.6-1 as the "zero-offset." The zero-offset data are considered to be approximate because of the curvature of some moment-deflection curves.

(3) Rationale for Test Selection

The service load which this test method is intended to simulate is that resulting from a differential vertical movement between the tub and waste or soil stack. The material of the tub around the drain outlet hole should be either (a) flexible

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