LOAD TEST OF CONCRETE FLEXURAL MEMBERS - METHOD - STATEMENT

LOAD TEST

This method covers the determination of the vertical deformation and strength characteristics of the structural member (Flexural Member).

 

TEST REFERENCE STANDARD

The load test will be carried out according to ACI 318M-11 Chapter 20 “Strength Evaluation of Existing Structures”.

LOAD INTENSITY

The total test load (including dead load already in place) shall not be less than the larger of the following (a), (b), (c)

(a)          1.15D+1.5L+ 0.4 (Lr or S or R)

(b)         1.15D+0.9L+ 1.5 (Lr or S or R)

(c)          1.3D 

Where

D        Dead Loads, or related internal moments and forces.

L         Live Loads, or related internal moments and forces.

Lr       Roof Live Load

S        Snow Load

R        Rain Load

LOAD TEST PROCEDURE - A load test shall not be made until that portion of the structure to be subjected to load is at least 56 days old.  - Measurements shall be made at locations where maximum deflection is expected. At-least three locations shall be monitored, one at the center and the other in areas with a suspected high deflection. - The initial value of deflection measurements using displacement transducers shall be obtained not more than 1 hour before application of the first load increment. - Test load shall be applied in not less than four approximately equal increments.  - Uniform test load shall be applied in a manner to ensure uniform distribution of the load transmitted to the structure or portion of the structure being tested. Arching of the applied load shall be avoided.  - Deflection measurements shall be made after each load increment is applied and after the total has been applied on the structure for at least 24 hours. - Total test load shall be removed immediately after deflection m - Final deflection measurements shall be made 24 hours after the test load is removed.

ACCEPTANCE CRITERIA

-	The portion of the structure tested shall show no evidence of failure. Spalling and crushing of compressed concrete shall be considered an indication of failure.

 

-	Measured deflection shall satisfy  either  equation 1 or 2

-	If the measured maximum and residual deflection do not satisfy Eq.1 or 2, it shall be permitted to repeat the load test.

-	The repeated test shall be conducted not earlier than 72hr after removal of the first test load. The portion of the structure tested in the repeat test shall be considered acceptable if deflection recovery satisfies the following condition:

Where

Δ 1 = measured maximum deflection

Δ r = measured residual deflection

l t = Span of the member under load test (mm), for the cantilever shall be twice the distance from support to cantilever end.

h =Overall thickness of the member (mm).

Δ2 = maximum deflection measured during the second test.

         SAMPLE LOADS CALCULATIONS

Say the proposed slab to be tested has a total area of 81.00m². (9.00m X 9.00m). 

(1)        Live Load Calculations 

Live Load, L.L = 2.50 kN/m²     (As per contract

(2)        Dead Load Calculations

Dead Load, D.L = Owen Wight + Flooring cover

  (To be discussed based on existing site conditions)

(3)        Load Intensity Calculations

(a)             1.15D+1.5L+ 0.4 (Lr or S or R)

(b)             1.15D+0.9L+ 1.5 (Lr or S or R)

(c)             1.3D

6.         MONITORING DEVICES

The deflection of the slab shall be monitored using an automatic data acquisition system in order to monitor the deflection away from the test area. The system comprises

• CDP Displacement Transducers (TML) - is a compact, easy-to-operate strain transducer. Because it is designed to produce a large output and to deliver stable performance, highly accurate measurements can be made. It is suitable for both static and dynamic measurements. 

• Data Taker DT85 Series – is a robust, stand-alone low-power data logger featuring USB memory stick support, 18-bit resolution, extensive communications capabilities, and a built-in display.

7.         ATTACHMENTS

Attachment A       Equipment Details