Concrete thickness

Determining concrete thickness and characterising internal defects using seismic techniques... 

A problem obviously exists in trying to characterise anomalies in concrete due to the limitations of the individual techniques. Even a simple problem such as measurement of concrete thickness can result in misleading data if complementary measurements are not made In Fig. 7 and 8 the results of Impact Echo and SASW on concrete slabs are shown. The lE-result indicates a reflecting boundary at a depth corresponding to a frequency of transient stress wave reflection of 5.2 KHz. This is equivalent to a depth of 530 mm for a compression wave speed (Cp) of 3000 m/s, or 706 mm if Cp = 4000 m/s. Does the reflection come from a crack, void or back-side of a wall, and what is the true Cp ... 

Rindner et al, Preliminary Estimate of Concrete Thicknesses and Construction Costs of Laced Reinforced Concrete Structures , PATR 4441... 

Breeching is a local perforation of the concrete element by the extremely high blast pressures of a close explosion. High velocity concrete fragments can result. Breeching failures are controlled by providing adequate reinforcement, concrete thickness and standoff distance to the explosive. 

Trial Cross-Section. A trial cross-section is chosen that includes the concrete thickness, and the tension and compression steel percentages (in the horizontal and vertical directions for a two-way slab). The optimum distribution of horizontal and vertical steel is obtained when 45 degree yield lines are obtained in a yield-line analysis for ultimate resistance. The minimum steel percentage, either way and in tension or compression, is 0.15%. The optimum total positive or negative reinforcement ratio (p + py) has been found to be between 0.6% and 0.8%. A value in this range should be used for design. 

Design for Spalling. Breeching, and Fragment Penetration. Test results have been used to empirically derive relationships for the reinforced concrete thickness required to prevent spalling, breeching, or fragment penetration. 

If spalling is a hazard it can be eliminated with spall plates or by using the minimum concrete thickness, t (in). 

Preliminary Estimate of Concrete Thickness and Construction Costs of Laced R. C. Structures, PA TR UUUl, October 1972. 

Dede, M., et al. Preliminary Estimate of Concrete Thicknesses and Construction Costs of Laced Reinforced Concrete Structures, Technical Report No. 1, Picatlnny Arsenal, Dover, N.J., October 1972. (U)... 

The observed data is consistent with the findings in Figs. 12.14—12.18. The plot also shows a corrosion initiation time increase for all concrete thickness values. 

Variation- of Required Concrete Thickness, The required thickness of the concrete varies from point to point of the thermal shield for two reasons. First, the shielding required opposite the edges and corners of the thermal... 

COMR4RISON OF OVERALL BARYTES CONCRETE THICKNESS WITH DESIGN REQUIREMENTS... 

The protection against a Phantom F-4 hitting at a velocity of 215 m s requires a minimum reinforced concrete thickness of 1.8 m and, at 150 m s, a minimum thickness of 1.2 m is needed. These thicknesses also take into account the penetration strength. 

However, even if a high (parabola-shaped) trajectory missile is considered, which is not influenced by the power station layout , the necessary reinforced concrete thickness (about 80 cm) is lower than that required for the aircraft impact. The turbine missile can be several tonnes and travel with a speed of the order of 100 m s (Zwicky, 1957). 

The concrete thickness design value determined assumes the presence of a minimum 1 m edge strip or tied shoulder otherwise, the concrete design thickness should be increased by 30 mm. 

The experimental assembly consisted of two parallel linear 1x3x1 arrays of cylinders, one on each half of the tables comprising the Horizontal Displacemoit Criticality Testing Unit. The cylinders in an array were in a line perpendicular to the direction of table motion. Each array was closely reflected on five sides by 20.3-cm thickness of concrete. The remaining facing surfaces of the arrays, also reflected by close-fitting concrete, had different concrete thicknesses, 10.2 cm on the movable table and 40.6 cm on the stationary table The total thickness of concrete between the two arrays was 50.8 cm. The cylinders in each array were in contact, center... 

If the inherent capacity of the structure does not suffice, an additional barrier or distance separation should be provided. An increase in the concrete thickness of the exposed structure may also be considered if this enhances the structural capacity to resist other postulated loads. Additionally, heat resistant cladding or tumescent coatings could be used to provide further protection for structural elements. However, it should be verified that such improvements are not endangered by secondary effects potentially associated with the fire scenario (e.g. explosion pressure waves and generated missiles). 

L, Typical floor structures (i.e. offices) Hollow pot tiles Reinforced concrete Thickness type < 30 cm 18.3... 

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