Punching strengthening of two-way slabs using a prestressing technique

El-Shafiey, Tarek F.; Atta, A.A.

doi:10.1201/b11585-28

Cited by 1 publication

(2 citation statements)

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“…Also, the Egyptian code, ECP 203-2007 [30] uses the same equation in MPa unit. Table (6) illustrates a comparison between the prestressing forces at ultimate obtained from experimental results of the two control specimens (without ECC layer) S-0-0 (f cu =15MPa), S-0-0* (f cu =40MPa) , and the pervious equations. It was found that the ACI and BS8110 underestimate the ultimate stress in the pre-stressing steel of the tested slabs by more than 20% for low concrete strength and by 48.5%, 37.4% respectively for moderate concrete strength.…”

Section: Proposed Tendon Stress Prediction Modelmentioning

confidence: 99%

“…This type of prestressing can be applied to both new and existing structures that need to be strengthened due to several reasons such as: changes in use, deficiencies in design or construction phase and structural degradation. At present, the application of external prestressing to deteriorated, overloaded or aging existing structural members using unbonded tendons is proving to be a very effective and promising in strengthening structural elements or systems [5,6,7,8,9,10]. Even in well designed concrete members cracking is the main cause of failure as it can lead to loss of structural integrity allowing partial or total collapse mechanisms to occur.…”

Section: Introductionmentioning

confidence: 99%

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2017

IOSR JMCE

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External prestressing is commenly used with notable effectiveness to increase and upgrade the flexural capacity of Reinforced Concrete (RC) beams and slabs. However, the major practical difficulty associated with external prestressing is that, it must be applied to relatively high strength concrete elements which may not be met in many cases where geometry and properties of concrete and steel reinforcement of existing member can't be modified. Hence the designer has no control on the existing structural elements that need repair. This research is aims to develop and evaluate an innovative strengthening technique for low strength concrete slabs. This method is based on applying a thin layer of Engineered Cementitious Composites (ECC) in the compressive side of RC slabs prior to the application of the external prestressing tendons. The role of the proposed ECC layer is to avoid the early concrete crushing in compression side, and consequently increase the efficiency of the external prestressing. To investigate the efficiency of the proposed strengthening technique, a total of nine RC slabs cast by low concrete strength (compressive strength = 15 MPa). Application of external prestressing solely would induce brittle failure by abrupt crushing in concrete at the low strength compressed soffit. For That purpose, two different thicknesses of ECC layer were considered in the first group of the experimental program. Strengthening process at three different levels of sustained loading was also taken into account through the second experimental group. The present study indicated that the proposed hybrid strengthening technique was is a very powerful tool for enhancing the capacity of the considered case study. Evaluation of some of the existing analytical formulae of tendon stress was finally made. In addition, a proposed prediction formula of the ultimate tendon stress for the case of the studied hybrid strengthening technique was presented.

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Section: Proposed Tendon Stress Prediction Modelmentioning

confidence: 99%