HUBUNGAN ANTARA TEGANGAN-REGANGAN (STRESS - STRAIN RELATIONSHIPS) PADA BETON

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ABSTRACT

Thereinforced concrete structures has been used more of structureswhere the compressive force was endured by concrete coused compressive stress  and  steel has tensile strength so it be coused tensile stress be holded by steel.The compressive strength concrete is usually obtained from cylinders with a hight to diameter ratio of 2. The cylinders are loaded longitudinally at a slow strain rate to reach maximum stress in 2 0r 3 minutes. The stress-strain curves obtained from concrete cylinders loaded in uniaxial compression in a test conducted over several minutes. The stress-strain relationships can be showed at stress-strain curve , where this curve can be obtained from cylinders test with uniaxial compressive test, biaxial compressive test and triaxial compressive test, with high intensity  repeated axial compressive cycle loading.  The axial stress-strain curve obtained by Richart at all for compression test conducted on concrete cylinders. The cyliders confined laterally by fluid pressure. For each curve the fluid pressure held constant while the axial compressive stress was increased to failure and the axial strain measured.The tensile strength of concrete generally less than 20 % of compressive strength, can be obtained direcly from tension specimens. Tensile strength of concrete may be measured indirectly in term of the computed stress at wich a cylinder placed horizontally in a testing machine and loading along the loaded diameter will split, and can be also be evaluated  by means of bending test conducted on plane concrete beams.The tension stress-strain relationships can be obtained from those testings.

Key Words: Stress - Strain Relationships

PENDAHULUAN

Beton merupakan bahan konstruksi yang banyak digunakan, baik untuk bangunan ringan maupun bangunan berat, karena beton mempunyai kuat tekan yang besar sedangkan gaya tarik sangat kecil.  Jika dilihat dari komposisi beton terdiri dari campuran agregat, semen dan air atau bahan tambahan lainnya, bahan-bahan tersebut menjadi padat dan keras karena semen dan air mengalami proses kimia mengikat agregat  sampai menjadi sangat keras. Dalam struktur bangunan, beton dipercayakan untuk menahan gaya tekan sedangkan gaya tarik ditahan oleh tulangan baja, maka beton yang diberi tulangan disebut beton bertulang (reinforced  concrete).  

Beton yang mengalami gaya tekan tentunya menimbulkan tegangan (stress)di dalam beton. Tegangan ini menyebabkan bahan beton mengalami regangan (strain), sehingga perlu kiranya untuk mengetahui hubungan antara tegangan dan regangan pada beton.

Sifat Tegangan Satu arah (Uniaxial Stress Bihavior)

Dalam praktek beton jarang menunjukkan tegangannya dalam satu arah (uniaxial stress), untuk ini banyak dari konstruksi beton structural, tegangan yang yang terjadi bersamaan dengan arah gaya yang diberikan, dengan kata lain suatu uniaxial stress dapat terjadi dalam segala arah.