SECTION 2.5Misfits and Prestrains117Problem 2.5-16A rigid steel plate is supported by three posts of high-strength concrete each having an effective cross-sectional area A5 40,000 mm2and length L5 2 m (see figure). Before the load Pis applied, the middle post is shorter than the others by an amount s 5 1.0 mm. Determine the maximum allowable load Pallowif the allowablecompressive stress in the concrete is sallow520 MPa. (Use E530 GPafor concrete.)Solution 2.5-16Plate supported by three postsSPCCCLsPCLsSteel plates5size of gap51.0 mmL5length of posts52.0 mA540,000 mm2sallow520 MPaE530 GPaC5concrete postDOES THE GAP CLOSE?Stress in the two outer posts when the gap is justclosed:Since this stress is less than the allowable stress, theallowable force Pwill close the gap.515MPas5Ee5E¢
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