3. A multistory cast-in-place reinforced concrete building is to be constructed using a system of shores and reshores. The typical slab thickness is 6". Slab design loads, construction loads, and relative concrete strength (as a percent of 28-day strength) at various ages are as follows: Design Loads Construction loads Slab weight = 6/12 ft x 150 pcf = 75 psf (D: slab wght) Slab weight..... = 75 psf (D) Superimposed DL (ceiling+MEP)= 40 psf (0.53 D) Forms and shores - 10 psf (0.13 D) Live load.... . = 65 osf (0.87 D) Weight workers & equipment = 40 psf (0.53 D) Total design load.. .. = 180 psf (2.40) Total construction load.... = 125 psf (1.67 D) Note: Neglect reshore weight Slab Carrying Slab Load to be Load on Age Capacity Load by slab shore/reshore 30% Concrete Strength Percent of 28-day strength Age % 3 days 4 days 45% 5 days 55% 7 days 65% 14 days 80% 21 days 90% 28 days 100% 2 Total: Figure 1 For one level of shores and 2 levels of reshores, as shown in Figure 1, a construction rate of 1 floor per week, for the construction stage shown (casting of slab 4), determine for each slab: (3 points) (a) Slab age (b) Slab carrying capacity (based on relative strength and design load) (c) Applied load on each slab, including construction load at level 4 and slab weight at levels 1, 2 and 3 (d) Load to be supported by each slab, including its weight and its share of the construction load at level 4 (assume load at level 4 is distributed equally to the three interconnected slabs) (e) Load to be supported by shores/reshores (f) Required spacing between shores/reshores at each story (assuming maximum allowable load on each post is 3,000 lb, as in example 3). (g) Comparing carrying capacity (a) and load to be carried (c), conclude if for the planned construction rate, it is appropriate two levels of reshores. (Could it be just one level? Should the contractor use three levels of reshores instead?) (h) Determine how many days after casting slab 4, can the shores and forms be removed (Hint: compute carrying capacity at 3 days, 4 days, 5 days and 7 days and see when it is greater than D) Note: in your calculations you may use actual loads (psf = 1b/ft2) or factor of slab weight, D) 3. A multistory cast-in-place reinforced concrete building is to be constructed using a system of shores and reshores. The typical slab thickness is 6". Slab design loads, construction loads, and relative concrete strength (as a percent of 28-day strength) at various ages are as follows: Design Loads Construction loads Slab weight = 6/12 ft x 150 pcf = 75 psf (D: slab wght) Slab weight..... = 75 psf (D) Superimposed DL (ceiling+MEP)= 40 psf (0.53 D) Forms and shores - 10 psf (0.13 D) Live load.... . = 65 osf (0.87 D) Weight workers & equipment = 40 psf (0.53 D) Total design load.. .. = 180 psf (2.40) Total construction load.... = 125 psf (1.67 D) Note: Neglect reshore weight Slab Carrying Slab Load to be Load on Age Capacity Load by slab shore/reshore 30% Concrete Strength Percent of 28-day strength Age % 3 days 4 days 45% 5 days 55% 7 days 65% 14 days 80% 21 days 90% 28 days 100% 2 Total: Figure 1 For one level of shores and 2 levels of reshores, as shown in Figure 1, a construction rate of 1 floor per week, for the construction stage shown (casting of slab 4), determine for each slab: (3 points) (a) Slab age (b) Slab carrying capacity (based on relative strength and design load) (c) Applied load on each slab, including construction load at level 4 and slab weight at levels 1, 2 and 3 (d) Load to be supported by each slab, including its weight and its share of the construction load at level 4 (assume load at level 4 is distributed equally to the three interconnected slabs) (e) Load to be supported by shores/reshores (f) Required spacing between shores/reshores at each story (assuming maximum allowable load on each post is 3,000 lb, as in example 3). (g) Comparing carrying capacity (a) and load to be carried (c), conclude if for the planned construction rate, it is appropriate two levels of reshores. (Could it be just one level? Should the contractor use three levels of reshores instead?) (h) Determine how many days after casting slab 4, can the shores and forms be removed (Hint: compute carrying capacity at 3 days, 4 days, 5 days and 7 days and see when it is greater than D) Note: in your calculations you may use actual loads (psf = 1b/ft2) or factor of slab weight, D)
