The$Simpliﬁed$Method$of$Shoring/Reshoring$ · PDF...

The Simplified Method of Shoring/Reshoring

•  Some field measurements of loads suggest that the simplified method is accurate enough for prac9cal use. Other theore9cal studies consider variable s9ffness of the shores, or aspects of the slab-‐shore interac9on. Some recommend a correc9on factor of 5-‐15 percent to be used when using compressible shores – CommiFee 347 is preparing a report.

•  Assump9on when using the Simplified Method 1.  All Slabs are iden9cal – and shores/reshores are aligned one-‐on-‐one from floor to floor 2.  Ground level is rigid, and shores are spaced closely enough to treat the shore reac9ons as

a distributed load. 3.  Shores and reshores are infinitely s9ff rela9ve to the slab. 4.  Slabs interconnected by shores all deflect equally when a new load is added, and carry a

share of the load in propor9on to their rela9ve s9ffness

SLAB 1 SLAB 1 SLAB 1

0 0

Step 1: Place level 1 concrete

0 1D

0 1D

0 2D

1D 0

1D 0

1D 0

1D 0

1D 0

1D 0

0 1D

1D 1D

1D 1D

.5D

.5D

1.5D 0

1D 0

Step 2: Place level 2 concrete Step 3: Remove shoring 1

Step 4: Re-‐shoring 1


SLAB 2


SLAB 2 SLAB 2

SLAB 2 SLAB 2

SLAB 3 SLAB 3

Shoring/Reshoring: Simplified Analysis of Loads: Two levels of shoring, one level of re-‐shoring

½ load

½ load

full load

full load

OG load -‐1/2 transferred

References: Formwork for Concrete – Special Publica9on #4 Seventh Ed As per OSHA standards: Removal of the forms and shores should be specified by the engineer-‐architect for most major structures during construc9on.

Notes: once slab one is placed all load is transferred to the shoring

Notes: Slab 2 is placed, all load is transferred to the shoring 2, then load is transferred to shoring 1 because slab 1 can’t take load because the shoring doesn’t allow.

Notes: When shoring is removed both slab 1 and slab 2 deflect together allowing both to absorb there own weight

Notes: No change when reshoring is placed Notes: New slab is placed all the weight is transferred down through the shoring and reshoring

Notes: When you take away shoring 2 a major shia happens, half of the load that was carried by shoring 2 is shiaed to slab 3 and the other half is shiaed to slab 2. Shoring 3 is now carrying less of the load.


SLAB 1

SLAB 2

.5D

.5D

1.5D 0

1D 0

0 1D

.83 1.17D

1.83D .34

1.34D 0

.59D

.41D

1.41D 0

1D 0

1D 0

0 1D

.92D 1.08D

1.74D .34D

1.34D 0

1D 0

Step 7: Place level 4 concrete, Reshore 2 with level 1 Step 8: Remove shoring 3

Step 10: Remove shoring 4

Step11: Place level 6 concrete, Reshore 4 with level 3

SLAB 2

SLAB 3

SLAB 4

SLAB 3

SLAB 2

SLAB 4 SLAB 4

SLAB 3

SLAB 2

Step 9: Place level 5 concrete, Reshore 3 with level 2

0 1D

.92D 1.08D

1.74D .34D

1.34D 0

1D 0

.54D

.46D

1.46D 0

1D 0

1D 0

1D 0

0 1D

.87D 1.13D

1.79D .34

1.34D 0

1D 0

1D 0

SLAB 1

SLAB 3 SLAB 3

SLAB 2

SLAB 4

SLAB 5

SLAB 4

SLAB 5

SLAB 6

SLAB 5

1/3 load

1/3 load

1/3 load

Load -‐1

/3 load

2/3 Load -‐1

/3 load

½ load

½ load

1/3 load

1/3 load

Load -‐1

/3 load

2/3 Load -‐1

/3 load

1/3 load

1/3 load

Load -‐1

/3 load

2/3 Load -‐1

/3 load

1/3 load ½ load

½ load



Notes: Now when a new slab is placed the load is shared among the other three slabs. This is high load impact on. Look at how much weight slab 2 has to carry.

Notes: Same method as step 6 Notes: Same method as step 7

Notes: Same method as step 7 Notes: Same method as step 6

Legend

Newly placed concrete slab

Fully cured concrete slab

Deflec9on of concrete is occurring

Transfer of load is occuring


0 0

Step 1: Place level 1 concrete

0 1.6D

0 1.6D

0 2.7D

1.05D 0.05D

1.05D 0

1D 0.05D

1D 0

1D 0.05D

1D 0

0 1.6D

1.05D 1.6D

1.05D 1.6D

.52D

.58D

1.58D 0

1D 0


Step 4: Re-‐shoring 1


SLAB 2


SLAB 2 SLAB 2

SLAB 2 SLAB 2

SLAB 3 SLAB 3

Shoring/Reshoring: Simplified Analysis of Loads: One levels of shoring, two level of re-‐shoring, assuming Construc9on Live loads(.5D) and shores and forms weigh(.1D)

½ load

½ load(1.05D)

full load

full load


References: Formwork for Concrete – Special Publica9on #4 Seventh Ed As per OSHA standards: Removal of the forms and shores should be specified by the engineer-‐architect for most major structures during construc9on.

Notes: once slab one is placed all load is transferred to the shoring

Notes: Slab 2 is placed, all load is transferred to the shoring 2, then load is transferred to shoring 1 because slab 1 can’t take load because the shoring doesn’t allow. Slab two has construc9on live load(CLL) and shores and forms weigh(SFW), slab just has SFW

Notes: When shoring is removed both slab 1 and slab 2 deflect together allowing both to absorb equally the remaining weight, which is just the self weight plus SFW of slab 2

Notes: No change when reshoring is placed Notes: New slab is placed all the weight is transferred down through the shoring and reshoring

Notes: When you take away shoring 2 a major shia happens, half of the load that was carried by shoring 2 is shiaed to slab 3 and the other half is shiaed to slab 2. Shoring 3 is now carrying less of the load. Also assume no CLL and only formwork on slab 3.


SLAB 1

SLAB 2

.52D

.58D

1.58D 0

1D 0

0 1.6D

1.05 1.65D

2.11D .54D

1.54D 0

.6D

.50D

1.5D 0

1D 0

1D 0

0 1.6D

1.13D 1.57D

2.03D .54D

1.54D 0

1D 0

Step 7: Place level 4 concrete, Reshore 2 with level 1 Step 8: Remove shoring 3

Step 10: Remove shoring 4

Step11: Place level 6 concrete, Reshore 4 with level 3

SLAB 2

SLAB 3

SLAB 4

SLAB 3

SLAB 2

SLAB 4 SLAB 4

SLAB 3

SLAB 2

Step 9: Place level 5 concrete, Reshore 3 with level 2

0 1.6D

1.13D 1.57D

2.03D .54D

1.54D 0

1D 0

.56D

.54D

1.54D 0

1D 0

1D 0

1D 0

0 1.6D

1.09D 1.61D

2.07D .54

1.54D 0

1D 0

1D 0

SLAB 1

SLAB 3 SLAB 3

SLAB 2

SLAB 4

SLAB 5

SLAB 4

SLAB 5

SLAB 6

SLAB 5

1/3 load

1/3 load

1/3 load

Load -‐1

/3 load

2/3 Load -‐1

/3 load

½ load

½ load

1/3 load

1/3 load

Load -‐1

/3 load

2/3 Load -‐1

/3 load

1/3 load

1/3 load

Load -‐1

/3 load

2/3 Load -‐1

/3 load

1/3 load ½ load

½ load



Notes: Now when a new slab is placed the load is shared among the other three slabs. This is high load impact on. Look at how much weight slab 2 has to carry.

Notes: Same method as step 6. No CLL Notes: Same method as step 7

Notes: Same method as step 7 Notes: Same method as step 6, CLL is assumed removed

Legend

Newly placed concrete slab

Fully cured concrete slab

Deflec9on of concrete is occurring

Transfer of load is occuring

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