Design Considerations during Construction

June 15, 2021
BLOG NEWS & TRENDS

OVERVIEW

 

There are cases where the design must be satisfied for two or more conditions for the same structure. In general, the design needs to be performed considering the load during construction and the load in use at the same time, as shown below. In this document, I will introduce how to perform two analyses simultaneously.

 

√ Page Contents

1. Modeling
2. Loading
3. The Setting of Boundary Condition
4. Running an Analysis
5. Running an Analysis: Checking Result-1
6. Running an Analysis: Checking Result-2
7. Running a Design
8. Combined Design Case
9. Running a Design: Checking Design Result

 


Case 1: During Construction

 

 

09_analysis case_case 1_1

Dead Load Slab (200mm) = 4.80kN/m2
Live Load

Vehicle load = 24.00kN/m2

* It is the value considered as an impact factor.

1.2DL + 1.6LL = 44.16kN/m2

 

 

 

Case 2: In Use

 

09_analysis case_case 2_2

Dead Load

Topping soil (900mm) = 16.20kN/m2

Slab (200mm) = 4.80kN/m2

Live Load

Landscape load = 5.00 kN/m2

*It is the value considered as an impact factor.

1.2DL + 1.6LL = 33.20kN/m2

 

 

 

 

 

Modeling

 

Step 1: Add & assign a member set.

 

 

09_analysis case_case_modeling step 1 & 2

1) Click 'Add Member Set'.

2) Add a new member set of 'Structure_01~02'.

 

09_analysis case_case_modeling step 33) Assign the base members to 'Structure_01' by Selecting the members and dragging in a model tree.

 

 

 

Step 2: Add jack support members & assign a member set.

 

 

09_analysis case_modeling step 2_1

09_analysis case_modeling step 2_2

1) Add the members of jack support in the model.

2) Select the members of jack support.

3)Assign the members of jack support to 'Structure_02' by dragging in a model tree.

 

 

 

Loading

 

Step 3: Create a slab load.

 

 

 

09_analysis case_modeling step 3_1-109_analysis case_modeling step 3_2

1) Define 'Static Load Set'.

2) Create 'Self-weight' of slabs.

3) Add a slab load for each case.

 

 

Step 4: Assign slab loads to slab members.

 

 

09_analysis case_modeling step 41) Run 'Slab Load'.

2) Assign the slab load for 'In Use' to slabs.

3) Assign the slab load for 'In Construction' to slabs.

 

 

Step 5: Create 'Support Set'.

 

09_analysis case_case_modeling step 5_1
09_analysis case_case_modeling step 5_2

 

1) Run 'Slab Lod'.

2) Assign the slab load for 'In Use' to slabs.

3) Assign the slab load for 'In Construction' to slabs.

 

 

 

The Setting of Boundary Condition

 

Step 6: Assign the support set to columns.

 

09_analysis case_case_modeling step 6-1

1) Run 'Ad Support' in the analysis tree.

2) Assign the support for 'In Use' to slabs at the bottom of RC columns.

3) Assign the support for 'In Construction' at bottom of jack supports members.

 

 

 

Running an Analysis

 

Step 7: Create an analysis case.

 

09_analysis case_case_modeling step 7_109_analysis case_case_modeling step 7_209_analysis case_case_modeling step 7_3

 * Select each applied member, load, and boundary condition to create an analysis case.

 

 

 

Running an Analysis: Checking Result-1

 

According to the load and boundary conditions, the results for each analysis case are different, as shown below.

 

09_analysis case_case_modeling step checking result_109_analysis case_case_modeling step checking result_2

 

 

Running an Analysis: Checking Result-2

 

 

09_analysis case_modeling checking result_1Case 1: During Construction

 

09_analysis case_modeling checking result_2

Case 2: In Use

 

09_analysis case_case_modeling step checking result_3

.

 

Running a Design

 

Step 8: Create design cases.

 

09_analysis case_case_running a design step9-1  Design Case 1: During Construction                                                         Design Case 2: In Use

 

09_analysis case_case_running a design step8_2

 

 

Combined Design Case

 

It performs the design considering both Design Case 1 and 2. 

 09_analysis case_case_running a design step8_3

1) Two design cases are crated according to each analysis case.

2) Create a combined case for two design cases.

 

 

 

Running  a Design: Checking Design Result

 

 Each design case has a different number of main rebars.

 

09_analysis case_case_modeling step checking design result_1

 

 

        Design result by 'During Construction'                                                 Design result by 'In Use'

09_analysis case_case_modeling step checking design result_2

                                                                                           Design result by 'During Construction'

09_analysis case_case_modeling step checking design result_3In the combined design case results, the reinforcement was recalculated considering the results for both design cases.

 

 

 

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About Author
Yeong-il Seo | Principal Structural Engineer

Young-il has over 13+ years of experience in building design, especially high-rise buildings with column reduction analysis, plant structures, pushover analysis, health monitoring, and vibration control projects. Since 2016, he is planning and providing technical supports for midas building products such as midas Gen, nGen, and Design+.

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