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Overview and purpose

This test problem demonstrates the formulation of staged-construction analysis, as applied using various modeling procedures. Time-dependent behavior is considered, new joints are placed within deformed and undeformed locations, and a description of how users may interpret output is included.

A five-story column is modeled with five construction stages which ascend vertically. At each stage, a frame object is assigned to represent a 3.7m column segment. A load of 500kN is applied in the gravity direction at the top of each segment. Five load cases are defined to illustrate the process and to evaluate construction scenario. These load cases include:

• LOAD: new joints placed in undeformed position; load applied without considering creep.

• (DEF) LOAD: new joints placed in deformed position using the ghost structure concept; load applied without considering creep.

• LOAD+CR: new joints placed in undeformed position; load applied and creep is considered.

• (DEF1) LOAD+CR: new joints placed in deformed position using a ghost structure with change modifiers; load applied and creep is considered.

{{Test Problem

Overview and Purpose

The purpose of this test problem is to illustrate how stage construction is handled in SAP2000 and how various aspects of stage construction (such as placing new joints to deformed or undeformed location; considering time dependent behavior) can be modeled and how to interpret the results.

The model consists of a 5-story column that is constructed in 5 stages, from the bottom up. In each stage, a frame member representing a 3.7 m long segment of the column is added and a load of 500 kN is applied to the top of the segment in gravity direction. The following 5 load cases were setup to evaluate different construction scenarios and to illustrate how SAP2000 handles the staged construction definition:

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• (DEF2) LOAD+CR:

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• new joints placed in

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• deformed position using a parallel ghost structure with change modifiers; load applied and creep is considered.

Each load case is described more fully in the sections below. Further, the attached PDF provides additional , remove structure and add structure operations, apply load and consider creepPlease refer to the sections below for a more detailed description of each load case. Also refer to the attached PDF file with illustrative sketches. Results for each load case were are independently verified by the spreadsheet calculations , please see in the attached Excel filesfile.

Sketch of Model and Staged Construction Sequence

(Please see the attached PDF file for a high resolution of the below sketch.)

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Summary of SAP2000 Deflections

(See the attached Excel file for a full resolution image.)

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Discussion of Modeling and Results for Individual Load Cases

LOAD

Modeling and staged-construction sequences

A sketch of the construction sequence and associated loading is presented in Figure 1:

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Figure 1 - Column model and sequence

A high resolution image of Figure 1 is presented in the attached PDF .

Summary of deflection results

Analysis generates the deflection results which follow:

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Figure 2 - Deflection summary

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Figure 3 - Graph of final joint deflections

A full resolution image of Figure 2 is attached in the Excel spreadsheet .

Discussion of modeling and results for individual load cases

Modeling and results for individual load cases are discussed as follows:

LOAD

• Following the default procedure, newly added joints are placed in undeformed locations. This corresponds to a situation in which concrete is cast-in-place Newly added joints are placed in undeformed location (this is the default way SAP2000 handles construction stage analysis). This would correspond to a situation when cast-in-place concrete is placed up to the desired elevation.

• Creep is not consider by keeping "Time Leaving the Time-Dependent Material Properties " option unchecked on in the Nonlinear Parameters formmenu keeps creep from being considered in analysis.

• In each construction stage, one story is added, and then loaded.

(DEF) LOAD

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- using ghost structure

• An auxiliary ghost structure is used to add new joints to deformed locations. This is a manual staged-construction process which requires Newly added joints are placed in deformed location by using an auxiliary ghost structure (this is not the default way SAP2000 handles staged construction and it requires some additional stages to setup and utilize the ghost structure.). This would correspond to a situation precast segments of the column with a fixed length are being method may be applicable when fixed-length precast-column segments are erected one by one.

• Creep is not considered.

• Staged construction consists of the following stages:
  
  
  • The To create the ghost structure, the entire structure is first added.
  • Frame property modifiers equal to 0.0001 are applied to the entire structure to make it very flexible - this is the ghost structure.
  • Stories are added one-by-one in the subsequent stages by first first assigning unit property modifiers to the story that is being erected (this . This effectively assigns the actual stiffness and activates the member ) and then before load is then applied.

LOAD+CR

• Newly added joints are placed in undeformed locationlocations.

• Creep is considered.

• Construction stages are similar as for to those of the " LOAD " load case. Note than Please note that nonzero stage duration of the stages causes creep deformation.

(

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DEF1) LOAD+CR - using ghost structure

• Newly added joints are placed in deformed locationlocations.

• Creep is considered.

• The Construction stages of the staged construction are similar to those of the " (DEF) LOAD " load case, but nonzero stage duration of the stages leads to creep deformation in this case.

• Note Please note that the *age of all elements is counted from the time when the entire (ghost) structure was is added in the first step. This The upper-story columns are activated, by changing their modifiers from GHOST to FULL, at an older age than the lower-story columns. This may underestimate the creep deformation when compared to the case when all in which all members are activated at the same (young) age , say 7 of seven days.

(DEF2) LOAD+CR - using parallel ghost structure

• Newly added joints are placed in deformed locationlocations.

• Creep is considered.

• The staged Staged construction was is slightly modified from the " (DEFDEF1) LOAD+CR " load case to model *all elements being activated at the age of 7 seven days. The modification involved removing and then adding members with the age of 7 days prior to activating the members by changing their property modifiers from 0.0001 to 1.

See Also

• List of creep resources
• List of staged construction resources
• Staged construction in buildings

Attachments

• This is achieved by first adding the entire ghost structure and then by then adding the real structure, story-by-story, with an actual age of seven days.

• Another approach which simulates the activation of elements at the age of seven days is to remove the ghost elements and then add the real elements in a subsequent stage. This procedure is illustrated in the DEF3 LOAD+CR load case within the model.

See Also

• Staged construction in buildings test problem

Attachments

• SAP2000 V18.0.1 model (zipped SDB file)

• File | filename = Staged construction for 5-story column - hand calculations and sketches.pdf | title = Hand calculations and sketches (PDF File)File | filename = Staged construction for 5-story column - verification using spreadsheet.zip | title =

• Spreadsheet calculations to verify SAP2000 results (Zipped zipped Excel file)

• File | filename = Staged construction for 5-story column - analysis log.zip | title = Tabulated summary of SAP2000 results (Zipped Excel file)File | filename = Staged construction for 5-story column - SAP2000 V12.0.2 file.zip | title = SAP2000 V12.0.2 file (Zipped SDB Filezipped Excel file)