Masonry Building Strengthening in StatiCAD Program

Masonry Building Strengthening in StatiCAD Program

Types of Strengthening Available

1- Strengthening with shotcrete (sprayed concrete)
2- Strengthening by adding vertical tie columns to the system
3- Strengthening with fiber polymer (FRP) wrapping
4- Strengthening by adding new walls to the system

R, D, I coefficients for masonry buildings should be taken according to Section 11. However, the program applies the values entered by the user.

Calculations should be performed for DD-2 earthquake ground motion level, and the controlled damage performance target must be met. For school-type structures, a building importance factor of 1.5 is appropriate.

Wall safety factors should be taken as 1 since it is an existing structure.

Information collection from the building according to TBDY2018 is as follows:

15.2.10. Limited Knowledge Level for Masonry Buildings

15.2.10.1 – Building Geometry: If architectural drawings are available, visual inspection of the building will determine the conformity of the existing geometry with the drawings. If there are no architectural drawings, the system survey of the building will be obtained. The information obtained should include the location, lengths, thicknesses, openings of masonry walls on each floor, and story heights.

15.2.10.2 – Details: The type of roof and slab, connection details with walls, and the condition of tie beams and lintels will be visually determined.

15.2.10.3 – Material Properties: The type of wall materials will be visually identified by removing a portion of the plaster from the wall surface. Wall shear strengths given for each wall type in Section 11 will be used as the basis for building strength calculations.

15.2.11. Comprehensive Knowledge Level for Masonry Buildings

15.2.11.1 – Building Geometry: The system survey of the building will be prepared. The information obtained should include the location, lengths, thicknesses, openings of masonry walls on each floor, and story heights. The foundation system will be determined by an inspection pit to be opened from outside the building.

15.2.11.2 – Details: The type of roof and slab, connection details with walls, and the condition of tie beams and lintels will be visually examined. As a result of this examination, it will be determined whether the rigid diaphragm property is satisfied on each floor. If this property cannot be satisfied, it will be decided that the building is inadequate in terms of earthquake safety.

15.2.11.3 – Material Properties: The type of wall materials will be visually identified by removing a portion of the plaster from the wall surface. At least two wall piece samples will be taken from the building for determining wall material properties, and the average properties obtained from compression strength tests of these samples will be used in calculations according to Section 11.

Wall shear strengths given for each wall type in Section 11 will be used as the basis for building strength calculations.

1- Strengthening with Shotcrete

1.1 Steel mesh of the calculated class is placed on one or both surfaces of the wall. The steel meshes are anchored to the existing wall to ensure composite action. The wall is covered with shotcrete or repair mortar of the calculated thickness providing the design strength.

For the strengthening to be considered in StatiCAD calculations, TBDY2018 regulation must be selected on the regulation selection page in the project general settings, and the option "This project is for Examination and Strengthening of an Existing Building" must be checked. If RYTEiE 2019 (Risky Building) regulation is selected or if the "This project is for Examination and Strengthening of an Existing Building" option is not checked, strengthening will not be considered.

In Project General Settings > Strengthening Tab, options 1, 2, and 4 are selected.

Option 1: If not selected, strengthening will not be considered.

Option 2: Enables consideration of the contribution of strengthening to compression capacity. May be left unchecked if wall compression strength is adequate.

Option 3: In wall strengthening, the shear capacity increase is calculated assuming only the shotcrete shear strength contributes and the reinforcement is placed constructively. Not recommended as it is excessively conservative and uneconomical, but can be applied at the engineer's discretion.

Option 4: When selected, the shear strength of shotcrete is not calculated; only the shear strength from the steel mesh reinforcement is considered. In our opinion, this is an economical and safe solution. In this option, the additional shear strength provided by the mesh reinforcement (to prevent brittle failure) is limited to 0.22*fcd*Ajacket. If the shear strength of the strengthened wall is still insufficient, increasing the shotcrete class or jacket thickness may be a solution to achieve adequate performance from strengthening as required by the formula.

Strengthening Jacket (Shotcrete) Drawing

For composite (jacket-inclusive) capacities of walls to be calculated in strengthening, the strengthening jacket must be modeled from the static axis passing through the center of the wall. The start and end nodes of each wall segment and jacket segment must be the same. If this is applied, the jacket carries load from the floor in proportion to its stiffness and calculates reinforcement for the insufficient capacity portion of the wall.

If the wall start and end points are defined differently from the jacket start and end points, the jacket only carries load from the floor and does not take additional load from the wall it is attached to. Reinforcement calculation is done based on the load taken from the floor.

The strengthening jacket term used in the program refers to strengthening by creating a reinforced concrete layer where steel mesh is placed on the wall and anchored to it, applied with shotcrete or repair mortar.

To draw a strengthening jacket, press the button on the main screen to bring up the Wall Strengthening Jacket Properties input form.

In the form, the jacket name is automatically assigned by the program and does not need to be changed. The wall thickness to be jacketed is entered in cm. The wall and jacket eccentricity value is kept at zero. The jacket left/bottom extension length determines how many cm the jacket extends to the left or bottom from the clicked point. The jacket right/top extension length determines how many cm the jacket extends to the right or top from the clicked point. The concrete jacket thickness is entered. If the building is not stepped or if the wall bottom-top elevation values are zero, the concrete jacket bottom and top elevations should also be left at zero.

If the upper or left face of the wall is to be covered, the Upper/Left face covering radio button is selected. If the right or lower face is to be covered, the Lower/Right face radio button is selected.

When walls are fully jacketed from end to end, the program can calculate the required reinforcement for the jacket. If custom values are desired, one of the available steel mesh options can be used.

After exiting with the OK button, the jacket is drawn by clicking the first and second points on the wall axis to be jacketed.

Drawing Strengthening Jackets

1. For composite (jacket-inclusive) capacities of walls to be calculated in strengthening, strengthening jackets and walls must be defined from the same axis.
2. There is no need to change the Jacket Name in Wall Strengthening Jacket Properties. The program assigns element names automatically; if elements drawn in mixed order need to be sorted, the sort button on the upper toolbar can be used for automatic sorting.
3. The wall thickness value is entered in the wall thickness to be jacketed box.
4. For exterior wall jackets, the jacket left/bottom extension length can be set to half the thickness of the wall perpendicular to the wall being jacketed. The left/bottom extension determines how far beyond or before the defined left/bottom axis the jacket will be drawn. Positive or negative values can be entered.
5. For interior wall jackets, the jacket left/bottom extension length can be set to the negative of half the thickness of the perpendicular wall (e.g., -10). The left/bottom extension determines how far beyond or before the defined left/bottom axis the jacket will be drawn.
6. For the jacket right/top extension definition, refer to items (4) and (5).
7. The concrete jacket thickness must be at least 3 cm as required by the earthquake code. When static calculations are performed considering the jacket stiffness, the jacket thickness is one of the factors in determining the seismic load the jackets will carry.
8. Bottom Elevation: If the floor you are modeling is a basement and your building is stepped, you can set the jacket bottom elevation equal to the wall bottom elevation.
9. Top Elevation: If the floor you are modeling is the top floor and your building is stepped, you can set the jacket top elevation equal to the wall top elevation. If the jacket bottom or top elevation differs from the wall bottom or top elevation, analysis results may deviate from expected results.
10. In building applications, setting the jacket bottom or top elevation differently from the wall bottom or top elevation may reduce the seismic performance of your building.
11. To cover the left face of vertical walls or the upper face of horizontal walls, activate the upper/left face covering option.
12. To cover the right face of vertical walls or the lower face of horizontal walls, activate the lower/right face covering option.
13. Click the OK button and click on the axis intersection points on the main modeling screen to mark the first and second ends of the jacket. The jacket will be drawn.
14. If you want to consider the contribution of strengthening jackets to wall compression safety stresses or calculate the contribution of strengthening jackets to wall shear capacity, the start and end points of exterior wall jackets must be equal to or greater than the wall start or end points (from the formula definition).
15. Similarly, for interior wall jackets, the start and end points must be equal to or greater than the wall start or end points.

On the screen and in drawings, the jacket will be drawn at the intersection of the jacket and wall (the intersection area of the jacket and perpendicular wall), resulting in some excess in jacket stiffness for the wall intersection area. However, this is taken into account in the analysis; jacket areas are reduced by the intersection area, so no difference occurs in calculations. In drawings, it is appropriate to additionally trim (cut, erase) the jacket line at the wall-jacket intersection.

When a wall jacket is drawn to cover a door or window opening, the jackets are automatically divided by the door or window openings, and constructive jackets are automatically created.

A constructive strengthening jacket is the continuation of the jacket on wall segments above and below windows or above doors. Continuing the jacket at door or window openings increases the stiffness of solid wall segment jackets and provides better strengthening for the building. When drawing strengthening jackets, constructive jackets are automatically created by the program at door or window sections, and their properties can be modified by the user through this form.

Jacket Reinforcement

If you want to use the same type of reinforcement for all jackets in the building, first select "Program automatic selection" in the reinforcement selection tab of the jacket properties window. After analysis, to apply the maximum jacket reinforcement selected by the program to all jackets, select all jackets floor by floor (using the "Change properties of selected jackets" option), and in the reinforcement selection tab of the jacket properties window, the maximum calculated steel mesh can be assigned to all jackets.

In calculation reports, finding a mesh class larger than Q785/785 steel mesh indicates that the required reinforcement area cannot be provided with standard steel meshes. For example, if Q1234/1234 mesh is calculated, it means 12.34 cm2/m horizontal and vertical reinforcement is needed in that jacket.

In such cases, 2 layers of Q634 reinforcement can be used inside the jacket thickness (2*634>1234), or if single-row 12 mm diameter ribbed reinforcement is to be used, spacing = 100/(12.34/(1.2*1.2*pi()/4)) = 9 cm, or if double-row 12 mm diameter ribbed reinforcement is to be used, spacing = 2*100/(12.34/(1.2*1.2*pi()/4)) = 18 cm.

2- Strengthening by Adding Vertical Tie Columns to Insufficient Walls

Checking the option shown above enables the application of the following regulation article in the program. When the "Include vertical tie columns in wall strength" option is checked, insufficient walls can become adequate when vertical tie columns of sufficient cross-section are added inside the wall.

3- Strengthening with Fiber Polymer (FRP) Wrapping

Insufficient walls are selected, right-clicked, and the "Change selected wall properties" option is clicked.

In the wall properties window, go to the FRP Wrapping tab and select "Apply horizontal strip fiber polymer wrapping" and/or "Apply diagonal fiber polymer between wall corners" option.

The values related to the material planned for application are entered in the boxes and the OK button is pressed.

After analysis, check whether the wall has become adequate. If not, repeat the analysis by changing the number of FRP wrapping layers on one face, the number of covered surfaces (1 or 2 faces of the wall), the center-to-center spacing of FRP strips, the width of FRP strips, or the material type/quality.

Static results can be checked from the wall shear stress report.

In the table above, Wall shear strength (Vrd) is found by adding Vfy+Vfc values to the smaller of Vrd1a and Vrd1b values for each loading:

Vrd = min(Vrd1a, Vrd1b) + Vfy + Vfc

Drawings can be obtained from the drawing selection window.

Foundations

Since the regulation does not specify the effect of foundation inadequacies on the building in performance calculations, the program does not change the performance status of the building due to foundation inadequacies. However, if there are foundation inadequacies (checked from foundation reports), analyses are performed by changing the foundation cross-section dimensions until they are adequate, and strengthening drawings for the new adequate foundation dimensions are separately prepared by the user. Prof. Zekai Celep's Introduction to Earthquake Engineering book can be used as a reference for drawings.