PART 2-SETTING UP DESIGN CRITERIA

Part 2 of design of building using staad and excel. Setting up the design criteria using a spreadsheet. Note that design criteria must be consistent with design drawings and design specifications.

PART 1- STAAD MODELING OF BUILDING

This is a sample staad modeling of 4 storey building. There are many easy ways to model building in staad and its in this video.

COLUMN INTERACTION DIAGRAM

In the design and investigation of concrete column, interaction diagram is required. This is a plot of Axial load, P capacity versus Moment, M capacity in a certain axis of the column.

The image below shows an interaction diagram indicating Nominal capacity and Ultimate capacity of the concrete column. The single dot is the specified load required in the column from the structural analysis. The load required plot should be inside the interaction diagram curve. Note that the interaction diagram is a work in progress to date.

This is the overview of the spreadsheet.

The user will only input on the following yellow filled cells:
1. b = width of the column along x axis
2. h= height of column along y axis
3. cover = extreme tension layer distance from center to outermost cover of column
4. As1= area of single rebar used in both extreme tension layer and compression layer, 3= number of rebar in both extreme tension and compression layer
5. effective depth from outermost compression concrete to extreme tension layer
6. As2 = area of single rebar in zone 2, 2=number of rebar in zone 2, 249= effective distance of zone 2 rebar to extreme compression concrete, As3=area of single rebar in zone 3, 2=number of rebar in zone 3, 491= effective distance of zone 3 rebar to extreme compression concrete..
7. fy= rebar yield strength
8.fc = concrete compressive strength

After inputting all those values, an interaction diagram is generated for up to 5 layers of rebar in a concrete column. The corresponding Pu and Mu required is also plotted if you input them.

Having this kind of spreadsheet will allow you to easily investigate the column for a number of load combinations of P and M from dead load, live load and earthquake load. Also, changing the parameters like rebar area, depth of each zone of rebar and number of rebars in each zone are easier compared to doing it in manual calculation.

The video below shows verification of result for 4 rows of rebar in column.

The video below shows a verification of result from interaction diagram.

This video shows how to input actual column rebar layout from column schedule and investigating the capacity from set of load forces from different load combinations:

Reinforced Concrete Design Laboratory

To ensure that students will learn how to design in a proper sequence and with task to finish on time, a monitoring checklist is required. See below for sample checklist I used..

As you observe, architectural plans should be submitted first followed by the Structural Plans. From the structural plans, students should be able to look for the design criteria and encode in the spreadsheet. Most of the values here are obtained from the General Notes or first sheet of the Structural Plan. They will then refer to NSCP 2010 to verify the values and set constant parameters like the following:

1. Beta factor of concrete from assumed Fc'
2. minimum reinforcement ratio from assumed fy and fc'
3. maximum reinforcement ratio

From structural plans, loading distribution plan and loading designation plan should be generated. This exercise will help student realize on loading effects on members and will determine by inspection which girder or beam will carry the most load.

There will be four major loading criteria for student to analyse:

1. Dead Load
2. Live Load
3. Wind Load
4. Earthquake Load

Gravity loads like Dead Load and Live load will be analyzed by Moment Distribution Method while Wind Load and Earthquake load by Factor Method.

Loading combinations are then post processed after analysis to obtain the Governing load combinations to be used in Design of Elements.

Girder Design In Accordance with Earthquake Provision

For a SMRF(special moment resisting frame) system, the earthquake lateral force is primarily resisted by girders and columns. Thus, they must be designed in consideration of earthquake provision in the code.

If you are new to earthquake code per ACI or NSCP, this spreadsheet has Notes beside the formulas to let you know what section it is located in the code. Thus, this helps in guiding you what important provision is really used in the code and you avoid reading too much unnecessary provisions.

Again, green values are linked from the Design Criteria tab. You just need to input(red fonts) the STAAD member forces and this spreadsheet will give you:

• required top and bottom bars
• hoops spacing from shear forces
• stiffener requirement
• and verification of section of beam assumed

Seismic Isolation for Designers and Structural Engineers

For an earthquake prone country, designing of buildings are approached using structurally advanced technology. One of these is seismic isolation. This book "Seismic Isolation for Designers and Structural Engineers" provides both theory and design aspects of seismic isolation.

Mr. Kelly has over thirty years professional experience in the design and analysis of a variety
of structures, with particular emphasis on the non-linear response of structures to seismic
loading, the earthquake evaluation of existing buildings and the application of base isolation
and energy dissipation techniques to a variety of structural types.

Japan which is also an earthquake prone country uses this technology and they were able to resist several earthquakes in the past. Truly, this book is a good reference.

Pilecap Design using STAAD FEM features

This video shows quickly how to design pilecap using staad fem analysis..