BILD 322 Assignment 2B

Assignment 2B is an individual assignment.

Your task is to submit a structural strengthening report for the earthquake prone building selected in  stage 1.

You will analyse the selected building structure from the perspective of gravity and lateral loadings  and recommend a strengthening strategy to achieve 100% compliance with the New Building  Standard (%NBS).

The Stage 2 report is due on Friday 2^rd October 9 pm to Nuku.

Stage 2 is an individual assignment and is worth 50% of the course grade.

For Stage 2, assume your building is to be strengthened to 100% of New Building Standard (%NBS).  Submit a professional report which describes your strengthening strategy. This report should be no longer  than 2500 words and include references, images, image annotations and titles, and appendices, etc. Your report will include the following sections and an appendix with two RESIST reports.

Details of each section include:  

1. Cover page

a) Report title

b) A representative image or drawing of your building

c) Your full name and student ID

2. Executive Summary (1 to 3 paragraphs) Briefly summarise:

a) Building name and location.

b) Existing structural system and current earthquake performance.

c) Design criteria: soil type and terrain type.

d) Key points of your proposed strengthening strategy.

3. Existing Structure: Systems and Behaviour

Purpose: identify how the current building resists gravity and lateral loads and what current  deficiencies exist.

a) Structural System Description

o Describe the primary structural systems for both gravity and lateral load resistance.

o Use any relevant annotated plans, sections, and/or elevations to show:
▪ All primary vertical and lateral load-resisting elements
▪ Gravity load paths
▪ Centre of Mass (CoM) and Centre of Rigidity/Resistance (CoR) on the ground  floor plan

b) Appraisal of the Current Strength

o Describe the potential strength of the current building (using the RESIST analysis of the  existing building’s structure). Concentrate on the existing structural systems and include  discussion of any current deficiencies and potential weaknesses.

c) Torsion and Diaphragm Action

o Show how the building may twist under seismic loading (use diagrams).

o Explain how torsion is resisted by the current system.

o Describe using diagrams how the first-floor diaphragm behaves, including:
▪ Earthquake forces acting on the diaphragm and how those forces are transferred  and resisted (use diagrams)
▪ Presenting shear force and bending moment diagrams for the diaphragm  (approach the diaphragm as a horizontal beam supported by the lateral structure)

4. Proposed Strengthening Strategy

Purpose: Present and justify a comprehensive retrofit approach.

a) Explain the proposed structural systems in each direction and why you have selected your strengthening strategy.

b) Discuss any need for a change in stiffness (e.g. adding/removing elements, cutting wall gaps), either in the existing structure or via the addition of new systems.

c) Describe critical detailing changes (connections, materials) that enhance strength/stiffness.

Explain how these details ensure the intended seismic response.

5. RESIST Evaluation of Strengthened Structure

a) Provide a brief reflection on any assumptions or limitations that have been made to accommodate your seismic retrofit design on RESIST.

b) Explain the RESIST report of the seismically retrofitted building.

c) Comment on any differences between your expectations and RESIST output.

6. Appendix

Include a RESIST report on the current strength of the building (pre-strengthening). Include a RESIST report on the strength of your proposed and strengthened building.

Marks for Assignment 2b will be graded on: 

1. The presentation (10%)

2. Executive summary (10%)

3. Existing Structure: Systems and Behaviour (25%)

4. Proposed Strengthening Strategy (35%)

5. RESIST Evaluation of Strengthened Structure (20%)

RESIST Modelling tips: 

Ensure the RESIST reports contains a reasonably sized image of your structure by using RESIST’s ‘set  image’ feature by right clicking on the image once you have selected the view you want and choosing the  menu option “set image for report”.

In your RESIST analysis of existing structure, you must take into account the lower strength of existing  shear walls and frames as follows:

• Brick masonry, assume the length is 10% of the actual length and model as reinforced concrete masonry (note that in doing this the building weight will be underestimated).
• Concrete shear walls, assume the length is 40% of the actual length and model as reinforced
• If you have a concrete moment resisting frame building with poor shear reinforcing, assume columns and beams are half the actual depth.

If your building has multiple structure types in one direction, model each one in RESIST separately,  assuming all elements in that direction are the same as the ones you are modelling. If your building has  wings, that is L or T shaped, then model each wing separately. If your building has part floors (for example  a large auditorium with galleries and concourses), then the most conservative option is to ignore part floors.  Remember that RESIST is a preliminary design tool and will only give an indication of an existing  building’s strength. It gives results as load/capacity which is the inverse of %NBS which is capacity/load. So  in your final RESIST analysis you need to be aiming for 100% or just under in the RESIST results chart.