Assessment of Existing Concrete Buildings after Vertical Addition

In Assessment of Existing Concrete Buildings after Vertical Addition, you'll learn ...

• The assessment process for existing reinforced concrete buildings following vertical additions.
• The evaluation of structural load path changes, transfer girder behavior, and foundation performance.
• The interpretation of structural distress using field observations, testing, and analytical modeling.
• How to develop safe and defensible rehabilitation strategies for modified concrete buildings.

Overview

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Credit: 6 PDH

Length: 94 pages

What happens when an existing reinforced concrete building is vertically expanded, its original structural role changes, and the modified load path begins to show signs of distress?

This course presents a real-world structural assessment involving an aging reinforced concrete building originally designed for workshop use. The building was later modified by removing its original roof, constructing a new slab-and-beam floor system, and placing new columns over existing long-span frame girders.

What initially appeared to be a straightforward vertical addition created a complex structural safety problem involving altered load paths, unintended transfer girder behavior, excessive deflection and cracking, questionable added supports, foundation overstress, corrosion, settlement, and seismic vulnerability.

The course provides a practical, forensic-style examination of how professional engineers evaluate existing concrete buildings after major structural modifications. Developed from an actual assessment performed by the presenting structural consultant, it combines analytical evaluation and code-based checks with the engineering judgment required to interpret distress, test assumptions, verify load paths, assess foundation reliability, and develop defensible recommendations that protect public safety.

Participants are guided through the full assessment process, including field observations, material testing, structural surveys, distress interpretation, staged-construction modeling, demand-capacity evaluation, serviceability checks, foundation reevaluation, assessment of added supports, and development of final safety recommendations.

Particular emphasis is placed on tracing the complete load path from the added floor and planted columns through the existing girders, columns, lower supports, foundations, and supporting soil. The course demonstrates why strengthening individual members or adding supports does not necessarily make a modified structure safe unless the capacity, stiffness, connections, contact conditions, and foundations of the entire system have been verified. The case study also illustrates why the safest rehabilitation strategy may sometimes involve removing unsafe added loads, reducing seismic mass, restoring a more reliable load path, and strengthening only those elements that continue to require intervention.

This course is intended for professional engineers involved in existing-building evaluation, renovation, adaptive reuse, vertical additions, structural rehabilitation, repair design, forensic assessment, and peer review. By the end of the course, participants will have a practical framework for evaluating modified concrete buildings and making sound engineering decisions concerning structural safety, use restrictions, load removal, strengthening, repair, monitoring, foundation improvements, and final reporting.

Specific Knowledge or Skill Obtained

This course teaches the following specific knowledge and skills:

• Why vertical additions to existing concrete buildings can create serious structural safety risks when the original load path, member capacity, foundation system, and occupancy assumptions are not fully re-evaluated.
• How a seemingly simple building modification can transform existing long-span frame girders into unintended transfer girders carrying concentrated column loads.
• Key distress indicators in existing concrete buildings, including excessive deflection, flexural and shear cracking, beam-column joint distress, corrosion, settlement, tilt, and foundation-related movement.
• How field observations, material testing, structural surveys, soil investigations, and monitoring data should be integrated into a defensible structural assessment.
• A structured assessment approach using staged-construction analysis, field-calibrated modeling assumptions, and sensitivity studies to compare the original building condition, the modified condition after vertical addition, the current distressed condition, and the proposed strengthened or load-reduced condition.
• Assessment of distressed reinforced concrete frame girders for flexure, shear, local effects under planted columns, serviceability deflection, and cracking after a change in structural role.
• Why added lower supports, temporary columns, or retrofit measures may not be reliable unless their contact condition, stiffness, connection behavior, axial capacity, and foundation support are verified.
• The importance of tracing the complete load path from the added floor and planted columns through girders, columns, lower supports, foundations, and soil.
• When a strengthening strategy may be unsafe or inefficient if it attempts to reinforce an overloaded and unreliable structural system without first reducing or removing unsafe added loads.
• How foundation re-evaluation can control the final engineering decision, even when upper structural elements appear to be repairable or strengthenable.
• Load removal, load reduction, localized strengthening, foundation enlargement, corrosion repair, and monitoring as part of an integrated rehabilitation strategy.
• Practical engineering recommendations for existing concrete buildings after vertical additions, including safety classification, use restrictions, monitoring requirements, repair priorities, and final reporting.

Certificate of Completion

You will be able to immediately print a certificate of completion after passing a multiple-choice quiz consisting of 40 questions. PDH credits are not awarded until the course is completed and quiz is passed.