What is Strengthening and Retrofit Design?

In the building inspection industry, Strengthening and Retrofit Design follows a rigorous process based on initial inspection and assessment, followed by strengthening, design, and construction. Inspection work is the foundation and prerequisite for strengthening design, aiming to comprehensively understand the building's current condition, identify safety hazards, and provide reliable technical basis for subsequent design.

Core Process

• Data Collection and On-site Investigation: Collect original design drawings, construction documents, geological survey reports, etc. Conduct a detailed investigation of the building's historical use changes and damage.

• On-site Inspection and Structural Assessment: Employ various professional technical methods to systematically inspect the performance of building materials (such as concrete strength, steel corrosion), component dimensions, connection conditions, and overall structural defects (such as cracks, deformation, corrosion).

• Common Inspection Methods: Including rebound method, ultrasonic method, core drilling method, non-destructive testing, etc.

• Preparation of Inspection and Assessment Report: Based on on-site inspection and laboratory test results, prepare a formal assessment report, evaluating the safety, seismic resistance, and durability level of the building structure.

• Development of Strengthening and Retrofit Plan: Based on the problems identified in the assessment report and the current functional requirements of the building, develop a detailed strengthening and retrofit plan, including plan comparison and optimization.

• Strengthening Design (Construction Drawing Design): After the plan is determined, conduct detailed construction drawing design, specifying the specific strengthening methods, material selection, structural requirements, connection details, and construction sequence. The design must comply with relevant national codes and standards, such as GB55021 "General Specification for Assessment and Strengthening of Existing Buildings".

• Construction and Acceptance: Strictly carry out construction according to the strengthening design documents and relevant specifications, and conduct quality inspection and completion acceptance after completion.

Main Strengthening Technologies and Methods

Depending on different structural types and damage conditions, the strengthening design will select appropriate technologies, including:

• Enlarging Cross-section Method: Increasing the cross-sectional size and strengthening of original components (such as beams and columns) to improve bearing capacity.

• External Steel Jacketing Method: Covering concrete components with steel sections to significantly improve their bearing capacity and seismic resistance.

• Carbon Fiber Fabric/Plate Bonding Method: Utilizing the high-strength characteristics of carbon fiber materials to improve the tensile and shear strength of components through bonding. • Prestressing strengthening method: Applying prestress to the structure to improve its stress state.

• Rebar planting and anchoring technology: Used for connecting new and old structures and anchoring newly added components.

• Foundation strenthening: Addressing issues such as insufficient bearing capacity or uneven settlement of the foundation.

Key Principles

• Safety and reliability: The reinforced structure must meet the safety requirements of current standards.

• Treatment before strengthening: For structural damage caused by factors such as corrosion or uneven foundation settlement, effective measures should be taken first to eliminate or limit the harmful factors before strengthening.

• Close integration with site conditions: Strengthening design must consider actual site conditions and construction conditions, and ensure reliable connection between new and old structures to form a unified working system.

• Compliance with standards: The inspection, assessment, and strengthening of existing buildings must strictly adhere to relevant national and industry standards.

Building inspection and strengthening/retrofit design are crucial links in ensuring the safety of existing buildings, extending their service life, and meeting modern functional requirements.