Phase 1: Pre-Construction Planning and Design
Proper planning in advance of construction lays the groundwork, both technically and legally, for steel structure projects. At this stage, we begin to contemplate the transformation of conceptual requirements into execution of action plans, and we assess our risk exposure downstream.
Structural Engineering, BIM Coordination, and Fabrication-Ready Detailing
As a part of the construction process, structural engineers provide design and build services to convert architects’ designs of a structure into legal realities. During this process, engineers ensure that the designed structures are resource optimal and enhance the resistance of the building to earthquakes. Engineers use BIM to eliminate design related clashes between various building elements. This approach is demonstrated to reduce rework by approximately 15% and thus saves time and costs. The last detailed construction drawings for fabrication are prepared. The drawings contain all the details for construction, including specification of bolt hole positions (with a 1.5 mm tolerance), CAD files for laser cutting, and materials which are certified to be in compliance with ASTM.
Before a competition starts, you've already won by communicating with the local governing bodies. They can point out the issues, and facilitate the acquisition of the needed documents since they are aware of the local zoning, environmental and building codes. It is good practice to get a review prior to construction starting to determine if there are any construction related issues, for example, cranes may have inadequate reach to service the construction location, or if there are dependencies in material transport. The best approach is for the parties involved in the project to deliver their project requirements/specifications contract integrated. The Owner is best positioned to manage conflicts. Issues are identified in advance and construction can proceed.
Thousands of issues have been identified and resolved in advance, making more issues resolvable. The effects of this approach include total control over the time and costs of additional works, enabling the Owners to achieve their desired state. The focus is to maintain Remaining Unresolved and Remaining Concerned at their desired state.
Phase 2: Off-Site Fabrication and Quality Assurance
Precision Fabrication: Cutting, Welding, and Surface Preparation (ASTM A6/SSPC-SP6)
There are three main processes in fabricating structural steel components, and they are also main points of quality control. First is cutting steel sheets using precision Laser/Plasma cutting. This cutting technology provides a +/- 2mm cutting tolerance which is critical in downstream assembly of steel components. Second, based on AWS D1.1, certified welders join the steel components. Sound wave testing is performed to determine if the welds are full and properly fused. Lastly, based on the Surface Preparation standard, SSPC-SP6, a blast anchor profile of 50-85 microns is developed. This profile provides a proper substrate for the coating system to adhere, and it also removes mill scale and rust. We are able to control the preparation and blast environment in this process which is also an advantage over the uncontrolled and unpredictable field environments. Prior to shipment, all components are evaluated in a coordinate measuring machine to assess if they are fitting within the permitted tolerances.
Our in-process QC and third-party inspection protocols
Constructing a robust QC system allows us to identify and address issues at every step of the production process. Checkpoint QC includes physical measurements taken by QC technicians and joint photographs taken by weld inspectors using digital X-ray weld imaging. Surprise QC audits are performed by ISO 17020 third-party inspectors and AISC 303 compliance consultants. Depending on the size of the audit, non-destructive tests (NDT) of surface crack assessments using magnetic particles and hardness assessments (post-heat) and coating thickness measurements are performed on the audit checklist. Safety audits from the previous year showed a 66% reduction of defects, on average, using a three-level, tiered QC system, as compared to single-stage inspections. We employ a thorough traceability system to track and document the history of every component of the product, from the point of origin of the raw material to the finished product.
Phase 3: Site Preparation and Foundation Integration
Site preparation is one of the most critical steps in the construction of steel structures. At the beginning of the process, the construction team clears the construction site of any unnecessary remnants of old structures, as well as other types of debris and biomass in the form of trees and shrubs. Once the site is cleared, they level the working area to ensure the surface of the ground is even to within 25 mm in any direction. Different construction platforms and buildings require different amounts of bearing capacity. Before excavation of the foundations of the building begins, construction engineers conduct soil tests to determine the soil's bearing capacity. During the soil preparation process, construction workers compact the soil in multiple layers, as well as place any necessary conduits for the water, electricity, and communication systems. Once the soil is prepared, concrete is thermally treated, and construction workers place anchor bolts in grouted concrete for future alignment with the building's steel frame. After the concrete has fully cured, construction workers conduct a final inspection to determine if the construction site is within the specified tolerances. Once a construction site is fully prepared, construction engineers begin the actual construction process.
Phase 4: Erection of Structure and Stabization of Frames
Order of Erection: Bracing First, Priority of Wind Compartments
In windy conditions, stable assemblies of the steel structure are best constructed by starting with the insertion of the main braces as soon as the first columns are placed. This technique reduces vertical deflections and collapse concerns. With regard to wind compartments, builders operationally prefer to “section off” and wind compartment them rather than do them all. This also reduces overall vertical deflections on the structure. These principles are applied on construction sites, and improve safety of construction personnel and the overall quality of the structural assembly.
AISC 360 Compliance: Dimensional Calibration, Column and Rafter Positioning and Purlin Installation
Deviation from all measurements are within the AISC 360 Chapter 7 tolerances for the fabrication and erection processes. Surveys will show that deviations have been kept within the limits prior to the commencement of envelope installation.
Phase 5: Completion of Envelope and Project Closeout
Cladding, Thermal Bridging, and Pre-Handover Review
The final stage of the building envelope is the installation of cladding panels. Improving a building’s energy efficiency is dependent on the installation of cladding panels. Prior to this, the cladding contractors of the building align building panels using a corrosion-resistant fastening system, and create a watertight seal to the building joints. A primary concern during the construction process is thermal bridging. Thermal bridging is responsible for approximately 30% of the energy losses in commercial buildings. Thermal bridging occurs when insulating materials do not fully cover building connections. To overcome thermal bridging, builders maintain a constant and full insulation across the connection. Prior to the handover of a building, there is a 12-point checklist that the project team must meet to achieve a functional air and water barrier, as well as evaluate the integrity of the drainage system. The air barrier’s integrity is assessed using ASTM E283. Measurements and spacings are verified by the contractors to meet AISC 360. The warranty is completed and finalized. Each of these functions, ensure that the building is ready for occupancy, energy efficient, and code compliant.
FAQ
What is Pre-construction Planning in steel structure projects?
The pre-construction planning phase mitigates risks of rework by establishing the first of technical and regulatory frameworks and converting conceptual requirements to a detailed blueprint.
What advantages come from BIM coordination in the pre-construction phase?
BIM coordination allows for the identification of design issues early, meaning rework is decreased by around 15%. This saves both time and money.
What is the benefit of off-site fabrication compared to on-site work?
When working off-site, the environment is better controlled for work to be completed with higher precision, as well as better consistency. The adverse effects of inclement weather is also less influential.
What is the foundation integration phase and what does it encompass?
The foundation integration phase encompasses the clearing of the site, grading of the site, the conducting of soil tests, the installation of underground utilities, and the pouring of concrete for the foundation with positioned anchor bolts.
What ways is structural stability ensured during the erection of a building?
The structural stability is primarily ensured through a bracing-first approach and first utilizing wind compartments to brace the structure during the assembly phase.