Structural Engineering

The area of structural engineering is very broad and provides numerous analysis and design opportunities within the industry, but we believe our clients are better served when they can receive consulting services that are specific to particular needs, such as: foundation design, silo design, structural steel design, concrete design, etc.

Structural Steel Detailing

There is a common phrase in engineering “the devil is in the detail.” The transition from analysis and design to detailed drawings is critical to the safe execution of a project. Cohesive Engineers has the ability to develop both the engineering drawings and associated details, making our service in steel design a complete service. We help to seamlessly integrate our client requirements and recommendations through our rigorous standards and general practices. Our process typically includes submission of milestone drawings for our clients to make sure the final products are fully in line with the requirements.

The following are part of our project deliverables:

  • 3D Steel Modeling and 3D BIM Erection drawings
  • Shop fabrication drawings
  • Material take-off
  • Structural and Miscellaneous Steel Detailing
  • CNC files for shop fabrication
  • Steel Connection Design

Structural Concrete Detailing

Concrete design is an important part of structural engineering. Our team prides itself in speed of delivery, accurately and quality. Our engineers help to ensure a smooth transition of engineering design to design and detail drawings. The end product can be used by contractors for pricing and ease of constructions.

In the process of designing and detailing concrete, the positional interference is always a challenge for the actual design project. We help solve potential problems and find the best and most economy layout at the stage of engineering design and analysis, thus reducing possible time loss and value engineering opportunities.

The following are part of our project deliverables:

  • Preliminary design concept drawings and models.
  • General Arrangement drawings.
  • Production molded drawings.
  • Production reinforcement drawings.
  • Bar bending schedules.

Bins and Silos

Bulk material storage vessels (e.g., silos, bins, hoppers, elevators, bunkers) are available in a variety of shapes and sizes. The main types of material used in construction are steel and concrete. There are numerous factors to consider when selecting a silo, bin and/or hopper. The construction type is an important consideration due to the difference in behavior between steel and concrete. The location and use of the structure is also an important consideration, which often drives the design type.

There two main characteristics for consideration when selecting a storage vessels; functionally and structural design. The following structural considerations are important when designing a storage vessel:

  • Provide general configuration that meets capacity and spatial constraints.
  • Use bulk material flow properties that help select vessel design parameters Hopper shape, angle, and internal surface required for material flow pattern.
  • Ensure the required discharge rates and different load combinations are utilized in design process for outlet sizes and shapes ensuring adequate performance.
  • Use state-of-the-art FEA analysis to develop stress/strain profiles to determine worst case loading for all critical design elements. Provide cost-effective rehabilitation approach to modify existing storage vessels to fit the new building code requirements or expansion capabilities.

Dynamic Equipment Supports

Heavy machinery with reciprocating, impacting, or rotating masses requires a support system that can resist dynamic forces and the resulting vibrations. When excessive, such vibrations may be detrimental to the machinery, its support system, and any operating personnel subjected to them.

When designing these foundations, engineers should fully understand the varying backgrounds that are engaged in the analysis, design, construction, maintenance, and repair of machine foundations. Therefore, it is important that the owner/operator, geotechnical engineer, structural engineer, and equipment supplier collaborate during the design process. Each of these participants has inputs that are important and should be effectively communicated, especially considering that machine foundation design procedures and criteria are not covered in building codes and national standards.

Some firms and individuals have developed their own standards and specifications as a result of research and development activities, field studies, or many years of successful engineering or construction practices. Unfortunately, most of these standards are not available to many practitioners.

Pipe Supports

Industrial facilities are highly dependent on pipe rack structures. AISC Specification for Structural Steel Buildings (AISC 360-10) is the most common method for analysis and design of these pipe racks. Improper application of stability analysis methods could lead to unconservative results and potential instability in the structure jeopardizing the safety of not only the pipe rack structure but the entire industrial facility.

There are three main methods for stability analysis on pipe rack structures.
  • The first order method typically provided conservative results.
  • The effective length method was determined to underestimate the moment demand in beams or connections that resist column rotation.
  • The direct analysis method was found to be a powerful analysis tool as it requires no additional calculations to calculate additional notional loads, calculate effective length factors or verify AISC 360-10 limitations.
Stability analysis is acceptable as long as limitations are met and the methods are applied correctly.

Duct and Duct Supports

Two basis shapes are used in forming ductwork; rectangular and round. The ductwork units carry large volumes of high temperature, dusty air, between pieces of process equipment. Having a good understanding of these materials will interact and behave under extreme and air is important to their analysis and design. Rectangular ductwork is covered be the ASCE "The Structural Design of Air & Gas Ducts for Process Power Stations and Industrial Applications".

The structural design of ductwork plate is based on buckling of the plate element. Round ductwork plate design is based on diameter to duct plate thickness ratios, and the allowable stresses are contained in multiple references such as US Steel Plate, ASME/ANSI STS-1, SMNACA, Tubular Steel Structures, and other references.

Chimneys and Stacks

Having a strong understanding of the process of exhaust stream, such as volume, corrosiveness, temperature, and load conditions is critical to design chimneys and stacks. It is also required to understand the local environment and regional building code requirements. After confirming the desired geometry, and other design conditions such as gas entry and flow, base configuration, and lateral support etc., the design engineer can construct the numerical model to come out the final design.

Chimneys and stacks must be designed for the process, and then they will be analyzed to make sure they are mechanically strong enough to withstand the environmental adverse conditions. The following conditions are among the importance factors to be considered:

  • Location - The location and height of the stack is normally influenced by the process requirement, space allocation, and topography.
  • Wind & Seismic Loads - Wind and seismic loads are normally governed by the applicable local building codes.
  • Supports and Foundations - The supporting system can be design in a wide variety of configurations. The design engineer will have to decide the proper system to accommodate the level of loading and client specifications. Stack foundation is normally made of concrete. The foundation design will be according to the local concrete design code or the client agreed popular codes.
  • Access Platforms - Platforms are the common fixtures and they are normally designed per the requirements of OSHA and local building codes. Accessing to the platform is usually through ladders if there is no other convenient access from adjacent building or structure.
  • Corrosion Requirements - Materials of construction need to consider based on long term performance.

Foundation Design

The design of a foundation systems is dependent on three main factors; firstly, the type of structure being supported, secondly, the soil properties and thirdly, the seismic zone. Foundations usually fall in one of three types; shallow foundation, driven pile foundations and drilled shaft foundations.

When selecting a foundation system the following items have to be carefully considered:

  • The ability of the foundation type to meet performance requirements (e.g., deformation, bearing resistance, uplift resistance, lateral resistance/deformation)
  • Constructability issues with the particular type of foundation chosen
  • The location and impact of the foundation installation of existing foundation from existing structures
  • The environmental impact of the foundation construction
  • The cost of the foundation system
The overall goal of the foundation system is meet the load bearing capacity with limited amount of settlement. Our team of structural engineers is verse in the design most types of foundation systems. We work very closely with top tier Geotechnical Engineering firms to get quality predesign/investigative information.