How do structural consultants save time and effort in every project stage?

Did you know that inadequate planning in the early stages of a structural project can lead to costly rework and delays? I have seen firsthand how meticulous planning at each project stage can save time and resources. In this article, we’ll explore how you can support clients—from developers to architectural consultants—throughout each critical stage, starting with the often-overlooked concept stage.

Main Project Stages:

a. Concept Stage.

b. Schematic Stage.

c. Detail Design Stage.

d. Tender Stage.

e. Issue for Construction (IFC) Stage.

Note: Municipality & Authority Approval are not mentioned here as the structural role differs from country to country.

a-Concept Stage:

The concept stage is crucial, yet often overlooked by many consultants.

We believe that investing effort in this phase saves time and resources, making subsequent stages more straightforward.

Key Points in the Concept Stage:

1-. Understand Client Requirements: Collect all available information from the client to fully grasp their needs and requirements. Ensure the client is aware of all necessary documents required to proceed smoothly, avoiding any interruptions in the workflow.

2. Propose Multiple Options: Present several structural system options, highlighting the pros and cons of each. Ensure the client fully understands and agrees with the chosen system. This agreement helps to eliminate the possibility of changes in later stages under the guise of cost reduction or due to input from other stakeholders.

3. Budget Considerations: Determine the construction budget for the structural work early in the project. This budget serves as a guideline for coordinating with the architectural team and selecting the appropriate structural system within the client’s financial constraints. For example, in one of our projects, a client requested a 25-meter clear span for an office building. We proposed several options to meet this requirement but, understanding the client's budget constraints, highlighted the construction cost implications. This transparency allowed the client to make an informed decision, ultimately opting to reduce the span to 15 meters, which still met the functional requirements within their budget.

Monitoring the client's budget and comparing it to the design at each project stage is crucial to avoid any rework. In several instances, projects were completed and later sent to us to study how we could reduce costs.

4. Agree on Design Criteria: Establish design criteria, materials, design codes, and any special client requirements. Ensure a thorough understanding of local building codes, as they often take precedence over international codes. For example, Design Coefficients and Factors for Seismic Force-Resisting Systems in the SBC local code may differ from those in the ASCE code.

5. Basic Analysis: Conduct preliminary analyses to demonstrate the recommended systems without delving into detailed calculations. Use your experience to minimize effort.

6. Initial Coordination with Geotechnical and Wind Tunnel Consultants: Provide proposed borehole locations and depths. Supply basic structural dynamic behaviour information to wind tunnel teams for preliminary analysis.

7. Highlight Potential Cost Reductions or Construction Challenges: Identify potential savings and construction challenges early in the project. Communicate these insights to the architectural team and the client to ensure cost efficiencies are realized without impacting the building’s function.

b-Schematic Stage

After agreeing on the structural layout with the client, the schematic stage involves developing analysis models and coordinating with other disciplines. The challenge here is to accommodate all disciplines' requirements while finalizing concrete dimensions. This stage includes several meetings with wind tunnel teams, geotechnical consultants, MEP, landscape, and other consultants to refine the structural system and determine the most efficient structure. At the end of this stage, refine your construction budget analysis and ensure it remains within the client’s budget.

c-Detail Design Stage

During the detail design stage, the focus shifts to developing detailed drawings with reinforcement details to ensure the contract package is ready for pricing. This phase involves minimal coordination with other disciplines, allowing for concentrated effort on the structural details. The project cost should be finalized at this stage and should remain within the client’s budget.

d-Tender Stage

In the tender stage, contractors will price the package, and you may receive queries regarding the design. Respond to their queries and add the required details to ensure clarity in the IFC package.

e-Issue for Construction (IFC) Stage

At this stage, a complete structural package is prepared, incorporating any additional contractor requirements.

By meticulously supporting your clients through each project stage, you help them achieve their goals efficiently and effectively and this is our proactive approach in our office, especially in the concept stage, sets the foundation for successful project execution and minimal rework.

Conclusion

Understanding the importance of each project stage and the role of a structural consultant can save time, reduce costs, and ensure the success of the project. Our detailed attention to the concept stage and continuous support throughout the project lifecycle distinguishes our consultancy services. Thoughtful planning and expert guidance can make a significant difference in achieving project goals smoothly and efficiently.

 Our commitment to client support extends beyond the submission of the IFC package, as we respond to any site team queries to ensure the project is completed as designed.

By meticulously supporting our clients through each project stage, we help them achieve their goals efficiently and effectively. Our proactive approach, especially in the concept stage, sets the foundation for successful project execution and minimal rework.

Lack of communication between structural engineers and geotechnical engineers can increase the construction cost.

Cooperation between the geotechnical engineers and structural engineers is the key to a project’s success. However, there is always a gap in communication between them.

The main causes of poor communication.

The client always hires the geotechnical consultant, while the architectural consultant always engages the structural consultant. Consequently, the main consultant does not manage the geotechnical engineer.

In some cases, the geotechnical consultant completes their work before the main consultant is assigned to the project.

Usually, the structural consultant fees do not include any allowance for managing the geotechnical consultant.

In most projects, The client allocates a small budget to conduct a geotechnical report. Consequently, this limits the field tests and information needed by the structural engineer.

Information required by the geotechnical consultant.

The more information the main consultants provide, the better recommendation you will receive. In general, geotechnical engineer needs :

1-    Building location on the site plan.

3-    Building section indicates the basement floor height and location.

4-    Building height.

5-    Columns and wall loads if available.

What do you expect to receive from the geotechnical consultant?

The Geotechnical report provides critical and vital information for the contractor and structural engineer. Here are the basic information included in the soil report.

1-    Allowable bearing capacity under gravity load and lateral loads.

2-    Minimum level of excavation.

3-    Recommendation for the type of foundation.

4-    Total and difference settlement allowance.

5-    Initial subgrade reaction.

6-    Recommendation of cement type for underground structure elements.

7-    Higher and lower groundwater table level.

8-    Seismicity and earthquake site classification.

9-    Recommendations for the construction of temporary and permanent cut, fill slopes and slope protection.

10- Recommendations for any shoring, sheet piling and dewatering (if required) for installation of below-grade structures and utilities.

11- Active and at‐rest pressures for design of free‐standing and restraint retaining walls and sheet pilings if needed.

12- Passive earth pressure and coefficients of friction for resisting lateral loads.

13- Appropriate factors of safety for the recommended pressure values should also be discussed.

14-  Recommendations for excavation and shoring method.

15-  Recommendation for slope protection and retention methods.

The effective communication process that leads to project success.

There general iterative process steps as follows :

1- Columns and walls load come from the structural engineer considering the building base condition as a fixed base.

2- The geotechnical consultant receives the columns loads and applies them to their own model to determine the building settlements, bearing pressure under the raft, soil spring and soil subgrade reaction then send the information back to the structural consultant.

3-  The communication between the geotechnical consultant and the structural consultant goes back and forth until they converge on the columns’ load and settlement value.

Minimum reinforcement ratio in piles

1-Introduction :

The Piles are a structural element that can be wood, steel sections, precast concrete, cast-in-place concrete, and composite type piles and etc.

The main function of the piles include :

1- Transferring load from the superstructure through weak compressible strata onto stiffer soils or onto rock.

2-Resisting uplift force when used to support tall structures or basement below the groundwater table.

3- Control the settlement.

4- Used in marine structures to resist the lateral loads from the impact of berthing ships and from waves.

2- Type of piles based on function.

Classification of piles with respect to functional behaviour as follows :

a- End-bearing pile: This type of pile derives most of its capacity from a bearing stratum on which the tip bears.

b- Friction pile: This type of pile derives its resistance primarily from friction or adhesion along the length of the pile. They are commonly used where a bearing stratum is too deep to be usable. A pile that resists tension does so by friction and would be considered a friction pile.

c- Combined end-bearing and friction pile: This type of pile derives its resistance from a combination of end bearing and friction

d- Batter pile: this is a pile that driven at an angle with respect to vertical to resist horizontal force.

e-Mirco pile.

2- Pile reinforcement detail :

Pile reinforcement detail is one of the issues that are unclear, and there is conflicting information in ACI 318, ASCE 7 and IBC foundations, but now ACI 318-19 eliminated that conflict. Below table explains the minimum reinforcement requirements.

References.

1.   Building code requirements for structural concrete (ACI 318-19) and commentary.

2.   International building code 2015

3.   Foundation analysis and design.

Introduction to P DELTA EFFECTS.

1- Each element has two types of stiffness matrices:

A-Mechanical Stiffness Matrix (Km):

This matrix is based on the physical properties of the element and it is not related to the forces, therefore this matrix can be determined from the first-order analysis step.

B-Geometric/Stress Stiffness Matrix (Kg):

This matrix is a direct function of element’s end joints forces and deformations, thus it couldn’t be determined unless the first-order analysis step is performed, and then extracted forces and deformations are used to formulate the geometric matrix.

The Total Stiffness of the element (Kt) is the total of Mechanical (Km) and Geometric stiffness matrices (Kg).

If the forces extracted from first-order analysis step are compressions, then (Kg) will be negative stiffness, and thus (Kt) will be less than the initial (Km) i.e. (Kt = Km – Kg), meaning that the total stiffness of the element is reduced. And in case that the magnitude of compressive force is so big in a way making Kg > Km, so (Kt) will be negative, and this meaning physically that the structure is unstable.

2- P-Delta effect: is a type of geometric nonlinearity, involves the equilibrium compatibility relationships of a structural system loaded about its deflected configuration.

Of particular concern is the application of gravity load on laterally displaced multi-story building structures. This condition magnifies story drift and certain mechanical behaviors while reducing deformation capacity.

The two sources of P-Delta effect are described as follows:

A- P-Δ effect, or P-"big-delta", is associated with displacements of the member ends. A large P-delta effect is important for overall structure behavior under significant axial load. and To consider P-Δ effect directly, gravity load should be present during nonlinear analysis. The ETABS does a good job of capturing the effect due to the Δ deformation, but it does not typically capture the effect of the δ deformation.

B- P-δ effect, or P-"small-delta", is associated with local deformation relative to the element chord between end nodes. Small P-delta effect is important for local buckling and for design algorithms that expect member buckling to be accounted for by analysis. 

In ETAB software, the columns may be subdivided using nodes along their length to evaluate slenderness effects between the ends which is not recommended for concrete elements.

Alternatively, ACI section R 6.7.1.2 allowed that If the column is not subdivided along its length, slenderness effects may be evaluated using the nonsway moment magnifier method specified in 6.6.4.5 (Moment magnification method: Nonsway frames) with member-end moments From the second-order elastic analysis which the same process in ETAB software.

Bear in mind the following issues:

1- If Pu exceeds 0.75Pc the column would be unstable. Hence, if Pu exceeds 0.75Pc , the column cross-section must be enlarged.

2- IF δ exceeds 1.4, ACI code Section 6.2.6 requires that the column cross-section should be enlarged.

3-Sway or not sway

For the purposes of design, a story or a frame can be considered “nonsway” if the moments due to lateral deflections are small compared with the first-order moments due to lateral loads. ACI Code Section 6.6.4.3(a) allows designers to assume that a frame is nonsway if the increase in column-end moments due to second-order effects does not exceed 5 percent of the first-order moments. This can be achieved when the horizontal deflection of one end of a column relative to the other end is prevented, or at least restrained, by walls or other bracing elements. 

4- P delta analysis perimeter in ETABS

https://wiki.csiamerica.com/display/etabs/P-Delta+analysis+parameters

Reference :

1.   Building code requirements for structural concrete (ACI 318-14) and commentary.

2.   Geometric stiffness and p-delta effects by ED Wilson.

3- ETAB software manual.

4- Reinforced concrete Mechanics and Design book.

Introduction to Diaphragm design.

1-Diaphragms:

Diaphragms is a horizontal or sloped system acting to transmit lateral forces to vertical elements of the lateral force-resisting system (LFRS). Generally provided by the floor and roof systems of the building; sometimes, however, horizontal bracing systems independent of the roof or floor structure serve as diaphragms.

There are many types of materials and systems for use as floor and roof diaphragms.

Such as; Concrete slabs, Precast concrete floor planks with concrete topping, Metal decking with concrete fill, Roof sheathing .. etc.

2- Diaphragms roles for the structure, the main purpose of the diaphragm is to distribute lateral forces to the elements of the LFRS also it is doing the following:

1- Resist gravity loads.

2-Provide lateral Support to vertical elements.

3-Transfer lateral inertial forces to vertical elements of the seismic force-resisting system.

4- Transfer forces through the diaphragm.

The Largest diaphragm transfer forces should be anticipated at offsets or discontinuities of the vertical elements of the seismic-force-resisting system such as.

(a) Setback in the building profile

(b) Podium level at grade.

3- Diaphragms components:

A-Chord:

Is assumed to resist all the flexural tension from the diaphragm in-plane bending moment resulting from the lateral load. In case the edge beam is not existed the slab will act as a deep beam to resist flexural tension force and the chord tension reinforcement to be placed within h/4 of the tension face, where h is the diaphragm width in the direction of the analysis (section 12.5.2.3 of ACI code).

B-Collector:

Also called drag struts or ties, are diaphragm framing members that collect diaphragm shear forces from laterally unsupported areas to vertical resisting elements. The collector width can be fit within the shear wall width but in some cases, it has to be wider.

SEAOC 2005 recommends the collector effective width beff to not exceed the wall width plus a width on either side of the wall equal to half the contact length between the diaphragm and the wall.

4- Behavior of Diaphragms

The behavior of a diaphragm can be as beam that is supported springing which represents the lateral stiffness of lateral resisting elements. The floor or roof system acts as the beam web which resists the design shear force the chords behave as flange elements resisting the axial tension or compression resulting from flexural behavior.

5-Type of diaphragms:

Diaphragms are typically classified into three categories: rigid, flexible and semi-rigid

a- Rigid diaphragms 

ASCE7-10 ( section 12.3.1.2) permits the assumption of rigid if the diaphragms aspect ratio is 3 or less for seismic and 2 or less for wind load ( section 27.5.4 of ASCE7-10) if the structure has no significant horizontal irregularities. The seismic story shear is to be distributed to the vertical elements of the LFRS based on the relative lateral stiffness of those elements.

b-Flexible:

Diaphragms is permitted to be flexible when the computed maximum in-plane deflection of the diaphragm under lateral load is more than two times the average story drift of adjoining vertical elements of the seismic force-resisting system of the associated story under equivalent tributary lateral load as shown in the above Fig. 12.3-1.

The seismic story shear is to be distributed to the vertical elements of the LFRS based on the tributary area. And the diaphragm deflection is significantly high compare to LFRS

c- Semi-rigid diaphragms simulate actual in-plane stiffness properties and behavior. it should be modeled when significant in-plane deformation does occur, or when required by code.

6- Code requirements:

The seismic design of the diaphragm is required for all buildings in SDC B to F.

ASCE7-10 12.10 required diaphragms to be designed for the internal forces determined as the maximum of :

a-    

b-    

The detailing of diaphragms is generally independent of the type of LFRS for building, therefore, the R-value does not appear in the upper and lower limit equation.

Section 18.12 of ACI 318-14 shall only apply for diaphragm design in building assigned to SDC D to F only. while chapter 12 of ACI318-14 provisions shall be applied and for buildings assigned to SDC B and C.

7- Diaphragm modeling and analysis approaches

The internal force in diaphragm can be calculated from hand calculation till complex computer analysis depending on the building's irregularity.

The following methods can be used for analysis:

1-    Equivalent beam model.

2-    Equivalent beam on spring model.

3-    Corrected equivalent beam model.

4-    Strut and tie model.

5-    Finite element model.

8-How to obtain the diaphragm in ETAB.

The diaphragm forces can be obtained through sections cut as illustrated in the following link:  https://wiki.csiamerica.com/display/etabs/Diaphragm+forces

Bear in mind the Stiffness modifiers for RC diaphragms commonly fall in the range of 0.15 to 0.50 when analyzing the building for design-level earthquake demands (Nakaki, 2000).

References.

1.   Building code requirements for structural concrete (ACI 318-14) and commentary.

2.   Minimum design loads for buildings and other structures (ASCE 7-10)

3.   NEHRP Seismic Design Technical Brief No. 3.

Which code should you follow to comply with IBC .?

Unintended Addition of Stiffness can cause major damage.

Structural engineer Commons mistakes when using Saudi building code.

Previously, Structural engineers in Saudi Arabia use British or American codes based on their knowledge background because there was no clear guideline or code for them to use in designing . Moreover, Uniform building code provided limited information about seismic zone for few cities in Saudi Arabia .

In 2007 Saudi Building code (SBC) was published and since then we have clear code that satisfy our requirements.Unfortunately, we found out there are three common mistakes, the structural engineers always do when using the Saudi building code.

1-    Mix of codes requirements :

Recently, structural engineers in KSA are using IBC 2012 code /ASCE 7-10 standards along with wind and seismic map provided in SBC code; ignoring the fact of SBC is based on (IBC 2003) code/ ASCE7-02. Which lead to underestimate wind design load, and in some cases it may cause a building failure.

ASCE 7-10 contains significant changes from ASCE 7-02 in the areas of seismic design, wind design, and more.

In ASCE7-10 the wind speed values represent “Ultimate” wind speeds , therefore, Strength design level wind speeds replaces the ASD level wind speeds. But in SBC the wind speed value represent “service “wind speed.

This is the reason the load factor is 1.0 for wind instead in ASCE7-10 While the load factor is 1.6 in SBC code .

Load combinations as per (ASCE 7-10) as follows :

Load combinations as per Saudi building code (SBC) as follows

Therefore, in order to use ASCE7-10 you , the wind speed should be modified .

Fortunately, ASCE7-10 provide a table in the commentary to ease the transition, that provide conversation from the strength wind speed and wind service speed of ASCE7-05 as shown below :

2-    Missing load combination :

The SBC mentioned the load combination in section 2.3.2. However, there is additional load for designing concrete and masonry mentioned in the exception clause No.2 which usually unobserved .

3-    Design coefficients and factors for basic seismic force-resisting system 

SBC code is using lower value of the response modification coefficient(R), seismic over-strength factor and defection amplification factor Cd than IBC code .

New version of SBC is under reviewing and expected to be released by end of this year .