Structural Engineering of The Mukaab — Four Corner Anchors, Load Systems, and Engineering Limits

Structural Engineering of The Mukaab: Building the Impossible Cube

The structural engineering challenge of The Mukaab is categorically different from that of conventional supertall towers. Where a tower concentrates its mass in a slender vertical column, The Mukaab distributes over two million square meters of floor space across a 400-meter cube — creating load management, wind resistance, and thermal movement challenges that required entirely new structural solutions. This analysis examines the engineering systems that make the world’s largest building structurally possible and the technical challenges that have informed expert debate about the project’s feasibility.

The Fundamental Challenge: Why a Cube Is Harder Than a Tower

Modern structural engineering has developed sophisticated solutions for tall, slender buildings. The Burj Khalifa at 828 meters, the Shanghai Tower at 632 meters, and dozens of supertall buildings exceeding 300 meters demonstrate that engineers can build vertically to extraordinary heights using established techniques: buttressed cores, outrigger trusses, tuned mass dampers, and aerodynamic tapering. These towers work because their narrow profiles minimize wind exposure, their tapering geometry reduces mass at the top where overturning moments are greatest, and their compact floor plates allow loads to be channeled efficiently through central cores to foundations.

The Mukaab abandons every one of these principles. At 400 meters in height, width, and depth, the structure presents flat surfaces of 160,000 square meters (400m x 400m) to wind — surfaces that generate aerodynamic forces orders of magnitude greater than the streamlined profiles of tapering towers. The structure does not taper; it maintains the same 400-meter width at the top as at the base, placing maximum dead load at maximum height. The floor plates span 400 meters in two directions — distances so great that conventional column-and-beam systems would produce inefficient, material-heavy structures. The structure houses an open central atrium — the spiraling tower and holographic dome — that removes structural material from the building’s core, eliminating the central core that provides the primary load path in conventional towers.

These challenges do not mean the structure is impossible, but they mean that the engineering solutions required are fundamentally different from those used in any existing building. The design consultants — AECOM and Jacobs — bring the global engineering expertise to address these challenges, but the solutions they develop will push the boundaries of structural engineering knowledge.

The Four Corner Anchors: The Primary Structural System

The fundamental structural strategy relies on four massive corner anchors, each comparable in scale to two or three Empire State Buildings. This comparison merits elaboration. The Empire State Building contains approximately 365,000 tons of structural steel and concrete across 102 floors rising to 443 meters (including antenna). Each corner anchor of The Mukaab, while not reaching the Empire State Building’s height, contains a comparable volume of structural material distributed across a footprint and height sufficient to support approximately one-quarter of the cube’s total load.

These corner anchors serve multiple structural functions simultaneously:

Gravity Load Path: All gravitational loads — the weight of floors, facades, residential units, amenities, mechanical systems, occupants, and furnishings — must ultimately reach the foundations through the structural frame. In The Mukaab, the floor plates span between the four corner anchors (and any intermediate structural elements), with loads flowing horizontally through the floors to the corner supports, then vertically down the anchors to the foundations. The magnitude of these gravity loads, distributed across over two million square meters of floor space with live loads varying from residential (approximately 2.0 kN/m2) to commercial (approximately 4.0 kN/m2) to mechanical (potentially 10.0+ kN/m2), creates foundation demands that dwarf those of any existing building.

Lateral Force Resistance: Wind loads and potential seismic forces act horizontally on the building, creating overturning moments that tend to tip the structure. In conventional towers, lateral forces are resisted by the central core — a concrete or steel tube running the full height of the building. In The Mukaab, with its open central atrium, lateral forces must be resisted by the corner anchors acting as vertical cantilevers fixed at their bases, with the floor plates acting as horizontal diaphragms distributing forces between the anchors. This perimeter-resistance strategy is effective but requires the corner anchors to be extremely stiff and the floor plates to act as rigid horizontal elements — both of which demand substantial structural material.

Torsional Resistance: Asymmetric wind loads (when wind acts more strongly on one face of the cube than another) and non-uniform gravity loads (when occupancy patterns create heavier loads on one side of the building) generate twisting forces. The four-corner anchor system provides torsional resistance through the box-like geometry formed by the four anchors and the floor diaphragms — a structural tube that resists twisting through shear in the floor plates and bending in the anchors.

Foundation Engineering: Building on the Riyadh Geology

The foundation system beneath the corner anchors extends deep into the Riyadh geology through piling systems designed to distribute loads that exceed those of any existing building. Riyadh sits on the Arabian Platform — a stable geological formation of sedimentary rocks (primarily limestone and sandstone) overlying the Arabian Shield’s crystalline basement. The sedimentary layers provide generally favorable conditions for deep foundation construction, with competent bearing strata accessible at depths that vary across the city but are typically within reach of modern piling techniques.

The piling systems for The Mukaab would likely employ bored piles — large-diameter concrete piles drilled into the rock to depths of 40 meters or more, depending on the subsurface conditions at the al-Qirawan site. The number and size of piles required depend on the per-pile capacity achievable in the local geology and the total load each foundation must carry. For context, the Burj Khalifa’s foundation system comprises 192 bored piles, each 1.5 meters in diameter and 50 meters long, bearing on a weak sandstone/siltstone layer. The Mukaab’s foundation demands, while different in configuration, are of comparable or greater magnitude.

The excavation phase validated the foundation engineering through direct observation and testing of subsurface conditions. By January 2025, over 10 million cubic meters of earth had been moved from beneath The Mukaab site, creating the below-grade volume necessary for the foundation system, underground service corridors, parking structures, and utility networks. The 86 percent completion of excavation confirmed that the geological conditions at the site are manageable with available construction technology — a significant de-risking milestone for the project.

Wind Engineering: The Aerodynamics of a Flat-Faced Cube

Wind loads on The Mukaab represent one of the project’s most technically demanding engineering challenges. Conventional towers are designed with aerodynamic profiles — tapering, chamfered corners, setbacks, and rounded forms — that reduce wind forces by allowing air to flow smoothly around the structure. The Mukaab, by contrast, presents flat surfaces of 160,000 square meters to the wind — surfaces that create turbulence, vortex shedding, and pressure differentials that generate enormous forces.

Wind engineering for The Mukaab would involve extensive wind tunnel testing using scaled physical models and computational fluid dynamics (CFD) simulations to map the pressure distribution across the building’s surfaces under all wind directions and speeds. These analyses determine the design wind loads that the structure must resist — loads that include steady-state pressure (the average force of wind on the surface), dynamic pressure (fluctuating forces caused by turbulence and vortex shedding), and aeroelastic effects (interaction between the building’s structural response and the wind forces, which can create resonance conditions).

The exterior screen — the overlapping triangular panels that define The Mukaab’s visual identity — plays a minor but positive role in wind engineering. The textured, faceted surface created by the overlapping panels disrupts laminar airflow more effectively than a smooth flat surface, potentially reducing organized vortex shedding and its associated dynamic forces. However, the primary wind resistance strategy relies on the structural stiffness of the four-corner anchor system and the floor plate diaphragms rather than facade geometry.

Thermal Movement: Managing Expansion Across 400 Meters

Thermal expansion and contraction across a 400-meter structural frame create movement dynamics that must be managed through sophisticated engineering systems. Steel expands approximately 12 millimeters per meter per degree Celsius change in temperature. Across a 400-meter span, a temperature change of 30 degrees Celsius (typical of the range between Riyadh’s nighttime winter temperature and daytime summer temperature experienced by exposed structural elements) produces a theoretical expansion of approximately 144 millimeters — nearly 15 centimeters. This magnitude of movement must be accommodated through expansion joints, sliding connections, and flexible structural elements that allow thermal movement without inducing damaging stresses in the structural frame.

Managing thermal movement in The Mukaab is complicated by the building’s complex geometry. Unlike a simple beam that expands in one direction, the three-dimensional structural frame of The Mukaab expands simultaneously in three dimensions, with different elements experiencing different temperature changes depending on their exposure to solar radiation, proximity to climate-controlled interior spaces, and shielding by the exterior screen. The expansion joint strategy must accommodate this differential movement without compromising the structural integrity of the floor diaphragms, the weathertightness of the facade, or the functionality of the smart building systems that run continuously through the structural frame.

Vibration Control: Comfort in the World’s Largest Occupied Structure

The vibration dynamics of a structure housing both occupied residential units and heavy mechanical systems — elevators, HVAC plant, holographic projection equipment, automated services — present comfort engineering challenges at unprecedented scale. Residents in luxury apartments expect quiet, vibration-free environments. Mechanical systems generate vibrations at frequencies and amplitudes that, if transmitted through the structure, would be perceptible and disturbing to occupants.

Vibration isolation strategies would include mounting heavy mechanical equipment on isolation systems (springs, rubber pads, or active vibration control platforms) that prevent vibration transmission to the structural frame. High-speed elevators would employ guide rail precision and vibration-dampened car suspensions to minimize the vibrations they generate during operation. The spiraling interior tower, if its helical geometry introduces unique vibration modes, would require tuned mass dampers or active damping systems to ensure comfort for occupants.

Floor vibration from human activity — walking, exercise, dancing — must also be managed through floor stiffness design that keeps acceleration responses within comfort criteria. In spans as large as those required in The Mukaab, maintaining floor stiffness sufficient to prevent perceptible bounce or vibration under normal occupant loading requires deep structural sections or post-tensioned concrete systems that increase floor weight and construction cost.

Expert Commentary and Engineering Debate

The Mukaab’s engineering feasibility has been the subject of expert debate within the structural engineering community. Some commentators have expressed concern about the structure’s feasibility under its own weight — questioning whether the massive gravity loads of a 400-meter cube can be efficiently channeled to foundations without requiring structural material quantities that make the project economically impractical. Others have highlighted the wind engineering challenges, noting that flat-faced structures of this scale have no precedent in the built environment.

These concerns, while technically legitimate, must be weighed against the credentials of the engineering team addressing them. AECOM and Jacobs, as Lead Design Consultants, represent the highest tier of global structural engineering capability. Their combined portfolio includes projects that pushed engineering boundaries at the time of their construction — projects that, before completion, generated similar skepticism about feasibility. The engineering profession has repeatedly demonstrated the ability to solve problems that initially appeared intractable, and The Mukaab’s challenges, while extreme, fall within the domain of known physics and available materials.

The January 2026 construction suspension relates to financing and feasibility reassessment by the Public Investment Fund rather than engineering failure. The excavation phase — reaching 86 percent completion with over 10 million cubic meters of earth moved — validated the foundation engineering without incident. The engineering challenges of above-ground construction remain to be tested, but the below-ground engineering has been proven. For the construction timeline and current status, see our progress coverage. For the architectural vision that the engineering serves, see our architecture section. For interior spaces within the structure, see our interior coverage.