Structural System Alternatives: Steel, Concrete, Wood, and Masonry for Program Requirements

Identifying and comparing structural system alternatives in steel, concrete, wood, and masonry during the programming phase, including how building type, function, program requirements, preliminary budget, schedule, seismic considerations, and sustainability goals influence system selection before design begins.

ARE · Programming & Analysis

Overview

Before a building has floor plans, elevations, or a design concept, someone has to answer a foundational question: what holds it up? This topic covers how architects identify and compare structural system alternatives in steel, concrete, wood, and masonry during the programming phase.

The ARE tests your ability to understand various structural materials and systems well enough to determine which ones fit a given project's needs. You're not designing the structure. You're identifying which systems could fulfill the program requirements based on building type, function, availability, cost, and sustainability goals.

Steel, concrete, wood, and masonry each carry distinct advantages and limitations. Steel spans long distances and goes up fast. Concrete handles compression forces and fire resistance with ease. Wood suits low-rise construction and renewable material goals. Masonry provides mass, durability, and lateral resistance in wall systems.

The real skill here isn't memorizing material properties in isolation. It's matching the right system to a specific set of project constraints: a 200-foot clear-span arena needs a completely different answer than a three-story office building on a tight urban lot. Budget, schedule, seismic zone, building height, occupancy type, and local material availability all shape the decision. Understanding those trade-offs is what NCARB expects you to demonstrate.

Essential

Selecting a structural system during programming is one of the earliest decisions that locks in cost, schedule, and performance characteristics for the entire project. You're not picking final member sizes. You're narrowing the field to systems that can meet the program, then evaluating trade-offs between them. ## How Structural Systems Are Categorized Structural systems sort into categories along two axes. First, the material: steel, concrete, masonry, or wood. Second, how the system resists lateral forces: through walls, frames, or a combination. The six broad categories recognized by ASCE/SEI 7 are: 1. Bearing wall systems: Walls carry both gravity loads and lateral forces. Common in residential, warehouse, and low-rise commercial construction using concrete, masonry, and wood. 2. Building frame systems: A complete space frame carries gravity loads; separate shear walls or braced frames handle lateral forces. Common in steel and reinforced concrete construction. 3.

Professional

Consider an architecture firm programming a six-story mixed-use building in a moderate seismic zone (SDC D). The owner wants retail on the ground floor with large storefront openings, office space on floors two through four, and residential units on floors five and six. The budget is mid-range, and the schedule calls for occupancy in 18 months. The structural engineer presents three alternatives: a steel moment frame, a reinforced concrete shear wall system, and a dual system combining concrete moment frames with concrete shear walls. The steel moment frame allows maximum flexibility for the retail ground floor, since no diagonal bracing or shear walls interrupt the storefront openings. But the steel will need fireproofing on every member, and the connections require special detailing to qualify as a special moment frame in SDC D. That detailing adds fabrication cost. The concrete shear wall system is less expensive per square foot.

TLDR

Six ASCE/SEI 7 system categories: bearing wall, building frame, moment-resisting frame, dual, cantilever column, and non-seismic
Steel: best strength-to-weight ratio, long spans, fast erection, needs fireproofing, ductile when detailed properly
Concrete: excellent compression and fire resistance, heavy, slow cast-in-place construction, quality depends on field work
Wood: lightweight, renewable, great for low-rise, combustible, sheathing type determines seismic classification
Masonry: durable compression material, unreinforced is brittle and seismic-restricted, needs expansion joints and cavity drainage
Ductility matters: R factor ranges 1-8; higher R means lower design forces but more rigorous detailing requirements
Dual systems: moment frame as backup to walls/braces; frame must resist at least 25% of seismic forces
K-braced frames and single-direction diagonal frames (>50%) are prohibited in seismic design
Programming question is never "which is best" but "which alternatives could work for these specific requirements"
Future expansion: design structural elements for future loads from day one; analyze wind and seismic for projected future configuration

ELI5

Think of a building's structural system like the skeleton inside a body. Just like humans have bones made of one material (calcium-based bone), buildings can have skeletons made of steel, concrete, wood, or masonry (brick and block). Each material has strengths and weaknesses, and picking the right one depends on what the building needs to do. Steel is like the skeleton of someone who does gymnastics. It's strong, flexible, and can stretch a long way without breaking. Steel buildings can have huge open spaces inside, like sports arenas. The downside? Steel gets weak when it's really hot, so you have to wrap it in fireproofing material. Think of it like putting sunscreen on someone who burns easily. Concrete is like a heavyweight boxer. Incredibly strong when you push on it (compression), but it cracks if you pull it apart (tension).

AREProgramming & Analysis

Structural System Alternatives: Steel, Concrete, Wood, and Masonry for Program Requirements

2 min read203 words

Choosing Structural Systems During Programming

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