Florida Waterslide Steel Supports

Project Overview

Project P-2023-072 involved the structural design of steel support structures for waterslide attractions at a Florida waterpark. Waterslide support structures are complex engineering problems: they must carry the weight of the fiberglass slide flumes, the water flowing through them, and the riders using them, while also resisting hurricane wind forces that in Florida can approach 160–185 mph in the design wind speed maps.

Florida Building Code (FBC) 2023 governs structural design throughout Florida. The FBC adopts ASCE 7 as its primary load standard with specific Florida amendments — particularly for wind design, where Florida's peninsular geography and frequent hurricane landfalls have resulted in wind design requirements more demanding than the base ASCE 7 provisions in many parts of the state.

Florida Building Code Wind Design

The FBC wind design provisions divide Florida into wind speed zones based on the ASCE 7 ultimate design wind speed maps. Coastal areas of Florida are designated as High-Velocity Hurricane Zone (HVHZ), which includes Miami-Dade and Broward counties and which applies the most rigorous wind design and product approval requirements in the United States. The project site wind exposure was classified and the appropriate basic wind speed from the FBC wind speed maps was applied.

For the waterslide support structures — classified as "other structures" per ASCE 7 Chapter 29 — wind forces were calculated using the force coefficient method, applying wind pressure to the projected area of each structural component. This method requires determination of wind directionality factor, exposure category factor, topographic factor, and applicable force coefficients for open framework structures. Open structural frames (lattice towers and support bents) carry significantly higher wind pressure per unit area than solid-faced structures because of turbulent wake interactions between members.

AISC-360 Member Design

The waterslide support members were designed per AISC 360-22. The primary structural elements were HSS (hollow structural sections) in round and square formats — chosen for their high strength-to-weight ratio, closed cross-section (important for corrosion resistance in a wet outdoor environment), and geometric suitability for the curved support configurations required by the waterslide layout geometry.

Combined loading governed the design of most primary support members: axial compression from gravity loads (slide dead load, water load, rider live load) combined with biaxial bending and axial force from wind loading. The AISC 360 Chapter H interaction equations were applied for combined loading checks. HSS compression members were checked for both flexural buckling and local buckling (wall slenderness limits), with wall thickness selected to ensure compact or at minimum noncompact section classification under all load combinations.

Waterslide Loading Conditions

Waterslide structures carry several distinct load types that require careful definition:

• Dead load — The self-weight of the steel support structure plus the weight of the fiberglass slide flumes and associated handrail and ladder systems.
• Water load — The weight of water in the slide flumes during operation. For large waterslides, the water volume can represent a substantial fraction of the total dead load and varies with operating condition (flowing vs static).
• Rider live load — Applied as a distributed live load along the slide line, representing the maximum density of riders that could be present simultaneously. This load is set conservatively to bound the actual operating condition.
• Wind load — Hurricane design wind pressures applied to the structural framing. In Florida, wind typically governs the lateral design of open support structures.
• Maintenance live load — Point loads representing maintenance workers accessing the structure for cleaning, inspection, and slide maintenance. Access walkway platforms must be designed for these loads.

Corrosion Considerations

Waterpark environments are among the most corrosively demanding conditions for structural steel. Chlorinated water, sun exposure, humidity, and physical abrasion from riders and maintenance create conditions that can cause rapid section loss in inadequately protected steel. The specification for this project required hot-dip galvanising of all steel components per ASTM A123, with touch-up paint at field welds. Stainless steel fasteners were specified at all bolted connections to eliminate bimetallic corrosion at steel-to-galvanised interfaces.

The structural design accounted for the corrosive environment by specifying no reduction in section for corrosion loss (galvanising provides full protection when properly applied and maintained), but the design report documented the maintenance requirements needed to preserve the assumed protection level over the structure's design life.

IBC Compliance

The International Building Code 2021, as adopted by Florida with FBC amendments, provided the load combination framework for the project. The governing load combinations for the support structures were wind-dominated combinations, with the ASCE 7-22 strength load combinations (1.2D + 1.0W + L) and (0.9D + 1.0W) applied with the FBC wind speed modifications.