Introduction to RISA Tools for Temporary Structures

Temporary structures—from construction shoring and scaffolding to event staging and emergency shelters—must meet the same rigorous safety standards as permanent buildings, but often under tighter deadlines and with less margin for error. Engineers rely on specialized software to design and analyze these structures efficiently while ensuring compliance with relevant codes. RISA Technologies offers a comprehensive suite of structural engineering tools that have become industry standards for both permanent and temporary works. The RISA portfolio includes RISA-3D, RISAFloor, RISAFoundation, and RISAConnection, each tailored to address specific aspects of structural design.

For temporary structures, the ability to model quickly, apply realistic loads, and verify performance across multiple failure modes is critical. RISA tools excel in this domain by providing a unified platform that integrates modeling, analysis, design, and reporting. Engineers can move from concept to documentation in a fraction of the time required by traditional methods, while still maintaining the depth of analysis needed for safety-critical structures.

This article provides a detailed walkthrough of the design and analysis workflow for temporary structures using RISA software, covering modeling techniques, load application, material selection, code checking, optimization, and practical considerations. By the end, you will have a clear understanding of how to leverage these tools to deliver reliable, cost-effective temporary designs.

Overview of the RISA Tool Suite

RISA Technologies provides several modular software packages. For temporary structures, the most commonly used are:

  • RISA-3D: A general-purpose 3D structural analysis and design program for frames, trusses, and shells. It supports steel, concrete, timber, aluminum, and cold-formed steel. This is the primary tool for temporary frame analysis.
  • RISAFloor: Used for lateral and gravity load distribution in floor and roof systems. Useful for elevated staging or platform structures.
  • RISAFoundation: For designing and analyzing footings, mats, and pile caps. Essential for temporary foundations like crane pads or shoring bases.
  • RISAConnection: For designing steel connections—critical for temporary frames where bolted or pinned connections are common.

All RISA tools share a common interface and data model, allowing seamless transfer of models between modules. This integration is especially beneficial for temporary structures where the entire assembly—superstructure, foundations, and connections—must be evaluated together.

Model Creation for Temporary Structures

Building the 3D Model

The first step in any RISA project is creating an accurate 3D representation of the temporary structure. The modeling environment in RISA-3D allows users to define nodes, members, plates, and surfaces. For temporary structures, which often consist of repetitive frames (e.g., scaffolding towers, truss systems, or adjustable shoring), the copy, mirror, and array tools speed model generation significantly.

Key considerations when modeling temporary structures:

  • Define geometry exactly: Include all braces, ties, and bracing systems. Even non-structural elements like handrails or safety nets can affect load distribution if they engage with the primary system.
  • Member end releases: Temporary connections are often pinned or partially fixed. Use RISA’s release features to model hinges accurately, as connection stiffness heavily influences load paths and deflections.
  • Non-structural elements: Use massless or dummy members to represent walkways, platforms, or cladding that contribute load but not stiffness, unless they provide diaphragm action.
  • Ground support: Model supports at foundations, with appropriate stiffness values for soil or bearing pads. Use spring supports for flexible soil conditions.

Best Practices for Efficiency

  • Use grouping and labeling to organize members by function (e.g., “Main Columns,” “Cross Braces,” “Decking”). This simplifies later results review.
  • Create design rules for member sizing so RISA can automatically select sections during iteration.
  • Import geometry from CAD or BIM tools for complex structures, reducing manual input errors.

Load Analysis and Application

Temporary structures must withstand a variety of load conditions, often more severe than permanent ones due to construction-stage exposure or event-specific demands. RISA provides flexible load definition and combination tools.

Dead and Live Loads

Dead loads include self-weight of the structure (automatically calculated by RISA) plus any permanent attachments. Live loads cover workers, materials, stored items, and equipment. For temporary structures, live loads can be highly variable—for example, a concert stage may have crowd loads, while construction shoring supports wet concrete. Use RISA’s area load assignment to apply distributed loads on surfaces or member uniform loads.

Environmental Loads

Wind, snow, and seismic loads are code-dependent. RISA integrates with major building codes (IBC, ASCE 7, AASHTO, etc.) to generate wind pressures based on exposure categories, topographic factors, and gust effects. For temporary structures, note that reduced load factors may apply per ASCE 37-14 (Design Loads on Structures During Construction). RISA allows manual override of load factors to match construction-specific codes.

  • Wind loads: Define wind speed, exposure, and importance factor. For open truss work, use RISA’s member wind load generator. For cladded structures, use surface pressure coefficients.
  • Snow loads: Apply drift and unbalanced loading as required by code.
  • Seismic loads: Use response spectrum or equivalent lateral force methods. For temporary structures with low occupancy, RISA can apply reduced R factors.

Construction and Erection Loads

These are unique to temporary works. Examples include point loads from cranes, concentrated loads at erection joints, and dynamic loads from pouring concrete. Model these as moving loads or placed at critical locations using RISA’s load placement tools. The software’s ability to run multiple load cases simultaneously helps identify worst-case scenarios.

Load Combinations

RISA automatically generates code-required load combinations. For temporary structures, you should also include construction-specific combinations (e.g., dead + construction live + wind reduced). Custom combinations can be created manually. Always check that the combination set includes the required safety factors for the temporary state.

Material Selection and Properties

RISA supports a wide range of materials: steel (A36, A992, etc.), aluminum (6061-T6, 6063-T5), timber (Douglas Fir, Southern Pine, glulam), concrete (normal weight, lightweight), and plastics/composites. For temporary structures, material choice is driven by strength-to-weight ratio, durability, and ease of assembly.

Steel and Aluminum

Steel is common for heavy shoring and large-span trusses. Use high-strength grades to reduce member sizes. Aluminum is popular for scaffolding due to its light weight and corrosion resistance. In RISA, you can import material databases or define custom materials. Ensure that the modulus of elasticity, yield strength, and density are accurate.

Timber

For temporary works like formwork and falsework, timber is often used. RISA includes NDS (National Design Specification) design checks for wood. Pay attention to load duration factors, as temporary structures often qualify for increased allowable stress due to short load durations.

Cold-Formed Steel

For light framing and temporary partitions, cold-formed steel is efficient. RISA’s metal framing module (RISAFloor) can design these sections per AISI standards.

Design Checks and Code Compliance

Once loads and materials are defined, RISA runs design checks to verify strength, stability, and serviceability. The software supports multiple design codes simultaneously, allowing you to check against both the local building code and a temporary works standard like BS 5975 (UK) or AS 3610 (Australia).

Stress and Deflection Limits

Temporary structures often have relaxed deflection criteria, but safety requirements are not reduced. RISA produces a serviceability check table where you can set custom deflection limits (e.g., L/180 for scaffolding decks vs. L/240 for permanent floors). The software highlights members that exceed limits, and you can iterate design.

Stability and Buckling

P-Delta and buckling analysis are essential for slender temporary frames. RISA-3D includes second-order analysis (AISC Direct Analysis Method) that accounts for both P-Δ and P-δ effects. Use this for structures where axial loads are high relative to member stiffness, such as multi-story shoring towers. For truss systems, ensure that compression members are checked for buckling in both principal axes.

Connection Design

RISAConnection can be used for bolted, welded, or pinned joints. Temporary connections often rely on simple bolted splices or couplers. The software checks bolt shear, bearing, and capacity. For proprietary connection systems (e.g., ring-lock or wedge-scaffold), you may need to manually verify using manufacturer data, but RISAConnection still helps with surrounding member forces.

Advanced Analysis Capabilities

Nonlinear and Dynamic Analysis

Temporary structures may experience dynamic loads from wind gusts, crowd movement, or equipment operation. RISA-3D supports nonlinear time history analysis and modal analysis. Use these to check for resonance or excessive vibration on event stages or bridge falsework. The software can output member forces at each time step, helping identify worst-case transients.

Progressive Collapse and Redundancy

For critical temporary works (e.g., grandstands, temporary bridges), check the structure’s ability to redistribute loads if one member fails. RISA can simulate member removal and evaluate alternate load paths. This is a powerful feature when designing for robustness under unpredictable construction loads.

Optimization and Efficiency Strategies

RISA includes built-in optimization tools that adjust member sizes to meet design criteria with minimal weight. For temporary structures, minimizing weight reduces cost and handling effort. Use the AutoDesign feature to let RISA select the lightest available section for each member based on strength and deflection limits. Additionally, manually adjust bracing patterns to reduce span lengths.

For reusability, design temporary structures with modular components that can be easily reconfigured. RISA’s parametric modeling allows you to change dimensions and see the effect on performance instantly.

Practical Applications and Case Studies

Construction Shoring and Formwork

Heavy shoring systems for bridge falsework or high-rise slab construction require precise load take-down and stability analysis. A typical workflow in RISA: model the shoring tower grid, apply concrete dead load plus construction live load, run code checks for AISC 360 or ACI 318, and optimize member sizes. One real-world project used RISA-3D to design a 50-foot-tall shoring tower supporting a balanced cantilever bridge segment, reducing steel tonnage by 15% compared to traditional methods.

Event Staging and Temporary Platforms

Concert stages, parade stands, and seating towers must resist wind and crowd loads. RISA’s ability to model complex loading from cladding (e.g., banners or video screens) and apply wind pressures on surfaces is invaluable. In one case, a temporary festival stage was analyzed using RISA, revealing a critical buckling mode in a roof truss that was subsequently stiffened before erection.

Emergency and Disaster Response Structures

Rapidly deployable shelters and temporary bridges used by relief organizations benefit from RISA’s quick model generation and code compliance. Engineers at a humanitarian engineering firm used RISA to design a modular steel bridge that could be assembled by hand and support heavy rescue vehicles, meeting AASHTO pedestrian loads with a 20% safety margin.

Advantages of Using RISA Tools for Temporary Structures

  • Integrated workflow: One model serves for analysis, design, and connection checks, reducing data transfer errors.
  • Code flexibility: Supports international codes and allows custom factors for temporary works standards.
  • Visual feedback: Color-coded results (stress ratios, deflection, axial force) make it easy to spot problem areas.
  • Documentation: Generates detailed calculation reports that can be submitted for plan check or PE stamping.
  • Efficiency: Automatic design iterations cut down manual calculation time significantly.

Conclusion

Designing and analyzing temporary structures is a demanding discipline that requires accurate modeling, proper load application, and thorough code compliance. RISA Technologies provides a powerful suite of tools that enables engineers to handle these challenges with confidence. By leveraging RISA-3D, RISAFloor, RISAFoundation, and RISAConnection, professionals can create safe, efficient, and cost-effective temporary works that meet the highest safety standards.

Whether you are designing shoring for a skyscraper, scaffolding for a stadium, or a temporary bridge for disaster relief, RISA software streamlines the process and helps you deliver reliable results under tight deadlines. With continuous updates and responsive support, RISA remains a trusted partner for structural engineers worldwide.

For more information on RISA products and temporary structure design, visit the official RISA website (risa.com) and explore the knowledge base articles and sample projects. Additional resources on construction loads can be found in ASCE 37-14 and the Temporary Works Forum publications (temporaryworksforum.org.uk).