ASCE/SEI 37-14 (R2019) Guide: On-Site Load Test Rules for Temporary Structures

Introduction: The “Proof is in the Testing” Standard for Temporary Works

For construction managers, field engineers, and inspectors, temporary structures—like falsework, shoring, formwork, and construction ramps—are the unsung heroes of a project. They carry critical loads during construction but are dismantled once their job is done. The core purpose of ASCE/SEI 37-14 (R2019), “Design Loads on Structures During Construction,” is to provide a standardized, rational framework for determining the loads these temporary structures must safely support. This guide translates that framework into actionable, on-site implementation steps. It fills a critical operational gap: moving beyond theoretical design assumptions to establish verifiable, on-site load test protocols that prove a temporary structure’s fitness for purpose before it is put into service. You will encounter this standard when planning lift operations, verifying shoring design before concrete placement, or when a project specification mandates a formal load test for a critical temporary installation.

What Problems Does ASCE/SEI 37 Solve On-Site?

The standard directly addresses several high-risk, costly on-site problems:
* Over-conservative or Under-designed Temporary Works: It prevents the dual risks of using excessive, costly materials based on overly conservative assumptions, or using under-designed systems that could fail under unexpected construction loads.
* Inconsistent Load Definitions: It standardizes how to account for real-world, dynamic construction loads—like impact from concrete placement, personnel and equipment concentrations, and environmental loads during the construction phase—which differ significantly from permanent design loads.
* Lack of a Clear Testing Protocol: It provides a recognized methodology for proving a design’s adequacy through load testing, giving field teams and inspectors a clear pass/fail criterion. This is crucial for avoiding disputes, rework, and ensuring safety.

Core On-Site Application: When and Who Uses This Standard?

This standard is a mandatory reference in project specifications across North America for major civil, commercial, and industrial projects. It is critical for:
* Temporary Works Designers & Checking Engineers: To calculate appropriate load combinations and factors for construction conditions.
* Construction Managers & Field Engineers: To plan and execute load tests, ensuring the temporary structure is ready for the upcoming construction phase.
* Third-Party Inspectors & Authority Having Jurisdiction (AHJ) Representatives: To verify that load tests are conducted in compliance with an accepted standard, providing objective evidence of safety.

Key On-Site Technical Requirements & Verification Points

ASCE/SEI 37’s operational power lies in its practical load factors and testing procedures. Unlike permanent design codes, it recognizes the shorter duration of loading and allows for a more realistic assessment of risk.

1. Understanding Construction Load Factors & Combinations
The standard defines specific load combinations (e.g., Dead Load + Construction Live Load + Environmental Load) with load factors typically lower than those for final design. For field personnel, this means:
* On-Site Implication: The test load you apply is not necessarily the full “ultimate” load from the permanent design code. It is a factored construction load. The design engineer should provide the required test load value based on ASCE 37 combinations.
* Verification Point: Confirm the test load value with the design engineer. It should be documented in the lift plan, shoring drawing, or test procedure.

2. Implementing the Mandatory Load Test Procedure
This is the standard’s most critical on-site activity. ASCE 37 provides a clear, step-by-step protocol.

Step-by-Step On-Site Load Test Implementation:
1. Pre-Test Documentation Review: Verify the design calculations, drawings, and the written test procedure. Ensure all components (jacks, gauges, instrumentation) are calibrated.
2. Visual Inspection: Conduct a thorough pre-test visual inspection of the entire temporary structure. Check for proper installation, alignment, bracing, and foundation bearing.
3. Apply Load in Increments: Load should be applied in stages (e.g., 25%, 50%, 75%, 100% of the test load). Hold at each stage for a specified time (per the standard or procedure) to allow for stabilization.
4. Monitor and Measure: Continuously monitor deflection at critical points (using dial gauges or survey equipment) and check for any signs of distress (unusual noises, cracking, yielding).
5. Hold at Full Test Load: Maintain the 100% test load for a minimum duration (typically 24 hours as a common specification, though ASCE 37 provides a basis for this requirement). Monitor continuously.
6. Post-Test Evaluation: After releasing the load, measure the residual (permanent) deflection. The structure should largely return to its original position.

On-Site Acceptance Criteria (The Pass/Fail Checklist):
* No Structural Failure: Obvious—no rupture, buckling, or connection failure.
* Deflection Limits: Maximum deflections under full test load should not exceed limits set by the designer (often based on span/360 or similar serviceability criteria).
* Recovery: The residual deflection after load removal should be small (e.g., less than 20% of the maximum measured deflection is a common benchmark). Significant permanent set indicates potential over-stressing.
* No Signs of Distress: No excessive cracking in concrete formwork, no yielding in steel members, and all connections remain tight.

Regulatory Context and Compliance Workflow

ASCE 37 is often invoked by project specifications and is endorsed by the Structural Engineering Institute (SEI). Its integration is practical:
* Permits & Audits: A documented load test following ASCE 37 is frequently required for permit approvals for major lifts or complex shoring from the local building department (AHJ). It serves as primary compliance evidence during audits.
* Handover Documentation: The signed test report—including load data, deflection readings, and inspector observations—becomes a permanent part of the project quality records, crucial for liability protection and project closeout.

Common On-Site Risks and Misconceptions

Risks of Non-Compliance:
* Catastrophic Structural Collapse: The most severe risk, leading to fatalities, injuries, and massive financial loss.
* Costly Project Delays: A failed test or, worse, a failure during construction leads to investigation, redesign, and rebuilding.
* Regulatory Shutdown: An AHJ can halt all work if temporary structures are not proven safe, causing significant schedule impacts.

Critical On-Site Misconceptions to Avoid:
1. “The Design Factor of Safety is Enough, We Don’t Need a Test.” ASCE 37 and project specs often mandate testing for a reason—to verify assumptions about material quality, workmanship, and actual load paths. Design and field execution are two different things.
2. “We Can Use the Same Load Factors as ACI 318 or AISC 360.” This is incorrect and can lead to an unsafe test (under-loading) or an unnecessarily conservative one (over-loading). ASCE 37’s factors are specifically calibrated for the unique risks and durations of the construction phase.
3. “If It Holds the Load, It Passes.” Not necessarily. Excessive deflection, even without collapse, can compromise the safety of the operation or the quality of the permanent work (e.g., sagging concrete forms). The deflection and recovery criteria are as important as the strength criterion.

Real-World On-Site Scenario

A field engineer is preparing for a large concrete deck pour on a bridge project using a complex system of falsework and shoring towers. The project specification requires a load test per ASCE 37. The engineer:
* Reviews the shoring designer’s report, which specifies a test load of 110% of the factored construction load (including wet concrete, workers, equipment, and a wind load allowance).
* Develops a test plan using water-filled bladders or calibrated jacking systems to apply the load evenly.
* Sets up dial gauges at mid-span and support points on the main beams.
* Executes the test in increments, holds for 24 hours at full load, and records deflections hourly.
* After load release, finds that 95% of the deflection recovered. The test report is signed by the engineer and the third-party inspector, submitted to the AHJ, and work is approved to proceed. This process objectively mitigates risk before placing hundreds of cubic yards of concrete.