Sure Pass Exam 93-Tall-Mass-Timber-Buildings PDF

The structural connections must maintain a fire-resistance rating corresponding to the required rating of the structural elements they connect. Because both the glulam beam and CLT panels require a two-hour fire-resistance rating, their connections must also provide two hours of fire resistance. Therefore, option C is correct.

Concealing steel hardware inside a timber member does not eliminate the fire-resistance requirement. Steel rapidly conducts heat and can lose strength, while timber surrounding a concealed connector can char, split, or withdraw from fasteners. The connection must consequently be protected through sufficient wood cover, noncombustible protection, tested assemblies, or an approved engineering analysis demonstrating acceptable connection temperatures and capacity for the entire required duration.

A three-hour rating is not required merely as a generalized safety factor; the code requires correspondence with the connected elements unless the approved design establishes another condition. A one-hour connection would create a premature weak point in the load path, and a zero-hour rating would be unacceptable simply because the hardware is hidden.

References/Topics: 2021 IBC Section 2304.10.1; fire-resistance rating of mass timber connections; protected concealed steel hardware.

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The permitted reduction is one hour. Table 601 assigns a two-hour base fire-resistance rating to exterior and interior bearing walls in Type IV-C construction. Footnote “a” to the table permits the ratings of the primary structural frame and bearing walls to be reduced by one hour where those elements support a roof only.

Accordingly, a Type IV-C bearing wall that supports only roof construction may be assigned a one-hour rating after application of the permitted reduction. The allowance recognizes that the element is not carrying occupied floor levels above and therefore presents a lower consequence of progressive structural failure than a wall supporting one or more floors.

The reduction is not automatic merely because a bearing wall is located at the upper story. The approved structural documents must establish that the wall supports only the roof and does not carry floor loads, transfer loads, elevated mechanical platforms, occupied rooftop structures, or other construction that invalidates the condition.

Options A and B are not reductions specified by Table 601. Option D would eliminate the entire two-hour rating and is not permitted. The inspector should verify the applicable rating and the precise load path before accepting reduced fire protection at the top story.

References/Topics: 2021 IBC Table 601, Footnote “a”; Type IV-C bearing walls and roof-support rating reduction.

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Option B is correct because the required protection time placed over a mass timber structural connection may be established through a code-recognized fire-resistance evaluation of that protective construction under standard fire exposure.

IBC Section 2304.10.1 regulates connections in Types IV-A, IV-B, and IV-C. The code allows connection fire performance to be demonstrated through testing where the connection is incorporated into the fire-resistance test or through an approved engineering analysis. AWC further clarifies that the protection applied over the connection must provide the necessary protection time and that its performance may be established using the methods recognized by IBC Section 703.3, including testing and engineering analysis based on ASTM E119 or UL 263 performance.

Option A is too narrow: testing an isolated fastener does not establish the fire protection of the entire connection. Options C and D also use the wrong temperature location. Where an engineering-analysis route is used, the temperature criterion applies to the connection itself , including connectors, fasteners, and portions of wood incorporated into the structural connection—not simply to the protected structural element or supported member.

References/Topics: 2021 IBC Section 2304.10.1; Section 703.3; AWC guidance on fire resistance of mass timber connections.

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The construction detail identifies a 1/2-inch tolerance between the steel beam web and the adjacent CLT panel. Therefore, option B is correct.

This is principally a construction-document interpretation question rather than a generic prescriptive IBC dimension. The 2021 IBC does not establish one universal steel-web-to-CLT clearance applicable to every mass timber connection. The required clearance is project specific and is established by the registered design professional through the approved structural drawings and connection details.

The tolerance provides erection clearance for placement of the prefabricated CLT around the steel member while accounting for fabrication and installation variation. It must not be arbitrarily reduced or increased because the gap can affect panel fit, bearing conditions, fastener alignment, fire-protection continuity, acoustic treatment and any specified joint-filling material.

Under the special-inspection framework, the inspector must compare the installed connection directly with the approved construction documents. Any condition that does not maintain the specified 1/2-inch clearance—or any undocumented field modification to the CLT or steel connection—must be reported and resolved through the registered design professional rather than accepted solely on the contractor’s direction.

References/Topics: Approved structural details; 2021 IBC Sections 1704.2 and 1705.5; inspection of mass timber erection, anchorage and connections.