Method for preparing a composite membrane/wood floor diaphragm

Abstract

A composite membrane of wood floor diaphragm for construction of new buildings and strengthening of existing buildings to provide improved load transfer capacity and enhanced resistance to gravity and lateral loads, such as earthquake and / or wind for buildings with wood floor framing. The composite membrane extends beneath the wall framing to utilize the composite membrane diaphragm as a load and shear bearing element.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS[0001]This application is a continuation of U.S. application Ser. No. 13 / 294,081, filed Nov. 10, 2011 incorporated by reference in its entirety.FIELD OF INVENTION[0002]In general, this invention relates to the field of building construction. More particularly, the present invention relates to a composite membrane wood floor diaphragm for new buildings and strengthening of the existing buildings to provide improved load transfer capacity and resistance of membrane of wood floor diaphragm to gravity and lateral loads, such as earthquake and / or wind for buildings with wood floor framing.BACKGROUNDWood Structures—Horizontal Diaphragm[0003]According to the American Wood and Forest Association's “Details for Conventional Wood Frame Construction”, wood frame construction continues to be the predominant method of constructing homes and apartments. This is due to the inherent strength and durability of wood frame buildings. Increasingly, wood framing i...

AI Technical Summary

Benefits of technology

This solution significantly improves soundproofing to the high 80s or 90s decibel range, enhances structural integrity by integrating flooring material into the load resistance mechanism, and provides thermal insulation and fire protection, addressing the limitations of traditional wood frame construction methods.

Problems solved by technology

The balloon style of construction has mostly been discontinued due to a number of factors, including, but not limited to the overall low fire resistance and the high cost of lengthy studs, which together inhibits the use of the balloon method of construction in multi-story buildings.

Blocking noise from floor-to-floor is the most common, yet challenging request in soundproofing.

However, flooring products really have a substantial effect only on impact sounds.

1. Use of actual flooring materials as soundproof material. Obviously, and as said in the aforementioned article, different flooring materials have very different sound transfer qualities. Carpet flooring, for an example, is a material with one of the highest soundproof ratings. However, it is highly problematic due to a number of factors, including, but not limited to, the major known issues of indoor air quality, and serviceability issues associated with particle residue retained between the carpet pad and carpet itself. Such residue is known to cause allergies, breathing problems, respiratory infections and asthma. Furthermore, accumulation of moisture and, as a consequence, most likely growing bacteria such as mold that is not removable by means of regular cleaning, creates a major problem for the consumers, not to mention the overall high maintenance factor.

2. Use of sound control underlayment, such as cork or even an engineered noise control insulation mat that is intended to limit only a certain percentage of impact noise between the floors. If sound control underlayment is employed, it is normally installed between the flooring 18 and plywood sheathing 11 (refer to FIGS. 1 to 4). Sound control underlayment is not called out in FIGS. 1 to 4 since it does not embody the industry standard or mandatory requirement in all the typical cases.

3. Interior drywall sheathing 23 per FIGS. 1 to 4 or, in older construction, use of so called acoustic ceiling, also known in the industry as “popcorn ceiling” instead of drywall sheathing 23. The “popcorn ceiling” can be found in some of the older structures since it was popular from the late 1950's through the early 1980's. Even if difficulty in cleaning and the issue of architectural appearance are negated and not considered as main factors against use of acoustic ceilings, the main prohibiting factor against this type of ceiling today is the presence of asbestos.

Interior drywall sheathing 23 itself is not very effective as a primary sound reduction system.

Obviously, such an approach offers a less than desirable solution from both the design gravity load standpoint and the design lateral load increase standpoint.

Although the acoustic engineering society has made attempts in the past to work on finding a solution in form of an improvement in the current state of the art, the building community has created an opposition that has thus far blocked these attempts due to the increase in the cost of construction.

However, a lack of a proper noise blocking barrier can lead to medical problems associated with exposure to noise.

Complications, related to the exposure to certain levels of noise in different environments, may result in an undesirable outcome.

Currently, the industry has not yet offered to the consumer a floor-to-floor noise blocking barrier that can operate in the high 80s decibel range or even 90 decibel range, despite the tendency toward higher population densities in urban areas.

This situation automatically leads to development of higher stresses within the horizontal diaphragm.

This offers an almost cost prohibitive, less than practical solution that also increases the dead load of the structure, inadvertently causing an increase in the design seismic load.

The natural difference in stiffness between the typical 2× joist and a 4× or 3× wood beam used as a joist in case of uniform long floor diaphragm may also invite issues with uneven gravity load distribution and transfer within the floor system, posting unexpected potential issues with overall floor system long term performance.

Obviously, use of 4× or 3× wood beams do not offer an acceptable solution for the issues (1), (2) and (3) above.

Not utilizing flooring as part of the structural system of the building traditionally creates challenges in the industry, including, but not limited to, moot points during the design phase.

Often times, not being able to define and, therefore, not knowing the weight of the flooring material while the architectural design decisions related to the flooring choice has not been made or is being changed numerous times during the design process inserts a definiteness issue between the offices of the architect and the engineer.

This negatively affects both cost of the design and cost of the project during the construction phase.

Conservative design for an additional weight may not always represent the safest and most economical design.

Although the aforementioned document also states that “Diaphragm failures are less commonly observed in earthquakes,” the same document reveals a significant problem related to “the disruption caused by strengthening the diaphragm [that] can be quite significant, so diaphragm rehabilitation is less commonly employed than adding global strength and stiffness, or improving connection paths.”

Although FEMA 547 addresses the existing wood structural panel diaphragm related issues, mentioning that “an issue that often arises is whether existing joists, which are typically thicker than the code assumed 1½″, can count as 3× blocking.

Another problem related to the use of the proposed remedies by FEMA such as the wood structural panel sheathing overlay technique(s) is the imposition of permanent weight (dead load) onto the existing structural system that may be incapable of carrying such additional dead load without strengthening and / or structural alterations.

Without analysis of the existing structure and possible strengthening of the gravity load resisting system of the existing structure, such an increase in dead load creates an additional burden in form of the overstress, excessive deflections, or in some rare cases even a so called near failure state situation within the existing gravity load resisting system that exists in the older buildings.

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