STRUCTURAL ENGINEERS ASSOCIATION OF HAWAII

STRUCTURAL ENGINEERS ASSOCIATION OF HAWAII (SEAOH)

POSITION STATEMENT

STRUCTURAL EVALUATION OF EXISTING BUILDINGS

January 1996

POSITION STATEMENT

The Building Code of the City and County of Honolulu, as well as other counties in the State of Hawaii, currently do not specify any quantitative criteria for evaluating whether an existing building is structurally "unsafe". The Structural Engineers Association of Hawaii (SEAOH) believes that quantitative criteria establishing a minimum level of structural capacity should be established in order to define structurally "unsafe" buildings.

SEAOH recommends that the following criteria, excerpted with specific modifications from Chapter 3, Section 302 of the Uniform Code for the Abatement of Dangerous Buildings (a companion document to the Uniform Building Code), be used to provide a quantitative definition of a structurally "unsafe" building:

1.: Whenever the stress in any materials, member or portion thereof, due to all dead and live loads, is more than one and one-half times the working stress or stresses allowed in the Building Code for new buildings of similar structure, purpose or location.

2.: Whenever any portion of a building, or any member, appurtenance or ornamentation on the exterior thereof is not of sufficient strength or stability, or is not so anchored, attached or fastened in place so as to be capable of resisting

(i) one half of the wind pressure, or

(ii) one half of the earthquake load for the City and County of Honolulu, or

(iii) two thirds of the earthquake load for all other counties

: of that specified in the Building Code for new buildings of similar structure, purpose or location without exceeding the working stresses permitted in the Building Code for such buildings. (Items (ii) & (iii) are modifications recommended by SEAOH, to reflect the expected earthquake ground motion determined by the Hawaii State Earthquake Advisory Board.)

3.: Whenever any building or structure which, whether or not erected in accordance with all applicable laws and ordinances, has in any non-supporting part, member or portion less than 50 percent, or in any supporting part, member or portion less than 66 percent of the (i) strength, (ii) fire-resisting qualities or characteristics, or (iii) weather-resisting qualities or characteristics required by law in the case of a newly constructed building of like area, height and occupancy in the same location.

BACKGROUND DISCUSSION

Current Code Situation (January 1996)

Honolulu structural engineers currently must comply with the 1991 Uniform Building Code as amended by the City and County of Honolulu. These amendments require that structurally "unsafe" buildings be abated by repair, rehabilitation, demolition or removal. The following passage from Chapter 2 Section 203 on "Unsafe Buildings or Structures" in the 1991 Uniform Building Code (UBC) directs engineers, architects, and owners to the Dangerous Building Code for determining the safety of buildings:

: All such unsafe buildings, structures or appendages are hereby declared to be public nuisances and shall be abated by repair, rehabilitation, demolition, or removal in accordance with procedures set forth in the Dangerous Building Code...

However, the Honolulu amendments removed this reference to the Dangerous Building Code, replacing it with language on City and County Administrative Procedures. This omission of criteria to use for evaluating building structural safety is the issue addressed by this position paper.

Evaluation Criteria and Abatement Requirements

While there is no question that new construction must conform to design standards of the current Building Code, the issue of what standards to use for additions, alterations, or repairs to an existing building is more complicated.

During the planning and design of alterations or additions to an existing building, the structural engineer should determine if the existing building is structurally "unsafe" or if the construction of the proposed alterations and/or additions may result in the existing building becoming structurally "unsafe".

(a): If the existing building is determined to be structurally "unsafe," the building deficiencies should be remedied to comply with the current Building Code before the owner can proceed with the proposed alteration or addition. This requirement is also valid when altering or adding to an existing building could result in it becoming structurally "unsafe."

(b): Alternatively, if an existing building is determined to be structurally adequate, and provided that the alteration/addition will not result in the building becoming structurally "unsafe", only the alteration or addition work needs to conform to the current Building Code. A structural upgrade of the original structure should not be required.

Hawaii has many buildings designed to older codes. While these buildings may not meet current code requirements, they should not be automatically deemed "unsafe." Their classification depends on the criteria used.

The current methodology for evaluating existing buildings relies on the discretion and professional judgment of the structural engineer. As a result, structural engineers might perform such evaluations using a wide range of criteria which may fall between these two extremes:

(a): Use of structural provisions contained in the current Building Code intended for new construction (which may go beyond what is necessary for life safety).

(b): Use of the structural provisions contained in the Building Code in effect at the time of original construction (or the "grandfather clause" approach).

Using the criteria in the current Building Code may result in many of the existing buildings in Hawaii being declared structurally "unsafe." While this may raise the overall level of building safety, it would escalate the need for abatement.

Using the Building Code in effect at the time of original construction might leave many older buildings at risk in the event of a major earthquake or hurricane. The amount of abatement might be reduced, but the risk to human life would remain high.

The criteria which an engineer chooses to use affects the outcome of a building evaluation. An "unsafe" evaluation will clearly impact a project's scope of work and budget, which in turn may affect the project's feasibility.

To control costs, building owners may sometimes "shop" for structural evaluations until they find an engineer who will provide a favorable structural determination for their building, based on the least restrictive criteria. Such "shopping" can circumvent the intent of good professional practice.

1994 Uniform Building Code

Chapter 1 Section 102 of the 1994 Uniform Building Code makes initial reference to the "Dangerous Building Code" as a means for evaluating structurally "unsafe" buildings.

Chapter 34 Section 3401 of the 1994 UBC also provides an important new reference to the Uniform Code for Building Conservation for "comprehensive code and guidelines on the treatment of existing buildings." Chapter 2 Section 206 of this Building Conservation Code defines "unsafe" as follows:

: All buildings or structures regulated by this code which are structurally unsafe or not provided with adequate egress, or which constitute a fire hazard, or are otherwise dangerous to human life are, for the purpose of this section, unsafe.

: All such unsafe buildings, structures or appendages and building service equipment are hereby declared to be public nuisances and shall be abated by repair, rehabilitation, demolition or removal in accordance with procedures set forth in the Dangerous Building Code or such alternate procedures as may have been or as may be adopted by this jurisdiction.

The above section reinforces Section 102 of the 1994 UBC with additional reference to the Dangerous Building Code.

Chapter 4 Section 403 of the Building Conservation Code on "Structural Safety" clearly indicates that the Dangerous Building Code should be consulted:

: A building or structure or its individual structural members that exceed the limits established by the Dangerous Building Code shall be replaced or strengthened in order that the building, structure, or individual structural members will comply with the requirements of the Building Code for new construction...

Section 302 of the Dangerous Building Code (more properly, the Uniform Code for the Abatement of Dangerous Buildings, lists eighteen "conditions or defects" that serve as criteria for identifying "dangerous" or "unsafe" buildings.

The 1994 UBC provides several strong references to the Dangerous Building Code as the intended criterion for identifying "unsafe" buildings. In effect, the 1994 UBC solves the issue of the structural evaluation of existing buildings. The Structural Engineers Association of Hawaii recommends that this intent be followed in the Honolulu Building Code.

CONCLUDING REMARKS

SEAOH considers the act of producing this Position Statement a very important first step towards the goal of developing a consistent and rational standard for determining the structural adequacy of existing buildings. SEAOH hopes that this document will be further improved. It should be expanded in scope to address the following issues:

(a): Should a serious and concerted effort be undertaken by all counties to identify and gradually abate existing dangerous or unsafe buildings? Many older buildings throughout the State of Hawaii have little if only marginal ability to withstand a major earthquake or hurricane wind force. SEAOH can take a proactive role on this issue by i) educating our business and political leaders about the need to identify these older buildings that may present unacceptable risk to human lives in the event of an earthquake or hurricane, and ii) offering to provide technical assistance in the development of an abatement ordinance which balances hazard reduction and economic concerns.

(b): What course of action should the structural engineer take if he discovers structurally dangerous conditions while performing an evaluation of an existing building?

: No existing Building Code provision, state law or county ordinance requires a structural engineer to report the discovery of structurally dangerous or unsafe conditions in existing buildings to local building officials. However, the insurance industry has cautioned that if a building owner fails to report the situation to building officials and the structural engineer does not then make a notification, the structural engineer may be exposed to legal liability.

The above two issues are often referred to as the "abatement of dangerous buildings" or "ADB" issue. The ADB issue focuses on the need for a general effort to mitigate all "unsafe" existing buildings and is concerned with what steps to take after any "unsafe" building conditions have been identified.

Alternative Criteria

The seismic criteria provided by Chapter 3 Section 302 Paragraph 6 of the Uniform Code for the Abatement of Dangerous Buildings may be sufficient for Seismic Zones 1 and 2 (e.g. City and County of Honolulu, Counties of Kauai and Maui). The existing buildings in Seismic Zones 3 and 4 (i.e. Hawaii County) may require more rigorous criteria found in other documents:

(a): The Seismic Design Guidelines for Upgrading Existing Buildings developed by the Departments of the Army, the Navy, and the Air Force describes a methodology based on a dynamic analysis approach to determine whether an existing building possesses adequate post-yield capacity to preclude collapse in the event of a major earthquake.

(b): The NEHRP Handbook for the Seismic Evaluation of Buildings, FEMA-178, describes analysis procedures and acceptance criteria often referenced when evaluating the seismic hazards of existing buildings.

Request for Feedback

The Structural Engineers Association of Hawaii considers this Position Statement to be a dynamic, continuously evolving document, which should reflect the consensus of the structural engineering community. To achieve this, SEAOH encourages its membership to provide feedback so that appropriate changes can be made to this document as required to keep it current and relevant.

SEAOH Committee Members:: Dean Doi (Chair)
: Brian Ide
: Michael Kasamoto
: Afaq Sarwar
: Gary Suzuki
: Ramesh Chandra

REFERENCES

Uniform Code for the Abatement of Dangerous Buildings, International Conference of Building Officials, 1994.
"Seismic Hazard on Oahu, Hawaii, and its Reflection in the Honolulu Building Code," Cox, D.C and Chock, G., Fourth International Conference on Seismic Zonation, Stanford University, California, August, 1991.
Uniform Code for Building Conservation, International Conference of Building Officials, 1994.
TM5-809-10-1/NAVFAC P-355.1/AFM 88-3, Chapter 13, Section A: Seismic Design Guidelines for Essential Buildings, 1986.
TM5-809-10-2/NAVFAC P-355.2/AFM 88-3, Chapter 13, Section B: Seismic Design Guidelines for Upgrading Existing Buildings, 1988.
Building Safety Seismic Council (BSSC) 1992: NEHRP Handbook for the Seismic Evaluation of Buildings, FEMA-178.7. AFM 32-1095, Structural Evaluation of Existing Buildings for Seismic and Wind Loads, 1994.