Journal of Fire Protection Engineering current issue

An Approach for Evaluating the Fire Resistance of CFHSS Columns under Design Fire Scenarios

Fike, R.S., Kodur, V.K.R. — Wed, 18 Nov 2009 06:07:53 PST

The use of concrete filling offers a practical alternative for achieving the required fire resistance in steel hollow structural section columns. However, the current prescriptive-based approach which evaluates fire resistance based on standard fire exposure does not account for realistic fire scenarios in the design of concrete-filled hollow structural section (CFHSS) columns. This article presents a methodology for evaluating the fire resistance of CFHSS columns under design fire scenarios without the need for costly computational models. The proposed approach is a derivative of the equal area concept, and evaluates the equivalent fire resistance of the column by comparing the time temperature curve of the standard fire exposure with that of the design fire exposure. The method has been validated against the results generated from finite element analysis (coupled heat transfer and strength analysis) on numerous CFHSS columns under a large number of design fires. The applicability of the approach in design situations is illustrated through a numerical example, and it is concluded that the proposed approach offers an attractive alternative for deriving equivalent fire resistance of CFHSS columns exposed to design fire scenarios.

Failure Analysis of the World Trade Center 5 Building

LaMalva, K. J., Barnett, J. R., Dusenberry, D. O. — Wed, 18 Nov 2009 06:07:53 PST

This article describes an analysis of the structural collapse that occurred in World Trade Center (WTC) building 5 due to fire exposure on 11 September 2001. It is hypothesized that the steel column-tree assembly failed during the heating phase of the fire. A failure analysis is performed to determine the response of the portion of the building frame that collapsed during the fire ignited by falling debris from the WTC towers. Results from a finite element, thermal-stress model confirm the column-tree failure hypothesis. Based on this model, the authors conclude that the catastrophic, progressive structural collapse occurred ~2 hours into the fire exposure.

The Skip-resistant Sprinkler Concept -- Theoretical Evaluation

De Ris, J. L., Ditch, B., Yu, H.-Z. — Wed, 18 Nov 2009 06:07:53 PST

This article presents a model for the response time of a sprinkler designed to reduce the skipping phenomenon experienced during large-scale fires. The model guides the design of a cylindrical shield intended to reduce drop impingement from nearby operating sprinklers. Several designs are experimentally tested and shown to reduce likely skipping when compared to the same sprinkler without a shield. The model is validated using a laboratory Plunge Tunnel apparatus to measure the effect of the shield on the thermal sensitivity of the sprinkler and its ability to intercept water drops. This work successfully demonstrates that shielding can decrease the response time of a sprinkler in drop-laden gas flow without causing a substantial increase in response time when exposed to a dry-gas flow. This is the first of two articles on the skip-resistant sprinkler concept. The following article evaluates the performance of the shield in actual fires.

The Skip-resistant Sprinkler Concept -- An Experimental Evaluation

Ditch, B., De Ris, J. L., Yu, H.-Z. — Wed, 18 Nov 2009 06:07:53 PST

A sprinkler with a shield designed to mitigate drop impingement from nearby operating sprinklers is shown experimentally to reduce skipping as compared to the same sprinkler without a shield. As described in a companion article, a model for the response time of a shielded sprinkler has been developed and validated with a Plunge Tunnel apparatus. In this article, results from intermediate-scale spray fire tests employing Froude modeling principles with a 1 : 3 scale ratio are used to evaluate sprinkler performance both with and without the shield. By comparing the operation times of adjacent shielded and unshielded sprinklers, the intermediate-scale tests can identify test arrangements where the shielded sprinkler operates while the unshielded sprinkler does not operate. The identified arrangements are then used in a full-scale environment where a series of pan fire tests serve as a proof-of-concept that proper shielding of a sprinkler can reduce skipping in terms of both the sprinkler operation pattern and total number of sprinkler operations. This study successfully demonstrates that proper shielding of a sprinkler can significantly reduce skipping.

Thanks to Reviewers

Wed, 18 Nov 2009 06:07:53 PST