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International Concrete Abstracts Portal

Showing 1-5 of 11 Abstracts search results

Document: 

SP255-05

Date: 

October 1, 2008

Author(s):

V.K.R. Kodur and N.K. Raut

Publication:

Symposium Papers

Volume:

255

Abstract:

This paper presents the state-of-the-art review and research needs assessment of the fire performance of reinforced concrete (RC) columns. The literature review revealed that almost all of the fire tests have been undertaken on RC columns under standard fire scenarios and were narrow in scope due to limitations in test equipment and loading capacities. There have been limited analytical studies on modeling the fire behavior of RC columns and were mainly based on elemental approach and either neglected spalling or used a very simple and crude model for representing spalling. Most of the current provisions, in codes and standards, for evaluating fire resistance are based on prescriptive approaches and do not include significant parameters that affect fire resistance. Based on this comprehensive review, research needs for developing rational fire design methods for RC columns through a performance-based approach, is highlighted.

DOI:

10.14359/20221


Document: 

SP255-09

Date: 

October 1, 2008

Author(s):

F. Ali and A. Nadjai

Publication:

Symposium Papers

Volume:

255

Abstract:

One of the new techniques to reduce explosive spalling in concrete subjected to fire is to add a cocktail of polypropylene fibers and steel fibers into the concrete mixture. This method is still in the early stages of development and requires more research to investigate the efficiency of introducing such a combination of fibers in reducing explosive spalling in fire. The purpose of this paper is to present the results of an experimental study conducted to investigate the performance of reinforced concrete columns containing steel and polypropylene fibers under different loadings and subjected to severe fire conditions. Two loading levels were investigated representing 0.6 and 0.76 of the ultimate strength limits of ACI 318. Columns containing polypropylene (1 kg/m3) and steel fibers (80kg/m3) showed a higher fire resistance by an average factor of 1.76 compared to columns containing PP fibers (1 kg/m3) only. The paper also assesses the effect of adding steel and polypropylene fibers on the severity of concrete explosion under fire. Measurements of axial displacements and concrete temperatures are presented in this paper. The paper compares the obtained experimental values of the axial displacements with theoretical values calculated using a previously developed simple approach.

DOI:

10.14359/20225


Document: 

SP255-02

Date: 

October 1, 2008

Author(s):

M. Guerrieri, J. Sanjayan, and F. Collins

Publication:

Symposium Papers

Volume:

255

Abstract:

A hydrocarbon fire test was conducted on nine concrete slabs incorporating three different types of binders: 100% ordinary portland cement (OPC), 50% OPC, and 50% ground-granulated blastfurnace slag (GGBFS), and alkali-activated slag (AAS). The specimens (780 mm [30.71 in.] x 360 mm [14.17 in.]) were made with three different thicknesses (100 mm [3.94 in.], 200 mm [7.87 in.] and 400 mm [15.75 in.]). Specimens were tested at an age of six months when the strengths were about 75 Mpa (10,877 psi). The specimens were exposed to the hydrocarbon fire on one side. Explosive spalling only occurred in the 400 mm (15.75 in.) AAS concrete specimen that had a lower moisture content and higher permeability than the OPC and OPC/slag concretes. This suggests that the well-renowned moisture clog theory is unlikely to be a predominant mechanism of spalling in AAS concrete. It is speculated that high thermal gradients caused explosive spalling in the AAS concrete specimen.

DOI:

10.14359/20218


Document: 

SP255-01

Date: 

October 1, 2008

Author(s):

L.T. Phan

Publication:

Symposium Papers

Volume:

255

Abstract:

Effects of elevated temperature exposure and various factors, including water-to-cementitious material ratios (w/cm), curing conditions, heating rates, test methods, and polypropylene (PP) fibers, on (1) pore pressure buildup and potential for explosive spalling and on (2) degradation of mechanical properties in normal-strength (NSC) and high-strength concrete (HSC) are presented. Degradations of mechanical properties were measured using 100 x 200 mm cylinders, heated to temperatures of up to 600 °C at 5 °C/min, and compared with results of other studies and existing codes. Pore pressures were measured using 100 x 200 x 200 mm blocks, heated to 600 °C at 5 °C/min and 25 °C/min. Experimental evidences of the complex, temperature-dependant moisture transport process that significantly influenced pore pressure and temperature developments are described.

DOI:

10.14359/20217


Document: 

SP255-08

Date: 

October 1, 2008

Author(s):

J. Chang, R.P. Dhakal, P.J. Moss, and A.H. Buchanan

Publication:

Symposium Papers

Volume:

255

Abstract:

The connection details of precast, prestressed hollow-core floor units to supporting reinforced concrete beams have a significant influence on the structural behavior of the floor systems during earthquakes. Connections are also one of the most dominant components affecting the fire performance of such floor systems. However, since it is often too complicated to conduct performancebased structural design of hollow-core concrete flooring systems for fire exposure or earthquake attack, engineers are inclined to carry out design using tabulated data and they subsequently overlook the influence of the connections. In this research, an analytical study has been conducted using the finite element tool SAFIR on the structural fire performance of hollow-core floor systems with new connection details that have been experimentally verified to provide better seismic performance. The analytical results show that rotationally rigid end and side connections provide better fire resistance than rotationally flexible connections.

DOI:

10.14359/20224


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