دانلود رایگان مقاله انگلیسی مطالعه تجربی و عددی رفتار خمشی لوله فولادی پرشده با بتن روغن پالم جدید - الزویر 2018

Abstract

Oil palm boiler clinker (OPB) is a waste byproduct obtained at elevated temperature in an oil palm processing mill. Moreover, in recent years, Concrete filled steel tube (CFST) has been used widely in structures throughout the world. This paper presents an experimental and numerical study on novel sustainable composite beam by using OPB as replacement of natural coarse aggregate in CFSTs. Steel hollow beams (3.2m length) infilled with natural aggregate concrete and OPB concrete were subjected to flexural load and elevated temperature. The parameters selected for the experimental tests were the cross-section type (square, rectangular) and the infilling type (natural aggregate concrete and OPB concrete). The thermal response, failure modes, critical temperature, temperature distribution in steel tube and infilled concrete, deflection along the span and fire concrete contribution ratio were evaluated. The critical temperature and fire concrete contribution ratio of OPB CFST was found to be higher than natural aggregate CFST, showing superior performance of OPB CFST. Thereafter, simulations were performed and more than 50 models were analyzed to evaluate the effect of yield strength of steel (235-400 MPa), compressive strength of infilled concrete (30-75 MPa), load ratio (0.3-0.6), width-to-depth ratio (2-0.5) and steel ratio (4.4%-2.1%) on the fire resistance time of CFST beam. It was found that the increase in load ratio, steel ratio and yield strength of steel has adverse effected on the fire resistance (FR) time of CFST member. However, the FR time increased significantly with an increase in compressive strength of infilled concrete and cross-sectional dimension of CFST member. Finally, the experimental results were compared with existing equations for CFST columns filled with natural aggregate concrete. It was found that current equations may underestimate the fire resistance of CFST filled with OPB.

Conclusions

The utilization of agricultural wastes in construction industry would be an ideal choice for sustainable and green construction. The oil palm industry produces a huge amount of solid agricultural wastes including oil palm boiler clinker (OPB). In this paper, a new sustainable and environment friendly composite flexural member with conventional coarse aggregate replaced with OPB was analyzed and its elevated temperature performance was compared with a conventional composite member. Based on experimental and numerical investigation, following conclusions can be drawn:

1. The deflection at any instant of time in OCFST was less than NCFST due to low 620 temperature rise in steel tube and higher contribution of infilled concrete. Moreover, the higher limiting values temperature in OCFST than NCFST reflects better fire resistance of OCFST beams.

2. The critical time of OCFST was 8-10 min higher than NCFST. Similarly, fire concrete 624 contribution ratio of OCFST was found to be 30% higher than NCFST showing superior structural performance of OCFST at elevated temperature.

3. FE model was used to investigate the effect of yield strength of steel, compressive strength of infilled concrete, load ratio, width-to-depth ratio and steel ratio. It was found that by changing the yield strength of steel tube from 235 to 400 MPa, steel ratio from 2.1% to 4.4% and load ratio from 0.3 to 0.6, the fire resistance time of CFST members decreased from 44 to 22 min (50%), 91.6 to 44.4 min (51%) and 44 to 36 min (18%), respectively. However, FR time increased by 57% when the compressive strength of infilled concrete increased from 30 to 75 MPa.

4. The experimental results when compared with existing equations developed for CFST columns filled with natural aggregate concrete indicated that current equations may underestimate the fire resistance of CFST filled with OPB.