波纹腹板开孔对预应力钢-混凝土组合梁抗火性能影响研究

桥梁工程中为了方便工程检修与管线布设,经常在梁腹板上开孔。为研究腹板开孔对预应力波纹腹板钢-混凝土组合梁抗火性能的影响,按照完全抗剪连接设计了2片承受两点对称集中荷载作用的预应力波纹腹板钢-混凝土简支组合梁,其中一片是预应力波纹腹板开孔组合梁,另一片是预应力波纹腹板无孔组合梁;采用ISO834国际标准升温曲线对其进行了恒载升温耐火试验,同时采用有限元软件ABAQUS对其进行了数值研究。研究结果表明:高温下2类预应力波纹腹板钢-混凝土组合梁均在剪弯区发生剪切屈曲;在截面尺寸和跨度相同条件下,承受相同的绝对荷载时,腹板开孔后的预应力波纹腹板钢-混凝土组合梁相对于后者在临界状态下抗弯刚度降低,抗火性能下降;在高温作用下,腹板开孔波纹腹板钢-混凝土组合梁相对于腹板未开孔波纹腹板钢-混凝土组合梁,预应力拉索的效率更高,下降速率更慢;腹板开孔后的预应力波纹腹板钢-混凝土组合梁,在升温后期其滑移曲线发展速率略高于腹板未开孔钢-混凝土组合梁;对于腹板开孔波纹腹板钢-混凝土组合梁,在未出现腹板局部屈曲截面上,腹板分担的剪力可达截面总剪力的78%;开孔截面的总剪力几乎完全由混凝土板承担;临界状态下钢梁腹板正应力略高于常温下的腹板正应力水平。

Effects of Web Openings on Fire Resistance of Prestressed Steel-concrete Composite Beams with Corrugated Webs

Holes are usually fabricated in the webs of composite beams to maintain bridges and to pass pipelines in bridge engineering. Two simply-supported prestressed composite beams with corrugated webs (PCBCW), one with web opening (PCBCW-O) and another without opening (PCBCW-N), were designed according to full shear connection to investigate the effects of web openings on fire resistance of prestressed steel-concrete composite beams with corrugated webs. In the tests, two concentrated loads were applied to the two beams while they were subjected to furnace temperature of ISO834. In addition, fire resistance of the two tested beams were numerically investigated by ABAQUS software. The results show that the two types of composite beams underwent local shear buckling in the shear flexural zone at high temperature. Under the same cross section, span, and absolute load, the flexural stiffness and fire resistance of PCBCW-O decrease relative to PCBCW-N in the critical state. At high temperature, the efficiency of prestress is higher and the decline rate of the tension in PCBCW-O is slower than that in PCBCW-N. In the later period of the tests, the slip between concrete slab and steel beams of PCBCW-O develops at a slightly higher rate than that of PCBCW-N. For PCBCW-O, the shear force shared by webs can reach 78% of the total section shear in the cross section without local buckling, while the total section force in the opening section is almost entirely borne by the top concrete slab. Under critical condition,the normal stress in the web is slightly higher than that under normal temperature.