姑山矿区多矿床矿产资源开发 利用的综合优化模型研究

依据整体采矿学的理念,即从整体上全过程、多方位、系统和动态地研究一个矿区多矿床矿产资源的开采与利用,构建了人工神经网络专家系统综合优化模型,根据所构建的模型对姑山矿区的多矿床矿产资源开采与利用进行了综合优化研究,得出了姑山矿区的铁矿石推荐生产规模为540×104～680×104 t/a的结论。研究结论对加强姑山矿区的建设、提高经济社会效益以及矿区可持续发展均有较好的指导作用。     

Measurements of wind speed and convective coefficient on the external surface of a low-rise building

Heat transfer between the surface of a building and its surroundings constitutes a substantial proportion of its annual heating energy demand and is made up of radiative and convective components. As the convective component of heat transfer varies with wind speed, a series of experimental measurements were made on a building to estimate the value of the convective heat transfer under a range of wind conditions. A low-rise building was used for the measurements, and strong correlations were obtained between the wind speed and the convective heat transfer coefficient. These results were analysed on a directional basis and with respect to the location of the wind speed measurements, and a series of correlations are presented which compare well with existing data. In conjunction with accurate wind speed data, they can be used to make more realistic estimates of heat transfer from a building.     

±800kV同塔双回输电线路十字组合角钢塔承载力真型试验

SJ30102十字组合角钢塔是我国第1基±800kV直流特高压双回路真型试验塔,塔总高75.5 m,塔重176.8 t。SJ30102试验塔顺利通过了大风、安装、覆冰、断线等7个工况的荷载试验,45°大风超载工况下,加载至设计荷载的134%时,十字组合角钢受压失稳破坏。试验结果表明:主材轴力计算值与试验结果相吻合,计算模型合理;考虑填板布置形式的十字组合角钢稳定承载力计算值与稳定应力实测值吻合较好,计算方法合理准确,DL/T 5154—2012关于十字组合角钢稳定计算方法过于保守;一字型填板布置形式,能够减轻塔重约3%,填板及螺栓计算方法安全可靠;十字组合角钢主材与斜材的新型连接形式,能够提高2个分肢角钢的协同工作性能,受力均匀性较好。     

山区航道机动船消滩水力指标的无因次表达及计算

消滩水力指标一般是指某船舶在额定载重、额定主机功率条件下能够自航上滩的最大航线流速和比降的组合,是判定船舶能否自航上滩的临界水流条件,是急滩整治效果分析的参照依据。分析现有确定急滩消滩水力指标的方法存在的缺陷,指出了现有综合消滩水力指标表达式存在的关键参数选择不合理、影响因子与主变量的关系不明确等不足。基于水流阻力与流速、坡降阻力与比降的基本关系,依据船舶推力与航行阻力平衡的基本原理,从克服现有消滩水力指标计算和表达等不足的角度出发,导出了无因次消滩水力指标的简要表达式和预估公式。应用澜沧江500 t级船舶静水航速实船试验成果,获得了螺旋桨实际转速与额定转速之比随进速系数的变化规律,计算消滩水力指标时,螺旋桨转速不宜取额定转速。分析结果表明,兹万科夫公式计算的水流阻力与船舶推力存在较为明显的偏差,并绘制了阻力修正系数随船舶佛汝德数的修正曲线,指明兹万科夫水流阻力计算公式需根据实船试验成果进行适当修正。分析计算了澜沧江多种机动船型的消滩水力指标,检验了无因次消滩水力指标简要表达式的合理性,采用无因次项的抛物线曲线描述消滩水力指标中流速、比降的关系甚为恰当。基于因次分析原理,通过澜沧江多种机动船消滩水力指标的数值回归分析,建立了无因次综合消滩水力指标与船舶基本参数无因次功载比、方形系数之间的关系式,明显提高了消滩水力指标的计算效率,可在缺乏船型详细资料的情况下预估消滩水力指标。     

不同阻塞条件下的隧道火灾全尺寸试验研究

为了研究阻塞条件下的隧道火灾危险性,选取某隧道网络中的某一支路作为火灾试验区,采用轴流风机通风,额定通风量为27 m3/s,以甲醇池火为火源,火源功率分别为0.25、0.50和1.00 MW。通过改变火源功率和隧道内风门的开闭模式开展全尺寸试验,分析火源横截面和隧道中心线竖直截面风速、隧道纵向拱顶温升、隧道中心面纵向温升等参数,研究了不同阻塞条件下的隧道火灾烟气扩散规律,获得了抑制隧道火灾危险性的风门控制模式。研究结果表明:①在隧道通风网络中,对称风流通过风门后,隧道截面距风门22 m处风速在整流作用下逐渐趋于均匀;②建立了考虑隧道阻塞比的隧道风量衰减模型,该模型可根据隧道阻塞比的变化预测隧道阻塞作用下的风量损失,同时可以计算沿程阻力损失的风量;③在自然通风条件下,当火源功率大于0.50 MW时,火灾烟气在火羽流作用下迅速向隧道拱顶浮动,通过对流换热使得拱顶温度急剧升高,对于隧道结构的稳定性具有巨大的破坏作用;可采用调节风门的方式控制通过起火区域的风量,从而优化隧道火灾危险控制模式,局部风速大小对火灾危险性影响不大;当起火区域风量不足时,人眼高度处的1.8 m高温度升幅较大,不利于人员逃生与救援;④阻塞条件下隧道断面不对称进风流易造成风流结构紊乱,使得隧道火灾烟气温度分布不稳定,危险性较大。     

Time–frequency analysis of structural dynamic characteristics of tall buildings

This study focuses on the correlations between the structural dynamic properties and the instantaneous response characteristics of a 492-m high building during a typhoon. An instantaneous analysis framework is established based on a combined usage of both linear-phase filtering and time–frequency techniques. This analysis framework can separate each modal response contribution without phase distortions. Random decrement technique is used to estimate the modal damping ratios. It is found that beating phenomenon widely exists in the separated modal response contributions, and the damping ratios correlate with the modulation of phase and amplitude within the beating closely. When the beating amplitude comes close to zero, the instantaneous frequency fluctuates evidently. The more intensive this fluctuation is, the larger the damping ratio becomes. An empirical model is presented to formulate the variations of damping ratio and natural frequency of this building with the fluctuation intensity of the instantaneous frequency.     

Simulation of wind loading and response of geometrically non-linear structures with particular reference to large antennas

The study of the response of wind-loaded flexible structures generates several problems, related to the collection of significant experimental data and the modelling of the random wind velocity field, fluid-structure interaction and actual structural behaviour. This paper presents some results of recent research on these problems.

The first part of the paper tackles the modelling and simulation of wind velocity and presents the treatment of some direct measurements on the site of an important broadcasting antenna located on Monte Nerone (Appennine Mountains) on the Italia watershed, 1500 m above sea level.

The second part deals with the problem of determining structural response under wind loading. Because of the impracticability of operating in the frequency domain in the presence of non-linearities, simulation and direct step-by-step integration in the time domain have been chosen. Two specific examples are presented, both pertaining to guyed antennas, for which non-linearities have been shown to be significant. The effects of ice formations on the mast and / orthe stays have also been investigated.     

Evaluation of quarter-scale compartment fire modeling for constant and stepped heat inputs

Quarter-scale tests of ten full-scale room fire tests were conducted by using an existing scaling technique developed at the National Bureau of Standards. Test results confirmed earlier studies which showed that, under constant fire exposure conditions, quarter-scale room testing ranked interior finish materials in the same order as did full-scale tests based on their times to achieve room flashover. In general, quarter-scale tests were less severe and took longer to reach peak room fire buildup because of a lower convective and radiative heat transfer in the quarter-scale room. These tests also generated more CO per unit mass of material and experienced lower combustion efficiencies than did their corresponding full-scale tests.     

Monitoring of dynamic behaviour of super-tall buildings during typhoons

This paper presents the field measurement results of the wind effects on two super-tall buildings (having height over 400 m) in Hong Kong during the passage of Typhoon Nesat in 2011. The field data such as wind speed, wind direction, structural acceleration and displacement responses were simultaneously recorded during the typhoon. Detailed analysis of the field data was conducted to investigate the wind field over an urban area, structural dynamic properties and wind-induced responses of the super-tall buildings. The typhoon-generated wind characteristics including turbulence intensity, gust factor and power spectral density of fluctuating wind speed were presented and discussed. The acceleration responses were analysed by Fourier transform to represent an averaged perspective over the records. Then, the wavelet transform was used to present time-frequency energy distributions of the structural vibrations. Instantaneous spectra were also presented for further discussions of the non-stationary signals. A high-pass Kaiser FIR digital filter was adopted to eliminate the multipath effects on the displacement responses recorded by global positioning system. Then, the resonant and background responses as well as their contributions to the total displacements were identified. Damping ratios of the high-rise structures were evaluated by the random decrement technique, which demonstrated amplitude-dependent characteristics. Finally, the serviceability performance of the super-tall buildings under wind actions with different return periods was estimated.     

软土地区扩底抗拔桩承载特性试验研究

扩底抗拔桩在软土地区的研究与工程应用较少。设计出适合于上海软土地区的扩底形状与机具,并采用现场足尺试验对等截面桩与扩底桩的抗拔承载特性进行了对比研究。试验共分两组,两组试桩的桩长与桩径皆不同。每组试桩由一根等截面桩与二根扩底桩组成。试验表明,扩底抗拔桩的荷载变形曲线相对平缓,表现得更有后劲,极限承载力比等截面桩提高50%以上,扩底效果明显。并对扩底抗拔桩的桩顶和桩端变形随荷载发展规律、桩身变形与回弹规律进行了初步探讨。足尺试验初步验证了上海地区采用小角度扩底抗拔桩的可行性,为认识此类扩底抗拔桩的承载特性并推动其在工程上的应用迈出了第一步。