屈曲约束支撑极限承载力研究方法探讨

屈曲约束支撑极限承载力的研究方法目前集中在试验和理论分析方面,这些技术都是基于对实际结构进行大量的假设和简化,但简化和假设很难完全符合实际,特别是对于支撑的约束条件以及初始缺陷等会影响结构极限承载力的因素。提出用有限元技术来研究初始几何缺陷对屈曲约束支撑极限承载力的影响,以其与试验和理论相佐证。     

Relations of calculated and actual settlement of a thawing foundation bed

Conclusions 1. The dependence of relative compression of thawing soil on pressure is nonlinear, and it is in agreement with views on the nature of deformation of thawing soil. A dominance of natural pressure in the total load on a foundation bed permits one to use the method of unit summation in calculating settlement of nonlinearly deformable soil. Such calculations, as compared with the linear formulas employed in SNiP, give better agreement with actual settlement.2. In calculating settlement of thawing foundation beds, we need differential consideration of soil compressibility with depth, since the combination of genetic features of frozen ground and the increasing natural pressure with depth may create a different inhomogeneity in the foundation bed.Yakutniproalmaz, Mirnyi. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 1, pp. 18–21, January–February, 1975.     

Procedure for predicting settlements of thawing bases for engineering calculations

It was shown that in order to compute the settlement of thawing cohesive soil under a load in time it is necessary to experimentally determine the consolidation coefficient. A procedure is suggested for determining this coefficient, as well as use of the classical solution of a differential equation for seepage consolidation to describe the settlement of soil, thawing of which can occur according to any law.State All-Union Scientific Research Institute of Roads. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 5–7, July–August, 1993.     

A new approach for simulating aerodynamic vibrations of structures in a wind tunnel—development of an experimental system by means of hybrid vibration technique

The present paper describes a newly proposed technique for simulating aerodynamic vibration of structures, which is referred to as the hybrid vibration technique or HVT. This technique is a combination of step-by-step computer calculation and measurement of the aerodynamic force acting on a model structure in a wind tunnel test. Even though the HVT can be applied effectively, problems still exist with respect to obtaining accurate simulations. These problems include response delay in controlling the model behavior and the inertia force component present in the measured aerodynamic force. Techniques for compensating for response delay and for eliminating inertia force from measured aerodynamic force are applied to a developed system based on HVT simulations of aerodynamic vibration of elastic structures and structures exhibiting elasto-plastic behavior are performed by means of the newly developed system. The effectiveness of the techniques for compensating for the response delay and eliminating the inertia force can be confirmed from the results of the simulations. In addition, the possibility and applicability of HVT is indicated.     

Concurrent denitrification and oxygen uptake in microbial films

Mixed microbial films were grown on the inner walls of a tubular reactor with recirculation of the reactor contents and continuous flow-through of nutrient solution. The loss of total oxidized nitrogen was correlated to the film population, the nitrite concentration and the dissolved oxygen concentration in the reactor. When film population was greater than 0.5 × 10⁹ cells cm⁻², reactor dissolved oxygen concentration greater than 1 mg l⁻¹ had little effect on the nitrate loss. Nitrate loss declined for film populations greater than 2 × 10⁹ cells cm⁻². Models based on Monod and zero-order microbial kinetics were calibrated using these data and a nonlinear least squares method. There was little difference in the residual errors with these methods.     

某综合楼的基础设计

介绍了某综合楼工程概况及地质勘察结果 ,针对其地质情况 ,阐述了在对地基基础设计时须解决的三个问题 ,并提出了相应的解决办法 ,经沉降观测 ,商住楼使用良好     

A pore crack model for the mechanical behaviour of porous granular rocks in the brittle deformation regime

A model is developed for predicting and simulating the mechanical behaviour and failure mode of brittle porous granular rocks loaded in compression. It is based on a fracture mechanics analysis applied to cracks emanating from the surface of cylindrical pores in two-dimensional, which is well suited to the microstructure of such rocks. It is also consistent with the usual experimental procedure used for biaxial compression tests since the numerical scheme is implemented under the assumption of imposed axial strain. The model takes into account interactions between neighbouring cracks, which grow when their stress intensity factor reaches the fracture toughness of the rock. The simulation of crack growth from cylindrical holes, associated with a failure criterion based on the coalescence of interacting cracks, allows one to calculate the critical stress at rupture and to derive theoretical stress–strain curves.The present model is then used to compare theoretical results with laboratory data obtained on four sandstones with porosity ranging between 13% and 25.5% which were deformed under conventional triaxial compression conditions at confining pressures between 0 and 35 MPa. The comparison shows that by using a small number of parameters (pore size, pore density, fracture toughness, and elastic moduli), the model is able to predict the rock behaviour during the compression tests and the stress level at rupture in a quite accurate way, when the microstructural parameters introduced are consistent with the observations.     

Analysis and jointing of polygonal road slabs

Conclusions 1. For anlaysis of circular (polygona) slabs which can be included in the category of absolutely rigid slabs, a practical approximate method of analysis has been developed and experimentally verified which permits determining the bending moments under centrally and eccentrically applied loads acting over a small circular area, as well as at any other points in the slab beyond the limits of the loaded area.2. Monolithic bonding of hexagonal road slabs up to 3–4 m² in area designed for the N-30 load results in increased design bending moments and, consequently, in thicker pavements. For these slabs it is expedient to use nonrigid joints, which do not transmit bending or torsional moments; however, these slabs must be placed on stabilized beds and their joints must be filled with waterproofing mastic.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 19–22, September–October, 1974.