强夯碎石柱法处理淤泥质粘土地基

常规强夯法处理淤泥质粘土地基效果不太理想。本文论述了强夯碎石柱法的原理及应用的可行性,对夯后形成复合地基的沉降、固结,稳定性等问题用多种方法进行了计算,讨论了施工中可能出现的情况。国内外成功的实例表明该法在处理饱和软粘土地基时有着良好的应用前景。     

巨型钢柱空间滞回特性的试验研究

巨型钢柱是巨型钢框架结构的关键受力构件,组成杆件多,构造复杂,建立其空间恢复力模型是进行巨型框架简化弹塑性地震反应分析的必要条件。通过两端简支巨型钢柱在双向水平往复荷载下的伪静力试验,研究了其空间滞回特性和模拟方法,为将巨型钢柱折算为等效单一柱提供了试验依据。     

Simplified seismic fatigue evaluation for rigid steel connections

A simplified fatigue-life model is proposed for assessing the seismic inelastic rotational capacity of steel connections. First relations are developed for rigid steel connections under lateral loading. Next this is extended to account for the effects of the welded steel moment frame (WSMF) connections of the so-called pre-Northridge type. The seismic fatigue theory is validated against experimental results. The experiments were conducted under increasing ductility amplitudcs until the onset of fracture. Miner‘ rule was used to convert the test results to given an equivalent constant amplitude cyclic fatigue life. Satisfactory agreement is obtained when comparing the experimental observations with the theoretical predictions.     

带暗柱Z形短柱抗震性能试验研究

提出了带暗的Z形短柱。通过3根Z形短柱抗震性能的试验研究,分析比较了Z形柱在两个工程轴受力方向的承载力、刚度、延性、滞回曲线和破坏特征,分析了暗柱对提高Z形短柱抗震能力的作用。试验表明加设暗柱后可明显提高Z形截面短柱的抗震性能。     

Control issues relating to real‐time substructuring experiments using a shaking table

Real‐time substructuring is a method of dynamically testing a structure without experimentally testing a physical model of the entire system. Instead the structure can be split into two linked parts, the region of particular interest, which is tested experimentally, and the remainder which is tested numerically. A transfer system, such as a hydraulic actuator or a shaking table, is used to impose the displacements at the interface between the two parts on the experimental substructure. The corresponding force imposed by the substructure on the transfer system is fed back to the numerical model. Control of the transfer system is critical to the accuracy of the substructuring process. A study of two controllers used in conjunction with the University of Bristol shaking table is presented here. A proof‐of‐concept one degree‐of‐freedom mass–spring–damper system is substructured such that a portion of the mass forms the experimental substructure and the remainder of the mass plus the spring and the damper is modelled numerically. Firstly a linear controller is designed and tested. Following this an adaptive substructuring strategy is considered, based on the minimal control synthesis algorithm. The deleterious effect of oil‐column resonance common to shaking tables is examined and reduced through the use of filters. The controlled response of the experimental specimen is compared for the two control strategies. Copyright © 2005 John Wiley & Sons, Ltd.     

An index for describing the core-stone shape in weathered columnar joints

The shape of core-stones remained in the weathering basalt column is an index to classify its weathered degree. In this paper, a roundness index (RI) like the box dimension using in fractal theory, was employed to quantitatively measure the shape of core-stone in various weathering grades. The rounded core-stone that is weathered seriously has a smaller RI value. According to the value of RI, the five classes shown in the Russell–Taylor–Pettijohn chart for visually classifying grain shape is available to approximately determine the weathered grades of core-stones remained in the basalt column in Taiwan. A slump test is preliminarily tested to show the difference in repose angle of a stability slope assembled by the grains in a similar shape. The collection of angular core-stones those are less weathered (with a higher RI value) indeed reveals a greater repose angle.     

淮南寒武纪岩溶陷落柱发育特征及导水性分析

1996年任楼煤矿发生的陷落柱特大突水事故，使“淮南不存在岩溶陷落柱”的认识得到了质疑。通过初步调研，在孔集矿南部的孙家大山一带发现出露于地表的岩溶陷落柱，而谢桥矿煤经三维地震勘探也探测出了发育于寒武纪灰岩中的两个岩溶陷落柱。因其岩溶陷落柱的发育层位、充填物质与华北煤田奥陶纪岩溶陷落柱构成明显的对比。导致了其水文、工程地质特征的特殊性。     

Cyclic tests of post‐tensioned precast CFT segmental bridge columns with unbonded strands

Two ungrouted post‐tensioned, precast concrete‐filled tube (CFT) segmental bridge columns were tested under lateral cyclic loading to evaluate the seismic performance of the column details. The specimens included a load stub, four equal‐height circular CFT segments, and a footing. Strands were placed through the column and post‐tensioned to provide a precompression of the column against the footing. One specimen also contained energy‐dissipating devices at the base to increase the hysteretic energy. The test results showed that (1) both specimens could develop the maximum flexural strength at the design drift and achieve 6% drift with small strength degradation and residual displacement, (2) the proposed energy‐dissipating device could increase energy dissipation in the hysteresis loops, and (3) the CFT segmental columns rotated not only about the base but also about the interface above the bottom segment. This study proposed and verified a method to estimate the experimental flexural displacement using two plastic hinges in the segmental column. Copyright © 2005 John Wiley & Sons, Ltd.     

Flexural deformation capacity of rectangular RC columns determined by the CAE method

A non‐parametric empirical approach, called the conditional average estimator (CAE) method, has been implemented for the estimation of the flexural deformation capacity of reinforced concrete rectangular columns expressed in terms of the ultimate (‘near collapse’) drift. Two databases (PEER and Fardis), which represent subsets of the original databases, were used. Four input parameters were employed in the basic model: axial load index, index related to confinement, shear span index, and concrete compressive strength. The results of analyses suggest that, in general, ultimate drift decreases with increasing axial load index, and increases with better confinement. An increase in the shear span‐to‐depth ratio has a beneficial effect until a turning point is reached. After that the opposite trend can be observed, i.e. a decrease in the ultimate drift with further increasing of the shear span‐to‐depth ratio. No clear trend is observed in the case of concrete compressive strength. The predictions, obtained by using the Fardis database are in general somewhat larger than the predictions from the PEER database, due to the difference in the definition of ultimate drift. The scatter of results is large. The local coefficient of variation, which is a measure for dispersion, amounts to about 0.2–0.5. The ultimate drifts obtained by using the two databases, were compared with the values predicted by the Eurocode 8 empirical formula. Copyright © 2006 John Wiley & Sons, Ltd.