部分预应力砼构件按两类极限状态的直接设计

本文提出了部分预应力砼构件基于两类极限状态直接控制的设计方法,并给出了具体的设计公式和设计步骤。同时,还对预应力砼超静定结构中的部分预应力砼构件的设计方法进行了说明。本文方法基本属一次性设计且具有较为经济的特点。     

复杂条件下发挥锚杆支护作用的相关技术

介绍了在特殊地质和开采条件下,发挥锚杆支护作用的几种相关技术。     

Finite element analysis of partly wrinkled reinforced prestressed membranes

Wrinkling is a well known phenomenon experimented by tension membranes in Civil Engineering applications. This paper will present an efficient numerical technique for the computational simulation of such wrinkles in a prestressed membrane. In particular, the relaxed energy approach (Pipkin in IMA J Appl Math 36:85–99, 1986) is particularized for prestressed membranes (Gil in Textile composites and inflatable structures, CIMNE, 2003) undergoing moderate strains. Wrinkling conditions in terms of the Euler-Lagrange finite deformation tensor along principal directions will be obtained. This will provide a framework to describe properly the initial instant when wrinkles start to be encountered in a prestressed Saint Venant–Kirchhoff hyperelastic membrane. Subsequently, a modified Helmholtz’s free energy functional will be introduced with the purpose of describing the modified constitutive behaviour of the continuum after the onset of wrinkling. Consistent derivations of the stress tensor as well as the constitutive tensor will de depicted. The results will be particularized for membranes and cables in a Finite Element discretization basis. Some numerical examples will prove the accuracy and robustness of the described algorithm.     

如何正确地提高轧机工作机座的刚度

本文着重分析和讨论了提高轧机工作机座刚度的三种途径：　合理提高零部件刚度、短应力线机座、预应力机座。指出某些错误概念与问题，阐述了如何正确地提高轧机工作座的刚度。     

PTC预应力管桩在软土地基处理中的施工工艺

结合PTC预应力管桩在沪宁高速公路扩建工程中的应用，从路基底板的施工、PTC预应力管桩的施工方面对其施工工艺进行了介绍，总结了PTC预应力管桩在软土地基处理中的应用优点。     

预应力钢丝用盘条在斯太尔摩控制冷却线的生产实践

介绍高强度、大直径、低松弛预应力钢丝用高碳钢盘条在标准型斯太尔摩控制冷却线的生产实践。内容包括作业线概况、原料准备、工艺制度及实际结果和分析。     

100 t级上仰预应力锚索在积石峡水电站隧洞工程中的应用

上仰预应力锚索较下倾锚索在施工中存在内锚固段灌浆、锚墩头制安等突出问题和困难,在积石峡水电站导流洞与中孔泄洪洞交叉段100 t级上仰预应力锚索施工中,采用高强度低松弛钢绞线自由式预应力锚索、三管两次灌浆、钢结构墩头等工艺和结构,成功解决了上仰预应力锚索施工中存在的问题,取得了良好的效果,可供其他类似工程借鉴使用。     

Factors affecting the external prestressing stress in externally strengthened prestressed concrete beams

The wide use of external prestressing system to strengthen reinforced and prestressed concrete members requires the full understanding of the behaviour of the strengthened members. At ultimate the stress in the external prestressing tendons need to be known in order to calculate the ultimate strength of the strengthened member. Several factors that can influence the increase in the ultimate stress in steel external prestressing tendons have been studied and well understood while the effect of these factors on tendons made from fibre reinforced plastics needs more research.

This research was carried out to study the effect of several factors on the increase in the ultimate stress in external Parafil ropes as well as external steel tendons. These factors were related to the external prestressing system, internal prestressed and ordinary bonded steel, beam geometry and material properties. Also, the accuracy of equations proposed by the Eurocode (EC2), ACI318 and BS8110 to calculate the ultimate stress in external steel and FRP prestressing tendons was examined.

The experimental and the analytical results showed that the studied factors have the same effect on both steel (up to yield) and Parafil ropes though this effect is greater in case of steel tendons. Also, factors such as tendon profile (straight or deviated), high strength of the concrete, effective tendon depth, number of deviators should be taken into consideration when calculating the ultimate stress in the external tendons.     

综述现代预应力技术在我国城市桥梁建设的创新发展

本文回顾和总结了21世纪前10年现代预应力技术在我国城市桥梁建设的创新发展。从设计理念、设计思想上,以及新技术、新材料、新工艺及其应用情况等方面来展示创新情况,并给出了4个典型工程案例。本文对现代预应力技术在城市桥梁建设的应用和发展作出了展望,积极倡议建造反映21世纪第二个10年科技水平的新型桥梁结构,推进我国向世界桥梁建设强国的目标迈进。     

Rheological approach in proportioning and evaluating prestressed self-consolidating concrete

The successful development of self-consolidating concrete (SCC) requires a careful control of rheological properties of matrix. In this investigation, a parametric study was undertaken to evaluate the influence of binder type, w/cm (water-to-cementitious materials ratio), and coarse aggregate type and nominal size on rheology of prestressed SCC. The rheological measurement of the 33 SCC mixtures investigated in parametric study was performed using a modified Tattersall two-point workability rheometer. The yield stress and plastic viscosity values derived from the SCC mixtures were correlated to the various workability test results to identify combinations of rheological parameters necessary to secure adequate filling ability, filling capacity, and stability of SCC for successful casting of prestressed elements. Based on the results, it is recommended that SCC should have a plastic viscosity of 30–70 Pa s and 30–130 Pa s for concrete made with crushed aggregate and gravel, respectively, to ensure proper workability. Higher viscosity levels could lead to limitation in passing ability should be avoided. Better understanding of the rheological parameters that control the workability of SCC is important in developing mix design approaches and interpreting quality control test methods.