工业建筑中常见结构损伤的原因分析和加固时的注意事项

分析了工业建筑中常见结构损伤的成因,探讨了维修加固处理的原则及加固时应注意的几个注意事项。     

浅谈公路隧道洞口段设计

公路隧道洞口段地质水文条件复杂,洞预埋深浅,围岩自承能力差,在施工中容易出现滑坡、塌方和大变形等情况。本文通过实际的工程设计和施工实践,提出了公路隧道洞口段设计需要着重考虑的因素及技术措施。其中包括不同地质地貌条件下洞门位置的确定、地表加固的作用和方法、洞口边仰坡开挖和加固、超前支护设计等。综合考虑隧道洞口段的各种自然条件,合理运用相应的技术措施,能够保证施工安全和工程质量,并可以节约工程造价。     

The effects of porphyroblast growth on the effective viscosity of metapelitic rocks: implications for the strength of the middle crust

Numerical models are used to examine the effects of porphyroblast growth on the rheology of compositionally layered rocks (metapelites and metapsammites) and by extension the middle crust during prograde metamorphism. As porphyroblast abundance increases during prograde metamorphism, metapelitic layers will strengthen relative to porphyroblast‐free metapelitic units, and potentially relative to quartzofeldspathic metapsammitic units. As metapelitic layers become stronger, the integrated strength of compositionally layered successions increases, potentially causing large volumes of mid‐crustal rock to strengthen, altering the strain‐rate distribution in the middle crust and affecting the geodynamic evolution of an orogenic belt. The growth of effectively rigid porphyroblasts creates strength heterogeneities in the layer undergoing porphyroblast growth, which leads to complex strain‐rate distributions within the layer. At the orogen scale, the strengthening of large crustal volumes (on the order of thousands of cubic kilometres) changes the strain‐rate distribution, which may change exhumation rates of high‐grade metamorphic rocks, the geothermal structure and the topography of the orogen. The presence of a strong zone in the middle crust causes strain‐rate partitioning around the zone, suppressed uplift rates within and above the zone and leads to the development of a basin on the surface.     

Disbond detection with piezoelectric wafer active sensors in RC structures strengthened with FRP composite overlays

The capability of embedded piezoelectric wafer active sensors (PWAS) to perform in-situ nondestructive evaluation (NDE) for structural health monitoring (SHM) of reinforced concrete (RC) structures strengthened with fiber reinforced polymer (FRP) composite overlays is explored. First, the disbond detection method were developed on coupon specimens consisting of concrete blocks covered with an FRP composite layer. It was found that the prescnce of a disbond crack drastically changes the electromecbanical (E/M) impedance spectrum measured at the PWAS terminals. The spectral changes depend on the distance between the PWAS and the crack tip. Second, large scale experiments were conducted on a RC beam strengthened with carbon fiber reinforced polymer (CFRP) composite overlay. The beam was subject to an acccleratcd fatigue load regime in a three-point bending configuration up to a total of807,415 cycles. During these fatigue tests, the CFRP overlay experienced disbonding beginning at about 500,000 cycles. The PWAS were able to detect the disbonding before it could be reliably seen by visual inspection. Good correlation between the PWAS readings and the position and extent of disbond damage was observed. These preliminary results demonstrate the potential of PWAS technology for SHM of RC structures strengthened with FRP composite ovcrlays.     

Performance improvement studies of masonry houses using elastic post‐tensioning straps

Unreinforced masonry houses are composed of building blocks with weak inter‐binding action between them which commonly possess low tensile strength. The principal tensile stresses generated by out‐of‐plane bending and in‐plane shear forces cannot be tolerated well and leads to heavy structural damage and brittle collapse beyond linear capacity of the material. Remedies such as externally applied mesh reinforcement and post‐tensioning improves post and pre‐cracking performances; however, yielding of reinforcement material or shortening of walls due to cracking causes loss of integrity and post‐tensioning force. This paper discusses a research programme on earthquake strengthening of masonry houses using post‐tensioning by elastomeric straps and related shaking table tests on 1/10 scale single storey rural dwelling models. The aim of the study is to assess the use and effectiveness of post‐tensioning rubber straps at several different configurations especially for houses with heavy earth roofs supported on wooden logs. Full‐scale application can be conducted using scrap automobile tyres, which might be implemented as an economic and environment friendly alternative strengthening technique for poor residents of low‐cost dwellings. The performance and validity of the proposed strengthening techniques were tested on 1/10 scale models using a simplistic shaking table. The structural performance of the reinforced models with vertical post‐tensioning rubber straps was significantly improved as compared to the original specimen; the results were even better when vertical and horizontal straps were used. Obtained results show promise for seismic strengthening using rubber straps for post‐tensioning. Copyright © 2006 John Wiley & Sons, Ltd.     

锚固斜孔长螺旋钻进技术研究

分析螺旋叶片的结构参数可为设计提供依据。根据斜孔钻进土屑运移情况，建立力学模型并确定钻进合理工艺参数。提出螺旋钻具设计应注意的问题和施工方法的改进措施。     

Paterns and regularity of ring distribution of seismic activity before great earthquakes in China

ＰａｔｅｒｎｓａｎｄｒｅｇｕｌａｒｉｔｙｏｆｒｉｎｇｄｉｓｔｒｉｂｕｔｉｏｎｏｆｓｅｉｓｍｉｃａｃｔｉｖｉｔｙｂｅｆｏｒｅｇｒｅａｔｅａｒｔｈｑｕａｋｅｓｉｎＣｈｉｎａＳＨＩ－ＲＯＮＧＭＥＩ（梅世蓉），ＺＨＩ－ＰＩＮＧＳＯＮＧ（宋治平）ａｎｄＹＡＮ...     

珠海（磨刀门）大桥震害预测及对策

按《公路工程抗震设计规范》（ＴＪＪ００４－８９）对珠海（磨刀门）大桥进行了抗震鉴定，结果表明大桥满足７度抗震设防要求，最后提出了抗震加固及设计新大桥时可供选用的一些措施。     

强夯法处理大块填石地基加固深度的探讨

在强夯处理大块碎石土地基采用剪切波、雷瑞波、分层沉降检测手段,探讨大块碎石土地基强夯加固深度的确定。     

珠江三角洲软土特性及化学灌浆加固初探

结合淤泥的工程特性和工程要求,选择合理科学的化学灌浆方法,以达到高质量,快速和节省投资的加固目标。