Interaction Between Pile-Supported Pier and Bank Slope

- Generally the toe of the bank slope in front of the pile- supported pier has to be dredged to meet the requirements of water depth for the berth of ships, while the top of the slope in rear of the pier must be backfilled and elevated to make connections with land transportation. Then the natural state of equilibrium of the slope is destroyed, and some deformation and displacement are unavoidably induced in the soil mass which will exert an undesirable influence on the pile foundation of the pier. This is a typical problem of the interaction between the so-called "passive pile" and surrounding soil, and has been scarcely studied in the literature of geotechnical engineering. In this paper, field observation, model tests and numerical analysis conducted by the authors to study the interaction between pile-supported pier and bank slope are briefly described and some preliminary results are presented.     

对结构设计中几个问题的浅见

作者对结构设计中一些规范不太明确的问题,如什么是短肢剪力墙较多、地震等级与地震烈度的关系、如何对抗震设防区预制板楼盖加强其整体性等问题,查阅和分析了现有的资料,并提出了自己的看法,可供同行参考。     

Collar performance in bridge pier scour with debris accumulation

The mechanism of bridge pier scour becomes more complex in the presence of debris accumulation upstream of the pier. While using countermeasures may be effective in reducing scour, their efficacy could be undermined in such a situation. The current study investigates the effectiveness of using a collar in the presence of different types of floating debris accumulation in reducing scour around a cylindrical bridge pier with non-cohesive bed sediment. The experimental results reveal that using a c...     

砖砌体农居隔震试验研究

针对广大农村民居低矮房屋抗震能力普遍不足的现状,提出一种新型、经济、简单、可靠的隔震技术:钢筋-沥青复合隔震墩技术。根据相关理论设计了相应的隔震墩试件,进行了足尺农居砌体模型房屋隔震试验研究。结果表明,在加速度峰值0.3 g以下时,隔震墩钢筋处于弹性工作状态,震后能自动复位。隔震墩加速度折减系数在0.15～0.61之间,具有很好的减震效果,并且对高频波形的过滤效果尤为明显。设置隔震墩后上部结构的抗震构造要求可相应降低,将节省的资金用于隔震体系的建设,基本不增加房屋整体造价。     

动水压力对深水桥墩地震响应影响的研究综述

地震激励下处于深水中的桥墩和周围水体的相互作用将对桥梁结构的动力响应产生较大影响。首先对地震作用下水-桥墩的相互作用理论做了概括,给出了动水压力对桥墩的作用效应及各自的适用范围;对主要的三种考虑流固耦合效应的分析方法做了对比,探讨了地震作用下影响水-结构相互作用的主要因素,并对今后的研究提出了建议。     

动水压力作用下深水桥墩非线性地震响应分析

为研究动水压力作用对深水桥墩地震响应的影响,本文分别采用Morison方程和辐射波浪理论建立了动水压力计算方法,分析了动水压力作用对桥墩地震响应的影响;同时分析了考虑材料非线性时动水压力作用对桥墩地震响应的影响。研究表明:动水压力作用增大了桥墩的地震响应,其影响随着相对水深的增加而增强;考虑材料非线性时动水压力对桥墩地震响应的影响,相对线性材料而言有所变化。     

开孔双壁圆形钢吊箱围堰消波效果影响因素分析

跨海大桥桥墩基础施工若采用双壁钢围堰,则在其外壁进行开孔可有效减小波浪力,有利于降低钢围堰的制作造价和提高基础施工的安全性。以某跨海大桥基础施工采用的双壁圆形钢吊箱围堰为研究对象,引入波浪力折减系数K_d对消波效果进行评价,采用数值方法着重分析波浪参数和围堰自身结构设计参数对消波效果的影响规律。结果表明:K_d随波陡增大呈先快后缓的增大趋势,波陡超过0.032后,消波效果基本不再变化;随着相对水深的增大,K_d呈先减小后增大并趋缓的规律,在相对水深d/L约为0.455时取得最小值;K_d随开孔率的增大呈线性减小,开孔率越大,消波效果越好。随着双壁间距s的增大,K_d总体上呈减小趋势,且减小速率先快后慢;双壁间距较小时,开孔的消波作用较弱。开孔率和双壁间距两种因素间存在耦合作用,两者越大,其耦合作用也越强。围堰设计中可适当增大开孔率并选取合适的双壁间距以得到最佳消波效果。     

Clear water scour around a finite array of cylinders

This experimental study presents clear-water scour and deposition patterns around hexagonal arrays of circular cylinders in steady flow conditions. Understanding the scour processes around such configurations could facilitate the design of several hydraulic and marine engineering structures, such as bridge piers and piles. The flow alteration caused by the examined porous obstacles depends on the solid volume fraction of the obstacles and on the angle of attack of the incoming flow, due to the limited number of cylinders constituting the array. Flume experiments with erodible bed were carried out for four array densities (solid volume fractions: 0.14, 0.20, 0.32 and 0.56) under three different orientations (regular, angled and staggered configurations). The scour/deposition characteristics were obtained by means of laser scanner and the results were compared to solid cylinders of equal circumambient diameter. Different angles of attack of the incoming flow lead to different blockage ratios, which have direct impact on the scour characteristics and deposition patterns. The arrays with the higher solid volume fraction generated scour/deposition patterns similar to solid cylinder, while in the arrays with the lower solid volume fractions, local scour around the individual small cylinders became evident. Finally, considering that the load bearing capacity of a pier basically depends on the area of its cross-section, a comparison of the maximum induced scour depth and volume by the cylinder arrays and the solid cylinder with equal solid cross-sectional area is presented, in order to introduce an alternative pier configuration that induces less scour. The results showed that the array of cylinders could generate 27% less scour volume and 22% less scour depth compared to its single solid cylinder counterpart.     

Evaluation of the applicability of pier local scour formulae using laboratory and field data

The reliable estimation of the local scour depth at a bridge pier is essential for proper design and maintenance of bridge piers. Most local scour formulae have been developed based on the results of laboratory experiments. The formulae based on laboratory data do not often produce reasonable predictions for field piers because laboratory investigations are apt to oversimplify or ignore many of the complexities of the flow fields around the bridge piers. Validation of the formulae is necessary in order to ascertain which of the formulae are able to provide reasonable estimates of the local scour depth. In this study, six commonly cited formulae based on laboratory data or field data were selected for validation using 180 laboratory data sets gathered from the literature and 446 field data sets collected from four countries. The six formulae validated in this paper are the Colorado State University (CSU), Neill, Froehlich, Breuser, Laursen, and simplified Chinese formulae. Comparisons between the predicted and measured depths were performed using scour from the laboratory and field data. An artificial neural network technique was also applied in order to compare the tendencies between the field and laboratory data sets.     

浅析断层对青岛海湾大桥一期工程Ⅲ标段工程地质的影响

通过海湾大桥一期工程Ⅲ标段的勘察施工,论证了非活动断层对重要工程稳定性存在一定的影响,特别是对桩基影响更大,提出科学、正确地划分断层的分布以及断层内岩体的破碎情况,是科学合理设计桩基的关键。