桩-承台基础相对刚度试验研究

制作了3个九桩承台和1个十六桩承台,采用不同刚度垫块模拟桩刚度的变化,研究了不同承台厚度和桩支撑刚度对承台刚度及其桩顶反力分布的影响。考虑了桩与承台的相互作用,在对试验结果分析的基础上提出了一种新的桩–承台相对刚度表达式。与现有桩筏(箱)基础刚度计算公式进行对比分析,表明按本文推荐公式计算桩-承台相对刚度和桩基承台的刚柔性特征表现出很好的一致性,解决了现有桩筏基础刚度判定公式对刚度较大的桩判别较差的问题,由本文公式可计算出满足刚性条件下所需承台板厚度。

白云石粉掺量对混凝土梁构件受弯性能的影响

为研究白云石粉对高性能混凝土梁构件受弯性能的影响,开展了白云石粉取代水泥用量的混凝土梁构件正截面受弯加载试验研究。通过对比分析4组不同掺量白云石粉(0、3%、5%、10%)混凝土梁构件受弯受力全过程,发现:(1)掺有白云石粉的混凝土梁构件跨中混凝土平均应变仍满足平截面假定;(2)掺有白云石粉的混凝土梁构件受弯破坏均经历弹性、带裂缝工作及破坏三阶段;(3)掺入5%白云石粉能明显降低混凝土梁构件的弹性模量;(4)合理掺量(5%以内)的白云石粉能够提升混凝土梁构件的受弯承载能力。

附加装配式钢管PBL剪力键抗剪承载力研究

组合结构中,传统PBL剪力键容易引起楼板劈裂,进而导致组合楼板弹塑性变形能力降低。为改善组合楼板的承载性能,提出一种改进型剪力键,即附加装配式钢管PBL剪力键。通过建立ABAQUS数值模型,进行了详细的有限元计算与参数分析,考察该类剪力键在整个加载范围内的承载性能,得到该类剪力键的荷载-相对滑移曲线和极限承载力。研究了钢管长度、钢管直径以及孔中贯通钢筋直径等参数对该类PBL剪力键承载性能的影响。研究结果表明,增大钢管直径和增大贯通钢筋直径均能提升该类剪力键的极限承载力,增大钢管直径对承载力的提升更显著,但改变钢管长度对该类剪力键承载力影响不明显。该研究可为该类改进型PBL剪力键的设计提供数据参考。

Complete load transfer behavior of base-grouted bored piles

A field study on the behavior of three destructive piles in soft soils subjected to axial load was presented.All the three piles with different diameters were base-grouted and installed with strain gauges along the piles.The complete load transfer behavior of the base-grouted pile was analyzed using measured results.Moreover,the thresholds of the relative pile-soil displacement for fully mobilizing skin frictions in different soils were investigated,and pile tip displacements needed to fully mobilize tip resistances were analyzed.The results of the full-scale loading tests show that the skin frictions are close to the ultimate values when the pile-soil relative displacements are 1%-3% of pile diameter,and the pile tip displacements needed to fully mobilize the tip resistances are about 1.3%-2.0% of pile diameter.The load transmission curve of the soils around the pile tip corresponds to a softening model when the pile is loaded to failure.

Seismic performance of isolation system of rolling friction with springs

In order to study an isolation system of rolling friction with springs, computer programs were compiled to evaluate the seismic performance based on its movement characteristics. Through the programs, the influences of various seismic performance factors, e.g., rolling friction coefficient, spring constant, were systematically investigated. Results show that by increasing the rolling friction coefficient, the structural relative displacement due to seismic load effectively decreases, while the structural response magnitude varies mainly depending on the correlations between the following factors: the spring constant, the earthquake intensity, and the rolling friction coefficient. Furthermore, increasing the spring constant can decrease the structural relative displacement, as well as residual displacement, however, it increases the structural response magnitude. Finally, based on the analyses of various seismic performance factors subjected to the scenario earthquakes, optimized theoretical seismic performance can be achieved by reasonably combining the spring constant and the rolling friction coefficient.

采用立方体劈拉试件测定混凝土双K断裂参数

与目前常用的三点弯曲梁和楔入劈拉试件相比,中央带有穿透型预制裂缝的立方体劈拉试件具有试件小、轻便、操作简捷、且可忽略试件自重对断裂参数影响等优点。本文采用该试件形式,进行了混凝土断裂试验。试验参数为3种初始缝高比(α0=0.1、0.3、0.5)和4种相对受压荷载分布宽度(β=0.05、0.10、0.15、0.20)。基于双K断裂理论,确定了起裂断裂韧度和失稳断裂韧度的实测值。结果表明:在相同α0下,测定的起裂荷载与峰值荷载的比值与起裂断裂韧度与失稳断裂韧度的比值稳定且变化范围相同;双K断裂韧度与相对荷载分布宽度呈现出线性递增关系,但失稳断裂韧度的增幅较起裂断裂韧度明显;采用立方体劈拉试件试验测定的失稳断裂韧度与初始缝高比无关,而起裂断裂韧度随着初始缝高比的增大而下降。