立足于解决山区公路建设中有关山区超宽混凝土斜拉桥荷载试验检测的技术难题,依托楠木渡乌江特大桥,将数值模拟、理论分析跟现场试验相结合的手段,对静动载作用下桥梁响应参数变化、承载能力进行分析。通过有限元软件Midas Civil进行建模与理论相结合的方式,得出了斜拉桥索塔偏位工况及塔底弯矩工况,由于影响线布载几乎是全主跨加载,最为不利的结论;通过静载试验,测试控制截面的应变、位移,并与理论值进行对比,对大桥的安全度从静力角度进行评价;通过动载试验,分析了桥梁在动载作用下响应参数的改变,从动力角度对大桥进行评价。试验结果表明,主桥试验桥跨满足设计荷载标准（公路-Ι级）的正常使用要求,为该桥提供相应的桥梁竣工备案与未来养护维修的科学根据。

框架梁体悬空是导致预应力锚索框架支护失效的重要因素之一,研究框架梁悬空对预应力锚索框架内力的影响可为制定框架梁悬空状况评价指标分级标准提供重要依据。文中以贵州省常见公路边坡形式为分析对象,基于FLAC3D建立数值分析模型,通过删除与梁单元节点连接的岩土体单元模拟框架梁悬空,分别建立锚头下方悬空、纵梁和横梁悬臂端悬空、纵梁和横梁跨中悬空5种工况,通过监测数据分析各部位悬空对框架梁梁体弯矩的影响。结果表明,相对于悬臂和跨中悬空,锚头下方悬空造成的框架最大弯矩绝对值增长程度较大,锚头下方悬空对梁体内力的影响大于悬臂悬空和跨中悬空,为最不利悬空位置。

以我国西部地区某库区一深水高墩大跨连续刚构桥梁为工程背景,考虑动水压力、桩-土相互作用以及二者联合作用的影响,确定了六类不同的分析工况,利用OpenSEES源代码分析平台分别建立有限元模型,通过输入两组空间地震波进行非线性时程分析

This paper experimentally studied the shear behavior of corroded post-tensioned prestressed concrete beams with full grouting. The effects of insufficient grouting in shear span on the shear behavior were also investigated. Eight beams were fabricated and divided into two groups: four beams with full grouting and four beams with insufficient grouting. Three beams in each group were subjected to accelerated corrosion. All beams were tested to failure in four-point loading. Experimental data on shear cracking, load-deflection response, shear strength and failure modes were presented. Results showed that strand corrosion accelerated the formation and propagation of diagonal crack. Insufficient grouting decreased the number of diagonal cracks. Strand corrosion degraded the post-cracking stiffness and shear strength. Insufficient grouting aggravated the propagation of diagonal crack and the degradation of post-cracking stiffness. The shear strength of corroded beam with 31.7% corrosion loss decreased by 15.44% as compared to that of the uncorroded beam. Strand corrosion loss less than 31.7% did not change the shear compression failure mode in fully grouted beams. The failure modes of locally ungrouted beams changed from shear compression failure to rupture of wires as the corrosion loss exceeded 39.6%.
© 2020, Korean Society of Civil Engineers.

Bond between seven-wire steel strand and concrete is critical for prestressed concrete structures. In a well-confined condition, the strand pull-out specimen tends to fail with strand rotation instead of directly pulling out from concrete due to its helical-shaped exterior wires. An analytical model, which considers the helical structural features of strand, is proposed to model bond strength for the pull-out failure case including strand rotation. Factors that have been experimentally verified to have influences on bond strength, such as concrete compressive strength, strand diameter and friction coefficient, are reflected and applied into the model through theoretical analysis. Comparison of results between the prediction and experimental results shows that the proposed model can be used to reasonably evaluate the bond strength. For practical design purposes, a simplified equation for transfer length of prestressing strand was proposed indirectly and compared with the current ACI 318 criterion. The proposed transfer length model shows higher safety margin in predicting the experimental results when comparing with that of ACI 318-14 for both 12.7 mm and 15.2 mm prestressing strands.

Concrete cracking induced by strand corrosion can degrade bond strength and lead to prestress loss. A novel model is proposed to predict corrosion-induced prestress loss in pretensioned concrete structures. The coupling effects of concrete cracking and bond degradation are incorporated into the model. An experimental study is conducted to evaluate the effective prestress in eight corroded pretensioned concrete beams under various stress levels. Experimental results are employed to validate the proposed model. Results demonstrate that the proposed model can accurately predict prestress loss in corroded pretensioned concrete structures. Prestress loss depends on the corrosion degree. Corrosion-induced concrete cracking may not degrade bond strength and effective prestress unless corrosion loss exceeds 6.6%. As corrosion further progresses, bond strength and effective prestress decrease monotonically and then reduce to zero when corrosion loss reaches 34.0%.
© 2020 American Society of Civil Engineers.

An experimental test was presented to study the effects of interface orientations on bond strength between old conventional concrete (CC) and new self-consolidating concrete (SCC). A total of 90 specimens were designed and tested using a direct shear test setup. The substrate CC was cast first and exposed to a carbonation chamber for the simulation of aged concrete. The new SCC was then cast on the aged concrete with different mold arrangements to simulate side, bottom, and top bonding interfaces. Effects of bonding interface orientation, concrete strength, and interface treatment on bond strength were clarified. Furthermore, the tested results were compared with the predictions of design codes to verify the applicability of design codes on the cases with different orientations of bonding interface. Results show that interface orientation significantly affects the bond strength between old CC and new SCC. Top bonding interface leads to highest bond strength, followed by side and bottom bonding interfaces. The average reductions of bond strength caused by side and bottom bonding interfaces, respectivety, are 6% and 57% compared to top bonding interface.

为了研究环境温度和混凝土强度对混凝土碳化的影响,在标准快速碳化试验的基础上,设计了不同强度的混凝土试件在不同温度下的碳化试验,明确了温度和强度对混凝土碳化性能的影响。基于实测数据提出了以强度和温度为主要参数的碳化深度预测模型。在该模型的基础上,结合各参数的统计分布特征,分析了混凝土结构碳化失效概率特征。研究表明:环境温度和混凝土强度对混凝土碳化影响显著,温度越高或混凝土强度越低,碳化速度越快,碳化深度也越深。混凝土强度在碳化初期对碳化速率的影响较大,随碳化的加深影响逐渐减小;当温度从20℃提高至30℃时,实测强度为28MPa和34MPa混凝土试件平均碳化深度分别增长约56%和62%;混凝土结构碳化失效概率和可靠指标退化对混凝土保护层厚度最为敏感,其次是混凝土强度和环境温度。

An experimental test is proposed to investigate the interface shear strength between carbonated concrete substrate and self-compacting concrete (SCC) overlay. Thirty-nine Z-type specimens consisting of two L-type concrete members were designed and subjected to direct shear test. One L-type concrete member was cast as substrate and carbonated. Then the SCC was cast as overlay. The effects of carbonation of substrate, strength of SCC overlay, and interfacial treatment on shear strength were discussed and clarified. A coefficient was developed to consider the influence of carbonation on the shear strength prediction between old concrete substrate and new SCC overlay. Results showed that carbonation of substrate affects both the interface shear strength and cracking. The shear strength increased by 30% when the carbonation depth of substrate was deeper than 20 mm. The location of shear crack was changed from the bonding interface to the interface between the carbonated and uncarbonated layers within the substrate. The strength of new self-compacting concrete and the interface treatment also affected the interface shear strength. For specimens without interfacial planted bars, the shear strength increased with the strength of SCC overlay until it was more than 5 MPa greater than that of the substrate. The strength of SCC overlay, however, had negligible effect on the shear strength of specimens reinforced with interfacial planted bars.
© 2020 American Society of Civil Engineers.

以某深水高墩大跨连续刚构桥梁为工程背景,考虑桩-土相互作用（PSI）、动水压力以及二者联合作用效应的影响,基于OpenSEES源代码分析平台建立有限元模型,随机选取100条近场地震波来考虑地震动输入的不确定性,以峰值地面速度（PGV）作为地震动强度参数,然后分别以墩顶、墩底曲率以及支座相对位移作为损伤指标,建立了桥梁不同构件的概率地震需求模型和地震易损性曲线,对深水桥梁的抗震性能进行了分析和评估。研究结果表明:深水桥梁的动水压力效应会增大桥墩的地震失效概率,但支座的失效概率会略有降低;考虑桩-土相互作用时墩底截面和支座的失效概率会有所减小,但墩顶的失效概率会有所增加;动水压力和桩-土相互作用均对支座易损性的影响相对较小;动水压力对高墩桥梁易损性的影响比桩-土相互作用要大。