Fully bonded prestressed precast concrete (FB-PPC) frames are recognized for seismic resilience and construction efficiency. However, their load-redistribution mechanisms under progressive collapse scenarios remain insufficiently quantified. In this study, two 2-story, 2-bay FB-PPC frames were tested under a middle-column-removal scenario. Different column-top constraint conditions and beam loads were considered. The test results show that the collapse resistance developed through two main stages. In the beam action (BA) stage, flexural action (FA) and compressive arch action (CAA) were mobilized together. In the catenary action (CA) stage, the vertical resistance was mainly provided by the continuous prestressed strands. Finite element models were established and validated against the test results. Parametric analyses show that the bonded strands contributed to both moment transfer and axial force transfer in the BA stage. Stronger column-top constraint improved the resistance in the CAA stage; lateral constraint at the beam ends significantly enhanced the CA resistance. Increasing the number of beam loading points improved the mobilization of strand-concrete bond and enhanced the structural resistance. The comparison between single-story and double-story models further shows that Vierendeel action provided an additional resistance contribution at small and moderate deformations, but its effect became limited in the CA stage. A simplified analytical model was proposed based on sectional force equilibrium, deformation compatibility, bond-slip behavior, and strand kinematics. The model can predict the resistance development throughout the entire process. The comparison with finite element results shows that the proposed method provides good accuracy under different constraint conditions. This study provides experimental evidence, numerical insight, and analytical support for evaluating the progressive collapse resistance of FB-PPC frame systems.

Preventing progressive collapse induced by accidental events poses a critical challenge in the design and construction of resilient structures. While substantial progress has been made in planar structures, the progressive collapse mechanisms of precast concrete spatial structures—particularly regarding the effects of precast slabs—remain inadequately explored. This study develops a refined finite element modeling approach to investigate progressive collapse mechanisms in fully bonded prestressed precast concrete (FB-PPC) spatial frames, both with and without precast slabs. The modeling approach was validated against available test data from related sub-assemblies, and applied to assess the collapse performance. A series of pushdown analyses were conducted on the spatial frames under various column removal scenarios. The load–displacement curves, slab contribution, and failure modes under different conditions were compared and analyzed. A simplified energy-based dynamic assessment was additionally employed to offer a rapid estimation of the dynamic collapse capacity. The results show that when interior or side columns fail, the progressive collapse process can be divided into the beam action stage and the catenary action (CA) stage. During the beam action stage, the compressive membrane action (CMA) of the slabs and the compressive arch action (CAA) of the beams work in coordination. Additionally, the tensile membrane action (TMA) of the slabs strengthens the CA in the beams. When the corner columns fail, the collapse stages comprise the beam action stage followed by the collapse stage. Due to insufficient lateral restraints around the failed column, the development of CA is limited. The membrane action of the slabs cannot be fully mobilized. The contribution of the slabs is significant, as it can substantially enhance the vertical resistance and restrain the lateral displacement of the columns. The energy-based dynamic assessment further reveals that FB-PPC spatial frames exhibit high ductility and residual strength following sudden column removal, with dynamic load–displacement curves showing sustained plateaus or gentle slopes across all scenarios. The inclusion of precast slabs consistently enhances both the peak load capacity and the residual resistance in dynamic collapse curves.

Performance of novel dry prestressed beam-to-column joints in precast concrete frames under vertical loads was investigated by experimental and numerical study. Two single-story and two-span precast concrete frames were tested under ortho symmetric or antisymmetric vertical low cyclic reversed loading on beams. The dry prestressed joints had better load capacities and energy dissipation in the frame under symmetric load, while both frames failed in ductile mode. Then a finite element model was developed based on experiments, by which parametric analysis was done including the tension control stress of prestressed tendons on beam ends and the axial compression ratio on columns. The numerical results revealed that the joint exhibited good mechanical performance with the increased tensile control stress of tendons and axial compression ratio of columns. More rigid behavior of joints appeared with increased tensile control stress, and higher load capacity increased with axial force on columns. These findings provide good evidence for designing dry prestressed joints in precast concrete frame.

Bridge foundation settlement monitoring is crucial for infrastructure safety management, as uneven settlement can lead to stress redistribution, structural damage, and potentially catastrophic collapse. While traditional contact sensors provide reliable measurements, their deployment is labor-intensive and costly, especially for long-span bridges. Current remote sensing methods have not been thoroughly evaluated for their capability to detect and analyze complex foundation settlement patterns in challenging environments with multiple influencing factors. Here, we applied Small Baseline Subsets Synthetic Aperture Radar Interferometry (SBAS-InSAR) technology to monitor foundation settlement of a long-span bridge. Our analysis revealed distinct deformation patterns: uplift in the north bank approach bridge foundation and the left-side main bridge foundation (maximum rate: 36.97 mm/year), concurrent with subsidence in the right-side main bridge foundation and south bank approach bridge foundation (maximum rate: 35.59 mm/year). We then investigated the relationship between these settlement patterns and various environmental factors, including geological conditions, Sediment Transport Index (STI), Topographic Wetness Index (TWI), precipitation, and temperature. The observed settlement patterns were attributed to the combined effects of stratigraphic heterogeneity, dynamic hydrological conditions, and seasonal climate variations. These findings demonstrate that SBAS-InSAR technology can effectively capture complex bridge foundation deformation processes, offering a cost-effective alternative to traditional monitoring methods. This advancement in bridge monitoring technology could enable more widespread and frequent assessment of bridge foundation stability, ultimately improving infrastructure safety management.

In order to explore the crack development, deformation capacity, failure mode and progressive collapse mechanism of the frame under the failure of the bottom side column, a progressive collapse test and theoretical analysis were conducted on a two-story two-span precast prestressed concrete frame. The results show that the structural loading stages include the beam mechanism stage and the collapse stage during the failure of the side column. In the small deformation stage, the structure follows the beam mechanism and exhibits compression arch effect and vierendeel action. In the large deformation collapse stage, the structure does not follow the catenary mechanism and the unbalanced load can be resisted by the bending mechanism and vierendeel action. Concrete cracking and failure were concentrated at the beam-column nodes on both sides of the frame beams adjacent to the failed side column, and the damage to the beam-column nodes of the bottom frame was more serious. The other columns and the beams away from the failed columns were basically intact. Then according to the control section of structural failure and the critical collapse state of the specimen, the computation methods of the collapse resistance and the critical displacement were proposed, respectively.

The shear bond of interface between concrete and basalt fiber reinforced polymer (BFRP) bars during freeze-thaw (F-T) cycles is crucial for the application of BFRP bar-reinforced concrete structures in cold regions. In this study, 48 groups of pull-out specimens were designed to test the shear bond of the BFRP-concrete interface subjected to F-T cycles. The effects of concrete strength, diameter, and embedment length of BFRP rebar were investigated under numerous F-T cycles. Test results showed that a larger diameter or longer embedment length of BFRP rebar resulted in lower interfacial shear bond behavior, such as interfacial bond strength, initial stiffness, and energy absorption, after the interface goes through F-T cycles. However, higher concrete strength and fewer F-T cycles were beneficial for enhancing the interfacial bond behavior. Subsequently, a three-dimensional (3D) interfacial model based on the finite element method was developed, and the interfacial bond behavior of the specimens was analyzed in-depth. Finally, a degradation bond strength subjected to F-T cycles was predicted by a proposed mechanical model. The predictions were fully consistent with the tested results. The model demonstrated accuracy in describing the shear bond behavior of the interface under numerous F-T cycles.

为研究预压装配式预应力混凝土(prestressed concrete,PC)框架的抗连续倒塌能力,文章设计1榀2层2跨预压装配式PC平面框架进行底层边柱柱拆除试验,对其裂缝发展、变形能力、破坏模式进行探究.研究表明,预压装配式PC框架在边柱失效的情况下具有较好的抗连续倒塌能力.在试验加载过程中,框架的混凝土裂缝开展与破坏集中在边柱失效跨内两侧梁端与框架柱牛腿结合部,框架柱以及远离失效边柱的框架梁基本完好.在倒塌阶段时,框架内部的预应力钢绞线产生的轴向拉力为结构提供了较大的承载力;普通钢筋由于在梁柱结合处未贯通,因此并未受拉屈服,贡献的承载力较小,但对抑制框架梁裂缝的开展具有一定的作用.

In general, historical earthquake events have shown that a strong mainshock might trigger several aftershocks, which can cause additional damage and seismic risk to the structures. This work tries to investigate the aftershock duration on seismic fragility of the shield building in consideration of initial damage. For this purpose, a three-dimensional finite element model of shield building is established using a concrete damage plastic model. A series of mainshock-aftershock sequences with different durations are selected and scaled to match the target spectrum. A damage ratio of tensile damage is developed to evaluate the additional damage caused by mainshock and aftershocks. Aftershocks with three durations, namely, 20 s, 40 s, and 60 s, are used to study the effect of initial damage levels and aftershock durations on the accumulative damage and seismic fragility of the shield building. The results indicate that those aftershocks with longer durations may wreak more worse cumulative damage to the post-mainshock damaged structure and significantly affect the probability of exceedance. It is also indicated that the initial damage levels have a significant impact on the fragility curves of the shield building. This work can directly incorporate the influence of mainshock-damaged states into the fragility assessment for Nuclear Power Plant.

The use of welded steel tubes and cementitious grout jackets for strengthening the existing reinforced concrete (RC) columns is an innovative approach, which can substantially enhance the strength of a deficient column without enlarging its cross-sectional area. In this study, an eccentric compressive test of a welded steel tube and cementitious grout jacket retrofitted RC (WSGR-RC) medium-length column was performed to explore the strengthening response of this novel method. A total of 12 eccentrically loaded columns and one axially loaded column were designed to investigate the influence of load eccentricity, area ratio of core concrete, and slenderness ratio on the bearing capacity. Correspondingly, the eccentric compressive performance of the WSGR-RC medium-length columns was analysed in detail using the strength enhancement index, ductility index, filling material contribution ratio, and the M-N curves. The test results revealed that this novel strengthening method could augment the bearing capacity of a deficient RC column. Finally, a simplified calculation method was proposed for predicting the eccentric bearing capacity of the WSGR-RC medium-length column, and the calculated results were found to be in good agreement with the experimental data. This study provides a scientific basis for the application of this novel strengthening method in practical engineering applications.

Stability presents a critical issue for real-time hybrid simulation. Actuator delay might destabilize the real-time test without proper compensation. Previous research often assumed real-time hybrid simulation as a continuous-time system; however, it is more appropriately treated as a discrete-time system because of application of digital devices and integration algorithms. By using the Lyapunov–Krasovskii theory, this study explores the convoluted effect of integration algorithms and actuator delay on the stability of real-time hybrid simulation. Both theoretical and numerical analysis results demonstrate that (1) the direct integration algorithm is preferably used for real-time hybrid simulation because of its computational efficiency; (2) the stability analysis of real-time hybrid simulation highly depends on actuator delay models, and the actuator model that accounts for time-varying characteristic will lead to more conservative stability; and (3) the integration step is constrained by the algorithm and structural frequencies. Moreover, when the step is small, the stability of the discrete-time system will approach that of the corresponding continuous-time system. The study establishes a bridge between continuous- and discrete-time systems for stability analysis of real-time hybrid simulation.

在新时期课程思教育改革的背景下，工程结构抗震是土木工程本科教学的重点。如何坚持以学生为中心，立德树人，教育教学过程中融入思政教育，并激发学生学习工程结构抗震的兴趣，实现以能力为导向的教学目标，探索相应的教学改革和教学设计是十分必要和迫切的。为此，本文以特定章节为例，进行了详细的教学设计，以期将知识传授、能力培养、思想引领融入课程教学的全过程，为社会主义建设培养德才兼备、具有工匠精神、敬业精神、科学精神高素质土木人才。

文章对已有相关试验进行仿真对比,验证仿真的可行性,然后设置多种工况对结构防连续倒塌的影响因素进行对比分析.结果表明:提高混凝土强度与普通钢筋强度可以延缓结构变形,提高梁机制的最大承载力,但是对于悬链线机制与整体结构的防连续倒塌能力贡献较小;提高预应力筋配筋率可以在梁机制与悬链线机制阶段显著提高结构的防连续倒塌能力,而预应力筋张拉控制应力对结构防连续倒塌贡献较小;楼板对结构防连续倒塌有较大的贡献,梁柱节点刚度对结构防连续倒塌无明显贡献,柱失效位置对结构防连续倒塌有重大的影响.

The article uses ABAQUS finite element simulation software to establish an L-shaped plane irregularly pre-pressed assembled PC frame. Setting a variety of working conditions,the mechanism of structural resistance against progressive collapse of the remaining frame structure was studied when removing different load-bearing columns. The results show that the pre-pressed assembly structure can increase the maximum resistance of the structure;the configuration of prestressed steel bars can improve the structural resistance against progressive collapse,and the effect is better in the catenary stage. The failure position of the column has a significant impact on the structural resistance against progressive collapse,and the resistance of the corner column is between the inner column and the long-side center column. The lower the failure position and the earlier the failure time,the larger the failure range.

对一榀二层二跨预压装配式预应力混凝土(PC)平面框架进行了静力拆除底层边柱的试验及理论分析,探究了裂缝发展、变形能力、破坏模式及连续倒塌机理.根据试验框架达到极限承载力时的状态,提出了边柱失效时简化的结构抗力分析模型,并推导出结构抗倒塌极限承载力的计算方法;基于能量法建立近似的动力响应评估模型,根据试验框架静力加载荷载-位移曲线近似得到其在边柱瞬时失效时的动力响应曲线.结果表明:框架的受力过程可分为弹性、弹塑性、塑性铰以及倒塌4个阶段;加载时试件的混凝土裂缝开展及破坏集中在失效边柱相邻区域框架梁两侧梁端结合部,除失效边柱外,其余框架柱以及失效柱远离区域框架梁端基本完好;框架在小变形阶段按梁机制受力,存在压拱效应及空腹效应;在大变形阶段不能按悬链线机制受力,由梁的受弯机制和空腹机制共同抵抗不平衡荷载;边柱失效时预压装配式预应力混凝土框架最大抗力达到60.9 kN,最终倒塌位移为430 mm,梁端转角为10.0°～15.3°,具有较好的抗连续倒塌能力.

为实现知识传授与价值引领相结合的课程思政,推进专业课程的课程思政建设,根据"工程结构抗震设计"课程的教学内容和专业素质要求,充分挖掘课程的思想政治内涵和德育元素,提出了本门课程的课程思政目标和实施思路.结合授课章节内容探索了课程思政目标的设计融入点,将专业知识教育和思想政治教育进行有机融合,提升了思想政治教育的亲和力和感染力,激发专业教师进行思想政治教育的积极性,提高学生学习的主动性和认同度.

为了研究试验中计算延迟的产生及影响,分析了滑移支座试验的计算耗时,并评价了试验的实时性.试验发现,在某些积分步骤中会偶然出现计算延迟,破坏了试验的实时性.计算延迟是由于试验中使用了隐式积分算法,在迭代计算中残差收敛速度缓慢所导致的.计算延迟具有偶然性和随机性,不仅影响了试验构件的加载速率,更使指令位移信号呈S形曲线.该信号命令作动器在短时间内急停急转,作动器需克服巨大的惯性力作用,导致响应延迟显著.通过使用显式积分算法、简化数值模型等方法,可显著减少实时混合模拟的积分计算时间,从而避免了计算延迟现象,保障了试验的实时性.

为了研究再生粗骨料与新浇筑的水泥砂浆间界面的黏结性能,设计了界面黏结抗拉试验和界面黏结抗剪试验,并考虑了水泥砂浆强度、再生粗骨料表面粗糙度以及是否添加苯乙烯/丙烯酸酯类聚合物胶乳对界面黏结抗拉和抗剪性能的影响.在界面黏结抗剪试验中还考虑了界面法向正应力的影响.界面黏结抗拉性能试验结果表明,界面黏结抗拉强度随水泥砂浆水灰比的减小或粗骨料表面粗糙度的提高而提高.同时,界面黏结抗剪性能试验结果表明,当界面倾角小于50°时,界面黏结抗剪试件发生界面剪切破坏,并且水泥砂浆水灰比越小、粗骨料表面越粗糙或界面法向正应力越大,界面黏结抗剪强度越强.最终,基于试验结果分析,获得再生粗骨料与新水泥砂浆间界面的内摩擦角约为30°.

为开拓冷弯薄壁型钢填充墙板在装配式建筑中的应用前景,将冷弯薄壁型钢填充墙板引入装配式混凝土框架中,并对其在地震作用下的共同受力性能进行了研究。在对1榀冷弯薄壁型钢填充墙板-装配式混凝土框架结构以及1榀装配式混凝土空框架结构试验分析的基础上,利用有限元分析软件ABAQUS建立了冷弯薄壁型钢填充墙板-装配式混凝土框架结构的数值模型。展开了冷弯薄壁型钢填充墙板-装配式混凝土框架结构在水平力作用下的全过程受力分析,揭示了结构体系在不同应力阶段的发展过程及典型破坏模式。另一方面,对影响冷弯薄壁型钢填充墙板-装配式混凝土框架性能的8个参数展开了进一步的研究与探讨。试验结果表明,轴压比n、混凝土强度fcs以及轻聚合物填料强度flc为影响框架体系抗剪承载力与抗侧刚度的主要因素。同时,提出了一种冷弯薄壁型钢填充墙板抗侧移刚度的简化计算方法,并通过有限元分析结果验证了其准确性。研究结果将为该结构在实际工程中的应用提供依据。

近年来,我国对装配式建筑的发展给予高度重视和大力支持.与此同时,钢骨混凝土由于其承载力强 、延性好 、刚度强等特点被广泛关注和应用.因此本文提出一种新型预制装配式钢骨接头钢筋混凝土中节点,节点区域钢骨采用螺栓连接.同时本文根据现有研究成果,并充分考虑实际工程的现场施工条件,以及节点的安全性和可靠性.通过ABAQUS有限元软件建立多类型预制装配式钢骨接头钢筋混凝土节点数值模型,以此对该节点的力学性能进行分析.

采用预应力钢筋连接梁柱预制构件能够综合发挥装配式框架和预应力混凝土结构的优点.预压装配式混凝土结构的梁柱节点属于半刚性节点,利用有限元模拟其节点在多遇与罕遇地震作用下的刚度退化情况,并与规范中规定的刚度折减系数进行对比,发现节点的刚度退化是一个动态过程,应对其在不同的阶段采取不同的折减系数进行分阶段的折减,才能体现出节点更真实的刚度退化情况.