Web opening regions in composite beams present unique stress conditions, yet dedicated connector types are still lacking. Although stud connectors are the most commonly used composite connectors, their structural characteristics make them unsuitable for the complex stress state in the web opening region. In light of this, this paper proposes introducing the Perfobond Strip (PBL) connector into the web opening region of steel-concrete composite beams for the first time. By leveraging the performance advantages of the PBL connector, the adverse effects caused by the web opening are mitigated, enabling effective shear force transfer and enhancing the composite action in the opening region. Beam tests and validated finite element simulations are systematically analyzed, and the underlying factors leading to the observed effects are explored. The results indicate that the web opening significantly alters the stress state, with the failure mode transitioning to shear-dominated failure. Compared to stud connectors, the PBL connector significantly improves the shear resistance and composite performance in the opening region, increasing the overall beam's deformation capacity by 49.18% and its load-carrying capacity by 26.94%. The internal force distribution is optimized by the PBL connector, which effectively alleviates stress concentration and slip issues in the opening region. Furthermore, drawing on the test data and validated finite-element results, a computational model is formulated for steel-concrete composite beams with web openings incorporating PBL connectors.

This study proposes a novel composite shear connector (CSC) for steel-concrete composite beams with web openings, designed to effectively enhance the connection performance and composite action in the opening regions, thereby improving their overall structural behavior. Monotonic static loading tests were conducted on five composite beams with web openings incorporating CSCs and two reference beams without CSCs, complemented by nonlinear finite element (FE) analyses. The investigation focused on the effects of key parameter variations on the load transfer mechanism of the CSCs and the structural performance of composite beams with web openings. The results indicate that the CSCs fully mobilize shear resistance in the opening regions, and that increasing the thickness of the vertical connecting plates or the number of transverse studs effectively improves both the load-carrying capacity and deformation capacity of composite beams with web openings. However, an excessive number of transverse studs reduces deformation capacity and may induce brittle failure. The CSCs exhibit excellent slip resistance, significantly enhancing the degree of connection and composite action in the opening regions. Furthermore, the CSCs and the concrete flanges jointly resist vertical shear, markedly increasing the vertical shear capacity in the opening regions. The size of the studs on the vertical connecting plates has a pronounced influence on their mechanical performance, whereas the effect of stud position is relatively minor. For design, prioritize plate thickening and stud size to meet capacity and ductility targets, avoid over-studding, and use CSCs to efficiently enhance shear transfer and composite action around web openings.

The precise determination of the critical force for frame structures usually necessitates iteratively solving intricate transcendental characteristic equations. The energy method can approximately calculate the critical force, but it is very difficult to establish and solve the energy equation. In the present study, a model employing a spring-pendulum column is introduced to delineate the internal and external stiffness of a structure. The formula for the separated column's internal and external stiffness is formulated. By exploiting the principle that the internal stiffness equals the external stiffness during frame instability, a practical formula for directly computing the critical bearing capacity of the original frame structure is derived. This methodology significantly streamlines the resolution of the critical force. The formula is an algebraic equation adept at accommodating the story-to-story support effect and the inter-column support effect within the same story. Compared to finite element analysis, this method exhibits excellent precision and accuracy, rendering it suitable for engineering design and theoretical calculations. To summarize, this paper presents a lucid concept and a practical calculation formula for determining the critical force of frame structures. The proposed method streamlines the solution process and resolves several shortcomings of existing approaches, thus making a valuable contribution to the field.

A new type of prefabricated steel truss frame-precast hollow-core concrete composite slab combines advantages of steel truss floor support plate and hollow-core floor slab, an integral part of steel frame flat beam floor system with widened outer overhang at lower flange, resulting in " flat floor without the presence of secondary beams " effect. Composite floor fully assembled by connecting steel clips and pins, energy-consuming components provide self-resetting, self-centering and minimal residual deformation capabilities, facilitating post-earthquake repair and replacement, enhancing seismic resilience. We designed two types of simply supported unidirectional composite plates to investigate static performance, conducted mechanical tests using uniform and concentrated loading methods, studying load-bearing capacity, failure morphology, cracking characteristics, and short-term deformation of specimens including bending, shear, and punching shear resistance. Experimental results compared with theoretical analysis, demonstrating good agreement with errors within 10%. Composite plate exhibited strong load-bearing capacity, with bending resistance borne primarily by combination of concrete and bottom chord steel bars, effectively utilizing material strength. Shear forces primarily carried by steel bars of truss web members, with small contribution from concrete slab. Punching shear resistance mainly provided by several small squares divided by distributed bars between two rows of trusses. Failure mode depended on loading method and cross-sectional size of component. Uniform load distribution and higher truss reinforcement height resulted in increased bending resistance. Failure mode transitioned from bending-shear failure to punching shear failure. Composite slab demonstrated excellent overall deformation capacity. Under concentrated loading, composite slabs exhibited plastic behavior when deflection reached 1/100 of calculated span, and concrete slab was in state of cracking at this point. Under uniform stacking loads, additional load on floor corresponding to deflection reaching 1/250 of calculated span greatly exceeded design capacity requirements specified in standards.

为预估徐变收缩对连续组合梁长期服役期间的潜在影响,考虑两跨连续组合梁邻跨混凝土徐变收缩特性、跨度和荷载互异等情况,基于力法基本原理和混凝土徐变本构方程,对徐变收缩次内力进行分析.结果表明:不考虑收缩影响时,两跨连续组合梁邻跨混凝土徐变特性或跨度相同,中间支座徐变次弯矩为零;邻跨徐变特性和跨度均不同,或邻跨徐变特性和加载方式均不同,中间支座产生随时间变化的徐变次弯矩.考虑收缩影响时,所有工况均产生收缩次弯矩.支座次弯矩的变化程度与两跨的徐变系数差、老化系数差、跨度差、荷载差等因素相关,内力的重新分布从两跨中徐变大的一侧向徐变小的一侧转移,两跨的徐变特性差异越大,重分布值越高,徐变次弯矩越大;反之越小,当两跨的徐变特性差异趋于最小,支座徐变次内力趋于零.支座次弯矩大小受截面内部应力重分布影响,与混凝土徐变系数和老化系数及重分配系数相关.采用所提分析方法可对连续组合梁受截面内和结构外双重耦合的内力进行解析,公式的参数可编制成表格,便于工程应用.

为研究部分剪切连接胶合木-混凝土连续组合梁中抗剪连接件不同分布情况对其受力性能的影响,运用ANSYS有限元软件建立4组模型试件,对抗剪连接件进行分段布置,其他相关参数和条件均保持不变,对4组试件的滑移、挠度和剪力进行建模分析.有限元计算结果表明:抗剪连接件分段布置的3组试件滑移和挠度均比沿全梁等间距布置抗剪连接件的试件小,荷载总量相同时对称集中荷载对组合梁滑移和挠度的影响更大;间距为 150 mm试件(GCB-4)的抗剪连接件布置方式最合适,该试件的界面滑移和挠度最小,且抗剪连接件的分布方式在实际施工时更方便,只需计算出布置区域并按固定间距布置即可.

For the problem of stiffness calculation of a composite slim beam with reinforced concrete composite truss slab as floor slab, the short-term deflection of the slim beam is calculated and analyzed by theoretical and numerical methods. The result shows that the load-deflection curve is linear in the middle span of the composite slim beam, and the cross section of the composite slim beam is the ideal cross section. The stiffness of the composite flat beam can be calculated according to the linear elastic theory. The concrete area is converted into steel beam area by the method of conversion section, and then analyzed by the method of material mechanics. The elastic deflection obtained by the theoretical formula is in good agreement with the finite element analysis. The load – displacement curve of a single span composite slim beam is obtained by numerical simulation using finite element method. The curve is nonlinear. In front of the concrete cracking (the load reaches 25% of the failure load), the curve is accord with the theoretical calculation of the elastic curve, then the curve of the finite element calculation is along the horizontal deviation, especially when the load applied to 45% of the breaking load, then the offset value increase, this match the experimental analysis of the early stage of our research team is good.

This paper presents a new type of composite slim floor beam, determined by combining the results of an experimental study and theoretical analysis of the ultimate flexural strength of slim floor beams. The shear connectors play a significant role in the mechanical properties of this type of composite slim floor beam, because the precast concrete slab is laid on the bottom flange of the steel section and because the upper portion of the steel beam is encased in the cast-in-place concrete slab. To investigate the ultimate flexural strength, three specimens, which included headed studs, transverse steel bar shear connectors and no shear connectors, were tested. Additionally, a detailed numerical analysis was performed to verify the experimental results, which indicated that a higher-strength steel beam and thicker concrete slab can effectively enhance the stiffness and flexural capacity of the composite slim floor beam. Based on plastic mechanics and limit analysis theory, a calculation method was derived to estimate the ultimate flexural strength of a composite slim floor beam, and a comparison between the calculation and experimental results shows that the theoretical results exhibit good agreement with the experimental results, and the proposed analysis method can be used in future studies to gain a better understanding of the ultimate flexural strength of composite slim floor beams.

针对规范计算长度系数法无法考虑框架与剪力墙之间的相互作用、同层柱之间的相互支援以及层与层的支援作用的不足,提出了一种计算框架-剪力墙结构临界力的解析算法.利用“三弹簧-摇摆柱”力学模型作为基本单元来计算单个框架柱的稳定承载力,进而通过基本单元(刚度和荷载)在各楼层内组装,之后再将各楼层的刚度及荷载进行楼层间的组装,将求解框架-剪力墙临界承载力转化为求解结构的楼层抗侧刚度,进而推导了可直接计算有侧移框架-剪力墙临界力的简单实用的计算公式,该公式能考虑这三种支援作用,即同层各柱间的支援作用,楼层间的相互支援作用,以及剪力墙对框架的支援作用,有效地弥补了规范尚无法求解框架-剪力墙临界力的不足.算例计算结果表明:该方法有很好的精度及准确性,可供工程设计使用.

The strength of stratified rocks is closely related to their inherent structural anisotropy, which cannot be accurately represented by the isotropic failure criteria. In this study, the Pietruszczak-Mroz (PM) anisotropic failure criterion was used to describe the directional dependency of strength of stratified rocks. In the meridian plane, the frictional coefficient was established by incorporating an anisotropic variable defined as a joint invariant of fabric and stress tensors. In the deviatoric plane, the anisotropic failure surface was characterized by a smooth shape function of Lode's angle. The material parameters for the failure criterion can be determined using the triaxial test. The PM anisotropic criterion was utilized to predict the anisotropic strength of specific stratified rocks. Analysis of the experimental data validated the assertion that PM anisotropic criterion has excellent ability to model the anisotropic strength features of stratified rocks.

为合理方便地计算支座约束影响下连续组合梁的徐变效应,预估组合梁长期力学性能,基于力法基本原理和混凝土徐变本构方程,分解了连续组合梁截面应力重分布和结构支座约束内力重分布的耦合关系,推导了连续组合梁在支座快速约束和缓慢约束两种情况下的徐变次内力解析公式,并通过理论和数值方法对算例进行分析.计算表明:徐变对支座沉降约束起有利作用,组合梁徐变次弯矩受截面内部应力重分布影响,受重分布系数控制,随组合梁截面混凝土与钢梁的刚度比变化,内部应力和外部内力相互影响,且与徐变系数和老化系数相关.采用该方法可较方便地计算连续组合梁在支座约束变化下的内力,公式推导建立在清晰的力学基础上,计算结果能较有效地反映组合梁力学特征,是对组合梁长期力学性能计算方法的一种有效补充.

A novel approach is proposed to compute the secondary internal forces caused by creep in a continuous steel-concrete composite beam that is constructed through segmented pouring. The key to solving the equations with the force method is related to the computation of the relative rotational angles, and addresses three factors: creep constitutive equations, material components of structures, and time status. Considering the effects of these factors, the relative rotational angles of a plain concrete beam and composite beam are deduced, respectively, based on concrete creep theory, and address two conditions: instantaneous deformability with no creep effect and time-dependent deformability with creep effect. By substituting the corresponding relative rotational angles into the force-method equations, the secondary creep forces are solved. Finally, a time-dependent analysis on a two-span continuous composite beam constructed through segmented pouring is presented. The results show that the negative bending moment at the support of the continuous beam constructed through segmented pouring is smaller than that of a continuous beam constructed through integrated pouring. Due to the effect of concrete creep, the negative bending moment at the support increases with time. The greater the creep effect, the closer the negative bending moment of the segmented-poured beam is to that of the integral-poured beam. It is observed that concrete creep has a significant influence on the deflection of a steel-concrete continuous composite beam. The proposed method is verified by comparing its results with those obtained from detailed finite element analyses. (C) 2020 American Society of Civil Engineers.

建筑砌体结构抗震性能评估,对建筑结构安全的稳定性至关重要.本文从四个方面分析建筑砌体结构抗震性能提升的条件,根据建筑结构的抗震性影响因素,评估抗震能力.构建建筑砌体结构抗震性能的评估BIM指标体系;利用BIM模型中的三角模糊数,定量计算建筑砌体结构抗震性能指标的模糊判断矩阵,得到建筑砌体结构的三角模糊数值,分析筑砌体结构抗震性能指标的单排序情况,结合对建筑砌体结构抗震性能评估体系指标权重系数和单项得分的计算,实现基于BIM的建筑砌体结构抗震性能评估.结合模拟建筑实例分析,利用建筑结构倒塌概率测试建筑砌体结构的抗震性能,并利用评估结果与实际评估结果的拟合度测试提出方法的准确性.实例结果证明,能够准确的得到抗震性能的评估结果.

基于结构平衡稳定状态的物理意义,提出了结构外刚度和内刚度的概念,得到了结构临界稳定状态表达式,利用框架重复单元推导了框架结构整体抗侧刚度的计算公式,获得了可直接计算框架临界承载力的简单实用的计算公式.该公式避免了传统计算长度系数法逐个构件验算的不便,而且可很好地考虑同层柱之间的相互支援以及层与层的支援作用,避免了计算长度系数法可能因此造成的不合理设计,弥补了规范计算长度系数法的不足.算例计算结果表明:该方法具有很好的精度及准确性,而且对复杂的框架结构也具有很好的适用性,可供工程设计及理论计算使用.

In order to establish accurate and effective mechanical models of concrete creep and shrinkage by numerical calculation, the problems of parametric finite element analysis by APDL with ANSYS software and constitutive relations of creep and shrinkage by the creep criterion in the software are discussed. The accuracy of calculating creep coefficient and shrinkage strain by theoretical calculation and numerical simulation is analysed with an example. The calculation results show that the results from the two kinds of methods are in good agreement. It can get very good results to simulate the constitutive relationship of concrete creep and shrinkage by the software, achieving the basic function of accurately describing the long-term deformation effects of concrete. This function is the first and most important step in accurately simulating the long-term effects of complex constructions.

Based on concrete creep mechanics and finite element method, the key influence factors of creep and shrinkage are analysed numerically to evaluate the long-term mechanical properties of the steel-concrete composite beams. A constraint coefficient is adopted to judge the constraint degrees of the steel beam in the composite beam. Finite element analyses are conducted on 8 kinds of sections in the composite beams with different constraint degrees. The analyses indicate the axial and bending rigidities increase with the section height of the steel beam, which lead to an increase in both constraint degrees and distributed internal forces. The final internal forces of the concrete slab decrease and the internal forces of the steel beam increase, that is, the reduced internal forces in the concrete slab are transferred to the steel beam. The variations of deflections also increase with the constrain degrees, which show the same trend when the increase of constraints. It can be seen that the constraint degrees of the steel beam in the concrete are the key influence factors that cause stress redistribution and deformation change of the composite beams.

针对西南地区某公路隧道的钻孔声波监测数据,分析了爆破开挖方式下围岩损伤区的分布特征.基于岩体RMR分值和Q指标值,采用现场声波测试结果,预测隧道开挖损伤区围岩和原岩的变形模量.研究结果可为隧道工程的设计和施工建设提供有益的参考和技术支持.

为改变土木工程专业传统的“纸上设计”的课堂教学模式,以全国大学生结构设计竞赛为依托,以现代土木工程专业大学生合理能力结构模型为导向,将“结构模型设计”纳入常态化的教学课程,在学生中从践行纸质结构设计进入“实战演练”的教学实践环节.该实践课程锻炼和提高了学生的实际操作能力、分析问题能力和组织管理能力,最终形成了教学与竞赛衔接、教赛互动、教学相长的良好局面.

To calculate creep and shrinkage effects of steel-concrete composite beams to forecast their long-term mechanical performances,a new algorithm named direct method was adopted.The material ratios,creep adjustment coefficients and shrinkage adjustment coefficients were derived.The formulas of time dependent stresses were obtained.Hence,cross section stresses of composite beam can be calculated similar to a single material section based on material mechanics theory.The analysis indicates the results of cross section stresses of composite beam by direct method are consistent with that by internal force distribution method.The direct method can be used in a wide range,such as simply supported composite beams,composite beams in frame and pre-stressed composite beams under actions of positive bending moment.It can be adopted to obtain adjustment coefficients,stresses and strains according to the internal force at the composite beam centroid with different constraint and load forms.It is a simple-useful method and supplement for a long-term mechanical calculation theory of composite beam.It can be directly applied in practical engineering calculations.