Adjacent Columns Research Articles

Probabilistic Seismic Performance Assessment of Rocking Buckling Restrained Braced Frames

One of the new lateral force-resisting systems introduced to improve seismic performance of structures is the rocking buckling restrained braced frame (RBRBF). In this system, conventional braces and adjacent columns are designed to remain elastic until near seismic collapse. In this paper, RBRBFs are designed according to a displacement-based design approach. Maximum interstory drift ratio (MIDR) and maximum residual interstory drift ratio (MRIDR) are among the most critical engineering demand parameters (EDPs) used to assess the safety of structures after an earthquake. MIDR is the largest peak interstory drift ratio (IDR) observed among all the stories of a structure. The primary aim of this study is to investigate the effects of utilizing RBRBFs on MIDR and MRIDR responses compared with buckling restrained braced frames (BRBFs). For this purpose, 4-, 8-, and 12-story structures with the RBRBF and BRBF systems are considered, and their collapse capacity values and residual drift capacity values, given different levels of MRIDR, are computed using incremental dynamic analyses (IDAs). After computing the capacity values, the mean annual frequencies (MAFs) of collapse ([Formula: see text]) and exceeding different MRIDR levels ([Formula: see text] are obtained. The results demonstrate that all the RBRBFs have considerably better collapse and residual drift performance than the BRBFs. Based on these results, the use of RBRBF significantly reduces the weaknesses of BRBF including damage concentration in a single story and low post-yield stiffness. Cloud analyses are performed on the structures to investigate the height-wise distributions of peak floor accelerations (PFAs), peak IDRs, and residual interstory drift ratios (RIDRs). The results indicate that the RBRBFs have a uniform height-wise distribution of peak IDR, but the BRBFs have considerable peak IDR concentrations. Furthermore, the RBRBFs have much lower RIDRs than the BRBFs, whereas they experience higher PFAs than the BRBFs. Nevertheless, their PFAs, on average, are not significantly higher than those of the BRBFs.

Dynamic Response and Anti-Collapse Analysis of Multi-Column Demolition Mode in Frame Structures

With the improvement of building safety requirements and the need for risk assessment under extreme conditions such as earthquakes, fires, and explosions, research related to the failure of some key components has received more attention in recent years. The concrete frame is an important and complex research field in structural engineering when analyzing the chain reaction and collapse mode that may occur after the failure or removal of some columns. In order to study the influence of local damage on the stability of the residual structure of a typical frame concrete structure, the dynamic response and collapse resistance of the residual structure of a plane frame structure were analyzed by using the column removal method. Based on LS-DYNA, all working conditions of single column, double column, and multi-column in different demolition positions were designed. By studying the numerical simulation of different adjacent demolition columns and demolition positions, combined with force transmission path analysis and progressive collapse theory, the dynamic response process of damaged structures under different conditions was obtained. Based on the theory of resistance in progressive collapse, the collapse mode and response characteristics of plane frame structures were analyzed. Through the simulation verification of a multi-story frame structure, the dynamic response law under each column removal condition was obtained: with the increase in the number of columns removed, the collapse speed of the building structure and the dynamic response to the remaining structure are enhanced; as the failure column is closer to the center of the structure, the force transmission path of the surrounding structure becomes greater, the resistance provided by the structure increases, the collapse speed becomes slower, the dynamic response range increases, and the progressive collapse of the peripheral column is caused when multiple columns are removed. According to this law, the relationship between the location parameters of the failure column and the vertical displacement and horizontal displacement is established. The results show that the closer the multi-column collapse is to the central area of the structure, the greater the structural response caused by the failure column. Due to the greater constraints and force transmission paths closer to the remaining columns in the center of the structure, it is difficult for the failure structure to eventually cause collapse damage to the central members, and the failure of the secondary external columns close to the external area is more likely to lead to the progressive collapse of the edge structure. The research provides design ideas and insights for the anti-collapse design of frame structures under multi-column demolition conditions. Attention should be paid to the risk of progressive collapse caused by the sub-external area, and this part should be strengthened.

Design of a Fast Image Encryption Algorithm Based on a Novel 2D Chaotic Map and DNA Encoding

ABSTRACTConventional DNA‐based encryption exhibits limited resistance against brute‐force attacks. To enhance image security, we propose an improved image encryption algorithm that integrates two‐dimensional chaotic mapping with optimized DNA encoding. First, a novel two‐dimensional chaotic mapping system is developed. The image is diagonally divided into upper and lower sections. The shorter columns are then systematically inserted into adjacent longer columns. A specialized linking mechanism first stretches the image into a linear sequence and then refolds it into a scrambled image that retains the original dimensions. Subsequently, DNA encoding is employed to induce pixel confusion and diffusion. The encryption key scrambles the original array, thereby enabling base substitution that generates an encoding lookup table. Following DNA‐based pixel encoding, lookup replacement and computational operations are executed prior to final decoding, which completes the encryption cycle. Experimental results confirm the algorithm's advantages, including an expansive key space, exceptional key sensitivity, efficient encryption performance, robust security, and practical implementation feasibility.

The CPAK classification in three-dimensional measurements is consistent with those in two-dimensional measurements.

This study aimed to evaluate whether the coronal plane alignment of the knee (CPAK) classification between three-dimensional (3D) measurement using computed tomography (CT) and two-dimensional (2D) measurement using long leg radiographs (LLR) match. A retrospective radiographic study compared pre-operative CT and LLR measurements in 69 patients undergoing primary total knee arthroplasty. The arithmetic hip-knee-ankle angle (aHKA), joint line obliquity (JLO), and CPAK types were calculated. A match in the CPAK classification was defined as "complete agreement" and agreement was considered partial if the CPAK was located in an adjacent column. If the discrepancy was more than one column, then it was recorded as no agreement. The mean aHKA was -0.6° ± 4.4° in 3D measurement and -1.1° ± 4.3° in 2D measurement (p = 0.42). The mean JLO was 174.2° ± 3.5° in 3D measurement and 175.2° ± 3.6° in 2D measurement (p = 0.07). There was no statistically significant difference in either aHKA or JLO obtained by the two measurement methods, each within 1°. However, the complete agreement was confirmed in only 60.8% of cases. After incorporating even partial agreements including neighboring columns, the agreement rate was 91.2%. The disagreement was noticed in 8.8% of the cases. The 3D measurement method enables aHKA and JLO calculations similar to those of 2D measurements. However, complete agreement with the CPAK classification in all cases was not obtained. On the other hand, 2D measurement has the advantage that JLO can be easily appreciated and remais more intuitive for surgeons. III.

Study on anti-collapse performance of CFST structures under collision load in different cases.

In view of the continuous collapse resistance of the remaining structure under impact column and side columns under vehicle loads, the composite plane frame of concrete filled steel tubes (CFST) was established by using the finite element software ABAQUS, and the orthogonal experimental design and analysis were carried out. Through numerical analysis, the whole process of continuous collapse of the structure caused by low-speed impact is simulated. The research results show that: in the collapse mechanism of the two working conditions, the deformation modes of the impact column and the remaining frame show two modes. According to the fact that the axial force of the adjacent bottom column of the non-impact column increases greatly at first and then tends to be stable after being impacted, the axial force of the non-adjacent bottom column fluctuates up and down around the impact front axle force. Comparing the two working conditions with the direct simulation method (DS) and the alternate path method (AP), the reliability of AP method in evaluating the internal force of the remaining structure under impact load is insufficient, and it is unsafe to judge the collapse degree of the structure. According to the result of range analysis, it can be seen that the velocity is the most important factor to cause the dynamic effect of the remaining structure in the two cases. This study deeply analyzes the influence of the structural damage caused by the low-speed impact of accidents on the continuous collapse of the remaining structures, which has very important theoretical and practical significance for improving the anti-continuous collapse ability of buildings.

Seismic performance and failure mechanisms evaluation of multi-story elliptic and mega-elliptic bracing frames: Experimental and numerical investigation

Seismic performance and failure mechanisms evaluation of multi-story elliptic and mega-elliptic bracing frames: Experimental and numerical investigation

The crystal structure of pezzottaite and the crystal chemistry of the beryl–pezzottaite series

AbstractCrystal structures along the join beryl–pezzottaite have been refined and their compositions determined by electron-microprobe analysis. All crystals show sharp uniform diffraction spots but are microscale mixtures of more than one structure. Three distinct phases were identified with different diffraction characteristics: (1) hexagonal (P6/mcc) Cs-rich beryl; (2) hexagonal–rhombohedral ($R\overline 3 c$) twinned pezzottaite; (3) incommensurate phases with cell dimensions resembling those of beryl with a doubled c-dimension and l indices deviating from integer values by ±0.05–0.10. Beryl (P6/mcc) structures refined to R1 indices from 2.36 to 2.91% and pezzottaite structures refined to R1 indices from 3.31 to 5.83%. In pezzottaite, the Cs1 and Cs2 sites are each occupied by Cs+, Rb+ and (H2O) with Cs+ showing a preference for Cs1; and the Na1 and Na2 sites are occupied by Na+ and Ca2+. Na+ bonds to one (H2O) group and (H2O) bonds to one Na+. The ordering of (Cs+ + Rb+) and (Na+ + Ca2+) in pezzottaite is driven by the incident bond-valence requirements of the anions coordinating the (LiO4) tetrahedron. The valence-sum rule is maintained through the (Cs+ + Rb+) + Li+ → □ + Be2+ variation in beryl by cooperative relaxation of bonds at the Si and Be tetrahedra, and in pezzottaite by cooperative relaxation of bonds at the Si, Al and Li tetrahedra. The valence-sum rule mandates that Na+ must bond to one channel (type-II) (H2O) group which, when combined with the constraint of electroneutrality, requires that compositions along the beryl–pezzottaite join must lie below the line (Cs+ + Rb+) + 2(Na+ + Ca2+) = 1 – 2Ca2+ apfu. The occurrence of an incommensurate phase at intermediate compositions is due to the interaction of the species in adjacent columns of the P6/mcc beryl structure.

Embryo movement is required for limb tendon maturation.

Following early cell specification and tenocyte differentiation at the sites of future tendons, very little is known about how tendon maturation into robust load-bearing tissue is regulated. Between embryonic day (E)16 and E18 in the chick, there is a rapid change in mechanical properties which is dependent on normal embryo movement. However, the tissue, cellular and molecular changes that contribute to this transition are not well defined. Here we profiled aspects of late tendon development (collagen fibre alignment, cell organisation and Yap pathway activity), describing changes that coincide with tissue maturation. We compared effects of rigid (constant static loading) and flaccid (no loading) immobilisation to gain insight into developmental steps influenced by mechanical cues. We show that YAP signalling is active and responsive to movement in late tendon. Collagen fibre alignment increased over time and under static loading. Cells organise into end-to-end stacked columns with increased distance between adjacent columns, where collagen fibres are deposited; this organisation was lost following both types of immobilisation. We conclude that specific aspects of tendon maturation require controlled levels of dynamic muscle-generated stimulation. Such a developmental approach to understanding how tendons are constructed will inform future work to engineer improved tensile load-bearing tissues.

Experimental and theoretical study on axial compression behaviour of the modular combined column

Experimental and theoretical study on axial compression behaviour of the modular combined column

Resilience of code compliant reinforced concrete buildings to progressive collapse: A numerical analysis investigation

Resilience of code compliant reinforced concrete buildings to progressive collapse: A numerical analysis investigation

Hysteresis performance and damage mode of self-centering frame with masonry infill wall: Experimental study assisted with DIC technique

Hysteresis performance and damage mode of self-centering frame with masonry infill wall: Experimental study assisted with DIC technique

Significant Enhancement of Negative Thermal Expansion Under Low Pressure in Cu2P2O7.

Much effort is made to achieve the negative thermal expansion (NTE) control, but rare methods reached the improvement of intrinsic NTE. In the present work, a significantly enhanced NTE is realized in Cu2P2O7 by applying low pressure. Especially, the volumetric coefficient of thermal expansion (CTE) of Cu2P2O7 reached to -50.0×10-6 K-1 (150-325K) under 0.25GPa, which is increased by 47.5% compared to its NTE in a similar temperature range under atmosphere pressure. This character enables a more effective manifestation of the thermal compensation role of Cu2P2O7 in composites. The enhanced NTE mechanisms are analyzed by high pressure synchrotron X-ray diffraction, neutron diffraction at variable temperature and pressure, as well as density functional theory (DFT) calculations. The results show that applied pressure accelerates the contraction of the distance between adjacent CuO layers and CuO columns. Meanwhile, the low-frequency phonon contribution to NTE in α-Cu2P2O7 is improved. This work is meaningful for the exploration of methods to enhance NTE and the practical application of NTE materials.

Study on Vibration Reduction Effect of the Building Structure Equipped with Intermediate Column–Lever Viscous Damper

Generally speaking, the traditional lever amplification damping system is installed between adjacent columns in a building, which occupies a significant amount of space in the building. In contrast to amplification devices in different forms, the damper displacement of the intermediate column damper system is smaller, and the vibration reduction efficiency is lower. In light of these drawbacks, this study proposes a new amplification device for energy dissipation and vibration reduction, which is based on an intermediate column–lever mechanism with a viscous damper (CLVD). Initially, a specific simplified mechanical model of CLVD is derived. Subsequently, an equivalent Kelvin mechanical model of CLVD is derived to intuitively reflect CLVD’s damping and stiffness effect. The damping ratio added by CLVDs to the structure is calculated according to that model; the additional damping ratio and additional stiffness are utilized to calculate the displacement ratio Rd and shear force ratio Rv of the structure with CLVDs to the structure without CLVDs. Rd and Rv are introduced to evaluate the vibration reduction effect of the structure with CLVDs, and the effects of various parameters (such as intermediate column position, beam’s bending line stiffness, lever amplification factor, damping coefficient, and earthquake intensity) on Rd and Rv are analyzed. The results indicate that when the ratio of the distance from the intermediate column to the edge column to the span of the beam is 0.5, CLVD owns the optimal vibration reduction effect. Increasing the beam’s bending line stiffness is beneficial for CLVD to control structural displacement and shear force; when the leverage amplification factor is too large, the CLVD provides the structure with stiffness as the main factor, followed by damping. Additionally, when the ratio of the displacement amplification factor to the geometric amplification factor satisfies fd/γ = 1/21−0.5α, the CLVD has the optimal displacement control effect on the structure. After that, measures are provided to optimize the CLVD in different situations in order to effectively control the inter-story displacement and the story shear force of the structure. Consequently, a nine-story frame is taken as an example to elaborate the application of CLVDs in the design for energy dissipation and vibration reduction. The results reveal that the CLVD scheme adopting the proposed optimization method can effectively enhance the displacement amplification ability of CLVDs, resulting in an additional damping ratio of up to 12%. At the same time, the inter-story displacement was reduced by almost 40% under fortification earthquakes. Through the research in this study, designers can obtain a new choice in structural vibration reduction design.

Experimental study on the hysteretic performance of a self-centering frame infilled with a bamboo wall

Experimental study on the hysteretic performance of a self-centering frame infilled with a bamboo wall

Current opinion on the prospect of mapping electronic orbitals in the transmission electron microscope: State of the art, challenges and perspectives.

The concept of electronic orbitals has enabled the understanding of a wide range of physical and chemical properties of solids through the definition of, for example, chemical bonding between atoms. In the transmission electron microscope, which is one of the most used and powerful analytical tools for high-spatial-resolution analysis of solids, the accessible quantity is the local distribution of electronic states. However, the interpretation of electronic state maps at atomic resolution in terms of electronic orbitals is far from obvious, not always possible, and often remains a major hurdle preventing a better understanding of the properties of the system of interest. In this review, the current state of the art of the experimental aspects for electronic state mapping and its interpretation as electronic orbitals is presented, considering approaches that rely on elastic and inelastic scattering, in real and reciprocal spaces. This work goes beyond resolving spectral variations between adjacent atomic columns, as it aims at providing deeper information about, for example, the spatial or momentum distributions of the states involved. The advantages and disadvantages of existing experimental approaches are discussed, while the challenges to overcome and future perspectives are explored in an effort to establish the current state of knowledge in this field. The aims of this review are also to foster the interest of the scientific community and to trigger a global effort to further enhance the current analytical capabilities of transmission electron microscopy for chemical bonding and electronic structureanalysis.

Study Performance of Floating Columns Subjected to Vertical Loads

In many cases, we need large areas in the building that are free of columns, especially on the lower floors, such as the ground floor and the basement, in order to use them as car parking or otherwise. The load path will change and new terms will appear, including the term ”floating column”, which is the column above the removed column, and the term Transfer beam, is the beam that the floating column is based on it as a concentrated load and then transfers the loads to the adjacent columns. In this paper, the effect of vertical load on a concrete building containing a floating column has been studied and compared to another one without a floating column. Also, the results of the Transfer beam were compared in a number of parameters such as moment, shear force, and deflection. A building consisting of G+4 was studied and analyzed using ETABS, SAFE, and Midas programs, A number of results were reached, the most important is the concept of load path redistribution, also this paper concluded that in normal buildings case all beams have an approximately equal result of bending, shear, and deflection but in floating column building the beams above the Transfer beam have different values which decrease when going upward.

Influence of Staggered Truss on Progressive Collapse-Resistant Behavior of Steel Frame Structures

In order to study the effect of the support mode of a staggered truss system on the continuous collapse resistance performance of a steel structure, four finite element models were established based on the bracing arrangement of a five-story steel frame structure. The situations of different columns on the first floor removed were classified into eight scenarios, and five models of each scenario were analyzed with nonlinear dynamic analyses. Finally, a computational metric based on energy robustness was proposed to evaluate the robustness of the structure. The results of nonlinear dynamic analyses indicated that the staggered truss system significantly improved the resistance to progressive collapse of steel frame structures and effectively increased the redundancy of steel frame structures. All four bracing methods effectively reduced the vertical displacement at the point of failure, with the peak displacement at the point of failure reduced by a maximum of 84 percent and a minimum of 41 percent compared to a pure frame structure. Moreover, the staggered truss system can reduce some axial force peaks in the adjacent columns adjacent to the failed columns. The structural robustness coefficients of Model A, Scheme 1, Scheme 2, Scheme 3, and Scheme 4 are 1.144, 1.339, 1.306, 1.584, and 1.176, respectively, according to the proposed robustness calculation method, which shows that the braced steel frame structure has improved robustness over the original structure. The staggered truss system improves the robustness of the steel frame structure so that the steel frame structure has better resistance to progressive collapse.

Monitoring the changes in the dynamic properties of an RC building experiencing column loss

In this study, an existing six-storey reinforced concrete building with an asymmetric structural plan and soft storey irregularity was used as a test specimen and subjected to three-step progressive structural damages to detect the variations in its dynamic properties. Mode shapes and dominant frequencies of the undamaged building were determined by the ambient vibration survey (AVS) and it was seen that its first three modes were torsion coupled. Besides, soft storey irregularity was evident due to the lack of masonry infill walls on its ground floor. Later on, three-step progressive damages were applied to the building. The first step targeted three columns and one beam of the building, located on a corner region of its ground floor to peel off their clear covers. The second step razed two adjacent corner columns which were already moderately damaged in the first step, while the third step knocked the third moderately damaged column down. After each damage step, AVS was repeated with the same details as applied for the undamaged building. The obtained dynamic properties for the four phases of the building were evaluated with the sustained damage. Numerical analyses with the finite element model of the building representing its four different phases were also performed and the unique responses due to damage effects on the structure were investigated numerically. As a result of induced damage, the quantified amount of frequency change in modes and the new mode observed after particularly column loss scenarios can be utilized for efficient structural health-monitoring strategies of plan-asymmetric buildings and post-earthquake assessment of partially damaged buildings where timely objective assessment is important.

Assessment of Different Methods for Enhancing Progressive Collapse Resistance of Irregular Reinforced Concrete Buildings Using Pushdown Analysis

Ensuring structures meet rigorous structural requirements is paramount in mitigating progressive collapse risk. In this comprehensive investigation, we scrutinize the impact of four distinct mitigation techniques on the propensity for progressive collapse in a six-story building featuring irregular structural attributes. The study adheres to the concrete building construction code ACI 318-14 and evaluates methods that include: (a) reinforcing the reinforced concrete (RC) slab with high-performance fiber-reinforced cementitious composites (HPFRCCs), (b) enhancing the RC slab with carbon fiber-reinforced polymers (CFRPs), (c) incorporating steel plate shear wall (SPSW) within specific columns, and (d) introducing an innovative approach named as the steel belt strip (SBS). In the context of 10 independent column loss scenarios conducted on the first floor, the nonlinear dynamic analysis reveals that HPFRCC effectively reduces vertical displacement under the removed column by up to 99.89% in certain scenarios. Meanwhile, the use of CFRP layers leads to reductions of up to 95% in vertical displacement, but with variations in effectiveness across scenarios. Notably, the SBS technique demonstrates remarkable potential by reducing vertical displacement by 97%, 89%, and 25.9% in different scenarios. This reduction, in conjunction with the mitigation of axial load on adjacent columns, makes the SBS a standout performer. Moreover, pushdown analysis indicates that, with the employment of these mitigation methods, the maximum loading factor can be increased up to 2.14 times in specific scenarios, significantly enhancing the structure’s resistance to progressive collapse. This pioneering research not only bolsters the resilience of irregular RC buildings but also holds profound implications for industry standards, risk assessment, and construction technology innovation.

Collapse-resistant mechanisms induced by various perimeter column damage scenarios in RC flat plate structures

Collapse-resistant mechanisms induced by various perimeter column damage scenarios in RC flat plate structures