Force Transfer Mechanism Research Articles

Numerical investigation of a novel concrete-to-steel column splice in mixed structures in height

Buildings in which the type of structural material changes between their stories are referred to as mixed-in-height structures. Typically, these buildings have concrete structures in lower stories and steel structures in upper stories. Valuable investigations have been conducted on mixed-in-height structures to explore their seismic response and changes in structural natural period due to the sudden change in the lateral stiffness at transition level and mass irregularity, but scant attention has been given to the connection between steel and concrete structures at varying heights. Given the geometrical limitations of existing concrete structures, the dimensions of steel columns in supplementary stories must align with those of reinforced concrete columns. Consequently, building codes have not yet provided guidelines for proper connection details and effective load transfer from upper steel to lower concrete structures which is crucial due to the abrupt changes in stiffness and force transfer mechanisms in such splice connections. Thus, this study considers Numerical investigation on two full-scale laboratory tested specimens, with similar details but different axial loads, and numerical analysis of a new connection between a concrete and a steel column at the transition level. This research examines the aforementioned connection under two boundary conditions. Furthermore, after validating the numerical models with experimental specimens, axial load parameters, relative percentage of reinforcement to concrete area, and the force–displacement diagrams are presented. Finally, a numerical model of a three-story column in a frame is analyzed using finite element analysis under lateral load, and the sequence of plastic hinge formation is studied. The practicality and effectiveness of the proposed splice was verified herein. Furthermore, the average value of ductility (µ) was calculated to be 5.5, while exhibiting negligible overstrength factor (Ω). Similar response parameters were calculated for F-AL-R2 (43.2 kN/mm, 21.1 kN/mm) and F-AL-R3 (43.8 kN/mm, 22 kN/mm), indicating that the influence of increased rebar percentage diminishes at higher values. The analysis demonstrates that column connection failure did not occur, and the sequence of hinge formation was from top to bottom, validating the suitable performance of the proposed connection.

Force transmission and SUN-KASH higher-order assembly in the LINC complex models

The linkers of the nucleoskeleton and cytoskeleton (LINC) complex comprises Sad-1 and UNC-84 (SUN) and Klarsicht, ANC-1, SYNE homology (KASH) domain proteins, whose conserved interactions provide a physical coupling between the cytoskeleton and the nucleoskeleton, thereby mediating the transfer of physical forces across the nuclear envelope. The LINC complex can perform distinct cellular functions by pairing various KASH domain proteins with the same SUN domain protein. Recent studies have suggested a higher-order assembly of SUN and KASH instead of a more widely accepted linear trimer model for the LINC complex. In the present study, we use molecular dynamics simulations to investigate the mechanism of force transfer across the two proposed models of LINC complex assembly, namely the 3:3 linear trimer model and the 6:6 higher-order model. Employing steered molecular dynamics simulations with various structures using forces at different rates and directions, we examine the structural stability of the two models under various biologically relevant conditions. Our results suggest that both models can withstand and transfer significant levels of force while retaining their structural integrity. However, the force response of various SUN/KASH assemblies depend on the force direction and pulling rates. Slower pulling rates result in higher mean square fluctuations of the 3:3 assembly compared to the fast pulling. Interestingly, the 6:6 assembly tends to provide an additional range of motion flexibility and might be more advantageous to the structural rigidity and pliability of the nuclear envelope. These findings offer insights into how the SUN and KASH proteins maintain the structural integrity of the nuclear membrane.

Material Removal Mechanism and Force Modeling in Ultrasonic Vibration-Assisted Micro-Grinding Biological Bone

Micro-grinding with a spherical grinding head has been deemed an indispensable method in high-risk surgeries, such as neurosurgery and spine surgery, where bone grinding has long been plagued by the technical bottleneck of mechanical stress-induced crack damage. In response to this challenge, the ultrasound-assisted biological bone micro-grinding novel process with a spherical grinding head has been proposed by researchers. Force modeling is a prerequisite for process parameter determination in orthopedic surgery, and the difficulty in establishing and accurately predicting bone micro-grinding force prediction models is due to the geometric distribution of abrasive grains and the dynamic changes in geometry and kinematics during the cutting process. In addressing these critical needs and technical problems, the shape and protrusion heights of the wear particle of the spherical grinding head were first studied, and the gradual rule of the contact arc length under the action of high-speed rotating ultrasonic vibration was proposed. Second, the mathematical model of the maximum thickness of undeformed chips under ultrasonic vibration of the spherical grinding head was established. Results showed that ultrasonic vibration can reduce the maximum thickness of undeformed chips and increase the range of ductile and bone meal removals, revealing the mechanism of reducing grinding force. Further, the dynamic grinding behavior of different layers of abrasive particles under different instantaneous interaction states was studied. Finally, a prediction model of micro-grinding force was established in accordance with the relationship between grinding force and cutting depth, revealing the mechanism of micro-grinding force transfer under ultrasonic vibration. The theoretical model’s average deviations are 10.37% in x-axis direction, 6.85% in y-axis direction, and 7.81% in z-axis direction compared with the experimental results. This study provides theoretical guidance and technical support for clinical bone micro-grinding.

Experimental investigations on the compression capacity of rectangular steel tubular columns strengthened with intermittently welded angle steel

Many steel structure buildings in China were built from the 1970s to the 1980s, and they have been in service for decades. However, due to factors such as changes in their functionality, prolonged disrepair, and erosion of the surrounding environment. Studying the strengthening of many existing steel structures will become an important measure during the “reinforcement period.” Welding angle steel on the surface of steel columns for reinforcement is a commonly used method in practical engineering. However, the traditional continuous welding of angle steel to reinforce rectangular steel tube columns results in a relatively large welding workload on the construction site, extending the construction period and increasing the engineering cost, which cannot guarantee high welding quality. To reduce the workload of on-site welding and the cost of construction reinforcement, intermittent welding is proposed. This article designed 9 test specimens for axial and eccentric compression tests to obtain the failure modes, ultimate bearing capacity, and stress distribution of the cross-section of steel tube columns reinforced with different intermittent welding angle steels. The experimental results indicate that intermittent welding can replace continuous welding for the reinforcement of steel tube columns, significantly reducing on-site welding workload and fully utilizing the role of angle steel reinforcement. If the length of the intermittent welding is too large, local buckling will occur, thereby weakening the reinforcement effect of the angle steel. The existence of batten plates can improve the ultimate bearing capacity of intermittent welded angle steel tube columns. Comparative analysis was conducted using a finite element model, which revealed the force transfer mechanism and ultimate bearing capacity of intermittent welding angle steel reinforced steel tube columns. The optimal weld spacing and weld length for intermittent welding of angle steel to reinforce rectangular steel tube columns provide a theoretical reference for the design and application of practical reinforcement engineering.

Instability mechanism and failure criteria of large-span flexible PV support arrays under severe wind

Compared with independent flexible PV support, the entire structure force performance and transfer mechanism of inter-row cables and inter-span rods of flexible PV support arrays are more complex, it is easy to have large vibration or even instability failure under strong wind. In this study, the three-span and five-row flexible PV support array of a 66 MW Fishery-PV Complementary demonstration site in the eastern coastal region of China is used as the research object. The rigid body pressure measurement wind tunnel test was designed and carried out, and the wind pressure distribution characteristics of the PV panels surface were analyzed. A three-dimensional explicit dynamics model of the flexible PV support array considering inter-row cables and inter-span rods is established, and the wind-induced dynamic response characteristics and instability processes of the large-span flexible PV support array are effectively simulated. Finally, the instability mechanism of the large-span flexible PV support array is revealed, and the dual failure criteria based on structural deformation and energy increment are proposed. Results demonstrated that the maximum values of displacement and von Mises stress of the large-span flexible PV support array are concentrated in the 1st row of the span in the windward side. The array under 0° and 180° wind direction angles induces local instability and failure at wind speeds of 51 m/s and 46 m/s due to the failure of the 1st row of triangular rods and crossed diagonal rods on the windward side, respectively, and the rods instability mechanisms are Eulerian buckling mechanism and Limit point buckling mechanism, respectively. When the axial compression ratio [Δ] > 0.1 or the strain energy increment [ΔU] > 1.0 × 105J of the instability rod, the structure will be locally destabilized. This paper presents a systematic work around the wind-induced response and instability characteristics of the large-span flexible PV support array, the results are of significance for the engineering application of solar energy generation structures.

Experimental analysis on the out-of-plane structural performance of single-face superposed shear walls with different horizontal connections

Single-face superposed (SFS) shear wall is a novel precast concrete sandwich panel (PCSP) wall that can be used as load-bearing walls in high-rise buildings and underground structures in seismic zones. This paper investigates the out-of-plane structural performance of SFS shear walls with different horizontal connections. Three SFS shear walls with different lap-spliced rebar connection configurations at the horizontal connections were designed and tested to compare their out-of-plane structural performance with that of a cast-in-place specimen, in terms of failure modes, cracking patterns, load-displacement curves, stiffness degradation curves, ductility, and force transfer mechanism of lap-spliced rebar connections. The test results showed that the SFS shear wall specimens exhibited and maintained a high level of composite action until failure, and the studied three different horizontal connections can allow effective force transfer between the upper shear walls and the lower. The stiffness, ductility, and ultimate bearing capacities of SFS shear walls under out-of-plane monotonic loading were significantly higher than those of cast-in-place shear walls. The bearing capacity was found to depend to a large extent on the location of additional vertical connecting rebar, the displacement mainly caused by rigid body rotation and related to crack width at joint. A calculation method of the ultimate bearing capacity of a SFS shear wall under out-of-plane horizontal loads was proposed. Finally, some suggestions on the setting of the vertical connecting bar are put forward.

Influence of longitudinal prestress on the shear resistance of prefabricated shear stud connectors

In order to meet the requirements of accelerated bridge construction (ABC), the structure of steel–concrete composite bridges presents a development trend of the entire assembly. A Prefabricated Composite Shear Studs (PCSS) is proposed to speed up the assembly efficiency of traditional steel–concrete composite beams and improve the effectiveness of the prestress of prefabricated concrete decks in the negative moment zone. A finite element model (FEM) of the PCSS shear connector is established by considering the stress characteristics of different assemblies, thirty different steel tendon quantities, and relative arrangements are selected to analyse the impact of longitudinal prestress on the shear resistance of PCSS, the effectiveness of finite element model is verified this through test results. It is revealed that the steel tendon arrangement and quantity will change the shear resistance of the PCSS shear connectors. However, the magnitude, positive and negative effects are related to the position of the steel tendon along the deck height. When the steel tendon deviates downward from the neutral axis of the deck, the shear bearing capacity and shear stiffness increase; in addition, its force transfer mechanism is that the longitudinal prestress changes the lateral restraint effect of the PCSS on the concrete. Under the combined action of prestressing and transverse restraint of steel plate, the cooperative working ability of the stud and surrounding concrete can be enhanced or weakened. Thus, the yielding of stud and concrete damage can be delayed or accelerated, significantly affecting the shear bearing capacity and stiffness.

Shear force transfer efficiency of tapered bridges with trapezoidal corrugated steel webs

This study investigated the shear force transfer mechanism in a prestressed concrete (PC) tapered box girder bridge with trapezoidal corrugated steel webs (TCSWs) throughout the cantilever construction process by theoretical analysis, experimental verification, and finite element (FE) simulation. It has been determined that the assumption made in the current standards that TCSWs completely bear the shear force is inaccurate when designing tapered girders with TCSWs. The bending moment can cause a redistribution of shear force in a tapered case, which leads to the transfer of shear force from the TCSWs to the curved bottom flanges, resulting in the TCSWs and curved bottom flanges resisting shear force together. This study also reveals the shear force transfer efficiency in the maximum cantilever stage of the bridge. The results indicate that the shear bearing mechanism of the girder undergoes a gradual transition from a state where TCSWs are the primary shear resisting member at the section near the free end to a state where both TCSWs and the curved bottom flange collaborate to resist shear force as the section moves towards the pier. The study suggested that the maximum shear bearing ratio of the curved concrete bottom flange can reach 60.55% at the section near the pier, starting to replace the TCSWs as the main shear bearing member. Consequently, the shear force calculation method recommended by the existing standards may result in substantial computational errors, with the maximum error reaching as high as 155.62%.

Cross-sectional and bidirectional connection design methods for volumetric steel modules

Modular steel constructions (MSCs) are becoming increasingly popular because of their advantages such as rapid construction speed, less demand for on-site labor, quick demolition, and recycling after demolition. An architecturally pleasing all bolted joint called modular bidirectional load-bearing and energy-dissipating joint (MBJ) with innovative modular bidirectional load-bearing and energy-dissipating connectors (MBC) was proposed in this study to achieve vertical and horizontal connection of adjacent modules simultaneously. Design methods that involve cross-sectional design of modules, as well as bidirectional connection design among modules were proposed to establish a relationship between the design of modules and MSCs by “equal initial stiffness” principles of MBJs and traditional bidirectional joints (TBJ). The initial stiffness of MBJs is based on a deep analysis of the force transfer mechanism and deformation characteristics of MBJ panel zones. The FEM of the MBJs was set according to the verified modeling approach, in contrast to the experimental results. Finite element models were set to verify the proposed design method, and theoretical studies were conducted. Our findings show that the ratio of the total cross-sectional moment of inertia of adjacent columns to that of the traditional column ranged from 0.600 to 1.228, the “equal initial stiffness” of MBJs to that of TBJs can be achieved, and the lateral strength of MBJs is consistently greater than that of the corresponding TSJs. In addition, the proposed design method can easily achieve standardization of modules because the ratio of the total cross-sectional moment of inertia of the MBC, ceiling beam, and floor beam to that of traditional beams is in a large range. The maximum error of the initial stiffness of the MBJs between the FEM results and theoretical values was 13.89 %, which meets the engineering accuracy requirements. The research results provide a theoretical basis for the design of MSCs for seismic regions.

Performance of concrete filled steel tubular (CFST) members with circumferential gap under lateral impact

To investigate the influence of circumferential gap on the impact-resistance capacity of CFST columns, 12 CFST specimens were tested under constant axial load and lateral impact loading at mid-span. The test parameters included gap ratio, impact velocity, and slenderness ratio. The failure mode, impact force versus time curves, and deflection versus time curves of CFST specimens with circumferential gap were experimentally investigated and compared with those of the reference samples without any gap. Based on the test results, the failure mode, impact force history, deflection response, and energy dissipation of the specimens were experimentally investigated, and the influence of the above parameters on the impact-resistance of CFST specimens was analyzed. To further explore the force transfer mechanism of CFST with gap under lateral impact, a finite element analysis (FEA) model was established, and the influence of the gap on the contact stress, internal force transfer mechanism, and dynamic flexural capacity of CFST specimens was analyzed. Lastly, a simplified formula for predicting the dynamic flexural capacity of CFST considering the influence of circumferential gap was proposed, which could provide a reference for practical engineering applications.

Bond behavior of FRP-concrete wet-bonding interface under lateral confinement

Wet-bonding is a technique of connecting fiber reinforced polymer (FRP) profile and cast-in-place concrete, which is characterized by the simultaneous hardening of concrete and adhesive. The mechanical properties of wet-bonding interface have been investigated by researchers, but none of them considers the influence of lateral confinement which is commonly present in structures. The insufficient knowledge on wet-bonding consequently hinders its application in FRP-concrete hybrid structures. To this end, this paper investigates the bond properties of wet-bonding interface in confined concrete through pullout and pushout tests. Test results indicate that the interfacial behavior of wet-bonding interface can be divided into three stages. In the first stage, the interfacial resistance comes from the chemical bond of adhesive, and the lateral confinement is hardly activated. This stage comes to an end when the interface between adhesive and concrete fails. In the second and third stage, the interfacial resistance is mainly contributed by the friction between fractured surfaces of adhesive and concrete. The relative movement of fractured surfaces which are microscopically rough induces vertical movement and then activates the lateral confinement, resulting in lateral pressure and tangential friction. The significant friction behavior further damages the FRP-adhesive interface, leading to the final delamination of adhesive from the FRP plate. Based on the above force-transfer mechanism, a bond stress-slip model depending on the lateral pressure is developed. This interfacial model is implemented into Abaqus and its effectiveness is verified by comparing with test results.

Experimental study on torsional behavior of tapered high strength thin-walled concrete-filled double-skin steel tubular columns

Comparing with traditional straight concrete-filled double-skin steel tubular (CFDST) members, tapered CFDST members have been increasingly used in the domain of power industry due to esthetics and special spatial experience. In addition, the utilization of high strength materials can reduce cross-sectional area and further lower construction cost. In this paper, the torsional behavior of tapered high-strength thin-walled CFDST (THSTW-CFDST) columns with or without longitudinal stiffeners was investigated and a total of twenty tapered THSTW-CFDST specimens were tested. The failure modes, torque-torsional angle curves and torsional capacity of the THSTW-CFDST columns were investigated. The results demonstrate that the installation of stiffeners can significantly improve the local stability of thin-walled steel tubes, but reduce the torsional capacity of the members. Compared with THSTW-CFDST specimens without stiffeners, the torsional capacities of those with stiffeners have been apparently reduced. Based on the experimental results, the finite element (FE) model was developed and verified, and then utilized to ascertain the force-transfer mechanism and the stress development process of each component of THSTW-CFDST columns. In addition, the effects of the various parameters including hollow ratio, diameter-to-thickness ratio, inner steel tube strength to outer steel tube strength ratio, concrete strength the torsional behavior of THSTW-CFDST members were quantitatively assessed. Finally, the accuracy of the existing methods for predicting the torsional capacity of THSTW-CFDST members was evaluated.

An enhanced steel sandwich foamed aluminum for strengthening RC frame structure: Experiment and numerical simulation

To improve the impact resistance performance of reinforced concrete (RC) frame structure against debris flow, an enhanced steel sandwich foamed aluminum strengthening method is proposed. A series of debris flow impact tests of the traditional reinforced concrete frame structure (TRCFS) and the strengthened reinforced concrete frame structure (SRCFS) are designed and carried out. Based on the impact test, the effectiveness of the proposed strengthening method is validated, and its energy consumption mechanism is further revealed through a comparative study. Meanwhile, the corresponding numerical simulations are carried out to validate the reasonableness and accuracy of the experimental results. The experimental results illustrate that the enhanced steel sandwich foamed aluminum strengthening method has three protection mechanisms, and this strengthening device can effectively improve the RC frame structure’s impact resistance. The SRCFS model has a more favorable force transfer mechanism, which can reasonably mobilize other members and significantly improve the normal service ultimate bearing capacity of the whole frame structure. Moreover, the numerical results match well with the experimental results, which demonstrates that the debris flow impact test can adequately reveal the impact resistance performance of the SRCFS model.

Experimental and numerical investigations on force transfer mechanism of steel-concrete joint in hybrid girder bridges

Steel-concrete joint is the core force transfer node of hybrid girder bridges. However, the load transfer mechanism of steel–concrete joint has not been understood enough, due to the material discontinuity, abrupt change of stiffness, and complex structure. In this paper, the model test of a typical steel–concrete joint in hybrid girder bridges and the push-out tests of its main force transfer components were carried out. The load-slip curve, stress distribution, and failure mode of the specimens were compared and discussed. The test results show that the steel–concrete joint possesses favorable axial stiffness and bearing capacity. The ultimate failure mode of the joint was reached when the steel beam segment adjacent to the steel–concrete joint buckled. However, the steel–concrete joint was still comparatively intact and in the elastic state during the loading process. In addition, the internal force transfer mechanism and characteristics of the steel–concrete joint were analyzed by finite element method. In terms of the force transfer rate, the bearing plate, perfobond leiste (PBL) connectors, and end face of the T-shaped steel girder transferred 72.9 %, 7.9 %, and 19.2 % of the total axial force, respectively. The redundancy analysis shows that the bearing capacity redundancy of the joint is 1.52. The joint has sufficient bearing capacity redundancy, but the ultimate bearing capacity of the joint as well as its adjacent areas is determined by the axially loaded steel beam segment.

Shear-transfer mechanisms in reinforced concrete beams with GFRP bars and basalt fibers

An increase in the use of glass fiber reinforced polymer (GFRP) bars and discrete fibers in reinforced concrete structures, associated with the limited understanding of the shear behavior of concrete beams, highlights the need for a comprehensive study of various force transfer mechanisms. This article investigates the experimental behavior of four slender reinforced concrete beams with GFRP bars. The testing program includes beams with and without GFRP stirrups and dispersed basalt fibers in the concrete matrix. The displacement fields throughout the shear span were monitored according to the digital image correlation (DIC) technique and shear-transfer constitutive models from the literature assessed the contribution of each mechanism. The sum of such contributions consistently agreed with the experimental shear strength and the use of fibers in beams with GFRP stirrups modified the relative influence of both shear reinforcements, i.e., one of them can preponderate over the other in function of load stage and failure mode.

Experimental research on the structural performance of continuous composite beams with uplift-restricted and slip-permitted connectors

The uplift-restricted and slip-permitted (URSP) connector technology is a new composite technology which achieves the purpose of reducing the tensile stress in concrete slab by releasing part of the composite action in the negative moment region. In this paper, it is found that arranging URSP connectors in continuous composite beams has an end-restraint effect, which has a significant impact on the force transfer mechanism of URSP composite beams. Previous studies on URSP technology seldom mention similar constraint effects, which cannot accurately reveal the mechanical behavior of URSP composite beams. In order to properly consider the influence brought by the end-restraint effect, this study uses continuous composite beams to carry out experimental research. Three two-span continuous composite specimens are fabricated and tested in this research. Six aspects of performance are compared and analyzed in detail, including ① cracking load, ② crack distribution and development pattern, ③ interfacial slip behavior, ④ deformation and stiffness, ⑤ internal force redistribution, and ⑥ strain distribution. It is found that the URSP connector can realize the release of part of the composite action, and has a significant effect on the crack control in the negative moment region. Meanwhile, the application of URSP connectors has little effect on the stiffness, bearing capacity and strain of steel beam.

Study on Surface Configurations and Force Transfer Mechanism of Dual-Wedge Shaped Slips for Liner Hanger

The penetration force and depth of the slip teeth are important factors influencing the hanging capacity of liner hanger, which can lead to failure of well cementation. In this study, a method to calculate the penetration force of dual-wedge slip teeth was presented by considering the surface configuration and the force transfer mechanism of dual-wedge slip in three dimensions. The interaction between dual-wedge slips and casing was simulated using ABAQUS 6.14 software, and the contact force (penetration force) was obtained. Experimental research was carried out to verify the correction of calculation and simulation. The strain of casing was obtained after the dual-wedge slips set under axial loads. The experimental results, theoretical prediction, and the numerical simulation are in good agreement. The effects of geometrical parameters on force transfer characteristics were discussed, which shows that the penetration force of dual-wedge slips increases with increase in the liner weight and Eulerian angle γ, and it decreases with the increase in Eulerian angle α and friction coefficient. The geometric parameters of the dual-wedge slip can be designed to obtain an optimal penetration force, and ensure that the slip teeth penetrate into the inner wall of casing without damage to the casing. The penetration force can be obtained by optimizing the parameters related to geometry of dual-wedge slips.

Splice Connections for Built-Up Column Assemblies in Cold-Formed Steel Construction

The development of simple connection methods is necessary for increasing cold-formed steel (CFS) construction activities. A new splice connection concept for the CFS built-up column-to-column connections is presented in this paper. This simple connection concept will use the same size and shape of the geometry as the CFS built-up column, which will enable a quick erection process. The new splice connection configurations, arrangement, and installation methods for cold-formed steel construction are demonstrated. Twenty-eight experiments, which include four actual columns, two disconnected columns, and 22 columns with splice connections, are carried out. This paper examines the influence of various parameters of splice connections such as length, thickness, and number of fastener rows. The design strength of the actual column is determined using the direct strength method (with modified global and local slenderness approaches) and is compared with the results of the splice connected columns for adequacy. The force transfer mechanism and failure modes of splice connection components are demonstrated in the form of detailed sketches. The smaller length splice connections led to localized failures, while the longer splice connections enabled the uniform force distribution between the built-up column cross-sections. Finally, it is recommended that the splice connection configuration should be a minimum of 300 mm in length, the splice thickness should be equal to the CFS built-up cross-section, and two rows of fasteners for attaining the required design strength of the built-up column members.

Numerical Investigations of Progressive Collapse Behaviour of Multi-Storey Reinforced Concrete Frames

This paper presents numerical simulations of multi-storey reinforced concrete frames under progressive collapse scenarios. Reinforced concrete frames with different storeys are modelled using DIANA. The load resistance and failure mode of frames are obtained from the numerical simulation. Variations in axial force and bending moment at the beam end are also determined and analysed to shed light on the force transfer mechanism. Numerical results show that the single-storey frame can develop compressive arch action at the initial loading stage and subsequent catenary action at large deformations. However, in multi-storey frames, only the first-storey beam develops compressive arch action and catenary action, whereas beams in other storeys show rather limited axial compression force. Based on numerical results, a design method is proposed for multi-storey frames to resist progressive collapse. Comparisons between numerical results and design methods suggest that the design method can evaluate the progressive collapse resistance of multi-storey frames with good accuracy.

Force transmission and SUN-KASH higher-order assembly in the LINC complex models.

The linker of the nucleoskeleton and cytoskeleton (LINC) complex comprises of SUN (Sad-1 and UNC-84) and KASH (Klarsicht, ANC-1, SYNE homology) domain proteins, which connect the inner and outer nuclear membrane, thereby mediating the transfer of physical forces between the cytoskeleton and the nucleoskeleton. While impaired SUN and KASH proteins are associated with structural and functional cell defects, the precise mechanism of force transduction and the assembly of these proteins remain unknown. Recent studies suggested a higher order assembly of SUN and KASH instead of a more widely accepted linear trimer model for the LINC complex. In the present study, we use molecular dynamics simulations to investigate the mechanism of force transfer across the two proposed models of LINC complex assembly, namely the 3:3 linear trimer model and the 6:6 higher-order model. Employing steered molecular dynamics simulations with forces at different rates and directions on various structures, we examine the structural stability of the two models under various biologically relevant conditions. Our results suggest that both models can withstand and transfer significant levels of force while retaining their structural integrity. However, some of the structures were more stable under specific forces compared to other structures. Slower pulling rates resulted in higher mean square fluctuations of the proteins compared to the fast pulling. Interestingly, the higher-order assembly tends to provide an additional range of motion flexibility and might be more suitable for describing the interaction between SUN and KASH under compressive and shear forces. These findings offer insights into how the SUN and KASH proteins maintain the structural integrity of the nuclear membrane.