Rigid Connection Research Articles

Shaking table tests on concrete-filled steel tubular-framed building assembled with microcrystalline foam boards

In recent years, prefabricated structures have been widely constructed to reduce construction costs and time. In this study, a new type of prefabricated structure, lightweight concrete-filled steel tubular (CFST)-framed building assembled with microcrystalline foam boards (MFBs), was developed. The MFBs exhibited high strength, heat insulation, soundproof, light weight, fireproof, and ecofriendly characteristics. The MFBs were combined with light steel keels and connected to the CFST frame with flexible and rigid connections. Shaking table tests on a full-scale, two-story, single-span lightweight CFST-framed building assembled with MFBs as exterior wallboards were performed to assess its dynamic properties and seismic response under the earthquake. The input waves used for the shaking table tests were the El-Centro, Taft, and Zhangjiakou artificial waves with seismic ground motion intensities of 8°–9°. The results indicated that the CFST-framed building exhibited satisfactory seismic performance. The main damage behavior was the cracking and spalling of the MFBs, however, the MFBs used as exterior wallboards were easy to repair and replace. No wallboard collapse occurred, and the lightweight CFST frame was in the elastic deformation stage. The flexible connections absorbed a large amount of energy, resulting in a reduction in the displacement of the structure and little damage to the wallboards under the earthquake. Finally, a nonlinear distribution model of acceleration amplification factors for calculating the seismic force on MFBs was established.

Concrete fatigue of composite constructions with rib shear connectors

AbstractRib shear connectors are gaining increasingly attention in the field of composite constructions. Especially in bridge constructions, rib shear connectors offer many advantages compared to conventional composite shear connectors such as headed studs. In order to describe the load‐bearing behaviour of rib shear connectors under cyclic loading, the successively increasing slip resulting from the cyclic loading of the shear connectors must be taken into account. The latter leads to the growth of the relative displacements along the composite joint and thus, to the degradation of the previously rigid shear connection. This effect leads to rearrangements of internal forces between the composite partners through which the load bearing behaviour and load bearing capacity of the structure alter. In this article results of experimental investigations on two cyclic single Push‐Out‐Tests (sPOT) and one full‐scale girder test regarding the degradation of the composite interconnection are presented and analysed. The investigated shear connectors in the full‐scale girder test are subjected to a comparable load history to that of the connectors in the sPOT. The results give insight into the effects of the degradation of the shear connection, as previously seen in sPOT, on the overall load bearing behaviour of composite girders.

Seismic behavior of innovative hybrid CLT-steel shear wall for mid-rise buildings

This paper examines the seismic behavior of CLT-steel hybrid walls at 6- and 10-story heights to increase seismic force resistance compared to conventional wooden walls. The ultra-strong shear walls proposed in this paper are called Framing Panel Shear Walls (FPSW), which are based on a robust articulated steel frame braced with CLT board panels and steel tendons. Timber structures are well-known for their ecological benefits, as well as their excellent seismic performance, mainly due to the high strength-to-weight ratio compared to steel and concrete ones, flexibility, and redundancy. However, in order to meet the requirements regarding the maximum inter-story drifts prescribed in seismic design codes, a challenging engineering problem emerges, because sufficiently resistant, rigid and ductile connections and lateral assemblies are not available for timber to meet both the technical and economical restrictions. Therefore, it is necessary to develop strong and cost-effective timber-based lateral systems, in order to become a real alternative to mid- and high-rises, especially in seismic countries. In this investigation, the dynamic response of cross-laminated timber (CLT) combined with hollow steel profiles has been investigated in shear wall configuration. After experimental work, research was also carried out into numerical modelling for simulating the cyclic behavior of a hybrid FPSW wall and the spectral modal analysis of buildings of 6- and a 10-stories with FPSW. A FPSW shear wall can double the capacity and stiffness.

Study of the seismic behavior of rigid and semi-rigid steel moment-resisting frames

Steel moment resisting frames are prevalent seismic force resisting systems that are used extensively in high seismic regions worldwide. New design procedures suggested by codes have resulted in extensive use of semi-rigid connections in moment resisting frames. These connections have some degree of flexibility. This study focuses on seismic performance of steel moment-resisting frames with different degrees of moment connection rigidities. Three moment frames (5, 10 and 15 stories), each with different levels of connection rigidities (full, 80%, 70% and 60% rigidities) are analyzed under the 22 far-field ground motions presented in FEMA P695. Detailed modal analysis, non-linear static (pushover) analysis and incremental dynamic analysis (IDA) were conducted. Results reveal that semi-rigid frames have lower base shears and higher structural deformations, but higher energy absorption capability. Lastly, detailed performance analysis was conducted. The results show that probability of exceeding the fully operational performance level is higher in semi-rigid frames as compared to rigid connections. The inclusion for the rigidity in the beam-column can have an impact on the performance of steel moment frames which cannot be ignored during the design and retrofit of steel moment-resisting frames.

The Response Modification Factor for Seismic Design of Integral Abutment Bridges

The response modification factor (R factor) is a crucial parameter for calculating the design seismic forces applied to a bridge structure. This factor considers the nonlinear performance of bridges during strong ground motions. Conventional bridge structures rely on the substructure components to resist earthquake forces. Accordingly, there are R factors available in the design codes based on the type of bridge substructure system. Lateral load resisting system of Integral Abutment Bridges (IABs) in the longitudinal direction is more complex than ordinary bridges. It involves the contributions from soils behind the abutments and soil/structure interaction (SSI) in addition to existing rigid connection between the superstructure and abutments. There is no R factor available in any design code throughout the world for IABs in the longitudinal direction that considers all these parameters. In this research, the Federal Emergency Management Agency publication FEMA P695 methodology has been applied to estimate the R factor for IABs. It is found that 3.5 could be a safe and valid R factor in the longitudinal direction for seismic design of such bridges.

Biomechanical analysis of rigid and non-rigid connection with implant abutment designs for tooth-implant supported prosthesis: A finite element analysis

Background/purposeThe design of the connectors and implant abutments could affect the stress distribution of the tooth-implant supported prosthesis (TISP) entire system after loading. Therefore, the purpose of this study was to investigate the stress distribution of the TISP in different connectors and different implant abutments after loading. Materials and methodsThe TISP design used in this study was divided into six models. R1, R2 and R3 represented the tooth and the one-piece, two-piece and three-piece abutment implant system connected by a rigid connector, respectively, while NR1, NR2 and NR3 were the corresponding tooth-abutment implant systems connected by a non-rigid connector. A vertical occlusal load of 50 N was applied at a right angle on the 6 occlusal points of the occlusal surface. ResultsAs a result, regarding the maximum average stress distribution, R1 and NR1 appeared on the implant fixture, and the other four models were on the implant abutment. On the other hand, regardless of the abutment implant system, the maximum von Mises stress generated by the rigid connector was greater than the corresponding non-rigid connector in the cortical bone around implant. In addition, the three-piece abutment implant system had lower von Mises stress than the one-piece and two-piece implant systems in the cortical bone. ConclusionIt is concluded that by adding a flexible non-rigid connector and three-piece abutment device design to TISP, the occlusal load of the implant was dispersed, and the stress could be gradually introduced into the relatively strong implant abutment.

Proposing a New Detailing Scheme for Rigid Connection with Endplate without the Need for Welding in Column

Connections are among the most important elements in the behavior of a structure. Numerous detailing schemes have been proposed for steel connections, many of which involve welding. In many rigid connections, using continuity and double plates enhances the behavior of the panel zone. Although this leads to an improvement in the behavior of the connection, welding procedure associated with it offers some disadvantages. The aim of this study is to present a numerical and experimental assessment of a new detailing scheme for rigid connections endplates. In this detail, the welding on the column of the structure and the panel zone has been completely removed. A stiffened channel carries out the responsibilities of continuity and double plates. This stiffened channel is fixed to the column using bolts and nuts. First, multiple numerical models were constructed in ABAQUS and after pushover and hysteretic analyses, the best model was identified. Then, based on the results of the numerical models, two full-scale experimental models were built and subjected to hysteretic loading until the hysteretic curves experienced degradation. The first sample was the principal and standard model which was built based on the specifications of the BSEEP-4ES and AISC 358-16 guidelines for pre-qualified connections so that it can serve as a basis of comparison for the other sample. The second sample was the preferred model selected based on the numerical results, which was made by attaching a channel profile to two stiffeners and was meant to be a replacement for the standard model. Assessment of the obtained results showed that under loading, both models satisfied the seismic criteria for the special moment resisting connection. The proposed detailing exhibited a better behavior in terms of seismic parameters compared to the standard sample and was also easier to implement.

Modeling Post-Scratching Locomotion with Two Rhythm Generators and a Shared Pattern Formation.

Simple SummaryPost-scratching locomotion in cats refers to the spontaneous occurrence of an episode of locomotion generated after an event of scratching. This phenomenon suggests the potential existence of shared neurons in the spinal cord mediating the transition from one rhythmic motor task to another. Here, we examine this possibility with a mathematical model, reproducing the experimental observations. Our findings reveal a possible mechanism in which the central nervous system could share neuronal circuits from two central pattern generators to produce a sequence of different rhythmic motor actions.This study aimed to present a model of post-scratching locomotion with two intermixed central pattern generator (CPG) networks, one for scratching and another for locomotion. We hypothesized that the rhythm generator layers for each CPG are different, with the condition that both CPGs share their supraspinal circuits and their motor outputs at the level of their pattern formation networks. We show that the model reproduces the post-scratching locomotion latency of 6.2 ± 3.5 s, and the mean cycle durations for scratching and post-scratching locomotion of 0.3 ± 0.09 s and 1.7 ± 0.6 s, respectively, which were observed in a previous experimental study. Our findings show how the transition of two rhythmic movements could be mediated by information exchanged between their CPG circuits through routes converging in a common pattern formation layer. This integrated organization may provide flexible and effective connectivity despite the rigidity of the anatomical connections in the spinal cord circuitry.

Effect of inter-module connections on progressive collapse behaviour of MiC structures

Modular integrated Construction (MiC) is a game changing construction approach which could significantly increase construction efficiency, quality, and sustainability. For steel MiC structures, modules are manufactured in the factories and assembled at the construction sites through inter-module connections. The concern of the vulnerability of these connections under abnormal hazards leading to disproportionate progressive collapse will impede industrial applications of MiC structures in the construction community. This study investigates the structural robustness of corner-supported modular steel buildings with the focus on different inter-module connections. A sub-structure extracted from a five-storey modular building is analysed by high fidelity finite element analysis under a corner column removal scenario. The load redistribution mechanism and failure modes are investigated thoroughly, based on which the simplified macro model is proposed where connections are modelled with rotational springs. Good consistence is found for the simplified model and the detailed FE analysis in terms of the pushdown curve. It is also found that the inter-module connection types will affect the beam-column joint properties which dominate the progressive collapse resistance of MiC structures. Therefore, attention should be paid when selecting different inter-module connections. The current rigid beam-column joint connection may lead to nonconservative evaluation.

Research on Hydroelastic Response of an FMRC Hexagon Enclosed Platform

The numerical hydroelastic method is used to study the structural response of a hexagon enclosed platform (HEP) of flexible module rigid connector (FMRC) structure that can provide life accommodation, ship berthing and marine supply for ships sailing in the deep ocean. Six trapezoidal floating structures constitute the HEP structure so that it is a symmetrical very large floating structure (VLFS). The HEP has the characteristics of large area and small depth, so its hydroelastic response is significant. Therefore, this paper studies the structural responses of a hexagon enclosed platform of FMRC structure in waves by means of a 3D potential-flow hydroelastic method based on modal superposition. Numerical models, including the hydrodynamic model, wet surface model and finite element method (FEM) model, are established, a rigid connection is simulated by many-point-contraction (MPC) and the number of wave cases is determined. The load and structural response of HEP are obtained and analyzed in all wave cases, and frequency-domain hydroelastic calculation and time-domain hydroelastic calculation are carried out. After obtaining a number of response amplitude operators (RAOs) for stress and time-domain stress histories, the mechanism of the HEP structure is compared and analyzed. This study is used to guide engineering design for enclosed-type ocean platforms.

Influence of Bubbles Causing Cavitation on Spool Oscillation of a Direct Drive Servovalve.

A direct drive servovalve has some inherent benefits over its conventional counterparts, but also has better reliability and output power. However, due to the rigid connection between the spool and the motor, which takes the place of interstage drive-by fluid, the spool oscillation is a long-standing unsolved problem. In order to study the oscillation mechanism and the influencing factors, a double-circuit direct drive servovalve was numerically simulated. An oil return valve cavity was concentrated on as the main flow domain and was used to analyze the fluid flow characteristics. Local cavitation fraction and surface average cavitation fraction were defined to evaluate the cavitation situation. The periodic growth process of bubbles in the valve cavity was obtained. The numerical results show that bubbles in the oil return valve cavity changes, although the occurrence, evolution, and collapse stages were certain. The intensity of pressure pulsation caused by bubble variation is highly related to the bubbles causing the cavitation, which suggests a workable way to inhibit the spool oscillation.

RIGID CONNECTION WITH GRANITE CHIPS IN THE TIMBER-CONCRETE COMPOSITE

Timber-concrete composite panels enables to combine advantages of pure timber and pure concrete panels in one structural member especially in the case, when the rigid timber-concrete connection is provided. The effectiveness of timber and concrete use and load-carrying capacity of the timber-concrete composite panels will grow in the case. The new concept of rigid timber to concrete connection was developed by the using of the granite chips as the keys to provide high quality of the glued connection. Behaviour of the timber-concrete composite panels were investigated by finite element method and laboratorian experiment. Three timber-concrete composite panels in combination with carbon fibre reinforced plastic composite tapes in the tension zone with the span 1.8 m were statically loaded till the failure by the scheme of three-point bending. One specimen was produced by dry method, by gluing together cross-laminated timber panel and prefabricated concrete panel. Timber-concrete connection of the other two specimens was provided by the granite chips, which were glued on the surface of the cross-laminated timber by epoxy, and then wet concrete was placed. Dimensions of the crushed granite pieces changes within the limits from 16 to 25 mm. The current study focuses on determining the effect of the use of granite chips for timber-concrete composite panels with adhesive connection between layers. The effect of the use of granite chips in rigid connection is determined by comparison of mid-span displacements and level of failure load of the two variants of the timber-concrete composite panels. Three-dimensional finite element models of timber-concrete composite with rigid connection was developed and validated by experiment data. Obtained results shown, that the use of the granite chips in rigid timber to concrete connection allow to make a quality rigid connection. Possibility to increase by 28% level of failure load of the timber-concrete composite panels by the adding of granite chips was stated. Maximal vertical mid-span displacements of the panels decrease about 3.8 times at the same time.

Experimental study of grouted sleeve connections under bending for steel modular buildings

In steel modular buildings, both inter- and intra-module connections can attract bending moment under the action of lateral loads. The moment is distributed in accordance with the relative stiffness ratios among the structural components and hence the connections should have sufficient flexural resistance and stiffness relative to the connecting members to be classified as a rigid connection. Typically, intra-module connections (beam-column joints within a module) are designed as full-strength rigid connections, while the inter-module connections are normally designed as pin-connected for fast-track construction. This paper proposes the use of grouted sleeve connection which does not require bolting or welding to achieve fast-track construction of modular buildings. An experimental programme is carried to investigate two types of inter-module connections, shear-keyed grouted sleeve versus slot-hole grouted sleeve, under flexural loading to evaluate their structural performance in terms of strength, stiffness, and ductility. The results showed that both connections have adequate moment resistance and ductility to resist bending and they can be classified as partial strength rigid connection for use in braced steel modular buildings. An analytical model, based on EN1992-1-1, is proposed to predict the moment resistance of the connection for the purpose of design.

Development of nanobody-based POLArIS orientation probes enabled multi-color/multi-target orientation imaging in living cells

Fluorescence polarization microscopy (FPM) can visualize the dipole orientation of fluorescent molecules and has been used for analyzing architectural dynamics of biomolecules including cytoskeletal proteins. To monitor the orientation of target molecules by FPM, target molecules need to be labeled with fluorophores in a sterically constrained manner, so that the fluorophores do not freely rotate. Recently, a versatile probe for such labeling using fluorescent proteins, POLArIS (Probe for Orientation and Localization Assessment, recognizing specific Intracellular Structures of interest), was reported. POLArIS is a fusion protein consisting of a non-immunoglobulin-based recombinant binder Affimer and a green fluorescent protein (GFP), where the Affimer and GFP are rigidly connected to each other. POLArIS probe for molecules of interest can be developed through phage display screening of Affimer. This screening is followed by the rigid connection of fluorescent proteins to the selected Affimers. The Affimer-based POLArIS, however, cannot be used with animal immune libraries for selecting specific binder clones. In addition, multi-color FPM by POLArIS was not available due to the lack of color variations of POLArIS. In this study, we have developed new versions of POLArIS with nanobodies, which are compatible with animal immune libraries, and expanded color variations of POLArIS with cyan/green/yellow/red fluorescent proteins, enabling multi-color orientation imaging for multiple targets. Using nanobody-based POLArIS orientation probes, we performed two-color FPM of F-actin and vimentin in living cells. Furthermore, we made nanobody-based POLArIS probes that have different dipole orientations for adjusting the orientation of fluorescence polarization with respect to the target molecules. These nanobody-based POLArIS with options of colors and dipole orientations will enhance the performance of this probe for broader applications of fluorescence polarization imaging in living cells, tissues, and whole organisms.

60188 The coupled dynamic analysis of hydroelectric unit and powerhouse considering the bolt connection characteristics

As the increasing of the capacity and water head of the hydropower stations, the hydroelectric unit’s vibration and its induced powerhouse vibrations become a critical problem. The system of hydraulic-mechanical-electric-structural is coupled and with strong non-linear characteristics. The frame and head cover are all connected with the powerhouse pier via high-strength bolt. The paper is concentrated on the dynamic coupling mechanism and simulation model considering the bolt’s connection and load transmission characteristics. With the theory analysis and numerical simulation, the connection and transmission behaviour of the high-strength bolt would be studied and a more accurate and simple mechanical expression would be derived. The connection sliding law and dynamics modelling method of bolts are discussed. Based on the displacement-load curve of single lap and single bolt analysis it is concluded that the increasing preloading will improve the tangential bearing capacity of the bolted joint connection. Then the FEM coupling model of the lower bracket and powerhouse is established with the virtual medium method. Based on the free-vibration and dynamic response analysis the effects of the loosening of the bolt on the static stiffness of the coupling structure are discussed. The von-Mises stress’s increasing due to some of the bolt’s loosening would result to the material fatigue damage. Finally five preloading schemes of the bolts are discussed and the simulation results show that the preloading force has a greater lateral impact on the structure than on the longitudinal direction. The preloading force improves the coupling structure’s stiffness and reduces the vibration amplitude of the frame. As for the preloading force, when it is small the connection effect is not strong enough and the vibration level may be higher, so the actual preloading state should be exactly simulated. When the bolt preloading reaches 60-70% of the material yield strength, the rigid connection can be directly used in the modelling for the convenience of calculation.

An analytical solution to the problem of thermoelastic bending of a multilayer beam with different temperature of longitudinal faces

An exact analytical solution of the quasistatic problem of thermoelasticity is presented for a section of a narrow multilayer beam with different temperatures of the longitudinal lower and upper faces and a heat flow of arbitrary height across the sections through the lateral faces. The solution was obtained for the entire package of layers by sequentially solving the heat equation for an inhomogeneous beam, taking into account the ideal thermal contact of the layers and the system of equations of the plane problem of the theory of elasticity under the assumption of a rigid connection of the layers. To take into account the inhomogeneity of the beam, a continuum approach is used, in which the multilayer material is considered continuous with variable physical and mechanical characteristics. The resulting relations take into account the orthotropy of the physico-mechanical properties of the materials of the layers and their compliance with the transverse shear and compression strains. An example of implementation of a solution for a five-layer beam with combined rigid and articulated fastening of the ends is given.

Experiment and numerical investigation on structural response of a FMRC hexagon enclosed platform in waves

Hexagon Enclosed Platform (HEP) provides life accommodation, ship docking and marine replenishment for many ocean-going vessels in deep ocean. The HEP is composed of six trapezoidal floating modules connected by six rigid connectors and has characteristic of heteromorphic mat-type so that its hydroelastic response is critical. Therefore, this paper proposes a FMRC (Flexible modulus Rigid Connector) HEP model and studies its hydroelastic response by means of numerical simulations and model experiment. Firstly, a scaled model of HEP which is also made up of six trapezoidal structural modules constructing with a steel layer and foam layer is designed and fabricated for model experiment. Secondly, the model experiment of HEP is performed in a number of tank waves. Thirdly, 3D hydroelasticity method is used to calculate the load and structural responses of HEP model. Finally, numerical results and experimental results involving frequency-domain and time-domain results are obtained and compared, and the structural response mechanism of FMRC HEP is analysed. It is found that experimental results and numerical results have accordant matching and hydroelastic response of HEP is generated indeed based on research results. The research results and conclusions obtained in the paper are used to guide conceputal design of a HEP structure.

Normal stress distribution of timber-concrete composite panels with an adhesive shear connection under thermal and humidity loadings

Humidity and temperature conditions have a substantial influence on the stresses and total deformation of timber-concrete composite panels, especially in terms of the high rigidity of the shear connection. In the present research, the normal stresses that resulted from the hygrothermal load of timber-concrete composite panels with an adhesive shear connection were analyzed. Three timber-concrete composite panel specimens were placed in controlled climate conditions. Strains in two orthogonal directions were measured. The stress distribution resulted from an approximate analytical calculation model. The results show that the highest stresses occurred near the shear connection. An increase in timber moisture content by 2.1% was predicted to result in exceeding the flexural tensile strength in the concrete perpendicular to the timber grain direction. At an outdoor temperature range, stresses influenced only by the temperature alone will possibly not cause a failure of timber or concrete. Under winter environmental conditions, the stress in timber can possibly reach 12% of the bending strength of the timber used.

Static Behaviors and Applications of Buckling Monitoring Members with Rigid Ends

The buckling of compression members may lead to the progressive collapse of spatial structures. Based on the sleeved compression member, the buckling monitoring member is introduced to control the buckling of compression member and raise buckling alert by sensing contact between the core tube and the restraining tube. Considering the rigid connection among the members in spatial structures, the buckling monitoring member with rigid ends needs to be further analyzed. An experimental test was conducted and finite element analyses were performed with calibrated finite element models. The results indicated that the ultimate bearing capacity and post-ultimate bearing capacity of the core tube were enhanced due to the restraint from the restraining tube. The contact was successfully sensed by pressure sensor, revealing that it sensed the buckling of the core tube. Parametric studies were conducted, indicating that the core protrusion, core slenderness ratio, the gap between the core tube and restraining tube, and the flexural rigidity ratio are the key parameters affecting the bearing capacity and the failure modes of the buckling monitoring member, and some key values of parameters were proposed to obtain good bearing capacity. Based on the parametric studies, the failure modes of buckling-monitoring members are summarized as global buckling and local buckling. The stress distribution and deformation mode of buckling monitoring members are presented in the non-contact, point-contact, line-contact, reverse-contact and ultimate bearing state. The buckling monitoring member is applied in a reticulated shell by substituting the buckling members. It can effectively improve the ultimate bearing capacity of reticulated shell.

Konrad Wachsman’s Grapevine Structure: Timber Variations on a Pre-Existing Concept

This paper offers a speculative reflection on the structural concept developed by Konrad Wachsmann in 1953 and built in timber by burkhalter sumi together with Marko Pogacnik IUAV at the Venice Biennale in 2018. The resulting construction, entitled the “Grapevine,” is analyzed according to changing, fragmentary viewpoints that aim to expand the field of its understanding. The Gestalt (shape)—to a certain extent the “aesthetic culmination” of the construction—is examined with regard to the object’s immediate perception. In contrast, a semantic approach questions and interprets the “Grapevine” according to its overriding meaning as a “modern totem.” The object is then brought into relation to sculptures by Joel Shapiro. “Figure” (1989) raises the question of the unstable balance as an artistic intention, while the detail of “étude” (2006) questions the fragility of the joint, in contrast to the rigidity of tectonic connections as assumed by Gottfried Semper. The argument thus comes closer to the conceptual orientation of the Wachsmann construction, namely the knot subjected to tensile stress. Centered on the “Grapevine” installation, this paper illustrates how timber knowledge is formed outside the academy, in dialogues between architects, engineers and timber contractors.