Vertical Bracing Research Articles

Closure without epiglottoplasty or tracheotomy after reconstructive frontal anterior laryngectomy

Reconstructive frontal anterior laryngectomy (RFAL) is a partial laryngeal surgery technique for resecting early-stage (T1–T2) glottic squamous cell carcinoma. Indications comprise a lesion of the anterior commissure of the larynx that cannot be adequately exposed by endoscopy, and cases in which radiotherapy is refused or contraindicated. The initial RFAL technique included epiglottoplasty. Here we propose a technique without epiglottoplasty, with the advantage of avoiding need for tracheotomy in most cases. After the first stage of surgical excision, reconstruction consists in placing a vertical brace transepiglottically and below the cricoid. The epiglottis is thus left at its original height and secured in place to prevent flapping in the pharyngolaryngeal lumen. Transverse bracing is then performed through the thyroid wings: one of the key points of this surgery is to control tension to avoid risk of stenosis. The subhyoid muscles are sutured together to achieve satisfactory sealing. This technique offers satisfying functional results and oncological control. The most frequent complications are (1) secondary tracheotomy, which can be avoided by selecting patients who require a primary tracheotomy and optimizing the seal, and (2) stenosis, which can be limited by not bringing the cartilaginous structures too close together during bracing.

Seismic performance of vertical strut and lateral brace suspended continuous‐plasterboard ceiling system with all edges free in the plane of ceiling

AbstractSuspended ceilings are critical nonstructural elements, and their seismic damage in buildings highlighted the incompatibility between the design and performance of structural and nonstructural elements. In order to study the performance of less researched continuous‐plasterboard ceilings, shake table testing was conducted on a ceiling system vertically supported at grid ends with free edges in its plane and suspended by vertical struts and lateral braces. The system had a clearance of 20 mm at the grid ends to accommodate ceiling movements. The ceiling performed satisfactorily for floor accelerations ranging from 0.2 g to 1.4 g without any visible damage. However, the ceiling was slightly rotated and lightly damaged at its perimeter for an extreme dynamic loading of sinusoidal excitation at its natural frequencies. In addition, the experimental performance of the ceiling was numerically validated using nonlinear and linearized responses of sub‐assemblage test data of critical components and connections. It was observed that the developed numerical models can be used to predict the behavior of such ceiling systems as an alternative to evaluation by shake table testing.

Seismic assessment of different vertical bracing systems in staging of elevated liquid retaining tank

The study of earthquakes indicates that earthquakes have a significant impact on the grid system, as well as significant catastrophic effects on human life, buildings, bridges and other structures. In macro scale water distribution network, water tanks play the key point site component, and it is the most vulnerable element in case of an earthquake. Water tanks play a vital role in our lives as they help to store and supply water for domestic and commercial purposes. They also store water for firefighting, irrigation and other agricultural needs. Based on the previous literatures, papers, articles, and other sources, it can be concluded that during an earthquake generally, a liquid retaining structure, i.e., water tank failure generally occurs due to the inability of the staging system to resist lateral movement. Most post-earthquake failures of elevated tanks are likely to result from dynamic buckling caused by overturning moments of seismically induced fluid inertia and surface sloshing waves. As they are the vital structures of our society, their construction and proper seismic evaluation is crucial. In this paper, the seismic response of liquid retaining tanks for different vertical bracing systems has been compared as per IS1893:2014 part-2 and the response spectrum analysis procedure. In all the models the storage tank's capacity has been taken as 150 cubic meters, keeping all the dimensions the same. The loads are considered as per IS875, IS3370 and other relevant codes. The different models considered in this paper are – water tank without bracing, water tank with diagonal bracing, water tank with cross bracing, water tank with K-type bracing, water tank with chevron bracing and water tank with box bracing. These models have been compared on the basis of different seismic parameters and optimized model is being suggested.

Experimental study on stable bearing capacity of wheel-buckle formwork support frames

To prevent the frequent jamming of straight plugs and disk plates, a novel wheel-buckle joint was introduced and investigated in this study. The destabilization failure mode and stable bearing capacity of the new wheel-buckle formwork support frame were studied through nine full-scale test models. Different influencing factors such as the horizontal scissor brace, vertical scissor brace, spacing of the standing tube, and lift height were considered in these tests. The results indicate that all the models tended to adopt a non-sway buckling mode with a large wave valley, and that the maximum horizontal displacement occurred in the upper-middle part of each model. The stable bearing capacity of each model increased with a decrease in the lift height and spacing of the standing tube. Furthermore, the arrangement of vertical scissor braces could significantly improve the stable bearing capacity of the models. Based on the stability theory, a simplified calculation formula for the stable bearing capacity of the support frame was established. The values calculated through the simplified formula were compared with the values calculated through the JGJ300-2013 code and the test values. It was observed that the formula has sufficient accuracy (average error 13.4 %) in predicting the stable bearing capacity of the support frame, and that the JGJ300-2013 code has sufficient bearing capacity reserve. Notably, the conclusions of this study can serve as a reference for further research on new wheel-buckle formwork support frames.

The effect of columns twisting on the behavior of steel frame of industrial building

The bracing system plays a very important role in the steel frame of an industrial building. The braces ensure the fixation of structures and their required effective lengths, give the frame overall spatial stability and geometric invariability. The scheme of bracing system significantly affects the behavior of the frame and the distribution of forces in its elements. The influence of the design solution of vertical bracing systems along the columns on the stress-strain state of the frame is studied in the article. It is shown that when using solid I-columns with the large web height (over 500 mm), to prevent their twisting and excessive displacements, it is necessary to fix both flanges of the columns in the longitudinal direction. That is why, the use of a single-plane vertical bracing system for the columns with the large web height is not recommended. For this, either two-plane braces can be used (allowing to reduce the twisting angle of the columns by 95%), or various options for fixing the flanges of the columns to struts or other structures (provide a reduction in the twisting angle of up to 88%).

Study on Construction Molding Technology of Long-Span Space Truss Suspended Dome Structure

Typically, the upper part of the roof a gymnasium building is a radial inverted triangular truss structure, and the lower part is a cable structure. They are connected by vertical braces to form a self-balancing structural system. The whole roof is supported by a complex, spatial, prestressed structure comprising tilted Y-shaped laced columns. Such structures rely on the integrity of the form and the application of prestress to achieve the best performance; it is in an extremely unstable state during construction. In order to study the mechanical behavior of the structure in this process, finite element software was used to analyze the cumulative slip of the structure and the construction process of cable tension, and the simulation values were compared to the actual monitoring values. The stress and deformation of the structure in different construction stages were investigated, and a reasonable structural unloading scheme was put forward. The study results showed that the stiffness of the long-span space truss suspended dome structure gradually increased with the structural integrity during construction, and the vertical deformation decreased from 25.4 mm to 19.26 mm with the construction process. The location and magnitude of the structure’s maximum internal force and maximum stress varied greatly compared to the static analysis when considering the construction process effects. Hence, conducting a construction process analysis is necessary. The construction technology of symmetrical rotating cumulative slip proposed in this paper has the advantages of a short construction duration, safe and stable construction process, etc., providing technical references for similar engineering constructions.

Numerical Analysis of Chevron Braced Frames retrofitted using Vertical and Diagonal Brace Members

This article discusses about the retrofitting of the existing chevron braced frames, constructed before the induction of the concept of thespecial concentrically braced frames (SCBF) braced frames. Two arrangements of upgraded bracing were developed; one configuration was inspired by X-brace and Y brace while the other was inspired by Zipper brace and Y-brace. Both arrangements resulted into unique dual half Y-brace (DHYB). The numerical analysis was done by using Abaqus software. The outcomes of the analysis for studying the behaviour of the braced frame after retrofitting were the hysteretic behaviour, plastic energy dissipation and the beam deflection. In most of the cases, retrofitting using the above mentioned technique provided a more stable and balanced hysteretic behaviour, improved energy dissipation, reduced beam deflection. This method of retrofitting would cause minimal structural intervention and least disruption to the occupants.

Safety and stability analysis of variable cross-section disc-buckle type steel pipe high support system

In order to solve the problems of poor safety and difficult determination of construction scheme in the construction process of variable cross-section disc-buckle type steel pipe high support system, based on the stress state of the normal working of the disc-buckle type formwork support, the stability bearing capacity of vertical poles under three working conditions of central pole, side pole and corner pole were experimentally carried out, and the correctness were verified by comparing with the results of the experiment and finite element analysis. Based on the verified finite element model and the characteristics of semi-rigid connection joints, the first-order buckling mode and nonlinear buckling analysis of the stability bearing capacity of the variable cross-section disc-buckle type steel pipe high support system were carried out in the construction period with special structure in practical engineering, the stability bearing capacity and deformation law of the variable cross-section disc-buckle type steel pipe high support system in the construction process were mastered. Through parametric analysis of the influencing factors such as the joint bending stiffness, the setting parameters and the initial imperfections, the influence law of the relevant parameters on the overall stability of the variable cross-section disc-buckle type steel pipe high support system was grasped. The results showed that the corner poles at the higher variable section and the lower variable section of the weak stiffness direction support system were prone to instability and failure. The overall stability bearing capacity was mainly affected by the lift height. The vertical diagonal bracing plays an important role in improving the overall stability, the larger the lift height was, the more obvious the improvement was. The overall stability bearing capacity decreases with increasing top extension length, and the top extension length should be controlled within 0.45 m. When the extension length of the top was greater than 0.45 m, the initial imperfection cannot control the overall stability bearing capacity, and the overall structural stability bearing capacity was determined by the buckling behavior of the top vertical pole. When the joint bending stiffness was greater than 2.0 K, the stability bearing capacity does not change. The higher the support system was, the smaller the influence of joint bending stiffness on the overall stability was.

Investigating the seismic efficiency of buckling-restrained braced frame structures

The bracing systems have been considered a reliable solution for the seismic-resistant design of buildings, which has been widely applied in recent years. This article aims to investigate the performance of braced frame structures in the seismic-resistant design. Typical buckling restrained braced frames, represented by an approximate bilinear behaviour, are selected to perform nonlinear time-history analyses. The findings indicate that bracing systems are a potential solution for seismic-resistant design, as they significantly reduce the top displacement and internal force of the structures based on their dissipation capacities through inelastic behaviour. Furthermore, the performance of vertical bracing systems is recommended to calculate according to the distribution of shear forces along the height of structures, ensuring that they are effective solutions that meet the design philosophies.

Old Iron and Steel Bridges. Historical and technical notes Static and strength of lattice truss girders. Part 4 (Conclusion)

A model was composed only of linear finite elements to simulate 5 consecutive spans (64m+3x66m+64m) of the D. Luiz bridge deck. It integrates the two main girders of the deck, the two horizontal bracings that exist between their upper and lower chords and the transverse vertical bracings located on the same planes of the girders’ verticals. It is already known (see previous parts of this article) that the diagonals of the trusses are single angles, the verticals are double angles and the chords are T-sections, formed by plates and angles, as it happens in many of the lattice truss girders built at that time (second half of the XIX century, first decades of the XX century).

Improving the robustness of steel frame structures under localised fire conditions

PurposeThe robustness of building structures in a fire has recently drawn wide attention. This study presents the progressive collapse analysis of steel frame building structures under localised fire. The main objective of this study is to propose methods to enhance the structural collapse resistance of such structures in fire.Design/methodology/approachA modelling method was developed and validated against both experimental and analytical studies. Then, a series of robustness analyses were performed to investigate the interaction among the members and the pattern of load distribution within the structures. These analyses show that lateral resistance and load redistribution have a vital role in the robustness of the building. Thus, two approaches have been adopted to enhance the robustness of the focused steel frame during a fire.FindingsIt is found that increased size of floor beams and vertical bracing systems are effective measures in preventing whole structure collapse. The larger beam section is able to prevent catenary action so that the load in the failed columns can safely transfer to the adjacent columns without buckling. On the other hand, the bracing system improves the lateral resistance that can accommodate the lateral force when catenary action occurs in the beam.Originality/valuePrevious studies have focused on the collapse mechanism of steel frame structures. However, the parameters affecting the structural robustness in a fire have not yet been explored. To address this gap, this study adopted numerical modelling to undertake parametric studies to identify effective methods to improve the robustness of such structures under fire conditions.

Deformation failure characteristics of weathered sandstone strata tunnel: A case study

Appropriate countermeasures are required after extreme deformation failure of rock mass to ensure the safety of the tunnel construction and operation, especially in a tunnel that through strongly weathered sandstone strata. The load bearing capacity is further weakened by the permeation of water in complicated geological conditions, which can frequently cause collapse and result in budget overruns during the construction period. This paper provides a case study about the process of the extreme deformation that occurred in the Piancheng Tunnel based on in situ monitoring. Based on the analysis of on-site deformation monitoring data, combined with the engineering practice characteristics, the factors affecting the deformation were analyzed, further, the countermeasures were put forward and its effectiveness was analyzed. The maximum settlement reached 1046.3 mm and the convergence reached 876.4 mm, and the seepage, rock strength and bias load were considered the main cause of extreme deformation. As a means to maintaining the structural integrity, countermeasures such as temporary steel arch, vertical bracing, diagonal bracing and the temporary inverted arch combination were used for strengthening the tunnel’s structure, hence, effectively preventing the development of extreme deformation. The manuscript records the whole process from occurrence to countermeasures of extreme deformation of surrounding rock, which provide experience for future similar projects.

An Ultra-Wideband Compact TR Module Based on 3-D Packaging

This study presents a novel four-channel tile-type T/R module which achieves excellent performances in ultra-wideband (2–12 GHz) and integrates all circuits in a super-light (25 g) and compact (27.8 × 27.8 × 12 mm3) mechanical structure in active phased array systems. The key advancement of this T/R module was to choose a Ball Grid Array (BGA) as the vertical interconnection and bracing between High-Temperature Co-fired Ceramic (HTCC) substrates in order to achieve a high-integration 3-D structure. Exploiting the HTCC multilayer layout, this paper presents the design and development of an ultra-wideband, compact and light, high-output power, four-channel, dual-polarization Transmit/Receive (T/R) Module. In this module, microwave circuits and power control circuits are highly integrated into electrically isolated HTCC layers or substrates, resulting in low coupling and crosstalk between signals. Furthermore, multichip assembly technology, multifunctional MMICs, and other high-integration technologies were adopted for this module. Each channel could provide more than 2 W transmit output power, more than 15 dB receive gain, and less than 5 dB receive noise figure. Every module contains four channels. The power supply and phase/amplitude conditioning of each channel can be controlled individually and showed good consistency of the amplitude and phase of all channels. The connectors of manifold port and polarization ports are all SSMP, which can achieve further integration. This module has also an automatic negative power protection function. The module has stabilized performance and mass production prospects.

A Multi-Pier-Macro MPM method for the progressive failure analysis of perforated masonry walls in-plane loaded

The aim of this paper is to present and put at disposal a reliable numerical procedure called MPM (Multi-Pier-Macro) method that can be used by unexperienced practitioners by means of a software equipped only with non-linear truss elements with softening for the progressive failure analysis of large scale perforated masonry walls in-plane loaded. The authors have a previous successful experience in the field, with a procedure proposed called MP Multi-Pier approach that relies into the substitution of a masonry wall in plane loaded with a composition of trusses, typically two vertical piers and braces. The intrinsic drawbacks of the MP method (mainly the large number of elements needed for the analyses) is here overcome, modeling each pier, spandrel and cross-joint belonging to a large and perforated wall with the minimum number of truss elements (piers and braces), having in mind to carry out very fast but reliable progressive failure analyses for large existing structures subjected to horizontal loads. To achieve such goal, for each single element used, suitable equivalent geometric and mechanical properties are assigned, assuring the equivalence element by element of the 1D mesh with the continuum in terms of elastic energy, behavior at peak and softening branch.MPM is benchmarked on two large scale perforated walls, where the results of several previous models are available from the literature, showing satisfactory accuracy in the reproduction of the global behavior and the activation of the mechanisms inducing the collapse.

Experimental research on load of transversal roof bracing due to geometrical imperfections of truss

The lattice or solid roof girders used in hall systems require transverse stabilization, most often realized with a transverse roof bracing and vertical bracing. The guidelines of EN 1993-1-1 for the design of the transversal roof bracing recommends considering loads resulting from geometric imperfection of the braced chord of the roof girder. According to the guidelines of EN 1993-1-1, the global imperfection of a braced chord is assumed as a bow imperfection with maximum deflection e0 (in the middle of the chord length), while the distribution of the normal force in the chord is simplified to a uniform distribution equal to the maximum compressive force NEd. On the basis of such assumptions, the load acting on the bracing from the imperfected girder is determined as a uniformly distributed load. The article presents theoretical analysis formulated by the author and the results of experimental research that contradict the standard model. The experimental results concern the nodal load acting on the transverse roof bracing and resulting from the influence of the truss girder with geometric imperfection of the compressed chord. The experimental studies were carried out on a semi-natural scale models. The article describes in detail the models and the test stand, as well as the research methodology. The obtained experimental results were compared with the results of theoretical analyses. These results confirm the differences between the standard load acting on the bracing and the real load, and confirm the conclusions resulting from the analysis of the theoretical author's model.

Analysis of the influence of erection of scissor braces on the bearing capacity of the wheel-buckled steel pipe supporting formwork system

The supporting formwork system as one of the most commonly used temporary structures in the process of building construction, its safety accidents frequently occur. The wheel-buckled steel pipe supporting formwork system is a new type of system developed under this background, and scissor brace as a kind of component in the system, have played an important role in improving the bearing capacity of the system. This paper uses ABAQUS finite element analysis software to establish an accurate simulation model of the foundational frame, and on the basis of this model, explores the influence of different erection methods of vertical and horizontal scissor braces on the overall bearing capacity of the frame. When erecting vertical scissor braces to reinforce the foundational frame, priority should be given to erect on the outer facades around the frame, and secondly consider satisfying the arrangement on the three facades. In the process of erecting horizontal scissor brace, the priority of the erected horizontal layer should be considered, that is the sub-bottom horizontal layer, sweeping rod horizontal layer, middle horizontal layer, sub-top horizontal layer, top horizontal layer.

Experimental Investigations on Ultimate Behavior of Fabricated Mobile Scaffolds

A fabricated mobile scaffold has various components, including vertical members, horizontal members, braces, work plates, and castor wheels. In Korea, the structural performance of each member must be validated based on member-level structural safety criteria; this means that rigorous evaluation methods are required to secure the system-level structural safety of the fabricated mobile scaffold. To suggest rational system-level structural safety criteria and effective evaluation methods, the characteristics of the structural behaviors of the assembled structure must be investigated first. Unlike other temporary equipment, it is a product that requires convenience of use and ease of movement. Therefore, to secure the safety and usability of the structure, it is necessary to evaluate the ultimate behavior of a mobile scaffold fabricated with various material and structural types. In an experimental study, the ultimate mode and load-bearing capacity were investigated, and the appropriateness of the required performance of the mobile scaffold was reviewed. Three types of experimental test models with different materials (steel and aluminum) and stories (single-story and three-story erection) were selected and examined for vertical loads. Based on the experimental results, the ultimate behavior characteristics of the fabricated mobile scaffold were analyzed, and the ultimate load was identified.

Research on Large Deformation Mechanism and Countermeasures of Shallow Buried Soft Rock Tunnel with Abundant Water

In view of the obvious deformation characteristics of shallow buried soft surrounding rock tunnels affected by excavation disturbance, this article takes a Tunnel as the engineering background and combines the geological conditions of the tunnel to carry out on-site monitoring and analysis of surrounding rock deformation after tunnel excavation. The deformation after excavation has the characteristics of fast deformation speed, long duration and large deformation. In addition, the excavation position and step have an important influence on the settlement of the vault and the convergence of the surrounding rock. The settlement of the vault and the convergence of the surrounding rock caused by the excavation of the upper and middle steps account for 61.16% and 63.34% of the total deformation respectively. Through the analysis of large deformation and collapse phenomenon, it is known that the large deformation mechanism in the cave mainly includes soft rock plastic flow and progressive loosening expansion. The soft rock plastic flow caused phenomena such as side wall bulging, top pressure and steel arch distortion, and the progressive loosening and expansion caused the collapse of the tunnel face and surface cracks. Finally, according to the principles of the New Austrian Method, temporary support (transverse bracing + vertical bracing) + grouting anchor pipe + spray-mixing coordinated support was used to construct the pipe shed at the same time, and the support was optimized, the leading small conduit was encrypted, and added Measures such as temporary invert and lock-foot anchor pipe have successfully dealt with the large deformation section of the collapse, and the treatment effect is good, which can provide reference and reference for similar projects.

Damage to the Vertical Braces of Industrial Buildings

The article describes the types of vertical connections of industrial buildings, presents the results of surveys, describes typical defects: bends of the connecting grid, cutouts of elements, local bends and curvature of branches of connections, destruction of attachment points. The description of unique damages of vertical connections is given: cut branches of connections, fastening of connections to crane beams, change of the design decision of connection. In conclusion, the analysis of zones of formation of defects and grouping of defects by zones of formation is performed.

An analytical formulation to evaluate natural frequencies and mode shapes of high-rise buildings

Abstract In this paper, an original analytical formulation to evaluate the natural frequencies and mode shapes of high-rise buildings is proposed. The methodology is intended to be used by engineers in the preliminary design phases as it allows the evaluation of the dynamic response of high-rise buildings consisting of thin-walled closed- or open-section shear walls, frames, framed tubes, and dia-grid systems. If thin-walled open-section shear walls are present, the stiffness matrix of the element is evaluated considering Vlasov’s theory. Using the procedure called General Algorithm, which allows to assemble the stiffness matrices of the individual vertical bracing elements, it is possible to model the structure as a single equivalent cantilever beam. Furthermore, the degrees of freedom of the structural system are reduced to only three per floor: two translations in the x and y directions and a rigid rotation of the floor around the vertical axis of the building. This results in a drastic reduction in calculation times compared to those necessary to carry out the same analysis using commercial software that implements Finite Element models. The potential of the proposed method is confirmed by a numerical example, which demonstrates the benefits of this procedure.