Horizontal Bracing Research Articles

Stability analysis of deep foundation pit with a double-row cast-in-place piles and diagonal steel lattice braces under sloped excavation conditions

Existing deep foundation pit support structures are commonly composed of external earth-retaining structures, internal horizontal bracings, and vertical columns. A closed bracing system, often formed by a horizontal support through a bracket board, frequently impedes vertical excavation and soil removal operations in the foundation pit, and the processes of assembly and dismantling are complex and time-consuming. This study presents a combined support system and construction method consisting of cast-in-place piles and diagonal steel lattice braces. For sloped excavation, diagonal braces were constructed by slotting through the reserved soil, allowing the use of a single layer of support within the excavation depth. This approach significantly optimizes the construction process, reducing both project duration and overall cost. The field monitoring results indicated that the support method effectively controlled the lateral displacement of the pile bodies. Field monitoring results demonstrated that the proposed support system effectively controlled the lateral displacement of the pile bodies. The adoption of a support-first, excavation-second approach significantly controlled the settlement of the ground surface around the foundation pit, thereby preventing excessive increments in the axial force of the supports due to the large longitudinal depth excavation. The calculation results of the three-dimensional finite element model for foundation pit excavation and support indicate that the proposed support method results in a decreasing ratio of the maximum lateral deformation depth of the pile body, denoted as δh-m, to the excavation depth He as the excavation depth increases. This implied that the displacement of the pile body was strictly controlled. When the depth of the foundation pit excavation exceeded 10 m, the maximum lateral deformation occurred below 10 m along the pile shaft. The diagonal steel lattice braces transferred the load to the top of the cast-in-place piles at the bottom of the pit, where the stress concentration occurred. During construction, special attention must be paid to the strength of the connection between the pile top and the connecting beams.

Effect of solid blocking on lateral bracing requirements for cold-formed steel wall studs

The effectiveness of horizontal bracing in increasing the strength of cold-formed steel (CFS) load-bearing walls has been widely acknowledged. However, while significant research has been conducted regarding the bracing requirements for CFS bearing walls, the effect of solid blocking, which prevents columns (studs) within the wall from rotating, has not been fully explored. In this study, we propose an analytical method to quantitatively assess the effect of solid blocking on bracing requirements for CFS load-bearing walls. This method is comprehensive as it can be applied to systems with different bracing patterns, load patterns, or non-identical columns (studs), and it accounts for the columns’ initial curvature and semi-rigid end connections. It has been verified that considering the solid blocking always decrease the bracing requirements because the existence of solid blocking increases the system’s stiffness and subsequently decreases the additional displacement as well as the brace force, as expected. An example consisting of 23 CFS studs is presented to illustrate how the effect of solid blocking on bracing requirements is influenced by the location and interval of solid blocking, the stiffness of column end connections, and the characteristics of tie bracing. The results indicate that the effect of solid blocking on bracing requirements increases when the location of solid blocking is closer to the anchor and the solid blocking interval is smaller. Moreover, a modification to the equation in AISI S100 is proposed to account for the effect of solid blocking on the strength requirement of tie bracing. Overall, this research contributes to a better understanding of the role of solid blocking in CFS load-bearing walls and provides insights for optimizing bracing design in practice.

Flexural and Shear Deformation of Basement-Clamped Reinforced Concrete Shear Walls.

For a precise analysis of buildings under earthquake effects, the load-deformation behaviour of the bracing walls must be comprehensively known. The horizontal bracing walls are often clamped in the basement; however, less attention has been paid to these walls' clamping parts in the past. This study presents three shear wall experiments (NW 1, NW 2, NW 3) with heights up to six meters in a scale of 1:1.5 to the real size. Measured were the force-displacement curve, the curvature distribution over the height, the crack pattern, and the crack opening and spacing. Twelve displacement transducers, an optical measurement system with eight cameras, and a manual crack measurement were utilised. Out of the measurements, the impact of the tension shift effect on the load-displacement curves could be quantified for the cantilever part of the walls. Additionally, it was found out that a sliding failure in the clamping part must be considered if the aspect ratio of H/L is equal to or less than one.

Optimal Reinforcement Model based on the Shape and Installation Position of the Lower Horizontal Bracing of a Ballastless Railway Plate Girder Bridge

Optimal Reinforcement Model based on the Shape and Installation Position of the Lower Horizontal Bracing of a Ballastless Railway Plate Girder Bridge

Pseudo-Dynamic Tests on Frame–Shear Wall Structure with Precast Concrete Diaphragm

In order to study how to improve the spatial action of precast monolithic composite floor slabs, and examine replacing the cast-in-place surface layer for reducing the weight of structure, we used pseudo-dynamic tests on one-quarter scale models of two-span and three-story frame structures. The lateral load tests compared the stresses and displacements with a cast-in-place floor frame–shear wall structure (SJ1) and a precast monolithic floor frame–shear wall structure with X horizontal braces at the bottom of the floor (SJ2). The results show the X horizontal braces can improve the spatial action. Structural integrity (SJ2) as well as the effective transmission of the horizontal force can be ensured by additional X bracing at the bottom of the rigidity of the floor without a cast-in-place concrete topping. The results show that X horizontal braces more effectively transfer horizontal stress, which provides a beneficial reference for similar research.

Analysis sedan vehicle structure in frontal impact using computer model

This paper presents an overview of Sedan vehicle structure based on frontal impact. The analysis results include parameters on the degree of deformation, the collision absorption ability of the Sedan vehicle structural model in accidents. The purpose is based on the comparison results to simulate the Sedan vehicle structure model that collides with other car chassis models at different speed levels, based on that, compares the crash analysis simulations to find the textures the frame absorbs the maximum impact energy and minimizes the deformation so as not to affect intrusion into the safe space of the passenger compartment of the vehicle. The results of this paper show that the frame structures such as the A-Pillars and Horizontal brace between the engine compartment and the passenger compartment need to be improved to increase the safety for the passengers inside. The study results are expected to be expanded in to optimize the engineering structures and improve the efficiency in various fields included shipbuilding, offshore structures, marine aquaculture structures, etc. Keywords: Structural, analysis, Sedan, vehicle structure, fontal impact.

Analysis and optimization of brace system in scaffold

Scaffold consists of horizontal components, vertical components and lateral braces, while the lateral stiffness of structure is mainly provided by brace system. Brace system can be classified into three groups: concentric brace, eccentric brace and knee brace. Concentric brace enables to offer greater stiffness, for providing direct load transfer. Eccentric brace and knee brace belong to ductile system, maintaining stability by energy consumption braces. Eccentric brace dissipates energy by deforming and buckling, while knee brace disposes energy by form a plastic hinges. Concentric brace is a common way for enhancing lateral stiffness in scaffold. Current studies aimed to investigate detail parameter effects in one brace pattern, while few comparative studies were carried on multiple brace pattern. In this paper, a simplified simulation method was proposed. Throughout simulation analysis, some regulations of brace arrangement were summarized, which provides a guidance during the scaffolding design and optimization process.

A Case Study of Tunnel Reinforcement Measure during Traffic Upgrading in Chongqing City, China

Because the urban tunnel is an essential knot of urban traffic and an easy blocking point in busy hours, upgrading the urban tunnel was necessary for the city after the tunnel being in service for a long time. However, to demolish the existing tunnel, some problems may be encountered, and these problems include occurrence of longitudinal cracks at the tunnel vault, increase of load due to infrastructure construction over the tunnel, unloading due to excavation of the rock over the tunnel, and uneven load due to asymmetric excavation or construction. To reinforce a cracked tunnel in Chongqing City, China, steel arches were installed to improve its bearing capacity, but some steel arches failed during the excavation of ground over the tunnel. Therefore, the scheme of “steel arch + shotcrete + tube column + transversal horizontal bracing” (hereinafter referred to as SASTCT) was proposed to ensure tunnel safety due to unloading and uneven load during the subsequent construction procedures. Numerical analysis indicated that the SASTCT measure can ensure the safety of the traffic and subsequent construction, which can provide some suggestions for similar tunnel upgrades in the future.

A general simplified method for static and free vibration analysis of coupled shear walls of a bay

In recent years, coupled shear walls have been used more often because they provide a significant percentage of the total stiffness of a tall building total horizontal bracing system. This article presents an analytical procedure for the static and dynamic analysis of coupled shear walls of a bay using a continuous model type – CTB of three fields. The coupled shear wall is modeled as a continuous structure consisting of the parallel coupling of a Timoshenko extensible beam and a shear beam. Using a variational approach, the equilibrium equations, constitutive laws, and boundary conditions are derived by applying Hamilton’s principle to the relevant Lagrangian function. Closed-form solutions are provided for the static deflection of the coupled shear wall under general profile lateral loads and the periods of vibration of the coupled shear wall under vertical loads uniformly distributed along its height. A validation of the static analysis was carried out, and to find the range of validity of the continuous model and proposed solution methods, a parametric analysis was carried out. The results are encouraging and show that the proposed analytical solutions have excellent correspondence with respect to the finite element method; they are accurate, reliable and involve low computational cost at a preliminary stage, and can be used as a verification method at the final stage of structural analysis and design.

Urban Viaducts at Section 1 of the “Tren Maya” railway

AbstractThe new Urban Viaducts at the Section 1 of the “Tren Maya” railway are located in southern Mexico, at the municipalities of Tenosique (State of Tabasco) and Candelaria and Escárcega (State of Campeche).The structural solution for the urban viaducts' deck is made of a reinforced concrete slab with a pair of “I” main steel girders. The girders have vertical bracing trusses, in order to reduce the distortion of the cross‐section, and a lower horizontal bracing truss, to close the torsional circuit. Steel diaphragms are located at the supports to transfer vertical and horizontals forces to the column.Viaducts consist of a succession of simply supported 40 m spans. The lengths of the viaducts are: 2920 m Tenosique, 990 m Candelaria and 1080 m Escárcega.The viaducts are located in a zone of high seismicity hazard, so the columns' design has been developed by a displacement‐capacity analysis. As a result, they consist of a single shaft on which rests a pier cap, both of reinforced concrete.This typology has been chosen because of the benefits of its construction process, which allows the execution of the spans to be independent. The steel structure of the deck also allows to reduce its mass, what helps to reduce the dimensions of the substructure.

ФОРМУЛА ДЛЯ НИЖНЕЙ ОЦЕНКИ ПЕРВОЙ ЧАСТОТЫ СОБСТВЕННЫХ КОЛЕБАНИЙ ФЕРМЫ ТРЕХГРАННОЙ БАШНИ

A scheme of a statically determinate tower-type spatial truss is proposed. Three lateral faces of the structure have double diagonal lattices, from below the truss rests on six racks and three additional horizontal lateral braces. The problem of the first natural frequency of free oscillations of the structure is solved. The inertial properties of the truss are modeled by the masses in its nodes. Each mass has two horizontal degrees of freedom. To obtain an analytical expression for the dependence of the lower limit of the oscillation frequency on the number of panels, the approximate Dunkerley method is used. The forces in the truss rods are found from the solution of the system of equilibrium equations for the nodes. The matrix of the system of equations is compiled in the Maple computer mathematics system. The rigidity of the structure is determined using the Mohr integral. A series of solutions obtained for a different number of panels is generalized to an arbitrary case by induction. For sequences of coefficients in the solution, linear recurrent equations are compiled and solved. The analytical solution is compared with the numerical solution of the problem of the vibration spectrum of the structure. It is shown that the first frequency of the spectrum is higher than the analytical estimate by no more than 30%. The accuracy of the estimate depends to a greater extent on the number of panels. As the number of panels increases, the accuracy of the resulting estimate increases. A trusses with only an even number of panels are considered. It is noticed that with an odd number of panels, the determinant of the system of equilibrium equations of nodes vanishes, which indicates the kinematic degeneration of the structure.

Analytical Investigation of the Effects of Secondary Structural Members on the Structural Behaviors of Transmission Towers

High-voltage transmission towers consist of structures that are designed to avoid the risk of electric shock and prevent the risk of collapse. Hence, for efficiency, they are generally designed as high-rise towers. The main tower posts are the primary structural members that resist loads under various load conditions. Therefore, the contribution of the secondary members to securing the stiffness and strength of the main posts by reducing the effective buckling length is an important one. However, we lack detailed secondary member design criteria. In this study, we observed the structural effects of the horizontal members and braces on the torsional stiffness, elastic buckling strength, and load-carrying capacity of a transmission tower using various structural analysis methods, including linear elastic, eigenvalue, and geometric nonlinear and inelastic analyses, under governing load combinations. According to the analytical results, it is the brace spacing rather than the horizontal members that substantially affects the structural performance. Therefore, we can minimize the number of horizontal members if we erect sufficient brace members. If the brace spacing is wide, then the horizontal members should be erected to create K bracing, thereby enhancing the buckling resistance of the main posts.

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.

Investigation of Intermediate-Height Horizontal Brace Forces under Horizontal and Vertical Loads including Random Initial Imperfections

In engineering practice, longitudinal brace systems for column-braced systems are designed to resist both horizontal and vertical loads. In previous experimental research on horizontal brace forces for column-braced systems of intermediate height, only vertical loads were considered. Hence, this paper presents a numerical simulation of numerous column-braced systems subjected to horizontal and vertical loads. In the numerical simulation, second-order analysis was adopted, and the Monte Carlo method was used to incorporate the randomness of initial imperfections in the horizontal brace and column. From the finite element (FE) analyses and probability model statistics, the normal probability density equation for intermediate-height horizontal brace forces under horizontal and vertical loads was obtained, and the corresponding design intermediate-height horizontal brace forces were determined and compared with those under vertical loads only. The results indicate that the design intermediate-height horizontal brace forces under horizontal and vertical loads are significantly greater than those under only vertical loads, and that the design intermediate-height horizontal brace forces under horizontal and vertical loads are also greater than the simple superposition results of horizontal loads and intermediate-height horizontal brace forces under only vertical loads.

Influence of bracing on the mechanical properties of Ti6Al4V lattice structures

In this paper, three novel lattice structures were designed based on the body-centered cubic (BCC) unit cell. These lattice structures with different porosities were fabricated by selective laser melting (SLM). We investigated the mechanical properties, deformation-induced failure modes, and energy absorption of these structures under uniaxial compression. We added the bracings in a BCC unit cell, resulting in the shift from the bending-dominated mode to the stretch-dominated mode during deformation. Specifically, the vertical and horizontal bracings dramatically increased the compressive strength of the lattice structures. Importantly, the combination of the two bracings improved the strength by 287 %. Additionally, while boosting energy absorption, the bracings prevented the original structure from the failure-induced efficiency decrease in energy absorption. These findings are expected to provide experimental data and a scientific basis for the design and engineering applications of 3D-printed BCC unit cell structures.

Warp-Free TEM Sample Preparation Methods Using FIB/SEM Systems.

Warping is a limiting factor when preparing transmission electron microscopy (TEM) samples using focused ion beam (FIB)/scanning electron microscope (SEM) systems. The conventional FIB sputtering process leaves at least one side of the lamella too thin to provide structural support to offset inherent stresses. As a result, warping can occur impacting imagining and reducing the potential size of lamellae. For example, capturing more than a few back-end metal layers in a 3 μm wide cross-section lamella can be difficult. Frequently, TEM analysts must perform multiple stage adjustments to analyze such a sample. In this paper, two methods are presented that enable FIB/SEM operators to prepare TEM samples where the thinned region of interest is surrounded by thick structures. As a result, these methods reduce warping and enable the fabrication of TEM lamellae not possible by conventional means. For example, these methods have been used to produce a 10 μm wide by 8 μm tall cross-section TEM sample that captured front-end transistors and 14 back-end metal layers. Furthermore, warping was so limited that only one alignment was needed by the TEM analyst to complete the imaging of the sample. The methods, called the horizontal bracing and window methods, make use of the deposition of low-Z amorphous films that are electron transparent in the TEM.

Bracing requirements for multiple parallel nonidentical columns with initial curvature

For a system consisting of multiple columns, horizontal discrete braces are often used to increase the system’s strength by decreasing the effective length of columns. Since the bracing requirements for such systems in current design standards were developed based on the assumption of identical columns with pin-ends, an analytical method is proposed to evaluate the ideal brace stiffness and brace forces for multiple columns by accounting for the stiffness interaction among columns and braces. For systems with uniform column lateral stiffness, the explicit solution for the maximum brace force is derived, and a simple formula is subsequently proposed by fitting the analytical results. The proposed formula explicitly accounts for the influences of column initial curvature and semi-rigid end connections on the maximum brace force. The method is comprehensive and applicable to multi-column systems with nonuniform column lateral stiffness, which can result from differences in column sizes, end connections, or applied loads. The results obtained from the proposed formulae are verified against those of finite element analyses. The ideal brace stiffness and brace forces for a system containing a distinctive column with a greater moment of inertia than the other columns are investigated. The results show that the location of the distinctive column affects the magnitudes of the ideal brace stiffness and the maximum brace force, which is yet to be considered in current design standards.

Incremental dynamic analysis of steel storage racks subjected to Chilean earthquakes

Steel storage racks are structures commonly used by all industries in Chile; nevertheless, due the seismic hazard in the country and its configurations, these structures are highly vulnerable to earthquakes and no specific regulations exist to design them. In this research, the seismic performance of steel storage racks subjected to Chilean Earthquakes was evaluated using nonlinear pushover and nonlinear dynamic analysis. The studied models consider different heights and global slenderness ratios in both directions and soil types. Racks were evaluated using an Incremental Dynamic Analysis (IDA) according to FEMA P695. Deformation values were exceeded in the down-aisle direction and the use of braces was necessary to control the interstory drift and high deformation levels. Also, the expected level of damage for drift design limits in models unbracing is not enough to keep the operation of the structures and more severe regulations are necessary to achieve a performance in agreement with Chilean design philosophy. Finally, the use of horizontal and lateral bracing improves the seismic performance of steel racks.

STUDY ON TENSILE FORCE TRANSMISSION PERFORMANCE OF DECK PLATE

Floors and roofs in buildings need to be capable of transmitting horizontal forces, such as seismic forces, from the horizontal structure to the vertical structure, in addition to the role of transmitting the weight acting in the vertical direction to the support beams. For this purpose, reinforced concrete slabs are generally used or horizontal braces are installed. However, this requires high material and transportation costs, and several weeks for curing period after concrete is poured. In this study, the possibility that deck plates used as roofing materials can transfer horizontal forces sufficiently without concrete or bracing was investigated. The initial stiffness, maximum load, and yield load are considered, and the yield load is compared with the converted TB (turnbuckle) brace diameter to evaluate the bearing force. Therefore, tensile experiments of deck plates were conducted with the parameters of plate thickness, wave height, and tensile angle. The tensile angle is the angle at which the tensile force is applied to the deck plate perpendicular to the groove direction. As a result, it was found that the lower the wave height and the thicker the plate thickness of the specimen, the higher the stiffness. The yield strength equivalent to TB brace diameter M14 was confirmed for the specimen with a wave height of 50 mm and a plate thickness of 1.6 mm at all tensile angles.

STUDY ON TENSILE FORCE TRANSMISSION PERFORMANCE OF DECK PLATE

Floors and roofs in buildings need to be capable of transmitting horizontal forces, such as seismic forces, from the horizontal structure to the vertical structure, in addition to the role of transmitting the weight acting in the vertical direction to the support beams. For this purpose, reinforced concrete slabs are generally used or horizontal braces are installed. However, this requires high material and transportation costs, and several weeks for curing period after concrete is poured. In this study, the possibility that deck plates used as roofing materials can transfer horizontal forces sufficiently without concrete or bracing was investigated. The initial stiffness, maximum load, and yield load are considered, and the yield load is compared with the converted TB (turnbuckle) brace diameter to evaluate the bearing force. Therefore, tensile experiments of deck plates were conducted with the parameters of plate thickness, wave height, and tensile angle. The tensile angle is the angle at which the tensile force is applied to the deck plate perpendicular to the groove direction. As a result, it was found that the lower the wave height and the thicker the plate thickness of the specimen, the higher the stiffness. The yield strength equivalent to TB brace diameter M14 was confirmed for the specimen with a wave height of 50 mm and a plate thickness of 1.6 mm at all tensile angles.