Arch Structure Research Articles

Design of Periodic Arched Structures Integrating the Structural Nonlinearity and Band Gap Effect for Vibration Isolation

Design of Periodic Arched Structures Integrating the Structural Nonlinearity and Band Gap Effect for Vibration Isolation

Numerical modeling of a masonry arch structure

To investigate the structural behavior and estimate the strength capacity of masonry arch structures, experimental testing can be challenging at large scales. In such a case, numerical modeling is considered as an interesting alternative. In this work, two ready-to-use modeling techniques are proposed. The first one is based on the detailed micro-modeling in which the brick and mortar were modeled using concrete damaged plasticity model and the brick-mortar interface was modeled by the surface-based cohesive behavior model. These constitutive laws are already implemented in the ABAQUS environment without the need for specific subroutines. The second technique is based on the homogenization approach to derive the equivalent characteristics of masonry, which is then modeled as one continuous element. Both techniques were used to simulate the experimental behavior of a masonry arch subjected to in-plane bending. Finally, comparison between experimental and numerical results of the two methods shows the capability of the proposed homogenization approach to simulate the behavior of masonry arch structures with a sufficient degree of accuracy and a reduced computational cost.

Диференційний підхід до хірургічної корекції вродженої лійкоподібної деформації грудної клітки в дітей

Pectus excavatum (PE) is the most common defect – it occurs in 0.1–0.8% of the population. This defect is characterized by changes in the cardiorespiratory system, induction of concomitant spinal deformities, severe psychological problems. Nuss surgery and most of its modifications doesn’t provide good results in the treatment of atypical anatomical variants of deformity; it is characterized by displacement and eruption of plates, chronic postoperative pain syndrome, deformity of the ribs, which encourages the search for ways to solve these problems. Purpose – to improve treatment results in patients with various forms of PE by introducing their own differentiated options for Nuss surgery and choosing the optimal size of fixation plates; to analyze the results of treatment. Materials and methods. H. J. Park classification has been used. Variants of Nuss surgery have been developed for the following types of IIA1; IIA2; IIA3; IIB, IIC. All surgeries begin with a free extension of the anterior chest wall to the physiological position with ligatures imposed on the sternum’s lower third and ribs. Horizontal plate fixation has been used in IIA1, IIA2, IIA3 types, and in IIB and II C types – its oblique fixation with a lower location of the end of the plate on depressed side. In both versions plate stabilizers are rigidly fixed to 2 (sometimes 3) ribs on both sides under the bones, and in IIB and II C types the plate stabilizer is fixed ventrally at the depressed side and dorsally at the bulging side. For surgical treatment of wide and widened deformation types we use two plates (IB, IIA2, IIA3); one plate is used for treatment of IA, IIA1, IIB, IIC deformations. In the case of the common version of the IIC – two plates. When installing two plates, the shorter upper plate is installed according to Pilegaard at IB, IIA2; standard length – with IIA3 and common version of IIC. We’ve done a mathematical modeling of the correcting plate functioning as a monolithic arched structure with rigidly fixed ends with the determination of the optimal plate width at a thickness of 2.2 mm. Also we’ve analyzed surgical treatment of 55 patients with PE operated in 2018–2020 (ІА – 25; ІВ – 6; ІІА1 – 7; ІІА2 – 3; ІІА3 – 2; ІІВ – 6; ІІС – 4). Results. Excellent and good cosmetic and functional results were revealed. Postoperative complications – 4 (7.3%). Two postoperative local asymmetric keel-like deformations were noted: one for each in treatment of IIB and IIC (successful treatment is carried out in an individual dynamic compression brace system). In one case, simple pneumothorax was diagnosed, and in another – eruption of one of the two corrective plates. Practical recommendations for determining the optimal plate width at its length of 280 mm and less – 12 mm; 290–300 mm – 13 mm; 310–320 mm – 14 mm; 330–340 mm – 15 mm; 350–360 mm – 16 mm. One month after the operation, 26 patients were surveyed according to the NRSP scale and the following results were obtained: among the operated patients with II degree of deformity: 1 point – 50.0% of patients, 2 points – 25% of patients, 0 points – 25.0% of patients (mean score – 1.0); among patients with III degree of deformity 1 point – 25% of patients; 2 points – 50%, patients 3 points – 12.5% of patients; 0 points – 12.5%, average score – 1.63. There was no chronic postoperative pain. Conclusions. Key to proposed differential approach in the PE treatment is careful planning of the operation (correct selection of the number of plates, their size, method of installation and fixation depending on the PE anatomical variant). This allows to achieve good and excellent cosmetic and functional results; minimize the number of postoperative complications. The research was carried out in accordance with the principles of the Helsinki declaration. The study protocol was approved by the Local ethics committee of all participating institutions. The informed consent of the patient was obtained for conducting the studies. No conflict of interest was declared by the authors. Key words: Nuss surgery modifications, atypical forms of pectus excavatum.

Numerical and dimensionless analytical solutions for circular arch optimization

In the design of arched structures, the pre-design phase assumes a crucial and even more evident importance. Once the requirements of the project are determined, via the programming process, the design phase begins. The selection of the most suitable shape appeared to be more and more crucial and represent the pre-sizing of the structure. Preliminary evaluation of the design program, schedule and construction budget needs to restrict the type and the characteristics of the structural shape of the arch that will be used. The aim of the present paper is to propose, firstly, a fast numerical resolution method to optimize the circular shapes via the selection of the best lowering degree and cross-sections for the arch, minimizing the total volume of the structure. To this purpose, a self-made code is proposed, able to solve, numerically, the ODE (ordinary differential equation) of the arch. The results, changing the spans, the shallowness ratio and the cross-section of the arches are considered in order to obtain the minimum employed volume and can be used as a first approximation in the design process. Furthermore, an analytical closed form solution is proposed by a dimensionless approach to identify the maximum stress behavior in the arches by a dimensionless parameter (η). Also in this case the proposed method is able to offer a valid way to evaluate different arch configurations, and can be used in the pre-design phases (conceptual design) for circular and segmental arches covering different spans.

High efficient 3D solar interfacial evaporator: Achieved by the synergy of simple material and structure

Solar steam generation has attracted tremendous attention because of severe freshwater scarcity and people's high degree of recognition of solar energy. However, photothermal conversion efficiency and thermal management capability are still the key factors restricting solar steam generation. Here, we prepared an efficient 3D solar interfacial evaporator via material selection and simple structural design. The microstructure shows that the air-laid paper is made up of two layers of unidirectional fibers of different shapes, which can provide efficient water transportation and strong photon capture capability. As for macrostructure, the 3D arched evaporator can greatly reduce heat conduction loss by reducing the contact area between the evaporator and bulk water and achieve high efficiency of solar utilization throughout the day. Finally, the 3D arched structure is beneficial for steam diffusion. As a result, the evaporator showed excellent photothermal conversion efficiency and thermal management capability by the synergy of microstructure and macrostructure. It has achieved an evaporation rate of 2.0 kg m−2 h−1 under 1 sun illumination with an energy utilization efficiency of 93.5%, and the efficiency remained above 90% when the incidence angle changed from 90° to 45°, which can produce clean water from seawater and contaminated water.

DEM simulation analysis of the improvement in particle discharge flowability using adhesive force distribution models based on admixed particle coating

Particle flowability can be improved by admixing particles smaller than the original particles (main particles). However, the details of the mechanism of this improvement are not yet fully understood. In this study, we used a discrete element method simulation to investigate the effects on the particle flowability of the adhesive force distribution at each contact point based on the admixed particle coating. We used the non-uniform, random, and uniform surface adhesive force distribution models and calculated the discharge flow rates. The non-uniform models had a larger discharge flow rate compared with the other models because the non-uniform adhesive force distribution destabilized the force balance in the bed, and thus destabilized the particle arching structure, which generated discontinuous layers more frequently and improved the flowability. Consequently, in a smaller particle admixing system, the adhesive force distribution at each contact point would help to improve the flowability.

Study on Applicability of Double Layer Superimposed Primary Support Arch Cover Method for Large-Span Station in Upper Soft and Lower Hard Stratum

The Qingniwaqiao Station from Dalian's 5th Metro Line in China has exhibited extremely complicated stratum structure, named as the upper soft lower hard (US-LH) stratum. In accordance with the characteristics of the stratum in which the station is located, the special structure form of double layer superimposed primary support arch cover method is presented. Numerical simulations and field monitoring are carried out to study the construction process. Subsequently, the double-layer primary lining, anchor and steel pipe pile are compared and analyzed respectively. The results show that the double-layer primary lining increases the safety reserve when the initial support is removed, and it can beneficially inhibit the deformation of the arch structure resulting in smaller ground surface subsidence. Anchor and steel pipe pile enhance the bearing capacity of rock mass on both sides of the station. The method has advantages in ground surface subsidence control and supporting structure safety. It is safe and feasible to create a large-span subway station using double layer superimposed primary support arch cover method in US-LH relative stratum.

Effects of obesity and foot arch height on gait mechanics: A cross-sectional study.

Foot arch structure contributes to lower-limb joint mechanics and gait in adults with obesity. However, it is not well-known if excessive weight and arch height together affect gait mechanics compared to the effects of excessive weight and arch height alone. The purpose of this study was to determine the influences of arch height and obesity on gait mechanics in adults. In this study, 1) dynamic plantar pressure, 2) spatiotemporal gait parameters, 3) foot progression angle, and 4) ankle and knee joint angles and moments were collected in adults with normal weight with normal arch heights (n = 11), normal weight with lower arch heights (n = 10), obesity with normal arch heights (n = 8), and obesity with lower arch heights (n = 18) as they walked at their preferred speed and at a pedestrian standard walking speed, 1.25 m/s. Digital foot pressure data were used to compute a measure of arch height, the Chippaux-Smirak Index (CSI). Our results revealed that BMI and arch height were each associated with particular measures of ankle and knee joint mechanics during walking in healthy young adults: (i) a higher BMI with greater peak internal ankle plantar-flexion moment and (ii) a lower arch height with greater peak internal ankle eversion and abduction moments and peak internal knee abduction moment (i.e., external knee adduction moment). Our results have implications for understanding the role of arch height in reducing musculoskeletal injury risks, improving gait, and increasing physical activity for people living with obesity.

Dynamic crushing behaviors and enhanced energy absorption of bio-inspired hierarchical honeycombs with different topologies

In order to pursue good crushing load uniformity and enchance energy absorption efficiency of conventional honeycombs, a kind of bio-inspired hierarchical honeycomb model is proposed by mimicking the arched crab shell structures. Three bio-inspired hierarchical honeycombs (BHHs) with different topologies are designed by replacing each vertex of square honeycombs with smaller arc-shaped structures. The effects of hierarchical topologies and multi-material layout on in-plane dynamic crushings and absorbed-energy capacities of the BHHs are explored based on the explicit finite element (FE) analysis. Different deformation modes can be observed from the BHHs, which mainly depend upon hierarchical topologies and impact velocities. According to energy efficiency method and one-dimensional (1D) shock theory, calculation formulas of densification strains and plateau stresses for the BHHs are derived to characterize the dynamic bearing capacity, which is consistent well with FE results. Compared with conventional honeycombs, the crushing load efficiency and energy absorption capacity of the BHHs can be improved by changing the proper hierarchical topology and multi-material layout. These researches will provide theoretical guidance for innovative design and dynamic response performance controllability of honeycombs.

Anti-frost heave design method for a parabolic canal based on the hydraulic optimal solution set in seasonally frozen regions

Parabolic canals are commonly used in seasonally frozen regions because of their excellent hydraulic characteristics and frost heave resistance. However, severe frost damage can still occur, mainly because the design of canals is based on experience, and the analytical mechnical models and design methods are limited. First, the frost heave characteristics of parabolic canals were analysed, and the canal lining was simplified as an arched thin shell structure under the normal frost heave force, tangential freezing force, and gravity. Second, an analytical mechanical model of frost damage to the lining was established, and the equations for the axial force, bending moment, tensile stress were derived; the accuracy of the model was verified by field measurements and numerical simulations of a canal case. Third, the effects of groundwater depth and canal size were analysed, and the frost damage mechanism was investigated. Fourth, the anti-frost heave design method of a canal based on the hydraulic optimal solution set was proposed, and the method was encapsulated into digital design software with Python language. This mechanical model can explain the frost damage of the canal, and the nonuniform frost heave of foundation soil caused by different groundwater depths in different parts of the canal is the cause of lining damage. The bi-objective optimization design method can consider the hydraulic performance and anti-frost heave performance of the canal, and the digital design software can assist engineers with developing a quick and accurate design approach. The research results can provide a theoretical basis and technical means for cold-region canal design.

Determination of free vibration properties of masonry arch bridges using the dynamic stiffness method

Masonry arch bridges constitute over half of the European bridge stock. The dynamic response of these bridges to traffic loads is influenced by their free vibration properties, i.e. their natural vibration frequencies and mode shapes. However, these properties have not been systematically examined to date. This paper utilises the dynamic stiffness method (DSM) to obtain an improved fundamental understanding of the free vibration properties of idealised single and multi-span arch bridges. In this approach, the piers and arches are modelled as an assembly of linear Timoshenko beam segments, the backing and infill are represented with axial struts and the underlying soil with concentrated spring elements. These idealisations enable rapid but accurate calculations of in-plane free vibration properties. To demonstrate this, the proposed procedure is applied to a simply-supported arch structure, a small-scale single-span arch bridge model and a multi-span arch bridge, where published experimental data is available. Then, free vibration analyses of representative single and multi-span arch bridges are performed. The results obtained from DSM analyses agree with detailed 3D finite element models and reveal the critical influence of backing elements and the interactions between adjacent spans on free vibration properties. Lastly, a range of arch bridge geometries are examined to reveal the shortcomings of existing provisions for modal frequency estimation in codes of guidance.

Arch Height Index, Arch Rigidity Index and Arch Stiffness Values in a Symptomatic Population

Studies of arch height index (AHI), arch rigidity index (ARI), and arch stiffness have primarily focused on healthy populations. Normative values of the aforementioned measurements in a pathologic sample may be useful in identifying relationships between arch structure and pathology. AHI was obtained bilaterally at 10% and 90% weightbearing conditions using the AHI measurement system. ARI and arch stiffness were calculated using AHI measurements. Dependent t tests compared right and left, dominant and nondominant, and injured and noninjured limbs. Dominant feet were compared between sexes using independent t tests. Relationships between arch stiffness and subcategories were examined using the coefficient of determination (R2). One-way analyses of variance determined differences between arch structure and number of pathologies or body mass index (BMI). A total of 110 participants reported one (n = 55), two (n = 38), or three or more (n = 17) pathologies. Plantar fasciitis (n = 31) and hallux valgus (n = 28) were the most common. AHI, ARI, and arch stiffness did not differ between limbs or sexes for any comparisons. Between subgroups of BMI and number of pathologies, BMI influenced AHI (10% weightbearing) and arch stiffness (P < .05). Arch stiffness showed a weak relationship to AHI, where a higher AHI was associated with a stiffer arch (R2 = 0.06). Normative arch structure values were established in a pathologic sample with a large incidence of plantar fasciitis and hallux valgus. Understanding relationships between arch structure and pathology is helpful for clinicians and researchers.

Research on Anchor Cable and C-Shaped Tube Support Method in Deep Layers Roadway, Experimental Study, and Numerical Simulation

In roadways with high ground stress or burial depths, the joints distributed within rock formations are subject to complex stresses and interlayer misalignments frequently. Rock bolts and cable bolts anchored in the rock formations are subject to tensile and shear forces. Most of the bolts used in roadway engineering are local anchored, resulting in insufficient shear strength at the bolt free end close to roadway surface and increasing bolts breaking. The anchor cable and C-shaped tube (ACC) is a highly prestressed cable bolt that can withstand high shear force in its free end. This paper examines the effect of the relationship between C-shaped tube length and joint location on the shear resistance of ACC by double shear tests. To fully exploit the ACC’s shear resistance, the C-shaped tube ends should be at least 30 cm beyond the joint. The effect of preload and concrete spray thicknesses on roadway deformation and plastic zone is investigated by numerical simulation. Results show that ACC and concrete spraying layer can form a stable extruded arch structure, so that the broken and soft rock within the loosen zone is in three-dimensional-stress state, effectively improving surrounding rock properties and controlling its deformation size. Based on these results, the ACC support design method is proposed.

The Community of Shared Future for Mankind and China’s Legalist Turn in International Relations

Abstract The introduction presents China’s legalist turn in international relations against the background of the Trump administration’s backlash against international law and international organizations. The next section retraces the origins and evolution of the Community of Shared Future for Mankind (CSFM) up to its incorporation in the preamble to the Chinese Constitution. Section 3 examines the main tenets of the CSFM on the basis of XI Jinping’s writings with the visual aid of a “paifang” (“牌坊”). In this representation of a Chinese architectural arch or gateway structure, the “foundation” of the CSFM is, first, assimilated to China’s acknowledgement of the centrality of “interdependence” in the international community. Second, the “pillars” of the CSFM are identified as the goals of global peace, international common security, inclusive international development and international ecological civilization. Third, the “wooden beams” that bind the CSFM together are assimilated into the principles of sovereign equality, inter-civilizational dialogue and multilateralism, while the principle of “win-win” cooperation is represented as the CSFM’s “frontispiece”. The concluding section points to the benefits of China deepening its legalist approach to international relations as the most fitting companion to its grand strategy of “peaceful/development rise”.

PENGGUNAAN SISTEM STRUKTUR RANGKA ATAP TIPE PELENGKUNG 3 SENDI

So far, the system of the roof structure of residential and office buildings is dominated by conventional frame types. The use of a 3-joint arch structure system is only familiar to warehouse buildings and the like. The purpose of this study is to identify the feasibility of using type 3 joint arches on the roof of a residential building. The research scenario is focused on calculations using SNI 7973-2013, namely Design Specifications for Wooden Construction and Specific Static Structural Analysis Methods for 3 Joint Arch Structures based on the length of the truss span model, which is 9 m. The calculation result indicates that 1). The 3-joint curve type is worth using as it proves stable and safe 2). The distance between the truss of the roof truss affects the dimensions of the truss. The implication is that the construction of the roof of a residential house can use a 3-joint arch structure system while the basic material for modeling uses Code E20 wood material with Quality B, depending on the length of the span and the slope of the roof.&#x0D;

A novel hemp-fiber bio-composite material for strengthening of arched structures: Experimental investigation

Fiber reinforced composites represent an alternative to traditional techniques for strengthening and retrofitting masonry structures. Within the growing environmental awareness, the development of composite materials to replace conventional synthetic fibers and polymeric matrices has become a crucial issue. In this paper, a novel sustainable composite material consisting in hemp fibers and a natural matrix made of a mix of ground clay bricks and organic binder is proposed. Experimental tests are carried out in order to estimate the mechanical characteristics of the single composite components. The structural performance of polycentric masonry arches strengthened at the extrados first with only natural matrix and then with the bio-composite material (i.e. hemp fibers and biodegradable matrix) is investigated. Single point vertical load tests and tilt tests are carried out in order to assess the effectiveness of the strengthening by comparing the results with those obtained with unstrengthened masonry arches.

A new deck arch bridge and a study on its mechanical properties by FE and experiment methods

In this study, a new type of deck arch bridge was proposed based on the triangle stability principle, and its mechanical properties were tested. The new deck arch bridge—named the superposed truss arch bridge—consists of main arches, auxiliary arches, a girder, and web members. These components adopt steel structures and are connected into a series of triangles to form a superposed truss structure. The new structural system design retains the advantages of the truss and arch structure. Additionally, the rise-span ratio of the main arch can be smaller in the new system design, so the rise height is smaller, which can decrease construction difficulty. The underlying mechanical principles of the new bridge were explained. A new type of railway deck arch bridge with a 650 m span was designed, and the finite element method was used to analyze its stiffness, strength, stability, and dynamic properties and the corresponding effects of the arch-axis coefficient, rise-span ratio, and span length on the mechanical properties. An experiment was carried out on a new deck arch bridge and a conventional deck arch bridge with the same span (10 m) to compare their performance. The results showed that the new deck arch bridge exhibited good mechanical properties while being inexpensive and easy to construct, which makes it suitable for high-speed railway bridges.

DEM Simulation of the Load Transfer Mechanism of a GRPS Embankment with a Fixed Geogrid Technique

As a new technique, a fixed geogrid in a geogrid-reinforced and pile-supported (GRPS) embankments has been used to reduce the total and differential settlement. To investigate the load transfer mechanism of the fixed geogrid technique of a GRPS embankment, three discrete element method (DEM) models of pile-supported embankments were established, including an unreinforced embankment, a geogrid reinforced embankment, and a fixed geogrid reinforced embankment. The efficacy of the pile, the evolution law of the contact force chain and the axial force of the reinforcement, and the microscopic load-bearing structure of the soil were investigated. Numerical simulation results showed that the embankment self-weight and surcharge load were transferred to the pile through the soil arching and tensile membrane effect. The settlement could be effectively reduced via the addition of the reinforcement, and the fixed geogrid technique was more conducive to improving the load-bearing ratio of the pile than the traditional reinforcement technique. Compared with the traditional technique of a GRPS embankment, the fixed geogrid technique had a better effect on reducing the total and differential settlement. With the increase in the surcharge load and the settlement of the soft subsoil, the reinforcement transferred a greater load to the pile. The results also showed that the stress of the embankment fill was concentrated at the pile top in all three models. The GRPS embankment with a fixed geogrid technique had a lower soil stress concentration than the other two cases. The contact force chain and stress in the embankment also showed that the reformation of the microscopic load-bearing system of the embankment fill was the internal mechanism that caused the development of the soil arching and the redistribution of stress. Furthermore, the evolution of the fabric parameters in the arching area could reflect the evolution of the soil arching structure. In the fixed geogrid case, the proportion of the load transferred to the pile from the soil arching effect was reduced, and the vertical load transferred to the pile top by the tensile membrane effect accounted for 22–28% in this study. Under the combined effect of the tensile membrane and the soil arching, the efficacy of the pile could increase by 10%.

Evaluating the Seismic Capacity of Dry-Joint Masonry Arch Structures via the Combined Finite-Discrete Element Method

The behaviour of dry-joint masonry arch structures is highly nonlinear and discontinuous since they are composed of individual discrete blocks. These structures are vulnerable to seismic excitations. It is difficult for traditional methods like the standard finite element method (FEM) to simulate masonry failure due to their intrinsic limitations. An advanced computational approach, i.e., the combined finite-discrete element method (FDEM), was employed in this study to examine the first-order seismic capacity of masonry arches and buttressed arches with different shapes subjected to gravity and constant horizontal acceleration. Within the framework of the FDEM, masonry blocks are discretised into discrete elements. A finite element formulation is implemented into each discrete element, providing accurate predictions of the deformation of each block and contact interactions between blocks. Numerical examples are presented and validated with results from the existing literature, demonstrating that the FDEM is capable of capturing the seismic capacities and hinge locations of masonry arch structures. Further simulations on geometric parameters and friction coefficient of masonry buttressed arches were conducted, and their influences on the seismic capacities are revealed.

Flexural behaviors of CFRP strengthened laminated bamboo arches

Arch structure is a special type of structure, mainly used in bridges, underground buildings and some large public buildings like stadiums. Previous studies have shown that bamboo composite arches are prone to interfacial failure under flexural loading, so that composite materials are considered to be used to reinforce the bamboo laminate. Three different Carbon fiber reinforced plastic (CFRP) reinforcing methods were adopted to strengthen the Laminated bamboo arch (LBA), and three-point bending experiments were conducted to compare the flexural mechanical property of the LBA before and after strengthening. The failure of the LBA is mainly induced by the interfacial delamination. Wrapping CFRP sheets around the LBA can restrain the interlaminar delamination and improve the load carrying capacity of the LBA. In this research, the peak load can be improved by 26.54%. It is also found that the wrapping at the vault is the most important while the wrapping at the haunt has less important effect to improve the load carrying capacity. With CFRP wrapping the utilization ratio of the fiber tensile strength can reaches 0.85, or even close to 1.0.