Maximum Allowable Deflection Research Articles

Structural Architectures for Imperfect Deployable Lunar Towers

The load-carrying performance for deployable lunar tower architectures using thin-ply composite booms is parametrically evaluated. These towers support a communications and sensor platform on the lunar surface. The primary design consists of the corrugated rollable tubular boom (COROTUB) acting as the primary tower mast that supports the payload tip mass. Guy wires connecting the boom tip to spreader bars attached at the base serve to correct lateral eccentricities and increase dimensional accuracy. The analysis compares the maximum tip mass that this primary design can carry relative to a reference design that does not contain any guy wires or spreader bars. The results provide insights into whether the additional system mass and complexity associated with the cable-stayed design are worth the increased payload mass that can be supported. By setting the design limiting condition to a maximum allowable deflection, the analysis reveals that the primary design has better performance when the spreader bar length relative to the tower height exceeds a critical value. The analysis is extended to lunar towers with collapsible tubular mast (CTM) booms, and similar trends are observed. Finally, the analytical load displacement behavior of the COROTUB and CTM reference towers is verified with finite element simulations.

Numerical simulation study on rubber ring for pipe jacking joint of electric power tunnels

Abstract To study the sealing properties and stress characteristics of the rubber ring in pipe jacking tunnel joints, the critical state value when the waterproof failure occurs is calculated using the expression of joint detail dimensions. The pipe joint installation finite element model is executed by ABAQUS software to optimize the rubber ring structure. Meanwhile, the pipe joint deflection angle and the installation gap are adjusted. The results indicate that the contact pressure and joint installation force of rubber rings significantly decreased. Moreover, the contact pressure exceeds 0.3 MPa, demonstrating that the optimized joint is more reasonable and reliable. When the pipe section deflects, the maximum allowable deflection angle is 0.02 rad. Exceeding this limit will result in leakage damage due to insufficient contact pressure. The installation gap has a significant impact on the stress of the rubber ring. With an installation gap between 7 and 13 mm, joint failure can be effectively prevented.

PENGARUH SERAT BAMBU TERHADAP KAPASITAS LENTUR PELAT BETON CAMPURAN STYROFOAM DEGAN PERKUATAN TULANGAN WIREMESH

Lightweight concrete is a concrete technology innovation that is currently developing. The advantage of lightweight concrete is that it uses less time and costs compared to concrete in general but has the disadvantage of lower strength. This research aims to determine the effect of adding bamboo fiber on the flexural capacity of lightweight concrete slabs mixed with Styrofoam. The lightweight concrete mixture used is Styrofoam at 50% of the weight of the mixed aggregate. Variations in adding bamboo fiber with a diameter of 1 mm and a length of 40 mm are 0% and 0.5% of the cement weight. The test object consists of a lightweight concrete plate measuring 50 cm x 150 cm x 8 cm with wire mesh reinforcement with a diameter of 8 mm. Tests were carried out when the concrete was 28 days old by applying an even load gradually until the slab collapsed. From the test results, at a loading of 300 kg, the average deflection value for lightweight concrete slabs with reinforcement reinforcement with 0% bamboo fiber was 1.18 mm and for lightweight concrete slabs with 0.5% bamboo fiber was 1.57 mm. Lightweight concrete slabs mixed with bamboo fiber have a greater deflection than lightweight concrete slabs without a mix of bamboo fiber. This shows that the addition of bamboo fiber to lightweight concrete slabs does not increase the flexural capacity of the slab. The difference between theoretical calculations and testing is due to the theoretical calculation formula used in this research not taking into account the content and properties of Styrofoam in the plates. The two variations of concrete slabs used in the test did not experience any cracks and met the maximum allowable deflection requirements at loads reaching 300 kg.

STUDY OF THE STRESS-STRAIN STATE OF A REINFORCED CONCRETE SLAB USING HYDROSTATIC METHOD

The scientific article is devoted to a complex study of the stress-strain state of a monolithic slab, implemented using the author’s method of hydrostatic loading, which involves setting the load by the weight of water and regulating its value by the height of the water column. To implement the given procedure, we used a tank-shaped facility for field tests of structures for vertical short-term and long-term loads. To determine the deflections of the loaded slab system, we installed mechanical deflection gauges of the 6PAO brand under the slab at pre-planned places. The short-term loading of the selected section of the monolithic reinforced concrete slab involved three stages. The first two stages of loading were carried out step by step, with a load step of 1–2 kN/m2 and a time delay until the arrows of the deflection gauges stopped. The maximum load on the slab was 5 kN/m2. The maximum deflection was recorded for point 2 (conventional centre of the tank) and was equal to 1.27 mm. The third stage of slab loading proceeded by analogy with the previous two. The maximum load on the slab was 8 kN/m2. The maximum deflection was recorded for point 2 and equalled 1.57 mm. After completing the stepped loading, the water tank was left on the slab to track vertical deflections for 32 days. The study experimentally established that the displacement of the examined slab in the span and support zones under increased load did not exceed the normative values. We carried out numerical verification using finite-element modelling followed by calculations in a linear and non-linear model. The theoretical and experimental calculation results showed a qualitative and quantitative data match (the difference did not exceed 15–20%). The nature of the change in the deflections remained practically linear and closely correlated with the experimental data (the values of the maximum deflections were equal to 1.16 and 1.57 mm, respectively, which was less than the maximum allowable deflection of 30 mm). Based on the results of the comprehensive study, we have made proposals for further safe operation of the investigated slab system through the use of lightweight floor elements (lighter filling, reduction of screed thickness, and others) to limit the total load on the overlapping to 10 kN/m2 (taking into account dead weight of the slab, load from floor structure and partitions, load from people and various types of construction and other equipment). Keywords: hydrostatic loading, testing, concrete, calculation, deflection, modelling.

Design optimization of additively manufactured sandwich beams through experimentation, machine learning, and imperialist competitive algorithm

The primary aim of this study was to optimize 3D-printed sandwich beams incorporating auxetic cores. Four key design variables were considered: core thickness, width, and two specific geometric parameters related to the auxetic core–the cell's wall thickness-to-length ratio and the cell angle. Initially, sixteen sandwich samples, each varying in geometric parameters, were printed following Taguchi's experimental design. These samples underwent a three-point bending test, and the resulting data were used to train a deep neural network (DNN). The trained DNN proficiently predicted the bending response of the structures. Another network, using a similar architecture, was trained to precisely predict the structure's mass. These trained networks were then integrated into the imperialist competitive algorithm (ICA) to optimize the sandwich beams design for minimal mass. A contour plot was subsequently generated to visually illustrate the minimum required mass distribution for sandwich beams under various conditions and constraints, considering applied bending forces and maximum allowable deflection. The optimization results underscored the importance of fabricating and testing an adequate number of sandwich samples, aligning with the number of design parameters. The results provide a valuable reference for future research on designing advanced 3D-printed lightweight structures, including integrating machine learning techniques and metaheuristic algorithms.

DEFLECTION ANALYSIS OF THE BUILDING STRUCTURE USING BUILDING INFORMATION MODELING

The National Research and Innovation Agency (BRIN) is currently carrying out the construction of research facilities in various regions in Indonesia, one of which is the construction of the Green House Display Facility Infrastructure located in the Cibinong Science Center and Botanical Garden (CSC-BG-LIPI) area. This study aims to model the structural elements of the BRIN Cibinong Bogor Green House Display building and conduct structural analysis of columns (K10, K11, K12) and beams (B3, B4, B10, B13, BP1, BP2) using Tekla Structures 21 and Tekla Structural. Designer 21. The result of this research is that the modeling of structural elements can be done well and in detail, for example, there are no structural components that have clashes. The largest maximum deflection occurs in beam B4 which is 0.004921 m. Based on the deflection calculation in article 24.2 of SNI 2847:2019, the maximum permit deflection value is 0.0125 m. This shows that all beams and columns analyzed meet the maximum allowable deflection requirements based on SNI 1726:2019 and SNI 2847:2019

Nonlinear Seismic Analysis of Perforated cold-formed steel shear wall with Upright Section

During the last few decades, cold-formed steel (CFS) is extensively used in mid- and low-rise housing due to the increasing demand of rapid constructions along with its various advantages in comparison with other structural material. Cold-formed steel framed shear walls (CFSFSW) are most common and primary lateral load resisting system. However, adopting it in the seismic zone is difficult, especially because many design components remain open. In this research an effort has been made to design the shear wall system with both unperforated and perforated upright sections using nonlinear static analysis method. In ABAQUS, a general-purpose finite element analysis software, three-dimensional models using shell elements are used to simulate a shear wall system. A comparative study regarding the lateral load capacities with respect to maximum allowable lateral deflection including different parameters like column sections, thickness and perforation arrangements are presented here. It was found that increasing thickness and including Chanel stiffeners improves the lateral strength of original upright section. The developed modelling protocol helps to estimate its lateral performance under earthquake with reasonable accuracy.

Evaluation of excessive wellhead motions: Reliability assessment and wellhead integrity index (Part II)

As discussed in part I of this work, the wellhead is an important component in the context of well integrity and operational safety, as it serves as a link between well and riser in offshore oil wells. The wellhead must sustain loads from the casings (soil reaction), which are hung into it through the casing hangers, as well as sustain loads from the riser (waves, current), which is connected at the top of the BOP (right above the wellhead) through the lower flex joint. In Part I of this work, we proposed a deterministic methodology to evaluate excessive wellhead motions, considering a mechanical system that couples the vessel, the riser, the wellhead itself, the conductor and surface casings, and their interaction with the soil. Now, in Part II, we move onto a stochastic analysis, which allows us to calculate the wellhead reliability. The simulation of this system provides the motions experienced by the wellhead; then, criteria such as maximum allowable lateral deflection and maximum allowable rotation are applied to verify if they will cause wellhead failure. Several interesting results have been observed: modern 5-phase wells with cemented conductor confer higher integrity to the wellhead compared to old 4-phase wells with jetted conductors; current speed/profile is the variable that affects the most the wellhead reliability; and heavier inner fluids reduce the reliability, posing a problem for later drilling phases. Finally, an integrity index for the wellhead throughout the well life cycle is suggested, aggregating the literature related to wellhead fatigue failure. The wellhead integrity index can then be combined with other indexes from other barrier elements to evaluate the overall integrity of barrier envelopes.

Experimental analysis and Study on Shear Performances of Castellated Beam Chassis under Three Cases of Stiffener

Nowadays, Engineers are actively seeking to improve construction materials and properties. In that, the usage of the castellated beam is become very popular due to its advantageous structural applications. In existing researches are described the presence of large openings in the web that creates different mechanical behaviour compared to strong web beams. While it does not deal with the behaviour of the shear strength performances of the castellated beam, which is due to the limitations on maximum allowable deflections by welding stiffeners. Therefore, this research analysis intends on augmentation of shear strength in castellated beam. Hence, the work incorporates shear stiffeners along with the web opening of the web adjacent to the shear region. Consequently, it leads to increase the shear strength of the castellated beam chassis with regard to cyclic loading and also efficiently reduce the deflection. In order to improve the behaviour of the castellated chassis beam, the study investigation providing the diagonal stiffeners on the web opening with the shear zone and thus compared to without stiffeners and vertical stiffeners. At last castellated beam and deflection effects with increased depth of web openings are analysed with the aid of Finite Element Analysis software ANSYS 16.0. From the experimental findings, the paper achieves the maximum deflection of forwarding and reverse cyclic loading is 7.7mm and 7.29mm respectively. This demonstrates the efficacy and the confines of the assorted studies of stiffening solutions.

Analysis and Optimization of Truss Structures, Constrained Handling using Genetic Algorithm

In this study, an attempt is made to minimize the weight of Howe roof and ten member-6 Node trusses, separately. Two constraints, maximum allowable deflection and maximum allowable member stresses have been considered. For the first truss, permissible deflection is not known from the literature; therefore, it is determined using the exhaustive search method. Once magnitudes of the constraints are identified, member cross-sectional areas are varied to get the optimal weight. Both the exhaustive search method and the genetic algorithm have been implemented for this purpose. During the optimization, members tending to form a string may be eliminated from the structure. Doing this, we could further reduce the weights of the trusses and even less than the minimum available in the literature. The second truss is an indeterminate structure, and Maxwell Betti reciprocal theorem is applied to calculate the member forces. Also, further reduction of members is made for this truss, keeping in mind that the truss becomes determinate with the decrease in the member(s).

ACI 318 최대허용처짐에 만족하는 1방향 GFRP-보강근 콘크리트 슬래브의 최소두께

ACI 318 최대허용처짐에 만족하는 1방향 GFRP-보강근 콘크리트 슬래브의 최소두께

Fully coupled modelling technique for blast analysis of cable truss facades

This paper develops and applies a fully coupled fluid–structure interaction technique to analyse the blast response of cable truss facade (CTF). This technique models the explosive source, blast wave propagation and interactive behaviour of blast pressure with the structure and enables to evaluate the effects of load related parameters. Modelling techniques are verified with experimental and numerical results and then used to analyse the blast induced shock wave propagation through air and the response of the CTF. Effects of load related parameters of charge weight, standoff distance and height of explosive from the ground are investigated. Limits on the load related parameters and the maximum allowable cable deflection are identified based on results to enable a safe design of the CTF. The combined effects of charge weight, standoff distance and height from the ground that produce similar failure patterns can be used to present the results in the form of Pressure- Impulse (P-I) diagrams. They are iso-damage curves based on blast pressure and impulse that produce similar damage in the structural component of interest. A damage criterion based on axial load carrying capacity, to initiate the development of P-I diagrams for CTF is proposed. The validated fully coupled modelling techniques presented in this paper provide an important source for generating information in the blast design field and for determining the blast behaviour of CTFs. The results can be used to determine the limits on the load related parameters and the maximum allowable cable deflection to enable safe blast designs of the CTFs.

Effect of Wall Deformation on Dewatering-Induced Ground Surface Settlement

In practice, dewatering for pressure relief is commonly undertaken during ongoing excavation to secure bottom stability against basal upheaval. Simultaneously, through unloading, wall deflection is obviously observed. Noticing that both cause soil deformations, this research is to study the effect of wall deformation on dewatering-induced settlement. A coupled numerical analysis of finite-difference software is employed to model Shanghai soft soils under multi-aquifer-aquitard systems (MAASs) by analyzing the results in association with an empirical approach. Consequently, through gradual force reduction, shear strength at soil-wall interface is significantly diminished. As wall deformation increases instantaneously upon lower loading, wall surface becomes deformedly bending; this condition causes the challenge to workability of shear strength. Moreover, wall deformation caused by unloading affects dewatering-induced settlement substantially. Under smaller loading, large wall deflection is observed; soil plane of failure caused by both sliding and compression occurs along slip curve, with weaker shear-strength soils at rD = 0.4 and stronger shear-strength soils between rD = 0.4 and rD = 0.65, where rD is the distance from the wall that is normalized by the depth measured from ground surface. During dewatering, stronger soils tend to drag weaker soils upward to reduce large differential settlements caused by additional compression. Consequently, settlement becomes larger at rD = 0.4 and smaller at rD = 0.65. Remarkably, at rD > 2.3, both settlement curves that result from numerical analysis and empirical method show overlapping; this indicates that the unloading effect on dewatering-induced settlement at rD > 2.3 is insignificant. Furthermore, as wall reaches maximum allowable wall deflection by 67% applied force, additional compression caused by dewatering after loading remains smaller than that under 70% applied force, contributing to smaller dewatering-induced settlement.

Analytical approach for the design of flexural elements made of reinforced ultra‐high performance concrete

AbstractThe increasing demands of sustainable design and construction with economical sections, reduced cover, and more efficient time schedule require more flexibility in the design methodologies. The development of ultra‐high performance concrete (UHPC) have gained increasing interests as an attractive option for structural members with lightweight and superior performances. Concrete members reinforced with steel bars and fibers, generally known as hybrid reinforced concrete (HRC), offer a feasible solution in terms of reducing reinforcing materials and achieving desired structural performance. This paper proposes an analytical model to predict the flexural behavior of hybrid reinforced UHPC with steel reinforcements. Moment–curvature solutions are derived for reinforced sections based on parameterized tension‐compression constitutive models. The approach is applicable to customized cross section and derivation of T‐section is demonstrated. The moment–curvature response is further simplified as a tri‐linear model, which is used for the development of full‐range displacement solutions in analytical form. The proposed model is validated with the experimental data from literature covering a range of materials and member sizes. The full‐range solutions may provide insights into the serviceability design approach based on the criterion of maximum crack width or allowable deflection.

ОСОБЕННОСТИ ДЕФОРМАЦИИ ЖЕЛОБЧАТОЙ КОНВЕЙЕРНОЙ ЛЕНТЫ ПРИ МАЛЫХ НАТЯЖЕНИЯХ

The article presents analytical dependences for the maximum permissible bending radius of the conveyor belt in the longitudinal direction, in which the shape of the gutter is lost in areas with low tension, depending on the design and physical and mechanical properties of the belt. The results of calculations based on these dependencies for a number of modern rubber-fabric and rubber-rope belts are presented. The results obtained can be applied to determine the minimum allowable belt tension and the maximum allowable belt deflection, which usually occur in the loading zone of the conveyor and are the starting value when constructing a tension diagram in the process of traction calculation of the conveyor. They are also useful for determining the parameters of transition sections of conveyor belts.

Rigorous uncertainty quantification and design with uncertain material models

We assess a method of quantification of margins and uncertainties (QMU) in applications where the main source of uncertainty is an imperfect knowledge or characterization of the material behavior. The aim of QMU is to determine adequate design margins given quantified uncertainties and a desired level of confidence in the design. We quantify uncertainties through rigorous probability bounds computed by exercising an existing deterministic code in order to sample the mean response and identify worst-case combinations of parameters. The resulting methodology is non-intrusive and can be wrapped around existing solvers. The use of rigorous probability bounds ensures that the resulting designs are conservative to within a desired level of confidence. We assess the QMU framework by means of an application concerned with sub-ballistic impact of AZ31B Mg alloy plates. We assume the design specification to be a maximum allowable backface deflection of the plate. As a simple scenario, we specifically assume that, under the conditions of interest, the plate is well-characterized by the Johnson-Cook model, but the parameters of the model are uncertain. In calculations, we use the commercial finite-element package LS-Dyna and DAKOTA Version 6.7. The assessment demonstrates the feasibility of the approach and how it results in high-confidence designs that are well-within the practical range of engineering application.

Scaling laws of compliant elements for high energy storage capacity in robotics

The key component in compliant actuators is the elastic element, typically a spring. Nevertheless, different types of springs have different characteristics in terms of size, weight, maximum allowable force, maximum allowable torque and maximum allowable deflection. It is however very important to compare them on these requirements, since each application has other demands. In this paper, the energy storage capacity of different types of compliant elements are calculated using scaling laws in order to easily derive the maximum achievable energy capacity for a certain arrangement. These scaling laws are given as a function of the structural parameters and are validated with catalog data of spring manufacturers and distributors such as Alcomex, Lesjöfors and Century Spring. As such, different types of compliant elements can be compared in an easy way. To fully exploit the capabilities of compliant elements, these scaling laws are used to verify the effect of spring parallelization on mass and/or enclosed volume, which is interesting regarding redundant compliant actuation. From theoretical calculations and a case study, it follows that parallelization is beneficial, especially for mass reduction.

The Audit and Assessment of Building Structural Strength (Case Study of Mataram Islamic State University Rectorate Building)

Rectorate building of Mataram Islamic State University was designed of four story building and startedunder construction on 2008. However, the construction was aborted due to lack of administrationmanagement and left the building under incomplete condition with only foundation and the first floorerected. Ten years afterward, the management decided to continue construct the building. This studyaimed to investigate the condition of existing building whether can be rebuilt properly corresponding tothe previous design. The investigation included structural cracks that happened on structural element aswell as the deflection of structural beams. The conditions of existing structural column have also beeninvestigated.The assessment process was conducted both on field and laboratory testing. The field testing was run withSchmidt Rebound Hammer test to know the compressive strength of structural concrete and its quality.The waterpass, theodolite, and tape measurement were used to measure the building geometric. SAP2000 computer package was used to analyze the structure. Loading test was carried out base on the totalmeasurement test which was required in SNI 03-2847-2002. The total measurement load of 700 kg/m2was employed representing U = 85% (1,4D + 1,7L), where D was dead load and L was live load. In thisstudy, the loading test was conducted on 300/700 and 200/500 size beams.Test result indicated that the qualities and the concrete compressive strengths on the buildingconstruction elements were varied. Steel reinforcement of structural columns was good enough towithstand the load, but, the column concrete strength should be improved. On the beam of 300/700 in thefirst floor, the deflection did not exceed the maximum deflection based on the code. However, themaximum deflection on 200/500 beam was 6.92 mm > 5.85 mm (maximum allowable deflection) andpermanent deflection after loading of 2.31 mm > 1.46 mm (maximum allowable permanent deflection).Therefore, rehabilitation and retrofitting of structural columns and 200/500 mm beam are essential.

A hybrid algorithm coupling genetic programming and Nelder–Mead for topology and size optimization of trusses with static and dynamic constraints

Truss optimization aims to provide the lightest truss to gain the maximum benefit out of available resources. Truss optimization may subject to static and dynamic constraints. Static constraints include structural kinematic stability, maximum allowable stress in truss members, maximum allowable deflection in the truss nodes and critical buckling load. However, dynamic constraints impose limits on the natural frequency of the desired truss to avoid the destructive resonance phenomenon. Taking both static and dynamic constraints into account may lead to growth in the search space but dwindling its feasible region; the search space becomes very non-convex and may subterfuge the solver to trap in a local optimum. Another design consideration may include fabricational constraints to present design variables from a set of available cross-sections to satisfy the design codes. This paper proposes a hybrid genetic programming algorithm to deal with the barriers of this complex problem. It looks for the optimum connectivity table (among the truss nodes) and optimal cross-sectional areas for its members subject to design constraints. It also benefits from a Nelder–Mead local search operator to improve the competence and true convergence of the algorithm. Our algorithm has been applied to some numerical examples considering both types of continuous and discrete design variables; It proved its efficiency to find better solutions (lighter trusses) in comparison with other methods in the literature for most of the cases.

Sizing and topology optimization of truss structures using genetic programming

This paper presents a genetic programming approach for simultaneous optimization of sizing and topology of truss structures. It aims to find the optimal cross-sectional areas and connectivities of the joints to achieve minimum weight in the search space. The structural optimization problem is subjected to kinematic stability, maximum allowable stress and deflection. This approach uses the variable-length representation of potential solutions in the shape of computer programs and evolves to the optimum solution. This method has the capability to identify redundant truss elements and joints in the design space. The obtained results are compared with existing popular and competent techniques in literature and its competence as a tool in the optimization problem are demonstrated in solving some benchmark examples, the proposed approach provided lighter truss structures than the available solutions reported in the literature.