Structural Design Configurations Research Articles

Effects of Sweep on the Flutter of Wraparound Fins

In the field of missile and rocket design, efficiency is a crucial aspect considering factors such as weight, storage, stealth, and cost. Wraparound fins (WAFs) have been used for many years to control the trajectory of missiles and rockets because of their compactness and effectiveness. However, WAFs are structurally more flexible than other types of fins, which may negatively impact their dynamic behavior and aeroelastic response. This can cause catastrophic instabilities, such as flutter. To mitigate these challenges, it is essential to consider both aerodynamic and structural models of WAFs during the design process. In this study, the flutter velocity and frequency of WAFs were investigated in relation to different structural design configurations and sweep angles, in order to understand and improve the aeroelastic performance of swept WAFs.

A Review on Construction Approach on Preliminary Stage at Best Location

Abstract: The construction of high rise structures in developed and developing countries have been widely used in their urban areas and semi-urban areas. These tall structures include residential apartment, commercial and semi-commercial apartment. Since the provision of these buildings have a larger area of construction, but constructed over less area. In analysis stage of the structure, significant characteristics like vertical load, horizontal load, superstructure design, foundation design takes place. But before that the architecture planning over the larger area has proposed. The selection of area of construction in this preliminary stage has not sufficient on comparing with structural design configurations and soil parameters is an important part should takes place before the planning of the construction area. The paper consists of the study of the past research based on the above title and after that conclusions have drawn based on the inferences of reviews. The result shows that location parameter based on the soil investigation report should be determined first for the usage of best SBC of soil of the selection of construction area. Keywords: Vertical Load, Soil Bearing Capacity (SBC), Tall Buildings, Foundation, Building Design.

Structural robustness quantification through the characterization of disproportionate collapse compared to the initial local failure

Modern design codes recommend ensuring an appropriate level of robustness to prevent disproportionate collapse under an exceptional event. This concept directly refers to the capacity of limiting progressive collapse after an unexpected initial local failure. Assessing a structure in terms of robustness results in a complex issue as it not only requires information on the structural response in a large non-linearity domain, but also as it introduces a high level of uncertainty due to the concept of exceptional initial action. This study proposes a strategy to assess structural robustness using collapse propagation and energy-based indicators. A case study on a demonstrative steel frame building is presented. The first step consists in the definition of the possible scenarios leading to the loss of one or several structural element(s), such as columns. For each scenario, the structural response, including collapse propagation and alternative equilibrium is investigated using a fast computational modelling coupling the yield design theory and a non-linear finite element analysis. Initial to final damage ratios of the structural system and needed energy for initial failure are computed to quantify the robustness of the structure through this scenario-based analysis. A Pareto front analysis of the scenarios is then conducted by solving bi-objective problems that aim to maximize the collapse propagation and minimize the required demand of the initial local failure scenarios. The scenario-based and Pareto front analyses are applied to compare different structural design configurations of a case study used for illustration purpose. Results clearly show how the two levels of analysis give complementary results that allow (i) quantifying and comparing robustness performance of the structure and (ii) identifying critical scenarios.

Review of Aerodynamic Design Configurations for Wind Mitigation in High-Rise Buildings: Two Cases from Amman

This study is concerned with reviewing and analyzing methods used in early design stages to mitigate wind effects on high-rise buildings. In order to mitigate wind effects on structures and specifically high-rise buildings, early stage aerodynamic design decisions are made. Architects try to mitigate the wind effects on buildings by choosing the right form configuration like tapering or setbacks, etc., or by making vital decisions in the early design stage. However, structural engineers utilize the structural system that can best counter-act forces acting on the stability of the building. For both architects and engineers there are many tools which can be used in early design including advanced analysis methods, wind tunnel testing and wind studies combined with Computational Fluid Dynamics (CFD) simulations. This study reviews general architectural and structural design configurations performed in the early phases of the design process, for achieving structural stability, comfort and cost control. The research methodology depends on the study and analysis of different international building examples, and also by reviewing two local high-rise building cases in Amman, Jordan. The study concludes that there are many architectural aerodynamic configurations for the purpose of mitigating wind loads, which can be used as guidelines in the early design phases.

Analysis and application of construction pre-set deformation value of inclined high-rise steel structures

For an inclined high-rise steel structure, for example, the new headquarters of China Central Television (CCTV), if the structural members are manufactured and erected according to the Structural Design Configuration (SDC), it may lead to a considerable deviation between the structural construction completed configuration and the SDC because of its continuously inclined deformation during the installation. And surely it is impossible to connect the cantilever accurately without taking Pre-set Deformation Value (PDV) for structural members during the erection. This paper introduced the concept of the PDV, which includes manufacture pre-set deformation value and erection pre-set deformation value. A new computational method, namely two stage comprehensive iteration method, to determine PDVs of the new CCTV headquarters is proposed. A number of numerical results are obtained which have been used as guidelines for the construction of the new CCTV headquarters.

A multi-objective systems reliability approach for infrastructure design under aleatory and epistemic uncertainty

Robust structural design requires joint consideration of both aleatory (random) and epistemic (lack of knowledge) uncertainty. In a multi-objective decision-making context, aleatory uncertainties are associated with uncertainty inherent to the built environment, whereas epistemic uncertainties accrue due to imperfect representation of decision maker values. This paper presents a systematic decision framework for combining treatment of these types of uncertainties using the First Order Reliability Method (FORM). Probabilistic descriptions of the performance of various alternative structural design configurations are combined with decision maker defined utility functions (indifference curves) that are subjected to epistemic uncertainty, supporting assessment of the sensitivity of the decision analysis results to various sources of error. The proposed decision analysis model allows full and consistent representation of all relevant uncertainties, multiple decision maker utilities, alternative design configurations, and alternative decision criteria. A demonstration identifies the optimal of 12 alternative configurations of a nine-story office building with the decision variables of building damage and business interruption cost, casualty cost, and CO2 emission cost under aleatory and epistemic uncertainties.

Vertical earthquake vulnerability of long-span spherical lattice shells with low rise-span ratios

This paper presents an approach for quickly predicting vulnerable areas of long-span spherical lattice shells under vertical earthquakes using the equivalent continuum analogy. According to the moment theory from classical shell mechanics, the equations for locating the position of maximum nodal displacement are deduced in the elastic range, while considering the heterogeneity in equivalent stiffness. Based on the plastic limit analysis theory, a defined relative stiffness index is proposed by integrating the curvature variation over the corresponding node-bearing area to predict the position of maximum nodal displacement in the plastic range. Several spherical single-layer lattice shells are analyzed using the finite element method to verify the proposed method, and the relative stiffness index, which could be used as an indicator to validate and adjust structural design configurations. As a large-span shell is expected to perform better when each ring has a similar equivalent stiffness index, thereby avoiding abrupt changes in stiffness. The case study indicates that the vulnerable area in such a long-span single-layer lattice shell can be predicted and controlled based on the relative stiffness index values. Additionally, the desired seismic damage-endurance capacity can be obtained by adjusting the relative stiffness index of each ring to ensure that the structure is sufficiently resilient. The method for predicting displacement-based vulnerable areas using the equivalent continuum analogy provides a practical tool for a quick assessment of preliminary design schemes of new lattice shells and can be also applicable to existing and ready-for-retrofit lattice shells.

Structural feasibility of incorporating the LVEM-isolated floor in the first story of a two-story steel frame

We introduce a novel floor-isolation system for mitigating the seismic responses of steel frames. In the system, the floors are connected to steel beams by the laminated visco-elastic material (LVEM). In this paper, we present the feasibility of installing the LVEM-isolated floors in the first story of a two-story steel moment-resisting frame. Firstly, we notice that the floor-isolation decouples the composite behavior between the floors and the beams, thus weakens the stiffness of the beams. Based on a generalized frame model, it is demonstrated that such a reduction in beam stiffness only yields a tiny decrease in the global lateral stiffness of the frame. Subsequently, the dynamic analysis model is established for the frame equipped with the LVEM-isolated floor. The LVEM isolators are simulated by a refined Kelvin-Voigt model, while the entire structure is modeled by a three-degree-of-freedom system. The accuracy of the numerical approach is validated by shaking table tests. Based on the established model, a large-scale numerical computation is conducted using 136 earthquake records. The results demonstrate that the structural displacement responses could be remarkably mitigated by the floor-isolation. In general, the reduction of the peak inter-story drift gets more pronounced when a larger mass-isolation ratio and a softer LVEM isolator are applied. For a regular structural design configuration (e.g., mass-isolation ration ν = 0.7, LVEM isolator stiffness ratio κ = 0.2), a 40% reduction in the peak inter-story drifts could be obtained via the floor-isolation. The ambient temperature notably affects the performance of the floor-isolation system. In many cases, a risen temperature amplifies the benefits of the floor-isolation while a fallen temperature abates such benefits. Meanwhile, the floor-isolation alters the form and the amplitude of the floor acceleration response spectrum (FARS). The peaks of the FARS are significantly mitigated by the LVEM-isolated floors. Quantitatively speaking, we could get a 50% reduction in the peak of FARS from the LVEM-isolated floor system for regular design configurations, say, ν = 0.7, and κ = 0.2.

GPR applications in structural detailing of a major tunnel using different frequency antenna systems

This paper reports an extended study on the applications of ground penetrating radar (GPR) on the structural detailing of a major tunnel located under the River Medway in north Kent, United Kingdom (the Medway Tunnel). Construction of the tunnel was completed in 1996 and it carries a substantial volume of traffic between two major areas of Medway in the south-east of England. The construction of the tunnel is an “immersed tube” tunnel type that connects a number of segments at immersion joint points. This investigation reports the utilisation of two sets of antenna systems with different frequencies (900MHz and 2GHz GPR) in establishing structural details of the tunnel roof at immersion joints. The processed data compiled as a result of this investigation provided essential information to tunnel engineers for forthcoming maintenance planning purposes. The data also provided ample information confirming rather doubted construction design drawings/plans originally produced. The results obtained were conclusive in terms of construction materials and structural design configurations (shape and dimensions) as well as the identification of rebar positions at all three immersion joint locations. A comparison between the different frequency antenna sets provided invaluable information in confirming the above findings. This paper also provides useful information within the context of survey planning and site procedure in a complex operation in terms of adaptation of the GPR systems used.

Analysis of cylindrical sandwich structures with weak orthotropic core under patch loading

An analysis of cylindrical sandwich structures with weak orthotropic core subjected to patch loading is presented. A high order theory model combined with a novel formulation technique is used to predict the static response of the structure. The face-sheets are considered as thin shells that follow the first order shear deformation theory, whereas the core is considered as a linear elastic medium. The effects of core elastic and shear stiffness, curvature to length ratio, and stacking sequence and orientation on the core’s stresses and displacements are presented. The case of a moving load is explored and performance charts are generated to design and optimize the structure in response to the patch loads. In particular, considering an orthotropic core with quasi-isotropic lay-up in the face-sheets, limit the variation of the transverse core shear stress and provide an efficient structural design configuration.

Structural Design of Production Risers and Offshore Production Terminals

Offshore production terminals and deepwater risers are seeing increasing use by the offshore oil industry. The structural design of these units presents a unique challenge compared to other offshore systems. Development of design loading conditions and fatigue histories is especially interesting due to the complex interaction of nonlinear riser and vessel dynamics, the statistical nature of maximum loads and the need to consider directionality as well as the magnitude of environmental loading. This paper presents a complete procedure for predicting design loads and fatigue histories for production risers and offshore terminals. The emphasis will be on systems wherein a dedicated vessel is connected to the riser by a rigid mooring arm. A number of structural design configurations will be surveyed. Techniques for preliminary sizing, dynamic analysis, model testing and fatigue analysis will be discussed. The application of this procedure to several specific design cases will be summarized.

Damping Structural Resonances Using Viscoelastic Shear-Damping Mechanisms: Part II—Experimental Results

This paper describes the experimental dynamic response characteristics of structural design configurations employing viscoelastic shear-damping mechanisms that have been discussed in a previous paper. Experimental results are given for cantilever beams fabricated from viscoelastic-damped sheet and structural shape members; results are also given for cantilever beams damped by use of the strip damper (an additive damping technique). The effects of shock excitation, steady-state vibration excitation, vibration excitation level, structure resonant frequency, and environmental temperature on the damping properties of the structural design configurations are demonstrated. The effects of structural damping on the performance of vibration isolation systems are determined and the significance of employing highly damped structural designs in fabrications intended for use in modern dynamic environments is discussed.