Design Guidelines For Structures Research Articles

Tsunami Effects on Buildings and Coastal Structures

In 2011, the Heisei Tsunami (also known as the East Japan Tsunami) caused unprecedented damage to well-engineered buildings and coastal structures. We examine two reinforced concrete buildings that were exposed to similar tsunami loadings, but one collapsed and the other did not. It is shown that the contrast is partly resulted from the presence of a building foundation that could cause a time delay and attenuation of the buoyancy effect on the buildings. The surviving building must be stabilized by the weight of water that flooded the building interior. We also investigate failure patterns of concrete seawalls and coastal dykes. It is demonstrated that flow-induced suction pressures on the crown play a role in the failure of concrete panels that covered the dyke’s infill. High-speed flows together with high compressing pressures can cause the formation of a scour at the leeside foot of the dyke. Considerations for the design guidelines for buildings and coastal structures to cope with the “beyond-the-design-basis” extreme coastal hazards are proposed.

Editorial: Optogenetic Tools in the Molecular Spotlight.

Editorial: Optogenetic Tools in the Molecular Spotlight.

Crushing analysis of splitting–bending steel plate energy absorber under axial loading

The splitting and bending behaviour of steel plates was used as energy absorber in our previous work. Two experiments with 9mm steel plates were carried out. The finite element models presented in this study are based on experimental tests and good agreement is achieved between the experimental and finite element results. Through the observation of the results of numerical simulation, the typical deformation process and variations of the stress triaxiality of the elements are presented. The parametric study was performed using finite element models under quasi-static loading conditions. It was found that the plate thickness, die angle, width of the die and the distance between the steel plate and the baffle have a distinct effect on the energy absorption. The outcome of this parametric study was full and detailed design guidelines for such energy-absorbing structures. The effect of the velocity was investigated and the result shows that under dynamic loading the deformation of the steel plates is similar to the quasi-static loading, and the steady state force increased as the impact velocity increased. With a bigger angle, the increase of the steady state force is larger.

Flexural Bond Behavior of Rebar in Ultra-High Performance Concrete Beams Considering Lap-Splice Length and Cover Depth

This study intends to find out the correlation between the cover depth and the bond characteristics of UHPC through pull-out tests of UHPC specimens with different cover depths and bond tests of rebar using flexural members. In this experimental study, specimens are fabricated with the lap-splice length as test variable in relation with the calculation of the lap-splice length for 180- MPa UHPC. Moreover, specimens are also fabricated with the cover depth as test variable to evaluate the effect of the cover depth on the UHPC flexural members. The load-displacement curves are analyzed for each of these test variables to compute the lap-splice length proposed in the K-UHPC structural design guideline and to evaluate the influence of the cover depth on the flexural members. As a result, the stability of the structural behavior can be significantly enhanced by increasing slightly the cover depth specification of the current UHPC Structure Design Guideline from the maximum value between 1.5 times of rebar diameter and 20 mm to the maximum value between 1.5 times of rebar diameter and 25 mm.

低炭素型セメント結合材を用いたコンクリート構造物の設計・施工ガイドライン（案）

低炭素型セメント結合材を用いたコンクリート構造物の設計・施工ガイドライン（案）

熱応力を受ける多層膜コーティングのき裂発生条件の理論的予測と検証

Reliability of environmental barrier coatings for ceramics (EBC) is essential for improving performance of high-pressure turbine materials for aircraft engines. The aim of this study is to prescribe theoretical guidelines for structural design of EBC with better mechanical reliability. We propose a simple theoretical method to predict the condition of interface crack initiation in multi-layered EBC coatings (ceramics/Si-based bond coat/Mullite/Yb-silicate) due to thermal stress in fabrication processes. The method is validated by comparing energy release rates between finite element method analysis and the proposed method. The results reveal that the condition of Si-based bond coat/ceramics interface crack initiation can be estimated by the method introducing factors independent of the thickness of layers. On the other hand, the conditions of crack initiation at Mullite/Si-based bond coat and Yb-silicate/Mullite interfaces are dependent on the thickness of the Si-based bond coat.

Quasi-static, impact and energy absorption of internally nested tubes subjected to lateral loading

This paper presents the responses of nested tube systems under quasi-static and dynamic lateral loading. Nested systems in the form of short internally stacked tubes were proposed as energy absorbing structures for applications that have limited crush zones. Three configurations of nested tube systems were experimentally analysed in this paper. The crush behaviour and energy absorbing responses of these systems under various loading conditions were presented and discussed. It was found that the quasi-static and dynamic responses of the nested systems were comparable under an experimental velocity of v=4.5m/sec. This is due to insignificant strain rate and inertia effects of the nested systems under the applied velocity.The performance indicators, which describe the effectiveness of energy absorbing systems, were calculated to compare the various nested systems and the best system was identified.Furthermore, the effects of geometrical and loading parameters on the responses of the best nested tube system were explored via performing parametric analysis.The parametric study was performed using validated finite element models. The outcome of this parametric study was full detailed design guidelines for such nested tube energy absorbing structures.

Resistance analysis and device design guideline for graphene RF transistors

Graphene has attracted enormous attention in recent years because of its high carrier mobility and saturation velocity. High-performance graphene transistors for radio-frequency (RF) applications are especially attractive. Synthesis of high quality graphene sheets and application of various materials for gate dielectrics and substrates have been demonstrated. However, very few studies have been performed on the effects of graphene transistor parameters, such as parasitic resistances and graphene quality, in relation to RF applications. Here we report a systematic study of those effects on electrical performance depending on the transistor structure. It is found that the access resistance and contact resistance are the dominant factors leading to degradation of the device performance, especially in deep scaled devices. A guideline for device structural parameter design for required RF performance is discussed. Furthermore, we demonstrate that the newly proposed self-aligned structure can minimize access resistance component, resulting in 6 times higher cut-off frequency compared to that of the conventional structure, when the gate length is 50 nm. The findings of this study can be used to predict the device RF performance and thus help the design of graphene transistor structures to meet specific requirements.

Comparative testing of crack formation in strain-hardening cement-based composites (SHCC)

Abstract Two of the main activities of RILEM Technical Committee 208-HFC Subcommittee 2 were the preparation and publication of the state-of-the-art report on durability of strain hardening cement-based composites (SHCC), and the performance of comparative laboratory testing on SHCC. In this paper the comparative mechanical tests are reported, as performed in laboratories of five participating institutions. The purpose was to investigate and compare the crack patterns in terms of crack widths and spacing, and subsequently to make recommendations for a suitable test setup and procedure towards characterizing cracking in this class of materials. Such standardized procedures are required for future systematic and objective research towards durability of these materials in their in-service conditions, i.e. their resistance to deterioration processes in the cracked state. Standardized test procedures are also required for durability testing and guidelines for structural design with SHCC, which is the focus of follow-up committee activity in TC 240-FDS.

Experimental and numerical study on the effect of humidity-temperature cycling on structural multi-material adhesive joints

The following paper describes investigations on the impact of harsh environment on shear and tensile strength of multi-material adhesive joints. The samples were made from carbon fiber – epoxy composites, aluminum and two types of advanced steels: abrasion resistant and high-strength. In order to assess the suitability of structural bonding for this sort of applications, it was decided to test two different epoxy-based adhesives, designed for moderate and elevated operating temperatures. The harmful conditions were simulated by means of humidity-temperature cycling tests, according to the SAE standard. The obtained results revealed that even moderately harsh humidity-temperature loads can cause debonding of the joints, even if no external forces are applied. In order to gain insight into this phenomenon, a series of finite element analyses was performed, simulating the exposure of the samples to the chosen environmental conditions. Based on these studies, the temperature expansion coefficient was identified as the crucial factor for the performance of the joints made from dissimilar materials. The results of the described experiments, confirmed by numerical calculations, constitute a guideline for multi-material structural design, supporting this constantly growing branch of modern engineering with a relevant input.

Analysis of hydroelastic slamming through particle image velocimetry

Predicting the hydrodynamic loading experienced by lightweight structures during water impact is central to the design of marine vessels and aircraft. Here, hydroelastic effects of flexible panels during water entry are studied through particle image velocimetry. Experiments are conducted on a compliant wedge entering the water surface in free fall for varying entry velocities, and the pressure field is indirectly evaluated from particle image velocimetry. Results show that the impact is responsible for prominent multimodal vibrations of the wedge, and, vice versa, that the wedge flexibility strongly influences the hydrodynamic loading. With respect to rigid wedges, the hydrodynamic loading exhibits marked spatial variations, which control the location of the minimum and maximum pressure on the wetted surface, and temporal oscillations, which modulate the direction of the hydrodynamic force. These experimental results are expected to aid in refining computational schemes for the analysis of hydroelastic phenomena and provide guidelines for structural design.

Elastic Buckling Behaviour of General Multi-Layered Graphene Sheets

Elastic buckling behaviour of multi-layered graphene sheets is rigorously investigated. Van der Waals forces are modelled, to a first order approximation, as linear physical springs which connect the nodes between the layers. Critical buckling loads and their associated modes are established and analyzed under different boundary conditions, aspect ratios and compressive loading ratios in the case of graphene sheets compressed in two perpendicular directions. Various practically possible loading configurations are examined and their effect on buckling characteristics is assessed. To model more accurately the buckling behaviour of multi-layered graphene sheets, a physically more representative and realistic mixed boundary support concept is proposed and applied. For the fundamental buckling mode under mixed boundary support, the layers with different boundary supports deform similarly but non-identically, leading to resultant van der Waals bonding forces between the layers which in turn affect critical buckling load. Results are compared with existing known solutions to illustrate the excellent numerical accuracy of the proposed modelling approach. The buckling characteristics of graphene sheets presented in this paper form a comprehensive and wholesome study which can be used as potential structural design guideline when graphene sheets are employed for nano-scale sensing and actuation applications such as nano-electro-mechanical systems.

Design guidelines for laser additive manufacturing of lightweight structures in TiAl6V4

Today, laser additive manufacturing (LAM) is used in more and more industrial applications. Due to a new freedom in design it offers a high potential for weight saving in lightweight applications, e.g., in the aerospace industry. However, most design engineers are used to design parts for conventional manufacturing methods, such as milling and casting, and often only have limited experience in designing products for additive manufacturing. The absence of comprehensive design guidelines is therefore limiting the further usage and distribution of LAM. In this paper, experimental investigations on the influence of part position and orientation on the dimension accuracy and surface quality are presented. Typical basic shapes used in lightweight design have been identified and built in LAM. Thin walls, bars, and bore holes with varying diameters were built in different orientations to determine the process limits. From the results of the experiments, comprehensive design guidelines for lightweight structures were derived in a catalog according to DIN 2222 and are presented in detail. For each structure a favorable and an unfavorable example is shown, the underlying process restrictions are mentioned and further recommendations are given.

Stress analysis in contact zone between the segments of telescopic booms of hydraulic truck cranes

This paper presents the analysis of local stress increases at the contact zone between the inner and outer segments of telescopic booms of truck cranes. A portion with a relevant length was singled out of the outer segment and a mathematical model was created describing its stress–strain state as a function of geometrical parameters. The obtained results were verified by the finite element method as well as by experimental testing of the truck crane TD-6/8. Comparison of results revealed high compliance between the analytical model and the results obtained by the finite element method and experimental testing, which confirmed all the hypotheses. The presented methodology as well as the verified analytical expressions give guidelines for optimum design of box-like telescopic segments and other structures with local stress increase in contact zone.

The single perturbation load approach applied to imperfection sensitive conical composite structures

The importance of taking into account geometric imperfections for cylindrical and conical thin-walled structures prone to buckling had been already recognized by the first authors dealing with new formulations. Nowadays, the analysts still use empirically based lower-bound methods such as the NASA SP-8007 guideline to calculate the required knock-down factors (KDFs), which does include important mechanical properties of laminated composite materials, such as the stacking sequence. New design approaches that allow taking full advantage of composite materials are required.The single perturbation load approach (SPLA), a new deterministic approach first proposed by Hühne, will be investigated with unstiffened composite conical structures varying the geometry, lamina and layup. The SPLA׳s capability for predicting KDF is compared with the NASA approach. The SPLA was applied to the geometrically perfect structures and to the structure with geometric imperfections of two types, mid-surface imperfections and thickness imperfections. The study contributes to the European Union (EU) project DESICOS, whose aim is to develop less conservative design guidelines for imperfection sensitive thin-walled structures.

고무차륜형 경전철 고가구조물 설계기준에 관한 현장 계측 시험 연구(1): 제동하중

국내에 건설 운영 중인 경전철 고가구조물은 설계 당시 경전철 고가구조물 설계기준이 마련되어 있지 않아 일반 철도교 설계기준 및 국외 차량제작사에서 제시한 설계기준을 참조하여 설계된 관계로, 고가구조물이 과다 설계되어 비경제적으로 건설된 주된 이유가 되고 있다. 본 연구에서는 고무차륜형 경량전철이 고가구조물 위를 각각 50km/h, 60km/h, 70km/h의 속도로 주행 중 5개 제동 지점별로 제동 시 고가 하부구조물에 작용하는 제동하중을 현장 계측시험을 통해 분석하였고, 현재 설계시 반영되고 있는 철도설계기준과 비교하였다. 본 연구에서 제시된 제동하중 시험분석 결과는 향후 경전철 고가구조물 설계기준 제정 시 참조될 수 있다. Due to the absence of design guidelines for elevated light-rail structures in Korea, most elevated light-rail structures have been designed and constructed based on the design codes of conventional railway bridges and on the codes recommended by foreign vehicle manufacturers. This is the main reason why most elevated light-rail structures are massive or over-designed or poorly constructed economically. In this paper, the authors carried out field tests to analyze the braking forces caused by braking a train running at speeds of 50km/h, 60km/h, and 70km/h, acting on the elevated structures of rubber-wheeled Light Rail Transit (LRT) trains. The authors also briefly describe the analyzed results of the braking force acting on the substructures of elevated light-rail structures. The test-results presented here in this paper can be referenced when establishing design guidelines or standards for elevated structures of LRT systems.

Future structural stability design for composite space and airframe structures

Space and aircraft industry demands for reduced development and operating costs. Structural weight reduction by exploitation of structural reserves in composite space and aerospace structures contributes to this aim, however, it requires accurate and experimentally validated stability analysis. Currently, the potential of composite light weight structures, which are prone to buckling, is not fully exploited as appropriate guidelines in the field of aerospace and space applications do not exist. This paper deals with the state-of-the-art advances and challenges related to coupled stability analysis of composite structures which show very complex stability behaviour. Two types of thin-walled light weight structures endangered by buckling will be considered; imperfection tolerant and imperfection sensitive structures. For both groups improved design guidelines for composites structures are still under development. This paper gives a short state-of-the-art and presents proposals for future design guidelines.

Optimization of Piezo-fibre Composite with IDE Embedded in a Multilayer Glass Fibre Composite

This paper deals with studying the effect of positioning and number of PFC with IDE (PFC-W14) embedded in a multilayer glass fibre composite for energy harvesting. Vacuum Bagging process is used to fabricate eight Multi- layered composite with PFC-W14 embedded inside the specimen at different locations and numbers. The PFC-W14 is positioned at different layers of the composite and number of PFC-W14 is varied in order to study various cases of strain acting on composite. Vibration test for different frequencies were conducted on these eight specimen using electro-dynamic shaker. The generated energy is directly proportional to the strain or voltage generated along the perpendicular axis of the direction of the strain applied, which is collected by the Integrated Digitated Electrodes. The max frequency of vibration at which max voltage is generated by each specimen is observed for different locations and numbers. The results of this study are presented with an eye toward obtaining guidelines for design of useful energy harvesting structures.

On the Suppression Band and Bandgap of Planar Electromagnetic Bandgap Structures

Electromagnetic bandgap structures are considered a viable solution for the problem of switching noise in printed circuit boards and packages. Less attention, however, has been given to whether or not the introduction of EBGs affects the EMI potential of the circuit to couple unwanted energy to neighboring layers or interconnects. In this paper, we show that the bandgap of EBG structures, as generated using the Brillouin diagram, does not necessarily correspond to the suppression bandwidth typically generated usingS-parameters. We show that the reactive near fields radiating from openings within the EBG layers can be substantial and are present in the entire frequency band including propagating and nonpropagating mode regions. These fields decay fast with distance; however, they can couple significant energy to adjacent layers and to signal lines. The findings are validated using full-wave three-dimensional numerical simulation. Based on this work, design guidelines for EBG structures can be drawn to insure not only suppression of switching noise but also minimization of EMI and insuring signal integrity.

Influence of loading rate on failure mode of reinforced concrete members

The lack of simplified methods for accurately predicting the response mode of reinforced concrete structural members (predominantly beams and columns) to impulsive loads indicates a lack of fundamental understanding of the complicated response of members in this situation. This often leads to engineers using over-simplified analytical methods or developing complex finite-element models, the reliability of which has been questioned. This paper presents the development of a theoretical model for predicting the initial demand on a reinforced concrete member subjected to impulsive loads, which can be used to show whether a brittle shear failure results. The model treats the response as being dominated by a wave phenomenon and employing a time increment approach to solve the equation of motion. Under impact loading, the model is able to demonstrate why higher velocity impacts are more likely to cause brittle shear failures in reinforced concrete beams than slower ones for the same impact energy. The paper concludes by extending the proposed method to predict the shear and bending demands on a blast-loaded member. It is hoped that through this new analytical model, design guidelines for new structures can be improved and better assessments of the vulnerability of existing structures can be carried out.