Cross-sectional Dimensions Research Articles

Axial compressive behavior and capacity prediction of concrete-filled cold-formed lipped channel PEC stub columns

The stability and capacity of thin-walled steel columns can be considerably upgraded by filling concrete into hollow spaces surrounded by cold-formed lipped channel (CLC) and external battens. However, there is limited experimental data available, especially for the axial compression behavior of concrete-filled CLC partially encased composite (PEC) columns. This paper aims to investigate the compressive behavior of CLC-PEC short columns and presents an analytical model for predicting the axial capacity of the column. The study explores the influences of cross-sectional dimensions and external batten plate configurations on the compressive performance of CLC-PEC columns through axial compression tests conducted on 12 short column specimens. The results indicate that the failure modes of the specimens involve localized concrete spalling on the exposed side at the lower part of the column, along with a elephant foot-shaped buckling of the cold-formed steel lipped channel. The damage surface of the confined concrete was obtained by circumferential cutting of the buckling location. The findings highlight the significant influence of the character of the CLC section on the ineffectively confined area at the failure surface, with a dumbbell-shaped effective confinement zone revealing the presence of a highly confined area. Based on the calibrated failure surfaces, a numerical model-based study of the axial stress distribution in the concrete core was then carried out to estimate the confinement effect of the columns under peak loading. The study employed multiple regression analysis to quantify the area ratio of the confined zone to the concrete core based on finite element analysis (FEA) results from 143 CLC-PEC columns. The proposed model was evaluated against test results and found to be more reliable than axial compression loads based on the superposition strength method. The proposed axial capacity of short columns takes into account the slenderness ratio of each member.

Female Directorship And Corporate Social Responsibility Disclosure In Nigeria: The Moderating Role Of Firm Size

Companies have witnessed more stringent pressure for corporate social responsibility reporting and the pressure has become critical for their long-term viability and success. Many studies have been conducted to determine the effect of corporate governance mechanism on corporate social responsibility disclosure both locally and internationally, but the studies have yielded inconsistent results. The moderating role of company size on the effect of corporate governance mechanism on corporate social responsibility disclosure has not been significantly studied in the Nigerian context. This study is to examine the effect of corporate governance mechanism on corporate social responsibility disclosure, and the moderating role of firm size. Ex-post facto research design was employed with cross sectional and time series dimensions. Secondary data was obtained from annual reports and accounts of listed manufacturing companies in Nigeria from 2012 to 2023 using disclosure checklist adopted from previous studies. The data was analysed using ordinary least square regressions to determine the effect of female directors on corporate social responsibility disclosure and the moderating role of firm size in listed manufacturing companies in Nigeria. The findings of the study revealed that: female directors have a positive and significant effect on corporate social responsibility disclosure in Nigeria; Firm size has a significant and positive moderating effect on the effect of female directors on corporate social responsibility disclosure of listed manufacturing companies in Nigeria. The study recommends that government and policy makers should set minimum benchmark for female directorship on corporate governance in Nigeria in order to encourage more corporate information disclosures

In Situ Multiphysical Metrology for Photonic Wire Bonding by Two-Photon Polymerization.

Femtosecond laser two-photon polymerization (TPP) technology, known for its high precision and its ability to fabricate arbitrary 3D structures, has been widely applied in the production of various micro/nano optical devices, achieving significant advancements, particularly in the field of photonic wire bonding (PWB) for optical interconnects. Currently, research on optimizing both the optical loss and production reliability of polymeric photonic wires is still in its early stages. One of the key challenges is that inadequate metrology methods cannot meet the demand for multiphysical measurements in practical scenarios. This study utilizes novel in situ scanning electron microscopy (SEM) to monitor the working PWBs fabricated by TPP technology at the microscale. Optical and mechanical measurements are made simultaneously to evaluate the production qualities and to study the multiphysical coupling effects of PWBs. The results reveal that photonic wires with larger local curvature radii are more prone to plastic failure, while those with smaller local curvature radii recover elastically. Furthermore, larger cross-sectional dimensions contribute dominantly to the improved mechanical robustness. The optical-loss deterioration of the elastically deformed photonic wire is only temporary, and can be fully recovered when the load is removed. After further optimization based on the results of multiphysical metrology, the PWBs fabricated in this work achieve a minimum insertion loss of 0.6 dB. In this study, the multiphysical analysis of PWBs carried out by in situ SEM metrology offers a novel perspective for optimizing the design and performance of microscale polymeric waveguides, which could potentially promote the mass production reliability of TPP technology in the field of chip-level optical interconnection.

Global buckling and residual capacities of circular recycled aggregate concrete-filled stainless steel tube (RACFSST) columns after exposure to fire

The post-fire flexural buckling behaviour and capacities of circular recycled aggregate concrete-filled stainless steel tube (RACFSST) columns are studied in this paper, underpinned by testing and numerical modelling. A testing programme was firstly conducted on twelve column specimens designed with three recycled coarse aggregate replacement ratios (0%, 35% and 70%), including nine column specimens after exposure to the ISO 834 standard fire for 15 min, 30 min and 45 min and three reference column specimens at ambient temperature. The test failure modes, load–mid-height lateral deflection curves and failure loads were reported in detail. The influences of heating durations and recycled coarse aggregate replacement ratios on failure loads and mid-height lateral deflections at failure loads of circular RACFSST column specimens were discussed and their lateral deflection distributions were analysed. The testing programme was followed by a numerical modelling programme, where thermal and mechanical finite element models were developed to repeat the experimental results and afterwards used to carry out parametric studies to generate a numerical data pool over a wide range of cross-section dimensions and member lengths. Based on the test and numerical data, the relevant design rules for circular natural aggregate concrete-filled carbon steel tube columns at ambient temperature, as specified in the European code, Australian/New Zealand standard and American specification, were evaluated, using post-fire material properties, for their applicability to circular RACFSST columns after exposure to fire. It was revealed from the evaluation results that the three design codes led to overall acceptable levels of accuracy and consistency in predicting post-fire flexural buckling capacities of circular RACFSST columns, but with some unsafe predictions.

Post-Fire Stability Bearing Capacity of I-Shaped Aluminum Alloy Members Under Axial Compression

Compared to steel structures, aluminum alloy structures are more susceptible to fire damage. Accurately evaluating the residual bearing capacity of fire-damaged aluminum alloy members is crucial for effective post-disaster management. Therefore, this paper investigates the post-fire bearing capacity of I-shaped aluminum alloy members under axial compression. First, a post-fire test on 16 I-shaped aluminum alloy members under axial compression was carried out. The test results indicate that all specimens fail by the minor axis flexural buckling, and the bearing capacity of the specimens decreases with the increase of the slenderness ratio. Moreover, a trilinear relationship is found between bearing capacity and post-fire temperatures. Second, finite element (FE) models are established using ABAQUS and validated against the test results. Subsequently, numerical analysis is carried out, considering various aluminum alloy brands, post-fire temperatures, slenderness ratios, initial geometrical imperfections, and cross-section dimensions. Through the statistical regression technology and the introduction of strength and stability-bearing capacity reduction coefficients, the formulae for estimating the post-fire stability-bearing capacity of I-shaped aluminum alloy members under axial compression are derived. Finally, the proposed formulae are verified to be accurate through error analysis.

Mechanical Analysis and Optimization of Concrete Structures Based on Advanced Finite Element Method

This article explores the mechanical analysis and optimization problems of concrete structures based on the Advanced Finite Element Method. By integrating advanced numerical techniques with practical engineering cases, this study aims to improve the safety and economy of concrete structure design. Firstly, the paper outlines the limitations of traditional finite element methods in concrete structure analysis, such as insufficient computational accuracy and low computational efficiency. Subsequently, by introducing AFEM, we significantly improved the accuracy and efficiency of the analysis. For example, when simulating a complex bridge structure, AFEM not only reduces the calculation time by about 25%, but also improves the accuracy of stress distribution prediction by more than 10%. In the optimization stage, we utilized the analysis results of AFEM and optimized the material consumption, cross-sectional dimensions, and reinforcement parameters of concrete structures through multi-objective optimization algorithms. A comprehensive data analysis underscores that the optimized concrete structure triumphantly meets all safety performance criteria while achieving a remarkable 12% reduction in material usage. This substantial material savings translates into a substantial 8% decrease in overall construction costs, significantly bolstering the project’s economic feasibility. Moreover, these cost savings not only amplify the project’s profitability but also play a pivotal role in enhancing the structure’s longevity and durability, thereby contributing to its sustainable performance over its entire service life. Furthermore, we delved into the capability of AFEM in simulating intricate phenomena such as the nonlinear behavior of concrete materials, crack propagation patterns, and the intricate interactions between steel reinforcements and concrete. These complex mechanical behaviors are crucial for the safety and stability of structures, and AFEM provides more comprehensive and accurate references for structural design by accurately simulating these behaviors. This article conducts in-depth research on the mechanical analysis and optimization of concrete structures based on AFEM, and demonstrates the significant advantages of AFEM in improving structural safety and economy through specific data. These research results not only provide new theoretical support and practical tools for concrete structure design, but also provide valuable references for future research and application in related fields.

Comparison of subcooled flow boiling in concentric annuli with bare and finned surfaces

In this study, the hydrodynamic and thermal characteristics of subcooled flow boiling in concentric annuli with inner heating wires, featuring bare and finned surfaces designed for heat transfer enhancement, were experimentally investigated, with a focus on cooling technology for EV charging cables. The bare wire test module consisted of a 300 mm long wire, with a 290 mm long inner heating surface and a diameter of 10 mm. The outer tube was constructed from transparent polycarbonate with a 22 mm diameter, allowing optical access to observe the flow. The finned wire test module has an identical construction, except for the addition of six longitudinally extruded fins with cross-sectional dimensions of 2 × 5 mm2. Experiments and flow visualizations, aided by high speed imaging, were conducted using HFE-7100 as the working fluid at mass velocities, G, 463.7 to 1,309.6 kg/m2s and heat fluxes from 0.90 to 9.93 W/cm2, under inlet pressures between 120 and 240 kPa. The study investigated thermal non-equilibrium phenomena, driven by asymmetric bubble accumulation, and their effects on circumferential temperature distribution, which showed opposing trends between the bare and finned surfaces. An evaluation of previous empirical correlations for predicting subcooled flow boiling heat transfer coefficients was performed, followed by an assessment of fin performance in enhancing heat transfer. A comparative analysis with the bare surface module of the same dimensions confirmed that the longitudinal fins provided superior thermal management, maintaining the surface temperature below the safety threshold, Ts,safe. The longitudinal fins demonstrated a 54.5 % reduction in charging time and a 183.7 % increase in charging current for charging up to 80 % state of charge (SOC) of a 77.4 kWh battery, compared to the bare wire.

Characterization and simulation of AlSi10Mg reinforcement structures by direct energy deposition by means of laser beam and powder

Among metal additive manufacturing technologies, direct energy deposition (DED) processes have the advantage to be easily integrable in a manufacturing chain with other conventional technologies. This characteristic can be exploited by designing reinforcement structures to be added by DED onto pre-existing subcomponents to tailor the part’s mechanical properties while keeping the part lightweight. This study focuses on DED by means of laser beam and powder process optimization to improve material quality and geometrical accuracy of AlSi10Mg reinforcement structures while preventing excessive thermal deformations and material dilution into the substrate. These results are compared with finite elements numerical simulations of the deposition process, comprising thermo-elastic deformation and material deposition, to predict the bending and reinforcement of the processed substrate. In particular, the model includes the deterministic prediction of the deposition profile as a function of the process parameters and a few condition-specific coefficients: once calibrated, the model was used to compare the numerical and experimental residual deformation of the reinforced sample, obtaining promising agreement. The reinforcement provided to a 1.5 mm thick substrate by a single wall of deposited materials, with cross-sectional dimensions of 2 mm in width and 2.5 mm in height, was evaluated by three points bending. With the reinforcement on the tensile side of the stresses, the energy absorbed by the material plastic deformation increased by 2.4% as compared to the substrate alone, while with the reinforcement on the compression side of the stresses the energy absorption increased by 75.8% on average.

Experimental and numerical investigations on flexural behavior of apex joints in aluminum alloy portal frames

Aluminum alloy portal frames (AAPFs) find extensive applications in lightweight and temporary structures owing to their light weight, excellent corrosion resistance, and ease of installation and disassembly. Existing design equations for cold-formed steel portal frame (CFSPF) apex joints are not applicable to AAPF apex joints due to significant differences in structural configuration. Therefore, dedicated research is needed to develop design guidelines for AAPF apex joints. Consequently, this paper conducts experimental and numerical investigations on flexural behavior of AAPF apex joints. Initially, bending tests are conducted on three AAPF apex joints, revealing failure modes including clamping plate buckling and beam failure. The flexural behavior of apex joints throughout the entire process is analyzed based on moment-rotation curves and moment-strain curves. Subsequently, finite element (FE) models are established and validated by comparing the FE results with the experimental results. Following this validation, parameter analysis is conducted considering the influence of beam cross-sectional dimensions, clamping plate dimensions, bolt dimensions, and layout. Finally, based on theoretical and numerical investigation, the calculation equation for the flexural capacity of AAPF joints is derived, offering valuable reference for engineering design.

Evaluation of the Effect of Pre-bent Z-shaped Titanium Plate on Narrowing of Zygomatic Arch in L-shaped Reduction Malarplasty

Objective: Pre-bent titanium plates are widely used for internal fixation in L-shaped zygomatic reduction. The aim is to evaluate the effect of pre-bent Z-shaped titanium plate on the narrowing of the zygomatic arch in L-shaped reduction malarplasty. Methods: Thirty cosmetic female patients were selected and scanned using computed tomography (CT). The CT images of pre-operation (T1) and post-operation(T2) were re-established through MIMICS26.0 (Materialise). After the 2 images were registered based on the skull base, the narrowing distance (ZRN) at the posterior end of the free zygomatic arch, as well as the preoperative and postoperative cross-sectional dimensions of the zygomatic arch, were measured. The ZRN and the altitude of the pre-bent titanium plate (TA) were compared using an independent t test, and their correlation was also analyzed using the Pearson coefficient. The preoperative and postoperative longest diameter (L1) and shortest diameter (L2) of the posterior zygomatic arch were compared using a paired t test. Results: The TA was 3.80±0.82 mm and the ZRN was 3.21±0.82 mm. The difference value was 0.59±0.41 mm, which was statistically significant. TA showed a strong correlation with ZRN (r=0.916, P=0.002). The L1 and L2 of the zygomatic arch root were slightly reduced postoperatively. Conclusion: The pre-bent Z-shaped titanium plate does not completely correspond to the zygomatic arch narrowing distance in the actual application of L-shaped reduction malarplasty. However, it can control the narrowing distance of the zygomatic arch predictably, and achieve satisfactory surgical outcomes.

Machine Learning-Based Strength Prediction of Round-Ended Concrete-Filled Steel Tube

Round-ended concrete-filled steel tubes (RECFSTs) present very different performances between the primary and secondary axes, which renders them particularly suitable for use as bridge piers and arches. In recent years, research into RECFST heavily relies on experimental procedures restricting the parameter range under consideration, which narrows the far-reaching applicability of RECFST. This study employs advanced machine learning methods to predict the axial load-bearing capacity of RECFST with a wide parameter range. Firstly, a machine learning database comprising 2400 RECFSTs is established, which covers a wider range of commonly used material strengths and cross-sectional dimensions. Three machine learning prediction models of this database are then developed, respectively, using different algorithms. The robustness of the machine learning models is evaluated by predicting the axial load-bearing capacity of 60 RECFST specimens from existing references. The results demonstrated that the machine learning models provided superior predictive accuracy compared to theoretical or code-based formulas. A graphical user interface (GUI) is ultimately developed based on the machine learning prediction models to predict the axial load-bearing capacity of RECFST. This tool facilitates rapid and accurate RECFST design.

Microstructure Evolution and Forming Characteristics of Post-Weld Composite Treatment of 6061 Aluminum Alloy Tailor Welded Blanks

The mechanical properties and cross-sectional geometric dimensions of the fusion zone (FZ), heat affected zone (HAZ), and base metal (BM) of 6xxx series aluminum alloys are inconsistent after filler wire welding, which reduces the formability of aluminum alloy tailor welded blanks (TWBs). This paper proposes a post-weld cold rolling-solution heat treatment (PWCR-SHT) composite process, and the effects of weld excess metal, plastic deformation, and SHT on the formability of aluminum alloy TWBs are studied. The results show that the PWCR-SHT composite process eliminates the weld excess metal and internal pores, reduces the stress concentration at the weld toe, eliminates the local strain hardening behavior, and causes recrystallization in the FZ region. The cupping value of aluminum alloy TWBs using SHT is 105% of BM, in comparison, the cupping value of aluminum alloy TWBs using the PWCR-SHT composite process is 119% of BM, which is the result of the combined effect of geometric dimensions consistency and mechanical properties consistency.

Eccentric load capacity of ultra-high strength concrete-filled steel tubular lattice short columns

To explore the behavior of ultra-high strength concrete filled steel tubular (UHSC-FST) lattice short columns under eccentric compressive loads, experimental analyses on four specimens and 276 finite element models using ABAQUS were conducted. The study focused on the effects of steel tube wall thickness, concrete strength, steel tube strength, and load eccentricity on failure modes, load-displacement curves, and ultimate load-bearing capacity. Results showed that for columns with minor eccentricity-induced compressive failure, the reduction coefficient of ultimate load capacity has a weak correlation with the parameters. However, for columns with significant eccentricity-induced tensile failure, the reduction coefficient increases with steel tube thickness and strength and decreases with concrete strength. The center-to-center distance of the columns has a minor effect. Based on these findings, a comparative analysis of existing standards was conducted, leading to the development of an accurate method for calculating the ultimate load-bearing capacity of eccentric CFST lattice columns. This method is applicable to various cross-sectional dimensions, material strengths, and steel tube wall thicknesses, with calculation errors within 10 %, ensuring it meets engineering precision requirements.

Lateral-Torsional Failure and DSM Design of CFS Lipped Channel Beams at Room and Elevated Temperatures

About a decade ago, in-depth investigations on the behaviour of cold-formed steel (CFS) single-span simply supported lipped channel beams failing in lateral-torsional modes at both room and elevated temperatures were reported at QUT (Queensland Technical University). They revealed a significant underestimation of the lateral-torsional (LT) failure moments by the Direct Strength Method (DSM) global design curve at room temperature, then codified in the Australian/New Zealand and North American specifications. In order to remedy this situation, these authors proposed two novel DSM-based beam strength curve sets, which were found to substantially improve the LT failure moment prediction quality, both at room and elevated temperatures. This work aims at extending the scope of the above investigations, by analysing a visibly larger set of CFS lipped channel beams at elevated temperatures (up to 800 °C), exhibiting (i) various cross-section dimensions and yield stresses, selected to cover wider LT slenderness ranges, (ii) two end support conditions, differing only in the end cross-section wall displacement/rotation and warping restraints (either fully free or fully prevented), and (iii) temperature-dependent steel material properties according with the model prescribed in Part 1-2 of Eurocode 3. The results presented and discussed consist of beam LT post-buckling equilibrium paths and failure moments, obtained through Abaqus shell finite element GMNIA that include critical-mode (LT) initial geometrical imperfections. Lastly, the numerical failure moment data obtained in this work and reported in the literature are used to develop and propose a new unified set of DSM-based strength curves capable of adequately handling beam LT failures at room or elevated temperatures. Since it is shown that the proposed strength curve set provides a quite good LT failure moment prediction quality, it is fair to argue that it constitutes a good starting point to search for an efficient general DSM-based design approach for CFS beams failing in LT modes at room and elevated temperatures.

Pharmaceutical/Biomedical Applications of Electrospun Nanofibers - Comprehensive Review, Attentive to Process Parameters and Patent Landscape.

Nanotechnology is a new science and business endeavour with worldwide economic benefits. Growing knowledge of nanomaterial fabrication techniques has increased the focus on nanomaterial preparation for various purposes. Nanofibers are one-dimensional nanomaterials having distinct physicochemical properties and characteristics. Nanofibers are nanomaterial types with a cross-sectional dimension of tens to hundreds of nanometres. They may create high porosity mesh networks with significant interconnections among pores, making them suitable for advanced applications. Electrospinning stands out for its ease of use, flexibility, low cost, and variety among the approaches described in the literature. The most common method for making nanofibers is electrospinning. This article extensively describes and summarizes the impact of various process variables on the fabrication of nanofibers. Special attention has been given to scientific and patent prospection to confirm the research interests in nanofibers.

Investigation on post-fire bond behavior between section steel and concrete in SRCFST columns

This paper presents an experimental and numerical investigation on post-fire bond behavior between section steel and concrete in steel-reinforced concrete-filled steel tubular (SRCFST) columns. The pushout tests on 22 post-fire SRCFST specimens were conducted, and test parameters included the fire exposure time, cross-sectional dimension of section steel, section steel-concrete interface length, and the loading ways. The effect of different parameters on the load-slip curves were analyzed. The results shown that the fire exposure time has an obvious influence on the bond strength of the interface. As the fire exposure time increases from 30 min to 60 min and 90 min, the average ultimate bond strength of post-fire specimens decreases by 48.3 % and 69.5 %, respectively. Based on the experimental results, the simplified full-range bond strength-slip model of the section steel-concrete interface in post-fire SRCFST columns was proposed. The finite element analysis model on the bond behavior of the section steel-concrete interface of post-fire SRCFST columns was finally developed and calibrated, and was used to analyze the stress distribution and variation of the section steel-concrete interface.

A methodical approach to design adiabatic waveguide couplers for heterogeneous integrated photonics

Abstract We present an elegant and effective approach for the design of adiabatic waveguide couplers tailored for the heterogeneous integration of photonic building blocks. This method empowers users to incorporate the shortest taper(s) in their designs, while upholding optimal coupling efficiency. The technique assesses mode overlap between a minimum of two waveguides within the cross-section of any heterogeneous material stack, determining the necessary waveguide cross-sectional dimension to achieve optimal coupling efficiency. Two illustrative design applications are showcased and compared to a linear, concave, and convex taper for reference: a SiN-to-polymer structure exhibiting a 40% coupling improvement and a Si-to-GeSi structure having a 2.2 up to 5 times shorter length.

Post-fire flexural buckling and resistances of square recycled aggregate concrete-filled stainless steel tube (RACFSST) columns

The flexural buckling behaviour and residual resistances of square recycled aggregate concrete-filled stainless steel tube (RACFSST) columns after exposure to fire are studied in this paper, based on experiments and numerical modelling. Twelve column specimens, fabricated from concretes with three recycled coarse aggregate replacement ratios (0%, 35% and 70%), were tested after exposure to the ISO 834 standard fire for 0 min (i.e. at ambient temperature), 15 min, 30 min and 45 min. The experimental investigation included heating of specimens, cylinder tests as well as post-fire initial global geometric imperfection measurements, tensile coupon tests and pin-ended column tests. The test setups, procedures and results were fully reported and the ductility indices, lateral deflection distributions and longitudinal strains were discussed and analysed. A numerical investigation was afterwards carried out, where the test results were used to validate thermal and mechanical finite element models; upon validation, parametric studies were conducted to expand the test data bank over a wider range of cross-section dimensions and member lengths. On the basis of the test and numerical data, the relevant design rules for square natural aggregate concrete-filled carbon steel tube columns at ambient temperature, as set out in the European code, Australian/New Zealand standard and American specification, were assessed, using post-fire material properties, for their applicability to square RACFSST columns after exposure to fire. It was found from the assessment results that the three design codes resulted in overall accurate and consistent post-fire flexural buckling resistance predictions but some were unsafe.

Failure Probability-Based Optimal Seismic Design of Reinforced Concrete Structures Using Genetic Algorithms

Artificial intelligence (AI) has enabled several optimization techniques for structural design, including machine learning, evolutionary algorithms, as in the case of genetic algorithms, reinforced learning, deep learning, etc. Although the use of AI for weight optimization in steel and concrete buildings has been extensively studied in recent decades, multi-objective optimization for reinforced concrete (RC) and steel buildings remains challenging due to the difficulty in establishing independent objective functions and obtaining Pareto fronts. The well-known Non-Dominated Sorting Genetic Algorithm II (NSGA-II) is an efficient genetic algorithm approach for multi-objective optimization. In this work, the NSGA-II approach is considered for the multi-objective structural optimization of three-dimensional RC buildings subjected to earthquakes. For the objective of this study, two function objectives are considered: minimizing total cost and the probability of structural failure, which are obtained via several nonlinear seismic analyses of the RC buildings. Beams and columns’ cross-sectional dimensions are selected as design variables, and the Mexican Building Code (MBC) specifications are imposed as design constraints. Pareto fronts are obtained for two RC-framed buildings located in Mexico City (soft soil sites), which demonstrate the efficiency and accuracy of NSGA-II for structural optimization.

Mesoscopic structure of the stock market and portfolio optimization

AbstractThe idiosyncratic and systemic components of market structure have been shown to be responsible for the departure of the optimal mean-variance allocation from the heuristic ‘equally weighted’ portfolio. In this paper, we exploit clustering techniques derived from Random Matrix Theory to study a third, intermediate (mesoscopic) market structure that turns out to be the most stable over time and provides important practical insights from a portfolio management perspective. First, we illustrate the benefits, in terms of predicted and realized risk profiles, of constructing portfolios by filtering out both random and systemic co-movements from the correlation matrix. Second, we redefine the portfolio optimization problem in terms of stock clusters that emerge after filtering. Finally, we propose a new wealth allocation scheme that attaches equal importance to stocks belonging to the same community and show that it further increases the reliability of the constructed portfolios. Results are robust across different time spans, cross sectional dimensions and set of constraints defining the optimization problem.