Structural Upgrade Research Articles

Carbon-FRCM materials for structural upgrade of masonry arch road bridges

Background/PurposeNumerous bridges of the Italian arterial road network were designed for live loads significantly lower than those produced by the current vehicular traffic. Many of them are masonry arch bridges whose load carrying capacity should be assessed for defining the necessary strengthening interventions. In the present paper the design criteria for strengthening masonry bridges with carbon fiber reinforced cementitious matrix (C-FRCM) materials are presented with reference to a masonry arch road bridge built right after the second world war. MethodsThe structure is analyzed both in its original and in its strengthened configuration following the approach of the collapse mechanisms. The considered approach allows to capture the strengthening effect of the C-FRCM material in terms of modification of the collapse mechanism and increase of the load collapse multiplier. Two different configurations of C-FRCM strengthening material applied at the extrados have been considered. In the first configuration the ends of the C-FRCM material are anchored at the vaults imposts, while in the second configuration they are not anchored at the imposts. ResultsTo obtain load collapse multipliers greater than one three layers of C-FRCM strengthening material have to be applied at the extrados of all the three vaults in the case of end anchored strengthened material, while in the case of unanchored strengthening material four layers of C-FRCM strengthening material have to be applied at the extrados of all the three vaults. ConclusionThe performed analyses show a lack of load carrying capacity of about 60% with respect to the load carrying capacity required by current codes. This lack can be filled up adopting the considered strengthening technique.

Assessment and restoration of the first Greek power plant – Registered monument of industrial heritage

The first electric power station in Greece is a registered monument of the international industrial heritage. The building consists of three longitudinal parts with a total area of 4800m2 approximately in plan and has two levels of a height of 3m and 12m respectively. The structural system consists mainly of stone masonry walls and a steel roof. Nowadays the building is scheduled to be reused as a Museum of Electric Power and the need for structural upgrade arose mainly from current seismic requirements. According to the structural assessment study, the prevailing problem of the building is the combination of the presence of very high walls, interrupted by transverse walls at a distance of approximately 80m, and the complete lack of horizontal diaphragms. The building’s architectural, historic and technological value is significant and its preservation, by minimization of interventions, posed several problems to the retrofit design. New steel frames connected to and cooperating with the masonry walls were designed to bear the vertical roof loads and restore the horizontal diaphragm at the roof level, while also reducing the seismic actions at the walls. The total required strength was achieved by additionally implementing vertical post-tensioning bars and FRP strips.

Enhancement of the Wear Particle Monitoring Capability of Oil Debris Sensors Using a Maximal Overlap Discrete Wavelet Transform with Optimal Decomposition Depth

Oil debris sensors are effective tools to monitor wear particles in lubricants. For in situ applications, surrounding noise and vibration interferences often distort the oil debris signature of the sensor. Hence extracting oil debris signatures from sensor signals is a challenging task for wear particle monitoring. In this paper we employ the maximal overlap discrete wavelet transform (MODWT) with optimal decomposition depth to enhance the wear particle monitoring capability. The sensor signal is decomposed by the MODWT into different depths for detecting the wear particle existence. To extract the authentic particle signature with minimal distortion, the root mean square deviation of kurtosis value of the segmented signal residue is adopted as a criterion to obtain the optimal decomposition depth for the MODWT. The proposed approach is evaluated using both simulated and experimental wear particles. The results show that the present method can improve the oil debris monitoring capability without structural upgrade requirements.

Environmental impact assessment of a WtE plant after structural upgrade measures

The study focuses on analysing the evolution of environmental impacts caused by a medium–large Italian WtE plant before and after revamping and maintenance operations, with the aim of providing an evaluation of how much these structural upgrade measures may affect the total environmental performance.LCA methodology was applied for the modelling and comparison of six WtE scenarios, each describing the main structural upgrades carried out in the plant over the years 1996–2011. The comparison was conducted by adopting 1ton of MSW as the functional unit, and the net contribution from energy recovery to power generation was distinguished by defining consistent national grid electricity mixes for every year considered. The Ecoindicator99 2.09 impact assessment method was used to evaluate the contribution to midpoint and endpoint categories (e.g. carcinogens, respiratory inorganics and organics, climate change, damage to human health). Lastly, the “Pedigree quality matrix” was applied to verify the reliability and robustness of the model created.As expected, the results showed better environmental scores after both the implementation of new procedures and the integration of operations. However, while a net reduction of air emissions seems to be achievable through dedicated flue gas treatment technologies, outcomes underscored potentials for improving the management of bottom ash through the adoption of alternative options aimed to use that solid residue mainly as filler, and to decrease risks from its current disposal in landfill. If the same effort that is put into flue gas treatment were devoted to energy recovery, the targets for the WtE plant could be easily met, achieving a higher sustainability. This aspect is even more complex: national policies for implementing greener and renewable energy sources would result in a lower impact of the national energy mix and, hence, in a lower net avoided burden from energy recovery.The study confirmed the expected improvements, indicating quantitatively the lower environmental impact resulting from structural upgrade operations in a WtE plant. Furthermore, the work highlights the importance of considering the evolution of the national energy mix in LCA studies, especially during the present years of transition from fossil fuels to renewable sources.

Reducing carbon emissions in China: Industrial structural upgrade based on system dynamics

China is now in urgent need to accelerate the transformation of the economic development model, promoting industrial structure upgrades in order to reduce carbon emissions. The goals are to relieve energy constraints, guarantee economic security, and reduce environmental pressures. This study calculated the industrial influence coefficients (IIC) and the industrial carbon emission coefficients (ICEC) of all industries in China in 2007. A system dynamics model was built to simulate the GDP growth and total carbon emissions in three scenarios. Scenario analyses have shown that the industrial structure adjustment based on the calculations of IIC and ICEC is better than the one based on the Chinese Industrial Restructuring Catalog. This study provides a solid research foundation for the government to adjust the industrial structure and reduce carbon emissions.

Fiber-Reinforced Polymers Exposed to Nuclear Power Plant Environment

The effectiveness of fiber-reinforced polymers (FRP) in structural upgrade has been demonstrated repeatedly in short-term laboratory tests and field applications. Consequently, the level of interest in exploring the potential applications of FRP in various types of structures and environments has increased. One of the potential areas of application of FRP is in nuclear power plants (NPP). However, there is very little research data available on the durability of FRP subject to an NPP environment. This paper reports the results from an experimental program aimed to address this knowledge gap. The study involved testing a total of 84 specimens consisting of FRP coupons, FRP-FRP single lap–bonded specimens, and FRP-bonded concrete prisms for their performance before and after exposure to gamma radiation. Both glass and carbon FRPs were included in this study. The specimens were tested for FRP tensile, FRP-to-FRP bond, and FRP-to-concrete bond properties. Results showed that the tensile and bond properties of FRP were not adversely affected in any significant manner as a result of the exposure.

Mechanistic-Based Nondestructive Structural Asset Management Testing to Optimize Low-Volume Road Structural Upgrades

The Saskatchewan, Canada, Ministry of Highways and Infrastructure is investigating integrated structural asset management to help optimize investment in the rural low-volume road (LVR) network. Integrated ground-penetrating radar (GPR) and heavyweight deflectometer (HWD) testing were found to be very effective structural assessment tools that might be used to strategically rehabilitate, maintain, and upgrade Saskatchewan's LVR network, which accounts for 80% of the ministry's total network. This paper demonstrates this integration at a project level to assess the pre- and postconstruction structural condition of two LVRs in Saskatchewan. The preconstruction GPR survey applied in this study showed locations of trapped moisture within the road structure's granular materials. The postconstruction HWD assessed the end product structural integrity of the road after its rehabilitation treatment. The ability to strategically allocate limited financial resources across the extensive in-service LVR system in Saskatchewan on the basis of accurate structural asset management infrastructure performance data was essential for this project, given the high variability in Saskatchewan LVR structures.

Externally bonded grids as strengthening and seismic retrofitting materials of masonry panels

Externally bonded grids are used in this study as a means of increasing the load-carrying and deformation capacity of unreinforced masonry (URM) walls subjected to cyclic loading. The experimental investigation was carried out on two groups of medium-scale, single-wythe wallettes consisting of either perforated fired clay bricks, or solid stone blocks. The specimens were subjected to cyclic loading which induced in-plane flexure combined with axial force, out-of-plane flexure and in-plane shear with axial force. The parameters considered were the number of strengthening layers (one or two layers, applied on both sides), the type of grid (open mesh structures comprising carbon, glass or basalt fibers and polypropylene or polyester), the type of bonding agent (mortars of different compositions or epoxy resin) and the compressive stress level applied to specimens undergoing in-plane loading. Based on the findings of this work the use of externally bonded grids comprises a promising solution for the structural upgrade of existing masonry structures.

Eos Interviews Robert Van Hook, Former AGU Interim Executive Director

Robert Van Hook, who served as AGU's interim executive director since January 2009, led the organization during a transition period that began with the retirement of long‐serving executive director A. F. (“Fred”) Spilhaus Jr. Van Hook's tenure concluded on 30 August when Christine McEntee assumed her position as AGU's new executive director (see Eos, 91(17), 153, 156, 2010). During his tenure at AGU, which overlapped with a global economic recession, Van Hook helped to guide the organization through key structural governance changes, strategic planning, and upgrades in technology, human resources, and accounting. He also helped to revitalize public outreach and member services, among many other efforts.

China’s value-added tax reform, firm behavior and performance

China reformed value-added tax (VAT) by removing investment from the tax base in northeastern provinces in 2004, which is a “natural experiment” of its tax system. Using difference-in-differences method, this paper for the first time investigates the impact of VAT reform on China firms’ fixed asset investment, employment behavior, innovative activities, and productivity, and furthermore discusses the impact of firm behavior on industrial structural upgrade and employment with a firm-level panel data of large and medium-sized manufacturing enterprises in China. We find that VAT reform significantly promotes firms’ fixed asset investment, and increases firms’ capital-labor ratio and productivity; while enhancement of firms’ productivity is mainly achieved by means of substituting labor with capital, rather than independent technology innovation; meanwhile, VAT reform distinctly decreases employment. Our findings have essential policy implications on the extension of VAT reform in the entire China.

Structural Upgrade Using Basalt Fibers for Concrete Confinement

This paper aims to appraise the opportunities provided by a new class of composites based on using basalt fibers bonded with a cement-based matrix as an innovative strengthening material for confinement of reinforced concrete members. The effectiveness of the proposed technique is assessed by comparing different confinement schemes on concrete cylinders: (1) uniaxial glass-fiber-reinforced polymer (FRP) laminates; (2) alkali-resistant fiberglass grids bonded with a cement-based mortar; (3) bidirectional basalt laminates preimpregnated with epoxy resin or latex and then bonded with a cement-based mortar; and (4) a cement-based mortar jacket. The study showed that confinement based on basalt fibers bonded with a cement-based mortar could be a promising solution to overcome some limitations of epoxy-based FRP laminates.

Sutter Health: Developing a Contracting Model to Support Lean Project

Sutter Health is a non-profit, community based healthcare and hospital system headquartered in Sacramento, California. The Sutter system serves more than one hundred communities in Northern California. From its historical roots of being a small community-based hospital in Sacramento, it has grown to be one of the largest healthcare providers in Northern California, caring for more patients than in any other network. Its affiliate-based system includes 27 acute care hospitals, over 3,400 physicians, 41,000 employees and recorded over 2.6 million outpatient visits in 2003. In 1994, after the Northridge earthquake caused significant damage to healthcare facilities in Southern California, The California Legislature enacted SB 1953 - the Hospital Facilities Seismic Safety Act. This requires significant structural seismic upgrades to be accomplished by January 1, 2013. In many cases, it is more cost-effective to replace existing facilities, rather than seismically retrofit. Sutter Health was facing a $5.5 billion design and construction undertaking to conclude by 2012. Senior management considered success to be traversing the risks associated with the program and reliably delivering the projects. Different governing and execution bodies were installed in place. Barrowing from practices that worked in the past was emphasized as well as innovating and adopting new practices. This led to the development and implementation of Lean Project Delivery. The paper outlines the features and shares the experiences.

Simplified Nonlinear Analysis of Strengthened Concrete Beams Based on a Rigorous Approach

The external fiber reinforced polymer (FRP) flexural and shear strengthening of reinforced concrete beams is a well-established technique for structural rehabilitation and upgrade. In the present work, an analytical solution is developed for the load.deflection calculation of FRP strengthened simple beams at any load stage. The solution assumes a trilinear moment.curvature response characterized by the flexural crack initiation, steel yielding, and ultimate capacity. Closed form expressions are presented for the case of simple beams subjected to three-point bending, four-point bending, and uniform load. These expressions are derived for beams with any extent of uncracked, postcracked, and postyielded regions along their span. An extensive parametric study is conducted yielding unique linear relationships between basic sectional moments of inertia and their corresponding effective beam values for a wide range of geometric and material variables considered. Accordingly, a simplified analysis procedure is developed by adopting a trilinear load.deflection response. The effectiveness of the simplified procedure is demonstrated by comparing its results to those of the analytical solution and the experimental values.

Selective Upgrade of Underdesigned Reinforced Concrete Beam-Column Joints Using Carbon Fiber-Reinforced Polymers

Seismic regions are characterized by reinforced concrete (RC) structures designed without seismic provisions. As the structural upgrade of such structures becomes necessary, one of the approaches that recent design guidelines suggest is that of the hierarchy of strength. By increasing the strength and ductility of critical components, their brittle and catastrophic failure is prevented and the occurrence of more desirable mechanisms is promoted. This approach allows improving the global behavior of the structure. The key issue of strengthening design of RC frames is represented by the beam-column connection. This paper presents a technique based on fiber-reinforced polymer composites for the seismic upgrade of RC beam-column connections that was validated with tests on 11 initially underdesigned specimens. The results of the experimental investigation are presented, and a discussion on how different parameters influenced the behavior of the samples in terms of strength or ductility, or both, is offered.

Closed form equations for FRP flexural strengthening design of RC beams

FRP external strengthening has proven its success in structural rehabilitation and upgrade. Researchers and practicing engineers are working towards introducing its design procedures to standard codes of practice. The current state of the art flexural design process suggests an iterative approach, which may lead to tedious calculations. This paper provides a direct approach furnishing calculation simplicity and design efficiency. It also proposes equations to design doubly strengthened sections for the first time. The expressions derived for doubly reinforced rectangular and Tee sections are written in a compact form based on those formulated for singly reinforced rectangular sections. Verifications against experimental results are performed. The solution, using the closed form equations, is compared to that of other procedures available in the literature through design examples. Tee section design is also presented and illustrated through a comparison with an analysis example. A doubly strengthened beam design example is also solved. The prevention of premature FRP plate separation using U-wraps to develop the full flexural capacity is also discussed.

Converging Disciplines during Structural and Environmental Upgrades: The Troxell-Steckel House

Converging Disciplines during Structural and Environmental Upgrades: The Troxell-Steckel House

Design of Energy Dissipation Devices Based on Concept of Damage Control

Recent laboratory and theoretical studies show that structures with added energy dissipation devices will generally exhibit inelastic behavior when they are subjected to strong ground motion; therefore, the assumption of linear structural responses has to be eliminated in the design of such devices for the purposes of structural upgrade and retrofit. In this paper, effects of high damping on a structure experiencing inelastic deformation under seismic ground motions are examined. The importance of the energy concept in the design of energy dissipation devices for structural applications is addressed, and a new design method is proposed based on the concept of damage control. To establish a rational design approach, an explicit procedure is developed to transform a multidegree-of-freedom system to an equivalent single-degree-of-freedom model in the inelastic range so that the evaluation of structural seismic performance with and without the added devices can be easily performed. While the example is given for the application of viscoelastic dampers, the proposed method is also applicable to other devices, such as friction and viscous dampers, under certain condition.

Continued enhancements to the commercial atlas launch system

Since the October 1988 update on the Commercial Atlas Launch System presented to the IAF, additional enhancements have been incorporated into the launch vehicles offered. Previous papers have dealt with performance and configuration details of the Atlas I, II, IIA launch vehicles. This paper discusses the latest addition to the line of Atlas launch vehicles, namely the Atlas IIAS, and other enhancements that have been made across the board. Discussion of the Atlas IIAS configuration includes details about structural upgrades made to the booster stage, the basic configuration of the solid rocket motors (SRMs) used, upgrades made to the launch facility, effects of the configuration change on spacecraft environments, and overall performance enhancement. By selective incorporation of the enhancement available, the performance of Atlas launch vehicles can be tailored to the specified requirements of particular missions. These capability enhancements include minimum residual shutdown of the Centaur upper stage, transverse spin separation, and small payload accommodations (SPA). When matched with existing capabilities of in-flight retargeting and precision pointing and injection accuracies, these improvements lead to the availability of a launch vehicle that can be tailored to a spacecraft's unique requirements. Finally, a review of performance capabilities for the entire line of Atlas launch vehicles is presented, capping a comprehensive view of the current state of the Atlas launch vehicle.