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Al-Sabah, Salam
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Al-Sabah, Salam
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Al-Sabah, Salam
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Now showing 1 - 9 of 9
- PublicationDynamic Amplification Factor of Continuous versus Simply Supported Bridges Due to the Action of a Moving Load(2014-08-29)
; ; ; This paper extends the research on dynamic amplification factors (DAFs) caused by traffic loading from simply supported to continuous (highway and railway) bridges. DAF is defined here as the ratio of maximum total load effect to maximum static load effect at a given section (mid-span). Another dynamic amplification factor FDAF can be defined as the ratio of the maximum total load effect throughout the entire bridge length to the maximum static load effect at a given section (mid-span). For continuous beam DAF/FDAF can be determined for both sagging and hogging bending moments. Noticeable differences appear among DAF/FDAF of mid-span bending moment in a simply supported beam, DAF/FDAF of the mid-span bending moment in a continuous beam and the DAF/FDAF of the bending moment over the internal support in a continuous beam. Three span lengths are tested in the simply supported beam models as well as three continuous beams made of two equal spans. Each model is subjected to a moving constant point load that travels at different velocities. The location of the maximum total moment varies depending on the speed. FDAF and DAF are plotted versus frequency ratio. The results showed that FDAF is often greater than DAF in simply supported and continuous beams. Also, FDAF of sagging bending moment in continuous beam is about 12 % greater than that the simply supported case. Moreover, the results showed that FDAF of hogging bending moments is about 3 % greater than those of sagging bending moments in continuous beam. Consequently, all values were larger than those of simply supported case.450 - PublicationStrength assessment of in-situ concrete for the evaluation of structural capacity: State of the art(Civil Engineering Research Association of Ireland, 2016-08-30)
; ; With more emphasis on reusing and extending the life of structures, it often becomes necessary to assess the capacity of existing concrete structures. One major component of this assessment relates to the concrete strength. Most reliable results are obtained by taking cores. However, such assessment is ideally made with a combination of destructive and nondestructive testing to minimise damage to the structure. The currently available methods for assessing in-situ concrete strength of the existing structures can be broadly divided into two groups. One group of tests is completely non-destructive. The other group is partially destructive where limited damage to the surface is caused by the tests. For the strength evaluation of existing concrete, methods such as surface hardness test, ultrasonic pulse velocity test, penetration resistance test and maturity test fall under the non-destructive category. Partially destructive tests include pull out test, CAPO test, pull off test and break off test. This paper critically evaluates and analyses the applicability and limitations of the methods used for evaluating concrete strength in existing structures. Most methods for strength evaluation are found to measure a certain property such as elasticity, density, tensile strength or hardness of concrete and then relate the measured value to compressive strength. Studies on these methods show a wide variation in the correlations between estimated and predicted compressive strength. Partially destructive methods are noted to provide correlations with good consistency between estimated and predicted compressive strength.741 - PublicationUse of post-installed screws in the compressive strength assessment of in-situ concreteIn the structural evaluation of existing concrete structures, concrete strength is an important parameter that influences the quality of the overall assessment. Non-destructive tests (NDTs) allows the inspection of larger areas of concrete at lesser cost and time than coring and provides more reliable information than visual inspection. The low reliability of common NDTs in the assessment of compressive strength of concrete limits the use of NDTs in the practical field. A new technique, post-installed screw pullout (PSP) test, based on the modified pullout of post-installed screw, is presented in this paper. The screw transfers the load to the concrete through bearing on the threads. During the complete pullout failure mode, the failure pattern involves local crushing of concrete under the threads. The PSP test was investigated in mortar and concrete to study different factors; compressive strength, presence of aggregates, and the types of aggregate. Mortar was considered to be a homogenous material and thus taken as a baseline for comparing the effect of aggregate type. Experimental studies showed that aggregates play a significant role in the assessment of compressive strength by PSP test, and a better correlation with compressive strength was observed when concretes with different aggregates were analysed separately. In the strength assessment, the degree of variability of the PSP test in terms of R-squared value, standard deviation, coefficient of variation, and RMSE for mortar and concrete with brick chips and lightweight aggregates was found to be low; however concrete with limestone aggregate showed higher variability in the test results. The study confirms that the PSP test is a viable test method with the potential to be reliable and reasonably accurate, yet cost effective; it can also contribute to the reduction of the uncertainty in the assessment of compressive strength of in-situ concrete.
144 - PublicationPost-installed screws for in-situ assessment of mortar strength(2017-06-18)
; ; For capacity evaluation, the structural assessment of existing structures is necessary. Concrete strength is an important parameter for such assessment. Non-destructive tests (NDTs) are used along with the traditional approach of core testing for strength assessment of concrete in existing structures. The low reliability of NDT results leads to uncertainty in assessing concrete strength. A new method of non-destructive testing is presented in this paper with the aim of achieving better reliability and reducing uncertainty in the assessment of mortar strength. This approach is based on a modified pullout of post-installed screw anchors. The technique involves a pushin mechanism for a steel screw inside the mortar where a void underneath the screw is left to allow for the uninterrupted movement of the screw inside the concrete. The failure pattern involves local crushing of concrete between the threads of the screw. This paper investigates the load bearing behaviour of threaded screws installed in cement mortar under compressive loading. The results supports the application of the technique in the assessment of compressive strength of mortar. The main parameters affecting the pushin behaviour are presented and their effects are discussed. It is planned to extend the test program to concrete in the future.525 - PublicationTRUSS, a European Innovative Training Network Dealing with the Challenges of an Aging Infrastructure Network(NDT.net, 2019-04-01)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Inspections and maintenance of infrastructure are expensive. In some cases, overdue or insufficient maintenance/monitoring can lead to an unacceptable risk of collapse and to a tragic failure as the Morandi bridge in Genoa, Italy, on 14th August 2018. An accurate assessment of the safety of a structure is a difficult task due to uncertainties associated with the aging and response of the structure, with the operational and environmental loads, and with their interaction. During the period from 2015 to 2019, the project TRUSS (Training in Reducing Uncertainty in Structural Safety) ITN (Innovative Training Network), funded by the EU H2020 Marie Curie-Skłodowska Action (MSCA) programme, has worked towards improving the structural assessment of buildings, energy, marine, and transport infrastructure. Fourteen Early Stage Researchers (ESRs) have been recruited to carry out related research on new materials, testing methods, improved and more efficient modelling methods and management strategies, and sensor and algorithm development for Structural Health Monitoring (SHM) purposes. This research has been enhanced by an advanced program of scientific and professional training delivered via a collaboration between 6 Universities, 1 research institute and 11 companies from 5 European countries. The high proportion of companies participating in TRUSS ITN has ensured significant industry expertise and has introduced a diverse range of perspectives to the consortium on the activities necessary to do business in the structural safety sector.115 - PublicationTRUSS, a European innovative training network dealing with the challenges of an aging infrastructure network(2018-11-12)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Inspections and maintenance of infrastructure are expensive. In some cases, overdue or insufficient maintenance/monitoring can lead to an unacceptable risk of collapse and to a tragic failure as the Morandi bridge in Genoa, Italy, on 14th August 2018. An accurate assessment of the safety of a structure is a difficult task due to uncertainties associated with the aging and response of the structure, with the operational and environmental loads, and with their interaction. During the period from 2015 to 2019, the project TRUSS (Training in Reducing Uncertainty in Structural Safety) ITN (Innovative Training Network), funded by the EU H2020 Marie Curie-Skłodowska Action (MSCA) programme, has worked towards improving the structural assessment of buildings, energy, marine, and transport infrastructure. Fourteen Early Stage Researchers (ESRs) have been recruited to carry out related research on new materials, testing methods, improved and more efficient modelling methods and management strategies, and sensor and algorithm development for Structural Health Monitoring (SHM) purposes. This research has been enhanced by an advanced program of scientific and professional training delivered via a collaboration between 6 Universities, 1 research institute and 11 companies from 5 European countries. The high proportion of companies participating in TRUSS ITN has ensured significant industry expertise and has introduced a diverse range of perspectives to the consortium on the activities necessary to do business in the structural safety sector.169 - PublicationNonlinear Analysis of Isotropic Slab Bridges under Extreme Traffic Loading(NRC Research Press, 2015-08-11)
; ; ; ; Probabilistic analysis of traffic loading on a bridge traditionally involves an extrapolation from measured or simulated load effects to a characteristic maximum value. In recent years, Long Run Simulation, whereby thousands of years of traffic are simulated, has allowed researchers to gain new insights into the nature of the traffic scenarios that govern at the limit state. For example, mobile cranes and low-loaders, sometimes accompanied by a common articulated truck, have been shown to govern in most cases. In this paper, the extreme loading scenarios identified in the Long Run Simulation are applied to a non-linear, two-dimensional (2D) plate finite element model. For the first time, the loading scenarios that govern in 2D nonlinear analyses are found and compared to those that govern for 2D linear and 1D linear/nonlinear analyses. Results show that, for an isotropic slab, the governing loading scenarios are similar to those that govern in simple one-dimensional (beam) models. Furthermore, there are only slight differences in the critical positions of the vehicles. It is also evident that the load effects causing failure in the 2D linear elastic plate models are significantly lower, i.e. 2D linear elastic analysis is more conservative than both 2D nonlinear and 1D linear/nonlinear.252 - PublicationMeshfree Sequentially Linear Analysis of ConcreteA new, meshfree method employing the node-based, smoothed point interpolation method (NS-PIM) is presented as an alternative to the nonlinear finite-element approach for concrete members. The nonlinear analysis is replaced by sequentially linear analyses (SLA), and a smeared, fixed concrete cracking model was used. A notched concrete beam was employed for validation. Using a crack band width factor of 2.0 and 10-mm nodal spacing, the peak load differed by only 3.5% from experimental results. Overall results were similar to experimental ones, as well as to those published by researchers using finite-element SLA. The approach provides two major advantages over finite-element-based SLA: (1) nodal distortion insensitivity, and (2) nodal spacing insensitivity.
459Scopus© Citations 4 - PublicationFinite element lower bound "yield line" analysis of isotropic slabs using rotation-free elementsA new lower bound finite element method for slab analysis is presented as a practical substitute to full, non-linear, finite element methods that require expert knowledge and long running times. The method provides a general, safe and efficient lower bound solution for the analysis of reinforced concrete slabs up to failure. As it is finite element based, the method is more general than the yield line and strip methods currently in use. Furthermore, its lower bound nature makes it safer than the yield line method. The method uses a rotation-free, plate finite element modified to allow plastic “yield lines” to pass through at any direction. Yield lines are generated at the principal moment directions when the plastic moment capacity is attained. The material is assumed to be elastic perfectly-plastic. Following the general spirit of yield line analysis, the effects of a yield line are projected to the sides of the triangular element and then used to calculate the bending curvatures. The method’s efficiency is achieved by using rotation-free plate elements with a single degree of freedom per node and by the incremental solution that does not require iterations. The method’s accuracy and convergence are assessed by comparing standard cases with known results. In all cases, results were close to the theoretical values with difference of less than 1%. It is also used to solve a practical sized flat slab problem in order to demonstrate the method’s efficiency, convergence, and speed.
12246Scopus© Citations 14