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This research paper reports results of strength development properties of ambient-cured alkali activated binders (AABs) and their reliance on different parameters, such as type of pre-cursor materials & their proportions, type & ratio of activators, and curing age. In this research study sodium silicate (SS) and sodium hydroxide (SH) solutions were used to activate a blend of low-calcium (class F) fly ash (FA) and ground granulated blast furnace slag (GGBFS). A total of 25 AABs mixes with various mix proportions are investigated in this research study. The results indicate that AABs can be manufactured with strength properties similar to ordinary Portland cement concrete (OPC). For further insight into the mechanical property variations of these samples SEM and EDS tests are conducted and their micrographs are presented here. A previously proposed analytical model to predict the compressive stress-strain response of these AABs is also modified in this study to better capture their post peak behaviour.

Polycal Wire rope isolators (PWRIs) have found many applications, especially in naval and aerospace structures. PWRIs are used to isolate individual equipment or complete floating floors against undesirable shocks and vibrations. A PWRI consists of arch shaped wire rope strands connected between circular plates. This architecture results in an isolator with a nonlinear hysteresis behavior capable of providing the necessary damping to dissipate an input energy. In this paper, a complete study of the shear cyclic behavior of PWRIs is presented. Twelve isolators of different geometries were tested in shear mode under different loading rates. The stiffness, energy dissipation, and damping were determined and related to the geometric and mechanical properties of each isolator. To overcome the limitations of existing mathematical models in representing the hysteretic behavior of wire rope isolators, a new model is proposed, in which, the Bouc-Wen-Baber-Noori model of hysteresis was adopted in conjunction with a modulating function. The model is shown to accurately replicate the soft-hardening, symmetric, hysteresis loops.

This paper presents a comprehensive analysis of mathematical models for estimating the shear strength of trapezoidal-corrugated steel webs. The existing database of experimental data on trapezoidal corrugated steel web beams and girders is updated by adding more test results, yielding a total of 144 tests. The three-parameter model, previously developed by the authors based on Richards equation is reduced to a two-parameter improved version based on Hill equation. Both models were found to have, essentially, the same performance when compared against test results of the updated database. Based on the Akaike Information Criterion, the new model was retained. The performance of the improved and previously published models is reviewed and tested against the updated database of test results. It was found that the improved model performed better than the existing models in many aspects. An uncertainty analysis was performed on the proposed model considering both, geometric and material parameters as random variables. Bootstrapping and the Point Estimate Method (PEM) were employed to propagate uncertainty and construct confidence intervals for the normalized shear strength. It was found that, overall, the coefficient of variation of the normalized shear strength increases with the slenderness ratio.

In this paper, we investigate the contribution of Fiber-Reinforced Polymer (FRP) to the load-carrying capacity of shear-strengthened Reinforced Concrete (RC) beams. Specifically, the investigation is focused on the FRP’s contribution in the presence and absence of shear stirrups. To this end, two sets of full-scale RC beam specimens were tested to failure in a simply supported setup. Set 1 consisted of specimens without shear stirrups whereas Set 2 included steel stirrups spaced at 170 mm. One and two layers of FRP discrete strips were bonded to the beams in a U-jacketing configuration. To investigate the contribution of FRP and its interaction with the stirrups, two different locations were considered when bonding the FRP strips: between the stirrups (referred to as Off-beams) and at the same level of the stirrups (referred to as On). Results of the experimental program showed that strengthening the beams with two layers of FRP does not necessarily translate to improved capacity. Furthermore, the location of FRP strips with respect to the location of shear stirrups has an influence on the beam’s overall behavior, especially its displacement ductility. This is an important parameter to consider to avoid premature failure of RC members. Test results were then used to assess the performance and accuracy of the predictions of ACI PRC-440.2-17 and fib-TG9.3. Both design codes were found to be conservative with an average prediction-to-test ratio of 0.7.

The aim and objective of this research project was to develop and investigate a rapid method of strengthening the Unreinforced Masonry walls (URM) for out-of-plane action. A total of 12 URM walls, built inside a precast fiber reinforced concrete boundary frame, were strengthened with a cement based concrete mix with or without steel reinforcement. The concrete mixes included Fiber Reinforced Concrete (FRC) (two dosage of fibers (4.6 & 6.0 kg/m3)), Engineered Cementitious Composite (ECC), and plain concrete shotcrete (PLS). Two out of 12 walls were strengthened with steel mesh reinforced shotcrete (MRS) such that a steel mesh was attached to the surface of the walls prior to spraying with concrete. In addition, one wall was plastered only with conventional cement mortar (RF) to serve as a reference. The strengthening materials were applied to both sides of URM walls using shotcrete technology. The walls were exposed to the air pressure of an actual blast from 10 kg of TNT explosive at a 1 m stand of distance. It was found that strengthening the walls with the proposed method significantly improved the out-of-plane behaviour of the URM walls. The results showed that the walls strengthened with ECCS exhibited the least damage followed by FRS-6, FRS-4.6, MRS, and PLS. Whereas, the reference wall (RF) did not survive the blast induced pressure and fully shattered into small pieces.

Les modèles macro-éléments non linéaires ont été développés pour simuler le comportement des appuis parasismiques. Cependant, ces modèles négligent certains aspects du comportement des isolateurs sismiques. Dans cet article, un modèle de macro éléments pour les appuis parasismique avec un barreau de plomb a été développé. Le modèle proposé comprend des effets de charge axiale et tient compte de grandes déplacements. La non-linéarité du modèle est représentée par le modèle d'hystérésis de Bouc-Wen. La réponse obtenue en utilisant le modèle numérique s'avère être en bon accord avec le comportement observé dans les résultats d'essai sur des appuis parasismiques avec barreau de plomb. La deuxième partie de cet article est d'appliquer le modèle proposé sur un pont à pile marteau avec isolation sismique sismique. Une augmentation de la charge axiale a été effectuée pour étudier l'influence de la charge axiale sur la réponse cyclique de la du pont. Le comportement du pont est caractérisé par une boucle d'hystérésis dont l'inclinaison et la surface dépendent de l'amplitude de la charge axiale. La rigidité post élastique diminue avec l'augmentation des charges axiales. Cependant, la dissipation d'énergie de l'isolateur, représentée par la surface de la boucle d'hystérésis, a augmenté de façon significative avec l'augmentation de la charge axiale., Academic Journal of Civil Engineering, Vol 35 No 1 (2017): Special Issue - RUGC 2017 Nantes

Steel beams and girders with corrugated webs have found many applications, especially in industrial structures and bridges. This choice is backed by the many features, this class of structural members can offer, such as the high load carrying capacity before failure due to the web geometry. The failure of a corrugated web may occur due to material yielding or due to geometrical buckling. Three modes of shear buckling are typical for corrugated webs: local, global, and interactive shear buckling. In this paper, the shear failure mechanisms of trapezoidal corrugated webs are investigated. Nine, shear-critical, corrugated web panels were tested until failure. The new test results confirmed a previous observation that all panels achieved a residual strength of about half of the buckling shear strength, regardless of their geometry and most of them reached yielding before buckling takes place. Since the shear strength of corrugated webs is a function of several material and geometric parameters, a comprehensive global, density-based, sensitivity analysis was performed to estimate the relative contribution of each parameter to the behavior of shear strength through a previously developed mathematical model. The analysis revealed that the length of the flat folds is the most influential parameter on the shear strength of corrugated webs, while the modulus of elasticity is the least influential. The study was extended to determine ranges on which each parameter is non-influential.

This paper demonstrates the evaluation of the energy dissipation capacity of a steel damper made from mild steel plates through performing a finite element analysis simulating cyclic loading. Results aimed to obtain the damper characteristics incorporated in retrofitting frames to increase their seismic resistance and energy dissipation. The analysis has well captured the damper energy dissipation capacity and the effective stiffness. Results showed that stresses were concentrated on the diaphragm plate since it is the weakest part of the damper and where the failure is expected to occur. Also, the diaphragm plate was the first segment of the damper to yield and enter the plastic ranges.

The main objective of this paper was to study the concrete-to-concrete shear friction behavior under cyclic loading and different test rates. Eight dynamic push-pull tests were performed on concrete specimens with as-cast surface roughness type applying four different test rates. The test results include the hysteresis loops of the friction force-displacement relations. It is concluded that the dynamic coefficient of friction decreased with the increased test rate. This reduction in the dynamic coefficient of friction should be considered in the design of structural elements under cyclic or dynamic loading.

The strength reduction factors (ϕ) adopted by ACI-440.1R-15 standard code for the flexure design of Fiber Reinforced Polymers Reinforced Concrete (FRP-RC) beams are calibrated in this study. The code calibration process aims to achieve a particular target reliability index (βT) for the selected FRP-RC rectangular beams. An extensive experimental database is collected and used in the calibration process of the resistance factors. It was found that the calibrated ϕ led to a more economical and less conservative design while satisfying the safety requirements imposed by the design code. To meet the βT, a recommended value of ϕ, is found to be 0.70 for cast-in-situ beams failing in compression and 0.65 for tension-controlled cast-in-situ beams. Thus, the proposed values are slightly greater than comparable factors adopted by the ACI code of 0.65 for compressioncontrolled and 0.55 for tension-controlled cast-in-situ beams.

Steel corrugated webs are vertical and lightweight plates responsible for carrying large in-plane loads before buckling. Three modes of shear failure are typical for these elements: local, global, and interactive shear buckling. In this paper, previously published analytical models for the estimation of the shear strength of trapezoidal corrugated webs are summarized, and a new model is developed. The proposed model takes into account the interaction between the modes of shear buckling. Twelve shear-critical corrugated web steel beams (CWSBs) were manufactured and tested to failure. The results were added to update the existing database, resulting in 125 test results, which were then used to compare the performance of developed and existing models. The new model is shown to be more accurate than previously published models for estimating the shear strength of corrugated steel webs, allowing for more economic designs.

This paper presents results from restrained shrinkage tests to assess the effectiveness of fly ash on cracking and relaxation behavior of Self Compacting Concrete (SCC). The effects of fly ash (FA) proportion, degree of restraint and curing regime are specifically addressed. The results show that curing condition and degree of restraint play a significant role on the effectiveness of FA on the cracking and relaxation behavior of SCC mixes. It was also found that addition of FA improves the cracking resistance and relaxation behavior of SCC relative to the control. The results further suggest that FA can replace cement by up to 50% for low degree of restraint, and up to 35% for high degree of restraint with significant improvement in cracking resistance, provided that appropriate moist curing is adopted. The normalized results presented may also prove to be an important tool in devising mixes best suited for onsite conditions.

Due to their lightweight and superior load carrying capacity, corrugated web steel beams (CWSBs) have gained popularity in the last few decades. CWSBs are known to fail at much higher loads compared to stiffened flat web beams. To understand their shear response, a series of three-point load tests were performed on five shear-critical trapezoidal corrugated web beams. The test results confirmed the existence of the three shear buckling modes of failure: local, global, and interactive. In addition, all tested beams were observed to have a residual strength that is about half of their ultimate load carrying capacity regardless of the shear buckling mode. Results of the nonlinear finite element analysis showed that the shear stress is at its maximum and uniformly distributed throughout the web until buckling, afterwards, it decreases and its distribution is uneven while the entire resistance is provided by the increased tensile stress. Furthermore, stocky corrugated webs were shown to reach shear yield strength. Comparison between existing analytical models for the estimation of shear strength against test data showed that EN-1993-1-5 is accurate and conservative enough for an economic design.

The restrained shrinkage cracking and relaxation behavior of Self Compacting Concrete (SCC) containing different proportions of ground granulated blast furnace slag (GGBS) is studied. The effects of GGBS proportion, degree of restraint and curing regime are specifically addressed. The results show that GGBS improves the cracking resistance and relaxation behavior of SCC relative to control. Curing condition and degree of restraint play a significant role on the cracking and relaxation behavior of SCC. The results revealed that GGBS can replace cement by up to 70% and 50% for low and high degree of restraint, respectively, provided moist curing is adopted.

Methods for the seismic demands evaluation of structures require iterative procedures. Many studies dealt with the development of different inelastic spectra with the aim to simplify the evaluation of inelastic deformations and performance of structures. Recently, the concept of inelastic spectra has been adopted in the global scheme of the Performance-Based Seismic Design (PBSD) through Capacity-Spectrum Method (CSM). For instance, the Modal Pushover Analysis (MPA) has been proved to provide accurate results for inelastic buildings to a similar degree of accuracy than the Response Spectrum Analysis (RSA) in estimating peak response for elastic buildings. In this paper, a simplified nonlinear procedure for evaluation of the seismic demand of structures is proposed with its applicability to multi-degree-of-freedom (MDOF) systems. The basic concept is to write the equation of motion of (MDOF) system into series of normal modes based on an inelastic modal decomposition in terms of ductility factor. The accuracy of the proposed procedure is verified against the Nonlinear Time History Analysis (NL-THA) results and Uncoupled Modal Response History Analysis (UMRHA) of a 9-story steel building subjected to El-Centro 1940 (N/S) as a first application. The comparison shows that the new theoretical approach is capable to provide accurate peak response with those obtained when using the NL-THA analysis. After that, a simplified nonlinear spectral analysis is proposed and illustrated by examples in order to describe inelastic response spectra and to relate it to the capacity curve (Pushover curve) by a new parameter of control, called normalized yield strength coefficient (). In the second application, the proposed procedure is verified against the NL-THA analysis results of two buildings for 80 selected real ground motions.

This research study is conducted to investigate the flexural behaviour of steel fiber reinforced concrete (SFRC) prisms incorporating different types and volume fractions of steel fibers, various grades of concrete, and different specimen depths, all tested under displacement control mode using four-point loading configuration. Two types of steel fibers (hooked end and straight) were incorporated into the concrete mixes at two different dosages (1% and 2%). Concrete mixes with compressive strengths of 40, 50, and 70 MPa were used to cast the samples. Specimen depth was also among the test variables, where prisms of depth 100, 150 and 200 mm were tested to study the size effect on the flexural behaviour of SFRC. Test results indicated that for the straight-end steel fibers, the increase in the fiber volume fraction from 1 to 2% had a noticeable effect on both flexural strength (or Modulus of Rupture, MOR) and associated prism mid-span deflection. However, for the hooked end steel fibers, there was only a limited increase in the same measured values due to reduced workability of the SFRC fresh mix. The test results also have shown that the increase in the concrete compressive strength had only a modest effect on the average MOR value, but a noticeable effect on average mid-span deflection at peak load. The latter was attributed to the relatively long length and the hooked end geometry of the steel fibers. Finally, test results revealed that specimen depth had an impact on the measured flexural strength, where increase in specimen depth was associated with reduced MOR values, a phenomenon that is commonly referred to in the literature as size effect.

The available literature on the shear strength of corrugated web steel beams (CWSBs) includes a wealth of methods that specify the nominal buckling capacity, but with no consideration of reliability-based design. In the framework of Load and Resistance Factor Design (LRFD) codes, the design of steel members requires load factors to amplify the load effect and a resistance factor to scale-down the resistance based on a target reliability index. Therefore, for full integration of the shear design of CWSBs into the current design codes, resistance factors must be developed and calibrated for use within the LRFD context. This is crucial since the use of existing resistance factors that were specifically developed for welded plate girders for the design of CWSBs may lead to a level of safety that is not consistent with the philosophy of the code. Using a curated database of test results, the present paper attempts to address the lack of a reliability-based design method specific to CWSBs. Two North American design standards were selected in this study, namely, AISC 360 and CSA-S16. A series of reliability analyses are performed first to verify the consistency of reliability indices for welded plate girders designed following the two standards. Then, a probabilistic-based approach is used to calibrate the resistance factors for the shear limit state of CWSBs in accordance with the AISC 360 and CSA-S16 considering dead, live, wind, and snow loads. Finally, an iterative step-by-step procedure is then developed within the LRFD framework to aid in the design of corrugated webs to resist shear loads at ultimate. Findings of the study showed that the current AISC 360 resistance factor for welded plate girders when used for the shear design for CWSB, does not yield a safety level that is consistent with the target reliability; thus, a new factor equal to 0.85 is proposed. For CSA-S16, the current resistance factor of 0.90 for welded plate girders is found to be appropriate for corrugated web steel beams.

Despite their successful use in many bridges across several countries around the world, corrugated web steel girders (CWSGs) haven't been yet recognized formally by mainstream design codes and standards. CWSGs can be an economical alternative to conventional welded plate girders; they can achieve higher shear strengths with lesser material usage. Corrugated webs have been demonstrated to carry about half of their ultimate shear strength after buckling, which is an important reserve strength to overcome sudden collapses of bridge structures. The current design practice combines the latest research in the field with engineering judgment with no regard for reliability-based design. In light of the new developments in the field of bridge design and reliability analysis techniques, this paper revisits first the reliability of welded plate girders in shear and verifies their target reliability index and the corresponding resistance factor as per AASHTO LRFD. Then, and in an attempt to prepare the inclusion of CWSGs shear design in AASHTO LRFD, a probabilistic-based calibration procedure is applied to calibrate the resistance factor for bridges having a range of span lengths and girder spacings, with consideration of different average daily truck traffic. A series of sensitivity analyses were carried out in order to quantify the relative contribution of each design parameter to the overall reliability of CWSGs in shear. The findings of this study suggest that, for CWSGs in shear, a resistance factor of 0.95 is appropriate to ensure a reliability level that is consistently close to the target. The sensitivity analysis showed that the web thickness, web depth, and the yield strength of the web's steel material are the most influential parameters on the reliability index of CWSGs.

Seismic hazard and geotechnical microzonation maps of urban communities make it conceivable to describe potential seismic zones that should be considered when planning new structures or retrofitting existing ones. This study looked at a local site-specific ground response analysis, which is an important step in estimating the effects of earthquakes. The soil data from 200 boreholes up to 30 m depth were collected and analyzed using SHAKE2000 and NovoLiq in order to develop local site amplification and liquefaction potential maps for the city of Sharjah. In addition, Geographical Information System (GIS) was utilized to create amplification and liquefaction potentials maps at different areas in Sharjah. These maps show zones of high vulnerability earthquake risk used for earthquake-resistant design of structures. The city of Sharjah was divided into areas, according to the amplification factor, which ranged from 1.44 to 1.83. A high amplification factor was found near the central region of the city, while the rest of the city lies in low amplification potential and relatively low seismic risk. Finally, liquefaction risk of Sharjah estimated and expressed in terms of safety factor. The low values of the safety factors against liquefaction were found in the north, northeastern, and southeastern portions of the city. Higher values were found in central and toward south central parts of the studied area. In these parts, the higher safety factor indicates low liquefaction potential of the soil and relatively low seismic risk.

This research investigates the fresh state properties and hardened state properties of medium strength, self-compacting concrete incorporating a high volume of class F fly ash as a partial replacement to cement and blended fine aggregates while maintaining satisfactory properties of SCC. The properties of self-compaction investigated are: slump flow, J-ring, L-box, Vfunnel, sieve stability and Visual Stability Index tests. Those of hardened concrete include compressive strength, splitting tensile strength, complete immersion water absorption, apparent volume of permeable voids, sorptivity, and rapid chloride ion penetration tests. The experiments on fresh state properties investigate the filling ability, the passing ability and the segregation resistance of concrete. The results show that fly ash improves workability and decreases the compressive strength as well as splitting tensile strength. Fly ash based SCC shows better resistance to water absorption, apparent volume of permeable voids, sorptivity, and chloride penetration than the control mix.

We present an enhancement to the existing elliptical leaf spring (ELS) for improved damping and energy dissipation capabilities. The ELS consists of a high tensile stainless steel elliptical leaf spring with polymer or rubber compound. This device is conceived as a shock and vibration isolator for equipment and lightweight structures. The enhancement to the ELS consists of a lead spring plugged vertically between the leaves (referred to as lead-rubber elliptical leaf spring (LRELS)). The lead is shown to produce hysteretic damping under plastic deformations. The LRELS isolator is shown to exhibit nonlinear hysteretic behavior. In both horizontal directions, the LRELS showed symmetrical rate independent behavior but undergoes stiffening behavior under large displacements. However, in the vertical direction, the LRELS behavior is asymmetric, exhibiting softening behavior in compression and stiffening behavior in tension. Mathematical models based on the Bouc-Wen model, describing the hysteretic behavior of the proposed isolator, are developed and numerically calibrated using a series of finite element analyses. The LRELS is found to be effective in the in-plane and vertical directions. The improved damping and energy dissipation of the LRELS is provided from the hysteretic damping of the lead spring.

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This paper presents the results of an experimental investigation on the behavior of Reinforced Concrete (RC) beams repaired and strengthened using Externally Bonded Carbon Fiber Reinforced Polymer (EB-CFRP). The experimental program involved 19 static tests on 16 simply supported rectangular RC beams in which seven were tested without CFRP and 12 were wrapped with one or two layers of CFRP. Out of the 12 beams, six were first tested to failure, repaired with epoxy, then wrapped with CFRP sheets before the second and final test. The remaining six were wrapped with CFRP, while virgin, before testing. Among the objectives of this study was the analysis of the effectiveness of EB-CFRP as a strengthening method for shear strengthening of damaged RC beams and the identification of interaction between conventional shear reinforcement and the EB-CFRP strips. Analysis of test results suggests that the EB-CFRP strengthening of damaged beams repaired using epoxy injection not only helps the beams to recover but also significantly increase their shear capacity. Moreover, one layer of CFRP discrete strips improved the overall capacity of the shear-deficient beams by more than 60% and an additional layer further increased the shear capacity by another 30%. The results also confirmed that an interaction exists between steel stirrups and EB-CFRP strips when carrying the applied load. For instance, test results demonstrated that the contribution of CFRP in shear strength is affected by the quantity of steel stirrups. Finally, when compared to test results, the ACI and fib formula provided reasonable estimation of the additional shear strength contributed by the EB-CFRP discrete strips, except for the beams with moderate ratio of steel stirrups. However, Chen et al. model better estimated the EB-CFRP contribution to the shear capacity of RC beams with moderate ratio of steel stirrups.

This paper presents results from an ongoing research that is intended to study the behavior of URM walls for out-of-plane action. The effect of fiber reinforced shotcrete (FRS) as a strengthening method for the URM walls is examined. Eight URM walls were built inside a precast reinforced concrete boundary frame and strengthened with cement-based shotcrete mixes reinforced with different types of fibers. The masonry wall is 1.2x 1.2 m, and the masonry units were hollow concrete blocks (10 x 20 x 40 cm). Conventional fiber reinforced concrete (FRC) and engineered cementitious composite (ECC) were used as the strengthening layers sprayed on the surface of masonry walls. Control walls with plain shotcrete and conventional plastering mortar were also examined. Synthetic macro-fibers at dosage rate of 6 kg/m3 in FRC mix and Polyethylene micro-fibers at a dosage rate of 16 kg/m3 in ECC mix were considered in this study. The walls were placed in a carefully designed set up and tested under static central load using a hydraulic actuator with a capacity of 500 kN. The parameters recorded during testing were the applied load and out-of-plane displacement of the walls. Cracking pattern and failure modes were also monitored. The reported test results demonstrate that FRC and ECC mixes can significantly increase the out of plane strength and ductility of the URM walls.

This paper presents preliminary results of an extensive experimental program on the behavior of high-strength (HS) reinforced concrete (RC) T-beams strengthened with Carbon Fiber Reinforced Polymer (CFRP) sheets. The test program involves the fabrication and testing of 56 RC beams and many objectives to achieve. The objective of this paper is to investigate the effect of the number of CFRP layers on the shear strength of HS RC beams. To this end, three full-scale specimens were prepared and instrumented with displacement transducers and strain gauges: one control beam, one single-layer of CFRP sheets, and one double-layer of CFRP sheets. All beams were simply supported and subjected to a monotonically increasing load until failure. Preliminary results showed that in the absence of transverse steel reinforcements, the number of CFRP layers does not affect the ultimate strength of the HSC beams.