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This paper investigated the impact of room temperature, cyclic ponding salt water (15%), hot water of 65°C, and rapid freeze and thaw cycles for three years on the flexural behavior of reinforced concrete beams strengthened with different configuration of CFRP composites. Totally sixteen RC beams were casted and tested as simply supported load as four point loading with a shear span to a depth ratio of 2.25. The investigated parameters includes mode of failure, ultimate load and corresponding deflection, yielding load and corresponding deflection, stiffness, steel strain, concrete strain, and CFRP strain. Based on tested results, the environment conditions had no effect (No separation or debonding) on the bond strength between CFRP composites and tension side of concrete. After applying the load, the inelastic deformation was shown in concrete which leads to yielding of main steel reinforcement and then compression failure of tested beams. In addition, the strengthened beams indicated a reduction in flexural stiffness and enhancement in the ductility of the member through. Finally, the increasing of number of layers (CFRP bonded area) had a strong impact on concrete by shelter concrete from environmental consequences and undesirable effect on the CFRP-concrete bond performance.

Optimizing ultra-high-performance concrete (UHPC) mixture design requires investigating the effect of varying the materials constituents and curing temperature on its mechanical characteristics. Therefore, a comprehensive experimental program was conducted that included studying the effect of varying the materials constituents on the mechanical and fracture mechanics properties of UHPC. The experimental program included water-cementitious materials ratio (w/cm), cementitious combination, amount of ground silica, aggregate type, maximum aggregate size, steel fiber content, and curing temperature. Higher compressive strength was achieved with higher curing temperature. The use of Class C fly ash with up to 20% replacement to cement by weight was found to be beneficial in increasing the compressive strength at later age (28 and 90 days). Moreover, reducing the ground silica content from 25% (control) to 10% as a partial replacement to fine sand and the silica fume from 25% to 20% can still yield more than 150 MPa (21.7 ksi) compressive strength at 28 days. In addition, the inclusion of steel fibers up to 2% by volume was found to significantly improve the compressive strength, ultimate flexural strength, flexure toughness, and the fracture parameters of UHPC. Keywords: concrete materials; curing; flexure toughness; fracture mechanics; shrinkage; steel fibers; strength; ultra-high-performance concrete (UHPC).

The flexural properties of eight 200 x 300 mm (8 x 12 in.) concrete beams reinforced with basalt fiber-reinforced polymer (BFRP) reinforcing bars were investigated. The beams were reinforced with four different sizes of BFRP (10, 13, 16, and 25 mm). The flexural reinforcement ratios [[rho].sub.f] ranged from 1.43 to 10.70 times the balanced ratio [[rho].sub.fb]. The beams were divided into three categories with low, moderate, and high [[rho].sub.f]. As expected, all the beams failed by crushing of the concrete in the top compression fiber. Higher [[rho].sub.f]/[[rho].sub.fb], to some extent, has a better effect on reducing the deflection than increasing the beam's ultimate strength. The strain compatibility equation per ACI 440.1R-06 was conservative in predicting the ultimate flexural strain in the BFRP bars and the ultimate moment capacity. The effective moment of inertia ([I.sub.e]) prediction model recommended by ACI 440.1R was the least conservative among other models when compared with the experimental [I.sub.e]. Keywords: basalt; beam; deflection; fiber-reinforced polymers (FRPs); flexure; reinforcement; serviceability.

Many countries worldwide face a common problem with the aging bridge infrastructure that is being demanded to carry increasing loads. With the cost and the difficulties associated with replacing and rehabilitating these bridges, it is necessary to make the most efficient use of the existing infrastructure. Proof load testing (PLT) proved to be a reliable non-destructive method to assess the bridge and reflect its actual behavior, especially the old bridges. The advancement on the Internet of Things (IoT) technology concerning sensors and data acquisition systems for sensing, collecting, and storing the data in conjunction with Finite Element Modeling has resulted in combining analytical models and field test results for better assessment of the bridge condition. It would be insightful to combine the field-testing data with Finite Element Modeling to optimize the outcomes from proof load tests. In this paper, the case of the I-39 Kishwaukee, a five-span twin post-tensioned segmental concrete box girder bridge, has been studied. Kishwaukee bridge was built in 1970. Several retrofits were carried out on the structure to solve the cracks and slippage at the shear key between the pier segment and the adjacent cantilever segment caused by non-hardened epoxy at the joint during the time of construction. In 2006, The Illinois Department of Transportation investigates the structural behavior of the bridge and determined that the crack growth along the webs is caused by principal tensile stresses higher than the code limits. Using the FEA, the model shows an estimated permanent strain of 85 µɛ caused by the dead load only at the shear key. This strain added to the strain caused by the HS20 truck live load led to a total strain of 180 µɛ higher than the strain corresponding to the modulus of rupture of the concrete (135 µɛ). A total estimated deflection of 3.84 in. at midspan of Span #3 caused by HS20 truck live load exceeded the AASHTO allowable limit for deflection (3.74 in). Since the bridge was deficient, IDOT decided to strengthen the structure using four–12 strands, 15 mm external post-tensioning tendons placed inside the box girders to reduce the shear forces acting across the webs. This paper illustrates a proof of four different trucks loading weights of 76 tons (167 k), 90 tons (200 k), 122 tons (268 k), and 136 tons (300 k) conducted on the bridge. Nine testing scenarios were successfully completed with a maximum of two testing trucks of approximately 136 tons (300 k). The data obtained from the field test (Measured strains near the pier, where shear and negative moment are critical, and at midspan, where the positive moment is crucial, and measured deflection profiles) were used to optimize a non-linear finite element model for the bridge. This paper provides a comprehensive guide on how to conduct load rating assessments based on the AASHTO MBE method for PLT. It outlines a step-by-step procedure for conducting field operations, implementing instrumentation, and interpreting test results. The data obtained from the field test are used to develop a Finite Element Model showing the impact of the recently introduced external post-tensioning tendons on the structural performance of the bridge. In conjunction with the FEA, this research demonstrated that the rehabilitation of Kishwaukee I-39 bridge using the post-tensioning system reduced the deflection by 88.72%, and minimized the principal tensile strain of the shear key by 80µɛ. Based on these findings, this paper provided a significant allowance for accommodating future traffic load increases on the Kishwaukee I-39 River bridge.

The questions raised about bridge performance are carried out by conducting physical bridge load testing and rating. The outcomes of bridge load testing are widely used to ensure bridge safety for the public when theoretical analysis cannot provide a sufficient conclusion of in-service performance. The research illustrates the load ratings and shear assessment of a 1976-built I-39 Kishwaukee bridge over the Kishwaukee River in Winnebago County, District 1, Illinois. Load ratings of the Kishwaukee twin post-tensioned concrete box girder bridges are governed mainly by the shear stresses located near the piers in combination with visible shear cracks exhibited at the joints around the shear key due to the inception of the cracks at the time of construction in single key joints. Proof of four different trucks loading weights of 76 tons (167 k), 90 tons (200 k), 122 tons (268 k), and 136 tons (300 k) were conducted on the bridge. Nine testing scenarios were successfully completed with a maximum of two testing trucks of approximately 136 tons (300 k). Half of the bridge was instrumented using vibrating wire strain gauges to measure the strains near the pier, where shear and negative moment are critical, and at midspan, where the positive moment is crucial. Furthermore, crackmeters were placed along the cracks near the shear key region to measure the crack opening during testing. Linear variable differential transducers (LVDTs) were placed at the critical Sect. (0.40L) of Span #5 to measure the deflection. The modified compression field theory (MCFT) is used to calculate the shear capacity along the joints considering the contributions of vertical and horizontal reinforcing steel, the prestressing Dywidag bars, and the effect of the external post-tension tendons. This paper illustrates a detailed procedure for Kishwaukee Bridge load rating, field operation, instrumentation, and interpretation of the test results to determine the bridge load rating based on the 2018 AASHTO Manual for Bridge Evaluation. Findings from this study demonstrated that there is no crack slippage across the web-cracked section, and the bridge’s concrete shear capacity remains strong and contributes to the bridge’s total shear capacity. This study also showed that the shear capacity of the bridge is 1.8 times stronger than the total applied shear force, concluding that the Kishwaukee I-39 bridge remains safe for future traffic load increases or higher truck loads.

Replacing cement with limestone and inorganic process additions (IPAs) and increasing the insoluble residue (IR) can aid in reducing the CO2 emission. This paper investigates the effect of adding IPA and increasing IR on the diffusivity characteristics of concrete. Also, the effect of replacing cement with supplementary cementitious materials while batching them with two sand types was demonstrated. To show the effect of these materials, the chloride diffusion test was conducted on 26 concrete mixtures with different proportions that were salt ponded for 90, 180, and 360 days. The IPA addition and increase in IR did not show any notable influence on concrete diffusivity. On the basis of the experimental results, a diffusion model with time-dependent surface chloride and diffusion coefficient was developed. The proposed model was compared with existing service-life prediction software and models, and showed promising results, while the current equations adopted by the software were very conservative.

The use of sand-lightweight concrete made with expanded shale aggregate has become prevalent in recent years. Sand-lightweight concrete is approximately 20% lighter than its normalweight counterpart based on the incorporation of coarse lightweight aggregate. Earthquake forces applied to a building structure are directly proportional to its mass, so the potential for better seismic performance is clear. However, concrete made with lightweight aggregate is more brittle in nature than normalweight concrete and, as such, is less ductile. This study focused on determining the behavior of reinforced sand-lightweight concrete beam-column joints of moment frame buildings by subjecting six half-scale test specimens to quasi-static cyclical loading that gave an indication of their ductility in a seismic event. This study found that, if designed and detailed in accordance with current code provisions and if joint shear stress is kept within a reasonable limit, high-strength, sand-lightweight beam-column joints can perform as well as similarly-built normalweight concrete specimens.

Development of a prefabricated, full-depth, precast concrete bridge deck construction system provides a very effective and economic design concept, and can be implemented for the rehabilitation of existing highway bridges as well as new bridge construction. The precast concrete panels must be post-tensioned in the longitudinal direction to provide continuity and to secure tightness in the transverse joints between the adjacent panels, thus rendering zero tension stresses in the precast deck system under all loads taking into account the long-term effects of concrete shrinkage and creep. The investigation entails a detailed evaluation of the full-depth system components under loading to verify the following concerns about the system: 1 serviceability and functionality of the precast concrete deck slab panels; 2 behavior of the transverse joints; 3 behavior of the shear connectors; and 4 effect and adequacy of the longitudinal post-tensioning on the behavior of transverse joints in the positive and negative moment regions.

This paper presents an experimental investigation on the influence of microstructural parameters, such as aggregate size, and macroscopic parameters, such as specimen dimensions, on brittle fracture. Maximum aggregate size was used as a representative parameter of aggregate distribution in agreement with ASTM C 136 standards. Six groups of geometrically similar concrete specimens with various dimensions and aggregate sizes were prepared. Similarity of the specimens was strictly maintained by scaling the specimen dimensions from one group to another by a factor of two starting from a specimen size of (width × total depth × thickness) 105×105×12.5 mm to 1680×1680×200 mm. Two separate sets of removable pre-cast notches were designed to determine the effect of initial notch size. A considerable effort was devoted to the design of the loading fixture to have a reproducible crack initiation and controlled crack growth. Several loading fixtures were evaluated prior to selection of the one used in the experimental program. Quasi-static splitting cyclic loading in edge cleavage configuration was applied. A servo-hydraulic Instron machine was used for testing. The fracture process was monitored by optical and acoustic imaging techniques. Three forms of comparisons of the test results with respect to the specimen and aggregate sizes were adopted. The first corresponded to the various specimen sizes cast with the same maximum aggregate size. The second comparison was based on the geometrically identical specimens cast with various maximum aggregate sizes. The third form of comparison dealt with complete geometrical similarity, i.e., all dimensionless geometrical characteristics including specimen thickness to maximum aggregate size ratio were identical. Results from this study indicated that as the specimen size decreases, the envelope becomes larger within the first and third forms of comparison. In the second form of comparison, i.e., geometrically identical specimens cast with various maximum aggregate sizes, the area under the envelope was greater as the maximum aggregate size increased. The existence of a trend in dimensionless critical load-CMOD envelopes despite the apparent geometrical and physical similarity of the test conditions is the direct indication of a scale effect, i.e., the modified fracture energy, indicates the existence of a strong scale effect: increases with the specimen dimensions as well as maximum aggregate size.

This paper presents an analysis of the extensive experimental program aimed at assessing the influence of maximum aggregate size and specimen size on the fracture properties of concrete. Concrete specimens used were prepared with varying aggregate sizes of 4.75, 9.5, 19, 38, and 76 mm. Approximately 250 specimens varying in dimension and maximum aggregate size were tested to accomplish the objectives of the study. Every specimen was subjected to the quasi-static cyclic loading at a rate of 0.125 mm/min (0.005 in./min) leading to a controlled crack growth. The test results were presented in the form of load-crack mouth opening displacement curves, compliance data, surface measured crack length and crack trajectories as well as calculated crack length, critical energy release rate, and fracture toughness (G1). There is a well pronounced general trend observed: G1 increases with crack length (R-curve behavior). For geometrically similar specimens, where the shape and all dimensionless parameters are the same, the R-curve for the larger specimens is noticeably higher than that for the smaller ones. For a fixed specimen size, G1 increases with an increase in the aggregate size (fracture surface roughness). For the same maximum aggregate size specimens, the apparent toughness increases with specimen size. It was clear that the rate of increase in G1, with respect to an increase of the dimensionless crack length (the crack length normalized by the specimen width), increases with both specimen size and maximum aggregate size increase. The crack trajectory deviates from the rectilinear path more in the specimens with larger aggregate sizes. Fracture surfaces in concrete with larger aggregate size exhibit higher roughness than that for smaller aggregate sizes. For completely similar specimens, the crack tortuosity is greater for the larger size specimens. The crack path is random, i.e., there are no two identical specimens that exhibit the same fracture path, however, there are distinct and well reproducible statistical features of crack trajectories in similar specimens. Bridging and other forms of crack face interactions that are the most probable causes of high toughness, were more pronounced in the specimens with larger maximum size aggregates.