FRP Systems in Shear Strengthening of Reinforced Concrete Structures

AbstractDue to their lightweight, high tensile strength, and ease to install on irregular surfaces, the use of FRP systems for the repair and strengthening of reinforced concrete structures has become an accepted practice within civil engineering community. Extensive research has been conducted on structural members to identify the improvement in their flexural and axial capacity due to FRP strengthening. However, the analytical and experimental studies on shear strengthening with FRP systems are limited. Currently, there is no widely accepted guideline available for the design of concrete structures strengthened in shear using externally bonded FRP systems. Keeping in mind the fact that the use of these strengthening methods has been hindered mostly due to lack of comprehensive design provisions, the available guidelines/specifications are reviewed and the factors that need further investigation are identified. To improve the understanding of the general mechanisms of shear strengthening techniques with externally bonded FRP systems, suggestions for further research effort are itemized and recommendations for an improved guideline are set forth

The Influence of Deformability of Horizontal Diaphragms in the Distribution of Seismic Loads to Bracing Elements in Rectangular Buildings

The operations of a floor, as a significant structural element, have an influence on the stability of the structure when it acts as a horizontal diaphragm. In this study, the in-plane deformability of rectangular floors of single story buildings is examined under the effects of horizontal seismic actions. Therefore, the effects of parameters influencing the behavior of the floor such as size opening and their location, position of shear walls, span-to-depth ratio, and materials constituting the floor were studied. Results suggest that a diaphragm will behave in a flexible manner whether it is classified as rigid or flexible. However, a small opening in the floor can change the behavior of a diaphragm assumed rigid and make it behave like a flexible diaphragm. Additionally, flexible diaphragms can distribute horizontal seismic shear forces to vertical resisting elements due to the relative rigidity of the shear wall. These results are in contradiction with seismic codes such as ASCE/SEI 7-10 [1], FEMA 356 [2], and Eurocode 8[3], further the size of opening that make flexible diaphragm behave like rigid diaphragm was suggested by formula. For the building with a shear wall, the classification of the diaphragm in seismic codes such ASCE is not accurate enough and they need to reform with taking into consideration the location of the opening in the floor

The Influence of Deformability of Horizontal Diaphragms in the Distribution of Seismic Loads to Bracing Elements in Rectangular Buildings

The operations of a floor, as a significant structural element, have an influence on the stability of the structure when it acts as a horizontal diaphragm. In this study, the in-plane deformability of rectangular floors of single story buildings is examined under the effects of horizontal seismic actions. Therefore, the effects of parameters influencing the behavior of the floor such as size opening and their location, position of shear walls, span-to-depth ratio, and materials constituting the floor were studied. Results suggest that a diaphragm will behave in a flexible manner whether it is classified as rigid or flexible. However, a small opening in the floor can change the behavior of a diaphragm assumed rigid and make it behave like a flexible diaphragm. Additionally, flexible diaphragms can distribute horizontal seismic shear forces to vertical resisting elements due to the relative rigidity of the shear wall. These results are in contradiction with seismic codes such as ASCE/SEI 7-10 [1], FEMA 356 [2], and Eurocode 8[3], further the size of opening that make flexible diaphragm behave like rigid diaphragm was suggested by formula. For the building with a shear wall, the classification of the diaphragm in seismic codes such ASCE is not accurate enough and they need to reform with taking into consideration the location of the opening in the floor

The Influence of Deformability of Horizontal Diaphragms in the Distribution of Seismic Loads to Bracing Elements in Rectangular Buildings

The operations of a floor, as a significant structural element, have an influence on the stability of the structure when it acts as a horizontal diaphragm. In this study, the in-plane deformability of rectangular floors of single story buildings is examined under the effects of horizontal seismic actions. Therefore, the effects of parameters influencing the behavior of the floor such as size opening and their location, position of shear walls, span-to-depth ratio, and materials constituting the floor were studied. Results suggest that a diaphragm will behave in a flexible manner whether it is classified as rigid or flexible. However, a small opening in the floor can change the behavior of a diaphragm assumed rigid and make it behave like a flexible diaphragm. Additionally, flexible diaphragms can distribute horizontal seismic shear forces to vertical resisting elements due to the relative rigidity of the shear wall. These results are in contradiction with seismic codes such as ASCE/SEI 7-10 [1], FEMA 356 [2], and Eurocode 8[3], further the size of opening that make flexible diaphragm behave like rigid diaphragm was suggested by formula. For the building with a shear wall, the classification of the diaphragm in seismic codes such ASCE is not accurate enough and they need to reform with taking into consideration the location of the opening in the floor

Preliminary Observations of Geotechnical Failures During the 21 May 2003 M 6.8 Boumerdes, Earthquake, Algeria

At 18:44 UTC (19:44 local time) on May 21, 2003, a strong, shallow earthquake of Moment Magnitude (M) 6.8 shook northern Algeria and caused damage in five provinces in the north-central section of the country. Damage was reported over an area about 100 km long and 35 km wide, centered on the city of Boumerdes. The hardest hit areas were in the coastal province of Boumerdes, mainly in the cities of Boumerdes, Zemmouri and Thenia. The earthquake appears to have been generated by an offshore south-dipping thrust fault oriented N54°E extending for about 35 km from Dellys to Corso. The fault rupture was bilateral, with a greater asymmetry to the southwest. The ground motions recorded from the mainshock were significantly higher than median values predicted by standard attenuation relationships. Liquefaction and lateral spreading occurred near the Isser River and areas with extensive beach sand deposits. In the port of Algiers, nine piers suffered damage where liquefaction, loss of ground support, and lateral displacement (seaward movements) of the bulkheads were pervasive. Cracks developed on the Keddara and Beni Amrane Dams and the water line running from the Keddara Dam to the Boudouaou water treatment plant suffered damage at two locations

Uniaxial Tensile Stress-Strain Relationships of RC Elements Strengthened with FRP Sheets

The shear behavior of fiber-reinforced-polymer–strengthened reinforced concrete (FRP-strengthened RC) members is not fully developed and accurately predicted because of the lack of accurate constitutive laws for the components of the composite members. This paper presents experimental and analytical investigations of tensile stress-strain relationships of concrete and steel in FRP-strengthened RC members. These stress-strain relationships are required in formulations of softened truss models to predict the shear behavior of the FRP-strengthened RC element. Thirteen full-scale FRP-strengthened RC prismatic specimens with different FRP reinforcement ratios, steel reinforcement ratios, and FRP wrapping schemes were tested under uniaxial tension loading. The results show that the tensile behavior of the concrete and steel is altered because of the externally bonded FRP sheets. Modified constitutive laws are proposed and incorporated in the softened membrane model (SMM) to demonstrate through two tests the behavior of FRP-strengthened RC element subjected to pure shear. Moreover, crack spacing and crack width were studied and compared with existing code provisions

Interdisciplinary Graduate Experience: Lessons Learned

Engineers interact in the workplace with technical peers in other disciplines at all stages of design, development, and application. Awareness of the constraints and needs of the other disciplines can be key in many situations. Such interdisciplinary activity and the associated communication are facilitated if the all participants have a solid knowledge of discipline-specific terminology and an understanding of connecting concepts. Consequently, experience relating to interdisciplinary teamwork is a necessary component of engineering education. The Smart Engineering Group at the University of Missouri-Rolla was established to conduct interdisciplinary research and to create interdisciplinary educational resources. The topical interest area is smart structures which requires the integration of materials, structures, sensing, signal processing, manufacturing, etc. The interdisciplinary research and educational activities of the group, the assessment of those activities, and the experiences of several graduate students will be described. The effectiveness of collaborative student work was tied to the students- understanding of the needed synergy and their comfort with cross-disciplinary communication. Also, an interdisciplinary course, which grew out of the group-s experiences, provided systematic preparation for graduate research projects. The role of this course will be discussed as it relates to the quality of collaborative experiences from both student and faculty perspectives

Rubble Pile Characterization Model

Rubble piles created following the collapse of a building in a combat situation can significantly impact mission accomplishment, particularly in the area of movement and maneuver. Rubble characteristics must be known, for example, in order to predict the ability of a vehicle to override the collateral damage from weapon effects in urban areas. Two types of models are developed: a first-order model and a first-principles-based model. In both models, we assume complete rubblization of the building and develop a rubble profile model using the size and composition of the collapsed structure to predict the rubble volume. In both cases, this profile model includes the size of the footprint area surrounding the original building assuming that the rubble is free to expand horizontally as well as the resulting height of such a rubble pile. Empirical data is now needed to verify the predictive capabilities of these models

Cracking behavior and crack width predictions of FRP strengthened RC members under tension

This paper presents and discusses the experimental results of uniaxial tensile tests of fiber reinforced polymer externally strengthened reinforced concrete (FRP strengthened RC) prisms in terms of crack width and crack spacing. As a non-contact and material independent system for in-time measurement of displacement and strain, the digital image correlation (DIC) technique has been used in this study for investigating the evolution of strains and formation of cracks during uniaxial tensile tests. As a result, the cracks were measured precisely at any load stage. The experimental results of tests performed by authors and other researchers on FRP strengthened RC members in tension are compared to prediction models from code provisions and guidelines (Eurocode 2 and fib 14), and their suitability are analyzed and discussed. The results show the dependence of the behavior and crack characteristics of FRP strengthened RC members to parameters such as wrapping scheme and FRP reinforcement ratios which are not included in design provisions for crack analysis. A new formulation for predicting crack width and spacing in FRP strengthened RC members, calibrated using the experimental results, has been proposed which considers all the main affecting parameters