Pushover analysis of an existing reinforced concrete bridge:Jamboree Road Overcrossing in Irvine, California

The work for the present thesis started in California, during my semester as an exchange student overseas. California is known worldwide for its seismicity and its effort in the earthquake engineering research field. For this reason, I immediately found interesting the Structural Dynamics Professor, Maria Q. Feng's proposal, to work on a pushover analysis of the existing Jamboree Road Overcrossing bridge. Concrete is a popular building material in California, and for the most part, it serves its functions well. However, concrete is inherently brittle and performs poorly during earthquakes if not reinforced properly. The San Fernando Earthquake of 1971 dramatically demonstrated this characteristic. Shortly thereafter, code writers revised the design provisions for new concrete buildings so to provide adequate ductility to resist strong ground shaking. There remain, nonetheless, millions of square feet of non-ductile concrete buildings in California. The purpose of this work is to perform a Pushover Analysis and compare the results with those of a Nonlinear Time-History Analysis of an existing bridge, located in Southern California. The analyses have been executed through the software OpenSees, the Open System for Earthquake Engineering Simulation. The bridge Jamboree Road Overcrossing is classified as a Standard Ordinary Bridge. In fact, the JRO is a typical three-span continuous cast-in-place prestressed post-tension box-girder. The total length of the bridge is 366 ft., and the height of the two bents are respectively 26,41 ft. and 28,41 ft.. Both the Pushover Analysis and the Nonlinear Time-History Analysis require the use of a model that takes into account for the nonlinearities of the system. In fact, in order to execute nonlinear analyses of highway bridges it is essential to incorporate an accurate model of the material behavior. It has been observed that, after the occurrence of destructive earthquakes, one of the most damaged elements on highway bridges is a column. To evaluate the performance of bridge columns during seismic events an adequate model of the column must be incorporated. Part of the work of the present thesis is, in fact, dedicated to the modeling of bents. Different types of nonlinear element have been studied and modeled, with emphasis on the plasticity zone length determination and location. Furthermore, different models for concrete and steel materials have been considered, and the selection of the parameters that define the constitutive laws of the different materials have been accurate. The work is structured into four chapters, to follow a brief overview of the content. The first chapter introduces the concepts related to capacity design, as the actual philosophy of seismic design. Furthermore, nonlinear analyses both static, pushover, and dynamic, time-history, are presented. The final paragraph concludes with a short description on how to determine the seismic demand at a specific site, according to the latest design criteria in California. The second chapter deals with the formulation of force-based finite elements and the issues regarding the objectivity of the response in nonlinear field. Both concentrated and distributed plasticity elements are discussed into detail. The third chapter presents the existing structure, the software used OpenSees, and the modeling assumptions and issues. The creation of the nonlinear model represents a central part in this work. Nonlinear material constitutive laws, for concrete and reinforcing steel, are discussed into detail; as well as the different scenarios employed in the columns modeling. Finally, the results of the pushover analysis are presented in chapter four. Capacity curves are examined for the different model scenarios used, and failure modes of concrete and steel are discussed. Capacity curve is converted into capacity spectrum and intersected with the design spectrum. In the last paragraph, the results of nonlinear time-history analyses are compared to those of pushover analysis.

Steel and macro-synthetic self-compacting fibre reinforced concrete, experimental study on the long-term deformations

Experimental study on the long-term deformations of the fibre reinforced concrete. Steel and macro-synthetic fibers were used to evaluate the shrinkage, creep, mid-span deflection, cracking and rupture analysis of three different types of samples. At the end the main topics of ACI guidelines were analyzed in order to perform an overview of design.

Experimental Data on Fire-Resistance Behavior of Reinforced Concrete Structures with Example Calculations

This thesis selects concrete, steel and their relation as research subjects, mainly commentary and discusses the property changes of steel and concrete materials under and after high temperature.The differences and comparisons of reasearch methods and ways between different researchers and different papers,particularly for chinese researches and chinese papers,and partly for comparison between chinese papers methods and Euro-Amercian papers methods about Fire Resistance Behavior of Reinforced Concrete will be summarized and analyzed.The researches on fire-resistance behavior of reinforced concrete become more and more important all over the world. And I would find differences between Chinese researches results, between Chinese researches results and other countries researches results.

Time-dependent behaviour of reinforced concrete slabs

In this thesis is studied the long-term behaviour of steel reinforced slabs paying particular attention to the effects due to shrinkage and creep. Despite the universal popularity of using this kind of slabs for simply construction floors, the major world codes focus their attention in a design based on the ultimate limit state, restraining the exercise limit state to a simply verification after the design. For Australia, on the contrary, this is not true. In fact, since this country is not subjected to seismic effects, the main concern is related to the long-term behaviour of the structure. Even if there are a lot of studies about long-term effects of shrinkage and creep, up to date, there are not so many studies concerning the behaviour of slabs with a cracked cross section and how shrinkage and creep influence it. For this reason, a series of ten full scale reinforced slabs was prepared and monitored under laboratory conditions to investigate this behaviour. A wide range of situations is studied in order to cover as many cases as possible, as for example the use of a fog room able to reproduce an environment of 100% humidity. The results show how there is a huge difference in terms of deflections between the case of slabs which are subjected to both shrinkage and creep effects soon after the partial cracking of the cross section, and the case of slabs which have already experienced shrinkage effects for several weeks, when the section has not still cracked, and creep effects only after the cracking.

Study of the mechanisms of shear transfer in fiber-reinforced concrete elements

matlab functions for the validation of push-off tests results

Analysis of an innovative slim floor composite beam conformed by a custom GFRP pultruded profile and reinforced concrete.

GFRP pultruded profiles have shown to be structural profiles with great stiffness, strenght and very low specific weight, making it a great candidate for the rehabilitation of damaged strucutres. To further enhance the strucutral mechanism of these type of beams, the Slimflor composite structural system has lead as basis for this analysis; by replacing the steel beam with a GFRP pultruded profile. To further increase its composite action, a continuous shear connector has been set as part of the beam cross section as well as its needed reinforcement and fire protection.