Showing papers in "Journal of Structural Engineering-asce in 2005"
TL;DR: In this article, the authors presented a practical and user-friendly finite element (FE) model updating technique for real structures using ambient vibration test results, which is able to produce sufficient improvement on modal parameters of the concerned modes which is in close agreement with the experimental results still preserving the physical meaning of updated parameters.
Abstract: This paper presents a practical and user-friendly finite element (FE) model updating technique for real structures using ambient vibration test results. The first case study of a simulated simply supported beam demonstrates a comparative study of the influence of different possible residuals in objective function. Frequency residual only, mode shape related function only, modal flexibility residual only, and their combinations are studied independently. In view of tuning as well as damage localization, full objective function that considers all three residuals is the best for FE updating. This objective function is implemented in a second case study of a real concrete-filled steel tubular arch bridge. The bridge was tested by ambient vibration measurements. Followed by the three-dimensional FE modeling of the bridge, an eigenvalue sensitivity study is carried out to see the most sensitive parameters to the concerned modes. FE model mass matrix obtained from Guyan reduction technique is used to the mass normalization of the mode shapes extracted from ambient modal test to calculate the modal flexibility. The updated FE model of the bridge is able to produce a sufficient improvement on modal parameters of the concerned modes which is in close agreement with the experimental results still preserving the physical meaning of updated parameters.
359 citations
TL;DR: In this article, an effective numerical model using the finite element method to simulate the push-off test was proposed, which provided a better understanding to the different modes of failure observed during experimental testing and hence shear capacity of headed studs in solid concrete slabs.
Abstract: In composite beam design, headed stud shear connectors are commonly used to transfer longitudinal shear forces across the steel-concrete interface. Present knowledge of the load-slip behavior and the shear capacity of the shear stud in composite beam are limited to data obtained from the experimental push-off tests. For this purpose, an effective numerical model using the finite element method to simulate the push-off test was proposed. The model has been validated against test results and compared with data given in the current Code of Practices, i.e., BS5950, EC4, and AISC. Parametric studies using this model were preformed to investigate variations in concrete strength and shear stud diameter. The finite element model provided a better understanding to the different modes of failure observed during experimental testing and hence shear capacity of headed shear studs in solid concrete slabs.
283 citations
TL;DR: In this paper, a critical evaluation of equations commonly used to compute short-term deflection for steel and fiber reinforced polymer (FRP) reinforced concrete beams is provided, and the different approaches are linked together by comparing the tension-stiffening component of each method.
Abstract: This paper provides a critical evaluation of equations commonly used to compute short-term deflection for steel and fiber reinforced polymer (FRP) reinforced concrete beams Numerous proposals have been made for FRP in particular, and the different approaches are linked together by comparing the tension-stiffening component of each method Tension stiffening reflects the participation of concrete between cracks in stiffening the member response The Branson equation used in North America and other parts of the world is based on an empirically derived effective moment of inertia to calculate deflection The tension-stiffening component with this method is highly dependent on the applied level of loading relative to the cracking load as well as the ratio of uncracked-to-cracked transformed moment of inertia ( Ig ∕ Icr ) for the beam section Tension stiffening is overestimated for the high Ig ∕ Icr ratios typical with FRP concrete, leading to a much stiffer response and underprediction of member deflection
261 citations
TL;DR: In this article, an approximate method to estimate floor acceleration demands in multistory buildings responding elastically or practically elastic when subjected to earthquake ground motion is presented, and the effect of reduction of lateral stiffness along the height is investigated.
Abstract: An approximate method to estimate floor acceleration demands in multistory buildings responding elastically or practically elastic when subjected to earthquake ground motion is presented. The method can be used to estimate floor acceleration demands at any floor level for a given ground motion record. The dynamic characteristics of the building are approximated by using a simplified model based on equivalent continuum structure that consists of a combination of a flexural beam and a shear beam. Closed-form solutions for mode shapes, period ratios, and modal participation factors are presented. The effect of reduction of lateral stiffness along the height is investigated. It is shown that the effect of reduction in lateral stiffness on the dynamic characteristics of the structure is small in buildings that deflect laterally like flexural beams. For other buildings, approximate correction factors to the closed-form solutions of the uniform case are presented to take into account the effects of reduction of lateral stiffness. Approximate dynamic properties of the building are then used to estimate acceleration demands in the building using modal analysis.
250 citations
TL;DR: In this article, a beam-to-column moment connection is applied to simulate earthquake loading effects, and the experimental results demonstrate that the posttensioned connection possesses good energy dissipation and ductility.
Abstract: Six full-scale interior connection subassemblies of posttensioned wide flange beam-to-column moment connections were subjected to inelastic cyclic loading up to 4% story drift to simulate earthquake loading effects. Bolted top and seat angles are used in the connection, along with posttensioned high strength strands that run parallel to the beam. These strands compress the beam flanges against the column flange to develop the resisting moment to service loading and to provide a restoring force that returns the structure to its initial position following an earthquake. The parameters studied in these experiments were the initial posttensioning force, the number of posttensioning strands, and the length of the reinforcing plates. The experimental results demonstrate that the posttensioned connection possesses good energy dissipation and ductility. Under drift levels of 4%, the beams and columns remain elastic, while only the top and seat angles are damaged and dissipate energy. The lack of damage to the beams, columns, and the posttensioning enable the system to return to its plumb position (i.e., it self-centers). Closed-form expressions are presented to predict the connection response and the results from these expressions compare well with the experimental results.
247 citations
TL;DR: In this article, a post-tensioned friction damped connection (PFDC) for steel moment resisting frames (MRFs) is introduced, which minimizes inelastic deformation to the components of the connection as well as the beams and columns, and requires no field welding.
Abstract: A post-tensioned friction damped connection (PFDC) for earthquake resistant steel moment resisting frames (MRFs) is introduced. The connection includes friction devices on the beam flanges with post-tensioned high strength strands running parallel to the beam. The connection minimizes inelastic deformation to the components of the connection as well as the beams and columns, and requires no field welding. Inelastic analyses were performed on a six-story, four-bay steel MRF with PFDCs to study its response to strong ground motions. The PFDC–MRF was designed using a performance based design approach. Results show the MRF with PFDCs has good energy dissipation, self-centering capability, and strength. Variability in the maximum friction forces that develop in the friction devices was determined not to have a significant effect on the MRF performance. The analyses indicate that the seismic performance of a MRF with PFDCs can exceed that of a MRF with conventional moment resisting connections.
246 citations
TL;DR: A design procedure utilizing an ant colony optimization (ACO) technique is developed for discrete optimization of steel frames and a comparison is presented between the ACO frame designs and designs developed using a genetic algorithm and classical continuous optimization methods.
Abstract: A design procedure utilizing an ant colony optimization (ACO) technique is developed for discrete optimization of steel frames. The objective function considered is the total weight (or cost) of the structure subjected to serviceability and strength requirements as specified by the American Institute for Steel Construction (AISC) Load and Resistance Factor Design, 2001. The design of steel frames is mapped into a modified traveling salesman problem (TSP) where the configuration of the TSP network reflects the structural topology, and the resulting length of the TSP tour corresponds to the weight of the frame. The number of potential paths between nodes in the TSP network represents all (or a portion) of the available W-shapes in the AISC database. The resulting frame, mapped into a TSP, is minimized using an ACO algorithm with a penalty function to enforce strength and serviceability constraints. A comparison is presented between the ACO frame designs and designs developed using a genetic algorithm and classical continuous optimization methods.
225 citations
TL;DR: In this article, a light-gauge steel plate shear wall is designed as seismic retrofits for a hospital structure in an area of high seismicity, and emphasis is placed on minimizing their impact on the existing framing.
Abstract: This paper describes the prototype design, specimen design, experimental setup, and experimental results of three light-gauge steel plate shear wall concepts. Prototype light-gauge steel plate shear walls are designed as seismic retrofits for a hospital structure in an area of high seismicity, and emphasis is placed on minimizing their impact on the existing framing. Three single-story test specimens are designed using these prototypes as a basis, two specimens with flat infill plates (thicknesses of 0.9 mm) and a third using a corrugated infill plate (thickness of 0.7 mm). Connection of the infill plates to the boundary frames is achieved through the use of bolts in combination with industrial strength epoxy or welds, allowing for mobility of the infills if desired. Testing of the systems is done under quasi-static conditions. It is shown that one of the flat infill plate specimens, as well as the specimen utilizing a corrugated infill plate, achieve significant ductility and energy dissipation while minimizing the demands placed on the surrounding framing. Experimental results are compared to monotonic pushover predictions from computer analysis using a simple model and good agreement is observed.
219 citations
TL;DR: In this article, a concrete filled steel tubular (CFT) column system, named as confined CFT or CCFT, is proposed for improved seismic design of steel and concrete composite structures.
Abstract: This paper presents a study to introduce and experimentally validate an innovative concrete filled steel tubular (CFT) column system, named as confined CFT or CCFT, for improved seismic design of steel and concrete composite structures. Based on fundamental mechanics, the concept is aimed at controlling the local buckling of the steel tube and confining the concrete in the potential plastic hinge regions of a CFT column. To achieve this, several efficient details of transverse confinement are proposed. In the first phase of the study, carbon-fiber-reinforced plastic as additional confinement of CCFT columns was examined through experimental testing. As demonstrated from the results of axial compression tests and seismic loading tests, the new type of CFT column system can provide excellent seismic performance. The complicated local buckling and confinement mechanisms were examined using a proposed simple analytical model.
218 citations
TL;DR: In this paper, the authors present recent efforts that have demonstrated an innovative use of thin-membrane elastomeric polymers to prevent breaching and collapse of unreinforced masonry walls subjected to blast.
Abstract: Recent terrorist attacks indicate the improvised explosive device as the choice terror tactic. Over the past decade, the U.S. Department of Defense has encouraged and sponsored research toward developing methods of reinforcing structures to protect building occupants from the effects of external explosion. The focus of wall reinforcement research has recently shifted from applying stiff fiber-reinforced composites to using lower-strength higher-elongation elastomeric polymers that can be easily applied to the wall interior. This paper presents recent efforts that have demonstrated an innovative use of thin-membrane elastomeric polymers to prevent breaching and collapse of unreinforced masonry walls subjected to blast. The complex array of failure mechanisms observed from recent explosive tests is discussed. Effects of structural and nonstructural parameters are described with the aid of finite-element simulations. Finally, the needs and direction of future blast reinforcement developments are outlined.
203 citations
TL;DR: In this article, a general analysis and design methodology that not only accounts for the interaction of the plates and the framing system but also can be used to better understand the linear and nonlinear behavior of different DSPW configurations.
Abstract: During the last 3 decades interest has grown globally in the application of ductile steel plate walls (DSPWs) (or steel plate shear walls) for building lateral load resistance. The supporting theory has evolved from both analytical and experimental research conducted in several countries around the world. The advantages of using DSPWs as the lateral force resisting system in buildings include stable hysteretic characteristics, high plastic energy absorption capacity, and enhanced stiffness, strength and ductility. A significant number of experimental and analytical studies have been carried out to establish analysis and design methods for such lateral resisting systems. Despite these efforts there is still a need for a general analysis and design methodology that not only accounts for the interaction of the plates and the framing system but also can be used to better understand the linear and nonlinear behavior of different DSPW configurations. These configurations include DSPWs with thin or thick steel p...
TL;DR: In this paper, the static pushover 2 incremental dynamic analysis (SPO2IDA) is used to estimate the seismic demand and capacity of first-mode-dominated multidegree-of-freedom systems in regions ranging from near-elastic to global collapse.
Abstract: Introducing a fast and accurate method to estimate the seismic demand and capacity of first-mode-dominated multidegree-of- freedom systems in regions ranging from near-elastic to global collapse. This is made possible by exploiting the connection between the static pushover ~SPO! and the incremental dynamic analysis ~IDA!. While the computer-intensive IDA would require several nonlinear dynamic analyses under multiple suitably scaled ground motion records, the simpler SPO helps approximate the multidegree-of-freedom system with a single-degree-of-freedom oscillator whose backbone matches the structure's SPO curve far beyond its peak. Similar methodologies exist but they usually employ oscillators with a bilinear backbone. In contrast, the empirical equations implemented in the static pushover 2 incremental dynamic analysis (SPO2IDA) software allow the use of a complex quadrilinear backbone shape. Thus, the entire summarized IDA curves of the resulting system are effortlessly generated, enabling an engineer-user to obtain accurate estimates of seismic demands and capacities for limit-states such as immediate occupancy or global dynamic instability. Using three multistory buildings as case studies, the methodology is favorably compared to the full IDA.
TL;DR: In this article, the authors performed large scale tests with progressive damage on a prestressed concrete highway bridge to investigate the sensitivity of several damage detection, localization, and quantification methods based on modal parameters.
Abstract: Large scale tests with progressive damage on a prestressed concrete highway bridge have been performed to investigate the sensitivity of several damage detection, localization, and quantification methods based on modal parameters. To investigate the quality of modal parameters, the data set of one damage step was analyzed by several output-only identification techniques. Although the bridge was severely cracked, natural frequencies as well as mode shapes display only minor changes. However, the relative changes of mode shapes are larger than those observed for natural frequencies. A novel damage indicator, called mode shape area index, based on changes of mode shapes, has been developed and found as the most sensitive damage detection approach. Damage detection or localization via changes of the flexibility matrix performed better than natural frequencies or mode shapes alone. The application of the direct stiffness calculation and a sensitivity-based model update technique showed results having a high level of ambiguity about the location and quantification of damage also at the highest damage level. Evaluating the information collected in this study the test results indicate that an early stage damage identification in prestressed concrete bridges is hardly possible because of the nearly complete recovery of stiffness after closing of cracks in prestressed concrete and the effect of environmental parameters on modal data.
TL;DR: In this article, a simple procedure to estimate the local displacement demands in regular frame-type structures that respond in elastic limits is described, given the spectral displacement and beam-to-column stiffness ratio, the procedure estimates the maximum ground story and maximum interstory drifts along the height of the structure.
Abstract: A simple procedure to estimate the local displacement demands in regular frame-type structures that respond in elastic limits is described. Given the spectral displacement and beam-to-column stiffness ratio, the procedure estimates the maximum ground story and maximum interstory drifts along the height of the structure. A total of 145 near-fault ground motions recorded on dense-to-firm soil sites are used for the evaluation of the procedure. The approximate drift demands computed from this procedure and the exact results from 27,550 response history analyses are used for calculating the error statistics. The calculations show that the procedure can be used with confidence for frames with fundamental periods between 0.3 and 1.5 s when they are subjected to near-fault records without pulse. The approximations are in good agreement with the exact response history results of near-fault records with pulse when the fundamental period to pulse period ratio is less than 1.5. The performance of the new procedure is also compared with other approximate methods that are employed for similar purposes. The method can be useful for preliminary design of new structures or rapid assessment of existing buildings.
TL;DR: In this article, a total of 23 tests were conducted to study the cyclic loading performance of links in steel eccentrically braced frames, with various lengths ranging from short shear yielding links to very long flexural yielding links.
Abstract: A total of 23 tests were conducted to study the cyclic loading performance of links in steel eccentrically braced frames. The objectives of these tests were to reevaluate flange slenderness limits and overstrength factors for links. The effect of loading history on link performance was also investigated. Link specimens were constructed from five different wide-flange sections, all of ASTM A992 steel, with various lengths ranging from short shear yielding links to very long flexural yielding links. In addition to providing data on the effects of flange buckling and overstrength, these tests also showed some unexpected failure modes. The paper provides an overview of this experimental investigation, describing the overall research program, as well as details of the test specimens and test results. The paper concludes with a number of design recommendations for links in eccentrically braced frames.
TL;DR: In this paper, a two-dimensional spatial time-dependent reliability model is developed to predict the likelihood and extent of corrosion-induced cracking in a typical reinforced concrete bridge deck, and the effect of concrete cover, concrete quality, limit crack width, and environment are considered.
Abstract: Corrosion-induced cracking is observed to vary spatially over concrete surfaces. A two-dimensional spatial time-dependent reliability model is developed to predict the likelihood and extent of corrosion-induced cracking. The spatial variability of concrete cover, concrete compressive strength, and surface chloride concentration are considered in the spatial time-dependent reliability model. The reliability analysis predicts: (1) probability of the first incidence of cracking, (2) proportion of an area subject to severe cracking, and (3) probability that a given percentage of a concrete surface has cracked. Corrosion-induced crack initiation and propagation models are developed for limit crack widths up to 1 mm. The present paper presents results for a typical reinforced concrete bridge deck. The effect of concrete cover, concrete quality, limit crack width, and environment are considered. It was shown that for poor durability design specifications the likelihood and extent of spalling is high. When combined with a life-cycle cost analysis, this predictive capability enables the extent of future repair costs to be estimated and the optimal durability design specifications or repair/maintenance strategies determined.
TL;DR: In this article, the effects of initial local and overall geometric imperfections have been taken into consideration in the analysis of cold-formed steel plain angle columns, and the effect of residual stresses on the buckling behavior was studied using the finite element model.
Abstract: The main objective of this paper is to provide an efficient and accurate finite element model to understand the behavior of cold-formed steel plain angle columns. The effects of initial local and overall geometric imperfections have been taken into consideration in the analysis. The material nonlinearities of flat and corner portions of the angle sections were incorporated in the model. Failure loads and buckling modes as well as load-shortening curves of plain angle columns were investigated in this study. Furthermore, the residual stresses of a column test specimen were measured and plotted. The effect of residual stresses on the buckling behavior was studied using the finite element model. The nonlinear finite element model was verified against experimental results. The finite element analysis was performed on plain angles compressed between fixed ends over different column lengths, and column curves were obtained. An extensive parametric study was carried out using the finite element model to study the effects of cross-section geometries on the strength and behavior of angle columns. The column strengths predicted from the finite element model were compared with the design strengths calculated using the American Specification and Australian/New Zealand Standard for cold-formed steel structures. In addition, the results obtained from the finite element model were also compared with the design strengths obtained from the design rules proposed by other researchers.
TL;DR: In this paper, a structural wood-concrete composite system is presented, which is formed by joining a wood component, such as a floor beam or laminated plate, to a concrete slab utilizing a continuous steel mesh of which one half is glued into a slot in the wood while the other half is embedded into the concrete.
Abstract: This paper introduces a new, structural wood-concrete composite system. The system is formed by joining a wood component, such as a floor beam or laminated plate, to a concrete slab utilizing a continuous steel mesh of which one half is glued into a slot in the wood while the other half is embedded into the concrete. Two series of tests were performed and are presented: static push-out tests to establish shear properties of the connector and a full scale bending test with a span of approximately 10 m. Test results reveal that the steel mesh performs favorably—as a stiff yet ductile shear connector between the wood and the concrete. Design equations, per European standards in absence of North American standards are described and used to predict the failure load of the bending test. Calculations indicate that the tested beam performs with near full composite action—specifically, 97% effective stiffness and 99% strength of that of a beam with full composite action. This is a marked improvement in the efficiency of wood-concrete systems developed to date. The system shows itself to be superior to alternative systems in its high structural efficiency as well as being relatively easy to install and economic.
TL;DR: In this paper, the behavior of cold-formed high strength stainless steel sections was analyzed using stub column tests and the initial local plate imperfection profiles were plotted. And the material properties of the complete cross section in the cold-worked state were also obtained from stub columns tests.
Abstract: This paper presents the behavior of cold-formed high strength stainless steel sections. The test specimens were cold-rolled from flat strips of duplex and high strength austenitic stainless steel. The material properties of high strength stainless steel square and rectangular hollow sections were determined. Tensile coupons at different locations in cross section were tested. Hence, the distributions of 0.2% proof stress and tensile strength measured in the cross section of cold-formed high strength stainless steel sections were plotted. The material properties of the complete cross section in the cold-worked state were also obtained from stub column tests. Detailed measurements of initial local geometric imperfections of the sections were obtained. The initial local plate imperfection profiles were plotted. Residual stress measurements of the high strength stainless steel sections were also conducted. The membrane and bending residual stress distributions in the cross section of the specimens were obtained. Furthermore, the stub column test strengths were compared with the design strengths.
TL;DR: In this paper, a simple dimensional analysis of the size effect of reinforced concrete beams was performed and the authors showed that the failure is caused by cohesive (or quasibrittle) fracture propagation and the maximum load is attained only after large fracture growth.
Abstract: The shear failure of reinforced concrete beams is a very complex fracture phenomenon for which a purely mathematical approach is not possible at present. However, detailed modeling of the fracture mechanism is not necessary for establishing the general form of the size effect. The first part of this paper shows that the general approximate mathematical form of the size effect law to be calibrated by experimental data can be deduced from two facts: (1) the failure is caused by cohesive (or quasibrittle) fracture propagation; and (2) the maximum load is attained only after large fracture growth (rather than at fracture initiation). Simple dimensional analysis yields the asymptotic properties of size effect, which are characterized by: (1) a constant beam shear strength vc (i.e., absence of size effect) for sufficiently small beam depths; and (2) the linear elastic fracture mechanics size effect vc ∼ d−1∕2 for very large beam depths d . Together with the recently established small- and large-size second-orde...
TL;DR: In this paper, the life-cycle maintenance planning of deteriorating bridges is formulated as a multi-objective optimization problem that treats the lifetime condition and safety levels as separate objective functions, and a multiobjective genetic algorithm is used as the search engine to automatically locate a large pool of different maintenance scenarios that exhibits an optimized tradeoff among conflicting objectives.
Abstract: Many of the currently available bridge management system tools focus on minimizing life-cycle maintenance cost of deteriorating bridges while imposing constraints on structural performance. The computed single optimal maintenance planning solution, however, may not necessarily meet a bridge manager's specific requirements on lifetime bridge performance. In this paper the life-cycle maintenance planning of deteriorating bridges is formulated as a multiobjective optimization problem that treats the lifetime condition and safety levels as well as life-cycle maintenance cost as separate objective functions. A multiobjective genetic algorithm is used as the search engine to automatically locate a large pool of different maintenance scenarios that exhibits an optimized tradeoff among conflicting objectives. This tradeoff provides improved opportunity for bridge managers to actively select the final maintenance scenario that most desirably balances life-cycle maintenance cost, condition, and safety levels of deteriorating bridges.
TL;DR: In this article, an alternative approach is proposed that leverages the capabilities of existing nonlinear dynamic pier analysis programs by adding dynamic barge behavior in a computationally efficient and modular manner.
Abstract: Assessing the structural response and vulnerability of bridge piers to collisions by barges typically involves either the use of static pier analysis codes and design-specification-stipulated equivalent static loading conditions, or a lengthy model development process followed by use of general-purpose finite-element codes. In this paper, an alternative approach is proposed that leverages the capabilities of existing nonlinear dynamic pier analysis programs by adding dynamic barge behavior in a computationally efficient and modular manner. By coupling nonlinear barge and pier responses together through a shared collision impact force and employing numerical procedures for accelerating convergence of the coupled system, dynamic barge collision analyses may be conducted for bridge piers efficiently and rapidly. The influence of impact parameters such as barge type and mass, impact speed and angle, and pier configuration can then be efficiently evaluated using dynamic collision analyses. For demonstration purposes, the method is implemented in an existing pier analysis program, validated, and used to conduct selected case studies.
TL;DR: In this article, a re-examination of gust factors associated with hurricanes is presented, with the observed gust factors compared to those determined using theoretically based models derived for extratropical storm winds, and the results suggest that in most cases hurricane gust factors can be described using models developed for standard neutral boundary layer flow conditions.
Abstract: This paper describes a re-examination of gust factors associated with hurricanes. The hurricane gust factors for the over-land and over-water cases are examined separately, with the observed gust factors compared to those determined using theoretically based models derived for extratropical storm winds. The results of the study suggest that in most cases hurricane gust factors can be described using models developed for standard neutral boundary layer flow conditions. Large, anomalous gust factors associated with convective gusts were found; however, these high gust factors were all observed well away from the hurricane eyewall in all cases.
TL;DR: In this paper, a model was developed to predict, for a given level of lateral deformation, the likelihood that longitudinal bars in a reinforced concrete column will have begun to buckle, based on the results of plastic-hinge analysis, moment-curvature analysis, and the expected influence of the confinement reinforcement.
Abstract: A practical model has been developed to predict, for a given level of lateral deformation, the likelihood that longitudinal bars in a reinforced concrete column will have begun to buckle. Three relationships linking plastic rotation, drift ratio, and displacement ductility with the onset of bar buckling were derived based on the results of plastic-hinge analysis, moment-curvature analysis, and the expected influence of the confinement reinforcement. These relationships, which account for the effective confinement ratio, axial-load ratio, aspect ratio, and longitudinal bar diameter, were calibrated using observations of bar buckling from cyclic tests of 62 rectangular-reinforced and 42 spiral-reinforced concrete columns. A version of the drift ratio relationship is proposed for earthquake engineering applications. The ratios of the measured displacements at bar buckling to the displacements calculated with the proposed model had a mean of 1.01 and a coefficient of variation of 25% for rectangular-reinforced concrete columns. The corresponding mean and coefficient of variation for spiral-reinforced columns were 0.97 and 24%, respectively.
TL;DR: In this paper, the results of experimental research on the structural behavior of dry joint masonry walls are presented and conclusions on their ultimate capacity and observed failure mechanisms are addressed, and the application of an existing numerical model, stemming from plasticity and based on a micromodeling strategy, is also presented and discussed with regard to its capacity to simulate the obtained experimental results.
Abstract: The paper presents the results of experimental research on the structural behavior of dry joint masonry. The most relevant experimental results concern the strength response of stone dry joint masonry walls subjected to in-plane combined compressive and shear loading. Significant features of the structural behavior shown by the walls are discussed and conclusions on their ultimate capacity and observed failure mechanisms are addressed. Complementarily, the application of an existing numerical model, stemming from plasticity and based on a micromodeling strategy, is also presented and discussed with regard to its capacity to simulate the obtained experimental results. The model was calibrated with data collected from complementary tests carried out on specimens and prisms made of the same type of stone. Finally, the usage of a simplified method of analysis based on a continuum of diagonal struts is also addressed.
TL;DR: In this article, the authors developed a constitutive relationship that predicts the behavior of reinforcing bars under compression given the geometric and material properties, and evaluated the impact of the rebar buckling on the deformation capacity of reinforced concrete members at plastic hinges.
Abstract: Predicting behavior of concrete members subjected to large inelastic deformations caused by extreme loads, such as earthquakes, plays an important role in assessing stable deformation capacities of concrete structures. An objective of the research is to contribute to the development of a constitutive relationship that predicts the behavior of reinforcing bars under compression given the geometric and material properties. By developing a constitutive relationship for the reinforcing bars under compression, conventional sectional analyses can be extended to incorporate the buckling of longitudinal reinforcement. This will enable an engineer to evaluate the pre- and postbuckling behavior of reinforcing bars under compression given the material properties and geometric nature of the problem, and hence evaluate the impact of the rebar buckling on the deformation capacity of reinforced concrete members at plastic hinges. This paper presents results from an experimental program for bar buckling in which a total ...
TL;DR: In this article, a nonlinear shear force-deformation model for the panel zone in beam-to-column CFT connections was proposed for predicting the elastoplastic behavior of the panel zones.
Abstract: Subassemblage tests were conducted on the panel zone within steel beam-to-concrete filled steel tube (CFT) column moment connections made from high-strength material to investigate their elastoplastic behavior. The writers propose a nonlinear shear force-deformation model for the panel zone in beam-to-column CFT connections for predicting the elastoplastic behavior of the panel zones. The proposed model includes a superposed model based on a trilinear shear-deformation relationship for the steel tube superposed on one for the concrete core, and a simple model provided as a trilinear model having a yield strength point and an ultimate strength point for this panel zone, as a practical model for design. The writers also propose a method for evaluating load resistance, in which a new theoretical compression strut mechanism is utilized, taking into account the confinement of the tube flange. The results predicted using the superposed and the simple model are found to agree approximately with the experimental results up to a large shear deformation of 0.04 rad.
TL;DR: In this article, a simplified finite-element analysis program based on multilayer elements and damage mechanics modeling of concrete behavior is presented to predict the behavior of three different structures: overreinforced normal strength concrete and high-strength concrete (HSC) beams tested monotonically, HSC columns tested under constant axial load and cyclic flexure, and bridge piers subjected to earthquake type loading by the pseudodynamic test method.
Abstract: Performance-based design of structures is becoming the preferred seismic design method. Its use requires special numerical programs capable of predicting the performance of structures during a seismic event well into the nonlinear range. Seismic analysis results obtained from these programs depend on the types of elements and constitutive material laws used. For one type of element used, the results can be sensitive to the size of the elements. This paper presents a simplified finite-element analysis program based on multilayer elements and damage mechanics modeling of concrete behavior. A method to identify the various parameters required to define the behavior of the different materials is presented and some guidance on structural modeling using this type of program is provided. This program is used to predict the behavior of three different structures: overreinforced normal-strength concrete and high-strength concrete (HSC) beams tested monotonically, HSC columns tested under constant axial load and cyclic flexure, and bridge piers subjected to earthquake-type loading by the pseudodynamic test method. It is shown that predictions are in excellent agreement with experimental results.
TL;DR: In this paper, a series of physical experiments is used to develop methods for predicting the hazard levels associated with concrete masonry units (CMUs), commonly known as concrete blocks, which may become a debris hazard to building occupants when high explosives, for example, a terrorist vehicle bomb, are detonated outside of a building.
Abstract: Exterior wall panels of structures are often constructed of concrete masonry units (CMUs), commonly known as concrete blocks. These walls may become a debris hazard to building occupants when high explosives, for example, a terrorist vehicle bomb, are detonated outside of a building. A recently completed series of physical experiments is being used to develop methods for predicting the hazard levels associated with CMU walls. Retrofitting techniques have been developed to mitigate these hazards. The experiments included nonretrofitted CMU walls as well as several different types of retrofits. Test data, high-speed video, and posttest inspection of the experiments were used to assess the parameters that affect the response of CMU walls and retrofit systems. The objective of the research presented in this paper is to collect data on the blast response of CMU walls so that improvements can be made to the previously developed Wall Analysis Code (WAC).
TL;DR: In this article, the beam-column finite element formulations for full nonlinear distributed plasticity analysis of planar frame structures are presented using a total Lagrangian corotational approach.
Abstract: This paper presents several beam–column finite element formulations for full nonlinear distributed plasticity analysis of planar frame structures. The fundamental steps within the derivation of displacement-based, flexibility-based, and mixed elements are summarized. These formulations are presented using a total Lagrangian corotational approach. In this context, the element displacements are separated into rigid-body and deformational (or natural) degrees of freedom. The element rigid-body motion is handled separately within the mapping from the corotational to global element frames. This paper focuses on the similarities and differences in the element formulations associated with the element natural degrees of freedom within the corotational frame. The paper focuses specifically on two-dimensional elements based on Euler–Bernoulli kinematics; however, the concepts are also applicable to general beam–column elements for three-dimensional analysis. The equations for the consistent tangent stiffness matric...