Evaluation of Seismic Analysis Procedures for Concrete Moment-Resistant Frames with Horizontal Re-entrant Corners Irregularity

Seismic design codes and standards such as the IBC 2012 and ASCE/SEI 7-10 allow using different seismic analysis procedures for buildings having horizontal re-entrant corner irregularity. However, such codes allow using Equivalent Lateral Force (ELF) procedure for buildings having re-entrant corner irregularity but not exceeding 50 m in height. The aim of this study is to quantify the limits on building height and on the percentage of re-entrant corner of building, where ELF procedure may not produce a reasonable results when compared to Response Spectrum (RS) and Response Time History (TH) procedures. Usually, these limits in seismic design standards are based on judgments and experience rather than quantification studies. Based on the results of this study, it is observed that using ELF method mostly overestimates maximum displacements and drift ratio. However, this method can be used safely up to 12-storey buildings, because the maximum underestimation of column shear forces for buildings with higher stories gives 30% less compared to other procedures. Moreover, it has been found that the maximum underestimation of column shear forces for buildings without re-entrant corner is 0% less than those with re-entrant corners. Furthermore, buildings analysed by ELF method are also exposed to have a higher percentage value of underestimation of column shear forces as the case of 12-story buildings with 40% less when compared to TH Procedure. In addition, the column at the re-entrant corner is not effectively affected until a re-entrant corner of 25% exists in buildings. Thus the ASCE/SEI 7-10’s limit for using ELF procedure for buildings with re-entrant corner irregularity may be increased from 15% to 25% with less conservative results

Hyperbolic P-Y Criterion for Cohesive Soils

Drilled shafts have been frequently used as a foundation to support lateral loads. The p-y method of analysis has been widely used for predicting the behavior of laterally loaded drilled shafts. The existing p-y criteria for cohesive soils are divided into soft or stiff clays, on the basis of a limited number of lateral load test results. Currently, there is no p-y criterion developed for cohesive intermediate geomaterial. In this paper, a hyperbolic equation for p-y curve is presented for cohesive soils and intermediate geomaterials. Based on 3-D FEM simulation results, a new empirical equation is presented for calculating the initial tangent to p-y curve. The proposed hyperbolic p-y criterion is verified by using the results of six full-scale lateral load tests on fully instrumented drilled shafts with diameters ranging from 0.76 m to 1.83 m in the geo-medium ranging from soft clays to intermediate geomaterial. The proposed hyperbolic p-y criterion is shown to be capable of predicting the loaddeflection and bending moments of the laterally loaded shafts for the six cases studied in this paper

A Software Evolution Process Model: Analysis of Software Failure Causes

This paper presents a study on the degree of impact of several components on the evolvability of software systems. In particular, it focuses on failure rates, testing, and other factors which force the evolution of a software system. Also, it studies the evolution of software systems in the presence of various failure scenarios. Unlike previous studies based on the system dynamic (SD) model, this study is modeled on the basis of actor-network theory (ANT) of software evolution, using the system dynamic environment. The main index used in this study is the destabilization period after the recovery from any failure scenario. The results show that more testing and quick recovery after failure are keys to a fast system return to stability

A Software Evolution Process Model: Analysis of Software Failure Causes

This paper presents a study on the degree of impact of several components on the evolvability of software systems. In particular, it focuses on failure rates, testing, and other factors which force the evolution of a software system. Also, it studies the evolution of software systems in the presence of various failure scenarios. Unlike previous studies based on the system dynamic (SD) model, this study is modeled on the basis of actor-network theory (ANT) of software evolution, using the system dynamic environment. The main index used in this study is the destabilization period after the recovery from any failure scenario. The results show that more testing and quick recovery after failure are keys to a fast system return to stability

Non-Linear Seismic Response of Base-Isolated Frame Structures Using Rubber Bearings

Over the past two decades, much progress has been made in research and application of the base isolation of structures as means of providing earthquake resistance to a structure. However, the trade-off between the extent of acceleration reduction and the response of a base-isolation system has not been given a serious consideration. This work uses a new material constitutive model for rubber bearing base-isolation system, which adopts the technique of real-time structural parameter modification. To achieve this, a finite element modeling and analysis are performed as a comparative study between a conventional totally fixed-base steel frame structure and similar base-isolated structures using rubber-steel bearings. The structures are subjected to the El-Centro, N-S earthquake. In order to include nonlinearity effects, a non-linear hyperviscoelastic material model has been used and linked to ABAQUS software as a user defined material subroutine (i.e., UMAT). Special connector elements are selected from ABAQUS library to connect the rubber bearings to the frame structure and the foundations in order to achieve the required kinematical constraints at the connection points. The model is validated by carrying out a comparative study of the results obtained from the analysis of the presented material model with those obtained by using the existing ABAQUS material models (e.g., Ogden material model). The results show a significance efficiency of using the rubber bearing isolation in order to uncouple the structure from the seismic ground motion. Moreover, it has been proved that the used material model is more effective to capture the behavior of the base-isolated structures expressing a notable reduction in acceleration and an increase in the structural resistance to earthquake excitations

Symmetrical and Anti-Symmetrical Buckling of Long Corroded Cylindrical Shell Subjected to External Pressure

This paper derives an exact analytical solution for determining elastic critical buckling pressures and mode shapes for very long corroded cylindrical steel shells subjected to external pressure considering symmetrical and anti-symmetrical mode cases. The corroded long cylindrical shell has been modelled as a non-uniform “stepped-type” ring consisting of two portions- corroded and un-corroded regions. A full range parametric study has been made to investigate the effect of corrosion angular extent and corrosion thickness on the elastic buckling pressures and their modes. The study shows that buckling loads and modes depend on the corrosion angular extent â and the corroded to un-corroded thicknesses ratio. The results are verified by a set of investigations with a series of corroded cylindrical shells. They showed a close agreement with those obtained from using the finite element package ABAQUS

Effect of Jordanian Steel Blast Furnace Slag on Asphalt Concrete Hot Mixes

Significant quantities of slag are generated as waste materials or by-product from steel industries. They usually contain considerable quantities of metals. In this study, steel slag obtained from a steel factory in Jordan was used in Asphalt Concrete Hot Mixes (ACHM). Marshall specimens were prepared with 100% lime stone dense graded aggregates at 4.5, 5, 5.5 and 6% bitumen contents by weight of aggregate to serve as control specimens. Another set of Marshall specimens with 100% Steel Slag Aggregates (SSA) and another set with a combination of limestone and (SSA) were prepared using the same grading and bitumen contents. Test results showed a reduction in the Optimum Bitumen Content (OBC) and an increase in density and stability values for specimens prepared with 100% (SSA). A decrease in the flow, Percentage of air voids (Pav), and Voids in Mineral Aggregates (VMA) values - but in compliance with the recommended values by the Asphalt Institute- was observed in specimens prepared with 100% (SSA)

Transient Mixed Convection Flow of A Second-Grade Visco-Elastic Fluid over a Vertical Surface

The viscoelastic boundary layer flow and mixed convection heat transfer near a vertical isothermal surface have been examined in this paper. The governing equations are formulated and solved numerically using an explicit finite difference technique. The velocity and temperature profiles, boundary layer thicknesses, Nusselt numbers and the local skin friction coefficients are shown graphically for different values of the viscoelsatic parameter. In general, it is found that the velocity decreases inside the boundary layer as the viscoelsatic parameter is increased and consequently, the local Nusselt number decreases. This is due to higher tensile stresses between viscoelsatic fluid layers which has a retardation effects on the motion of these layers and consequently, on the heat transfer rates for the mixed convection heat transfer problem under investigation. A Comparison with available published results on special cases of the problem shows excellent agreement

MSAIndelFR: a scheme for multiple protein sequence alignment using information on indel flanking regions

Background The alignment of multiple protein sequences is one of the most commonly performed tasks in bioinformatics. In spite of considerable research and efforts that have been recently deployed for improving the performance of multiple sequence alignment (MSA) algorithms, finding a highly accurate alignment between multiple protein sequences is still a challenging problem. Results We propose a novel and efficient algorithm called, MSAIndelFR, for multiple sequence alignment using the information on the predicted locations of IndelFRs and the computed average log–loss values obtained from IndelFR predictors, each of which is designed for a different protein fold. We demonstrate that the introduction of a new variable gap penalty function based on the predicted locations of the IndelFRs and the computed average log–loss values into the proposed algorithm substantially improves the protein alignment accuracy. This is illustrated by evaluating the performance of the algorithm in aligning sequences belonging to the protein folds for which the IndelFR predictors already exist and by using the reference alignments of the four popular benchmarks, BAliBASE 3.0, OXBENCH, PREFAB 4.0, and SABRE (SABmark 1.65). Conclusions We have proposed a novel and efficient algorithm, the MSAIndelFR algorithm, for multiple protein sequence alignment incorporating a new variable gap penalty function. It is shown that the performance of the proposed algorithm is superior to that of the most–widely used alignment algorithms, Clustal W2, Clustal Omega, Kalign2, MSAProbs, MAFFT, MUSCLE, ProbCons and Probalign, in terms of both the sum–of–pairs and total column metrics

Personalisation in MOOCs: a critical literature review

The advent and rise of Massive Open Online Courses (MOOCs) have brought many issues to the area of educational technology. Researchers in the field have been addressing these issues such as pedagogical quality of MOOCs, high attrition rates, and sustainability of MOOCs. However, MOOCs personalisation has not been subject of the wide discussions around MOOCs. This paper presents a critical literature survey and analysis of the available literature on personalisation in MOOCs to identify the needs, the current states and efforts to personalise learning in MOOCs. The findings illustrate that there is a growing attention to personalisation to improve learners’ individual learning experiences in MOOCs. In order to implement personalised services, personalised learning path, personalised assessment and feedback, personalised forum thread and recommendation service for related learning materials or learning tasks are commonly applied