Journal of Seismology and Earthquake Engineering
Volume:12 Issue: 3, Autumn 2010

This note was prompted by the earthquake of 12 January 2010 in Haiti, which is notthe only earthquake in recent years in which hundreds of thousands of peoplehave been killed, in contrast to the near-zero death toll caused by earthquakes ofthe same magnitude elsewhere (viz.New Zealand 03.09.10). The Haiti earthquakeraises several points that must be addressed in any realistic attempt to mitigatethe loss of life arising from earthquakes, in particular the question of whether thisenormous difference in human losses is almost entirely due to houses having beenpoorly constructed due to corrupt practices that allowed poorly sited andconstructed houses to be built in seismic regions.

This paper presents the differences of cyclic behavior in Special Moment ResistingFrames (SMRF) with unequal beam depths which can be affected by connectiondetailing arrangements. The studied connection detailing arrangements consist ofcontinuity plate arrangements such as straight or inclined continuity plates,coverplate and flange plate connection and haunch connection systems at theshallow beam side which can create some alternatives to connect shallow beamsand deep beams with columns. In spite of probable occurrences of this special casein current engineering practice, codes do not take these especial cases into consideration.Six full scale beams to column sub-assemblages were tested to investigatethe cyclic behavior for this special case i.e. unequal beamdepths. Experiments showthat the mentioned connection detailing arrangements could achieve performancediscriminations ranged between story drift ratios of at least 4% to 6% radiansbefore experiencing 20% strength degradation. Using a specific combination offlange plate connection with the haunch connection system, the crack propagationat the deep beam bottomflange which is observed in most of the connection detailingarrangements for this special case is eliminated.

This paper presents the results of an experimental study conducted to assess theseismic response of the commonly used multicolumn bridge bents constructed inIran. Observing the real performance of the bent, capturing undesirable failuremodes, and verifying current code requirements are the main goals of this study. A30% scaled specimen was designed, constructed and tested under simulated earthquakeloads. The results indicate that the joint failure and slippage of longitudinalcolumn reinforcement within the joints are the predominant failure modes underlateral cyclic loading. Such failure modes adversely affect the energy-absorbingcapacity by a significantly pinched hysteresis response. Slippage of the columnslongitudinal bar is the main contributing factor for the pinched hysteresis response.Based on the test results, AASHTOrequirements for development length of the columnslongitudinal bars inside the cap-beam is unnecessarily long, and it can be reducedconsidering the confinement effects of transverse reinforcement. Test results alsoindicate that the displacement capacity of bridge bents calculated by the AASHTOapproximate equation may be unconservative.

One of the major causes of train accidents is derailment due to axial or lateralbuckling of the track. This problemis more prominent in continuously welded rails(CWR), which are now very common because of their advantages of reduced noiseand damage and more comfortable rides. As for the effect of earthquakes on trackbuckling, the axial force they induce seems to be much less than that of temperaturechange as well as those caused by tractive action and braking of locomotives. Thisdoes not mean that earthquakes cannot have a detrimental effect on railroad tracks.Their main cause of damage is the large reduction they may produce in the lateralresistance of ballast due to shaking of the ballast bed. This paper deals with theproblem of axial and lateral buckling of CWR and the effects of earthquakes andtemperature change on the stability of the track. A three-dimensional macro-elementis used to model the track. Aprogram, developed in Mathcad environment, isused to conduct a series of parametric studies. The results show that the simplesinusoidal formoften used for determining buckling loads of tracks is only valid fortotally homogeneous tracks, a rather rare situation. It was ascertained that thebuckled shapes observed in practice are due to local inhomogeneities of the track.

In this paper, a cyclic constitutive model is developed for high-strength concrete(HSC) confined by ultra-high-strength and normal-strength transverse reinforcements(UHSTR and NSTR), with the intention of providing efficient modeling for themember and structural behavior of HSC in seismic regions. The model for HSCsubjected to monotonic and cyclic loading, comprises four components; an envelopecurve (for monotonic, cyclic and earthquake loadings), an unloading curve, areloading curve, and a tensile unloading curve. It explicitly accounts for the effectsof concrete compressive strength, the volumetric ratio of transverse reinforcement,yield strength of ties, tie spacing, and tie pattern. The proposed envelope curvemodels for confined HSC cover four options; namely, (1) rectangular (square) crosssection with NSTR, (2) circular cross section with NSTR, (3) rectangular (square)cross section with UHSTR, and (4) circular cross section with UHSTR. Comparisonswith test results showed that the proposed model provides a good fitting to a widerange of experimental results. The configuration of transverse reinforcement had aparticularly large effect.