Considering Soil-Nonlinearity Effect on Seismic Performance Evaluation of Structures based on Pushover Analysis

According to the most of current seismic codes, nonlinear soil behavior is commonly ignored in seismic evaluation procedure of the structures. To contribute on this matter, a pushover analysis method incorporating the probabilistic seismic hazard analysis (PSHA) is proposed to evaluate the effect of nonlinear soil response on seismic performance of a structure. The PSHA outcomes considering soil nonlinearity effect is involved in the analysis procedures by modifying the site-specific response spectrum. Results showed that incorporation of nonlinear soil behavior leads to an increase in displacement demand of structures which should accurately be considered in seismic design/assessment procedure. Results of implemented procedure are confirmed with the estimated displacement demand including soil-structure interaction (SSI).     

Equivalent Damping Ratio Equations in Support of Displacement-Based Seismic Design for Pile-Supported Wharves

This study primarily proposes new equivalent damping ratio equations based on Jacobsen’s approach for displacement-based seismic design of pile-supported wharves to account for wharf configurations and soil-pile interaction. It is found that Pivot hysteresis model and Masing rule can accurately capture nonlinear behavior of concrete and steel wharves, respectively. To verify applicability of proposed equations, analyses were conducted to three typical wharves to make a comparison of maximum displacements obtained from nonlinear time-history analyses and substitute structure method with various damping equations. The verification reveals proposed equations are better than those in practice for their higher precision in determining displacements.     

Effects of Base and Lift Joints on the Dynamic Response of Concrete Gravity Dams to Pulse-Like Excitations

Near-fault earthquakes with forward-directivity effects produce pulse-like excitations. This article studies the dynamic response of monolithic and cracked sections of gravity dam under symmetric and anti-symmetric pulse-like excitations. The pulses are generated by the modified Gabor Wavelet transform. Two main characteristics of the pulses are pulse period and amplitude. The prescribed cracks are located along the base and two distinct lift joints through the dam body. The dam is modeled along with its reservoir using finite element method. The effects of base and lift joints, pulses shape, period, and amplitude, and reservoir height on the dam dynamic response are studied.     

Rocking of Non-symmetric Rigid Blocks in Buildings Considering Effects Associated with Dynamic Soil-Structure Interaction

A dynamic model for the estimation of the rocking and/or overturning response of a free-standing non-symmetric rigid block considering rotational and horizontal excitation is proposed. The block is situated at different levels of a building with flexible base subjected to earthquakes. Base flexibility introduces the rotational component of the excitation due to dynamic soil-structure interaction (DSSI). The model is used to assess the influence of the dynamic soil-structure interaction on the behavior of the block. An illustrative example of the proposed model for non-symmetric rigid blocks in 5-, 10-, and 15-story buildings located in soft soils considering earthquakes from different seismic sources is presented. Results show that it is important to consider kinematic effects as well as inertial effects of DSSI in the dynamic response of contents. The influence of base flexibility depends on the change of spectral intensities associated to the increase of the building structural period and is larger for higher building levels.     

Soil-Structure Interaction on a Shallow Rigid Circular Foundation: SH Wave Source from Near-Field Excitations

A closed-form wave function analytic solution is presented in this article regarding the two-dimensional scattering and diffraction of a flexible wall sitting on a rigid shallow circular foundation embedded in an elastic half-space that is activated by a nearby anti-plane line source such as a blast caused by underground construction or mineral exploration or a near-field fault rupture, using similar methodology as the other paper in a series [Lee and Luo, 2013]. These wave propagation influences, although often treated as a transient process, may be simulated as linear combinations of steady-simple harmonic responses as studied in this article. Ground surface displacements spectra for wide-band of incident wave frequencies are calculated. Based on the spectra obtained, the dependence of near-field ground displacements are shown with respect to the rise-to-span ratio of foundation profile, frequency of incident waves, distance of source from the foundation, and mass ratios of various media (foundation-structure-soil). The screening effect of rigid foundation upon ground motions behind grazing incident waves is also presented.     

Arch Dam-Fluid Interaction Considering Reservoir Topology

The magnitudes of the hydrodynamic pressures at the dam-fluid interface depend on the amount of energy transmitted to the fluid by the vibration of the reservoir boundaries. Although the reservoir topology can have a considerable impact on the amount of generated energy, it has still not been adequately addressed. This article treats an arch dam-fluid interaction considering a compound wave field of compressive and dilatational waves in a reservoir with a complex topology. A truncation surface was located at a distance beyond which the simulated wave field has only negligible effects.     

古籍墨迹的老化检测及其模拟实验研究

随着纸质文物保护工作的推进,针对古籍纸张载体的保护研究已逐步深入,但对于古籍纸张上的墨、颜料等其他写印材料的保护及写印材料之间的相互作用则亟待研究。其中,古籍墨迹的老化研究有助于揭示墨与纸相互作用的本质,对于古籍文物的保护具有非常重要的意义。以复旦大学图书馆藏古籍《三十二兰亭室诗存》墨迹的老化现象为出发点,通过显微镜观察、表面pH值测定、显微拉曼(micro-Raman)和傅里叶变换红外(FT-IR)光谱法等多种无损、微损的检测手段多尺度分析了墨迹泛黄的现象,结果显示墨迹处及周边黄晕纤维与空白部分纤维相比,光泽缺失且略显糟朽,酸性更强,表面氧化基团增多,说明墨可能对纸张的老化降解产生了影响。通过设计纸墨浸润模拟老化实验对此进行验证,结果显示与偏中性墨汁相比,尽管墨汁中胶料对纤维有一定保护作用,但偏酸性墨汁对纸张老化的促进作用使pH值、抗张性能及耐折性能的下降趋势更明显,聚合度保留率也较低。墨字模拟老化实验佐证了前述结论,使用酸性更强的墨汁书写的字迹,周围纸张酸性更强,色差也更显著。以上结果表明,墨汁的酸碱性质对纸张的老化降解进程有很重要的影响。这不仅揭示出古籍存藏过程中受墨影响的纸张老化机制以及模拟实验合理设计对于系统探究老化机制及纸墨相互作用的重要性,也对古籍保护工作范畴的扩大和策略的制定具有指导意义,并为修复用墨的研制提供了思路。