Bin Wang

Experimental Study on Damage Behavior of Reinforced Concrete Shear Walls Subjected to Cyclic Loads

Previous experimental research on shear walls has mainly focused on load carrying capacity, deformation, or hysteretic characteristics, with relatively little attention paid to individual damage states and their corresponding responses during the entire loading process until failure. The damage behavior of seven reinforced concrete shear wall specimens subjected to cyclic loading is presented in this study. The effects of the axial load ratio, transverse reinforcement ratio of confining boundary elements, and cross-section shape on damage characteristics, ductility, shear deformation, and crack width of the specimens were analyzed comprehensively.

Seismic behavior of self-centering reinforced concrete wall enabled by superelastic shape memory alloy bars

Reinforced concrete (RC) wall is a common type of structural component used in high-rise buildings to resist lateral loads induced by earthquakes. RC walls are typically designed and detailed to dissipate energy through significant inelastic responses to meet expected seismic performance under moderate-to-strong earthquakes. However, costly repair or even demolition caused by excessive residual deformation is usually inevitable. Given this deficiency, this study investigates the feasibility of utilizing superelastic shape memory alloy (SMA) bars to achieve self-centering (SC) RC walls. Under this condition, the residual deformation of SC–RC walls is reduced by superelastic SMA with large recoverable strain and remarkable fatigue properties. The mechanical properties of superelastic nickel–titanium bars and SC–RC wall design are described. A numerical SC–RC wall model is developed and validated by comparing the test results. Parametric studies of SC–RC wall systems are then conducted to investigate the effects of axial compressive load ratio, bottom slit length, and lower plateau stress factor of SMA. Results show that the proposed SC–RC walls have excellent SC ability and moderate energy dissipation capacity. The damage regions and levels of the SC–RC wall systems are also discussed.

SHAKING TABLE TESTS ON A COMPLEX HIGH-RISE STRUCTURE WITH TWO TOWERS AND LAPPING TRANSFER COLUMNS

In recent decades, structural engineering tends to progress toward more novel high-rise structures under the requirement of realistic functions and architectural aesthetics. The complex high-rise building structure in this study has two towers with lapping transfer columns. The lapping transfer columns, considering aesthetic requirement in elevation, lead to a complex system of vertical force transfer. The large irregularity in elevation, according to Chinese code, needs a detailed study. A 1/15-scaled model of the structure was tested on the shaking table to evaluate its seismic performance. During the tests, the model was subjected to earthquake inputs representing frequent, basic, rare, and extremely rare earthquakes. The results of shaking table test in terms of the global and local responses as well as the dynamic properties are presented. The tests demonstrate that the designed structural system satisfies the pre-defined performance objectives and the lapping transfer columns are capable of coordinating the bi-level stories to resist lateral forces even under extremely strong earthquakes. To better control seismic damages of the building, some suggestions for improving the design of this structure are also put forward at last.

Seismic Damage Analyses of Staircases in RC Frame Structures

Staircases in Reinforced Concrete (RC) frame structures suffered severe damages in recent earthquakes although they are regarded as critically important passages during emergencies. Staircases act as the first line of defense in earthquakes, and therefore they first yield and fail. Then they lose the action of safe passages so that the anticipated seismic performance objectives cannot be satisfied. To make sure that staircases work as safe passages in strong earthquakes, the current Chinese code for seismic design of buildings claims special requirements on the design of staircases. At first, the influence of staircases on the structural behavior of a typical RC frame structure is studied by the comparison of internal force in the structural members considering and neglecting the effect of staircases under frequent earthquakes. Besides, the effect of staircases on the yielding and failing mechanism of the frame structure is investigated through static elasto-plastic analyses. From this study the reason of the damages suffered by cast-in-site staircases in RC frame structures under earthquakes can be understood.

Seismic Retrofitting of Non-Seismically Designed RC Beam-Column Joints using Buckling-Restrained Haunches: Design and Analysis

ABSTRACT Many existing reinforced concrete (RC) structures around the world have been designed to sustain gravity and wind loads only. Past earthquake reconnaissance showed that strong earthquakes can lead to substantial damage to non-seismically designed RC buildings, particularly to their beam-column joints. This paper presents a novel retrofit method using buckling-restrained haunches (BRHs) to improve the seismic performance of such joints. A numerical model for RC joints is introduced and validated. Subsequently, a new seismic retrofit strategy using BRHs is proposed, aimed at relocating plastic hinges and increasing energy dissipation. The results indicate the retrofit method can effectively meet the performance objectives.

Experimental Behavior of Concrete-Filled Square Steel Tube of Mid and Long Columns Subjected to Eccentric Compression

This paper presents an experimental investigation of the mechanic behavior of 9 concrete-filled square steel tube columns (CFSST) subjected to eccentric loading. The primary parameters of the specimens are eccentricity ratios, slenderness ratios and concrete strength. The results showed that the eccentricity ratios and slenderness ratios are the primary factors to influence the load-bearing capacity of CFSST columns, with the increase of eccentricity ratios and slenderness ratios, the limit load-bearing capacity reduced gradually. The influence of concrete strength to load-bearing capacity decreased gradually with the increase of eccentricity ratios and slenderness ratios.

Experimental Investigation on Damage Behavior of RC Shear Walls

Low-cycle cyclic loading tests were carried out on seven reinforced concrete shear wall specimens with different design parameters to investigate the damage behavior under earthquakes. The damage features including the damage process, deformations, the maximum crack width and the corresponding residue crack width at different damage state were recorded. According to the experimental data, the influence of axial compressive load ratio, stirrup ratio of the boundary column and cross-section shape on the ductility, carrying capacity, deformation characteristic and seismic damage is analyzed. With the axial compressive load ratio increasing, the carrying capacity and shear effect increase while the ductility and residual crack ratio decrease. With the deformation and damage increasing, the shear effect increases. The shear walls with I-shaped cross-section display more shear effect than those with the cross-section of “—” and “T” shape.

Seismic Performance Evaluation of a High-Rise Building with Lapping Transfer Columns by Shaking Table Tests

The reinforced concrete (RC) frame-tube structure considered in the study has two towers with lapping transfer columns. The lapping transfer columns, considering aesthetic requirement in elevation, lead to a complex vertical force transfer system. The large irregularity in elevation, according to Chinese code, necessitates a detailed study. A 1/15-scaled model of the high-rise building was tested on a shaking table to evaluate its seismic performance. The model was subjected to earthquake inputs representing frequent, basic, rare, and extremly rare earthquakes. The results of shaking table test in terms of the global and local responses as well as the dynamic properties are presented. The tests demonstrate that the designed structural system satisfies the pre-defined performance objectives and the lapping transfer columns have good seismic peformance. To better control seismic damages of the building, some suggestions for improving the design of this structure are also put forward at last.