Yu-Chen Ou

National Taiwan University | NTU · Department of Civil Engineering

Summarized herein are the motivation, special design details developed, and key findings from an extensive experimental study conducted at National Taiwan University to investigate the effectiveness of using unstressed steel strands as longitudinal reinforcement in reinforced concrete elements. As a part of the study, multiple flexurally dominant c...

Multi-spiral transverse reinforcement has been shown to provide superior seismic performance than conventional rectilinear tie reinforcement. This research intends to investigate the flexural behavior of the five-spiral transverse reinforcement configuration for square concrete columns. Large-scale flexure-critical five-spiral columns and counterpa...

Six full-scale beams using either only steel bars, mixed steel bars and seven-wire steel strands, or only seven-wire steel strands as longitudinal reinforcement were tested under four-point bending. The bars were ASTM A706 Grade 60 (420 MPa) steel deformed bars, and the strands were ASTM 416 Grade 270 (1860 MPa) seven-wire steel strands. Test resul...

The use of unstressed Grade 1860 MPa seven-wire steel strands as longitudinal reinforcement has the potential to reduce steel congestion in reinforced concrete members. However, no studies which use unstressed steel strands as the longitudinal reinforcement in concrete columns have been reported in the literature. Thus, in this study, five large-sc...

Five-spiral transverse reinforcement for square reinforced concrete columns has been proven to possess a confinement capability superior to that of conventional rectilinear tie reinforcement. The objective of this research is to investigate the shear capacity of five-spiral reinforcement. Large-scale shear-critical five-spiral columns and comparabl...

This paper proposes a simplified finite-element analysis (FEA) method to analyze the axial compression behavior of rectangular concrete columns confined by interlocking multispiral reinforcements. The proposed method uses an elastic finite-element analysis to approximate the distribution and ultimate state of confining stress in each core concrete...

As fossil fuels and people’s environmental awareness increases, renewable energy is becoming one of the world’s most anticipated areas of development. Taiwan has an outstandingly favorable environment for wind farms, and the Taiwanese government actively promotes wind-power generation (such as its “Thousand Wind Turbines Project”). Many wind turbin...

Five full-scale reinforced concrete wall specimens with openings typical of the first story backside exterior walls of row houses in Taiwan were tested using lateral cyclic loading to study their seismic behavior. The effects of location and size of the window opening were studied. Test results showed that the wall with the window opening on the si...

Capacity‐based inelastic displacement spectra that comprise an inelastic displacement ratio (CR) spectrum and the corresponding damage index (DI) spectrum are proposed in this study to aid seismic design and evaluation of reinforced concrete (RC) bridges. Nonlinear time history analyses of single‐degree‐of‐freedom (SDOF) systems are conducted using...

Although a detailed finite element (FE) model provides more precise results, a lumped-mass stick (LMS) model is preferred because of its simplicity and rapid computational time. However, the reliability of LMS models has been questioned especially for structures dominated by higher modes and seismic inputs. Normally, the natural frequencies and dyn...

The renewable energy industry is thriving in many countries against a global backdrop of growing environmental awareness. In particular, in Taiwan, wind is emerging as a potential source. The Taiwanese government has implemented the “Thousand Wind Turbines” project as a collaboration with the private sector to construct a wind power infrastructure....

The paper investigated the effect of alkaline concrete environment on thermally damaged glass fiber reinforced polymer (GFRP) reinforcing bars through an accelerated aging test in alkaline solution. In the experimental test, the GRFP bar specimens were exposed to high temperatures and then immersed in alkaline solution with a pH of 12.6 presenting...

To promote prefabricated segmental bridges in regions of moderate or high seismicity, stainless energy dissipation bars (ED bars) are used continuously across the column segment critical joints to increase the hysteretic energy dissipation. However, the bond response and the design development length of the anchored ED bars were not well understood...

Shear keys as sacrificial members are widely used in cap beams and abutments of highway bridges, to limit the transverse displacement of superstructures and control damage to substructures. An experimental program to study the seismic behavior of reinforced concrete (RC) sacrificial exterior shear keys was presented. The influence of reinforcement...

The anchorage performance of headed deformed bars anchored in inter-story exterior beam-column joints under cyclic load was examined based on a test database with 118 test data. A proposed performance index based on the ACI 318 development length equation was used to evaluate the anchorage performance of the headed deformed bars of the specimens in...

A new smooth hysteretic model is proposed for ductile, flexural-dominated reinforced concrete bridge columns. Four columns designed per modern seismic codes were tested using monotonically increasing and variable-amplitude cyclic loading protocols and ground motion loading to develop the model. Based on the test results, hysteretic rules for damage...

The seismic performance of unbonded post-tensioned (PT) precast segmental bridge columns (PSBCs) with circular section was investigated. Two precast segmental columns with/without energy dissipation (ED) bars were tested under quasi-static cyclic loading. Their damaged pattern and hysteretic curves were compared. Three single degree of freedom hyst...

The primary goal is to accurately predict long-term integral abutment bridge (IAB) responses under thermal loads by applying available numerical modeling techniques developed on the basis of a long-term monitoring of in-service IABs. Considered methodologies are: (1) free expansion; (2) empirical approximate; (3) two-dimensional (2D) static analysi...

This study developed discrete computational shear strength (DCSS) models for two-circular-hoop, two-spiral, seven-circular-hoop, and seven-spiral transverse reinforcement for reinforced concrete columns. The DCSS models show that as a shear crack moves along the column, the reinforcement shear strength varies periodically. The critical shear crack,...

Four 1/4-scale precast segmental bridge columns (PSBC) with different reinforcement types and arrangements and one monolithic reference column (MRC) were designed and tested under cyclic quasi-static loading. Both UPC (PSBC with unbonded tendons only) and UPCE (PSBC with unbonded tendons and bonded mild steel bars) use unbonded posttensioned (PT) s...

Based on the actual, discrete locations of interception points between the critical shear crack and transverse reinforcement, this study developed the discrete computational shear strength (DCSS) models for five-, six-, and eleven-circular-hoop and spiral reinforcement. Moreover, conventional simplified calculation method was revised for use for fi...

Double-curvature cyclic tests of large-scale columns were conducted to investigate the seismic performance of precast high-strength reinforced concrete columns. High-strength concrete and high-strength longitudinal and transverse reinforcement were used. The use of grouted coupler splices for the high-strength longitudinal reinforcement in the plas...

A pushover seismic analysis method based on the extended N2 method is proposed. Compared to the extended N2 method, the proposed method has four modifications that account for nonlinear higher mode effects. In the first modification, a lateral load based on the equivalent static forces from the dominant dynamic modes of a building combined using th...

This research investigated the panel zone shear behavior of a proposed through-flange connection for steel beams to circular concrete-filled steel tubular (CFT) columns. Four exterior beam-column specimens were designed and tested using cyclic loading applied to the beam end. Three design variables were examined: concrete infill in the column tube,...

Finite element analysis based on solid elements can be used in the seismic analysis of integrated nuclear containment systems, which include structural components (nuclear containment building) and non-structural components (reactor vessel, steam generator, etc.). However, this solid element based FE modeling requires long computational times or hi...

This research proposes innovative seven-spiral and eleven-spiral transverse reinforcement to replace two-spiral and six-spiral reinforcement, respectively, to decrease the spiral size to address the issue of spiral fabrication in large columns. Moreover, this research proposes using large reinforcing bars or H-shaped steel as longitudinal reinforce...

The proposed method, called the Taiwan Earthquake Assessment for Structures by Pushover Analysis (TEASPA), is a modified capacity spectrum method developed in the NCREE handbook after the 1999 Chi-Chi earthquake. In this study, the evaluation of TEASPA is carried out using results from an experimental campaign comprised of two pushover tests inlow-...

To observe the effect of axial compression on the shear behavior of high-strength reinforced concrete columns, eight shear-critical high-strength columns were tested under cyclic shear with an axial compressive stress of 0.3f c ʹ to 0.4f c ʹ and compared to eight columns tested in a previous study with an axial compressive stress of 0.1f c ʹ to 0.2...

Eight shear-critical, large-scale, high-strength reinforced concrete columns under low axial load were tested. The specified concrete compressive strengths were 70 and 100 MPa (10,000 and 14,500 psi). The specified yield strengths were 685 and 785 MPa (100,000 and 114,000 psi) for the longitudinal and transverse reinforcement, respectively. Test re...

An innovative seven-spiral transverse reinforcement is proposed for oblong reinforced concrete bridge columns. Compared to conventional single-spiral or two-spiral transverse reinforcement, the proposed scheme reduces the size of the spirals and hence improves the constructibility of spirals for large bridge columns. Four seven-spiral columns were...

This study examined the seismic performance of reinforced concrete beams with corrosion only induced in the transverse steel reinforcement by using cyclic loading. The beams were designed with closely spaced steel hoops as transverse reinforcement conforming to the seismic design provisions of the ACI 318 code. Seven beams were constructed. One bea...

Existing plastic hinge length formulations for reinforced concrete members do not consider the effect of steel reinforcement corrosion. This study investigated the effect of reinforcement corrosion on the plastic hinge length L p of reinforced concrete beams. A nonlinear finite element analysis method was developed, and verified by experimental res...

This study examined seismic behavior under long-duration ground motion in flexural-dominated reinforced concrete bridge columns designed per modern seismic design codes. Two column specimens with identical design parameters were tested. The first column (named CLC) was tested using a long-duration loading protocol developed to represent the number...

Bridges are a vital and significant component of Taiwan's transportation infrastructure. Therefore, regular and comprehensive inspections of existing bridges are necessary to prevent damage and traffic disruption and reduce earthquake-related damage and casualties. However, due to the large number of bridges in Taiwan, the time and budget required...

This study investigates the behavior of transversely reinforced oblong and rectangular bridge columns under combined axial and flexural loading, including eccentric compression and lateral cyclic loading under constant axial load. The transverse reinforcement schemes include conventional tie and multi-spiral reinforcement. The multi-spiral reinforc...

This work proposes a new precast segmental concrete bridge column. The lower region of the column is built using cast-in-place (CIP) construction. The height of the CIP region and level of post-tensioning force in the precast region are selected such that the ultimate condition of the column under seismic loading is governed by a conventional plast...

Synopsis: The advancement of material technology has led to higher grades of both concrete and steel strengths. High-strength concrete and steel can decrease the size of structural members and increase the available floor area. In addition, it can decrease the consumption of aggregate and steel, promoting environmental sustainability. This research...

This work presents a new seismic evaluation methodology for corroded reinforced concrete bridges on the basis of nonlinear static pushover analysis. Corrosion of steel reinforcement by chloride attack is considered. At the material level, the effects of corrosion are considered by modeling the degradation of the mechanical properties of steel reinf...

Precast construction is an increasing trend of concrete bridge technology to fulfill the demand of innovative technique that yields accelerated, durable and safe bridge construction. Although precast bridge superstructures are widely used in bridge construction projects from the U.S. to Asia, precast substructures are seldom used. The lack of in-de...

Taiwan is located on the Pacific Ring of Fire and thus experiences many detectable earthquakes annually. The damage resulting from these earthquakes affects the government and local citizens financially and endangers lives. As the political and economic capital of Taiwan, Taipei has a high population density. Assessing the seismic effects in Taipei...

Bridges are a vital and significant component of Taiwan's transportation infrastructure. Therefore, regular and comprehensive inspections of existing bridges are necessary to prevent damage and traffic disruption and reduce earthquake-related damage and casualties. However, due to the large number of bridges in Taiwan, the time and budget required...

This paper presents a parametric study of the plastic hinge length of circular reinforced concrete columns using a three-dimensional finite element analysis method, and using the Taguchi robust design method to reduce computational cost. Parameters examined include the longitudinal reinforcing ratio, the shear span-to-depth ratio, the axial force r...

Nine large‐scale beam specimens were constructed. Of which, one was used as the control, whereas the other eight ones were divided into four sets. Each set had two specimens and was subjected to accelerated corrosion using an imposed current for the same time interval. Following the corrosion, a specimen in each set was tested using cyclic loading...

Compression tests on cylinders were performed to characterize the compressive stress-strain behavior of steel fiber-reinforced concrete (SFRC) with a high reinforcing index. The reinforcing index, defined as the product of the volume fraction and the aspect ratio of the fibers, of steel fibers examined was as high as 1.7. Hooked-end fibers of vario...

The cyclic behavior of precast segmental concrete bridge columns with high performance (HP) steel reinforcing bars and that with conventional steel reinforcing bars as energy dissipation (ED) bars were investigated. The HP steel reinforcing bars are characterized by higher strength, greater ductility, and superior corrosion resistance compared with...

Use of stainless reinforcing steel (SRS) in reinforced concrete (RC) structures is a promising solution to corrosion issues. However, for SRS to be used in seismic applications, several mechanical properties need to be investigated. These include specified and actual yield strengths, tensile strengths, uniform elongations and low-cycle fatigue beha...

A new roller seismic isolation bearing is developed for use in highway bridges. This new bearing uses rolling of cylindrical rollers on V-shaped sloping surfaces to achieve seismic isolation. The bearing is characterized by a constant spectral acceleration under horizontal ground motions and by a self-centering capability, which are two desirable p...

The seismic behavior of the proposed precast segmental unbonded posttensioned concrete bridge columns for use in regions of high seismicity was investigated experimentally. Posttensioning tendons were placed in the hollow core of the columns and left unbonded with the surrounding concrete to decrease prestress loss during earthquakes. Bonded mild s...

The cyclic behavior of precast segmental concrete bridge columns with high performance (HP) steel rebar and that with conventional steel rebar as energy dissipation (ED) bars were investigated. The HP steel rebar is characterized by higher strength, greater ductility and superior corrosion resistance compared to the conventional steel rebar. Three...

A roller seismic isolation bearing is proposed for use in highway bridges. The bearing utilizes a rolling mechanism to achieve seismic isolation and has a zero post-elastic stiffness under horizontal ground motions, a self-centering capability, and unique friction devices for supplemental energy dissipation. The objectives of this research are to i...

Past experimental studies have shown that existing precast segmental concrete bridge columns possess unsatisfactory hysteretic energy dissipation capacity, which is an undesirable feature for applications in seismic regions. In this research, we propose new methods of precast segment construction for tall concrete bridge columns to enhance the colu...

The seismic performance of segmental precast unbonded posttensioned bridge columns with hollow cross sections is investigated in this paper. Bonded longitudinal mild steel reinforcement crossing the column segment joints is provided to enhance the hysteretic energy dissipation of the columns, also referred to as energy dissipation (ED) bars in this...

Segmental bridge column construction has been proven to be an economic and durable option to accelerate the bridge construction in non-seismic regions in the United States. Examples include Seven Mile Bridge in Florida and Chesapeake and Delaware (C&D) Canal Bridge in Delaware. The lack of knowledge of the seismic behavior of a bridge with segmenta...

The cyclic performance of an unbonded precast concrete segmental bridge column system is examined in this paper. This system uses unbonded posttensioning to enhance the self-centering capability and mild steel reinforcement extended across the segment joints to enhance the energy dissipation capability. A simplified analytical method for the system...

The cyclic performance of an unbonded precast concrete segmental bridge column system is examined in this paper. This system uses unbonded posttensioning to enhance the self-centering capability and mild steel reinforcement extended across the segment joints to enhance the energy dissipation capability. A simplified analytical method for the system...

The use of stainless steel reinforcing bars in reinforced concrete structures is one of the promising solutions to corrosion issues. For stainless steel reinforcing bars to be used in seismic applications, several mechanical properties need to be investigated such as nominal and actual yield strengths, tensile strengths, elongations and low cycle f...